CVE-2023-34968: mdssvc: introduce an allocating wrapper to sl_pack()

[Samba.git] / source4 / kdc / authn_policy_util.c

/*
   Unix SMB/CIFS implementation.
   Samba Active Directory authentication policy utility functions

   Copyright (C) Catalyst.Net Ltd 2023

   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 "lib/replace/replace.h"
#include "source4/kdc/authn_policy_util.h"
#include "auth/authn_policy_impl.h"
#include "lib/util/debug.h"
#include "lib/util/samba_util.h"
#include "libcli/security/security.h"
#include "libcli/util/werror.h"
#include "auth/common_auth.h"
#include "source4/auth/session.h"
#include "source4/dsdb/samdb/samdb.h"
#include "source4/dsdb/samdb/ldb_modules/util.h"

bool authn_policy_silos_and_policies_in_effect(struct ldb_context *samdb)
{
        /*
         * Authentication Silos and Authentication Policies are not
         * honoured by Samba unless the DC is at FL 2012 R2.  This is
         * to match Windows, which will offer these features as soon
         * as the DC is upgraded.
         */
        const int functional_level = dsdb_dc_functional_level(samdb);
        return functional_level >= DS_DOMAIN_FUNCTION_2012_R2;
}

bool authn_policy_allowed_ntlm_network_auth_in_effect(struct ldb_context *samdb)
{
        /*
         * The allowed NTLM network authentication Policies are not
         * honoured by Samba unless the DC is at FL2016.  This
         * is to match Windows, which will enforce these restrictions
         * as soon as the DC is upgraded.
         */
        const int functional_level = dsdb_dc_functional_level(samdb);
        return functional_level >= DS_DOMAIN_FUNCTION_2016;
}

/*
 * Depending on the type of the account, we need to refer to different
 * attributes of authentication silo objects. This structure keeps track of the
 * attributes to use for a certain account type.
 */
struct authn_silo_attrs {
        const char *policy;
        const char *attrs[];
};

/*
 * Depending on the type of the account, we need to refer to different
 * attributes of authentication policy objects. This structure keeps track of
 * the attributes to use for a certain account type.
 */
struct authn_policy_attrs {
        /* This applies at FL2016 and up. */
        const char *allowed_ntlm_network_auth;
        /* The remainder apply at FL2012_R2 and up. */
        const char *allowed_to_authenticate_from;
        const char *allowed_to_authenticate_to;
        const char *tgt_lifetime;
        const char *attrs[];
};

struct authn_attrs {
        const struct authn_silo_attrs *silo;
        const struct authn_policy_attrs *policy;
};

/*
 * Get the authentication attributes that apply to an account of a certain
 * class.
 */
static const struct authn_attrs authn_policy_get_attrs(const struct ldb_message *msg)
{
        const struct authn_attrs null_authn_attrs = {
                .silo = NULL,
                .policy = NULL,
        };
        const struct ldb_message_element *objectclass_el = NULL;
        unsigned i;

        objectclass_el = ldb_msg_find_element(msg, "objectClass");
        if (objectclass_el == NULL || objectclass_el->num_values == 0) {
                return null_authn_attrs;
        }

        /*
         * Iterate over the objectClasses, starting at the most-derived class.
         */
        for (i = objectclass_el->num_values; i > 0; --i) {
                const struct ldb_val *objectclass_val = &objectclass_el->values[i - 1];
                const char *objectclass = NULL;

                objectclass = (const char *)objectclass_val->data;
                if (objectclass == NULL) {
                        continue;
                }

#define COMMON_AUTHN_SILO_ATTRS \
        "msDS-AuthNPolicySiloEnforced", \
        "msDS-AuthNPolicySiloMembers", \
        "name"

#define COMMON_AUTHN_POLICY_ATTRS \
        "msDS-AuthNPolicyEnforced", \
        "msDS-StrongNTLMPolicy", \
        "name"

                /*
                 * See which of three classes this object is most closely
                 * derived from.
                 */
                if (strcasecmp(objectclass, "user") == 0) {
                        static const struct authn_silo_attrs user_authn_silo_attrs = {
                                .policy = "msDS-UserAuthNPolicy",
                                .attrs = {
                                        COMMON_AUTHN_SILO_ATTRS,
                                        "msDS-UserAuthNPolicy",
                                        NULL,
                                },
                        };

                        static const struct authn_policy_attrs user_authn_policy_attrs = {
                                .allowed_ntlm_network_auth = "msDS-UserAllowedNTLMNetworkAuthentication",
                                .allowed_to_authenticate_from = "msDS-UserAllowedToAuthenticateFrom",
                                .allowed_to_authenticate_to = "msDS-UserAllowedToAuthenticateTo",
                                .tgt_lifetime = "msDS-UserTGTLifetime",
                                .attrs = {
                                        COMMON_AUTHN_POLICY_ATTRS,
                                        "msDS-UserAllowedNTLMNetworkAuthentication",
                                        "msDS-UserAllowedToAuthenticateFrom",
                                        "msDS-UserAllowedToAuthenticateTo",
                                        "msDS-UserTGTLifetime",
                                        NULL,
                                },
                        };

