CVE-2022-2031 s4:kdc: Don't use strncmp to compare principal components

[Samba.git] / source4 / kdc / db-glue.c

/*
   Unix SMB/CIFS implementation.

   Database Glue between Samba and the KDC

   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005-2009
   Copyright (C) Simo Sorce <idra@samba.org> 2010

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.


   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "libcli/security/security.h"
#include "librpc/gen_ndr/ndr_security.h"
#include "auth/auth.h"
#include "auth/auth_sam.h"
#include "dsdb/samdb/samdb.h"
#include "dsdb/common/util.h"
#include "librpc/gen_ndr/ndr_drsblobs.h"
#include "param/param.h"
#include "param/secrets.h"
#include "../lib/crypto/md4.h"
#include "system/kerberos.h"
#include "auth/kerberos/kerberos.h"
#include "kdc/sdb.h"
#include "kdc/samba_kdc.h"
#include "kdc/db-glue.h"
#include "kdc/pac-glue.h"
#include "librpc/gen_ndr/ndr_irpc_c.h"
#include "lib/messaging/irpc.h"

#undef strcasecmp
#undef strncasecmp

#define SAMBA_KVNO_GET_KRBTGT(kvno) \
        ((uint16_t)(((uint32_t)kvno) >> 16))

#define SAMBA_KVNO_GET_VALUE(kvno) \
        ((uint16_t)(((uint32_t)kvno) & 0xFFFF))

#define SAMBA_KVNO_AND_KRBTGT(kvno, krbtgt) \
        ((krb5_kvno)((((uint32_t)kvno) & 0xFFFF) | \
         ((((uint32_t)krbtgt) << 16) & 0xFFFF0000)))

enum trust_direction {
        UNKNOWN = 0,
        INBOUND = LSA_TRUST_DIRECTION_INBOUND,
        OUTBOUND = LSA_TRUST_DIRECTION_OUTBOUND
};

static const char *trust_attrs[] = {
        "securityIdentifier",
        "flatName",
        "trustPartner",
        "trustAttributes",
        "trustDirection",
        "trustType",
        "msDS-TrustForestTrustInfo",
        "trustAuthIncoming",
        "trustAuthOutgoing",
        "whenCreated",
        "msDS-SupportedEncryptionTypes",
        NULL
};

/*
  send a message to the drepl server telling it to initiate a
  REPL_SECRET getncchanges extended op to fetch the users secrets
 */
static void auth_sam_trigger_repl_secret(TALLOC_CTX *mem_ctx,
                                  struct imessaging_context *msg_ctx,
                                  struct tevent_context *event_ctx,
                                  struct ldb_dn *user_dn)
{
        struct dcerpc_binding_handle *irpc_handle;
        struct drepl_trigger_repl_secret r;
        struct tevent_req *req;
        TALLOC_CTX *tmp_ctx;

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                return;
        }

        irpc_handle = irpc_binding_handle_by_name(tmp_ctx, msg_ctx,
                                                  "dreplsrv",
                                                  &ndr_table_irpc);
        if (irpc_handle == NULL) {
                DEBUG(1,(__location__ ": Unable to get binding handle for dreplsrv\n"));
                TALLOC_FREE(tmp_ctx);
                return;
        }

        r.in.user_dn = ldb_dn_get_linearized(user_dn);

        /*
         * This seem to rely on the current IRPC implementation,
         * which delivers the message in the _send function.
         *
         * TODO: we need a ONE_WAY IRPC handle and register
         * a callback and wait for it to be triggered!
         */
        req = dcerpc_drepl_trigger_repl_secret_r_send(tmp_ctx,
                                                      event_ctx,
                                                      irpc_handle,
                                                      &r);

        /* we aren't interested in a reply */
        talloc_free(req);
        TALLOC_FREE(tmp_ctx);
}

static time_t ldb_msg_find_krb5time_ldap_time(struct ldb_message *msg, const char *attr, time_t default_val)
{
    const char *tmp;
    const char *gentime;
    struct tm tm;

    gentime = ldb_msg_find_attr_as_string(msg, attr, NULL);
    if (!gentime)
        return default_val;

    tmp = strptime(gentime, "%Y%m%d%H%M%SZ", &tm);
    if (tmp == NULL) {
            return default_val;
    }

    return timegm(&tm);
}

static struct SDBFlags uf2SDBFlags(krb5_context context, uint32_t userAccountControl, enum samba_kdc_ent_type ent_type)
{
        struct SDBFlags flags = int2SDBFlags(0);

        /* we don't allow kadmin deletes */
        flags.immutable = 1;

        /* mark the principal as invalid to start with */
        flags.invalid = 1;

        flags.renewable = 1;

        /* All accounts are servers, but this may be disabled again in the caller */
        flags.server = 1;

        /* Account types - clear the invalid bit if it turns out to be valid */
        if (userAccountControl & UF_NORMAL_ACCOUNT) {
                if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT || ent_type == SAMBA_KDC_ENT_TYPE_ANY) {
                        flags.client = 1;
                }
                flags.invalid = 0;
        }

        if (userAccountControl & UF_INTERDOMAIN_TRUST_ACCOUNT) {
                if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT || ent_type == SAMBA_KDC_ENT_TYPE_ANY) {
                        flags.client = 1;
                }
                flags.invalid = 0;
        }
        if (userAccountControl & UF_WORKSTATION_TRUST_ACCOUNT) {
                if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT || ent_type == SAMBA_KDC_ENT_TYPE_ANY) {
                        flags.client = 1;
                }
                flags.invalid = 0;
        }
        if (userAccountControl & UF_SERVER_TRUST_ACCOUNT) {
                if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT || ent_type == SAMBA_KDC_ENT_TYPE_ANY) {
                        flags.client = 1;
                }
                flags.invalid = 0;
        }

        /* Not permitted to act as a client if disabled */
        if (userAccountControl & UF_ACCOUNTDISABLE) {
                flags.client = 0;
        }
        if (userAccountControl & UF_LOCKOUT) {
                flags.locked_out = 1;
        }
/*
        if (userAccountControl & UF_PASSWORD_NOTREQD) {
                flags.invalid = 1;
        }
*/
/*
        UF_PASSWORD_CANT_CHANGE and UF_ENCRYPTED_TEXT_PASSWORD_ALLOWED are irrelevent
*/
        if (userAccountControl & UF_TEMP_DUPLICATE_ACCOUNT) {
                flags.invalid = 1;
        }

/* UF_DONT_EXPIRE_PASSWD and UF_USE_DES_KEY_ONLY handled in samba_kdc_message2entry() */

/*
        if (userAccountControl & UF_MNS_LOGON_ACCOUNT) {
                flags.invalid = 1;
        }
*/
        if (userAccountControl & UF_SMARTCARD_REQUIRED) {
                flags.require_hwauth = 1;
        }
        if (userAccountControl & UF_TRUSTED_FOR_DELEGATION) {
                flags.ok_as_delegate = 1;
        }
        if (userAccountControl & UF_TRUSTED_TO_AUTHENTICATE_FOR_DELEGATION) {
                /*
                 * this is confusing...
                 *
                 * UF_TRUSTED_FOR_DELEGATION
                 * => ok_as_delegate
                 *
                 * and
                 *
                 * UF_TRUSTED_TO_AUTHENTICATE_FOR_DELEGATION
                 * => trusted_for_delegation
                 */
                flags.trusted_for_delegation = 1;
        }
        if (!(userAccountControl & UF_NOT_DELEGATED)) {
                flags.forwardable = 1;
                flags.proxiable = 1;
        }

        if (userAccountControl & UF_DONT_REQUIRE_PREAUTH) {
                flags.require_preauth = 0;
        } else {
                flags.require_preauth = 1;
        }

        if (userAccountControl & UF_NO_AUTH_DATA_REQUIRED) {
                flags.no_auth_data_reqd = 1;
        }

        return flags;
}

static int samba_kdc_entry_destructor(struct samba_kdc_entry *p)
{
        if (p->db_entry != NULL) {
                /*
                 * A sdb_entry still has a reference
                 */
                return -1;
        }

        if (p->kdc_entry != NULL) {
                /*
                 * hdb_entry or krb5_db_entry still
                 * have a reference...
                 */
                return -1;
        }

        return 0;
}

/*
 * Sort keys in descending order of strength.
 *
 * Explanaton from Greg Hudson:
 *
 * To encrypt tickets only the first returned key is used by the MIT KDC.  The
 * other keys just communicate support for session key enctypes, and aren't
 * really used.  The encryption key for the ticket enc part doesn't have
 * to be of a type requested by the client. The session key enctype is chosen
 * based on the client preference order, limited by the set of enctypes present
 * in the server keys (unless the string attribute is set on the server
 * principal overriding that set).
 */

static int sdb_key_strength_priority(krb5_enctype etype)
{
        static const krb5_enctype etype_list[] = {
                ENCTYPE_AES256_CTS_HMAC_SHA1_96,
                ENCTYPE_AES128_CTS_HMAC_SHA1_96,
                ENCTYPE_DES3_CBC_SHA1,
                ENCTYPE_ARCFOUR_HMAC,
                ENCTYPE_DES_CBC_MD5,
                ENCTYPE_DES_CBC_MD4,
                ENCTYPE_DES_CBC_CRC,
                ENCTYPE_NULL
        };
        int i;

        for (i = 0; i < ARRAY_SIZE(etype_list); i++) {
                if (etype == etype_list[i]) {
                        break;
                }
        }

        return ARRAY_SIZE(etype_list) - i;
}

static int sdb_key_strength_cmp(const struct sdb_key *k1, const struct sdb_key *k2)
{
        int p1 = sdb_key_strength_priority(KRB5_KEY_TYPE(&k1->key));
        int p2 = sdb_key_strength_priority(KRB5_KEY_TYPE(&k2->key));

        if (p1 == p2) {
                return 0;
        }

        if (p1 > p2) {
                /*
                 * Higher priority comes first
                 */
                return -1;
        } else {
                return 1;
        }
}

static void samba_kdc_sort_keys(struct sdb_keys *keys)
{
        if (keys == NULL) {
                return;
        }

        TYPESAFE_QSORT(keys->val, keys->len, sdb_key_strength_cmp);
}

int samba_kdc_set_fixed_keys(krb5_context context,
                             const struct ldb_val *secretbuffer,
                             uint32_t supported_enctypes,
                             struct sdb_keys *keys)
{
        uint16_t allocated_keys = 0;
        int ret;

        allocated_keys = 3;
        keys->len = 0;
        keys->val = calloc(allocated_keys, sizeof(struct sdb_key));
        if (keys->val == NULL) {
                memset(secretbuffer->data, 0, secretbuffer->length);
                ret = ENOMEM;
                goto out;
        }

        if (supported_enctypes & ENC_HMAC_SHA1_96_AES256) {
                struct sdb_key key = {};

                ret = smb_krb5_keyblock_init_contents(context,
                                                      ENCTYPE_AES256_CTS_HMAC_SHA1_96,
                                                      secretbuffer->data,
                                                      MIN(secretbuffer->length, 32),
                                                      &key.key);
                if (ret) {
                        memset(secretbuffer->data, 0, secretbuffer->length);
                        goto out;
                }

                keys->val[keys->len] = key;
                keys->len++;
        }

        if (supported_enctypes & ENC_HMAC_SHA1_96_AES128) {
                struct sdb_key key = {};

                ret = smb_krb5_keyblock_init_contents(context,
                                                      ENCTYPE_AES128_CTS_HMAC_SHA1_96,
                                                      secretbuffer->data,
                                                      MIN(secretbuffer->length, 16),
                                                      &key.key);
                if (ret) {
                        memset(secretbuffer->data, 0, secretbuffer->length);
                        goto out;
                }

                keys->val[keys->len] = key;
                keys->len++;
        }

        if (supported_enctypes & ENC_RC4_HMAC_MD5) {
                struct sdb_key key = {};

                ret = smb_krb5_keyblock_init_contents(context,
                                                      ENCTYPE_ARCFOUR_HMAC,
                                                      secretbuffer->data,
                                                      MIN(secretbuffer->length, 16),
                                                      &key.key);
                if (ret) {
                        memset(secretbuffer->data, 0, secretbuffer->length);
                        goto out;
                }

                keys->val[keys->len] = key;
                keys->len++;
        }
        ret = 0;
out:
        return ret;
}


static int samba_kdc_set_random_keys(krb5_context context,
                                     uint32_t supported_enctypes,
                                     struct sdb_keys *keys)
{
        struct ldb_val secret_val;
        uint8_t secretbuffer[32];

        /*
         * Fake keys until we have a better way to reject
         * non-pkinit requests.
         *
         * We just need to indicate which encryption types are
         * supported.
         */
        generate_secret_buffer(secretbuffer, sizeof(secretbuffer));

        secret_val = data_blob_const(secretbuffer,
                                     sizeof(secretbuffer));
        return samba_kdc_set_fixed_keys(context,
                                        &secret_val,
                                        supported_enctypes,
                                        keys);
}

struct samba_kdc_user_keys {
        struct sdb_keys *skeys;
        uint32_t kvno;
        uint32_t *returned_kvno;
        uint32_t supported_enctypes;
        uint32_t *available_enctypes;
        const struct samr_Password *nthash;
        const char *salt_string;
        uint16_t num_pkeys;
        const struct package_PrimaryKerberosKey4 *pkeys;
};

static krb5_error_code samba_kdc_fill_user_keys(krb5_context context,
                                                struct samba_kdc_user_keys *p)
{
        /*
         * Make sure we'll never reveal DES keys
         */
        uint32_t supported_enctypes = p->supported_enctypes & ENC_ALL_TYPES;
        uint32_t _available_enctypes = 0;
        uint32_t *available_enctypes = p->available_enctypes;
        uint32_t _returned_kvno = 0;
        uint32_t *returned_kvno = p->returned_kvno;
        uint32_t num_pkeys = p->num_pkeys;
        uint32_t allocated_keys = num_pkeys;
        uint32_t i;
        int ret;

        if (available_enctypes == NULL) {
                available_enctypes = &_available_enctypes;
        }

        *available_enctypes = 0;

        if (returned_kvno == NULL) {
                returned_kvno = &_returned_kvno;
        }

        *returned_kvno = p->kvno;

        if (p->nthash != NULL) {
                allocated_keys += 1;
        }

        allocated_keys = MAX(1, allocated_keys);

        /* allocate space to decode into */
        p->skeys->len = 0;
        p->skeys->val = calloc(allocated_keys, sizeof(struct sdb_key));
        if (p->skeys->val == NULL) {
                return ENOMEM;
        }

        for (i=0; i < num_pkeys; i++) {
                struct sdb_key key = {};
                uint32_t enctype_bit;

                if (p->pkeys[i].value == NULL) {
                        continue;
                }

                enctype_bit = kerberos_enctype_to_bitmap(p->pkeys[i].keytype);
                if (!(enctype_bit & supported_enctypes)) {
                        continue;
                }

                if (p->salt_string != NULL) {
                        DATA_BLOB salt;

