1 files changed, 629 insertions, 0 deletions

diff --git a/src/lib/libcrypto/x509v3/v3_purp.c b/src/lib/libcrypto/x509v3/v3_purp.c
new file mode 100644
index 0000000000..4d145f71fd
--- /dev/null
+++ b/src/lib/libcrypto/x509v3/v3_purp.c
@@ -0,0 +1,629 @@
+/* v3_purp.c */
+/* Written by Dr Stephen N Henson (shenson@bigfoot.com) for the OpenSSL
+ * project 2001.
+ */
+/* ====================================================================
+ * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer. 
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    licensing@OpenSSL.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
+
+#include <stdio.h>
+#include "cryptlib.h"
+#include <openssl/x509v3.h>
+#include <openssl/x509_vfy.h>
+
+static void x509v3_cache_extensions(X509 *x);
+
+static int ca_check(const X509 *x);
+static int check_ssl_ca(const X509 *x);
+static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int purpose_smime(const X509 *x, int ca);
+static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca);
+static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca);
+
+static int xp_cmp(const X509_PURPOSE * const *a,
+                const X509_PURPOSE * const *b);
+static void xptable_free(X509_PURPOSE *p);
+
+static X509_PURPOSE xstandard[] = {
+        {X509_PURPOSE_SSL_CLIENT, X509_TRUST_SSL_CLIENT, 0, check_purpose_ssl_client, "SSL client", "sslclient", NULL},
+        {X509_PURPOSE_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ssl_server, "SSL server", "sslserver", NULL},
+        {X509_PURPOSE_NS_SSL_SERVER, X509_TRUST_SSL_SERVER, 0, check_purpose_ns_ssl_server, "Netscape SSL server", "nssslserver", NULL},
+        {X509_PURPOSE_SMIME_SIGN, X509_TRUST_EMAIL, 0, check_purpose_smime_sign, "S/MIME signing", "smimesign", NULL},
+        {X509_PURPOSE_SMIME_ENCRYPT, X509_TRUST_EMAIL, 0, check_purpose_smime_encrypt, "S/MIME encryption", "smimeencrypt", NULL},
+        {X509_PURPOSE_CRL_SIGN, X509_TRUST_COMPAT, 0, check_purpose_crl_sign, "CRL signing", "crlsign", NULL},
+        {X509_PURPOSE_ANY, X509_TRUST_DEFAULT, 0, no_check, "Any Purpose", "any", NULL},
+        {X509_PURPOSE_OCSP_HELPER, X509_TRUST_COMPAT, 0, ocsp_helper, "OCSP helper", "ocsphelper", NULL},
+};
+
+#define X509_PURPOSE_COUNT (sizeof(xstandard)/sizeof(X509_PURPOSE))
+
+IMPLEMENT_STACK_OF(X509_PURPOSE)
+
+static STACK_OF(X509_PURPOSE) *xptable = NULL;
+
+static int xp_cmp(const X509_PURPOSE * const *a,
+                const X509_PURPOSE * const *b)
+{
+        return (*a)->purpose - (*b)->purpose;
+}
+
+/* As much as I'd like to make X509_check_purpose use a "const" X509*
+ * I really can't because it does recalculate hashes and do other non-const
+ * things. */
+int X509_check_purpose(X509 *x, int id, int ca)
+{
+        int idx;
+        const X509_PURPOSE *pt;
+        if(!(x->ex_flags & EXFLAG_SET)) {
+                CRYPTO_w_lock(CRYPTO_LOCK_X509);
+                x509v3_cache_extensions(x);
+                CRYPTO_w_unlock(CRYPTO_LOCK_X509);
+        }
+        if(id == -1) return 1;
+        idx = X509_PURPOSE_get_by_id(id);
+        if(idx == -1) return -1;
+        pt = X509_PURPOSE_get0(idx);
+        return pt->check_purpose(pt, x, ca);
+}
+
+int X509_PURPOSE_set(int *p, int purpose)
+{
+        if(X509_PURPOSE_get_by_id(purpose) == -1) {
+                X509V3err(X509V3_F_X509_PURPOSE_SET, X509V3_R_INVALID_PURPOSE);
+                return 0;
+        }
+        *p = purpose;
+        return 1;
+}
+
+int X509_PURPOSE_get_count(void)
+{
+        if(!xptable) return X509_PURPOSE_COUNT;
+        return sk_X509_PURPOSE_num(xptable) + X509_PURPOSE_COUNT;
+}
+
+X509_PURPOSE * X509_PURPOSE_get0(int idx)
+{
+        if(idx < 0) return NULL;
+        if(idx < X509_PURPOSE_COUNT) return xstandard + idx;
+        return sk_X509_PURPOSE_value(xptable, idx - X509_PURPOSE_COUNT);
+}
+
+int X509_PURPOSE_get_by_sname(char *sname)
+{
+        int i;
+        X509_PURPOSE *xptmp;
+        for(i = 0; i < X509_PURPOSE_get_count(); i++) {
+                xptmp = X509_PURPOSE_get0(i);
+                if(!strcmp(xptmp->sname, sname)) return i;
