Added restrictions on the use of proxy certificates, as they may pose
[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 2001.
4  */
5 /* ====================================================================
6  * Copyright (c) 1999-2004 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 check_ssl_ca(const X509 *x);
67 static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca);
68 static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
69 static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
70 static int purpose_smime(const X509 *x, int ca);
71 static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
72 static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca);
73 static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
74 static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca);
75 static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca);
76
77 static int xp_cmp(const X509_PURPOSE * const *a,
78                 const X509_PURPOSE * const *b);
79 static void xptable_free(X509_PURPOSE *p);
80
81 static X509_PURPOSE xstandard[] = {
82         {X509_PURPOSE_SSL_CLIENT, X509_TRUST_SSL_CLIENT, 0, check_purpose_ssl_client, "SSL client", "sslclient", NULL},
83         {X509_PURPOSE_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ssl_server, "SSL server", "sslserver", NULL},
84         {X509_PURPOSE_NS_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ns_ssl_server, "Netscape SSL server", "nssslserver", NULL},
85         {X509_PURPOSE_SMIME_SIGN, X509_TRUST_EMAIL, 0, check_purpose_smime_sign, "S/MIME signing", "smimesign", NULL},
86         {X509_PURPOSE_SMIME_ENCRYPT, X509_TRUST_EMAIL, 0, check_purpose_smime_encrypt, "S/MIME encryption", "smimeencrypt", NULL},
87         {X509_PURPOSE_CRL_SIGN, X509_TRUST_COMPAT, 0, check_purpose_crl_sign, "CRL signing", "crlsign", NULL},
88         {X509_PURPOSE_ANY, X509_TRUST_DEFAULT, 0, no_check, "Any Purpose", "any", NULL},
89         {X509_PURPOSE_OCSP_HELPER, X509_TRUST_COMPAT, 0, ocsp_helper, "OCSP helper", "ocsphelper", NULL},
90 };
91
92 #define X509_PURPOSE_COUNT (sizeof(xstandard)/sizeof(X509_PURPOSE))
93
94 IMPLEMENT_STACK_OF(X509_PURPOSE)
95
96 static STACK_OF(X509_PURPOSE) *xptable = NULL;
97
98 static int xp_cmp(const X509_PURPOSE * const *a,
99                 const X509_PURPOSE * const *b)
100 {
101         return (*a)->purpose - (*b)->purpose;
102 }
103
104 /* As much as I'd like to make X509_check_purpose use a "const" X509*
105  * I really can't because it does recalculate hashes and do other non-const
106  * things. */
107 int X509_check_purpose(X509 *x, int id, int ca)
108 {
109         int idx;
110         const X509_PURPOSE *pt;
111         if(!(x->ex_flags & EXFLAG_SET)) {
112                 CRYPTO_w_lock(CRYPTO_LOCK_X509);
113                 x509v3_cache_extensions(x);
114                 CRYPTO_w_unlock(CRYPTO_LOCK_X509);
115         }
116         if(id == -1) return 1;
117         idx = X509_PURPOSE_get_by_id(id);
118         if(idx == -1) return -1;
119         pt = X509_PURPOSE_get0(idx);
120         return pt->check_purpose(pt, x, ca);
121 }
122
123 int X509_PURPOSE_set(int *p, int purpose)
124 {
125         if(X509_PURPOSE_get_by_id(purpose) == -1) {
126                 X509V3err(X509V3_F_X509_PURPOSE_SET, X509V3_R_INVALID_PURPOSE);
127                 return 0;
128         }
129         *p = purpose;
130         return 1;
131 }
132
133 int X509_PURPOSE_get_count(void)
134 {
135         if(!xptable) return X509_PURPOSE_COUNT;
136         return sk_X509_PURPOSE_num(xptable) + X509_PURPOSE_COUNT;
137 }
138
139 X509_PURPOSE * X509_PURPOSE_get0(int idx)
140 {
141         if(idx < 0) return NULL;
142         if(idx < (int)X509_PURPOSE_COUNT) return xstandard + idx;
143         return sk_X509_PURPOSE_value(xptable, idx - X509_PURPOSE_COUNT);
144 }
145
146 int X509_PURPOSE_get_by_sname(char *sname)
147 {
148         int i;
149         X509_PURPOSE *xptmp;
150         for(i = 0; i < X509_PURPOSE_get_count(); i++) {
151                 xptmp = X509_PURPOSE_get0(i);
152                 if(!strcmp(xptmp->sname, sname)) return i;
153         }
154         return -1;
155 }
156
157 int X509_PURPOSE_get_by_id(int purpose)
158 {
159         X509_PURPOSE tmp;
160         int idx;
