crypto/x509v3/v3_purp.c

   1 /* v3_purp.c */
   2 /* Written by Dr Stephen N Henson (shenson@bigfoot.com) for the OpenSSL
   3  * project 1999.
   4  */
   5 /* ====================================================================
   6  * Copyright (c) 1999 The OpenSSL Project.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  *
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in
  17  *    the documentation and/or other materials provided with the
  18  *    distribution.
  19  *
  20  * 3. All advertising materials mentioning features or use of this
  21  *    software must display the following acknowledgment:
  22  *    "This product includes software developed by the OpenSSL Project
  23  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  24  *
  25  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  26  *    endorse or promote products derived from this software without
  27  *    prior written permission. For written permission, please contact
  28  *    licensing@OpenSSL.org.
  29  *
  30  * 5. Products derived from this software may not be called "OpenSSL"
  31  *    nor may "OpenSSL" appear in their names without prior written
  32  *    permission of the OpenSSL Project.
  33  *
  34  * 6. Redistributions of any form whatsoever must retain the following
  35  *    acknowledgment:
  36  *    "This product includes software developed by the OpenSSL Project
  37  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  38  *
  39  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  40  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  41  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  42  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  43  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  44  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  45  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  46  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  48  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  49  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  50  * OF THE POSSIBILITY OF SUCH DAMAGE.
  51  * ====================================================================
  52  *
  53  * This product includes cryptographic software written by Eric Young
  54  * (eay@cryptsoft.com).  This product includes software written by Tim
  55  * Hudson (tjh@cryptsoft.com).
  56  *
  57  */
  58
  59 #include <stdio.h>
  60 #include "cryptlib.h"
  61 #include <openssl/x509v3.h>
  62 #include <openssl/x509_vfy.h>
  63
  64 static void x509v3_cache_extensions(X509 *x);
  65
  66 static int ca_check(const X509 *x);
  67 static int check_ssl_ca(const X509 *x);
  68 static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca);
  69 static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
  70 static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
  71 static int purpose_smime(const X509 *x, int ca);
  72 static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
  73 static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca);
  74 static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
  75 static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca);
  76 static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca);
  77
  78 static int xp_cmp(const X509_PURPOSE * const *a,
  79                 const X509_PURPOSE * const *b);
  80 static void xptable_free(X509_PURPOSE *p);
  81
  82 static X509_PURPOSE xstandard[] = {
  83         {X509_PURPOSE_SSL_CLIENT, X509_TRUST_SSL_CLIENT, 0, check_purpose_ssl_client, "SSL client", "sslclient", NULL},
  84         {X509_PURPOSE_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ssl_server, "SSL server", "sslserver", NULL},
