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 RCSID("$Id$");
  40
  41 /*
  42  *
  43  */
  44
  45 krb5_error_code
  46 _kdc_try_kx509_request(void *ptr, size_t len, 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_string(context, "pk-hash have wrong length: %lu",
  71                               (unsigned long)req->pk_hash.length);
  72         return KRB5KDC_ERR_PREAUTH_FAILED;
  73     }
  74
  75     HMAC_CTX_init(&ctx);
  76     HMAC_Init_ex(&ctx,
  77                  key->keyvalue.data, key->keyvalue.length,
  78                  EVP_sha1(), NULL);
  79     if (sizeof(digest) != HMAC_size(&ctx))
  80         krb5_abortx(context, "runtime error, hmac buffer wrong size in kx509");
  81     HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
  82     HMAC_Update(&ctx, req->pk_key.data, req->pk_key.length);
  83     HMAC_Final(&ctx, digest, 0);
  84     HMAC_CTX_cleanup(&ctx);
  85
  86     if (memcmp(req->pk_hash.data, digest, sizeof(digest)) != 0) {
  87         krb5_set_error_string(context, "pk-hash is not correct");
  88         return KRB5KDC_ERR_PREAUTH_FAILED;
  89     }
  90     return 0;
  91 }
  92
  93 static krb5_error_code
  94 calculate_reply_hash(krb5_context context,
  95                      krb5_keyblock *key,
  96                      Kx509Response *rep)
  97 {
  98     HMAC_CTX ctx;
  99
 100     HMAC_CTX_init(&ctx);
 101
 102     HMAC_Init_ex(&ctx,
 103                  key->keyvalue.data, key->keyvalue.length,
 104                  EVP_sha1(), NULL);
 105     rep->hash->length = HMAC_size(&ctx);
 106     rep->hash->data = malloc(rep->hash->length);
 107     if (rep->hash->data == NULL) {
 108         HMAC_CTX_cleanup(&ctx);
 109         krb5_set_error_string(context, "out of memory");
 110         return ENOMEM;
 111     }
 112
 113     HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
 114     if (rep->error_code) {
 115         int32_t t = *rep->error_code;
 116         do {
 117             unsigned char p = (t & 0xff);
 118             HMAC_Update(&ctx, &p, 1);
 119             t >>= 8;
 120         } while (t);
 121     }
 122     if (rep->certificate)
 123         HMAC_Update(&ctx, rep->certificate->data, rep->certificate->length);
 124     if (rep->e_text)
 125         HMAC_Update(&ctx, (unsigned char *)*rep->e_text, strlen(*rep->e_text));
 126
 127     HMAC_Final(&ctx, rep->hash->data, 0);
 128     HMAC_CTX_cleanup(&ctx);
 129
 130     return 0;
 131 }
 132
 133 /*
 134  * Build a certifate for `principal´ that will expire at `endtime´.
 135  */
 136
 137 static krb5_error_code
 138 build_certificate(krb5_context context,
 139                   krb5_kdc_configuration *config,
 140                   const krb5_data *key,
 141                   time_t endtime,
 142                   krb5_principal principal,
 143                   krb5_data *certificate)
 144 {
 145     hx509_context hxctx = NULL;
 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_context_init(&hxctx);
 158     if (ret)
 159         goto out;
 160
 161     ret = hx509_env_add(hxctx, &env, "principal-name",
 162                         krb5_principal_get_comp_string(context, principal, 0));
 163     if (ret)
 164         goto out;
 165
 166     {
 167         hx509_certs certs;
 168         hx509_query *q;
 169
 170         ret = hx509_certs_init(hxctx, config->kx509_ca, 0,
 171                                NULL, &certs);
 172         if (ret) {
 173             kdc_log(context, config, 0, "Failed to load CA %s",
 174                     config->kx509_ca);
 175             goto out;
 176         }
 177         ret = hx509_query_alloc(hxctx, &q);
 178         if (ret) {
 179             hx509_certs_free(&certs);
 180             goto out;
 181         }
 182
 183         hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
 184         hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
 185
 186         ret = hx509_certs_find(hxctx, certs, q, &signer);
 187         hx509_query_free(hxctx, q);
 188         hx509_certs_free(&certs);
 189         if (ret) {
 190             kdc_log(context, config, 0, "Failed to find a CA in %s",
