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_context hxctx = NULL;
 147     hx509_ca_tbs tbs = NULL;
 148     hx509_env env = NULL;
 149     hx509_cert cert = NULL;
 150     hx509_cert signer = NULL;
 151     int ret;
 152
 153     if (krb5_principal_get_comp_string(context, principal, 1) != NULL) {
 154         kdc_log(context, config, 0, "Principal is not a user");
 155         return EINVAL;
 156     }
 157
 158     ret = hx509_context_init(&hxctx);
 159     if (ret)
 160         goto out;
 161
 162     ret = hx509_env_add(hxctx, &env, "principal-name",
 163                         krb5_principal_get_comp_string(context, principal, 0));
 164     if (ret)
 165         goto out;
 166
 167     {
 168         hx509_certs certs;
 169         hx509_query *q;
 170
 171         ret = hx509_certs_init(hxctx, config->kx509_ca, 0,
 172                                NULL, &certs);
 173         if (ret) {
 174             kdc_log(context, config, 0, "Failed to load CA %s",
 175                     config->kx509_ca);
 176             goto out;
 177         }
 178         ret = hx509_query_alloc(hxctx, &q);
 179         if (ret) {
 180             hx509_certs_free(&certs);
 181             goto out;
 182         }
 183
 184         hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
 185         hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
 186
 187         ret = hx509_certs_find(hxctx, certs, q, &signer);
 188         hx509_query_free(hxctx, q);
 189         hx509_certs_free(&certs);
 190         if (ret) {
 191             kdc_log(context, config, 0, "Failed to find a CA in %s",
 192                     config->kx509_ca);
 193             goto out;
 194         }
 195     }
 196
 197     ret = hx509_ca_tbs_init(hxctx, &tbs);
 198     if (ret)
 199         goto out;
 200
 201     {
 202         SubjectPublicKeyInfo spki;
 203         heim_any any;
 204
 205         memset(&spki, 0, sizeof(spki));
 206
 207         spki.subjectPublicKey.data = key->data;
 208         spki.subjectPublicKey.length = key->length * 8;
 209
 210         ret = der_copy_oid(&asn1_oid_id_pkcs1_rsaEncryption,
 211                            &spki.algorithm.algorithm);
 212
 213         any.data = "\x05\x00";
 214         any.length = 2;
 215         spki.algorithm.parameters = &any;
 216
 217         ret = hx509_ca_tbs_set_spki(hxctx, tbs, &spki);
 218         der_free_oid(&spki.algorithm.algorithm);
 219         if (ret)
 220             goto out;
 221     }
 222
 223     {
 224         hx509_certs certs;
 225         hx509_cert template;
 226
 227         ret = hx509_certs_init(hxctx, config->kx509_template, 0,
 228                                NULL, &certs);
 229         if (ret) {
 230             kdc_log(context, config, 0, "Failed to load template %s",
 231                     config->kx509_template);
 232             goto out;
 233         }
 234         ret = hx509_get_one_cert(hxctx, certs, &template);
 235         hx509_certs_free(&certs);
 236         if (ret) {
 237             kdc_log(context, config, 0, "Failed to find template in %s",
 238                     config->kx509_template);
 239             goto out;
 240         }
 241         ret = hx509_ca_tbs_set_template(hxctx, tbs,
 242                                         HX509_CA_TEMPLATE_SUBJECT|
 243                                         HX509_CA_TEMPLATE_KU|
 244                                         HX509_CA_TEMPLATE_EKU,
 245                                         template);
 246         hx509_cert_free(template);
 247         if (ret)
 248             goto out;
 249     }
 250
 251     hx509_ca_tbs_set_notAfter(hxctx, tbs, endtime);
 252
 253     hx509_ca_tbs_subject_expand(hxctx, tbs, env);
 254     hx509_env_free(&env);
 255
 256     ret = hx509_ca_sign(hxctx, tbs, signer, &cert);
 257     hx509_cert_free(signer);
 258     if (ret)
 259         goto out;
 260
 261     hx509_ca_tbs_free(&tbs);
 262
 263     ret = hx509_cert_binary(hxctx, cert, certificate);
 264     hx509_cert_free(cert);
 265     if (ret)
 266         goto out;
 267
 268     hx509_context_free(&hxctx);
 269
 270     return 0;
 271 out:
 272     if (env)
 273         hx509_env_free(&env);
 274     if (tbs)
 275         hx509_ca_tbs_free(&tbs);
 276     if (signer)
 277         hx509_cert_free(signer);
 278     if (hxctx)
 279         hx509_context_free(&hxctx);
 280     krb5_set_error_message(context, ret, "cert creation failed");
 281     return ret;
 282 }
 283
 284 /*
 285  *
 286  */
 287
 288 krb5_error_code
 289 _kdc_do_kx509(krb5_context context,
 290               krb5_kdc_configuration *config,
 291               const struct Kx509Request *req, krb5_data *reply,
 292               const char *from, struct sockaddr *addr)
 293 {
 294     krb5_error_code ret;
 295     krb5_ticket *ticket = NULL;
 296     krb5_flags ap_req_options;
 297     krb5_auth_context ac = NULL;
 298     krb5_keytab id = NULL;
 299     krb5_principal sprincipal = NULL, cprincipal = NULL;
 300     char *cname = NULL;
 301     Kx509Response rep;
 302     size_t size;
