kdc/kx509.c

   1 /*
   2  * Copyright (c) 2006 - 2007 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include "kdc_locl.h"
  35 #include <hex.h>
  36 #include <rfc2459_asn1.h>
  37 #include <hx509.h>
  38
  39 #ifdef KX509
  40
  41 /*
  42  *
  43  */
  44
  45 krb5_error_code
  46 _kdc_try_kx509_request(void *ptr, size_t len, struct Kx509Request *req, size_t *size)
  47 {
  48     if (len < 4)
  49         return -1;
  50     if (memcmp("\x00\x00\x02\x00", ptr, 4) != 0)
  51         return -1;
  52     return decode_Kx509Request(((unsigned char *)ptr) + 4, len - 4, req, size);
  53 }
  54
  55 /*
  56  *
  57  */
  58
  59 static const unsigned char version_2_0[4] = {0 , 0, 2, 0};
  60
  61 static krb5_error_code
  62 verify_req_hash(krb5_context context,
  63                 const Kx509Request *req,
  64                 krb5_keyblock *key)
  65 {
  66     unsigned char digest[SHA_DIGEST_LENGTH];
  67     HMAC_CTX ctx;
  68
  69     if (req->pk_hash.length != sizeof(digest)) {
  70         krb5_set_error_message(context, KRB5KDC_ERR_PREAUTH_FAILED,
  71                                "pk-hash have wrong length: %lu",
  72                                (unsigned long)req->pk_hash.length);
  73         return KRB5KDC_ERR_PREAUTH_FAILED;
  74     }
  75
  76     HMAC_CTX_init(&ctx);
  77     HMAC_Init_ex(&ctx,
  78                  key->keyvalue.data, key->keyvalue.length,
  79                  EVP_sha1(), NULL);
  80     if (sizeof(digest) != HMAC_size(&ctx))
  81         krb5_abortx(context, "runtime error, hmac buffer wrong size in kx509");
  82     HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
  83     HMAC_Update(&ctx, req->pk_key.data, req->pk_key.length);
  84     HMAC_Final(&ctx, digest, 0);
  85     HMAC_CTX_cleanup(&ctx);
  86
  87     if (memcmp(req->pk_hash.data, digest, sizeof(digest)) != 0) {
  88         krb5_set_error_message(context, KRB5KDC_ERR_PREAUTH_FAILED,
  89                                "pk-hash is not correct");
  90         return KRB5KDC_ERR_PREAUTH_FAILED;
  91     }
  92     return 0;
  93 }
  94
  95 static krb5_error_code
  96 calculate_reply_hash(krb5_context context,
  97                      krb5_keyblock *key,
  98                      Kx509Response *rep)
  99 {
 100     krb5_error_code ret;
 101     HMAC_CTX ctx;
 102
 103     HMAC_CTX_init(&ctx);
 104
 105     HMAC_Init_ex(&ctx, key->keyvalue.data, key->keyvalue.length,
 106                  EVP_sha1(), NULL);
 107     ret = krb5_data_alloc(rep->hash, HMAC_size(&ctx));
 108     if (ret) {
 109         HMAC_CTX_cleanup(&ctx);
 110         krb5_set_error_message(context, ENOMEM, "malloc: out of memory");
 111         return ENOMEM;
 112     }
 113
 114     HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
 115     if (rep->error_code) {
 116         int32_t t = *rep->error_code;
 117         do {
 118             unsigned char p = (t & 0xff);
 119             HMAC_Update(&ctx, &p, 1);
 120             t >>= 8;
 121         } while (t);
 122     }
 123     if (rep->certificate)
 124         HMAC_Update(&ctx, rep->certificate->data, rep->certificate->length);
 125     if (rep->e_text)
 126         HMAC_Update(&ctx, (unsigned char *)*rep->e_text, strlen(*rep->e_text));
 127
 128     HMAC_Final(&ctx, rep->hash->data, 0);
 129     HMAC_CTX_cleanup(&ctx);
 130
 131     return 0;
 132 }
 133
 134 /*
 135  * Build a certifate for `principal´ that will expire at `endtime´.
