/* $OpenBSD: ocsp_vfy.c,v 1.26 2026/04/07 13:02:50 tb Exp $ */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2000.
 */
/* ====================================================================
 * Copyright (c) 2000-2004 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
 *    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 <openssl/ocsp.h>
#include <string.h>

#include "err_local.h"
#include "ocsp_local.h"
#include "x509_local.h"

static int ocsp_find_signer(X509 **psigner, OCSP_BASICRESP *bs,
    STACK_OF(X509) *certs, X509_STORE *st, unsigned long flags);
static X509 *ocsp_find_signer_sk(STACK_OF(X509) *certs, const OCSP_BASICRESP *id);
static int ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain,
    unsigned long flags);
static int ocsp_check_ids(STACK_OF(OCSP_SINGLERESP) *sresp, OCSP_CERTID **ret);
static int ocsp_match_issuerid(X509 *cert, OCSP_CERTID *cid,
    STACK_OF(OCSP_SINGLERESP) *sresp);
static int ocsp_check_delegated(X509 *x, int flags);
static int ocsp_req_find_signer(X509 **psigner, OCSP_REQUEST *req,
    X509_NAME *nm, STACK_OF(X509) *certs, X509_STORE *st,
    unsigned long flags);

/* Verify a basic response message */
int
OCSP_basic_verify(OCSP_BASICRESP *bs, STACK_OF(X509) *certs, X509_STORE *st,
    unsigned long flags)
{
        X509 *signer, *x;
        STACK_OF(X509) *chain = NULL;
        STACK_OF(X509) *untrusted = NULL;
        X509_STORE_CTX ctx;
        int i, ret = 0;

        ret = ocsp_find_signer(&signer, bs, certs, st, flags);
        if (!ret) {
                OCSPerror(OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);
                goto end;
        }
        if ((ret == 2) && (flags & OCSP_TRUSTOTHER))
                flags |= OCSP_NOVERIFY;
        if (!(flags & OCSP_NOSIGS)) {
                EVP_PKEY *skey;

                skey = X509_get0_pubkey(signer);
                if (skey) {
                        ret = OCSP_BASICRESP_verify(bs, skey, 0);
                }
                if (!skey || ret <= 0) {
                        OCSPerror(OCSP_R_SIGNATURE_FAILURE);
                        goto end;
                }
        }
        if (!(flags & OCSP_NOVERIFY)) {
                int init_res;

                if (flags & OCSP_NOCHAIN) {
                        untrusted = NULL;
                } else if (bs->certs && certs) {
                        untrusted = sk_X509_dup(bs->certs);
                        for (i = 0; i < sk_X509_num(certs); i++) {
                                if (!sk_X509_push(untrusted,
                                        sk_X509_value(certs, i))) {
                                        OCSPerror(ERR_R_MALLOC_FAILURE);
                                        goto end;
                                }
                        }
                } else if (certs != NULL) {
                        untrusted = certs;
                } else {
                        untrusted = bs->certs;
                }
                init_res = X509_STORE_CTX_init(&ctx, st, signer, untrusted);
                if (!init_res) {
                        ret = -1;
                        OCSPerror(ERR_R_X509_LIB);
                        goto end;
                }

                if (X509_STORE_CTX_set_purpose(&ctx,
                    X509_PURPOSE_OCSP_HELPER) == 0) {
                        X509_STORE_CTX_cleanup(&ctx);
                        ret = -1;
                        goto end;
                }
                ret = X509_verify_cert(&ctx);
                chain = X509_STORE_CTX_get1_chain(&ctx);
                X509_STORE_CTX_cleanup(&ctx);
                if (ret <= 0) {
                        i = X509_STORE_CTX_get_error(&ctx);
                        OCSPerror(OCSP_R_CERTIFICATE_VERIFY_ERROR);
                        ERR_asprintf_error_data("Verify error:%s",
                            X509_verify_cert_error_string(i));
                        goto end;
                }
                if (flags & OCSP_NOCHECKS) {
                        ret = 1;
                        goto end;
                }
                /* At this point we have a valid certificate chain
                 * need to verify it against the OCSP issuer criteria.
                 */
                ret = ocsp_check_issuer(bs, chain, flags);

                /* If fatal error or valid match then finish */
                if (ret != 0)
                        goto end;