                        return (struct authn_attrs) {
                                .silo = &user_authn_silo_attrs,
                                .policy = &user_authn_policy_attrs,
                        };
                }

                if (strcasecmp(objectclass, "computer") == 0) {
                        static const struct authn_silo_attrs computer_authn_silo_attrs = {
                                .policy = "msDS-ComputerAuthNPolicy",
                                .attrs = {
                                        COMMON_AUTHN_SILO_ATTRS,
                                        "msDS-ComputerAuthNPolicy",
                                        NULL,
                                },
                        };

                        static const struct authn_policy_attrs computer_authn_policy_attrs = {
                                .allowed_ntlm_network_auth = NULL,
                                .allowed_to_authenticate_from = NULL,
                                .allowed_to_authenticate_to = "msDS-ComputerAllowedToAuthenticateTo",
                                .tgt_lifetime = "msDS-ComputerTGTLifetime",
                                .attrs = {
                                        COMMON_AUTHN_POLICY_ATTRS,
                                        "msDS-ComputerAllowedToAuthenticateTo",
                                        "msDS-ComputerTGTLifetime",
                                        NULL,
                                },
                        };

                        return (struct authn_attrs) {
                                .silo = &computer_authn_silo_attrs,
                                .policy = &computer_authn_policy_attrs,
                        };
                }

                if (strcasecmp(objectclass, "msDS-ManagedServiceAccount") == 0) {
                        static const struct authn_silo_attrs service_authn_silo_attrs = {
                                .policy = "msDS-ServiceAuthNPolicy",
                                .attrs = {
                                        COMMON_AUTHN_SILO_ATTRS,
                                        "msDS-ServiceAuthNPolicy",
                                        NULL,
                                },
                        };

                        static const struct authn_policy_attrs service_authn_policy_attrs = {
                                .allowed_ntlm_network_auth = "msDS-ServiceAllowedNTLMNetworkAuthentication",
                                .allowed_to_authenticate_from = "msDS-ServiceAllowedToAuthenticateFrom",
                                .allowed_to_authenticate_to = "msDS-ServiceAllowedToAuthenticateTo",
                                .tgt_lifetime = "msDS-ServiceTGTLifetime",
                                .attrs = {
                                        COMMON_AUTHN_POLICY_ATTRS,
                                        "msDS-ServiceAllowedNTLMNetworkAuthentication",
                                        "msDS-ServiceAllowedToAuthenticateFrom",
                                        "msDS-ServiceAllowedToAuthenticateTo",
                                        "msDS-ServiceTGTLifetime",
                                        NULL,
                                },
                        };

                        return (struct authn_attrs) {
                                .silo = &service_authn_silo_attrs,
                                .policy = &service_authn_policy_attrs,
                        };
                }
        }

#undef COMMON_AUTHN_SILO_ATTRS
#undef COMMON_AUTHN_POLICY_ATTRS

        /* No match — this object is not a user. */
        return null_authn_attrs;
}

/*
 * Look up the silo assigned to an account. If one exists, returns its details
 * and whether it is enforced or not. ‘silo_attrs’ comprises the attributes to
 * include in the search result, the relevant set of which can differ depending
 * on the account’s objectClass.
 */
int authn_policy_get_assigned_silo(struct ldb_context *samdb,
                                   TALLOC_CTX *mem_ctx,
                                   const struct ldb_message *msg,
                                   const char * const *silo_attrs,
                                   const struct ldb_message **silo_msg_out,
                                   bool *is_enforced)
{
        TALLOC_CTX *tmp_ctx = NULL;
        int ret = 0;
        const struct ldb_message_element *authn_silo = NULL;
        struct ldb_dn *authn_silo_dn = NULL;
        struct ldb_message *authn_silo_msg = NULL;
        const struct ldb_message_element *members = NULL;
        const char *linearized_dn = NULL;
        struct ldb_val linearized_dn_val;

        *silo_msg_out = NULL;
        *is_enforced = true;

        if (!authn_policy_silos_and_policies_in_effect(samdb)) {
                return 0;
        }

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                ret = ENOMEM;
                goto out;
        }

        authn_silo = ldb_msg_find_element(msg, "msDS-AssignedAuthNPolicySilo");
        /* Is the account assigned to a silo? */
        if (authn_silo == NULL || !authn_silo->num_values) {
                goto out;
        }

        authn_silo_dn = ldb_dn_from_ldb_val(tmp_ctx, samdb, &authn_silo->values[0]);
        if (authn_silo_dn == NULL) {
                ret = ENOMEM;
                goto out;
        }

        ret = dsdb_search_one(samdb,
                              tmp_ctx,
                              &authn_silo_msg,
                              authn_silo_dn,
                              LDB_SCOPE_BASE,
                              silo_attrs,
                              0, NULL);
        if (ret == LDB_ERR_NO_SUCH_OBJECT) {
                /* Not found. */
                ret = 0;
                goto out;
        }
        if (ret) {
                goto out;
        }

        members = ldb_msg_find_element(authn_silo_msg,
                                       "msDS-AuthNPolicySiloMembers");
        if (members == NULL) {
                goto out;
        }

        linearized_dn = ldb_dn_get_linearized(msg->dn);
        if (linearized_dn == NULL) {
                ret = ENOMEM;
                goto out;
        }

        linearized_dn_val = data_blob_string_const(linearized_dn);
        /* Is the account a member of the silo? */
        if (!ldb_msg_find_val(members, &linearized_dn_val)) {
                goto out;
        }