                        salt = data_blob_string_const(p->salt_string);

                        key.salt = calloc(1, sizeof(*key.salt));
                        if (key.salt == NULL) {
                                ret = ENOMEM;
                                goto fail;
                        }

                        key.salt->type = KRB5_PW_SALT;

                        ret = smb_krb5_copy_data_contents(&key.salt->salt,
                                                          salt.data,
                                                          salt.length);
                        if (ret) {
                                ZERO_STRUCTP(key.salt);
                                sdb_key_free(&key);
                                goto fail;
                        }
                }

                ret = smb_krb5_keyblock_init_contents(context,
                                                      p->pkeys[i].keytype,
                                                      p->pkeys[i].value->data,
                                                      p->pkeys[i].value->length,
                                                      &key.key);
                if (ret == 0) {
                        p->skeys->val[p->skeys->len++] = key;
                        *available_enctypes |= enctype_bit;
                        continue;
                }
                ZERO_STRUCT(key.key);
                sdb_key_free(&key);
                if (ret == KRB5_PROG_ETYPE_NOSUPP) {
                        DEBUG(2,("Unsupported keytype ignored - type %u\n",
                                 p->pkeys[i].keytype));
                        ret = 0;
                        continue;
                }

                goto fail;
        }

        if (p->nthash != NULL && (supported_enctypes & ENC_RC4_HMAC_MD5)) {
                struct sdb_key key = {};

                ret = smb_krb5_keyblock_init_contents(context,
                                                      ENCTYPE_ARCFOUR_HMAC,
                                                      p->nthash->hash,
                                                      sizeof(p->nthash->hash),
                                                      &key.key);
                if (ret == 0) {
                        p->skeys->val[p->skeys->len++] = key;

                        *available_enctypes |= ENC_RC4_HMAC_MD5;
                } else if (ret == KRB5_PROG_ETYPE_NOSUPP) {
                        DEBUG(2,("Unsupported keytype ignored - type %u\n",
                                 ENCTYPE_ARCFOUR_HMAC));
                        ret = 0;
                }
                if (ret != 0) {
                        goto fail;
                }
        }

        samba_kdc_sort_keys(p->skeys);

        return 0;
fail:
        sdb_keys_free(p->skeys);
        return ret;
}

krb5_error_code samba_kdc_message2entry_keys(krb5_context context,
                                             TALLOC_CTX *mem_ctx,
                                             const struct ldb_message *msg,
                                             bool is_krbtgt,
                                             bool is_rodc,
                                             uint32_t userAccountControl,
                                             enum samba_kdc_ent_type ent_type,
                                             unsigned flags,
                                             krb5_kvno requested_kvno,
                                             struct sdb_entry *entry,
                                             const uint32_t supported_enctypes_in,
                                             uint32_t *supported_enctypes_out)
{
        krb5_error_code ret = 0;
        enum ndr_err_code ndr_err;
        struct samr_Password *hash;
        unsigned int num_ntPwdHistory = 0;
        struct samr_Password *ntPwdHistory = NULL;
        struct samr_Password *old_hash = NULL;
        struct samr_Password *older_hash = NULL;
        const struct ldb_val *sc_val;
        struct supplementalCredentialsBlob scb;
        struct supplementalCredentialsPackage *scpk = NULL;
        struct package_PrimaryKerberosBlob _pkb;
        struct package_PrimaryKerberosCtr4 *pkb4 = NULL;
        int krbtgt_number = 0;
        uint32_t current_kvno;
        uint32_t old_kvno = 0;
        uint32_t older_kvno = 0;
        uint32_t returned_kvno = 0;
        uint16_t i;
        struct samba_kdc_user_keys keys = { .num_pkeys = 0, };
        struct samba_kdc_user_keys old_keys = { .num_pkeys = 0, };
        struct samba_kdc_user_keys older_keys = { .num_pkeys = 0, };
        uint32_t available_enctypes = 0;
        uint32_t supported_enctypes = supported_enctypes_in;

        *supported_enctypes_out = 0;

        /* Is this the krbtgt or a RODC krbtgt */
        if (is_rodc) {
                krbtgt_number = ldb_msg_find_attr_as_int(msg, "msDS-SecondaryKrbTgtNumber", -1);

                if (krbtgt_number == -1) {
                        return EINVAL;
                }
                if (krbtgt_number == 0) {
                        return EINVAL;
                }
        }

        if ((ent_type == SAMBA_KDC_ENT_TYPE_CLIENT)
            && (userAccountControl & UF_SMARTCARD_REQUIRED)) {
                ret = samba_kdc_set_random_keys(context,
                                                supported_enctypes,
                                                &entry->keys);

                *supported_enctypes_out = supported_enctypes;

                goto out;
        }

        current_kvno = ldb_msg_find_attr_as_int(msg, "msDS-KeyVersionNumber", 0);
        if (current_kvno > 1) {
                old_kvno = current_kvno - 1;
        }
        if (current_kvno > 2) {
                older_kvno = current_kvno - 2;
        }
        if (is_krbtgt) {
                /*
                 * Even for the main krbtgt account
                 * we have to strictly split the kvno into
                 * two 16-bit parts and the upper 16-bit
                 * need to be all zero, even if
                 * the msDS-KeyVersionNumber has a value
                 * larger than 65535.
                 *
                 * See https://bugzilla.samba.org/show_bug.cgi?id=14951
                 */
                current_kvno = SAMBA_KVNO_GET_VALUE(current_kvno);
                old_kvno = SAMBA_KVNO_GET_VALUE(old_kvno);
                older_kvno = SAMBA_KVNO_GET_VALUE(older_kvno);
                requested_kvno = SAMBA_KVNO_GET_VALUE(requested_kvno);
        }

        /* Get keys from the db */

        hash = samdb_result_hash(mem_ctx, msg, "unicodePwd");
        num_ntPwdHistory = samdb_result_hashes(mem_ctx, msg,
                                               "ntPwdHistory",
                                               &ntPwdHistory);
        if (num_ntPwdHistory > 1) {
                old_hash = &ntPwdHistory[1];
        }
        if (num_ntPwdHistory > 2) {
                older_hash = &ntPwdHistory[1];
        }
        sc_val = ldb_msg_find_ldb_val(msg, "supplementalCredentials");

        /* supplementalCredentials if present */
        if (sc_val) {
                ndr_err = ndr_pull_struct_blob_all(sc_val, mem_ctx, &scb,
                                                   (ndr_pull_flags_fn_t)ndr_pull_supplementalCredentialsBlob);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        dump_data(0, sc_val->data, sc_val->length);
                        ret = EINVAL;
                        goto out;
                }

                if (scb.sub.signature != SUPPLEMENTAL_CREDENTIALS_SIGNATURE) {
                        if (scb.sub.num_packages != 0) {
                                NDR_PRINT_DEBUG(supplementalCredentialsBlob, &scb);
                                ret = EINVAL;
                                goto out;
                        }
                }

                for (i=0; i < scb.sub.num_packages; i++) {
                        if (strcmp("Primary:Kerberos-Newer-Keys", scb.sub.packages[i].name) == 0) {
                                scpk = &scb.sub.packages[i];
                                if (!scpk->data || !scpk->data[0]) {
                                        scpk = NULL;
                                        continue;
                                }
                                break;
                        }
                }
        }
        /*
         * Primary:Kerberos-Newer-Keys element
         * of supplementalCredentials
         *
         * The legacy Primary:Kerberos only contains
         * single DES keys, which are completely ignored
         * now.
         */
        if (scpk) {
                DATA_BLOB blob;

                blob = strhex_to_data_blob(mem_ctx, scpk->data);
                if (!blob.data) {
                        ret = ENOMEM;
                        goto out;
                }

                /* we cannot use ndr_pull_struct_blob_all() here, as w2k and w2k3 add padding bytes */
                ndr_err = ndr_pull_struct_blob(&blob, mem_ctx, &_pkb,
                                               (ndr_pull_flags_fn_t)ndr_pull_package_PrimaryKerberosBlob);
                if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                        ret = EINVAL;
                        krb5_set_error_message(context, ret, "samba_kdc_message2entry_keys: could not parse package_PrimaryKerberosBlob");
                        krb5_warnx(context, "samba_kdc_message2entry_keys: could not parse package_PrimaryKerberosBlob");
                        goto out;
                }

                if (_pkb.version != 4) {
                        ret = EINVAL;
                        krb5_set_error_message(context, ret, "samba_kdc_message2entry_keys: Primary:Kerberos-Newer-Keys not version 4");
                        krb5_warnx(context, "samba_kdc_message2entry_keys: Primary:Kerberos-Newer-Keys not version 4");
                        goto out;
                }

                pkb4 = &_pkb.ctr.ctr4;
        }

        keys = (struct samba_kdc_user_keys) {
                .kvno = current_kvno,
                .supported_enctypes = supported_enctypes,
                .nthash = hash,
                .salt_string = pkb4 != NULL ? pkb4->salt.string : NULL,
                .num_pkeys = pkb4 != NULL ? pkb4->num_keys : 0,
                .pkeys = pkb4 != NULL ? pkb4->keys : NULL,
        };

        old_keys = (struct samba_kdc_user_keys) {
                .kvno = old_kvno,
                .supported_enctypes = supported_enctypes,
                .nthash = old_hash,
                .salt_string = pkb4 != NULL ? pkb4->salt.string : NULL,
                .num_pkeys = pkb4 != NULL ? pkb4->num_old_keys : 0,
                .pkeys = pkb4 != NULL ? pkb4->old_keys : NULL,
        };
        older_keys = (struct samba_kdc_user_keys) {
                .kvno = older_kvno,
                .supported_enctypes = supported_enctypes,
                .nthash = older_hash,
                .salt_string = pkb4 != NULL ? pkb4->salt.string : NULL,
                .num_pkeys = pkb4 != NULL ? pkb4->num_older_keys : 0,
                .pkeys = pkb4 != NULL ? pkb4->older_keys : NULL,
        };

        if (flags & SDB_F_KVNO_SPECIFIED) {
                if (requested_kvno == keys.kvno) {
                        /*
                         * The current kvno was requested,
                         * so we return it.
                         */
                        keys.skeys = &entry->keys;
                        keys.available_enctypes = &available_enctypes;
                        keys.returned_kvno = &returned_kvno;
                } else if (requested_kvno == 0) {
                        /*
                         * don't return any keys
                         */
                } else if (requested_kvno == old_keys.kvno) {
                        /*
                         * return the old keys as default keys
                         * with the requested kvno.
                         */
                        old_keys.skeys = &entry->keys;
                        old_keys.available_enctypes = &available_enctypes;
                        old_keys.returned_kvno = &returned_kvno;
                } else if (requested_kvno == older_keys.kvno) {
                        /*
                         * return the older keys as default keys
                         * with the requested kvno.
                         */
                        older_keys.skeys = &entry->keys;
                        older_keys.available_enctypes = &available_enctypes;
                        older_keys.returned_kvno = &returned_kvno;
                } else {
                        /*
                         * don't return any keys
                         */
                }
        } else {
                bool include_history = false;

                if ((flags & SDB_F_GET_CLIENT) && (flags & SDB_F_FOR_AS_REQ)) {
                        include_history = true;
                } else if (flags & SDB_F_ADMIN_DATA) {
                        include_history = true;
                }

                keys.skeys = &entry->keys;
                keys.available_enctypes = &available_enctypes;
                keys.returned_kvno = &returned_kvno;

                if (include_history && old_keys.kvno != 0) {
                        old_keys.skeys = &entry->old_keys;
                }
                if (include_history && older_keys.kvno != 0) {
                        older_keys.skeys = &entry->older_keys;
                }
        }

        if (keys.skeys != NULL) {
                ret = samba_kdc_fill_user_keys(context, &keys);
                if (ret != 0) {
                        goto out;
                }
        }

        if (old_keys.skeys != NULL) {
                ret = samba_kdc_fill_user_keys(context, &old_keys);
                if (ret != 0) {
                        goto out;
                }
        }

        if (older_keys.skeys != NULL) {
                ret = samba_kdc_fill_user_keys(context, &older_keys);
                if (ret != 0) {
                        goto out;
                }
        }

        *supported_enctypes_out |= available_enctypes;

        /* Set FAST support bits */
        *supported_enctypes_out |= supported_enctypes & (ENC_FAST_SUPPORTED |
                                                         ENC_COMPOUND_IDENTITY_SUPPORTED |
                                                         ENC_CLAIMS_SUPPORTED);

        if (is_krbtgt) {
                /*
                 * Even for the main krbtgt account
                 * we have to strictly split the kvno into
                 * two 16-bit parts and the upper 16-bit
                 * need to be all zero, even if
                 * the msDS-KeyVersionNumber has a value
                 * larger than 65535.
                 *
                 * See https://bugzilla.samba.org/show_bug.cgi?id=14951
                 */
                returned_kvno = SAMBA_KVNO_AND_KRBTGT(returned_kvno, krbtgt_number);
        }
        entry->kvno = returned_kvno;

out:
        return ret;
}

static int principal_comp_strcmp_int(krb5_context context,
                                     krb5_const_principal principal,
                                     unsigned int component,
                                     const char *string,
                                     bool do_strcasecmp)
{
        const char *p;

#if defined(HAVE_KRB5_PRINCIPAL_GET_COMP_STRING)
        p = krb5_principal_get_comp_string(context, principal, component);
        if (p == NULL) {
                return -1;
        }
        if (do_strcasecmp) {
                return strcasecmp(p, string);
        } else {
                return strcmp(p, string);
        }
#else
        size_t len;
        krb5_data *d;
        if (component >= krb5_princ_size(context, principal)) {
                return -1;
        }

        d = krb5_princ_component(context, principal, component);
        if (d == NULL) {
                return -1;
        }

        p = d->data;

        len = strlen(string);