 136  */
 137
 138 static krb5_error_code
 139 build_certificate(krb5_context context,
 140                   krb5_kdc_configuration *config,
 141                   const krb5_data *key,
 142                   time_t endtime,
 143                   krb5_principal principal,
 144                   krb5_data *certificate)
 145 {
 146     hx509_ca_tbs tbs = NULL;
 147     hx509_env env = NULL;
 148     hx509_cert cert = NULL;
 149     hx509_cert signer = NULL;
 150     int ret;
 151
 152     if (krb5_principal_get_comp_string(context, principal, 1) != NULL) {
 153         kdc_log(context, config, 0, "Principal is not a user");
 154         return EINVAL;
 155     }
 156
 157     ret = hx509_env_add(context->hx509ctx, &env, "principal-name",
 158                         krb5_principal_get_comp_string(context, principal, 0));
 159     if (ret)
 160         goto out;
 161
 162     {
 163         hx509_certs certs;
 164         hx509_query *q;
 165
 166         ret = hx509_certs_init(context->hx509ctx, config->kx509_ca, 0,
 167                                NULL, &certs);
 168         if (ret) {
 169             kdc_log(context, config, 0, "Failed to load CA %s",
 170                     config->kx509_ca);
 171             goto out;
 172         }
 173         ret = hx509_query_alloc(context->hx509ctx, &q);
 174         if (ret) {
 175             hx509_certs_free(&certs);
 176             goto out;
 177         }
 178
 179         hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
 180         hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
 181
 182         ret = hx509_certs_find(context->hx509ctx, certs, q, &signer);
 183         hx509_query_free(context->hx509ctx, q);
 184         hx509_certs_free(&certs);
 185         if (ret) {
 186             kdc_log(context, config, 0, "Failed to find a CA in %s",
 187                     config->kx509_ca);
 188             goto out;
 189         }
 190     }
 191
 192     ret = hx509_ca_tbs_init(context->hx509ctx, &tbs);
 193     if (ret)
 194         goto out;
 195
 196     {
 197         SubjectPublicKeyInfo spki;
 198         heim_any any;
 199
 200         memset(&spki, 0, sizeof(spki));
 201
 202         spki.subjectPublicKey.data = key->data;
 203         spki.subjectPublicKey.length = key->length * 8;
 204
 205         ret = der_copy_oid(&asn1_oid_id_pkcs1_rsaEncryption,
 206                            &spki.algorithm.algorithm);
 207
 208         any.data = "\x05\x00";
 209         any.length = 2;
 210         spki.algorithm.parameters = &any;
 211
 212         ret = hx509_ca_tbs_set_spki(context->hx509ctx, tbs, &spki);
 213         der_free_oid(&spki.algorithm.algorithm);
 214         if (ret)
 215             goto out;
 216     }
 217
 218     {
 219         hx509_certs certs;
 220         hx509_cert template;
 221
 222         ret = hx509_certs_init(context->hx509ctx, config->kx509_template, 0,
 223                                NULL, &certs);
 224         if (ret) {
 225             kdc_log(context, config, 0, "Failed to load template %s",
 226                     config->kx509_template);
 227             goto out;
 228         }
 229         ret = hx509_get_one_cert(context->hx509ctx, certs, &template);
 230         hx509_certs_free(&certs);
 231         if (ret) {
 232             kdc_log(context, config, 0, "Failed to find template in %s",
 233                     config->kx509_template);
 234             goto out;
 235         }
 236         ret = hx509_ca_tbs_set_template(context->hx509ctx, tbs,
 237                                         HX509_CA_TEMPLATE_SUBJECT|
 238                                         HX509_CA_TEMPLATE_KU|
 239                                         HX509_CA_TEMPLATE_EKU,
 240                                         template);
 241         hx509_cert_free(template);
 242         if (ret)
 243             goto out;
 244     }
 245
 246     hx509_ca_tbs_set_notAfter(context->hx509ctx, tbs, endtime);
 247
 248     hx509_ca_tbs_subject_expand(context->hx509ctx, tbs, env);
 249     hx509_env_free(&env);
 250
 251     ret = hx509_ca_sign(context->hx509ctx, tbs, signer, &cert);
 252     hx509_cert_free(signer);
 253     if (ret)
 254         goto out;
 255
 256     hx509_ca_tbs_free(&tbs);
 257
 258     ret = hx509_cert_binary(context->hx509ctx, cert, certificate);
 259     hx509_cert_free(cert);
 260     if (ret)
 261         goto out;
 262
 263     return 0;
 264 out:
 265     if (env)
 266         hx509_env_free(&env);
 267     if (tbs)
 268         hx509_ca_tbs_free(&tbs);
 269     if (signer)
 270         hx509_cert_free(signer);
 271     krb5_set_error_message(context, ret, "cert creation failed");
 272     return ret;
 273 }
 274
 275 /*
 276  *
 277  */
 278
 279 krb5_error_code
 280 _kdc_do_kx509(krb5_context context,
 281               krb5_kdc_configuration *config,
 282               const struct Kx509Request *req, krb5_data *reply,
 283               const char *from, struct sockaddr *addr)
 284 {
 285     krb5_error_code ret;
 286     krb5_ticket *ticket = NULL;
 287     krb5_flags ap_req_options;
 288     krb5_auth_context ac = NULL;
 289     krb5_keytab id = NULL;