        /* Is the silo actually enforced? */
        *is_enforced = ldb_msg_find_attr_as_bool(
                authn_silo_msg,
                "msDS-AuthNPolicySiloEnforced",
                false);

        *silo_msg_out = talloc_move(mem_ctx, &authn_silo_msg);

out:
        talloc_free(tmp_ctx);
        return ret;
}

/*
 * Look up the authentication policy assigned to an account, returning its
 * details if it exists. ‘authn_attrs’ specifies which attributes are relevant,
 * and should be chosen based on the account’s objectClass.
 */
static int samba_kdc_authn_policy_msg(struct ldb_context *samdb,
                                      TALLOC_CTX *mem_ctx,
                                      const struct ldb_message *msg,
                                      const struct authn_attrs authn_attrs,
                                      struct ldb_message **authn_policy_msg_out,
                                      struct authn_policy *authn_policy_out)
{
        TALLOC_CTX *tmp_ctx = NULL;
        int ret = 0;
        const struct ldb_message *authn_silo_msg = NULL;
        const struct ldb_message_element *authn_policy = NULL;
        const char *silo_name = NULL;
        const char *policy_name = NULL;
        struct ldb_dn *authn_policy_dn = NULL;
        struct ldb_message *authn_policy_msg = NULL;
        bool belongs_to_silo = false;
        bool is_enforced = true;

        *authn_policy_msg_out = NULL;
        *authn_policy_out = (struct authn_policy) {};

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                ret = ENOMEM;
                goto out;
        }

        /* See whether the account is assigned to a silo. */
        ret = authn_policy_get_assigned_silo(samdb,
                                             tmp_ctx,
                                             msg,
                                             authn_attrs.silo->attrs,
                                             &authn_silo_msg,
                                             &is_enforced);
        if (ret) {
                goto out;
        }

        if (authn_silo_msg != NULL) {
                belongs_to_silo = true;

                silo_name = ldb_msg_find_attr_as_string(authn_silo_msg, "name", NULL);

                /* Get the applicable authentication policy. */
                authn_policy = ldb_msg_find_element(
                        authn_silo_msg,
                        authn_attrs.silo->policy);
        } else {
                /*
                 * If no silo is assigned, take the policy that is directly
                 * assigned to the account.
                 */
                authn_policy = ldb_msg_find_element(msg, "msDS-AssignedAuthNPolicy");
        }

        if (authn_policy == NULL || !authn_policy->num_values) {
                /* No policy applies; we’re done. */
                goto out;
        }

        authn_policy_dn = ldb_dn_from_ldb_val(tmp_ctx, samdb, &authn_policy->values[0]);
        if (authn_policy_dn == NULL) {
                ret = ENOMEM;
                goto out;
        }

        /* Look up the policy object. */
        ret = dsdb_search_one(samdb,
                              tmp_ctx,
                              &authn_policy_msg,
                              authn_policy_dn,
                              LDB_SCOPE_BASE,
                              authn_attrs.policy->attrs,
                              0, NULL);
        if (ret == LDB_ERR_NO_SUCH_OBJECT) {
                /* Not found. */
                ret = 0;
                goto out;
        }
        if (ret) {
                goto out;
        }

        policy_name = ldb_msg_find_attr_as_string(authn_policy_msg, "name", NULL);

        if (!belongs_to_silo) {
                is_enforced = ldb_msg_find_attr_as_bool(
                        authn_policy_msg,
                        "msDS-AuthNPolicyEnforced",
                        false);
        }

        authn_policy_out->silo_name = talloc_move(mem_ctx, &silo_name);
        authn_policy_out->policy_name = talloc_move(mem_ctx, &policy_name);
        authn_policy_out->enforced = is_enforced;

        *authn_policy_msg_out = talloc_move(mem_ctx, &authn_policy_msg);

out:
        talloc_free(tmp_ctx);
        return ret;
}

/*
 * Reference an existing authentication policy onto a talloc context, returning
 * ‘true’ on success.
 */
static bool authn_policy_ref(TALLOC_CTX *mem_ctx,
                             struct authn_policy *policy_out,
                             const struct authn_policy *policy)
{
        const char *silo_name = NULL;
        const char *policy_name = NULL;

        if (policy->silo_name != NULL) {
                silo_name = talloc_strdup(mem_ctx, policy->silo_name);
                if (silo_name == NULL) {
                        return false;
                }
        }

        if (policy->policy_name != NULL) {
                policy_name = talloc_strdup(mem_ctx, policy->policy_name);
                if (policy_name == NULL) {
                        /*
                         * We can’t free ‘silo_name’ here, as it is declared
                         * const. It will be freed with the parent context.
                         */
                        return false;
                }
        }