161         if((purpose >= X509_PURPOSE_MIN) && (purpose <= X509_PURPOSE_MAX))
162                 return purpose - X509_PURPOSE_MIN;
163         tmp.purpose = purpose;
164         if(!xptable) return -1;
165         idx = sk_X509_PURPOSE_find(xptable, &tmp);
166         if(idx == -1) return -1;
167         return idx + X509_PURPOSE_COUNT;
168 }
169
170 int X509_PURPOSE_add(int id, int trust, int flags,
171                         int (*ck)(const X509_PURPOSE *, const X509 *, int),
172                                         char *name, char *sname, void *arg)
173 {
174         int idx;
175         X509_PURPOSE *ptmp;
176         /* This is set according to what we change: application can't set it */
177         flags &= ~X509_PURPOSE_DYNAMIC;
178         /* This will always be set for application modified trust entries */
179         flags |= X509_PURPOSE_DYNAMIC_NAME;
180         /* Get existing entry if any */
181         idx = X509_PURPOSE_get_by_id(id);
182         /* Need a new entry */
183         if(idx == -1) {
184                 if(!(ptmp = OPENSSL_malloc(sizeof(X509_PURPOSE)))) {
185                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
186                         return 0;
187                 }
188                 ptmp->flags = X509_PURPOSE_DYNAMIC;
189         } else ptmp = X509_PURPOSE_get0(idx);
190
191         /* OPENSSL_free existing name if dynamic */
192         if(ptmp->flags & X509_PURPOSE_DYNAMIC_NAME) {
193                 OPENSSL_free(ptmp->name);
194                 OPENSSL_free(ptmp->sname);
195         }
196         /* dup supplied name */
197         ptmp->name = BUF_strdup(name);
198         ptmp->sname = BUF_strdup(sname);
199         if(!ptmp->name || !ptmp->sname) {
200                 X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
201                 return 0;
202         }
203         /* Keep the dynamic flag of existing entry */
204         ptmp->flags &= X509_PURPOSE_DYNAMIC;
205         /* Set all other flags */
206         ptmp->flags |= flags;
207
208         ptmp->purpose = id;
209         ptmp->trust = trust;
210         ptmp->check_purpose = ck;
211         ptmp->usr_data = arg;
212
213         /* If its a new entry manage the dynamic table */
214         if(idx == -1) {
215                 if(!xptable && !(xptable = sk_X509_PURPOSE_new(xp_cmp))) {
216                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
217                         return 0;
218                 }
219                 if (!sk_X509_PURPOSE_push(xptable, ptmp)) {
220                         X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
221                         return 0;
222                 }
223         }
224         return 1;
225 }
226
227 static void xptable_free(X509_PURPOSE *p)
228         {
229         if(!p) return;
230         if (p->flags & X509_PURPOSE_DYNAMIC) 
231                 {
232                 if (p->flags & X509_PURPOSE_DYNAMIC_NAME) {
233                         OPENSSL_free(p->name);
234                         OPENSSL_free(p->sname);
235                 }
236                 OPENSSL_free(p);
237                 }
238         }
239
240 void X509_PURPOSE_cleanup(void)
241 {
242         unsigned int i;
243         sk_X509_PURPOSE_pop_free(xptable, xptable_free);
244         for(i = 0; i < X509_PURPOSE_COUNT; i++) xptable_free(xstandard + i);
245         xptable = NULL;
246 }
247
248 int X509_PURPOSE_get_id(X509_PURPOSE *xp)
249 {
250         return xp->purpose;
251 }
252
253 char *X509_PURPOSE_get0_name(X509_PURPOSE *xp)
254 {
255         return xp->name;
256 }
257
258 char *X509_PURPOSE_get0_sname(X509_PURPOSE *xp)
259 {
260         return xp->sname;
261 }
262
263 int X509_PURPOSE_get_trust(X509_PURPOSE *xp)
264 {
265         return xp->trust;
266 }
267
268 static int nid_cmp(int *a, int *b)
269         {
270         return *a - *b;
271         }
272
273 int X509_supported_extension(X509_EXTENSION *ex)
274         {
275         /* This table is a list of the NIDs of supported extensions:
276          * that is those which are used by the verify process. If
277          * an extension is critical and doesn't appear in this list
278          * then the verify process will normally reject the certificate.
