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     char *name = NULL;
 147     const char *kx509_ca;
 148     hx509_ca_tbs tbs = NULL;
 149     hx509_env env = NULL;
 150     hx509_cert cert = NULL;
 151     hx509_cert signer = NULL;
 152     krb5_boolean def_bool;
 153     int ret;
 154
 155     ret = krb5_unparse_name_flags(context, principal,
 156                                   KRB5_PRINCIPAL_UNPARSE_NO_REALM,
 157                                   &name);
 158     if (ret)
 159         goto out;
 160
 161     ret = hx509_env_add(context->hx509ctx, &env, "principal-name-without-realm",
 162                         name);
 163     krb5_xfree(name);
 164     name = NULL;
 165     if (ret)
 166         goto out;
 167
 168     /*
 169      * Include the realm in the principal-name env var; the template
 170      * might not use $principal-name-realm after all.
 171      */
 172     ret = krb5_unparse_name(context, principal, &name);
 173     if (ret)
 174         goto out;
 175
 176     ret = hx509_env_add(context->hx509ctx, &env, "principal-name",
 177                         name);
 178     if (ret)
 179         goto out;
 180
 181     ret = hx509_env_add(context->hx509ctx, &env, "principal-name-realm",
 182                         krb5_principal_get_realm(context, principal));
 183     if (ret)
 184         goto out;
 185
 186     /* Pick an issuer based on the crealm if we can */
 187     kx509_ca = krb5_config_get_string(context, NULL, "kdc",
 188                                       krb5_principal_get_realm(context,
 189                                                                principal),
 190                                       "kx509_ca", NULL);
 191     if (kx509_ca == NULL)
 192         kx509_ca = config->kx509_ca;
 193
 194     {
 195         hx509_certs certs;
 196         hx509_query *q;
 197
 198         ret = hx509_certs_init(context->hx509ctx, config->kx509_ca, 0,
 199                                NULL, &certs);
 200         if (ret) {
 201             kdc_log(context, config, 0, "Failed to load CA %s",
 202                     config->kx509_ca);
 203             goto out;
 204         }
 205         ret = hx509_query_alloc(context->hx509ctx, &q);
 206         if (ret) {
 207             hx509_certs_free(&certs);
 208             goto out;
 209         }
 210
 211         hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
 212         hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
 213
 214         ret = hx509_certs_find(context->hx509ctx, certs, q, &signer);
 215         hx509_query_free(context->hx509ctx, q);
 216         hx509_certs_free(&certs);
 217         if (ret) {
 218             kdc_log(context, config, 0, "Failed to find a CA in %s",
 219                     config->kx509_ca);
 220             goto out;
 221         }
 222     }
 223
 224     ret = hx509_ca_tbs_init(context->hx509ctx, &tbs);
 225     if (ret)
 226         goto out;
 227
 228     {
 229         SubjectPublicKeyInfo spki;
 230         heim_any any;
 231
 232         memset(&spki, 0, sizeof(spki));
 233
 234         spki.subjectPublicKey.data = key->data;
 235         spki.subjectPublicKey.length = key->length * 8;
 236
 237         ret = der_copy_oid(&asn1_oid_id_pkcs1_rsaEncryption,
 238                            &spki.algorithm.algorithm);
 239
 240         any.data = "\x05\x00";
 241         any.length = 2;
 242         spki.algorithm.parameters = &any;
 243
 244         ret = hx509_ca_tbs_set_spki(context->hx509ctx, tbs, &spki);
 245         der_free_oid(&spki.algorithm.algorithm);
 246         if (ret)
 247             goto out;
 248     }
 249
 250     {
 251         hx509_certs certs;
 252         hx509_cert template;
 253
 254         ret = hx509_certs_init(context->hx509ctx, config->kx509_template, 0,
 255                                NULL, &certs);
 256         if (ret) {
 257             kdc_log(context, config, 0, "Failed to load template %s",
 258                     config->kx509_template);
 259             goto out;
 260         }
 261         ret = hx509_get_one_cert(context->hx509ctx, certs, &template);
 262         hx509_certs_free(&certs);
 263         if (ret) {
 264             kdc_log(context, config, 0, "Failed to find template in %s",
 265                     config->kx509_template);
 266             goto out;
 267         }
 268         ret = hx509_ca_tbs_set_template(context->hx509ctx, tbs,
 269                                         HX509_CA_TEMPLATE_SUBJECT|
 270                                         HX509_CA_TEMPLATE_KU|