        *policy_out = (struct authn_policy) {
                .silo_name = silo_name,
                .policy_name = policy_name,
                .enforced = policy->enforced,
        };

        return true;
}

/* Create a structure containing auditing information. */
static NTSTATUS _authn_policy_audit_info(TALLOC_CTX *mem_ctx,
                                         const struct authn_policy *policy,
                                         const struct authn_int64_optional tgt_lifetime_raw,
                                         const struct auth_user_info_dc *client_info,
                                         const enum authn_audit_event event,
                                         const enum authn_audit_reason reason,
                                         const NTSTATUS policy_status,
                                         const char *location,
                                         struct authn_audit_info **audit_info_out)
{
        struct authn_audit_info *audit_info = NULL;
        bool ok;

        if (audit_info_out == NULL) {
                return NT_STATUS_OK;
        }

        audit_info = talloc_zero(mem_ctx, struct authn_audit_info);
        if (audit_info == NULL) {
                return NT_STATUS_NO_MEMORY;
        }

        if (client_info != NULL) {
                /*
                 * Keep a reference to the client’s user information so that it
                 * is available to be logged later.
                 */
                audit_info->client_info = talloc_reference(audit_info, client_info);
                if (audit_info->client_info == NULL) {
                        talloc_free(audit_info);
                        return NT_STATUS_NO_MEMORY;
                }
        }

        if (policy != NULL) {
                audit_info->policy = talloc_zero(audit_info, struct authn_policy);
                if (audit_info->policy == NULL) {
                        talloc_free(audit_info);
                        return NT_STATUS_NO_MEMORY;
                }

                ok = authn_policy_ref(audit_info, audit_info->policy, policy);
                if (!ok) {
                        talloc_free(audit_info);
                        return NT_STATUS_NO_MEMORY;
                }
        }

        audit_info->event = event;
        audit_info->reason = reason;
        audit_info->policy_status = policy_status;
        audit_info->location = location;
        audit_info->tgt_lifetime_raw = tgt_lifetime_raw;

        *audit_info_out = audit_info;
        return NT_STATUS_OK;
}

/* Create a structure containing auditing information. */
#define authn_policy_audit_info( \
        mem_ctx, \
        policy, \
        tgt_lifetime_raw, \
        client_info, \
        event, \
        reason, \
        policy_status, \
        audit_info_out) \
        _authn_policy_audit_info( \
                mem_ctx, \
                policy, \
                tgt_lifetime_raw, \
                client_info, \
                event, \
                reason, \
                policy_status, \
                __location__, \
                audit_info_out)

/*
 * Perform an access check against the security descriptor set in an
 * authentication policy. ‘client_info’ must be talloc-allocated so that we can
 * make a reference to it.
 */
static NTSTATUS _authn_policy_access_check(TALLOC_CTX *mem_ctx,
                                           struct ldb_context *samdb,
                                           struct loadparm_context* lp_ctx,
                                           const struct auth_user_info_dc *client_info,
                                           const struct authn_policy *policy,
                                           const struct authn_int64_optional tgt_lifetime_raw,
                                           const enum authn_audit_event restriction_event,
                                           const DATA_BLOB *descriptor_blob,
                                           const char *location,
                                           struct authn_audit_info **audit_info_out)
{
        TALLOC_CTX *tmp_ctx = NULL;
        NTSTATUS status = NT_STATUS_OK;
        NTSTATUS status2;
        enum ndr_err_code ndr_err;
        struct security_descriptor *descriptor = NULL;
        struct security_token *security_token = NULL;
        uint32_t session_info_flags =
                AUTH_SESSION_INFO_DEFAULT_GROUPS |
                AUTH_SESSION_INFO_SIMPLE_PRIVILEGES;
        const uint32_t access_desired = SEC_ADS_CONTROL_ACCESS;
        uint32_t access_granted;
        enum authn_audit_event event = restriction_event;
        enum authn_audit_reason reason = AUTHN_AUDIT_REASON_NONE;

        if (audit_info_out != NULL) {
                *audit_info_out = NULL;
        }

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                status = NT_STATUS_NO_MEMORY;
                goto out;
        }

        if (!(client_info->info->user_flags & NETLOGON_GUEST)) {
                session_info_flags |= AUTH_SESSION_INFO_AUTHENTICATED;
        }

        descriptor = talloc(tmp_ctx, struct security_descriptor);
        if (descriptor == NULL) {
                status = NT_STATUS_NO_MEMORY;
                goto out;
        }

        ndr_err = ndr_pull_struct_blob(descriptor_blob,
                                       tmp_ctx,
                                       descriptor,
                                       (ndr_pull_flags_fn_t)ndr_pull_security_descriptor);
        if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
                status = ndr_map_error2ntstatus(ndr_err);
                DBG_ERR("Failed to unmarshall "
                        "security descriptor for authentication policy: %s\n",
                        nt_errstr(status));
                reason = AUTHN_AUDIT_REASON_DESCRIPTOR_INVALID;
                goto out;
        }