279          * The list must be kept in numerical order because it will be
280          * searched using bsearch.
281          */
282
283         static int supported_nids[] = {
284                 NID_netscape_cert_type, /* 71 */
285                 NID_key_usage,          /* 83 */
286                 NID_subject_alt_name,   /* 85 */
287                 NID_basic_constraints,  /* 87 */
288                 NID_ext_key_usage,      /* 126 */
289                 NID_proxyCertInfo       /* 661 */
290         };
291
292         int ex_nid;
293
294         ex_nid = OBJ_obj2nid(X509_EXTENSION_get_object(ex));
295
296         if (ex_nid == NID_undef) 
297                 return 0;
298
299         if (OBJ_bsearch((char *)&ex_nid, (char *)supported_nids,
300                 sizeof(supported_nids)/sizeof(int), sizeof(int),
301                 (int (*)(const void *, const void *))nid_cmp))
302                 return 1;
303         return 0;
304         }
305  
306
307 static void x509v3_cache_extensions(X509 *x)
308 {
309         BASIC_CONSTRAINTS *bs;
310         PROXY_CERT_INFO_EXTENSION *pci;
311         ASN1_BIT_STRING *usage;
312         ASN1_BIT_STRING *ns;
313         EXTENDED_KEY_USAGE *extusage;
314         X509_EXTENSION *ex;
315         
316         int i;
317         if(x->ex_flags & EXFLAG_SET) return;
318 #ifndef OPENSSL_NO_SHA
319         X509_digest(x, EVP_sha1(), x->sha1_hash, NULL);
320 #endif
321         /* Does subject name match issuer ? */
322         if(!X509_NAME_cmp(X509_get_subject_name(x), X509_get_issuer_name(x)))
323                          x->ex_flags |= EXFLAG_SS;
324         /* V1 should mean no extensions ... */
325         if(!X509_get_version(x)) x->ex_flags |= EXFLAG_V1;
326         /* Handle basic constraints */
327         if((bs=X509_get_ext_d2i(x, NID_basic_constraints, NULL, NULL))) {
328                 if(bs->ca) x->ex_flags |= EXFLAG_CA;
329                 if(bs->pathlen) {
330                         if((bs->pathlen->type == V_ASN1_NEG_INTEGER)
331                                                 || !bs->ca) {
332                                 x->ex_flags |= EXFLAG_INVALID;
333                                 x->ex_pathlen = 0;
334                         } else x->ex_pathlen = ASN1_INTEGER_get(bs->pathlen);
335                 } else x->ex_pathlen = -1;
336                 BASIC_CONSTRAINTS_free(bs);
337                 x->ex_flags |= EXFLAG_BCONS;
338         }
339         /* Handle proxy certificates */
340         if((pci=X509_get_ext_d2i(x, NID_proxyCertInfo, NULL, NULL))) {
341                 if (x->ex_flags & EXFLAG_CA
342                     || X509_get_ext_by_NID(x, NID_subject_alt_name, 0) >= 0
343                     || X509_get_ext_by_NID(x, NID_issuer_alt_name, 0) >= 0) {
344                         x->ex_flags |= EXFLAG_INVALID;
345                 }
346                 if (pci->pcPathLengthConstraint) {
347                         x->ex_pcpathlen =
348                                 ASN1_INTEGER_get(pci->pcPathLengthConstraint);
349                 } else x->ex_pcpathlen = -1;
350                 PROXY_CERT_INFO_EXTENSION_free(pci);
351                 x->ex_flags |= EXFLAG_PROXY;
352         }
353         /* Handle key usage */
354         if((usage=X509_get_ext_d2i(x, NID_key_usage, NULL, NULL))) {
355                 if(usage->length > 0) {
356                         x->ex_kusage = usage->data[0];