        /*
         * We explicitly return -1 or 1. Subtracting of the two lengths might
         * give the wrong result if the result overflows or loses data when
         * narrowed to int.
         */
        if (d->length < len) {
                return -1;
        } else if (d->length > len) {
                return 1;
        }

        if (do_strcasecmp) {
                return strncasecmp(p, string, len);
        } else {
                return memcmp(p, string, len);
        }
#endif
}

static int principal_comp_strcasecmp(krb5_context context,
                                     krb5_const_principal principal,
                                     unsigned int component,
                                     const char *string)
{
        return principal_comp_strcmp_int(context, principal,
                                         component, string, true);
}

static int principal_comp_strcmp(krb5_context context,
                                 krb5_const_principal principal,
                                 unsigned int component,
                                 const char *string)
{
        return principal_comp_strcmp_int(context, principal,
                                         component, string, false);
}

static bool is_kadmin_changepw(krb5_context context,
                               krb5_const_principal principal)
{
        return krb5_princ_size(context, principal) == 2 &&
                (principal_comp_strcmp(context, principal, 0, "kadmin") == 0) &&
                (principal_comp_strcmp(context, principal, 1, "changepw") == 0);
}

static krb5_error_code samba_kdc_get_entry_principal(
                krb5_context context,
                struct samba_kdc_db_context *kdc_db_ctx,
                const char *samAccountName,
                enum samba_kdc_ent_type ent_type,
                unsigned flags,
                bool is_kadmin_changepw,
                krb5_const_principal in_princ,
                krb5_principal *out_princ)
{
        struct loadparm_context *lp_ctx = kdc_db_ctx->lp_ctx;
        krb5_error_code code = 0;
        bool canon = flags & (SDB_F_CANON|SDB_F_FORCE_CANON);

        /*
         * If we are set to canonicalize, we get back the fixed UPPER
         * case realm, and the real username (ie matching LDAP
         * samAccountName)
         *
         * Otherwise, if we are set to enterprise, we
         * get back the whole principal as-sent
         *
         * Finally, if we are not set to canonicalize, we get back the
         * fixed UPPER case realm, but the as-sent username
         */

        /*
         * We need to ensure that the kadmin/changepw principal isn't able to
         * issue krbtgt tickets, even if canonicalization is turned on.
         */
        if (!is_kadmin_changepw) {
                if (ent_type == SAMBA_KDC_ENT_TYPE_KRBTGT && canon) {
                        /*
                         * When requested to do so, ensure that the
                         * both realm values in the principal are set
                         * to the upper case, canonical realm
                         */
                        code = smb_krb5_make_principal(context,
                                                       out_princ,
                                                       lpcfg_realm(lp_ctx),
                                                       "krbtgt",
                                                       lpcfg_realm(lp_ctx),
                                                       NULL);
                        if (code != 0) {
                                return code;
                        }
                        smb_krb5_principal_set_type(context,
                                                    *out_princ,
                                                    KRB5_NT_SRV_INST);

                        return 0;
                }

                if ((canon && flags & (SDB_F_FORCE_CANON|SDB_F_FOR_AS_REQ)) ||
                    (ent_type == SAMBA_KDC_ENT_TYPE_ANY && in_princ == NULL)) {
                        /*
                         * SDB_F_CANON maps from the canonicalize flag in the
                         * packet, and has a different meaning between AS-REQ
                         * and TGS-REQ.  We only change the principal in the
                         * AS-REQ case.
                         *
                         * The SDB_F_FORCE_CANON if for new MIT KDC code that
                         * wants the canonical name in all lookups, and takes
                         * care to canonicalize only when appropriate.
                         */
                        code = smb_krb5_make_principal(context,
                                                      out_princ,
                                                      lpcfg_realm(lp_ctx),
                                                      samAccountName,
                                                      NULL);
                        return code;
                }
        }

        /*
         * For a krbtgt entry, this appears to be required regardless of the
         * canonicalize flag from the client.
         */
        code = krb5_copy_principal(context, in_princ, out_princ);
        if (code != 0) {
                return code;
        }

        /*
         * While we have copied the client principal, tests show that Win2k3
         * returns the 'corrected' realm, not the client-specified realm.  This
         * code attempts to replace the client principal's realm with the one
         * we determine from our records
         */
        code = smb_krb5_principal_set_realm(context,
                                            *out_princ,
                                            lpcfg_realm(lp_ctx));

        return code;
}

/*
 * Construct an hdb_entry from a directory entry.
 */
static krb5_error_code samba_kdc_message2entry(krb5_context context,
                                               struct samba_kdc_db_context *kdc_db_ctx,
                                               TALLOC_CTX *mem_ctx,
                                               krb5_const_principal principal,
                                               enum samba_kdc_ent_type ent_type,
                                               unsigned flags,
                                               krb5_kvno kvno,
                                               struct ldb_dn *realm_dn,
                                               struct ldb_message *msg,
                                               struct sdb_entry *entry)
{
        struct loadparm_context *lp_ctx = kdc_db_ctx->lp_ctx;
        uint32_t userAccountControl;
        uint32_t msDS_User_Account_Control_Computed;
        krb5_error_code ret = 0;
        krb5_boolean is_computer = FALSE;
        struct samba_kdc_entry *p;
        NTTIME acct_expiry;
        NTSTATUS status;
        bool protected_user = false;
        uint32_t rid;
        bool is_krbtgt = false;
        bool is_rodc = false;
        struct ldb_message_element *objectclasses;
        struct ldb_val computer_val = data_blob_string_const("computer");
        uint32_t supported_enctypes
                = ldb_msg_find_attr_as_uint(msg,
                                            "msDS-SupportedEncryptionTypes",
                                            0);
        const char *samAccountName = ldb_msg_find_attr_as_string(msg, "samAccountName", NULL);

        ZERO_STRUCTP(entry);

        if (ldb_msg_find_element(msg, "msDS-SecondaryKrbTgtNumber")) {
                is_rodc = true;
        }

        if (!samAccountName) {
                ret = ENOENT;
                krb5_set_error_message(context, ret, "samba_kdc_message2entry: no samAccountName present");
                goto out;
        }

        objectclasses = ldb_msg_find_element(msg, "objectClass");

        if (objectclasses && ldb_msg_find_val(objectclasses, &computer_val)) {
                is_computer = TRUE;
        }

        p = talloc_zero(mem_ctx, struct samba_kdc_entry);
        if (!p) {
                ret = ENOMEM;
                goto out;
        }

        p->is_rodc = is_rodc;
        p->kdc_db_ctx = kdc_db_ctx;
        p->realm_dn = talloc_reference(p, realm_dn);
        if (!p->realm_dn) {
                ret = ENOMEM;
                goto out;
        }

        talloc_set_destructor(p, samba_kdc_entry_destructor);

        entry->skdc_entry = p;

        userAccountControl = ldb_msg_find_attr_as_uint(msg, "userAccountControl", 0);

        msDS_User_Account_Control_Computed
                = ldb_msg_find_attr_as_uint(msg,
                                            "msDS-User-Account-Control-Computed",
                                            UF_ACCOUNTDISABLE);

        /*
         * This brings in the lockout flag, block the account if not
         * found.  We need the weird UF_ACCOUNTDISABLE check because
         * we do not want to fail open if the value is not returned,
         * but 0 is a valid value (all OK)
         */
        if (msDS_User_Account_Control_Computed == UF_ACCOUNTDISABLE) {
                ret = EINVAL;
                krb5_set_error_message(context, ret, "samba_kdc_message2entry: "
                                "no msDS-User-Account-Control-Computed present");
                goto out;
        } else {
                userAccountControl |= msDS_User_Account_Control_Computed;
        }

        if (ent_type == SAMBA_KDC_ENT_TYPE_KRBTGT) {
                p->is_krbtgt = true;
        }

        /* First try and figure out the flags based on the userAccountControl */
        entry->flags = uf2SDBFlags(context, userAccountControl, ent_type);

        /*
         * Take control of the returned principal here, rather than
         * allowing the Heimdal code to do it as we have specific
         * behaviour around the forced realm to honour
         */
        entry->flags.force_canonicalize = true;

        /* Windows 2008 seems to enforce this (very sensible) rule by
         * default - don't allow offline attacks on a user's password
         * by asking for a ticket to them as a service (encrypted with
         * their probably patheticly insecure password) */

        if (entry->flags.server
            && lpcfg_parm_bool(lp_ctx, NULL, "kdc", "require spn for service", true)) {
                if (!is_computer && !ldb_msg_find_attr_as_string(msg, "servicePrincipalName", NULL)) {
                        entry->flags.server = 0;
                }
        }

        /*
         * We restrict a 3-part SPN ending in my domain/realm to full
         * domain controllers.
         *
         * This avoids any cases where (eg) a demoted DC still has
         * these more restricted SPNs.
         */
        if (krb5_princ_size(context, principal) > 2) {
                char *third_part
                        = smb_krb5_principal_get_comp_string(mem_ctx,
                                                             context,
                                                             principal,
                                                             2);
                bool is_our_realm =
                         lpcfg_is_my_domain_or_realm(lp_ctx,
                                                     third_part);
                bool is_dc = userAccountControl &
                        (UF_SERVER_TRUST_ACCOUNT | UF_PARTIAL_SECRETS_ACCOUNT);
                if (is_our_realm && !is_dc) {
                        entry->flags.server = 0;
                }
        }
        /*
         * To give the correct type of error to the client, we must
         * not just return the entry without .server set, we must
         * pretend the principal does not exist.  Otherwise we may
         * return ERR_POLICY instead of
         * KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN
         */
        if (ent_type == SAMBA_KDC_ENT_TYPE_SERVER && entry->flags.server == 0) {
                ret = SDB_ERR_NOENTRY;
                krb5_set_error_message(context, ret, "samba_kdc_message2entry: no servicePrincipalName present for this server, refusing with no-such-entry");
                goto out;
        }
        if (flags & SDB_F_ADMIN_DATA) {
                /* These (created_by, modified_by) parts of the entry are not relevant for Samba4's use
                 * of the Heimdal KDC.  They are stored in a the traditional
                 * DB for audit purposes, and still form part of the structure
                 * we must return */

                /* use 'whenCreated' */
                entry->created_by.time = ldb_msg_find_krb5time_ldap_time(msg, "whenCreated", 0);
                /* use 'kadmin' for now (needed by mit_samba) */

                ret = smb_krb5_make_principal(context,
                                              &entry->created_by.principal,
                                              lpcfg_realm(lp_ctx), "kadmin", NULL);
                if (ret) {
                        krb5_clear_error_message(context);
                        goto out;
                }

                entry->modified_by = (struct sdb_event *) malloc(sizeof(struct sdb_event));
                if (entry->modified_by == NULL) {
                        ret = ENOMEM;
                        krb5_set_error_message(context, ret, "malloc: out of memory");
                        goto out;
                }

                /* use 'whenChanged' */
                entry->modified_by->time = ldb_msg_find_krb5time_ldap_time(msg, "whenChanged", 0);
                /* use 'kadmin' for now (needed by mit_samba) */
                ret = smb_krb5_make_principal(context,
                                              &entry->modified_by->principal,
                                              lpcfg_realm(lp_ctx), "kadmin", NULL);
                if (ret) {
                        krb5_clear_error_message(context);
                        goto out;
                }
        }


        /* The lack of password controls etc applies to krbtgt by
         * virtue of being that particular RID */
        status = dom_sid_split_rid(NULL, samdb_result_dom_sid(mem_ctx, msg, "objectSid"), NULL, &rid);

        if (!NT_STATUS_IS_OK(status)) {
                ret = EINVAL;
                goto out;
        }

        if (rid == DOMAIN_RID_KRBTGT) {
                char *realm = NULL;

                entry->valid_end = NULL;
                entry->pw_end = NULL;

                entry->flags.invalid = 0;
                entry->flags.server = 1;

                realm = smb_krb5_principal_get_realm(
                        mem_ctx, context, principal);
                if (realm == NULL) {
                        ret = ENOMEM;
                        goto out;
                }

                /* Don't mark all requests for the krbtgt/realm as
                 * 'change password', as otherwise we could get into
                 * trouble, and not enforce the password expirty.
                 * Instead, only do it when request is for the kpasswd service */
                if (ent_type == SAMBA_KDC_ENT_TYPE_SERVER &&
                    is_kadmin_changepw(context, principal) &&
                    lpcfg_is_my_domain_or_realm(lp_ctx, realm)) {
                        entry->flags.change_pw = 1;
                }

                TALLOC_FREE(realm);

                entry->flags.client = 0;
                entry->flags.forwardable = 1;
                entry->flags.ok_as_delegate = 1;
        } else if (is_rodc) {
                /* The RODC krbtgt account is like the main krbtgt,
                 * but it does not have a changepw or kadmin
                 * service */

                entry->valid_end = NULL;
                entry->pw_end = NULL;

                /* Also don't allow the RODC krbtgt to be a client (it should not be needed) */
                entry->flags.client = 0;
                entry->flags.invalid = 0;
                entry->flags.server = 1;

                entry->flags.client = 0;
                entry->flags.forwardable = 1;
                entry->flags.ok_as_delegate = 0;
        } else if (entry->flags.server && ent_type == SAMBA_KDC_ENT_TYPE_SERVER) {
                /* The account/password expiry only applies when the account is used as a
                 * client (ie password login), not when used as a server */

                /* Make very well sure we don't use this for a client,
                 * it could bypass the password restrictions */
                entry->flags.client = 0;

                entry->valid_end = NULL;
                entry->pw_end = NULL;

        } else {
                NTTIME must_change_time
                        = samdb_result_nttime(msg,
                                        "msDS-UserPasswordExpiryTimeComputed",
                                        0);
                if (must_change_time == 0x7FFFFFFFFFFFFFFFULL) {
                        entry->pw_end = NULL;
                } else {
                        entry->pw_end = malloc(sizeof(*entry->pw_end));
                        if (entry->pw_end == NULL) {
                                ret = ENOMEM;
                                goto out;
                        }
                        *entry->pw_end = nt_time_to_unix(must_change_time);
                }

                acct_expiry = samdb_result_account_expires(msg);
                if (acct_expiry == 0x7FFFFFFFFFFFFFFFULL) {
                        entry->valid_end = NULL;
                } else {
                        entry->valid_end = malloc(sizeof(*entry->valid_end));
                        if (entry->valid_end == NULL) {
                                ret = ENOMEM;
                                goto out;
                        }
                        *entry->valid_end = nt_time_to_unix(acct_expiry);
                }
        }

        ret = samba_kdc_get_entry_principal(context,
                                            kdc_db_ctx,
                                            samAccountName,
                                            ent_type,
                                            flags,
                                            entry->flags.change_pw,
                                            principal,
                                            &entry->principal);
        if (ret != 0) {
                krb5_clear_error_message(context);
                goto out;
        }

        entry->valid_start = NULL;

        entry->max_life = malloc(sizeof(*entry->max_life));
        if (entry->max_life == NULL) {
                ret = ENOMEM;
                goto out;
        }

        if (ent_type == SAMBA_KDC_ENT_TYPE_SERVER) {
                *entry->max_life = kdc_db_ctx->policy.svc_tkt_lifetime;
        } else if (ent_type == SAMBA_KDC_ENT_TYPE_KRBTGT || ent_type == SAMBA_KDC_ENT_TYPE_CLIENT) {
                *entry->max_life = kdc_db_ctx->policy.usr_tkt_lifetime;
        } else {
                *entry->max_life = MIN(kdc_db_ctx->policy.svc_tkt_lifetime,
                                                kdc_db_ctx->policy.usr_tkt_lifetime);
        }

        if (entry->flags.change_pw) {
                /* Limit lifetime of kpasswd tickets to two minutes or less. */
                *entry->max_life = MIN(*entry->max_life, CHANGEPW_LIFETIME);
        }

        entry->max_renew = malloc(sizeof(*entry->max_renew));
        if (entry->max_renew == NULL) {
                ret = ENOMEM;
                goto out;
        }