        /* Require that the security descriptor has an owner set. */
        if (descriptor->owner_sid == NULL) {
                status = NT_STATUS_INVALID_PARAMETER;
                reason = AUTHN_AUDIT_REASON_DESCRIPTOR_NO_OWNER;
                goto out;
        }

        status = auth_generate_security_token(tmp_ctx,
                                               lp_ctx,
                                               samdb,
                                               client_info,
                                               session_info_flags,
                                               &security_token);
        if (!NT_STATUS_IS_OK(status)) {
                reason = AUTHN_AUDIT_REASON_SECURITY_TOKEN_FAILURE;
                goto out;
        }

        status = sec_access_check_ds(descriptor, security_token,
                                        access_desired, &access_granted,
                                        NULL, NULL);
        if (NT_STATUS_EQUAL(status, NT_STATUS_ACCESS_DENIED)) {
                status = NT_STATUS_AUTHENTICATION_FIREWALL_FAILED;
                reason = AUTHN_AUDIT_REASON_ACCESS_DENIED;
                goto out;
        }
        if (!NT_STATUS_IS_OK(status)) {
                goto out;
        }

        event = AUTHN_AUDIT_EVENT_OK;
out:
        /*
         * Create the structure with auditing information here while we have all
         * the relevant information to hand. It will contain references to
         * information regarding the client and the policy, to be consulted
         * after the referents have possibly been freed.
         */
        status2 = _authn_policy_audit_info(mem_ctx,
                                           policy,
                                           tgt_lifetime_raw,
                                           client_info,
                                           event,
                                           reason,
                                           status,
                                           location,
                                           audit_info_out);
        if (!NT_STATUS_IS_OK(status2)) {
                status = status2;
        } else if (!authn_policy_is_enforced(policy)) {
                status = NT_STATUS_OK;
        }

        talloc_free(tmp_ctx);
        return status;
}

#define authn_policy_access_check(mem_ctx, \
        samdb, \
        lp_ctx, \
        client_info, \
        policy, \
        tgt_lifetime_raw, \
        restriction_event, \
        descriptor_blob, \
        audit_info_out) \
        _authn_policy_access_check(mem_ctx, \
                samdb, \
                lp_ctx, \
                client_info, \
                policy, \
                tgt_lifetime_raw, \
                restriction_event, \
                descriptor_blob, \
                __location__, \
                audit_info_out)

/* Return an authentication policy moved onto a talloc context. */
static struct authn_policy authn_policy_move(TALLOC_CTX *mem_ctx,
                                             struct authn_policy *policy)
{
        return (struct authn_policy) {
                .silo_name = talloc_move(mem_ctx, &policy->silo_name),
                .policy_name = talloc_move(mem_ctx, &policy->policy_name),
                .enforced = policy->enforced,
        };
}

/* Authentication policies for Kerberos clients. */

/*
 * Get the applicable authentication policy for an account acting as a Kerberos
 * client.
 */
int authn_policy_kerberos_client(struct ldb_context *samdb,
                                 TALLOC_CTX *mem_ctx,
                                 const struct ldb_message *msg,
                                 const struct authn_kerberos_client_policy **policy_out)
{
        TALLOC_CTX *tmp_ctx = NULL;
        int ret = 0;
        struct authn_attrs authn_attrs;
        struct ldb_message *authn_policy_msg = NULL;
        struct authn_kerberos_client_policy *client_policy = NULL;
        struct authn_policy policy;

        *policy_out = NULL;

        if (!authn_policy_silos_and_policies_in_effect(samdb)) {
                return 0;
        }

        /*
         * Get the silo and policy attributes that apply to objects of this
         * account’s objectclass.
         */
        authn_attrs = authn_policy_get_attrs(msg);
        if (authn_attrs.silo == NULL || authn_attrs.policy == NULL) {
                /*
                 * No applicable silo or policy attributes (somehow). Either
                 * this account isn’t derived from ‘user’, or the message is
                 * missing an objectClass element.
                 */
                goto out;
        }

        if (authn_attrs.policy->allowed_to_authenticate_from == NULL &&
            authn_attrs.policy->tgt_lifetime == NULL)
        {
                /* No relevant policy attributes apply. */
                goto out;
        }

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                ret = ENOMEM;
                goto out;
        }

        ret = samba_kdc_authn_policy_msg(samdb,
                                         tmp_ctx,
                                         msg,
                                         authn_attrs,
                                         &authn_policy_msg,
                                         &policy);
        if (ret) {
                goto out;
        }

        if (authn_policy_msg == NULL) {
                /* No policy applies. */
                goto out;
        }

        client_policy = talloc_zero(tmp_ctx, struct authn_kerberos_client_policy);
        if (client_policy == NULL) {
                ret = ENOMEM;
                goto out;
        }

        client_policy->policy = authn_policy_move(client_policy, &policy);

        if (authn_attrs.policy->allowed_to_authenticate_from != NULL) {
                const struct ldb_val *allowed_from = ldb_msg_find_ldb_val(
                        authn_policy_msg,
                        authn_attrs.policy->allowed_to_authenticate_from);

                if (allowed_from != NULL && allowed_from->data != NULL) {
                        client_policy->allowed_to_authenticate_from = data_blob_const(
                                talloc_steal(client_policy, allowed_from->data),
                                allowed_from->length);
                }
        }

        if (authn_attrs.policy->tgt_lifetime != NULL) {
                client_policy->tgt_lifetime_raw = ldb_msg_find_attr_as_int64(
                        authn_policy_msg,
                        authn_attrs.policy->tgt_lifetime,
                        0);
        }

