v3_purp.c

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/* v3_purp.c */
/* Written by Dr Stephen N Henson ([email protected]) for the OpenSSL
 * project 2001.
 */
/* ====================================================================
 * Copyright (c) 1999-2004 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
 *    [email protected].
 *
 * 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
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */

#include <stdio.h>
#include "cryptlib.h"
#include <openssl/x509v3.h>
#include <openssl/x509_vfy.h>

static void x509v3_cache_extensions(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 check_purpose_timestamp_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},
    {X509_PURPOSE_TIMESTAMP_SIGN, X509_TRUST_TSA, 0, check_purpose_timestamp_sign, "Time Stamp signing", "timestampsign", 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 < (int)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)
{
    unsigned 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(const int *a, const int *b)
    {
    return *a - *b;
    }

DECLARE_OBJ_BSEARCH_CMP_FN(int, int, nid);
IMPLEMENT_OBJ_BSEARCH_CMP_FN(int, int, nid);

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 const int supported_nids[] = {
        NID_netscape_cert_type, /* 71 */
            NID_key_usage,      /* 83 */
        NID_subject_alt_name,   /* 85 */
        NID_basic_constraints,  /* 87 */
        NID_certificate_policies, /* 89 */
            NID_ext_key_usage,  /* 126 */
#ifndef OPENSSL_NO_RFC3779
        NID_sbgp_ipAddrBlock,   /* 290 */
        NID_sbgp_autonomousSysNum, /* 291 */
#endif
        NID_policy_constraints, /* 401 */
        NID_proxyCertInfo,  /* 663 */
        NID_name_constraints,   /* 666 */
        NID_policy_mappings,    /* 747 */
        NID_inhibit_any_policy  /* 748 */
    };

    int ex_nid = OBJ_obj2nid(X509_EXTENSION_get_object(ex));

    if (ex_nid == NID_undef) 
        return 0;

    if (OBJ_bsearch_nid(&ex_nid, supported_nids,
            sizeof(supported_nids)/sizeof(int)))
        return 1;
    return 0;
    }

static void setup_dp(X509 *x, DIST_POINT *dp)
    {
    X509_NAME *iname = NULL;
    int i;
    if (dp->reasons)
        {
        if (dp->reasons->length > 0)
            dp->dp_reasons = dp->reasons->data[0];
        if (dp->reasons->length > 1)
            dp->dp_reasons |= (dp->reasons->data[1] << 8);
        dp->dp_reasons &= CRLDP_ALL_REASONS;
        }
    else
        dp->dp_reasons = CRLDP_ALL_REASONS;
    if (!dp->distpoint || (dp->distpoint->type != 1))
        return;
    for (i = 0; i < sk_GENERAL_NAME_num(dp->CRLissuer); i++)
        {
        GENERAL_NAME *gen = sk_GENERAL_NAME_value(dp->CRLissuer, i);
        if (gen->type == GEN_DIRNAME)
            {
            iname = gen->d.directoryName;
            break;
            }
        }
    if (!iname)
        iname = X509_get_issuer_name(x);

    DIST_POINT_set_dpname(dp->distpoint, iname);

    }

static void setup_crldp(X509 *x)
    {
    int i;
    x->crldp = X509_get_ext_d2i(x, NID_crl_distribution_points, NULL, NULL);
    for (i = 0; i < sk_DIST_POINT_num(x->crldp); i++)
        setup_dp(x, sk_DIST_POINT_value(x->crldp, i));
    }

static void x509v3_cache_extensions(X509 *x)
{
    BASIC_CONSTRAINTS *bs;
    PROXY_CERT_INFO_EXTENSION *pci;
    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_SI;
    /* 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 proxy certificates */
    if((pci=X509_get_ext_d2i(x, NID_proxyCertInfo, NULL, NULL))) {
        if (x->ex_flags & EXFLAG_CA
            || X509_get_ext_by_NID(x, NID_subject_alt_name, 0) >= 0
            || X509_get_ext_by_NID(x, NID_issuer_alt_name, 0) >= 0) {
            x->ex_flags |= EXFLAG_INVALID;
        }
        if (pci->pcPathLengthConstraint) {
            x->ex_pcpathlen =
                ASN1_INTEGER_get(pci->pcPathLengthConstraint);
        } else x->ex_pcpathlen = -1;
        PROXY_CERT_INFO_EXTENSION_free(pci);
        x->ex_flags |= EXFLAG_PROXY;
    }
    /* 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);
    x->altname = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);
    x->nc = X509_get_ext_d2i(x, NID_name_constraints, &i, NULL);
    if (!x->nc && (i != -1))
        x->ex_flags |= EXFLAG_INVALID;
    setup_crldp(x);