        *entry->max_renew = kdc_db_ctx->policy.renewal_lifetime;

        if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT && (flags & SDB_F_FOR_AS_REQ)) {
                int result;
                struct auth_user_info_dc *user_info_dc = NULL;
                /*
                 * These protections only apply to clients, so servers in the
                 * Protected Users group may still have service tickets to them
                 * encrypted with RC4. For accounts looked up as servers, note
                 * that 'msg' does not contain the 'memberOf' attribute for
                 * determining whether the account is a member of Protected
                 * Users.
                 *
                 * Additionally, Microsoft advises that accounts for services
                 * and computers should never be members of Protected Users, or
                 * they may fail to authenticate.
                 */
                status = samba_kdc_get_user_info_from_db(p, msg, &user_info_dc);
                if (!NT_STATUS_IS_OK(status)) {
                        ret = EINVAL;
                        goto out;
                }

                result = dsdb_is_protected_user(kdc_db_ctx->samdb,
                                                user_info_dc->sids,
                                                user_info_dc->num_sids);
                if (result == -1) {
                        ret = EINVAL;
                        goto out;
                }

                protected_user = result;

                if (protected_user) {
                        *entry->max_life = MIN(*entry->max_life, 4 * 60 * 60);
                        *entry->max_renew = MIN(*entry->max_renew, 4 * 60 * 60);

                        entry->flags.forwardable = 0;
                        entry->flags.proxiable = 0;
                }
        }

        if (rid == DOMAIN_RID_KRBTGT || is_rodc) {
                bool enable_fast;

                is_krbtgt = true;

                /* KDCs (and KDCs on RODCs) use AES */
                supported_enctypes |= ENC_HMAC_SHA1_96_AES128 | ENC_HMAC_SHA1_96_AES256;

                enable_fast = lpcfg_kdc_enable_fast(kdc_db_ctx->lp_ctx);
                if (enable_fast) {
                        supported_enctypes |= ENC_FAST_SUPPORTED;
                }
        } else if (userAccountControl & (UF_PARTIAL_SECRETS_ACCOUNT|UF_SERVER_TRUST_ACCOUNT)) {
                /* DCs and RODCs comptuer accounts use AES */
                supported_enctypes |= ENC_HMAC_SHA1_96_AES128 | ENC_HMAC_SHA1_96_AES256;
        } else if (ent_type == SAMBA_KDC_ENT_TYPE_CLIENT ||
                   (ent_type == SAMBA_KDC_ENT_TYPE_ANY)) {
                /* for AS-REQ the client chooses the enc types it
                 * supports, and this will vary between computers a
                 * user logs in from.
                 *
                 * likewise for 'any' return as much as is supported,
                 * to export into a keytab */
                supported_enctypes = ENC_ALL_TYPES;
        }

        /* If UF_USE_DES_KEY_ONLY has been set, then don't allow use of the newer enc types */
        if (userAccountControl & UF_USE_DES_KEY_ONLY) {
                supported_enctypes = 0;
        } else {
                /* Otherwise, add in the default enc types */
                supported_enctypes |= ENC_RC4_HMAC_MD5;
        }

        if (protected_user) {
                supported_enctypes &= ~ENC_RC4_HMAC_MD5;
        }

        /* Get keys from the db */
        ret = samba_kdc_message2entry_keys(context, p, msg,
                                           is_krbtgt, is_rodc,
                                           userAccountControl,
                                           ent_type, flags, kvno, entry,
                                           supported_enctypes,
                                           &supported_enctypes);
        if (ret) {
                /* Could be bogus data in the entry, or out of memory */
                goto out;
        }

        if (entry->keys.len == 0) {
                if (kdc_db_ctx->rodc) {
                        /*
                         * We are on an RODC, but don't have keys for this
                         * account.  Signal this to the caller
                         */
                        auth_sam_trigger_repl_secret(kdc_db_ctx,
                                                     kdc_db_ctx->msg_ctx,
                                                     kdc_db_ctx->ev_ctx,
                                                     msg->dn);
                        return SDB_ERR_NOT_FOUND_HERE;
                }

                /*
                 * oh, no password.  Apparently (comment in
                 * hdb-ldap.c) this violates the ASN.1, but this
                 * allows an entry with no keys (yet).
                 */
        }

        p->msg = talloc_steal(p, msg);
        p->supported_enctypes = supported_enctypes;

out:
        if (ret != 0) {
                /* This doesn't free ent itself, that is for the eventual caller to do */
                sdb_entry_free(entry);
        } else {
                talloc_steal(kdc_db_ctx, p);
        }

        return ret;
}

/*
 * Construct an hdb_entry from a directory entry.
 * The kvno is what the remote client asked for
 */
static krb5_error_code samba_kdc_trust_message2entry(krb5_context context,
                                               struct samba_kdc_db_context *kdc_db_ctx,
                                               TALLOC_CTX *mem_ctx,
                                               enum trust_direction direction,
                                               struct ldb_dn *realm_dn,
                                               unsigned flags,
                                               uint32_t kvno,
                                               struct ldb_message *msg,
                                               struct sdb_entry *entry)
{
        struct loadparm_context *lp_ctx = kdc_db_ctx->lp_ctx;
        const char *our_realm = lpcfg_realm(lp_ctx);
        char *partner_realm = NULL;
        const char *realm = NULL;
        const char *krbtgt_realm = NULL;
        DATA_BLOB password_utf16 = data_blob_null;
        DATA_BLOB password_utf8 = data_blob_null;
        struct samr_Password _password_hash;
        const struct samr_Password *password_hash = NULL;
        const struct ldb_val *password_val;
        struct trustAuthInOutBlob password_blob;
        struct samba_kdc_entry *p;
        bool use_previous = false;
        uint32_t current_kvno;
        uint32_t previous_kvno;
        uint32_t num_keys = 0;
        enum ndr_err_code ndr_err;
        int ret;
        unsigned int i;
        struct AuthenticationInformationArray *auth_array;
        struct timeval tv;
        NTTIME an_hour_ago;
        uint32_t *auth_kvno;
        bool preferr_current = false;
        uint32_t supported_enctypes = ENC_RC4_HMAC_MD5;
        struct lsa_TrustDomainInfoInfoEx *tdo = NULL;
        NTSTATUS status;

        ZERO_STRUCTP(entry);

        if (dsdb_functional_level(kdc_db_ctx->samdb) >= DS_DOMAIN_FUNCTION_2008) {
                supported_enctypes = ldb_msg_find_attr_as_uint(msg,
                                        "msDS-SupportedEncryptionTypes",
                                        supported_enctypes);
        }

        status = dsdb_trust_parse_tdo_info(mem_ctx, msg, &tdo);
        if (!NT_STATUS_IS_OK(status)) {
                krb5_clear_error_message(context);
                ret = ENOMEM;
                goto out;
        }

        if (!(tdo->trust_direction & direction)) {
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        if (tdo->trust_type != LSA_TRUST_TYPE_UPLEVEL) {
                /*
                 * Only UPLEVEL domains support kerberos here,
                 * as we don't support LSA_TRUST_TYPE_MIT.
                 */
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        if (tdo->trust_attributes & LSA_TRUST_ATTRIBUTE_CROSS_ORGANIZATION) {
                /*
                 * We don't support selective authentication yet.
                 */
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        if (tdo->domain_name.string == NULL) {
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }
        partner_realm = strupper_talloc(mem_ctx, tdo->domain_name.string);
        if (partner_realm == NULL) {
                krb5_clear_error_message(context);
                ret = ENOMEM;
                goto out;
        }

        if (direction == INBOUND) {
                realm = our_realm;
                krbtgt_realm = partner_realm;

                password_val = ldb_msg_find_ldb_val(msg, "trustAuthIncoming");
        } else { /* OUTBOUND */
                realm = partner_realm;
                krbtgt_realm = our_realm;

                password_val = ldb_msg_find_ldb_val(msg, "trustAuthOutgoing");
        }

        if (password_val == NULL) {
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        ndr_err = ndr_pull_struct_blob(password_val, mem_ctx, &password_blob,
                                       (ndr_pull_flags_fn_t)ndr_pull_trustAuthInOutBlob);
        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                krb5_clear_error_message(context);
                ret = EINVAL;
                goto out;
        }

        p = talloc_zero(mem_ctx, struct samba_kdc_entry);
        if (!p) {
                ret = ENOMEM;
                goto out;
        }

        p->is_trust = true;
        p->kdc_db_ctx = kdc_db_ctx;
        p->realm_dn = realm_dn;
        p->supported_enctypes = supported_enctypes;

        talloc_set_destructor(p, samba_kdc_entry_destructor);

        entry->skdc_entry = p;

        /* use 'whenCreated' */
        entry->created_by.time = ldb_msg_find_krb5time_ldap_time(msg, "whenCreated", 0);
        /* use 'kadmin' for now (needed by mit_samba) */
        ret = smb_krb5_make_principal(context,
                                      &entry->created_by.principal,
                                      realm, "kadmin", NULL);
        if (ret) {
                krb5_clear_error_message(context);
                goto out;
        }

        /*
         * We always need to generate the canonicalized principal
         * with the values of our database.
         */
        ret = smb_krb5_make_principal(context, &entry->principal, realm,
                                      "krbtgt", krbtgt_realm, NULL);
        if (ret) {
                krb5_clear_error_message(context);
                goto out;
        }
        smb_krb5_principal_set_type(context, entry->principal,
                                    KRB5_NT_SRV_INST);

        entry->valid_start = NULL;

        /* we need to work out if we are going to use the current or
         * the previous password hash.
         * We base this on the kvno the client passes in. If the kvno
         * passed in is equal to the current kvno in our database then
         * we use the current structure. If it is the current kvno-1,
         * then we use the previous substrucure.
         */

        /*
         * Windows preferrs the previous key for one hour.
         */
        tv = timeval_current();
        if (tv.tv_sec > 3600) {
                tv.tv_sec -= 3600;
        }
        an_hour_ago = timeval_to_nttime(&tv);

        /* first work out the current kvno */
        current_kvno = 0;
        for (i=0; i < password_blob.count; i++) {
                struct AuthenticationInformation *a =
                        &password_blob.current.array[i];

                if (a->LastUpdateTime <= an_hour_ago) {
                        preferr_current = true;
                }

                if (a->AuthType == TRUST_AUTH_TYPE_VERSION) {
                        current_kvno = a->AuthInfo.version.version;
                }
        }
        if (current_kvno == 0) {
                previous_kvno = 255;
        } else {
                previous_kvno = current_kvno - 1;
        }
        for (i=0; i < password_blob.count; i++) {
                struct AuthenticationInformation *a =
                        &password_blob.previous.array[i];

                if (a->AuthType == TRUST_AUTH_TYPE_VERSION) {
                        previous_kvno = a->AuthInfo.version.version;
                }
        }

        /* work out whether we will use the previous or current
           password */
        if (password_blob.previous.count == 0) {
                /* there is no previous password */
                use_previous = false;
        } else if (!(flags & SDB_F_KVNO_SPECIFIED)) {
                /*
                 * If not specified we use the lowest kvno
                 * for the first hour after an update.
                 */
                if (preferr_current) {
                        use_previous = false;
                } else if (previous_kvno < current_kvno) {
                        use_previous = true;
                } else {
                        use_previous = false;
                }
        } else if (kvno == current_kvno) {
                /*
                 * Exact match ...
                 */
                use_previous = false;
        } else if (kvno == previous_kvno) {
                /*
                 * Exact match ...
                 */
                use_previous = true;
        } else {
                /*
                 * Fallback to the current one for anything else
                 */
                use_previous = false;
        }

        if (use_previous) {
                auth_array = &password_blob.previous;
                auth_kvno = &previous_kvno;
        } else {
                auth_array = &password_blob.current;
                auth_kvno = &current_kvno;
        }

        /* use the kvno the client specified, if available */
        if (flags & SDB_F_KVNO_SPECIFIED) {
                entry->kvno = kvno;
        } else {
                entry->kvno = *auth_kvno;
        }

        for (i=0; i < auth_array->count; i++) {
                if (auth_array->array[i].AuthType == TRUST_AUTH_TYPE_CLEAR) {
                        bool ok;

                        password_utf16 = data_blob_const(auth_array->array[i].AuthInfo.clear.password,
                                                         auth_array->array[i].AuthInfo.clear.size);
                        if (password_utf16.length == 0) {
                                break;
                        }

                        if (supported_enctypes & ENC_RC4_HMAC_MD5) {
                                mdfour(_password_hash.hash, password_utf16.data, password_utf16.length);
                                if (password_hash == NULL) {
                                        num_keys += 1;
                                }
                                password_hash = &_password_hash;
                        }

                        if (!(supported_enctypes & (ENC_HMAC_SHA1_96_AES128|ENC_HMAC_SHA1_96_AES256))) {
                                break;
                        }

                        ok = convert_string_talloc(mem_ctx,
                                                   CH_UTF16MUNGED, CH_UTF8,
                                                   password_utf16.data,
                                                   password_utf16.length,
                                                   (void *)&password_utf8.data,
                                                   &password_utf8.length);
                        if (!ok) {
                                krb5_clear_error_message(context);
                                ret = ENOMEM;
                                goto out;
                        }

                        if (supported_enctypes & ENC_HMAC_SHA1_96_AES128) {
                                num_keys += 1;
                        }
                        if (supported_enctypes & ENC_HMAC_SHA1_96_AES256) {
                                num_keys += 1;
                        }
                        break;
                } else if (auth_array->array[i].AuthType == TRUST_AUTH_TYPE_NT4OWF) {
                        if (supported_enctypes & ENC_RC4_HMAC_MD5) {
                                password_hash = &auth_array->array[i].AuthInfo.nt4owf.password;
                                num_keys += 1;
                        }
                }
        }