        *policy_out = talloc_move(mem_ctx, &client_policy);

out:
        talloc_free(tmp_ctx);
        return ret;
}

/* Get device restrictions enforced by an authentication policy. */
static const DATA_BLOB *authn_policy_kerberos_device_restrictions(const struct authn_kerberos_client_policy *policy)
{
        const DATA_BLOB *restrictions = NULL;

        if (policy == NULL) {
                return NULL;
        }

        restrictions = &policy->allowed_to_authenticate_from;
        if (restrictions->data == NULL) {
                return NULL;
        }

        return restrictions;
}

/* Return whether an authentication policy enforces device restrictions. */
bool authn_policy_device_restrictions_present(const struct authn_kerberos_client_policy *policy)
{
        return authn_policy_kerberos_device_restrictions(policy) != NULL;
}

/*
 * Perform an access check for the device with which the client is
 * authenticating. ‘device_info’ must be talloc-allocated so that we can make a
 * reference to it.
 */
NTSTATUS authn_policy_authenticate_from_device(TALLOC_CTX *mem_ctx,
                                               struct ldb_context *samdb,
                                               struct loadparm_context* lp_ctx,
                                               const struct auth_user_info_dc *device_info,
                                               const struct authn_kerberos_client_policy *client_policy,
                                               struct authn_audit_info **client_audit_info_out)
{
        NTSTATUS status = NT_STATUS_OK;
        const DATA_BLOB *restrictions = NULL;

        restrictions = authn_policy_kerberos_device_restrictions(client_policy);
        if (restrictions == NULL) {
                goto out;
        }

        status = authn_policy_access_check(mem_ctx,
                                           samdb,
                                           lp_ctx,
                                           device_info,
                                           &client_policy->policy,
                                           authn_int64_some(client_policy->tgt_lifetime_raw),
                                           AUTHN_AUDIT_EVENT_KERBEROS_DEVICE_RESTRICTION,
                                           restrictions,
                                           client_audit_info_out);
out:
        return status;
}

/* Authentication policies for NTLM clients. */

/*
 * Get the applicable authentication policy for an account acting as an NTLM
 * client.
 */
int authn_policy_ntlm_client(struct ldb_context *samdb,
                             TALLOC_CTX *mem_ctx,
                             const struct ldb_message *msg,
                             const struct authn_ntlm_client_policy **policy_out)
{
        TALLOC_CTX *tmp_ctx = NULL;
        int ret = 0;
        struct authn_attrs authn_attrs;
        struct ldb_message *authn_policy_msg = NULL;
        struct authn_ntlm_client_policy *client_policy = NULL;
        struct authn_policy policy;

        *policy_out = NULL;

        if (!authn_policy_silos_and_policies_in_effect(samdb)) {
                return 0;
        }

        /*
         * Get the silo and policy attributes that apply to objects of this
         * account’s objectclass.
         */
        authn_attrs = authn_policy_get_attrs(msg);
        if (authn_attrs.silo == NULL || authn_attrs.policy == NULL) {
                /*
                 * No applicable silo or policy attributes (somehow). Either
                 * this account isn’t derived from ‘user’, or the message is
                 * missing an objectClass element.
                 */
                goto out;
        }

        if (authn_attrs.policy->allowed_to_authenticate_from == NULL &&
            authn_attrs.policy->allowed_ntlm_network_auth == NULL)
        {
                /* No relevant policy attributes apply. */
                goto out;
        }

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                ret = ENOMEM;
                goto out;
        }

        ret = samba_kdc_authn_policy_msg(samdb,
                                         tmp_ctx,
                                         msg,
                                         authn_attrs,
                                         &authn_policy_msg,
                                         &policy);
        if (ret) {
                goto out;
        }

        if (authn_policy_msg == NULL) {
                /* No policy applies. */
                goto out;
        }

        client_policy = talloc_zero(tmp_ctx, struct authn_ntlm_client_policy);
        if (client_policy == NULL) {
                ret = ENOMEM;
                goto out;
        }

        client_policy->policy = authn_policy_move(client_policy, &policy);

        if (authn_attrs.policy->allowed_to_authenticate_from != NULL) {
                const struct ldb_val *allowed_from = ldb_msg_find_ldb_val(
                        authn_policy_msg,
                        authn_attrs.policy->allowed_to_authenticate_from);

                if (allowed_from != NULL && allowed_from->data != NULL) {
                        client_policy->allowed_to_authenticate_from = data_blob_const(
                                talloc_steal(client_policy, allowed_from->data),
                                allowed_from->length);
                }
        }

        if (authn_attrs.policy->allowed_ntlm_network_auth != NULL &&
            authn_policy_allowed_ntlm_network_auth_in_effect(samdb))
        {
                client_policy->allowed_ntlm_network_auth = ldb_msg_find_attr_as_bool(
                        authn_policy_msg,
                        authn_attrs.policy->allowed_ntlm_network_auth,
                        false);
        }