+        }
+        return -1;
+}
+
+int X509_PURPOSE_get_by_id(int purpose)
+{
+        X509_PURPOSE tmp;
+        int idx;
+        if((purpose >= X509_PURPOSE_MIN) && (purpose <= X509_PURPOSE_MAX))
+                return purpose - X509_PURPOSE_MIN;
+        tmp.purpose = purpose;
+        if(!xptable) return -1;
+        idx = sk_X509_PURPOSE_find(xptable, &tmp);
+        if(idx == -1) return -1;
+        return idx + X509_PURPOSE_COUNT;
+}
+
+int X509_PURPOSE_add(int id, int trust, int flags,
+                        int (*ck)(const X509_PURPOSE *, const X509 *, int),
+                                        char *name, char *sname, void *arg)
+{
+        int idx;
+        X509_PURPOSE *ptmp;
+        /* This is set according to what we change: application can't set it */
+        flags &= ~X509_PURPOSE_DYNAMIC;
+        /* This will always be set for application modified trust entries */
+        flags |= X509_PURPOSE_DYNAMIC_NAME;
+        /* Get existing entry if any */
+        idx = X509_PURPOSE_get_by_id(id);
+        /* Need a new entry */
+        if(idx == -1) {
+                if(!(ptmp = OPENSSL_malloc(sizeof(X509_PURPOSE)))) {
+                        X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
+                        return 0;
+                }
+                ptmp->flags = X509_PURPOSE_DYNAMIC;
+        } else ptmp = X509_PURPOSE_get0(idx);
+
+        /* OPENSSL_free existing name if dynamic */
+        if(ptmp->flags & X509_PURPOSE_DYNAMIC_NAME) {
+                OPENSSL_free(ptmp->name);
+                OPENSSL_free(ptmp->sname);
+        }
+        /* dup supplied name */
+        ptmp->name = BUF_strdup(name);
+        ptmp->sname = BUF_strdup(sname);
+        if(!ptmp->name || !ptmp->sname) {
+                X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
+                return 0;
+        }
+        /* Keep the dynamic flag of existing entry */
+        ptmp->flags &= X509_PURPOSE_DYNAMIC;
+        /* Set all other flags */
+        ptmp->flags |= flags;
+
+        ptmp->purpose = id;
+        ptmp->trust = trust;
+        ptmp->check_purpose = ck;
+        ptmp->usr_data = arg;
+
+        /* If its a new entry manage the dynamic table */
+        if(idx == -1) {
+                if(!xptable && !(xptable = sk_X509_PURPOSE_new(xp_cmp))) {
+                        X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
+                        return 0;
+                }
+                if (!sk_X509_PURPOSE_push(xptable, ptmp)) {
+                        X509V3err(X509V3_F_X509_PURPOSE_ADD,ERR_R_MALLOC_FAILURE);
+                        return 0;
+                }
+        }
+        return 1;
+}
+
+static void xptable_free(X509_PURPOSE *p)
+        {
+        if(!p) return;
+        if (p->flags & X509_PURPOSE_DYNAMIC) 
+                {
+                if (p->flags & X509_PURPOSE_DYNAMIC_NAME) {
+                        OPENSSL_free(p->name);
+                        OPENSSL_free(p->sname);
+                }
+                OPENSSL_free(p);
+                }
+        }
+
+void X509_PURPOSE_cleanup(void)
+{
+        int i;
+        sk_X509_PURPOSE_pop_free(xptable, xptable_free);
+        for(i = 0; i < X509_PURPOSE_COUNT; i++) xptable_free(xstandard + i);
+        xptable = NULL;
+}
+
+int X509_PURPOSE_get_id(X509_PURPOSE *xp)
+{
+        return xp->purpose;
+}
+
+char *X509_PURPOSE_get0_name(X509_PURPOSE *xp)
+{
+        return xp->name;
+}
+
+char *X509_PURPOSE_get0_sname(X509_PURPOSE *xp)
+{
+        return xp->sname;
+}
+
+int X509_PURPOSE_get_trust(X509_PURPOSE *xp)
+{
+        return xp->trust;
+}
+
+static int nid_cmp(int *a, int *b)
+        {
+        return *a - *b;
+        }
+
+int X509_supported_extension(X509_EXTENSION *ex)
+        {
+        /* This table is a list of the NIDs of supported extensions:
+         * that is those which are used by the verify process. If
+         * an extension is critical and doesn't appear in this list
+         * then the verify process will normally reject the certificate.