  85         {X509_PURPOSE_NS_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ns_ssl_server, "Netscape SSL server", "nssslserver", NULL},
  86         {X509_PURPOSE_SMIME_SIGN, X509_TRUST_EMAIL, 0, check_purpose_smime_sign, "S/MIME signing", "smimesign", NULL},
  87         {X509_PURPOSE_SMIME_ENCRYPT, X509_TRUST_EMAIL, 0, check_purpose_smime_encrypt, "S/MIME encryption", "smimeencrypt", NULL},
  88         {X509_PURPOSE_CRL_SIGN, X509_TRUST_COMPAT, 0, check_purpose_crl_sign, "CRL signing", "crlsign", NULL},
  89         {X509_PURPOSE_ANY, X509_TRUST_DEFAULT, 0, no_check, "Any Purpose", "any", NULL},
  90         {X509_PURPOSE_OCSP_HELPER, X509_TRUST_COMPAT, 0, ocsp_helper, "OCSP helper", "ocsphelper", NULL},
  91 };
  92
  93 #define X509_PURPOSE_COUNT (sizeof(xstandard)/sizeof(X509_PURPOSE))
  94
  95 IMPLEMENT_STACK_OF(X509_PURPOSE)
  96
  97 static STACK_OF(X509_PURPOSE) *xptable = NULL;
  98
  99 static int xp_cmp(const X509_PURPOSE * const *a,
 100                 const X509_PURPOSE * const *b)
 101 {
 102         return (*a)->purpose - (*b)->purpose;
 103 }
 104
 105 /* As much as I'd like to make X509_check_purpose use a "const" X509*
 106  * I really can't because it does recalculate hashes and do other non-const
 107  * things. */
 108 int X509_check_purpose(X509 *x, int id, int ca)
 109 {
 110         int idx;
 111         const X509_PURPOSE *pt;
 112         if(!(x->ex_flags & EXFLAG_SET)) {
 113                 CRYPTO_w_lock(CRYPTO_LOCK_X509);
 114                 x509v3_cache_extensions(x);
 115                 CRYPTO_w_unlock(CRYPTO_LOCK_X509);
 116         }
 117         if(id == -1) return 1;
 118         idx = X509_PURPOSE_get_by_id(id);
 119         if(idx == -1) return -1;
 120         pt = X509_PURPOSE_get0(idx);
 121         return pt->check_purpose(pt, x, ca);
 122 }
 123
 124 int X509_PURPOSE_get_count(void)
 125 {
 126         if(!xptable) return X509_PURPOSE_COUNT;
 127         return sk_X509_PURPOSE_num(xptable) + X509_PURPOSE_COUNT;
 128 }
 129
 130 X509_PURPOSE * X509_PURPOSE_get0(int idx)
 131 {
 132         if(idx < 0) return NULL;
 133         if(idx < X509_PURPOSE_COUNT) return xstandard + idx;
 134         return sk_X509_PURPOSE_value(xptable, idx - X509_PURPOSE_COUNT);
 135 }
 136
 137 int X509_PURPOSE_get_by_sname(char *sname)
 138 {
 139         int i;
 140         X509_PURPOSE *xptmp;
 141         for(i = 0; i < X509_PURPOSE_get_count(); i++) {
 142                 xptmp = X509_PURPOSE_get0(i);
 143                 if(!strcmp(xptmp->sname, sname)) return i;
 144         }
 145         return -1;
 146 }
 147
 148 int X509_PURPOSE_get_by_id(int purpose)
 149 {
 150         X509_PURPOSE tmp;
 151         int idx;
 152         if((purpose >= X509_PURPOSE_MIN) && (purpose <= X509_PURPOSE_MAX))
 153                 return purpose - X509_PURPOSE_MIN;
 154         tmp.purpose = purpose;
 155         if(!xptable) return -1;
 156         idx = sk_X509_PURPOSE_find(xptable, &tmp);
 157         if(idx == -1) return -1;
 158         return idx + X509_PURPOSE_COUNT;
 159 }
 160
 161 int X509_PURPOSE_add(int id, int trust, int flags,
 162                         int (*ck)(const X509_PURPOSE *, const X509 *, int),
 163                                         char *name, char *sname, void *arg)
 164 {
 165         int idx;
 166         X509_PURPOSE *ptmp;
 167         /* This is set according to what we change: application can't set it */
 168         flags &= ~X509_PURPOSE_DYNAMIC;
 169         /* This will always be set for application modified trust entries */
 170         flags |= X509_PURPOSE_DYNAMIC_NAME;
 171         /* Get existing entry if any */