        *policy_out = talloc_move(mem_ctx, &client_policy);

out:
        talloc_free(tmp_ctx);
        return ret;
}

/* Return whether an authentication policy enforces device restrictions. */
static bool authn_policy_ntlm_device_restrictions_present(const struct authn_ntlm_client_policy *policy)
{
        if (policy == NULL) {
                return false;
        }

        return policy->allowed_to_authenticate_from.data != NULL;
}

/* Check whether the client is allowed to authenticate using NTLM. */
NTSTATUS authn_policy_ntlm_apply_device_restriction(TALLOC_CTX *mem_ctx,
                                                    const struct authn_ntlm_client_policy *client_policy,
                                                    struct authn_audit_info **client_audit_info_out)
{
        NTSTATUS status;
        NTSTATUS status2;

        if (client_audit_info_out != NULL) {
                *client_audit_info_out = NULL;
        }

        if (client_policy == NULL) {
                return NT_STATUS_OK;
        }

        /*
         * Access control restrictions cannot be applied to NTLM.
         *
         * If NTLM authentication is disallowed and the policy enforces a device
         * restriction, deny the authentication.
         */

        if (!authn_policy_ntlm_device_restrictions_present(client_policy)) {
                return authn_policy_audit_info(mem_ctx,
                                               &client_policy->policy,
                                               authn_int64_none() /* tgt_lifetime_raw */,
                                               NULL /* client_info */,
                                               AUTHN_AUDIT_EVENT_OK,
                                               AUTHN_AUDIT_REASON_NONE,
                                               NT_STATUS_OK,
                                               client_audit_info_out);
        }

        /*
         * (Although MS-APDS doesn’t state it, AllowedNTLMNetworkAuthentication
         * applies to interactive logons too.)
         */
        if (client_policy->allowed_ntlm_network_auth) {
                return authn_policy_audit_info(mem_ctx,
                                               &client_policy->policy,
                                               authn_int64_none() /* tgt_lifetime_raw */,
                                               NULL /* client_info */,
                                               AUTHN_AUDIT_EVENT_OK,
                                               AUTHN_AUDIT_REASON_NONE,
                                               NT_STATUS_OK,
                                               client_audit_info_out);
        }

        status = NT_STATUS_ACCOUNT_RESTRICTION;
        status2 = authn_policy_audit_info(mem_ctx,
                                          &client_policy->policy,
                                          authn_int64_none() /* tgt_lifetime_raw */,
                                          NULL /* client_info */,
                                          AUTHN_AUDIT_EVENT_NTLM_DEVICE_RESTRICTION,
                                          AUTHN_AUDIT_REASON_NONE,
                                          status,
                                          client_audit_info_out);
        if (!NT_STATUS_IS_OK(status2)) {
                status = status2;
        } else if (!authn_policy_is_enforced(&client_policy->policy)) {
                status = NT_STATUS_OK;
        }

        return status;
}

/* Authentication policies for servers. */

/*
 * Get the applicable authentication policy for an account acting as a
 * server.
 */
int authn_policy_server(struct ldb_context *samdb,
                        TALLOC_CTX *mem_ctx,
                        const struct ldb_message *msg,
                        const struct authn_server_policy **policy_out)
{
        TALLOC_CTX *tmp_ctx = NULL;
        int ret = 0;
        struct authn_attrs authn_attrs;
        struct ldb_message *authn_policy_msg = NULL;
        struct authn_server_policy *server_policy = NULL;
        struct authn_policy policy;

        *policy_out = NULL;

        if (!authn_policy_silos_and_policies_in_effect(samdb)) {
                return 0;
        }

        /*
         * Get the silo and policy attributes that apply to objects of this
         * account’s objectclass.
         */
        authn_attrs = authn_policy_get_attrs(msg);
        if (authn_attrs.silo == NULL || authn_attrs.policy == NULL) {
                /*
                 * No applicable silo or policy attributes (somehow). Either
                 * this account isn’t derived from ‘user’, or the message is
                 * missing an objectClass element.
                 */
                goto out;
        }

        if (authn_attrs.policy->allowed_to_authenticate_to == NULL) {
                /* The relevant policy attribute doesn’t apply. */
                goto out;
        }

        tmp_ctx = talloc_new(mem_ctx);
        if (tmp_ctx == NULL) {
                ret = ENOMEM;
                goto out;
        }

        ret = samba_kdc_authn_policy_msg(samdb,
                                         tmp_ctx,
                                         msg,
                                         authn_attrs,
                                         &authn_policy_msg,
                                         &policy);
        if (ret) {
                goto out;
        }

        if (authn_policy_msg == NULL) {
                /* No policy applies. */
                goto out;
        }

        server_policy = talloc_zero(tmp_ctx, struct authn_server_policy);
        if (server_policy == NULL) {
                ret = ENOMEM;
                goto out;
        }

        server_policy->policy = authn_policy_move(server_policy, &policy);

        if (authn_attrs.policy->allowed_to_authenticate_to != NULL) {
                const struct ldb_val *allowed_to = ldb_msg_find_ldb_val(
                        authn_policy_msg,
                        authn_attrs.policy->allowed_to_authenticate_to);

                if (allowed_to != NULL && allowed_to->data != NULL) {
                        server_policy->allowed_to_authenticate_to = data_blob_const(
                                talloc_steal(server_policy, allowed_to->data),
                                allowed_to->length);
                }
        }