        /* Must have found a cleartext or MD4 password */
        if (num_keys == 0) {
                DEBUG(1,(__location__ ": no usable key found\n"));
                krb5_clear_error_message(context);
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        entry->keys.val = calloc(num_keys, sizeof(struct sdb_key));
        if (entry->keys.val == NULL) {
                krb5_clear_error_message(context);
                ret = ENOMEM;
                goto out;
        }

        if (password_utf8.length != 0) {
                struct sdb_key key = {};
                krb5_const_principal salt_principal = entry->principal;
                krb5_data salt;
                krb5_data cleartext_data;

                cleartext_data.data = discard_const_p(char, password_utf8.data);
                cleartext_data.length = password_utf8.length;

                ret = smb_krb5_get_pw_salt(context,
                                           salt_principal,
                                           &salt);
                if (ret != 0) {
                        goto out;
                }

                if (supported_enctypes & ENC_HMAC_SHA1_96_AES256) {
                        ret = smb_krb5_create_key_from_string(context,
                                                              salt_principal,
                                                              &salt,
                                                              &cleartext_data,
                                                              ENCTYPE_AES256_CTS_HMAC_SHA1_96,
                                                              &key.key);
                        if (ret != 0) {
                                smb_krb5_free_data_contents(context, &salt);
                                goto out;
                        }

                        entry->keys.val[entry->keys.len] = key;
                        entry->keys.len++;
                }

                if (supported_enctypes & ENC_HMAC_SHA1_96_AES128) {
                        ret = smb_krb5_create_key_from_string(context,
                                                              salt_principal,
                                                              &salt,
                                                              &cleartext_data,
                                                              ENCTYPE_AES128_CTS_HMAC_SHA1_96,
                                                              &key.key);
                        if (ret != 0) {
                                smb_krb5_free_data_contents(context, &salt);
                                goto out;
                        }

                        entry->keys.val[entry->keys.len] = key;
                        entry->keys.len++;
                }

                smb_krb5_free_data_contents(context, &salt);
        }

        if (password_hash != NULL) {
                struct sdb_key key = {};

                ret = smb_krb5_keyblock_init_contents(context,
                                                      ENCTYPE_ARCFOUR_HMAC,
                                                      password_hash->hash,
                                                      sizeof(password_hash->hash),
                                                      &key.key);
                if (ret != 0) {
                        goto out;
                }

                entry->keys.val[entry->keys.len] = key;
                entry->keys.len++;
        }

        entry->flags = int2SDBFlags(0);
        entry->flags.immutable = 1;
        entry->flags.invalid = 0;
        entry->flags.server = 1;
        entry->flags.require_preauth = 1;

        entry->pw_end = NULL;

        entry->max_life = NULL;

        entry->max_renew = NULL;

        /* Match Windows behavior and allow forwardable flag in cross-realm. */
        entry->flags.forwardable = 1;

        samba_kdc_sort_keys(&entry->keys);

        p->msg = talloc_steal(p, msg);

out:
        TALLOC_FREE(partner_realm);

        if (ret != 0) {
                /* This doesn't free ent itself, that is for the eventual caller to do */
                sdb_entry_free(entry);
        } else {
                talloc_steal(kdc_db_ctx, p);
        }

        return ret;

}

static krb5_error_code samba_kdc_lookup_trust(krb5_context context, struct ldb_context *ldb_ctx,
                                        TALLOC_CTX *mem_ctx,
                                        const char *realm,
                                        struct ldb_dn *realm_dn,
                                        struct ldb_message **pmsg)
{
        NTSTATUS status;
        const char * const *attrs = trust_attrs;

        status = dsdb_trust_search_tdo(ldb_ctx, realm, realm,
                                       attrs, mem_ctx, pmsg);
        if (NT_STATUS_IS_OK(status)) {
                return 0;
        } else if (NT_STATUS_EQUAL(status, NT_STATUS_OBJECT_NAME_NOT_FOUND)) {
                return SDB_ERR_NOENTRY;
        } else if (NT_STATUS_EQUAL(status, NT_STATUS_NO_MEMORY)) {
                int ret = ENOMEM;
                krb5_set_error_message(context, ret, "get_sam_result_trust: out of memory");
                return ret;
        } else {
                int ret = EINVAL;
                krb5_set_error_message(context, ret, "get_sam_result_trust: %s", nt_errstr(status));
                return ret;
        }
}

static krb5_error_code samba_kdc_lookup_client(krb5_context context,
                                                struct samba_kdc_db_context *kdc_db_ctx,
                                                TALLOC_CTX *mem_ctx,
                                                krb5_const_principal principal,
                                                const char **attrs,
                                                struct ldb_dn **realm_dn,
                                                struct ldb_message **msg)
{
        NTSTATUS nt_status;
        char *principal_string = NULL;

        if (smb_krb5_principal_get_type(context, principal) == KRB5_NT_ENTERPRISE_PRINCIPAL) {
                principal_string = smb_krb5_principal_get_comp_string(mem_ctx, context,
                                                                      principal, 0);
                if (principal_string == NULL) {
                        return ENOMEM;
                }
        } else {
                char *principal_string_m = NULL;
                krb5_error_code ret;

                ret = krb5_unparse_name(context, principal, &principal_string_m);
                if (ret != 0) {
                        return ret;
                }

                principal_string = talloc_strdup(mem_ctx, principal_string_m);
                SAFE_FREE(principal_string_m);
                if (principal_string == NULL) {
                        return ENOMEM;
                }
        }

        nt_status = sam_get_results_principal(kdc_db_ctx->samdb,
                                              mem_ctx, principal_string, attrs,
                                              realm_dn, msg);
        if (NT_STATUS_EQUAL(nt_status, NT_STATUS_NO_SUCH_USER)) {
                krb5_principal fallback_principal = NULL;
                unsigned int num_comp;
                char *fallback_realm = NULL;
                char *fallback_account = NULL;
                krb5_error_code ret;

                ret = krb5_parse_name(context, principal_string,
                                      &fallback_principal);
                TALLOC_FREE(principal_string);
                if (ret != 0) {
                        return ret;
                }

                num_comp = krb5_princ_size(context, fallback_principal);
                fallback_realm = smb_krb5_principal_get_realm(
                        mem_ctx, context, fallback_principal);
                if (fallback_realm == NULL) {
                        krb5_free_principal(context, fallback_principal);
                        return ENOMEM;
                }

                if (num_comp == 1) {
                        size_t len;

                        fallback_account = smb_krb5_principal_get_comp_string(mem_ctx,
                                                context, fallback_principal, 0);
                        if (fallback_account == NULL) {
                                krb5_free_principal(context, fallback_principal);
                                TALLOC_FREE(fallback_realm);
                                return ENOMEM;
                        }

                        len = strlen(fallback_account);
                        if (len >= 2 && fallback_account[len - 1] == '$') {
                                TALLOC_FREE(fallback_account);
                        }
                }
                krb5_free_principal(context, fallback_principal);
                fallback_principal = NULL;

                if (fallback_account != NULL) {
                        char *with_dollar;

                        with_dollar = talloc_asprintf(mem_ctx, "%s$",
                                                     fallback_account);
                        if (with_dollar == NULL) {
                                TALLOC_FREE(fallback_realm);
                                return ENOMEM;
                        }
                        TALLOC_FREE(fallback_account);

                        ret = smb_krb5_make_principal(context,
                                                      &fallback_principal,
                                                      fallback_realm,
                                                      with_dollar, NULL);
                        TALLOC_FREE(with_dollar);
                        if (ret != 0) {
                                TALLOC_FREE(fallback_realm);
                                return ret;
                        }
                }
                TALLOC_FREE(fallback_realm);

                if (fallback_principal != NULL) {
                        char *fallback_string = NULL;

                        ret = krb5_unparse_name(context,
                                                fallback_principal,
                                                &fallback_string);
                        if (ret != 0) {
                                krb5_free_principal(context, fallback_principal);
                                return ret;
                        }

                        nt_status = sam_get_results_principal(kdc_db_ctx->samdb,
                                                              mem_ctx,
                                                              fallback_string,
                                                              attrs,
                                                              realm_dn, msg);
                        SAFE_FREE(fallback_string);
                }
                krb5_free_principal(context, fallback_principal);
                fallback_principal = NULL;
        }
        TALLOC_FREE(principal_string);

        if (NT_STATUS_EQUAL(nt_status, NT_STATUS_NO_SUCH_USER)) {
                return SDB_ERR_NOENTRY;
        } else if (NT_STATUS_EQUAL(nt_status, NT_STATUS_NO_MEMORY)) {
                return ENOMEM;
        } else if (!NT_STATUS_IS_OK(nt_status)) {
                return EINVAL;
        }

        return 0;
}

static krb5_error_code samba_kdc_fetch_client(krb5_context context,
                                               struct samba_kdc_db_context *kdc_db_ctx,
                                               TALLOC_CTX *mem_ctx,
                                               krb5_const_principal principal,
                                               unsigned flags,
                                               krb5_kvno kvno,
                                               struct sdb_entry *entry)
{
        struct ldb_dn *realm_dn;
        krb5_error_code ret;
        struct ldb_message *msg = NULL;

        ret = samba_kdc_lookup_client(context, kdc_db_ctx,
                                      mem_ctx, principal, user_attrs,
                                      &realm_dn, &msg);
        if (ret != 0) {
                return ret;
        }

        ret = samba_kdc_message2entry(context, kdc_db_ctx, mem_ctx,
                                      principal, SAMBA_KDC_ENT_TYPE_CLIENT,
                                      flags, kvno,
                                      realm_dn, msg, entry);
        return ret;
}

static krb5_error_code samba_kdc_fetch_krbtgt(krb5_context context,
                                              struct samba_kdc_db_context *kdc_db_ctx,
                                              TALLOC_CTX *mem_ctx,
                                              krb5_const_principal principal,
                                              unsigned flags,
                                              uint32_t kvno,
                                              struct sdb_entry *entry)
{
        struct loadparm_context *lp_ctx = kdc_db_ctx->lp_ctx;
        krb5_error_code ret;
        struct ldb_message *msg = NULL;
        struct ldb_dn *realm_dn = ldb_get_default_basedn(kdc_db_ctx->samdb);
        char *realm_from_princ;
        char *realm_princ_comp = smb_krb5_principal_get_comp_string(mem_ctx, context, principal, 1);

        realm_from_princ = smb_krb5_principal_get_realm(
                mem_ctx, context, principal);
        if (realm_from_princ == NULL) {
                /* can't happen */
                return SDB_ERR_NOENTRY;
        }

        if (krb5_princ_size(context, principal) != 2
            || (principal_comp_strcmp(context, principal, 0, KRB5_TGS_NAME) != 0)) {
                /* Not a krbtgt */
                return SDB_ERR_NOENTRY;
        }

        /* krbtgt case.  Either us or a trusted realm */

        if (lpcfg_is_my_domain_or_realm(lp_ctx, realm_from_princ)
            && lpcfg_is_my_domain_or_realm(lp_ctx, realm_princ_comp)) {
                /* us, or someone quite like us */
                /* Cludge, cludge cludge.  If the realm part of krbtgt/realm,
                 * is in our db, then direct the caller at our primary
                 * krbtgt */

                int lret;
                unsigned int krbtgt_number;
                /* w2k8r2 sometimes gives us a kvno of 255 for inter-domain
                   trust tickets. We don't yet know what this means, but we do
                   seem to need to treat it as unspecified */
                if (flags & SDB_F_KVNO_SPECIFIED) {
                        krbtgt_number = SAMBA_KVNO_GET_KRBTGT(kvno);
                        if (kdc_db_ctx->rodc) {
                                if (krbtgt_number != kdc_db_ctx->my_krbtgt_number) {
                                        return SDB_ERR_NOT_FOUND_HERE;
                                }
                        }
                } else {
                        krbtgt_number = kdc_db_ctx->my_krbtgt_number;
                }

                if (krbtgt_number == kdc_db_ctx->my_krbtgt_number) {
                        lret = dsdb_search_one(kdc_db_ctx->samdb, mem_ctx,
                                               &msg, kdc_db_ctx->krbtgt_dn, LDB_SCOPE_BASE,
                                               krbtgt_attrs, DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                               "(objectClass=user)");
                } else {
                        /* We need to look up an RODC krbtgt (perhaps
                         * ours, if we are an RODC, perhaps another
                         * RODC if we are a read-write DC */
                        lret = dsdb_search_one(kdc_db_ctx->samdb, mem_ctx,
                                               &msg, realm_dn, LDB_SCOPE_SUBTREE,
                                               krbtgt_attrs,
                                               DSDB_SEARCH_SHOW_EXTENDED_DN | DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                               "(&(objectClass=user)(msDS-SecondaryKrbTgtNumber=%u))", (unsigned)(krbtgt_number));
                }

                if (lret == LDB_ERR_NO_SUCH_OBJECT) {
                        krb5_warnx(context, "samba_kdc_fetch: could not find KRBTGT number %u in DB!",
                                   (unsigned)(krbtgt_number));
                        krb5_set_error_message(context, SDB_ERR_NOENTRY,
                                               "samba_kdc_fetch: could not find KRBTGT number %u in DB!",
                                               (unsigned)(krbtgt_number));
                        return SDB_ERR_NOENTRY;
                } else if (lret != LDB_SUCCESS) {
                        krb5_warnx(context, "samba_kdc_fetch: could not find KRBTGT number %u in DB!",
                                   (unsigned)(krbtgt_number));
                        krb5_set_error_message(context, SDB_ERR_NOENTRY,
                                               "samba_kdc_fetch: could not find KRBTGT number %u in DB!",
                                               (unsigned)(krbtgt_number));
                        return SDB_ERR_NOENTRY;
                }

                ret = samba_kdc_message2entry(context, kdc_db_ctx, mem_ctx,
                                              principal, SAMBA_KDC_ENT_TYPE_KRBTGT,
                                              flags, kvno, realm_dn, msg, entry);
                if (ret != 0) {
                        krb5_warnx(context, "samba_kdc_fetch: self krbtgt message2entry failed");
                }
                return ret;

        } else {
                enum trust_direction direction = UNKNOWN;
                const char *realm = NULL;

                /* Either an inbound or outbound trust */

                if (strcasecmp(lpcfg_realm(lp_ctx), realm_from_princ) == 0) {
                        /* look for inbound trust */
                        direction = INBOUND;
                        realm = realm_princ_comp;
                } else if (principal_comp_strcasecmp(context, principal, 1, lpcfg_realm(lp_ctx)) == 0) {
                        /* look for outbound trust */
                        direction = OUTBOUND;
                        realm = realm_from_princ;
                } else {
                        krb5_warnx(context, "samba_kdc_fetch: not our realm for trusts ('%s', '%s')",
                                   realm_from_princ,
                                   realm_princ_comp);
                        krb5_set_error_message(context, SDB_ERR_NOENTRY, "samba_kdc_fetch: not our realm for trusts ('%s', '%s')",
                                               realm_from_princ,
                                               realm_princ_comp);
                        return SDB_ERR_NOENTRY;
                }