 290     krb5_principal sprincipal = NULL, cprincipal = NULL;
 291     char *cname = NULL;
 292     Kx509Response rep;
 293     size_t size;
 294     krb5_keyblock *key = NULL;
 295
 296     krb5_data_zero(reply);
 297     memset(&rep, 0, sizeof(rep));
 298
 299     if(!config->enable_kx509) {
 300         kdc_log(context, config, 0,
 301                 "Rejected kx509 request (disabled) from %s", from);
 302         return KRB5KDC_ERR_POLICY;
 303     }
 304
 305     kdc_log(context, config, 0, "Kx509 request from %s", from);
 306
 307     ret = krb5_kt_resolve(context, "HDB:", &id);
 308     if (ret) {
 309         kdc_log(context, config, 0, "Can't open database for digest");
 310         goto out;
 311     }
 312
 313     ret = krb5_rd_req(context,
 314                       &ac,
 315                       &req->authenticator,
 316                       NULL,
 317                       id,
 318                       &ap_req_options,
 319                       &ticket);
 320     if (ret)
 321         goto out;
 322
 323     ret = krb5_ticket_get_client(context, ticket, &cprincipal);
 324     if (ret)
 325         goto out;
 326
 327     ret = krb5_unparse_name(context, cprincipal, &cname);
 328     if (ret)
 329         goto out;
 330
 331     /* verify server principal */
 332
 333     ret = krb5_sname_to_principal(context, NULL, "kca_service",
 334                                   KRB5_NT_UNKNOWN, &sprincipal);
 335     if (ret)
 336         goto out;
 337
 338     {
 339         krb5_principal principal = NULL;
 340
 341         ret = krb5_ticket_get_server(context, ticket, &principal);
 342         if (ret)
 343             goto out;
 344
 345         ret = krb5_principal_compare(context, sprincipal, principal);
 346         krb5_free_principal(context, principal);
 347         if (ret != TRUE) {
 348             ret = KRB5KDC_ERR_SERVER_NOMATCH;
 349             krb5_set_error_message(context, ret,
 350                                    "User %s used wrong Kx509 service principal",
 351                                    cname);
 352             goto out;
 353         }
 354     }
 355
 356     ret = krb5_auth_con_getkey(context, ac, &key);
 357     if (ret == 0 && key == NULL)
 358         ret = KRB5KDC_ERR_NULL_KEY;
 359     if (ret) {
 360         krb5_set_error_message(context, ret, "Kx509 can't get session key");
 361         goto out;
 362     }
 363
 364     ret = verify_req_hash(context, req, key);
 365     if (ret)
 366         goto out;
 367
 368     /* Verify that the key is encoded RSA key */
 369     {
 370         RSAPublicKey key;
 371         size_t size;
 372
 373         ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
 374                                   &key, &size);
 375         if (ret)
 376             goto out;
 377         free_RSAPublicKey(&key);
 378         if (size != req->pk_key.length) {
 379             ret = ASN1_EXTRA_DATA;
 380             goto out;
 381         }
 382     }
 383
 384     ALLOC(rep.certificate);
 385     if (rep.certificate == NULL)
 386         goto out;
 387     krb5_data_zero(rep.certificate);
 388     ALLOC(rep.hash);
 389     if (rep.hash == NULL)
 390         goto out;
 391     krb5_data_zero(rep.hash);
 392
 393     ret = build_certificate(context, config, &req->pk_key,
 394                             krb5_ticket_get_endtime(context, ticket),
 395                             cprincipal, rep.certificate);
 396     if (ret)
 397         goto out;
 398
 399     ret = calculate_reply_hash(context, key, &rep);
 400     if (ret)
 401         goto out;
 402
 403     /*
 404      * Encode reply, [ version | Kx509Response ]
 405      */
 406
 407     {
 408         krb5_data data;
 409
 410         ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
 411                            &size, ret);
 412         if (ret) {
 413             krb5_set_error_message(context, ret, "Failed to encode kx509 reply");
 414             goto out;
 415         }
 416         if (size != data.length)
 417             krb5_abortx(context, "ASN1 internal error");
 418
 419         ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
 420         if (ret) {
 421             free(data.data);
 422             goto out;
 423         }
 424         memcpy(reply->data, version_2_0, sizeof(version_2_0));
 425         memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
 426                data.data, data.length);
 427         free(data.data);
 428     }
 429
 430     kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
 431
 432 out:
 433     if (ac)
 434         krb5_auth_con_free(context, ac);
 435     if (ret)
 436         krb5_warn(context, ret, "Kx509 request from %s failed", from);
 437     if (ticket)
 438         krb5_free_ticket(context, ticket);
 439     if (id)
 440         krb5_kt_close(context, id);
 441     if (sprincipal)
 442         krb5_free_principal(context, sprincipal);
 443     if (cprincipal)
 444         krb5_free_principal(context, cprincipal);
 445     if (key)
 446         krb5_free_keyblock (context, key);
 447     if (cname)
 448         free(cname);
 449     free_Kx509Response(&rep);
 450
 451     return 0;
 452 }
 453
 454 #endif /* KX509 */