357                         if(usage->length > 1) 
358                                 x->ex_kusage |= usage->data[1] << 8;
359                 } else x->ex_kusage = 0;
360                 x->ex_flags |= EXFLAG_KUSAGE;
361                 ASN1_BIT_STRING_free(usage);
362         }
363         x->ex_xkusage = 0;
364         if((extusage=X509_get_ext_d2i(x, NID_ext_key_usage, NULL, NULL))) {
365                 x->ex_flags |= EXFLAG_XKUSAGE;
366                 for(i = 0; i < sk_ASN1_OBJECT_num(extusage); i++) {
367                         switch(OBJ_obj2nid(sk_ASN1_OBJECT_value(extusage,i))) {
368                                 case NID_server_auth:
369                                 x->ex_xkusage |= XKU_SSL_SERVER;
370                                 break;
371
372                                 case NID_client_auth:
373                                 x->ex_xkusage |= XKU_SSL_CLIENT;
374                                 break;
375
376                                 case NID_email_protect:
377                                 x->ex_xkusage |= XKU_SMIME;
378                                 break;
379
380                                 case NID_code_sign:
381                                 x->ex_xkusage |= XKU_CODE_SIGN;
382                                 break;
383
384                                 case NID_ms_sgc:
385                                 case NID_ns_sgc:
386                                 x->ex_xkusage |= XKU_SGC;
387                                 break;
388
389                                 case NID_OCSP_sign:
390                                 x->ex_xkusage |= XKU_OCSP_SIGN;
391                                 break;
392
393                                 case NID_time_stamp:
394                                 x->ex_xkusage |= XKU_TIMESTAMP;
395                                 break;
396
397                                 case NID_dvcs:
398                                 x->ex_xkusage |= XKU_DVCS;
399                                 break;
400                         }
401                 }
402                 sk_ASN1_OBJECT_pop_free(extusage, ASN1_OBJECT_free);
403         }
404
405         if((ns=X509_get_ext_d2i(x, NID_netscape_cert_type, NULL, NULL))) {
406                 if(ns->length > 0) x->ex_nscert = ns->data[0];
407                 else x->ex_nscert = 0;
408                 x->ex_flags |= EXFLAG_NSCERT;
409                 ASN1_BIT_STRING_free(ns);
410         }
411         x->skid =X509_get_ext_d2i(x, NID_subject_key_identifier, NULL, NULL);
412         x->akid =X509_get_ext_d2i(x, NID_authority_key_identifier, NULL, NULL);
413         for (i = 0; i < X509_get_ext_count(x); i++)
414                 {
415                 ex = X509_get_ext(x, i);
416                 if (!X509_EXTENSION_get_critical(ex))
417                         continue;
418                 if (!X509_supported_extension(ex))
419                         {
420                         x->ex_flags |= EXFLAG_CRITICAL;
421                         break;
422                         }
423                 }
424         x->ex_flags |= EXFLAG_SET;
425 }
426
427 /* CA checks common to all purposes
428  * return codes:
429  * 0 not a CA
430  * 1 is a CA
431  * 2 basicConstraints absent so "maybe" a CA
432  * 3 basicConstraints absent but self signed V1.
433  * 4 basicConstraints absent but keyUsage present and keyCertSign asserted.