                /* Trusted domains are under CN=system */

                ret = samba_kdc_lookup_trust(context, kdc_db_ctx->samdb,
                                       mem_ctx,
                                       realm, realm_dn, &msg);

                if (ret != 0) {
                        krb5_warnx(context, "samba_kdc_fetch: could not find principal in DB");
                        krb5_set_error_message(context, ret, "samba_kdc_fetch: could not find principal in DB");
                        return ret;
                }

                ret = samba_kdc_trust_message2entry(context, kdc_db_ctx, mem_ctx,
                                                    direction,
                                                    realm_dn, flags, kvno, msg, entry);
                if (ret != 0) {
                        krb5_warnx(context, "samba_kdc_fetch: trust_message2entry failed for %s",
                                   ldb_dn_get_linearized(msg->dn));
                        krb5_set_error_message(context, ret, "samba_kdc_fetch: "
                                               "trust_message2entry failed for %s",
                                               ldb_dn_get_linearized(msg->dn));
                }
                return ret;
        }

}

static krb5_error_code samba_kdc_lookup_server(krb5_context context,
                                               struct samba_kdc_db_context *kdc_db_ctx,
                                               TALLOC_CTX *mem_ctx,
                                               krb5_const_principal principal,
                                               unsigned flags,
                                               const char **attrs,
                                               struct ldb_dn **realm_dn,
                                               struct ldb_message **msg)
{
        krb5_error_code ret;
        if ((smb_krb5_principal_get_type(context, principal) != KRB5_NT_ENTERPRISE_PRINCIPAL)
            && krb5_princ_size(context, principal) >= 2) {
                /* 'normal server' case */
                int ldb_ret;
                NTSTATUS nt_status;
                struct ldb_dn *user_dn;
                char *principal_string;

                ret = krb5_unparse_name_flags(context, principal,
                                              KRB5_PRINCIPAL_UNPARSE_NO_REALM,
                                              &principal_string);
                if (ret != 0) {
                        return ret;
                }

                /* At this point we may find the host is known to be
                 * in a different realm, so we should generate a
                 * referral instead */
                nt_status = crack_service_principal_name(kdc_db_ctx->samdb,
                                                         mem_ctx, principal_string,
                                                         &user_dn, realm_dn);
                free(principal_string);

                if (!NT_STATUS_IS_OK(nt_status)) {
                        return SDB_ERR_NOENTRY;
                }

                ldb_ret = dsdb_search_one(kdc_db_ctx->samdb,
                                          mem_ctx,
                                          msg, user_dn, LDB_SCOPE_BASE,
                                          attrs,
                                          DSDB_SEARCH_SHOW_EXTENDED_DN | DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                          "(objectClass=*)");
                if (ldb_ret != LDB_SUCCESS) {
                        return SDB_ERR_NOENTRY;
                }
                return 0;
        } else if (!(flags & SDB_F_FOR_AS_REQ)
                   && smb_krb5_principal_get_type(context, principal) == KRB5_NT_ENTERPRISE_PRINCIPAL) {
                /*
                 * The behaviour of accepting an
                 * KRB5_NT_ENTERPRISE_PRINCIPAL server principal
                 * containing a UPN only applies to TGS-REQ packets,
                 * not AS-REQ packets.
                 */
                return samba_kdc_lookup_client(context, kdc_db_ctx,
                                               mem_ctx, principal, attrs,
                                               realm_dn, msg);
        } else {
                /*
                 * This case is for:
                 *  - the AS-REQ, where we only accept
                 *    samAccountName based lookups for the server, no
                 *    matter if the name is an
                 *    KRB5_NT_ENTERPRISE_PRINCIPAL or not
                 *  - for the TGS-REQ when we are not given an
                 *    KRB5_NT_ENTERPRISE_PRINCIPAL, which also must
                 *    only lookup samAccountName based names.
                 */
                int lret;
                char *short_princ;
                krb5_principal enterprise_principal = NULL;
                krb5_const_principal used_principal = NULL;
                char *name1 = NULL;
                size_t len1 = 0;
                char *filter = NULL;

                if (smb_krb5_principal_get_type(context, principal) == KRB5_NT_ENTERPRISE_PRINCIPAL) {
                        char *str = NULL;
                        /* Need to reparse the enterprise principal to find the real target */
                        if (krb5_princ_size(context, principal) != 1) {
                                ret = KRB5_PARSE_MALFORMED;
                                krb5_set_error_message(context, ret, "samba_kdc_lookup_server: request for an "
                                                       "enterprise principal with wrong (%d) number of components",
                                                       krb5_princ_size(context, principal));
                                return ret;
                        }
                        str = smb_krb5_principal_get_comp_string(mem_ctx, context, principal, 0);
                        if (str == NULL) {
                                return KRB5_PARSE_MALFORMED;
                        }
                        ret = krb5_parse_name(context, str,
                                              &enterprise_principal);
                        talloc_free(str);
                        if (ret) {
                                return ret;
                        }
                        used_principal = enterprise_principal;
                } else {
                        used_principal = principal;
                }

                /* server as client principal case, but we must not lookup userPrincipalNames */
                *realm_dn = ldb_get_default_basedn(kdc_db_ctx->samdb);

                /* TODO: Check if it is our realm, otherwise give referral */

                ret = krb5_unparse_name_flags(context, used_principal,
                                              KRB5_PRINCIPAL_UNPARSE_NO_REALM |
                                              KRB5_PRINCIPAL_UNPARSE_DISPLAY,
                                              &short_princ);
                used_principal = NULL;
                krb5_free_principal(context, enterprise_principal);
                enterprise_principal = NULL;

                if (ret != 0) {
                        krb5_set_error_message(context, ret, "samba_kdc_lookup_principal: could not parse principal");
                        krb5_warnx(context, "samba_kdc_lookup_principal: could not parse principal");
                        return ret;
                }

                name1 = ldb_binary_encode_string(mem_ctx, short_princ);
                SAFE_FREE(short_princ);
                if (name1 == NULL) {
                        return ENOMEM;
                }
                len1 = strlen(name1);
                if (len1 >= 1 && name1[len1 - 1] != '$') {
                        filter = talloc_asprintf(mem_ctx,
                                        "(&(objectClass=user)(|(samAccountName=%s)(samAccountName=%s$)))",
                                        name1, name1);
                        if (filter == NULL) {
                                return ENOMEM;
                        }
                } else {
                        filter = talloc_asprintf(mem_ctx,
                                        "(&(objectClass=user)(samAccountName=%s))",
                                        name1);
                        if (filter == NULL) {
                                return ENOMEM;
                        }
                }

                lret = dsdb_search_one(kdc_db_ctx->samdb, mem_ctx, msg,
                                       *realm_dn, LDB_SCOPE_SUBTREE,
                                       attrs,
                                       DSDB_SEARCH_SHOW_EXTENDED_DN | DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                       "%s", filter);
                if (lret == LDB_ERR_NO_SUCH_OBJECT) {
                        DEBUG(10, ("Failed to find an entry for %s filter:%s\n",
                                  name1, filter));
                        return SDB_ERR_NOENTRY;
                }
                if (lret == LDB_ERR_CONSTRAINT_VIOLATION) {
                        DEBUG(10, ("Failed to find unique entry for %s filter:%s\n",
                                  name1, filter));
                        return SDB_ERR_NOENTRY;
                }
                if (lret != LDB_SUCCESS) {
                        DEBUG(0, ("Failed single search for %s - %s\n",
                                  name1, ldb_errstring(kdc_db_ctx->samdb)));
                        return SDB_ERR_NOENTRY;
                }
                return 0;
        }
        return SDB_ERR_NOENTRY;
}



static krb5_error_code samba_kdc_fetch_server(krb5_context context,
                                              struct samba_kdc_db_context *kdc_db_ctx,
                                              TALLOC_CTX *mem_ctx,
                                              krb5_const_principal principal,
                                              unsigned flags,
                                              krb5_kvno kvno,
                                              struct sdb_entry *entry)
{
        krb5_error_code ret;
        struct ldb_dn *realm_dn;
        struct ldb_message *msg;

        ret = samba_kdc_lookup_server(context, kdc_db_ctx, mem_ctx, principal,
                                      flags, server_attrs, &realm_dn, &msg);
        if (ret != 0) {
                return ret;
        }

        ret = samba_kdc_message2entry(context, kdc_db_ctx, mem_ctx,
                                      principal, SAMBA_KDC_ENT_TYPE_SERVER,
                                      flags, kvno,
                                      realm_dn, msg, entry);
        if (ret != 0) {
                char *client_name = NULL;
                krb5_error_code code;

                code = krb5_unparse_name(context, principal, &client_name);
                if (code == 0) {
                        krb5_warnx(context,
                                   "samba_kdc_fetch: message2entry failed for "
                                   "%s",
                                   client_name);
                } else {
                        krb5_warnx(context,
                                   "samba_kdc_fetch: message2entry and "
                                   "krb5_unparse_name failed");
                }
                SAFE_FREE(client_name);
        }

        return ret;
}

static krb5_error_code samba_kdc_lookup_realm(krb5_context context,
                                              struct samba_kdc_db_context *kdc_db_ctx,
                                              TALLOC_CTX *mem_ctx,
                                              krb5_const_principal principal,
                                              unsigned flags,
                                              struct sdb_entry *entry)
{
        TALLOC_CTX *frame = talloc_stackframe();
        NTSTATUS status;
        krb5_error_code ret;
        bool check_realm = false;
        const char *realm = NULL;
        struct dsdb_trust_routing_table *trt = NULL;
        const struct lsa_TrustDomainInfoInfoEx *tdo = NULL;
        unsigned int num_comp;
        bool ok;
        char *upper = NULL;

        num_comp = krb5_princ_size(context, principal);

        if (flags & SDB_F_GET_CLIENT) {
                if (flags & SDB_F_FOR_AS_REQ) {
                        check_realm = true;
                }
        }
        if (flags & SDB_F_GET_SERVER) {
                if (flags & SDB_F_FOR_TGS_REQ) {
                        check_realm = true;
                }
        }

        if (!check_realm) {
                TALLOC_FREE(frame);
                return 0;
        }

        realm = smb_krb5_principal_get_realm(frame, context, principal);
        if (realm == NULL) {
                TALLOC_FREE(frame);
                return ENOMEM;
        }

        /*
         * The requested realm needs to be our own
         */
        ok = lpcfg_is_my_domain_or_realm(kdc_db_ctx->lp_ctx, realm);
        if (!ok) {
                /*
                 * The request is not for us...
                 */
                TALLOC_FREE(frame);
                return SDB_ERR_NOENTRY;
        }

        if (smb_krb5_principal_get_type(context, principal) == KRB5_NT_ENTERPRISE_PRINCIPAL) {
                char *principal_string = NULL;
                krb5_principal enterprise_principal = NULL;
                char *enterprise_realm = NULL;

                if (num_comp != 1) {
                        TALLOC_FREE(frame);
                        return SDB_ERR_NOENTRY;
                }

                principal_string = smb_krb5_principal_get_comp_string(frame, context,
                                                                      principal, 0);
                if (principal_string == NULL) {
                        TALLOC_FREE(frame);
                        return ENOMEM;
                }

                ret = krb5_parse_name(context, principal_string,
                                      &enterprise_principal);
                TALLOC_FREE(principal_string);
                if (ret) {
                        TALLOC_FREE(frame);
                        return ret;
                }

                enterprise_realm = smb_krb5_principal_get_realm(
                        frame, context, enterprise_principal);
                krb5_free_principal(context, enterprise_principal);
                if (enterprise_realm != NULL) {
                        realm = enterprise_realm;
                }
        }

        if (flags & SDB_F_GET_SERVER) {
                char *service_realm = NULL;

                ret = principal_comp_strcmp(context, principal, 0, KRB5_TGS_NAME);
                if (ret == 0) {
                        /*
                         * we need to search krbtgt/ locally
                         */
                        TALLOC_FREE(frame);
                        return 0;
                }

                /*
                 * We need to check the last component against the routing table.
                 *
                 * Note this works only with 2 or 3 component principals, e.g:
                 *
                 * servicePrincipalName: ldap/W2K8R2-219.bla.base
                 * servicePrincipalName: ldap/W2K8R2-219.bla.base/bla.base
                 * servicePrincipalName: ldap/W2K8R2-219.bla.base/ForestDnsZones.bla.base
                 * servicePrincipalName: ldap/W2K8R2-219.bla.base/DomainDnsZones.bla.base
                 */

                if (num_comp == 2 || num_comp == 3) {
                        service_realm = smb_krb5_principal_get_comp_string(frame,
                                                                           context,
                                                                           principal,
                                                                           num_comp - 1);
                }

                if (service_realm != NULL) {
                        realm = service_realm;
                }
        }

        ok = lpcfg_is_my_domain_or_realm(kdc_db_ctx->lp_ctx, realm);
        if (ok) {
                /*
                 * skip the expensive routing lookup
                 */
                TALLOC_FREE(frame);
                return 0;
        }

        status = dsdb_trust_routing_table_load(kdc_db_ctx->samdb,
                                               frame, &trt);
        if (!NT_STATUS_IS_OK(status)) {
                TALLOC_FREE(frame);
                return EINVAL;
        }

        tdo = dsdb_trust_routing_by_name(trt, realm);
        if (tdo == NULL) {
                /*
                 * This principal has to be local
                 */
                TALLOC_FREE(frame);
                return 0;
        }

        if (tdo->trust_attributes & LSA_TRUST_ATTRIBUTE_WITHIN_FOREST) {
                /*
                 * TODO: handle the routing within the forest
                 *
                 * This should likely be handled in
                 * samba_kdc_message2entry() in case we're
                 * a global catalog. We'd need to check
                 * if realm_dn is our own domain and derive
                 * the dns domain name from realm_dn and check that
                 * against the routing table or fallback to
                 * the tdo we found here.
                 *
                 * But for now we don't support multiple domains
                 * in our forest correctly anyway.
                 *
                 * Just search in our local database.
                 */
                TALLOC_FREE(frame);
                return 0;
        }

        ZERO_STRUCTP(entry);

        ret = krb5_copy_principal(context, principal,
                                  &entry->principal);
        if (ret) {
                TALLOC_FREE(frame);
                return ret;
        }

        upper = strupper_talloc(frame, tdo->domain_name.string);
        if (upper == NULL) {
                TALLOC_FREE(frame);
                return ENOMEM;
        }

        ret = smb_krb5_principal_set_realm(context,
                                           entry->principal,
                                           upper);
        if (ret) {
                TALLOC_FREE(frame);
                return ret;
        }