+         * The list must be kept in numerical order because it will be
+         * searched using bsearch.
+         */
+
+        static int supported_nids[] = {
+                NID_netscape_cert_type, /* 71 */
+                NID_key_usage,          /* 83 */
+                NID_subject_alt_name,   /* 85 */
+                NID_basic_constraints,  /* 87 */
+                NID_ext_key_usage       /* 126 */
+        };
+
+        int ex_nid;
+
+        ex_nid = OBJ_obj2nid(X509_EXTENSION_get_object(ex));
+
+        if (ex_nid == NID_undef) 
+                return 0;
+
+        if (OBJ_bsearch((char *)&ex_nid, (char *)supported_nids,
+                sizeof(supported_nids)/sizeof(int), sizeof(int),
+                (int (*)(const void *, const void *))nid_cmp))
+                return 1;
+        return 0;
+        }
+ 
+
+static void x509v3_cache_extensions(X509 *x)
+{
+        BASIC_CONSTRAINTS *bs;
+        ASN1_BIT_STRING *usage;
+        ASN1_BIT_STRING *ns;
+        EXTENDED_KEY_USAGE *extusage;
+        X509_EXTENSION *ex;
+        
+        int i;
+        if(x->ex_flags & EXFLAG_SET) return;
+#ifndef OPENSSL_NO_SHA
+        X509_digest(x, EVP_sha1(), x->sha1_hash, NULL);
+#endif
+        /* Does subject name match issuer ? */
+        if(!X509_NAME_cmp(X509_get_subject_name(x), X509_get_issuer_name(x)))
+                         x->ex_flags |= EXFLAG_SS;
+        /* V1 should mean no extensions ... */
+        if(!X509_get_version(x)) x->ex_flags |= EXFLAG_V1;
+        /* Handle basic constraints */
+        if((bs=X509_get_ext_d2i(x, NID_basic_constraints, NULL, NULL))) {
+                if(bs->ca) x->ex_flags |= EXFLAG_CA;
+                if(bs->pathlen) {
+                        if((bs->pathlen->type == V_ASN1_NEG_INTEGER)
+                                                || !bs->ca) {
+                                x->ex_flags |= EXFLAG_INVALID;
+                                x->ex_pathlen = 0;
+                        } else x->ex_pathlen = ASN1_INTEGER_get(bs->pathlen);
+                } else x->ex_pathlen = -1;
+                BASIC_CONSTRAINTS_free(bs);
+                x->ex_flags |= EXFLAG_BCONS;
+        }
+        /* Handle key usage */
+        if((usage=X509_get_ext_d2i(x, NID_key_usage, NULL, NULL))) {
+                if(usage->length > 0) {
+                        x->ex_kusage = usage->data[0];
+                        if(usage->length > 1) 
+                                x->ex_kusage |= usage->data[1] << 8;
+                } else x->ex_kusage = 0;
+                x->ex_flags |= EXFLAG_KUSAGE;
+                ASN1_BIT_STRING_free(usage);
+        }
+        x->ex_xkusage = 0;
+        if((extusage=X509_get_ext_d2i(x, NID_ext_key_usage, NULL, NULL))) {
+                x->ex_flags |= EXFLAG_XKUSAGE;
+                for(i = 0; i < sk_ASN1_OBJECT_num(extusage); i++) {
+                        switch(OBJ_obj2nid(sk_ASN1_OBJECT_value(extusage,i))) {
+                                case NID_server_auth:
+                                x->ex_xkusage |= XKU_SSL_SERVER;
+                                break;
+
+                                case NID_client_auth:
+                                x->ex_xkusage |= XKU_SSL_CLIENT;
+                                break;
+
+                                case NID_email_protect:
+                                x->ex_xkusage |= XKU_SMIME;
+                                break;
+
+                                case NID_code_sign:
+                                x->ex_xkusage |= XKU_CODE_SIGN;
+                                break;
+
+                                case NID_ms_sgc:
+                                case NID_ns_sgc:
+                                x->ex_xkusage |= XKU_SGC;
+                                break;
+
+                                case NID_OCSP_sign:
+                                x->ex_xkusage |= XKU_OCSP_SIGN;
+                                break;
+
+                                case NID_time_stamp:
+                                x->ex_xkusage |= XKU_TIMESTAMP;
+                                break;
+
+                                case NID_dvcs:
+                                x->ex_xkusage |= XKU_DVCS;
+                                break;
+                        }
+                }
+                sk_ASN1_OBJECT_pop_free(extusage, ASN1_OBJECT_free);
+        }
+
+        if((ns=X509_get_ext_d2i(x, NID_netscape_cert_type, NULL, NULL))) {