        *policy_out = talloc_move(mem_ctx, &server_policy);

out:
        talloc_free(tmp_ctx);
        return ret;
}

/* Get restrictions enforced by an authentication policy. */
static const DATA_BLOB *authn_policy_restrictions(const struct authn_server_policy *policy)
{
        const DATA_BLOB *restrictions = NULL;

        if (policy == NULL) {
                return NULL;
        }

        restrictions = &policy->allowed_to_authenticate_to;
        if (restrictions->data == NULL) {
                return NULL;
        }

        return restrictions;
}

/* Return whether an authentication policy enforces restrictions. */
bool authn_policy_restrictions_present(const struct authn_server_policy *policy)
{
        return authn_policy_restrictions(policy) != NULL;
}

/*
 * Perform an access check for the client attempting to authenticate to the
 * server. ‘user_info’ must be talloc-allocated so that we can make a reference
 * to it.
 */
NTSTATUS authn_policy_authenticate_to_service(TALLOC_CTX *mem_ctx,
                                              struct ldb_context *samdb,
                                              struct loadparm_context* lp_ctx,
                                              const enum authn_policy_auth_type auth_type,
                                              const struct auth_user_info_dc *user_info,
                                              const struct authn_server_policy *server_policy,
                                              struct authn_audit_info **server_audit_info_out)
{
        NTSTATUS status = NT_STATUS_OK;
        const DATA_BLOB *restrictions = NULL;
        enum authn_audit_event event;

        restrictions = authn_policy_restrictions(server_policy);
        if (restrictions == NULL) {
                return authn_server_policy_audit_info(mem_ctx,
                                                      server_policy,
                                                      user_info,
                                                      AUTHN_AUDIT_EVENT_OK,
                                                      AUTHN_AUDIT_REASON_NONE,
                                                      NT_STATUS_OK,
                                                      server_audit_info_out);
        }

        switch (auth_type) {
        case AUTHN_POLICY_AUTH_TYPE_KERBEROS:
                event = AUTHN_AUDIT_EVENT_KERBEROS_SERVER_RESTRICTION;
                break;
        case AUTHN_POLICY_AUTH_TYPE_NTLM:
                event = AUTHN_AUDIT_EVENT_NTLM_SERVER_RESTRICTION;
                break;
        default:
                return NT_STATUS_INVALID_PARAMETER_4;
        }

        status = authn_policy_access_check(mem_ctx,
                                           samdb,
                                           lp_ctx,
                                           user_info,
                                           &server_policy->policy,
                                           authn_int64_none() /* tgt_lifetime_raw */,
                                           event,
                                           restrictions,
                                           server_audit_info_out);
        return status;
}

/* Create a structure containing auditing information. */
NTSTATUS _authn_kerberos_client_policy_audit_info(
        TALLOC_CTX *mem_ctx,
        const struct authn_kerberos_client_policy *client_policy,
        const struct auth_user_info_dc *client_info,
        const enum authn_audit_event event,
        const enum authn_audit_reason reason,
        const NTSTATUS policy_status,
        const char *location,
        struct authn_audit_info **audit_info_out)
{
        const struct authn_policy *policy = NULL;
        struct authn_int64_optional tgt_lifetime_raw = authn_int64_none();

        if (client_policy != NULL) {
                policy = &client_policy->policy;
                tgt_lifetime_raw = authn_int64_some(client_policy->tgt_lifetime_raw);
        }

        return _authn_policy_audit_info(mem_ctx,
                                        policy,
                                        tgt_lifetime_raw,
                                        client_info,
                                        event,
                                        reason,
                                        policy_status,
                                        location,
                                        audit_info_out);
}

/* Create a structure containing auditing information. */
NTSTATUS _authn_ntlm_client_policy_audit_info(
        TALLOC_CTX *mem_ctx,
        const struct authn_ntlm_client_policy *client_policy,
        const struct auth_user_info_dc *client_info,
        const enum authn_audit_event event,
        const enum authn_audit_reason reason,
        const NTSTATUS policy_status,
        const char *location,
        struct authn_audit_info **audit_info_out)
{
        const struct authn_policy *policy = NULL;

        if (client_policy != NULL) {
                policy = &client_policy->policy;
        }

        return _authn_policy_audit_info(mem_ctx,
                                        policy,
                                        authn_int64_none() /* tgt_lifetime_raw */,
                                        client_info,
                                        event,
                                        reason,
                                        policy_status,
                                        location,
                                        audit_info_out);
}

/* Create a structure containing auditing information. */
NTSTATUS _authn_server_policy_audit_info(
        TALLOC_CTX *mem_ctx,
        const struct authn_server_policy *server_policy,
        const struct auth_user_info_dc *client_info,
        const enum authn_audit_event event,
        const enum authn_audit_reason reason,
        const NTSTATUS policy_status,
        const char *location,
        struct authn_audit_info **audit_info_out)
{
        const struct authn_policy *policy = NULL;

        if (server_policy != NULL) {
                policy = &server_policy->policy;
        }

        return _authn_policy_audit_info(mem_ctx,
                                        policy,
                                        authn_int64_none() /* tgt_lifetime_raw */,
                                        client_info,
                                        event,
                                        reason,
                                        policy_status,
                                        location,
                                        audit_info_out);
}