 191                     config->kx509_ca);
 192             goto out;
 193         }
 194     }
 195
 196     ret = hx509_ca_tbs_init(hxctx, &tbs);
 197     if (ret)
 198         goto out;
 199
 200     {
 201         SubjectPublicKeyInfo spki;
 202         heim_any any;
 203
 204         memset(&spki, 0, sizeof(spki));
 205
 206         spki.subjectPublicKey.data = key->data;
 207         spki.subjectPublicKey.length = key->length * 8;
 208
 209         ret = der_copy_oid(oid_id_pkcs1_rsaEncryption(),
 210                            &spki.algorithm.algorithm);
 211
 212         any.data = "\x05\x00";
 213         any.length = 2;
 214         spki.algorithm.parameters = &any;
 215
 216         ret = hx509_ca_tbs_set_spki(hxctx, tbs, &spki);
 217         der_free_oid(&spki.algorithm.algorithm);
 218         if (ret)
 219             goto out;
 220     }
 221
 222     {
 223         hx509_certs certs;
 224         hx509_cert template;
 225
 226         ret = hx509_certs_init(hxctx, config->kx509_template, 0,
 227                                NULL, &certs);
 228         if (ret) {
 229             kdc_log(context, config, 0, "Failed to load template %s",
 230                     config->kx509_template);
 231             goto out;
 232         }
 233         ret = hx509_get_one_cert(hxctx, certs, &template);
 234         hx509_certs_free(&certs);
 235         if (ret) {
 236             kdc_log(context, config, 0, "Failed to find template in %s",
 237                     config->kx509_template);
 238             goto out;
 239         }
 240         ret = hx509_ca_tbs_set_template(hxctx, tbs,
 241                                         HX509_CA_TEMPLATE_SUBJECT|
 242                                         HX509_CA_TEMPLATE_KU|
 243                                         HX509_CA_TEMPLATE_EKU,
 244                                         template);
 245         hx509_cert_free(template);
 246         if (ret)
 247             goto out;
 248     }
 249
 250     hx509_ca_tbs_set_notAfter(hxctx, tbs, endtime);
 251
 252     hx509_ca_tbs_subject_expand(hxctx, tbs, env);
 253     hx509_env_free(&env);
 254
 255     ret = hx509_ca_sign(hxctx, tbs, signer, &cert);
 256     hx509_cert_free(signer);
 257     if (ret)
 258         goto out;
 259
 260     hx509_ca_tbs_free(&tbs);
 261
 262     ret = hx509_cert_binary(hxctx, cert, certificate);
 263     hx509_cert_free(cert);
 264     if (ret)
 265         goto out;
 266
 267     hx509_context_free(&hxctx);
 268
 269     return 0;
 270 out:
 271     if (env)
 272         hx509_env_free(&env);
 273     if (tbs)
 274         hx509_ca_tbs_free(&tbs);
 275     if (signer)
 276         hx509_cert_free(signer);
 277     if (hxctx)
 278         hx509_context_free(&hxctx);
 279     krb5_set_error_string(context, "cert creation failed");
 280     return ret;
 281 }
 282
 283 /*
 284  *
 285  */
 286
 287 krb5_error_code
 288 _kdc_do_kx509(krb5_context context,
 289               krb5_kdc_configuration *config,
 290               const Kx509Request *req, krb5_data *reply,
 291               const char *from, struct sockaddr *addr)
 292 {
 293     krb5_error_code ret;
 294     krb5_ticket *ticket = NULL;
 295     krb5_flags ap_req_options;
 296     krb5_auth_context ac = NULL;
 297     krb5_keytab id = NULL;
 298     krb5_principal sprincipal = NULL, cprincipal = NULL;
 299     char *cname = NULL;
 300     Kx509Response rep;
 301     size_t size;
 302     krb5_keyblock *key = NULL;
 303
 304     krb5_data_zero(reply);
 305     memset(&rep, 0, sizeof(rep));
 306
 307     if(!config->enable_kx509) {
 308         kdc_log(context, config, 0,
 309                 "Rejected kx509 request (disabled) from %s", from);
 310         return KRB5KDC_ERR_POLICY;
 311     }
 312
 313     kdc_log(context, config, 0, "Kx509 request from %s", from);
 314
 315     ret = krb5_kt_resolve(context, "HDB:", &id);
 316     if (ret) {
 317         kdc_log(context, config, 0, "Can't open database for digest");
 318         goto out;
 319     }
 320
 321     ret = krb5_rd_req(context,
 322                       &ac,
 323                       &req->authenticator,
 324                       NULL,