 172         idx = X509_PURPOSE_get_by_id(id);
 173         /* Need a new entry */
 174         if(idx == -1) {
 175                 if(!(ptmp = OPENSSL_malloc(sizeof(X509_PURPOSE)))) {
 176                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
 177                         return 0;
 178                 }
 179                 ptmp->flags = X509_PURPOSE_DYNAMIC;
 180         } else ptmp = X509_PURPOSE_get0(idx);
 181
 182         /* OPENSSL_free existing name if dynamic */
 183         if(ptmp->flags & X509_PURPOSE_DYNAMIC_NAME) {
 184                 OPENSSL_free(ptmp->name);
 185                 OPENSSL_free(ptmp->sname);
 186         }
 187         /* dup supplied name */
 188         ptmp->name = BUF_strdup(name);
 189         ptmp->sname = BUF_strdup(sname);
 190         if(!ptmp->name || !ptmp->sname) {
 191                 X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
 192                 return 0;
 193         }
 194         /* Keep the dynamic flag of existing entry */
 195         ptmp->flags &= X509_PURPOSE_DYNAMIC;
 196         /* Set all other flags */
 197         ptmp->flags |= flags;
 198
 199         ptmp->purpose = id;
 200         ptmp->trust = trust;
 201         ptmp->check_purpose = ck;
 202         ptmp->usr_data = arg;
 203
 204         /* If its a new entry manage the dynamic table */
 205         if(idx == -1) {
 206                 if(!xptable && !(xptable = sk_X509_PURPOSE_new(xp_cmp))) {
 207                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
 208                         return 0;
 209                 }
 210                 if (!sk_X509_PURPOSE_push(xptable, ptmp)) {
 211                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
 212                         return 0;
 213                 }
 214         }
 215         return 1;
 216 }
 217
 218 static void xptable_free(X509_PURPOSE *p)
 219         {
 220         if(!p) return;
 221         if (p->flags & X509_PURPOSE_DYNAMIC)
 222                 {
 223                 if (p->flags & X509_PURPOSE_DYNAMIC_NAME) {
 224                         OPENSSL_free(p->name);
 225                         OPENSSL_free(p->sname);
 226                 }
 227                 OPENSSL_free(p);
 228                 }
 229         }
 230
 231 void X509_PURPOSE_cleanup(void)
 232 {
 233         int i;
 234         sk_X509_PURPOSE_pop_free(xptable, xptable_free);
 235         for(i = 0; i < X509_PURPOSE_COUNT; i++) xptable_free(xstandard + i);
 236         xptable = NULL;
 237 }
 238
 239 int X509_PURPOSE_get_id(X509_PURPOSE *xp)
 240 {
 241         return xp->purpose;
 242 }
 243
 244 char *X509_PURPOSE_get0_name(X509_PURPOSE *xp)
 245 {
 246         return xp->name;
 247 }
 248
 249 char *X509_PURPOSE_get0_sname(X509_PURPOSE *xp)
 250 {
 251         return xp->sname;
 252 }
 253
 254 int X509_PURPOSE_get_trust(X509_PURPOSE *xp)
 255 {
 256         return xp->trust;
 257 }
 258
 259 static void x509v3_cache_extensions(X509 *x)
 260 {
 261         BASIC_CONSTRAINTS *bs;
 262         ASN1_BIT_STRING *usage;
 263         ASN1_BIT_STRING *ns;
 264         EXTENDED_KEY_USAGE *extusage;
 265
 266         int i;
 267         if(x->ex_flags & EXFLAG_SET) return;
 268 #ifndef NO_SHA
 269         X509_digest(x, EVP_sha1(), x->sha1_hash, NULL);
 270 #endif
 271         /* Does subject name match issuer ? */
 272         if(!X509_NAME_cmp(X509_get_subject_name(x), X509_get_issuer_name(x)))
 273                          x->ex_flags |= EXFLAG_SS;
 274         /* V1 should mean no extensions ... */
 275         if(!X509_get_version(x)) x->ex_flags |= EXFLAG_V1;
 276         /* Handle basic constraints */