+                if(ns->length > 0) x->ex_nscert = ns->data[0];
+                else x->ex_nscert = 0;
+                x->ex_flags |= EXFLAG_NSCERT;
+                ASN1_BIT_STRING_free(ns);
+        }
+        x->skid =X509_get_ext_d2i(x, NID_subject_key_identifier, NULL, NULL);
+        x->akid =X509_get_ext_d2i(x, NID_authority_key_identifier, NULL, NULL);
+        for (i = 0; i < X509_get_ext_count(x); i++)
+                {
+                ex = X509_get_ext(x, i);
+                if (!X509_EXTENSION_get_critical(ex))
+                        continue;
+                if (!X509_supported_extension(ex))
+                        {
+                        x->ex_flags |= EXFLAG_CRITICAL;
+                        break;
+                        }
+                }
+        x->ex_flags |= EXFLAG_SET;
+}
+
+/* CA checks common to all purposes
+ * return codes:
+ * 0 not a CA
+ * 1 is a CA
+ * 2 basicConstraints absent so "maybe" a CA
+ * 3 basicConstraints absent but self signed V1.
+ */
+
+#define V1_ROOT (EXFLAG_V1|EXFLAG_SS)
+#define ku_reject(x, usage) \
+        (((x)->ex_flags & EXFLAG_KUSAGE) && !((x)->ex_kusage & (usage)))
+#define xku_reject(x, usage) \
+        (((x)->ex_flags & EXFLAG_XKUSAGE) && !((x)->ex_xkusage & (usage)))
+#define ns_reject(x, usage) \
+        (((x)->ex_flags & EXFLAG_NSCERT) && !((x)->ex_nscert & (usage)))
+
+static int ca_check(const X509 *x)
+{
+        /* keyUsage if present should allow cert signing */
+        if(ku_reject(x, KU_KEY_CERT_SIGN)) return 0;
+        if(x->ex_flags & EXFLAG_BCONS) {
+                if(x->ex_flags & EXFLAG_CA) return 1;
+                /* If basicConstraints says not a CA then say so */
+                else return 0;
+        } else {
+                if((x->ex_flags & V1_ROOT) == V1_ROOT) return 3;
+                /* If key usage present it must have certSign so tolerate it */
+                else if (x->ex_flags & EXFLAG_KUSAGE) return 3;
+                else return 2;
+        }
+}
+
+/* Check SSL CA: common checks for SSL client and server */
+static int check_ssl_ca(const X509 *x)
+{
+        int ca_ret;
+        ca_ret = ca_check(x);
+        if(!ca_ret) return 0;
+        /* check nsCertType if present */
+        if(x->ex_flags & EXFLAG_NSCERT) {
+                if(x->ex_nscert & NS_SSL_CA) return ca_ret;
+                return 0;
+        }
+        if(ca_ret != 2) return ca_ret;
+        else return 0;
+}
+
+
+static int check_purpose_ssl_client(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        if(xku_reject(x,XKU_SSL_CLIENT)) return 0;
+        if(ca) return check_ssl_ca(x);
+        /* We need to do digital signatures with it */
+        if(ku_reject(x,KU_DIGITAL_SIGNATURE)) return 0;
+        /* nsCertType if present should allow SSL client use */ 
+        if(ns_reject(x, NS_SSL_CLIENT)) return 0;
+        return 1;
+}
+
+static int check_purpose_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        if(xku_reject(x,XKU_SSL_SERVER|XKU_SGC)) return 0;
+        if(ca) return check_ssl_ca(x);
+
+        if(ns_reject(x, NS_SSL_SERVER)) return 0;
+        /* Now as for keyUsage: we'll at least need to sign OR encipher */
+        if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT)) return 0;
+        
+        return 1;
+
+}
+
+static int check_purpose_ns_ssl_server(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        int ret;
+        ret = check_purpose_ssl_server(xp, x, ca);
+        if(!ret || ca) return ret;
+        /* We need to encipher or Netscape complains */
+        if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
+        return ret;
+}
+
+/* common S/MIME checks */
+static int purpose_smime(const X509 *x, int ca)
+{
+        if(xku_reject(x,XKU_SMIME)) return 0;
+        if(ca) {
+                int ca_ret;
+                ca_ret = ca_check(x);
+                if(!ca_ret) return 0;
+                /* check nsCertType if present */
+                if(x->ex_flags & EXFLAG_NSCERT) {
+                        if(x->ex_nscert & NS_SMIME_CA) return ca_ret;
+                        return 0;
+                }
+                if(ca_ret != 2) return ca_ret;
+                else return 0;
+        }
+        if(x->ex_flags & EXFLAG_NSCERT) {
+                if(x->ex_nscert & NS_SMIME) return 1;
+                /* Workaround for some buggy certificates */
+                if(x->ex_nscert & NS_SSL_CLIENT) return 2;
+                return 0;