        TALLOC_FREE(frame);
        return SDB_ERR_WRONG_REALM;
}

krb5_error_code samba_kdc_fetch(krb5_context context,
                                struct samba_kdc_db_context *kdc_db_ctx,
                                krb5_const_principal principal,
                                unsigned flags,
                                krb5_kvno kvno,
                                struct sdb_entry *entry)
{
        krb5_error_code ret = SDB_ERR_NOENTRY;
        TALLOC_CTX *mem_ctx;

        mem_ctx = talloc_named(kdc_db_ctx, 0, "samba_kdc_fetch context");
        if (!mem_ctx) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret, "samba_kdc_fetch: talloc_named() failed!");
                return ret;
        }

        ret = samba_kdc_lookup_realm(context, kdc_db_ctx, mem_ctx,
                                     principal, flags, entry);
        if (ret != 0) {
                goto done;
        }

        ret = SDB_ERR_NOENTRY;

        if (flags & SDB_F_GET_CLIENT) {
                ret = samba_kdc_fetch_client(context, kdc_db_ctx, mem_ctx, principal, flags, kvno, entry);
                if (ret != SDB_ERR_NOENTRY) goto done;
        }
        if (flags & SDB_F_GET_SERVER) {
                /* krbtgt fits into this situation for trusted realms, and for resolving different versions of our own realm name */
                ret = samba_kdc_fetch_krbtgt(context, kdc_db_ctx, mem_ctx, principal, flags, kvno, entry);
                if (ret != SDB_ERR_NOENTRY) goto done;

                /* We return 'no entry' if it does not start with krbtgt/, so move to the common case quickly */
                ret = samba_kdc_fetch_server(context, kdc_db_ctx, mem_ctx, principal, flags, kvno, entry);
                if (ret != SDB_ERR_NOENTRY) goto done;
        }
        if (flags & SDB_F_GET_KRBTGT) {
                ret = samba_kdc_fetch_krbtgt(context, kdc_db_ctx, mem_ctx, principal, flags, kvno, entry);
                if (ret != SDB_ERR_NOENTRY) goto done;
        }

done:
        talloc_free(mem_ctx);
        return ret;
}

struct samba_kdc_seq {
        unsigned int index;
        unsigned int count;
        struct ldb_message **msgs;
        struct ldb_dn *realm_dn;
};

static krb5_error_code samba_kdc_seq(krb5_context context,
                                     struct samba_kdc_db_context *kdc_db_ctx,
                                     struct sdb_entry *entry)
{
        krb5_error_code ret;
        struct samba_kdc_seq *priv = kdc_db_ctx->seq_ctx;
        const char *realm = lpcfg_realm(kdc_db_ctx->lp_ctx);
        struct ldb_message *msg = NULL;
        const char *sAMAccountName = NULL;
        krb5_principal principal = NULL;
        TALLOC_CTX *mem_ctx;

        if (!priv) {
                return SDB_ERR_NOENTRY;
        }

        mem_ctx = talloc_named(priv, 0, "samba_kdc_seq context");

        if (!mem_ctx) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret, "samba_kdc_seq: talloc_named() failed!");
                return ret;
        }

        while (priv->index < priv->count) {
                msg = priv->msgs[priv->index++];

                sAMAccountName = ldb_msg_find_attr_as_string(msg, "sAMAccountName", NULL);
                if (sAMAccountName != NULL) {
                        break;
                }
        }

        if (sAMAccountName == NULL) {
                ret = SDB_ERR_NOENTRY;
                goto out;
        }

        ret = smb_krb5_make_principal(context, &principal,
                                      realm, sAMAccountName, NULL);
        if (ret != 0) {
                goto out;
        }

        ret = samba_kdc_message2entry(context, kdc_db_ctx, mem_ctx,
                                      principal, SAMBA_KDC_ENT_TYPE_ANY,
                                      SDB_F_ADMIN_DATA|SDB_F_GET_ANY,
                                      0 /* kvno */,
                                      priv->realm_dn, msg, entry);

out:
        if (principal != NULL) {
                krb5_free_principal(context, principal);
        }

        if (ret != 0) {
                TALLOC_FREE(priv);
                kdc_db_ctx->seq_ctx = NULL;
        } else {
                talloc_free(mem_ctx);
        }

        return ret;
}

krb5_error_code samba_kdc_firstkey(krb5_context context,
                                   struct samba_kdc_db_context *kdc_db_ctx,
                                   struct sdb_entry *entry)
{
        struct ldb_context *ldb_ctx = kdc_db_ctx->samdb;
        struct samba_kdc_seq *priv = kdc_db_ctx->seq_ctx;
        char *realm;
        struct ldb_result *res = NULL;
        krb5_error_code ret;
        TALLOC_CTX *mem_ctx;
        int lret;

        if (priv) {
                TALLOC_FREE(priv);
                kdc_db_ctx->seq_ctx = NULL;
        }

        priv = (struct samba_kdc_seq *) talloc(kdc_db_ctx, struct samba_kdc_seq);
        if (!priv) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret, "talloc: out of memory");
                return ret;
        }

        priv->index = 0;
        priv->msgs = NULL;
        priv->realm_dn = ldb_get_default_basedn(ldb_ctx);
        priv->count = 0;

        mem_ctx = talloc_named(priv, 0, "samba_kdc_firstkey context");

        if (!mem_ctx) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret, "samba_kdc_firstkey: talloc_named() failed!");
                return ret;
        }

        ret = krb5_get_default_realm(context, &realm);
        if (ret != 0) {
                TALLOC_FREE(priv);
                return ret;
        }
        krb5_free_default_realm(context, realm);

        lret = dsdb_search(ldb_ctx, priv, &res,
                           priv->realm_dn, LDB_SCOPE_SUBTREE, user_attrs,
                           DSDB_SEARCH_NO_GLOBAL_CATALOG,
                           "(objectClass=user)");

        if (lret != LDB_SUCCESS) {
                TALLOC_FREE(priv);
                return SDB_ERR_NOENTRY;
        }

        priv->count = res->count;
        priv->msgs = talloc_steal(priv, res->msgs);
        talloc_free(res);

        kdc_db_ctx->seq_ctx = priv;

        ret = samba_kdc_seq(context, kdc_db_ctx, entry);

        if (ret != 0) {
                TALLOC_FREE(priv);
                kdc_db_ctx->seq_ctx = NULL;
        } else {
                talloc_free(mem_ctx);
        }
        return ret;
}

krb5_error_code samba_kdc_nextkey(krb5_context context,
                                  struct samba_kdc_db_context *kdc_db_ctx,
                                  struct sdb_entry *entry)
{
        return samba_kdc_seq(context, kdc_db_ctx, entry);
}

/* Check if a given entry may delegate or do s4u2self to this target principal
 *
 * The safest way to determine 'self' is to check the DB record made at
 * the time the principal was presented to the KDC.
 */
krb5_error_code
samba_kdc_check_client_matches_target_service(krb5_context context,
                                              struct samba_kdc_entry *skdc_entry_client,
                                              struct samba_kdc_entry *skdc_entry_server_target)
{
        struct dom_sid *orig_sid;
        struct dom_sid *target_sid;
        TALLOC_CTX *frame = talloc_stackframe();

        orig_sid = samdb_result_dom_sid(frame,
                                        skdc_entry_client->msg,
                                        "objectSid");
        target_sid = samdb_result_dom_sid(frame,
                                          skdc_entry_server_target->msg,
                                          "objectSid");

        /*
         * Allow delegation to the same record (representing a
         * principal), even if by a different name.  The easy and safe
         * way to prove this is by SID comparison
         */
        if (!(orig_sid && target_sid && dom_sid_equal(orig_sid, target_sid))) {
                talloc_free(frame);
                return KRB5KRB_AP_ERR_BADMATCH;
        }

        talloc_free(frame);
        return 0;
}

/* Certificates printed by a the Certificate Authority might have a
 * slightly different form of the user principal name to that in the
 * database.  Allow a mismatch where they both refer to the same
 * SID */

krb5_error_code
samba_kdc_check_pkinit_ms_upn_match(krb5_context context,
                                    struct samba_kdc_db_context *kdc_db_ctx,
                                    struct samba_kdc_entry *skdc_entry,
                                     krb5_const_principal certificate_principal)
{
        krb5_error_code ret;
        struct ldb_dn *realm_dn;
        struct ldb_message *msg;
        struct dom_sid *orig_sid;
        struct dom_sid *target_sid;
        const char *ms_upn_check_attrs[] = {
                "objectSid", NULL
        };

        TALLOC_CTX *mem_ctx = talloc_named(kdc_db_ctx, 0, "samba_kdc_check_pkinit_ms_upn_match");

        if (!mem_ctx) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret, "samba_kdc_fetch: talloc_named() failed!");
                return ret;
        }

        ret = samba_kdc_lookup_client(context, kdc_db_ctx,
                                      mem_ctx, certificate_principal,
                                      ms_upn_check_attrs, &realm_dn, &msg);

        if (ret != 0) {
                talloc_free(mem_ctx);
                return ret;
        }

        orig_sid = samdb_result_dom_sid(mem_ctx, skdc_entry->msg, "objectSid");
        target_sid = samdb_result_dom_sid(mem_ctx, msg, "objectSid");

        /* Consider these to be the same principal, even if by a different
         * name.  The easy and safe way to prove this is by SID
         * comparison */
        if (!(orig_sid && target_sid && dom_sid_equal(orig_sid, target_sid))) {
                talloc_free(mem_ctx);
#if defined(KRB5KDC_ERR_CLIENT_NAME_MISMATCH) /* MIT */
                return KRB5KDC_ERR_CLIENT_NAME_MISMATCH;
#else /* Heimdal (where this is an enum) */
                return KRB5_KDC_ERR_CLIENT_NAME_MISMATCH;
#endif
        }

        talloc_free(mem_ctx);
        return ret;
}

/*
 * Check if a given entry may delegate to this target principal
 * with S4U2Proxy.
 */
krb5_error_code
samba_kdc_check_s4u2proxy(krb5_context context,
                          struct samba_kdc_db_context *kdc_db_ctx,
                          struct samba_kdc_entry *skdc_entry,
                          krb5_const_principal target_principal)
{
        krb5_error_code ret;
        char *tmp = NULL;
        const char *client_dn = NULL;
        const char *target_principal_name = NULL;
        struct ldb_message_element *el;
        struct ldb_val val;
        unsigned int i;
        bool found = false;

        TALLOC_CTX *mem_ctx = talloc_named(kdc_db_ctx, 0, "samba_kdc_check_s4u2proxy");

        if (!mem_ctx) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret,
                                       "samba_kdc_check_s4u2proxy:"
                                       " talloc_named() failed!");
                return ret;
        }

        client_dn = ldb_dn_get_linearized(skdc_entry->msg->dn);
        if (!client_dn) {
                if (errno == 0) {
                        errno = ENOMEM;
                }
                ret = errno;
                krb5_set_error_message(context, ret,
                                       "samba_kdc_check_s4u2proxy:"
                                       " ldb_dn_get_linearized() failed!");
                return ret;
        }

        el = ldb_msg_find_element(skdc_entry->msg, "msDS-AllowedToDelegateTo");
        if (el == NULL) {
                ret = ENOENT;
                goto bad_option;
        }
        SMB_ASSERT(el->num_values != 0);

        /*
         * This is the Microsoft forwardable flag behavior.
         *
         * If the proxy (target) principal is NULL, and we have any authorized
         * delegation target, allow to forward.
         */
        if (target_principal == NULL) {
                return 0;
        }


        /*
         * The main heimdal code already checked that the target_principal
         * belongs to the same realm as the client.
         *
         * So we just need the principal without the realm,
         * as that is what is configured in the "msDS-AllowedToDelegateTo"
         * attribute.
         */
        ret = krb5_unparse_name_flags(context, target_principal,
                                      KRB5_PRINCIPAL_UNPARSE_NO_REALM, &tmp);
        if (ret) {
                talloc_free(mem_ctx);
                krb5_set_error_message(context, ret,
                                       "samba_kdc_check_s4u2proxy:"
                                       " krb5_unparse_name() failed!");
                return ret;
        }
        DEBUG(10,("samba_kdc_check_s4u2proxy: client[%s] for target[%s]\n",
                 client_dn, tmp));

        target_principal_name = talloc_strdup(mem_ctx, tmp);
        SAFE_FREE(tmp);
        if (target_principal_name == NULL) {
                ret = ENOMEM;
                krb5_set_error_message(context, ret,
                                       "samba_kdc_check_s4u2proxy:"
                                       " talloc_strdup() failed!");
                return ret;
        }

        val = data_blob_string_const(target_principal_name);

        for (i=0; i<el->num_values; i++) {
                struct ldb_val *val1 = &val;
                struct ldb_val *val2 = &el->values[i];
                int cmp;

                if (val1->length != val2->length) {
                        continue;
                }

                cmp = strncasecmp((const char *)val1->data,
                                  (const char *)val2->data,
                                  val1->length);
                if (cmp != 0) {
                        continue;
                }

                found = true;
                break;
        }

        if (!found) {
                ret = ENOENT;
                goto bad_option;
        }

        DEBUG(10,("samba_kdc_check_s4u2proxy: client[%s] allowed target[%s]\n",
                 client_dn, tmp));
        talloc_free(mem_ctx);
        return 0;

bad_option:
        krb5_set_error_message(context, ret,
                               "samba_kdc_check_s4u2proxy: client[%s] "
                               "not allowed for delegation to target[%s]",
                               client_dn,
                               target_principal_name);
        talloc_free(mem_ctx);
        return KRB5KDC_ERR_BADOPTION;
}