 325                       id,
 326                       &ap_req_options,
 327                       &ticket);
 328     if (ret)
 329         goto out;
 330
 331     ret = krb5_ticket_get_client(context, ticket, &cprincipal);
 332     if (ret)
 333         goto out;
 334
 335     ret = krb5_unparse_name(context, cprincipal, &cname);
 336     if (ret)
 337         goto out;
 338
 339     /* verify server principal */
 340
 341     ret = krb5_sname_to_principal(context, NULL, "kca_service",
 342                                   KRB5_NT_UNKNOWN, &sprincipal);
 343     if (ret)
 344         goto out;
 345
 346     {
 347         krb5_principal principal = NULL;
 348
 349         ret = krb5_ticket_get_server(context, ticket, &principal);
 350         if (ret)
 351             goto out;
 352
 353         ret = krb5_principal_compare(context, sprincipal, principal);
 354         krb5_free_principal(context, principal);
 355         if (ret != TRUE) {
 356             ret = KRB5KDC_ERR_SERVER_NOMATCH;
 357             krb5_set_error_string(context,
 358                                   "User %s used wrong Kx509 service principal",
 359                                   cname);
 360             goto out;
 361         }
 362     }
 363
 364     ret = krb5_auth_con_getkey(context, ac, &key);
 365     if (ret || key == NULL) {
 366         krb5_set_error_string(context, "Kx509 can't get session key");
 367         goto out;
 368     }
 369
 370     ret = verify_req_hash(context, req, key);
 371     if (ret)
 372         goto out;
 373
 374     /* Verify that the key is encoded RSA key */
 375     {
 376         RSAPublicKey key;
 377         size_t size;
 378
 379         ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
 380                                   &key, &size);
 381         if (ret)
 382             goto out;
 383         free_RSAPublicKey(&key);
 384         if (size != req->pk_key.length)
 385             ;
 386     }
 387
 388     ALLOC(rep.certificate);
 389     if (rep.certificate == NULL)
 390         goto out;
 391     krb5_data_zero(rep.certificate);
 392     ALLOC(rep.hash);
 393     if (rep.hash == NULL)
 394         goto out;
 395     krb5_data_zero(rep.hash);
 396
 397     ret = build_certificate(context, config, &req->pk_key,
 398                             krb5_ticket_get_endtime(context, ticket),
 399                             cprincipal, rep.certificate);
 400     if (ret)
 401         goto out;
 402
 403     ret = calculate_reply_hash(context, key, &rep);
 404     if (ret)
 405         goto out;
 406
 407     /*
 408      * Encode reply, [ version | Kx509Response ]
 409      */
 410
 411     {
 412         krb5_data data;
 413
 414         ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
 415                            &size, ret);
 416         if (ret) {
 417             krb5_set_error_string(context, "Failed to encode kx509 reply");
 418             goto out;
 419         }
 420         if (size != data.length)
 421             krb5_abortx(context, "ASN1 internal error");
 422
 423         ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
 424         if (ret) {
 425             free(data.data);
 426             goto out;
 427         }
 428         memcpy(reply->data, version_2_0, sizeof(version_2_0));
 429         memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
 430                data.data, data.length);
 431         free(data.data);
 432     }
 433
 434     kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
 435
 436 out:
 437     if (ac)
 438         krb5_auth_con_free(context, ac);
 439     if (ret)
 440         krb5_warn(context, ret, "Kx509 request from %s failed", from);
 441     if (ticket)
 442         krb5_free_ticket(context, ticket);
 443     if (id)
 444         krb5_kt_close(context, id);
 445     if (sprincipal)
 446         krb5_free_principal(context, sprincipal);
 447     if (cprincipal)
 448         krb5_free_principal(context, cprincipal);
 449     if (key)
 450         krb5_free_keyblock (context, key);
 451     if (cname)
 452         free(cname);
 453     free_Kx509Response(&rep);
 454
 455     return 0;
 456 }