 271                                         HX509_CA_TEMPLATE_EKU,
 272                                         template);
 273         hx509_cert_free(template);
 274         if (ret)
 275             goto out;
 276     }
 277
 278     def_bool = krb5_config_get_bool_default(context, NULL, TRUE, "kdc",
 279                                             "kx509_include_pkinit_san",
 280                                             NULL);
 281     if (krb5_config_get_bool_default(context, NULL, def_bool, "kdc",
 282                                      krb5_principal_get_realm(context,
 283                                                               principal),
 284                                      "kx509_include_pkinit_san",
 285                                      NULL)) {
 286         ret = hx509_ca_tbs_add_san_pkinit(context->hx509ctx, tbs, name);
 287         if (ret)
 288             goto out;
 289     }
 290
 291     hx509_ca_tbs_set_notAfter(context->hx509ctx, tbs, endtime);
 292
 293     hx509_ca_tbs_subject_expand(context->hx509ctx, tbs, env);
 294     hx509_env_free(&env);
 295
 296     ret = hx509_ca_sign(context->hx509ctx, tbs, signer, &cert);
 297     hx509_cert_free(signer);
 298     if (ret)
 299         goto out;
 300
 301     hx509_ca_tbs_free(&tbs);
 302
 303     ret = hx509_cert_binary(context->hx509ctx, cert, certificate);
 304     hx509_cert_free(cert);
 305     if (ret)
 306         goto out;
 307
 308     /* cleanup on success */
 309     krb5_xfree(name);
 310
 311     return 0;
 312 out:
 313     if (name)
 314         krb5_xfree(name);
 315     if (env)
 316         hx509_env_free(&env);
 317     if (tbs)
 318         hx509_ca_tbs_free(&tbs);
 319     if (signer)
 320         hx509_cert_free(signer);
 321     krb5_set_error_message(context, ret, "cert creation failed");
 322     return ret;
 323 }
 324
 325 krb5_error_code
 326 kdc_kx509_verify_service_principal(krb5_context context,
 327                                    const char *cname,
 328                                    krb5_principal sprincipal)
 329 {
 330     krb5_error_code ret, aret;
 331     krb5_boolean bret;
 332     krb5_principal principal = NULL;
 333     char *expected = NULL;
 334     char localhost[MAXHOSTNAMELEN];
 335
 336     ret = gethostname(localhost, sizeof(localhost) - 1);
 337     if (ret != 0) {
 338         ret = errno;
 339         krb5_set_error_message(context, ret,
 340                                N_("Failed to get local hostname", ""));
 341         return ret;
 342     }
 343     localhost[sizeof(localhost) - 1] = '\0';
 344
 345     ret = krb5_make_principal(context, &principal, "", "kca_service",
 346                               localhost, NULL);
 347     if (ret)
 348         goto out;
 349
 350     bret = krb5_principal_compare_any_realm(context, sprincipal, principal);
 351     if (bret == TRUE)
 352         goto out;       /* found a match */
 353
 354     ret = KRB5KDC_ERR_SERVER_NOMATCH;
 355
 356     aret = krb5_unparse_name(context, sprincipal, &expected);
 357     if (aret)
 358         goto out;
 359
 360     krb5_set_error_message(context, ret,
 361                            "User %s used wrong Kx509 service "
 362                            "principal, expected: %s",
 363                            cname, expected);
 364
 365   out:
 366     krb5_xfree(expected);
 367     krb5_free_principal(context, principal);
 368
 369     return ret;
 370 }
 371
 372 /*
 373  *
 374  */
 375
 376 krb5_error_code
 377 _kdc_do_kx509(krb5_context context,
 378               krb5_kdc_configuration *config,
 379               const struct Kx509Request *req, krb5_data *reply,
 380               const char *from, struct sockaddr *addr)
 381 {
 382     krb5_error_code ret;
 383     krb5_ticket *ticket = NULL;
 384     krb5_flags ap_req_options;
 385     krb5_auth_context ac = NULL;
 386     krb5_keytab id = NULL;
 387     krb5_principal sprincipal = NULL, cprincipal = NULL;
 388     char *cname = NULL;
 389     Kx509Response rep;
 390     size_t size;
 391     krb5_keyblock *key = NULL;
 392     krb5_boolean def_bool;
 393
 394     krb5_data_zero(reply);
 395     memset(&rep, 0, sizeof(rep));
 396
 397     if(!config->enable_kx509) {
 398         kdc_log(context, config, 0,
 399                 "Rejected kx509 request (disabled) from %s", from);
 400         return KRB5KDC_ERR_POLICY;
 401     }
 402
 403     kdc_log(context, config, 0, "Kx509 request from %s", from);
 404
 405     ret = krb5_kt_resolve(context, "HDBGET:", &id);
 406     if (ret) {
 407         kdc_log(context, config, 0, "Can't open database for digest");
