Tolerate some "variations" used in some
[openssl.git] / 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                 /* If key usage present it must have certSign so tolerate it */
375                 else if (x->ex_flags & EXFLAG_KUSAGE) return 3;
376                 else return 2;
377         }
378 }
379
380 /* Check SSL CA: common checks for SSL client and server */
381 static int check_ssl_ca(const X509 *x)
382 {
383         int ca_ret;
384         ca_ret = ca_check(x);
385         if(!ca_ret) return 0;
386         /* check nsCertType if present */
387         if(x->ex_flags & EXFLAG_NSCERT) {
388                 if(x->ex_nscert & NS_SSL_CA) return ca_ret;
389                 return 0;
390         }
391         if(ca_ret != 2) return ca_ret;
392         else return 0;
393 }
394
395
396 static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca)
397 {
398         if(xku_reject(x,XKU_SSL_CLIENT)) return 0;
399         if(ca) return check_ssl_ca(x);
400         /* We need to do digital signatures with it */
401         if(ku_reject(x,KU_DIGITAL_SIGNATURE)) return 0;
402         /* nsCertType if present should allow SSL client use */ 
403         if(ns_reject(x, NS_SSL_CLIENT)) return 0;
404         return 1;
405 }
406
407 static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
408 {
409         if(xku_reject(x,XKU_SSL_SERVER|XKU_SGC)) return 0;
410         if(ca) return check_ssl_ca(x);
411
412         if(ns_reject(x, NS_SSL_SERVER)) return 0;
413         /* Now as for keyUsage: we'll at least need to sign OR encipher */
414         if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT)) return 0;
415         
416         return 1;
417
418 }
419
420 static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
421 {
422         int ret;
423         ret = check_purpose_ssl_server(xp, x, ca);
424         if(!ret || ca) return ret;
425         /* We need to encipher or Netscape complains */
426         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
427         return ret;
428 }
429
430 /* common S/MIME checks */
431 static int purpose_smime(const X509 *x, int ca)
432 {
433         if(xku_reject(x,XKU_SMIME)) return 0;
434         if(ca) {
435                 int ca_ret;
436                 ca_ret = ca_check(x);
437                 if(!ca_ret) return 0;
438                 /* check nsCertType if present */
439                 if(x->ex_flags & EXFLAG_NSCERT) {
440                         if(x->ex_nscert & NS_SMIME_CA) return ca_ret;
441                         return 0;
442                 }
443                 if(ca_ret != 2) return ca_ret;
444                 else return 0;
445         }
446         if(x->ex_flags & EXFLAG_NSCERT) {
447                 if(x->ex_nscert & NS_SMIME) return 1;
448                 /* Workaround for some buggy certificates */
449                 if(x->ex_nscert & NS_SSL_CLIENT) return 2;
450                 return 0;
451         }
452         return 1;
453 }
454
455 static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
456 {
457         int ret;
458         ret = purpose_smime(x, ca);
459         if(!ret || ca) return ret;
460         if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_NON_REPUDIATION)) return 0;
461         return ret;
462 }
463
464 static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca)
465 {
466         int ret;
467         ret = purpose_smime(x, ca);
468         if(!ret || ca) return ret;
469         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
470         return ret;
471 }
472
473 static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
474 {
475         if(ca) {
476                 int ca_ret;
477                 if((ca_ret = ca_check(x)) != 2) return ca_ret;
478                 else return 0;
479         }
480         if(ku_reject(x, KU_CRL_SIGN)) return 0;
481         return 1;
482 }
483
484 /* OCSP helper: this is *not* a full OCSP check. It just checks that
485  * each CA is valid. Additional checks must be made on the chain.
486  */
487
488 static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca)
489 {
490         /* Must be a valid CA */
491         if(ca) {
492                 int ca_ret;
493                 ca_ret = ca_check(x);
494                 if(ca_ret != 2) return ca_ret;
495                 if(x->ex_flags & EXFLAG_NSCERT) {
496                         if(x->ex_nscert & NS_ANY_CA) return ca_ret;
497                         return 0;
498                 }
499                 return 0;
500         }
501         /* leaf certificate is checked in OCSP_verify() */
502         return 1;
503 }
504
505 static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca)
506 {
507         return 1;
508 }
509
510 /* Various checks to see if one certificate issued the second.
511  * This can be used to prune a set of possible issuer certificates
512  * which have been looked up using some simple method such as by
513  * subject name.
514  * These are:
515  * 1. Check issuer_name(subject) == subject_name(issuer)
516  * 2. If akid(subject) exists check it matches issuer
517  * 3. If key_usage(issuer) exists check it supports certificate signing
518  * returns 0 for OK, positive for reason for mismatch, reasons match
519  * codes for X509_verify_cert()
520  */
521
522 int X509_check_issued(X509 *issuer, X509 *subject)
523 {
524         if(X509_NAME_cmp(X509_get_subject_name(issuer),
525                         X509_get_issuer_name(subject)))
526                                 return X509_V_ERR_SUBJECT_ISSUER_MISMATCH;
527         x509v3_cache_extensions(issuer);
528         x509v3_cache_extensions(subject);
529         if(subject->akid) {
530                 /* Check key ids (if present) */
531                 if(subject->akid->keyid && issuer->skid &&
532                  ASN1_OCTET_STRING_cmp(subject->akid->keyid, issuer->skid) )
533                                 return X509_V_ERR_AKID_SKID_MISMATCH;
534                 /* Check serial number */
535                 if(subject->akid->serial &&
536                         ASN1_INTEGER_cmp(X509_get_serialNumber(issuer),
537                                                 subject->akid->serial))
538                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
539                 /* Check issuer name */
540                 if(subject->akid->issuer) {
541                         /* Ugh, for some peculiar reason AKID includes
542                          * SEQUENCE OF GeneralName. So look for a DirName.
543                          * There may be more than one but we only take any
544                          * notice of the first.
545                          */
546                         GENERAL_NAMES *gens;
547                         GENERAL_NAME *gen;
548                         X509_NAME *nm = NULL;
549                         int i;
550                         gens = subject->akid->issuer;
551                         for(i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
552                                 gen = sk_GENERAL_NAME_value(gens, i);
553                                 if(gen->type == GEN_DIRNAME) {
554                                         nm = gen->d.dirn;
555                                         break;
556                                 }
557                         }
558                         if(nm && X509_NAME_cmp(nm, X509_get_issuer_name(issuer)))
559                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
560                 }
561         }
562         if(ku_reject(issuer, KU_KEY_CERT_SIGN)) return X509_V_ERR_KEYUSAGE_NO_CERTSIGN;
563         return X509_V_OK;
564 }
565