#ifndef OPENSSL_NO_RFC3779
    x->rfc3779_addr =X509_get_ext_d2i(x, NID_sbgp_ipAddrBlock, NULL, NULL);
    x->rfc3779_asid =X509_get_ext_d2i(x, NID_sbgp_autonomousSysNum,
                      NULL, NULL);
#endif
    for (i = 0; i < X509_get_ext_count(x); i++)
        {
        ex = X509_get_ext(x, i);
        if (!X509_EXTENSION_get_critical(ex))
            continue;
        if (OBJ_obj2nid(X509_EXTENSION_get_object(ex))
                    == NID_freshest_crl)
            x->ex_flags |= EXFLAG_FRESHEST;
        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.
 * 4 basicConstraints absent but keyUsage present and keyCertSign asserted.
 */

#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 check_ca(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 {
        /* we support V1 roots for...  uh, I don't really know why. */
        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 4;
        /* Older certificates could have Netscape-specific CA types */
        else if (x->ex_flags & EXFLAG_NSCERT
             && x->ex_nscert & NS_ANY_CA) return 5;
        /* can this still be regarded a CA certificate?  I doubt it */
        return 0;
    }
}

int X509_check_ca(X509 *x)
{
    if(!(x->ex_flags & EXFLAG_SET)) {
        CRYPTO_w_lock(CRYPTO_LOCK_X509);
        x509v3_cache_extensions(x);
        CRYPTO_w_unlock(CRYPTO_LOCK_X509);
    }

    return check_ca(x);
}

/* Check SSL CA: common checks for SSL client and server */
static int check_ssl_ca(const X509 *x)
{
    int ca_ret;
    ca_ret = check_ca(x);
    if(!ca_ret) return 0;
    /* check nsCertType if present */
    if(ca_ret != 5 || x->ex_nscert & NS_SSL_CA) 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 = check_ca(x);
        if(!ca_ret) return 0;
        /* check nsCertType if present */
        if(ca_ret != 5 || x->ex_nscert & NS_SMIME_CA) 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 = check_ca(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.  Should we really support the "I don't know"
       value (2)? */
    if(ca) return check_ca(x);
    /* leaf certificate is checked in OCSP_verify() */
    return 1;
}

static int check_purpose_timestamp_sign(const X509_PURPOSE *xp, const X509 *x,
                    int ca)
{
    int i_ext;

    /* If ca is true we must return if this is a valid CA certificate. */
    if (ca) return check_ca(x);

    /* 
     * Check the optional key usage field:
     * if Key Usage is present, it must be one of digitalSignature 
     * and/or nonRepudiation (other values are not consistent and shall
     * be rejected).
     */
    if ((x->ex_flags & EXFLAG_KUSAGE)
        && ((x->ex_kusage & ~(KU_NON_REPUDIATION | KU_DIGITAL_SIGNATURE)) ||
        !(x->ex_kusage & (KU_NON_REPUDIATION | KU_DIGITAL_SIGNATURE))))
        return 0;

    /* Only time stamp key usage is permitted and it's required. */
    if (!(x->ex_flags & EXFLAG_XKUSAGE) || x->ex_xkusage != XKU_TIMESTAMP)
        return 0;

    /* Extended Key Usage MUST be critical */
    i_ext = X509_get_ext_by_NID((X509 *) x, NID_ext_key_usage, 0);
    if (i_ext >= 0)
        {
        X509_EXTENSION *ext = X509_get_ext((X509 *) x, i_ext);
        if (!X509_EXTENSION_get_critical(ext))
            return 0;
        }

    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)
        {
        int ret = X509_check_akid(issuer, subject->akid);
        if (ret != X509_V_OK)
            return ret;
        }

    if(subject->ex_flags & EXFLAG_PROXY)
        {
        if(ku_reject(issuer, KU_DIGITAL_SIGNATURE))
            return X509_V_ERR_KEYUSAGE_NO_DIGITAL_SIGNATURE;
        }
    else if(ku_reject(issuer, KU_KEY_CERT_SIGN))
        return X509_V_ERR_KEYUSAGE_NO_CERTSIGN;
    return X509_V_OK;
}

int X509_check_akid(X509 *issuer, AUTHORITY_KEYID *akid)
    {

    if(!akid)
        return X509_V_OK;

    /* Check key ids (if present) */
    if(akid->keyid && issuer->skid &&
         ASN1_OCTET_STRING_cmp(akid->keyid, issuer->skid) )
                return X509_V_ERR_AKID_SKID_MISMATCH;
    /* Check serial number */
    if(akid->serial &&
        ASN1_INTEGER_cmp(X509_get_serialNumber(issuer), akid->serial))
                return X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH;
    /* Check issuer name */
    if(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 = 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;
        }
    return X509_V_OK;
    }