 277         if((bs=X509_get_ext_d2i(x, NID_basic_constraints, NULL, NULL))) {
 278                 if(bs->ca) x->ex_flags |= EXFLAG_CA;
 279                 if(bs->pathlen) {
 280                         if((bs->pathlen->type == V_ASN1_NEG_INTEGER)
 281                                                 || !bs->ca) {
 282                                 x->ex_flags |= EXFLAG_INVALID;
 283                                 x->ex_pathlen = 0;
 284                         } else x->ex_pathlen = ASN1_INTEGER_get(bs->pathlen);
 285                 } else x->ex_pathlen = -1;
 286                 BASIC_CONSTRAINTS_free(bs);
 287                 x->ex_flags |= EXFLAG_BCONS;
 288         }
 289         /* Handle key usage */
 290         if((usage=X509_get_ext_d2i(x, NID_key_usage, NULL, NULL))) {
 291                 if(usage->length > 0) {
 292                         x->ex_kusage = usage->data[0];
 293                         if(usage->length > 1)
 294                                 x->ex_kusage |= usage->data[1] << 8;
 295                 } else x->ex_kusage = 0;
 296                 x->ex_flags |= EXFLAG_KUSAGE;
 297                 ASN1_BIT_STRING_free(usage);
 298         }
 299         x->ex_xkusage = 0;
 300         if((extusage=X509_get_ext_d2i(x, NID_ext_key_usage, NULL, NULL))) {
 301                 x->ex_flags |= EXFLAG_XKUSAGE;
 302                 for(i = 0; i < sk_ASN1_OBJECT_num(extusage); i++) {
 303                         switch(OBJ_obj2nid(sk_ASN1_OBJECT_value(extusage,i))) {
 304                                 case NID_server_auth:
 305                                 x->ex_xkusage |= XKU_SSL_SERVER;
 306                                 break;
 307
 308                                 case NID_client_auth:
 309                                 x->ex_xkusage |= XKU_SSL_CLIENT;
 310                                 break;
 311
 312                                 case NID_email_protect:
 313                                 x->ex_xkusage |= XKU_SMIME;
 314                                 break;
 315
 316                                 case NID_code_sign:
 317                                 x->ex_xkusage |= XKU_CODE_SIGN;
 318                                 break;
 319
 320                                 case NID_ms_sgc:
 321                                 case NID_ns_sgc:
 322                                 x->ex_xkusage |= XKU_SGC;
 323                                 break;
 324
 325                                 case NID_OCSP_sign:
 326                                 x->ex_xkusage |= XKU_OCSP_SIGN;
 327                                 break;
 328
 329                                 case NID_time_stamp:
 330                                 x->ex_xkusage |= XKU_TIMESTAMP;
 331                                 break;
 332                         }
 333                 }
 334                 sk_ASN1_OBJECT_pop_free(extusage, ASN1_OBJECT_free);
 335         }
 336
 337         if((ns=X509_get_ext_d2i(x, NID_netscape_cert_type, NULL, NULL))) {
 338                 if(ns->length > 0) x->ex_nscert = ns->data[0];
 339                 else x->ex_nscert = 0;
 340                 x->ex_flags |= EXFLAG_NSCERT;
 341                 ASN1_BIT_STRING_free(ns);
 342         }
 343         x->skid =X509_get_ext_d2i(x, NID_subject_key_identifier, NULL, NULL);
 344         x->akid =X509_get_ext_d2i(x, NID_authority_key_identifier, NULL, NULL);
 345         x->ex_flags |= EXFLAG_SET;
 346 }
 347
 348 /* CA checks common to all purposes
 349  * return codes:
 350  * 0 not a CA
 351  * 1 is a CA
 352  * 2 basicConstraints absent so "maybe" a CA
 353  * 3 basicConstraints absent but self signed V1.