+        }
+        return 1;
+}
+
+static int check_purpose_smime_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        int ret;
+        ret = purpose_smime(x, ca);
+        if(!ret || ca) return ret;
+        if(ku_reject(x, KU_DIGITAL_SIGNATURE|KU_NON_REPUDIATION)) return 0;
+        return ret;
+}
+
+static int check_purpose_smime_encrypt(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        int ret;
+        ret = purpose_smime(x, ca);
+        if(!ret || ca) return ret;
+        if(ku_reject(x, KU_KEY_ENCIPHERMENT)) return 0;
+        return ret;
+}
+
+static int check_purpose_crl_sign(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        if(ca) {
+                int ca_ret;
+                if((ca_ret = ca_check(x)) != 2) return ca_ret;
+                else return 0;
+        }
+        if(ku_reject(x, KU_CRL_SIGN)) return 0;
+        return 1;
+}
+
+/* OCSP helper: this is *not* a full OCSP check. It just checks that
+ * each CA is valid. Additional checks must be made on the chain.
+ */
+
+static int ocsp_helper(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        /* Must be a valid CA */
+        if(ca) {
+                int ca_ret;
+                ca_ret = ca_check(x);
+                if(ca_ret != 2) return ca_ret;
+                if(x->ex_flags & EXFLAG_NSCERT) {
+                        if(x->ex_nscert & NS_ANY_CA) return ca_ret;
+                        return 0;
+                }
+                return 0;
+        }
+        /* leaf certificate is checked in OCSP_verify() */
+        return 1;
+}
+
+static int no_check(const X509_PURPOSE *xp, const X509 *x, int ca)
+{
+        return 1;
+}
+
+/* Various checks to see if one certificate issued the second.
+ * This can be used to prune a set of possible issuer certificates
+ * which have been looked up using some simple method such as by
+ * subject name.
+ * These are:
+ * 1. Check issuer_name(subject) == subject_name(issuer)
+ * 2. If akid(subject) exists check it matches issuer
+ * 3. If key_usage(issuer) exists check it supports certificate signing
+ * returns 0 for OK, positive for reason for mismatch, reasons match
+ * codes for X509_verify_cert()
+ */
+
+int X509_check_issued(X509 *issuer, X509 *subject)
+{
+        if(X509_NAME_cmp(X509_get_subject_name(issuer),
+                        X509_get_issuer_name(subject)))
+                                return X509_V_ERR_SUBJECT_ISSUER_MISMATCH;
+        x509v3_cache_extensions(issuer);
+        x509v3_cache_extensions(subject);
+        if(subject->akid) {
+                /* Check key ids (if present) */
+                if(subject->akid->keyid && issuer->skid &&
+                 ASN1_OCTET_STRING_cmp(subject->akid->keyid, issuer->skid) )
+                                return X509_V_ERR_AKID_SKID_MISMATCH;
+                /* Check serial number */
+                if(subject->akid->serial &&
+                        ASN1_INTEGER_cmp(X509_get_serialNumber(issuer),
+                                                subject->akid->serial))
+                                return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
+                /* Check issuer name */
+                if(subject->akid->issuer) {
+                        /* Ugh, for some peculiar reason AKID includes
+                         * SEQUENCE OF GeneralName. So look for a DirName.
+                         * There may be more than one but we only take any
+                         * notice of the first.
+                         */
+                        GENERAL_NAMES *gens;
+                        GENERAL_NAME *gen;
+                        X509_NAME *nm = NULL;
+                        int i;
+                        gens = subject->akid->issuer;
+                        for(i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
+                                gen = sk_GENERAL_NAME_value(gens, i);
+                                if(gen->type == GEN_DIRNAME) {
+                                        nm = gen->d.dirn;
+                                        break;
+                                }
+                        }
+                        if(nm && X509_NAME_cmp(nm, X509_get_issuer_name(issuer)))
+                                return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
+                }
+        }
+        if(ku_reject(issuer, KU_KEY_CERT_SIGN)) return X509_V_ERR_KEYUSAGE_NO_CERTSIGN;
+        return X509_V_OK;
+}
+