                /* Easy case: explicitly trusted. Get root CA and
                 * check for explicit trust
                 */
                if (flags & OCSP_NOEXPLICIT)
                        goto end;

                x = sk_X509_value(chain, sk_X509_num(chain) - 1);
                if (X509_check_trust(x, X509_TRUST_OCSP_SIGN, 0) !=
                    X509_TRUST_TRUSTED) {
                        OCSPerror(OCSP_R_ROOT_CA_NOT_TRUSTED);
                        goto end;
                }
                ret = 1;
        }

end:
        if (chain)
                sk_X509_pop_free(chain, X509_free);
        if (bs->certs && certs)
                sk_X509_free(untrusted);
        return ret;
}
LCRYPTO_ALIAS(OCSP_basic_verify);

int
OCSP_resp_get0_signer(OCSP_BASICRESP *bs, X509 **signer,
    STACK_OF(X509) *extra_certs)
{
        return ocsp_find_signer(signer, bs, extra_certs, NULL, 0) > 0;
}
LCRYPTO_ALIAS(OCSP_resp_get0_signer);

static int
ocsp_find_signer(X509 **psigner, OCSP_BASICRESP *bs, STACK_OF(X509) *certs,
    X509_STORE *st, unsigned long flags)
{
        X509 *signer;

        if ((signer = ocsp_find_signer_sk(certs, bs))) {
                *psigner = signer;
                return 2;
        }
        if (!(flags & OCSP_NOINTERN) &&
            (signer = ocsp_find_signer_sk(bs->certs, bs))) {
                *psigner = signer;
                return 1;
        }
        /* Maybe lookup from store if by subject name */

        *psigner = NULL;
        return 0;
}

static X509 *
ocsp_find_signer_sk(STACK_OF(X509) *certs, const OCSP_BASICRESP *bs)
{
        const ASN1_OCTET_STRING *byKey = NULL;
        const X509_NAME *byName = NULL;
        const unsigned char *keyhash;
        unsigned char tmphash[SHA_DIGEST_LENGTH];
        X509 *x;
        int i;

        if (!OCSP_resp_get0_id(bs, &byKey, &byName))
                return NULL;

        /* Easy if lookup by name */
        if (byName != NULL)
                return X509_find_by_subject(certs, (X509_NAME *)byName);

        /* Lookup by key hash */

        /* If key hash isn't SHA1 length then forget it */
        if (ASN1_STRING_length(byKey) != SHA_DIGEST_LENGTH)
                return NULL;
        keyhash = ASN1_STRING_get0_data(byKey);
        /* Calculate hash of each key and compare */
        for (i = 0; i < sk_X509_num(certs); i++) {
                x = sk_X509_value(certs, i);
                X509_pubkey_digest(x, EVP_sha1(), tmphash, NULL);
                if (!memcmp(keyhash, tmphash, SHA_DIGEST_LENGTH))
                        return x;
        }
        return NULL;
}

static int
ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain,
    unsigned long flags)
{
        STACK_OF(OCSP_SINGLERESP) *sresp;
        X509 *signer, *sca;
        OCSP_CERTID *caid = NULL;
        int i;

        sresp = bs->tbsResponseData->responses;

        if (sk_X509_num(chain) <= 0) {
                OCSPerror(OCSP_R_NO_CERTIFICATES_IN_CHAIN);
                return -1;
        }

        /* See if the issuer IDs match. */
        i = ocsp_check_ids(sresp, &caid);

        /* If ID mismatch or other error then return */
        if (i <= 0)
                return i;

        signer = sk_X509_value(chain, 0);
        /* Check to see if OCSP responder CA matches request CA */
        if (sk_X509_num(chain) > 1) {
                sca = sk_X509_value(chain, 1);
                i = ocsp_match_issuerid(sca, caid, sresp);
                if (i < 0)
                        return i;
                if (i) {
                        /* We have a match, if extensions OK then success */
                        if (ocsp_check_delegated(signer, flags))
                                return 1;
                        return 0;
                }
        }

        /* Otherwise check if OCSP request signed directly by request CA */
        return ocsp_match_issuerid(signer, caid, sresp);
}

/* Check the issuer certificate IDs for equality. If there is a mismatch with the same
 * algorithm then there's no point trying to match any certificates against the issuer.
 * If the issuer IDs all match then we just need to check equality against one of them.
 */
static int
ocsp_check_ids(STACK_OF(OCSP_SINGLERESP) *sresp, OCSP_CERTID **ret)
{
        OCSP_CERTID *tmpid, *cid;
        int i, idcount;

        idcount = sk_OCSP_SINGLERESP_num(sresp);
        if (idcount <= 0) {
                OCSPerror(OCSP_R_RESPONSE_CONTAINS_NO_REVOCATION_DATA);
                return -1;
        }

        cid = sk_OCSP_SINGLERESP_value(sresp, 0)->certId;

        *ret = NULL;

        for (i = 1; i < idcount; i++) {
                tmpid = sk_OCSP_SINGLERESP_value(sresp, i)->certId;
                /* Check to see if IDs match */
                if (OCSP_id_issuer_cmp(cid, tmpid)) {
                        return 0;
                }
        }