 354  */
 355
 356 #define V1_ROOT (EXFLAG_V1|EXFLAG_SS)
 357 #define ku_reject(x, usage) \
 358         (((x)->ex_flags & EXFLAG_KUSAGE) && !((x)->ex_kusage & (usage)))
 359 #define xku_reject(x, usage) \
 360         (((x)->ex_flags & EXFLAG_XKUSAGE) && !((x)->ex_xkusage & (usage)))
 361 #define ns_reject(x, usage) \
 362         (((x)->ex_flags & EXFLAG_NSCERT) && !((x)->ex_nscert & (usage)))
 363
 364 static int ca_check(const X509 *x)
 365 {
 366         /* keyUsage if present should allow cert signing */
 367         if(ku_reject(x, KU_KEY_CERT_SIGN)) return 0;
 368         if(x->ex_flags & EXFLAG_BCONS) {
 369                 if(x->ex_flags & EXFLAG_CA) return 1;
 370                 /* If basicConstraints says not a CA then say so */
 371                 else return 0;
 372         } else {
 373                 if((x->ex_flags & V1_ROOT) == V1_ROOT) return 3;
 374                 else return 2;
 375         }
 376 }
 377
 378 /* Check SSL CA: common checks for SSL client and server */
 379 static int check_ssl_ca(const X509 *x)
 380 {
 381         int ca_ret;
 382         ca_ret = ca_check(x);
 383         if(!ca_ret) return 0;
 384         /* check nsCertType if present */
 385         if(x->ex_flags & EXFLAG_NSCERT) {
 386                 if(x->ex_nscert & NS_SSL_CA) return ca_ret;
 387                 return 0;
 388         }
 389         if(ca_ret != 2) return ca_ret;
 390         else return 0;
 391 }
 392
 393
 394 static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca)
 395 {
 396         if(xku_reject(x,XKU_SSL_CLIENT)) return 0;
 397         if(ca) return check_ssl_ca(x);
 398         /* We need to do digital signatures with it */
 399         if(ku_reject(x,KU_DIGITAL_SIGNATURE)) return 0;
 400         /* nsCertType if present should allow SSL client use */
 401         if(ns_reject(x, NS_SSL_CLIENT)) return 0;
 402         return 1;
 403 }
 404
 405 static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
 406 {
 407         if(xku_reject(x,XKU_SSL_SERVER|XKU_SGC)) return 0;
 408         if(ca) return check_ssl_ca(x);
 409
 410         if(ns_reject(x, NS_SSL_SERVER)) return 0;
 411         /* Now as for keyUsage: we'll at least need to sign OR encipher */
 412         if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT)) return 0;
 413
 414         return 1;
 415
 416 }
 417
 418 static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
 419 {
 420         int ret;
 421         ret = check_purpose_ssl_server(xp, x, ca);
 422         if(!ret || ca) return ret;
 423         /* We need to encipher or Netscape complains */
 424         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
 425         return ret;
 426 }
 427
 428 /* common S/MIME checks */
 429 static int purpose_smime(const X509 *x, int ca)
 430 {
 431         if(xku_reject(x,XKU_SMIME)) return 0;
 432         if(ca) {
 433                 int ca_ret;
 434                 ca_ret = ca_check(x);
 435                 if(!ca_ret) return 0;
 436                 /* check nsCertType if present */
 437                 if(x->ex_flags & EXFLAG_NSCERT) {
 438                         if(x->ex_nscert & NS_SMIME_CA) return ca_ret;
 439                         return 0;
 440                 }
 441                 if(ca_ret != 2) return ca_ret;
 442                 else return 0;
 443         }
 444         if(x->ex_flags & EXFLAG_NSCERT) {
 445                 if(x->ex_nscert & NS_SMIME) return 1;
 446                 /* Workaround for some buggy certificates */
 447                 if(x->ex_nscert & NS_SSL_CLIENT) return 2;
 448                 return 0;
 449         }
 450         return 1;
 451 }
 452
 453 static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
 454 {
 455         int ret;
 456         ret = purpose_smime(x, ca);
 457         if(!ret || ca) return ret;
 458         if(ku_reject(x, KU_DIGITAL_SIGNATURE)) return 0;
 459         return ret;
 460 }
 461
 462 static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca)
 463 {
 464         int ret;
 465         ret = purpose_smime(x, ca);
 466         if(!ret || ca) return ret;
 467         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
 468         return ret;
 469 }
 470
 471 static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
 472 {
 473         if(ca) {
 474                 int ca_ret;
 475                 if((ca_ret = ca_check(x)) != 2) return ca_ret;
 476                 else return 0;
 477         }
 478         if(ku_reject(x, KU_CRL_SIGN)) return 0;
 479         return 1;
 480 }
 481
 482 /* OCSP helper: this is *not* a full OCSP check. It just checks that
 483  * each CA is valid. Additional checks must be made on the chain.