 408         goto out;
 409     }
 410
 411     ret = krb5_rd_req(context,
 412                       &ac,
 413                       &req->authenticator,
 414                       NULL,
 415                       id,
 416                       &ap_req_options,
 417                       &ticket);
 418     if (ret)
 419         goto out;
 420
 421     ret = krb5_ticket_get_client(context, ticket, &cprincipal);
 422     if (ret)
 423         goto out;
 424
 425     def_bool = krb5_config_get_bool_default(context, NULL, TRUE, "kdc",
 426                                             "require_initial_kca_tickets",
 427                                             NULL);
 428     if (!ticket->ticket.flags.initial &&
 429         krb5_config_get_bool_default(context, NULL, def_bool, "kdc",
 430                                       krb5_principal_get_realm(context,
 431                                                                cprincipal),
 432                                       "require_initial_kca_tickets", NULL)) {
 433         ret = KRB5KDC_ERR_POLICY;
 434         goto out;
 435     }
 436
 437     ret = krb5_unparse_name(context, cprincipal, &cname);
 438     if (ret)
 439         goto out;
 440
 441     ret = krb5_ticket_get_server(context, ticket, &sprincipal);
 442     if (ret)
 443         goto out;
 444
 445     ret = kdc_kx509_verify_service_principal(context, cname, sprincipal);
 446     if (ret)
 447         goto out;
 448
 449     ret = krb5_auth_con_getkey(context, ac, &key);
 450     if (ret == 0 && key == NULL)
 451         ret = KRB5KDC_ERR_NULL_KEY;
 452     if (ret) {
 453         krb5_set_error_message(context, ret, "Kx509 can't get session key");
 454         goto out;
 455     }
 456
 457     ret = verify_req_hash(context, req, key);
 458     if (ret)
 459         goto out;
 460
 461     /* Verify that the key is encoded RSA key */
 462     {
 463         RSAPublicKey rsapkey;
 464         size_t rsapkeysize;
 465
 466         ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
 467                                   &rsapkey, &rsapkeysize);
 468         if (ret)
 469             goto out;
 470         free_RSAPublicKey(&rsapkey);
 471         if (rsapkeysize != req->pk_key.length) {
 472             ret = ASN1_EXTRA_DATA;
 473             goto out;
 474         }
 475     }
 476
 477     ALLOC(rep.certificate);
 478     if (rep.certificate == NULL)
 479         goto out;
 480     krb5_data_zero(rep.certificate);
 481     ALLOC(rep.hash);
 482     if (rep.hash == NULL)
 483         goto out;
 484     krb5_data_zero(rep.hash);
 485
 486     ret = build_certificate(context, config, &req->pk_key,
 487                             krb5_ticket_get_endtime(context, ticket),
 488                             cprincipal, rep.certificate);
 489     if (ret)
 490         goto out;
 491
 492     ret = calculate_reply_hash(context, key, &rep);
 493     if (ret)
 494         goto out;
 495
 496     /*
 497      * Encode reply, [ version | Kx509Response ]
 498      */
 499
 500     {
 501         krb5_data data;
 502
 503         ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
 504                            &size, ret);
 505         if (ret) {
 506             krb5_set_error_message(context, ret, "Failed to encode kx509 reply");
 507             goto out;
 508         }
 509         if (size != data.length)
 510             krb5_abortx(context, "ASN1 internal error");
 511
 512         ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
 513         if (ret) {
 514             free(data.data);
 515             goto out;
 516         }
 517         memcpy(reply->data, version_2_0, sizeof(version_2_0));
 518         memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
 519                data.data, data.length);
 520         free(data.data);
 521     }
 522
 523     kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
 524
 525 out:
 526     if (ac)
 527         krb5_auth_con_free(context, ac);
 528     if (ret)
 529         krb5_warn(context, ret, "Kx509 request from %s failed", from);
 530     if (ticket)
 531         krb5_free_ticket(context, ticket);
 532     if (id)
 533         krb5_kt_close(context, id);
 534     if (sprincipal)
 535         krb5_free_principal(context, sprincipal);
 536     if (cprincipal)
 537         krb5_free_principal(context, cprincipal);
 538     if (key)
 539         krb5_free_keyblock (context, key);
 540     if (cname)
 541         free(cname);
 542     free_Kx509Response(&rep);
 543
 544     return 0;
 545 }
 546
 547 #endif /* KX509 */