434  */
435
436 #define V1_ROOT (EXFLAG_V1|EXFLAG_SS)
437 #define ku_reject(x, usage) \
438         (((x)->ex_flags & EXFLAG_KUSAGE) && !((x)->ex_kusage & (usage)))
439 #define xku_reject(x, usage) \
440         (((x)->ex_flags & EXFLAG_XKUSAGE) && !((x)->ex_xkusage & (usage)))
441 #define ns_reject(x, usage) \
442         (((x)->ex_flags & EXFLAG_NSCERT) && !((x)->ex_nscert & (usage)))
443
444 static int check_ca(const X509 *x)
445 {
446         /* keyUsage if present should allow cert signing */
447         if(ku_reject(x, KU_KEY_CERT_SIGN)) return 0;
448         if(x->ex_flags & EXFLAG_BCONS) {
449                 if(x->ex_flags & EXFLAG_CA) return 1;
450                 /* If basicConstraints says not a CA then say so */
451                 else return 0;
452         } else {
453                 /* we support V1 roots for...  uh, I don't really know why. */
454                 if((x->ex_flags & V1_ROOT) == V1_ROOT) return 3;
455                 /* If key usage present it must have certSign so tolerate it */
456                 else if (x->ex_flags & EXFLAG_KUSAGE) return 4;
457                 /* Older certificates could have Netscape-specific CA types */
458                 else if (x->ex_flags & EXFLAG_NSCERT
459                          && x->ex_nscert & NS_ANY_CA) return 5;
460                 /* can this still be regarded a CA certificate?  I doubt it */
461                 return 0;
462         }
463 }
464
465 int X509_check_ca(X509 *x)
466 {
467         if(!(x->ex_flags & EXFLAG_SET)) {
468                 CRYPTO_w_lock(CRYPTO_LOCK_X509);
469                 x509v3_cache_extensions(x);
470                 CRYPTO_w_unlock(CRYPTO_LOCK_X509);
471         }
472
473         return check_ca(x);
474 }
475
476 /* Check SSL CA: common checks for SSL client and server */
477 static int check_ssl_ca(const X509 *x)
478 {
479         int ca_ret;
480         ca_ret = check_ca(x);
481         if(!ca_ret) return 0;
482         /* check nsCertType if present */
483         if(ca_ret != 5 || x->ex_nscert & NS_SSL_CA) return ca_ret;
484         else return 0;
485 }
486
487
488 static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca)
489 {
490         if(xku_reject(x,XKU_SSL_CLIENT)) return 0;
491         if(ca) return check_ssl_ca(x);
492         /* We need to do digital signatures with it */
493         if(ku_reject(x,KU_DIGITAL_SIGNATURE)) return 0;
494         /* nsCertType if present should allow SSL client use */ 
495         if(ns_reject(x, NS_SSL_CLIENT)) return 0;
496         return 1;
497 }
498
499 static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
500 {
501         if(xku_reject(x,XKU_SSL_SERVER|XKU_SGC)) return 0;
502         if(ca) return check_ssl_ca(x);
503
504         if(ns_reject(x, NS_SSL_SERVER)) return 0;
505         /* Now as for keyUsage: we'll at least need to sign OR encipher */
506         if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT)) return 0;
507         
508         return 1;
509
510 }
511
512 static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
513 {
514         int ret;
515         ret = check_purpose_ssl_server(xp, x, ca);
516         if(!ret || ca) return ret;
517         /* We need to encipher or Netscape complains */
518         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
519         return ret;
520 }
521
522 /* common S/MIME checks */
523 static int purpose_smime(const X509 *x, int ca)
524 {
525         if(xku_reject(x,XKU_SMIME)) return 0;
526         if(ca) {
527                 int ca_ret;
528                 ca_ret = check_ca(x);
529                 if(!ca_ret) return 0;
530                 /* check nsCertType if present */
531                 if(ca_ret != 5 || x->ex_nscert & NS_SMIME_CA) return ca_ret;
532                 else return 0;
533         }
534         if(x->ex_flags & EXFLAG_NSCERT) {
535                 if(x->ex_nscert & NS_SMIME) return 1;
536                 /* Workaround for some buggy certificates */
537                 if(x->ex_nscert & NS_SSL_CLIENT) return 2;
538                 return 0;
539         }
540         return 1;
541 }
542
543 static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
544 {
545         int ret;
546         ret = purpose_smime(x, ca);
547         if(!ret || ca) return ret;
548         if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_NON_REPUDIATION)) return 0;
549         return ret;
550 }
551
552 static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca)
553 {
554         int ret;
555         ret = purpose_smime(x, ca);
556         if(!ret || ca) return ret;
557         if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
558         return ret;
559 }
560
561 static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
562 {
563         if(ca) {
564                 int ca_ret;
565                 if((ca_ret = check_ca(x)) != 2) return ca_ret;
566                 else return 0;
567         }
568         if(ku_reject(x, KU_CRL_SIGN)) return 0;
569         return 1;
570 }
571
572 /* OCSP helper: this is *not* a full OCSP check. It just checks that
573  * each CA is valid. Additional checks must be made on the chain.