 484  */
 485
 486 static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca)
 487 {
 488         /* Must be a valid CA */
 489         if(ca) {
 490                 int ca_ret;
 491                 ca_ret = ca_check(x);
 492                 if(ca_ret != 2) return ca_ret;
 493                 if(x->ex_flags & EXFLAG_NSCERT) {
 494                         if(x->ex_nscert & NS_ANY_CA) return ca_ret;
 495                         return 0;
 496                 }
 497                 return 0;
 498         }
 499         /* leaf certificate is checked in OCSP_verify() */
 500         return 1;
 501 }
 502
 503 static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca)
 504 {
 505         return 1;
 506 }
 507
 508 /* Various checks to see if one certificate issued the second.
 509  * This can be used to prune a set of possible issuer certificates
 510  * which have been looked up using some simple method such as by
 511  * subject name.
 512  * These are:
 513  * 1. Check issuer_name(subject) == subject_name(issuer)
 514  * 2. If akid(subject) exists check it matches issuer
 515  * 3. If key_usage(issuer) exists check it supports certificate signing
 516  * returns 0 for OK, positive for reason for mismatch, reasons match
 517  * codes for X509_verify_cert()
 518  */
 519
 520 int X509_check_issued(X509 *issuer, X509 *subject)
 521 {
 522         if(X509_NAME_cmp(X509_get_subject_name(issuer),
 523                         X509_get_issuer_name(subject)))
 524                                 return X509_V_ERR_SUBJECT_ISSUER_MISMATCH;
 525         x509v3_cache_extensions(issuer);
 526         x509v3_cache_extensions(subject);
 527         if(subject->akid) {
 528                 /* Check key ids (if present) */
 529                 if(subject->akid->keyid && issuer->skid &&
 530                  ASN1_OCTET_STRING_cmp(subject->akid->keyid, issuer->skid) )
 531                                 return X509_V_ERR_AKID_SKID_MISMATCH;
 532                 /* Check serial number */
 533                 if(subject->akid->serial &&
 534                         ASN1_INTEGER_cmp(X509_get_serialNumber(issuer),
 535                                                 subject->akid->serial))
 536                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
 537                 /* Check issuer name */
 538                 if(subject->akid->issuer) {
 539                         /* Ugh, for some peculiar reason AKID includes
 540                          * SEQUENCE OF GeneralName. So look for a DirName.
 541                          * There may be more than one but we only take any
 542                          * notice of the first.
 543                          */
 544                         GENERAL_NAMES *gens;
 545                         GENERAL_NAME *gen;
 546                         X509_NAME *nm = NULL;
 547                         int i;
 548                         gens = subject->akid->issuer;
 549                         for(i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
 550                                 gen = sk_GENERAL_NAME_value(gens, i);
 551                                 if(gen->type == GEN_DIRNAME) {
 552                                         nm = gen->d.dirn;
 553                                         break;
 554                                 }
 555                         }
 556                         if(nm && X509_NAME_cmp(nm, X509_get_issuer_name(issuer)))
 557                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
 558                 }
 559         }
 560         if(ku_reject(issuer, KU_KEY_CERT_SIGN)) return X509_V_ERR_KEYUSAGE_NO_CERTSIGN;
 561         return X509_V_OK;
 562 }
 563