 303     krb5_keyblock *key = NULL;
 304
 305     krb5_data_zero(reply);
 306     memset(&rep, 0, sizeof(rep));
 307
 308     if(!config->enable_kx509) {
 309         kdc_log(context, config, 0,
 310                 "Rejected kx509 request (disabled) from %s", from);
 311         return KRB5KDC_ERR_POLICY;
 312     }
 313
 314     kdc_log(context, config, 0, "Kx509 request from %s", from);
 315
 316     ret = krb5_kt_resolve(context, "HDB:", &id);
 317     if (ret) {
 318         kdc_log(context, config, 0, "Can't open database for digest");
 319         goto out;
 320     }
 321
 322     ret = krb5_rd_req(context,
 323                       &ac,
 324                       &req->authenticator,
 325                       NULL,
 326                       id,
 327                       &ap_req_options,
 328                       &ticket);
 329     if (ret)
 330         goto out;
 331
 332     ret = krb5_ticket_get_client(context, ticket, &cprincipal);
 333     if (ret)
 334         goto out;
 335
 336     ret = krb5_unparse_name(context, cprincipal, &cname);
 337     if (ret)
 338         goto out;
 339
 340     /* verify server principal */
 341
 342     ret = krb5_sname_to_principal(context, NULL, "kca_service",
 343                                   KRB5_NT_UNKNOWN, &sprincipal);
 344     if (ret)
 345         goto out;
 346
 347     {
 348         krb5_principal principal = NULL;
 349
 350         ret = krb5_ticket_get_server(context, ticket, &principal);
 351         if (ret)
 352             goto out;
 353
 354         ret = krb5_principal_compare(context, sprincipal, principal);
 355         krb5_free_principal(context, principal);
 356         if (ret != TRUE) {
 357             ret = KRB5KDC_ERR_SERVER_NOMATCH;
 358             krb5_set_error_message(context, ret,
 359                                    "User %s used wrong Kx509 service principal",
 360                                    cname);
 361             goto out;
 362         }
 363     }
 364
 365     ret = krb5_auth_con_getkey(context, ac, &key);
 366     if (ret == 0 && key == NULL)
 367         ret = KRB5KDC_ERR_NULL_KEY;
 368     if (ret) {
 369         krb5_set_error_message(context, ret, "Kx509 can't get session key");
 370         goto out;
 371     }
 372
 373     ret = verify_req_hash(context, req, key);
 374     if (ret)
 375         goto out;
 376
 377     /* Verify that the key is encoded RSA key */
 378     {
 379         RSAPublicKey key;
 380         size_t size;
 381
 382         ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
 383                                   &key, &size);
 384         if (ret)
 385             goto out;
 386         free_RSAPublicKey(&key);
 387         if (size != req->pk_key.length) {
 388             ret = ASN1_EXTRA_DATA;
 389             goto out;
 390         }
 391     }
 392
 393     ALLOC(rep.certificate);
 394     if (rep.certificate == NULL)
 395         goto out;
 396     krb5_data_zero(rep.certificate);
 397     ALLOC(rep.hash);
 398     if (rep.hash == NULL)
 399         goto out;
 400     krb5_data_zero(rep.hash);
 401
 402     ret = build_certificate(context, config, &req->pk_key,
 403                             krb5_ticket_get_endtime(context, ticket),
 404                             cprincipal, rep.certificate);
 405     if (ret)
 406         goto out;
 407
 408     ret = calculate_reply_hash(context, key, &rep);
 409     if (ret)
 410         goto out;
 411
 412     /*
 413      * Encode reply, [ version | Kx509Response ]
 414      */
 415
 416     {
 417         krb5_data data;
 418
 419         ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
 420                            &size, ret);
 421         if (ret) {
 422             krb5_set_error_message(context, ret, "Failed to encode kx509 reply");
 423             goto out;
 424         }
 425         if (size != data.length)
 426             krb5_abortx(context, "ASN1 internal error");
 427
 428         ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
 429         if (ret) {
 430             free(data.data);
 431             goto out;
 432         }
 433         memcpy(reply->data, version_2_0, sizeof(version_2_0));
 434         memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
 435                data.data, data.length);
 436         free(data.data);
 437     }
 438
 439     kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
 440
 441 out:
 442     if (ac)
 443         krb5_auth_con_free(context, ac);
 444     if (ret)
 445         krb5_warn(context, ret, "Kx509 request from %s failed", from);
 446     if (ticket)
 447         krb5_free_ticket(context, ticket);
 448     if (id)
 449         krb5_kt_close(context, id);
 450     if (sprincipal)
 451         krb5_free_principal(context, sprincipal);
 452     if (cprincipal)
 453         krb5_free_principal(context, cprincipal);
 454     if (key)
 455         krb5_free_keyblock (context, key);
 456     if (cname)
 457         free(cname);
 458     free_Kx509Response(&rep);
 459
 460     return 0;
 461 }
 462
 463 #endif /* KX509 */