574  */
575
576 static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca)
577 {
578         /* Must be a valid CA.  Should we really support the "I don't know"
579            value (2)? */
580         if(ca) return check_ca(x);
581         /* leaf certificate is checked in OCSP_verify() */
582         return 1;
583 }
584
585 static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca)
586 {
587         return 1;
588 }
589
590 /* Various checks to see if one certificate issued the second.
591  * This can be used to prune a set of possible issuer certificates
592  * which have been looked up using some simple method such as by
593  * subject name.
594  * These are:
595  * 1. Check issuer_name(subject) == subject_name(issuer)
596  * 2. If akid(subject) exists check it matches issuer
597  * 3. If key_usage(issuer) exists check it supports certificate signing
598  * returns 0 for OK, positive for reason for mismatch, reasons match
599  * codes for X509_verify_cert()
600  */
601
602 int X509_check_issued(X509 *issuer, X509 *subject)
603 {
604         if(X509_NAME_cmp(X509_get_subject_name(issuer),
605                         X509_get_issuer_name(subject)))
606                                 return X509_V_ERR_SUBJECT_ISSUER_MISMATCH;
607         x509v3_cache_extensions(issuer);
608         x509v3_cache_extensions(subject);
609         if(subject->akid) {
610                 /* Check key ids (if present) */
611                 if(subject->akid->keyid && issuer->skid &&
612                  ASN1_OCTET_STRING_cmp(subject->akid->keyid, issuer->skid) )
613                                 return X509_V_ERR_AKID_SKID_MISMATCH;
614                 /* Check serial number */
615                 if(subject->akid->serial &&
616                         ASN1_INTEGER_cmp(X509_get_serialNumber(issuer),
617                                                 subject->akid->serial))
618                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
619                 /* Check issuer name */
620                 if(subject->akid->issuer) {
621                         /* Ugh, for some peculiar reason AKID includes
622                          * SEQUENCE OF GeneralName. So look for a DirName.
623                          * There may be more than one but we only take any
624                          * notice of the first.
625                          */
626                         GENERAL_NAMES *gens;
627                         GENERAL_NAME *gen;
628                         X509_NAME *nm = NULL;
629                         int i;
630                         gens = subject->akid->issuer;
631                         for(i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
632                                 gen = sk_GENERAL_NAME_value(gens, i);
633                                 if(gen->type == GEN_DIRNAME) {
634                                         nm = gen->d.dirn;
635                                         break;
636                                 }
637                         }
638                         if(nm && X509_NAME_cmp(nm, X509_get_issuer_name(issuer)))
639                                 return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
640                 }
641         }
642         if(subject->ex_flags & EXFLAG_PROXY)
643                 {
644                 if(ku_reject(issuer, KU_DIGITAL_SIGNATURE))
645                         return X509_V_ERR_KEYUSAGE_NO_DIGITAL_SIGNATURE;
646                 }
647         else if(ku_reject(issuer, KU_KEY_CERT_SIGN))
648                 return X509_V_ERR_KEYUSAGE_NO_CERTSIGN;
649         return X509_V_OK;
650 }
651