/*
 * This method is called for S4U2Proxy requests and implements the
 * resource-based constrained delegation variant, which can support
 * cross-realm delegation.
 */
krb5_error_code samba_kdc_check_s4u2proxy_rbcd(
                krb5_context context,
                struct samba_kdc_db_context *kdc_db_ctx,
                krb5_const_principal client_principal,
                krb5_const_principal server_principal,
                krb5_pac header_pac,
                struct samba_kdc_entry *proxy_skdc_entry)
{
        krb5_error_code code;
        enum ndr_err_code ndr_err;
        char *client_name = NULL;
        char *server_name = NULL;
        const char *proxy_dn = NULL;
        const DATA_BLOB *data = NULL;
        struct security_descriptor *rbcd_security_descriptor = NULL;
        struct auth_user_info_dc *user_info_dc = NULL;
        struct auth_session_info *session_info = NULL;
        uint32_t session_info_flags = AUTH_SESSION_INFO_SIMPLE_PRIVILEGES;
        /*
         * Testing shows that although Windows grants SEC_ADS_GENERIC_ALL access
         * in security descriptors it creates for RBCD, its KDC only requires
         * SEC_ADS_CONTROL_ACCESS for the access check to succeed.
         */
        uint32_t access_desired = SEC_ADS_CONTROL_ACCESS;
        uint32_t access_granted = 0;
        NTSTATUS nt_status;
        TALLOC_CTX *mem_ctx = NULL;

        mem_ctx = talloc_named(kdc_db_ctx,
                               0,
                               "samba_kdc_check_s4u2proxy_rbcd");
        if (mem_ctx == NULL) {
                errno = ENOMEM;
                code = errno;

                return code;
        }

        proxy_dn = ldb_dn_get_linearized(proxy_skdc_entry->msg->dn);
        if (proxy_dn == NULL) {
                DBG_ERR("ldb_dn_get_linearized failed for proxy_dn!\n");
                TALLOC_FREE(mem_ctx);
                if (errno == 0) {
                        errno = ENOMEM;
                }
                code = errno;

                goto out;
        }

        rbcd_security_descriptor = talloc_zero(mem_ctx,
                                               struct security_descriptor);
        if (rbcd_security_descriptor == NULL) {
                errno = ENOMEM;
                code = errno;

                goto out;
        }

        code = krb5_unparse_name_flags(context,
                                       client_principal,
                                       KRB5_PRINCIPAL_UNPARSE_DISPLAY,
                                       &client_name);
        if (code != 0) {
                DBG_ERR("Unable to parse client_principal!\n");
                goto out;
        }

        code = krb5_unparse_name_flags(context,
                                       server_principal,
                                       KRB5_PRINCIPAL_UNPARSE_DISPLAY,
                                       &server_name);
        if (code != 0) {
                DBG_ERR("Unable to parse server_principal!\n");
                SAFE_FREE(client_name);
                goto out;
        }

        DBG_INFO("Check delegation from client[%s] to server[%s] via "
                 "proxy[%s]\n",
                 client_name,
                 server_name,
                 proxy_dn);

        code = kerberos_pac_to_user_info_dc(mem_ctx,
                                            header_pac,
                                            context,
                                            &user_info_dc,
                                            NULL,
                                            NULL);
        if (code != 0) {
                goto out;
        }

        if (user_info_dc->info->authenticated) {
                session_info_flags |= AUTH_SESSION_INFO_AUTHENTICATED;
        }

        nt_status = auth_generate_session_info(mem_ctx,
                                               kdc_db_ctx->lp_ctx,
                                               kdc_db_ctx->samdb,
                                               user_info_dc,
                                               session_info_flags,
                                               &session_info);
        if (!NT_STATUS_IS_OK(nt_status)) {
                code = map_errno_from_nt_status(nt_status);
                goto out;
        }

        data = ldb_msg_find_ldb_val(proxy_skdc_entry->msg,
                                    "msDS-AllowedToActOnBehalfOfOtherIdentity");
        if (data == NULL) {
                DBG_ERR("Could not find security descriptor "
                        "msDS-AllowedToActOnBehalfOfOtherIdentity in "
                        "proxy[%s]\n",
                        proxy_dn);
                code = KRB5KDC_ERR_BADOPTION;
                goto out;
        }

        ndr_err = ndr_pull_struct_blob(
                        data,
                        mem_ctx,
                        rbcd_security_descriptor,
                        (ndr_pull_flags_fn_t)ndr_pull_security_descriptor);
        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                errno = ndr_map_error2errno(ndr_err);
                DBG_ERR("Failed to unmarshall "
                        "msDS-AllowedToActOnBehalfOfOtherIdentity "
                        "security descriptor of proxy[%s]\n",
                        proxy_dn);
                code = KRB5KDC_ERR_BADOPTION;
                goto out;
        }

        if (DEBUGLEVEL >= 10) {
                NDR_PRINT_DEBUG(security_token, session_info->security_token);
                NDR_PRINT_DEBUG(security_descriptor, rbcd_security_descriptor);
        }

        nt_status = sec_access_check_ds(rbcd_security_descriptor,
                                        session_info->security_token,
                                        access_desired,
                                        &access_granted,
                                        NULL,
                                        NULL);

        if (!NT_STATUS_IS_OK(nt_status)) {
                DBG_WARNING("RBCD: sec_access_check_ds(access_desired=%#08x, "
                            "access_granted:%#08x) failed with: %s\n",
                            access_desired,
                            access_granted,
                            nt_errstr(nt_status));

                code = KRB5KDC_ERR_BADOPTION;
                goto out;
        }

        DBG_NOTICE("RBCD: Access granted for client[%s]\n", client_name);

        code = 0;
out:
        SAFE_FREE(client_name);
        SAFE_FREE(server_name);

        TALLOC_FREE(mem_ctx);
        return code;
}

NTSTATUS samba_kdc_setup_db_ctx(TALLOC_CTX *mem_ctx, struct samba_kdc_base_context *base_ctx,
                                struct samba_kdc_db_context **kdc_db_ctx_out)
{
        int ldb_ret;
        struct ldb_message *msg;
        struct auth_session_info *session_info;
        struct samba_kdc_db_context *kdc_db_ctx;
        /* The idea here is very simple.  Using Kerberos to
         * authenticate the KDC to the LDAP server is higly likely to
         * be circular.
         *
         * In future we may set this up to use EXERNAL and SSL
         * certificates, for now it will almost certainly be NTLMSSP_SET_USERNAME
        */

        kdc_db_ctx = talloc_zero(mem_ctx, struct samba_kdc_db_context);
        if (kdc_db_ctx == NULL) {
                return NT_STATUS_NO_MEMORY;
        }
        kdc_db_ctx->ev_ctx = base_ctx->ev_ctx;
        kdc_db_ctx->lp_ctx = base_ctx->lp_ctx;
        kdc_db_ctx->msg_ctx = base_ctx->msg_ctx;

        /* get default kdc policy */
        lpcfg_default_kdc_policy(mem_ctx,
                                 base_ctx->lp_ctx,
                                 &kdc_db_ctx->policy.svc_tkt_lifetime,
                                 &kdc_db_ctx->policy.usr_tkt_lifetime,
                                 &kdc_db_ctx->policy.renewal_lifetime);

        session_info = system_session(kdc_db_ctx->lp_ctx);
        if (session_info == NULL) {
                return NT_STATUS_INTERNAL_ERROR;
        }

        /* Setup the link to secrets.ldb */

        kdc_db_ctx->secrets_db = secrets_db_connect(kdc_db_ctx,
                                                    base_ctx->lp_ctx);
        if (kdc_db_ctx->secrets_db == NULL) {
                DEBUG(1, ("samba_kdc_setup_db_ctx: "
                          "Cannot open secrets.ldb for KDC backend!"));
                talloc_free(kdc_db_ctx);
                return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
        }

        kdc_db_ctx->fx_cookie_dn = ldb_dn_new(kdc_db_ctx,
                                              kdc_db_ctx->secrets_db,
                                              "CN=FX Cookie");

        /* Setup the link to LDB */
        kdc_db_ctx->samdb = samdb_connect(kdc_db_ctx,
                                          base_ctx->ev_ctx,
                                          base_ctx->lp_ctx,
                                          session_info,
                                          NULL,
                                          0);
        if (kdc_db_ctx->samdb == NULL) {
                DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot open samdb for KDC backend!"));
                talloc_free(kdc_db_ctx);
                return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
        }

        /* Find out our own krbtgt kvno */
        ldb_ret = samdb_rodc(kdc_db_ctx->samdb, &kdc_db_ctx->rodc);
        if (ldb_ret != LDB_SUCCESS) {
                DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot determine if we are an RODC in KDC backend: %s\n",
                          ldb_errstring(kdc_db_ctx->samdb)));
                talloc_free(kdc_db_ctx);
                return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
        }
        if (kdc_db_ctx->rodc) {
                int my_krbtgt_number;
                const char *secondary_keytab[] = { "msDS-SecondaryKrbTgtNumber", NULL };
                struct ldb_dn *account_dn;
                struct ldb_dn *server_dn = samdb_server_dn(kdc_db_ctx->samdb, kdc_db_ctx);
                if (!server_dn) {
                        DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot determine server DN in KDC backend: %s\n",
                                  ldb_errstring(kdc_db_ctx->samdb)));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }

                ldb_ret = samdb_reference_dn(kdc_db_ctx->samdb, kdc_db_ctx, server_dn,
                                             "serverReference", &account_dn);
                if (ldb_ret != LDB_SUCCESS) {
                        DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot determine server account in KDC backend: %s\n",
                                  ldb_errstring(kdc_db_ctx->samdb)));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }

                ldb_ret = samdb_reference_dn(kdc_db_ctx->samdb, kdc_db_ctx, account_dn,
                                             "msDS-KrbTgtLink", &kdc_db_ctx->krbtgt_dn);
                talloc_free(account_dn);
                if (ldb_ret != LDB_SUCCESS) {
                        DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot determine RODC krbtgt account in KDC backend: %s\n",
                                  ldb_errstring(kdc_db_ctx->samdb)));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }

                ldb_ret = dsdb_search_one(kdc_db_ctx->samdb, kdc_db_ctx,
                                          &msg, kdc_db_ctx->krbtgt_dn, LDB_SCOPE_BASE,
                                          secondary_keytab,
                                          DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                          "(&(objectClass=user)(msDS-SecondaryKrbTgtNumber=*))");
                if (ldb_ret != LDB_SUCCESS) {
                        DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot read krbtgt account %s in KDC backend to get msDS-SecondaryKrbTgtNumber: %s: %s\n",
                                  ldb_dn_get_linearized(kdc_db_ctx->krbtgt_dn),
                                  ldb_errstring(kdc_db_ctx->samdb),
                                  ldb_strerror(ldb_ret)));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }
                my_krbtgt_number = ldb_msg_find_attr_as_int(msg, "msDS-SecondaryKrbTgtNumber", -1);
                if (my_krbtgt_number == -1) {
                        DEBUG(1, ("samba_kdc_setup_db_ctx: Cannot read msDS-SecondaryKrbTgtNumber from krbtgt account %s in KDC backend: got %d\n",
                                  ldb_dn_get_linearized(kdc_db_ctx->krbtgt_dn),
                                  my_krbtgt_number));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }
                kdc_db_ctx->my_krbtgt_number = my_krbtgt_number;

        } else {
                kdc_db_ctx->my_krbtgt_number = 0;
                ldb_ret = dsdb_search_one(kdc_db_ctx->samdb, kdc_db_ctx,
                                          &msg,
                                          ldb_get_default_basedn(kdc_db_ctx->samdb),
                                          LDB_SCOPE_SUBTREE,
                                          krbtgt_attrs,
                                          DSDB_SEARCH_NO_GLOBAL_CATALOG,
                                          "(&(objectClass=user)(samAccountName=krbtgt))");

                if (ldb_ret != LDB_SUCCESS) {
                        DEBUG(1, ("samba_kdc_fetch: could not find own KRBTGT in DB: %s\n", ldb_errstring(kdc_db_ctx->samdb)));
                        talloc_free(kdc_db_ctx);
                        return NT_STATUS_CANT_ACCESS_DOMAIN_INFO;
                }
                kdc_db_ctx->krbtgt_dn = talloc_steal(kdc_db_ctx, msg->dn);
                kdc_db_ctx->my_krbtgt_number = 0;
                talloc_free(msg);
        }
        *kdc_db_ctx_out = kdc_db_ctx;
        return NT_STATUS_OK;
}

krb5_error_code dsdb_extract_aes_256_key(krb5_context context,
                                         TALLOC_CTX *mem_ctx,
                                         const struct ldb_message *msg,
                                         uint32_t user_account_control,
                                         const uint32_t *kvno,
                                         uint32_t *kvno_out,
                                         DATA_BLOB *aes_256_key,
                                         DATA_BLOB *salt)
{
        krb5_error_code krb5_ret;
        uint32_t supported_enctypes;
        unsigned flags = SDB_F_GET_CLIENT;
        struct sdb_entry sentry = {};

        if (kvno != NULL) {
                flags |= SDB_F_KVNO_SPECIFIED;
        }

        krb5_ret = samba_kdc_message2entry_keys(context,
                                                mem_ctx,
                                                msg,
                                                false, /* is_krbtgt */
                                                false, /* is_rodc */
                                                user_account_control,
                                                SAMBA_KDC_ENT_TYPE_CLIENT,
                                                flags,
                                                (kvno != NULL) ? *kvno : 0,
                                                &sentry,
                                                ENC_HMAC_SHA1_96_AES256,
                                                &supported_enctypes);
        if (krb5_ret != 0) {
                DBG_ERR("Failed to parse supplementalCredentials "
                        "of %s with %s kvno using "
                        "ENCTYPE_HMAC_SHA1_96_AES256 "
                        "Kerberos Key: %s\n",
                        ldb_dn_get_linearized(msg->dn),
                        (kvno != NULL) ? "previous" : "current",
                        krb5_get_error_message(context,
                                               krb5_ret));
                return krb5_ret;
        }

        if ((supported_enctypes & ENC_HMAC_SHA1_96_AES256) == 0 ||
            sentry.keys.len != 1) {
                DBG_INFO("Failed to find a ENCTYPE_HMAC_SHA1_96_AES256 "
                         "key in supplementalCredentials "
                         "of %s at KVNO %u (got %u keys, expected 1)\n",
                         ldb_dn_get_linearized(msg->dn),
                         sentry.kvno,
                         sentry.keys.len);
                sdb_entry_free(&sentry);
                return ENOENT;
        }

        if (sentry.keys.val[0].salt == NULL) {
                DBG_INFO("Failed to find a salt in "
                         "supplementalCredentials "
                         "of %s at KVNO %u\n",
                         ldb_dn_get_linearized(msg->dn),
                         sentry.kvno);
                sdb_entry_free(&sentry);
                return ENOENT;
        }

        if (aes_256_key != NULL) {
                *aes_256_key = data_blob_talloc(mem_ctx,
                                                KRB5_KEY_DATA(&sentry.keys.val[0].key),
                                                KRB5_KEY_LENGTH(&sentry.keys.val[0].key));
                if (aes_256_key->data == NULL) {
                        sdb_entry_free(&sentry);
                        return ENOMEM;
                }
                talloc_keep_secret(aes_256_key->data);
        }

        if (salt != NULL) {
                *salt = data_blob_talloc(mem_ctx,
                                         sentry.keys.val[0].salt->salt.data,
                                         sentry.keys.val[0].salt->salt.length);
                if (salt->data == NULL) {
                        sdb_entry_free(&sentry);
                        return ENOMEM;
                }
        }

        if (kvno_out != NULL) {
                *kvno_out = sentry.kvno;
        }

        sdb_entry_free(&sentry);

        return 0;
}