        /* All IDs match: only need to check one ID */
        *ret = cid;
        return 1;
}

static int
ocsp_match_issuerid(X509 *cert, OCSP_CERTID *cid,
    STACK_OF(OCSP_SINGLERESP) *sresp)
{
        /* If only one ID to match then do it */
        if (cid) {
                const EVP_MD *dgst;
                X509_NAME *iname;
                int mdlen;
                unsigned char md[EVP_MAX_MD_SIZE];

                if (!(dgst =
                    EVP_get_digestbyobj(cid->hashAlgorithm->algorithm))) {
                        OCSPerror(OCSP_R_UNKNOWN_MESSAGE_DIGEST);
                        return -1;
                }

                mdlen = EVP_MD_size(dgst);
                if (mdlen < 0)
                        return -1;
                if (cid->issuerNameHash->length != mdlen ||
                    cid->issuerKeyHash->length != mdlen)
                        return 0;
                iname = X509_get_subject_name(cert);
                if (!X509_NAME_digest(iname, dgst, md, NULL))
                        return -1;
                if (memcmp(md, cid->issuerNameHash->data, mdlen))
                        return 0;
                X509_pubkey_digest(cert, dgst, md, NULL);
                if (memcmp(md, cid->issuerKeyHash->data, mdlen))
                        return 0;

                return 1;
        } else {
                /* We have to match the whole lot */
                int i, ret;
                OCSP_CERTID *tmpid;

                for (i = 0; i < sk_OCSP_SINGLERESP_num(sresp); i++) {
                        tmpid = sk_OCSP_SINGLERESP_value(sresp, i)->certId;
                        ret = ocsp_match_issuerid(cert, tmpid, NULL);
                        if (ret <= 0)
                                return ret;
                }
                return 1;
        }
}

static int
ocsp_check_delegated(X509 *x, int flags)
{
        X509_check_purpose(x, -1, 0);
        if ((x->ex_flags & EXFLAG_XKUSAGE) && (x->ex_xkusage & XKU_OCSP_SIGN))
                return 1;
        OCSPerror(OCSP_R_MISSING_OCSPSIGNING_USAGE);
        return 0;
}

/* Verify an OCSP request. This is fortunately much easier than OCSP
 * response verify. Just find the signers certificate and verify it
 * against a given trust value.
 */
int
OCSP_request_verify(OCSP_REQUEST *req, STACK_OF(X509) *certs, X509_STORE *store,
    unsigned long flags)
{
        X509 *signer;
        X509_NAME *nm;
        GENERAL_NAME *gen;
        int ret;
        X509_STORE_CTX ctx;

        if (!req->optionalSignature) {
                OCSPerror(OCSP_R_REQUEST_NOT_SIGNED);
                return 0;
        }
        gen = req->tbsRequest->requestorName;
        if (!gen || gen->type != GEN_DIRNAME) {
                OCSPerror(OCSP_R_UNSUPPORTED_REQUESTORNAME_TYPE);
                return 0;
        }
        nm = gen->d.directoryName;
        ret = ocsp_req_find_signer(&signer, req, nm, certs, store, flags);
        if (ret <= 0) {
                OCSPerror(OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);
                return 0;
        }
        if ((ret == 2) && (flags & OCSP_TRUSTOTHER))
                flags |= OCSP_NOVERIFY;
        if (!(flags & OCSP_NOSIGS)) {
                EVP_PKEY *skey;

                if ((skey = X509_get0_pubkey(signer)) == NULL)
                        return 0;
                ret = OCSP_REQUEST_verify(req, skey);
                if (ret <= 0) {
                        OCSPerror(OCSP_R_SIGNATURE_FAILURE);
                        return 0;
                }
        }
        if (!(flags & OCSP_NOVERIFY)) {
                int init_res;

                if (flags & OCSP_NOCHAIN)
                        init_res = X509_STORE_CTX_init(&ctx, store, signer,
                            NULL);
                else
                        init_res = X509_STORE_CTX_init(&ctx, store, signer,
                            req->optionalSignature->certs);
                if (!init_res) {
                        OCSPerror(ERR_R_X509_LIB);
                        return 0;
                }

                if (X509_STORE_CTX_set_purpose(&ctx,
                      X509_PURPOSE_OCSP_HELPER) == 0 ||
                    X509_STORE_CTX_set_trust(&ctx,
                      X509_TRUST_OCSP_REQUEST) == 0) {
                        X509_STORE_CTX_cleanup(&ctx);
                        return 0;
                }
                ret = X509_verify_cert(&ctx);
                X509_STORE_CTX_cleanup(&ctx);
                if (ret <= 0) {
                        ret = X509_STORE_CTX_get_error(&ctx);
                        OCSPerror(OCSP_R_CERTIFICATE_VERIFY_ERROR);
                        ERR_asprintf_error_data("Verify error:%s",
                            X509_verify_cert_error_string(ret));
                        return 0;
                }
        }
        return 1;
}
LCRYPTO_ALIAS(OCSP_request_verify);

static int
ocsp_req_find_signer(X509 **psigner, OCSP_REQUEST *req, X509_NAME *nm,
    STACK_OF(X509) *certs, X509_STORE *st, unsigned long flags)
{
        X509 *signer;

        if (!(flags & OCSP_NOINTERN)) {
                signer = X509_find_by_subject(req->optionalSignature->certs, nm);
                if (signer) {
                        *psigner = signer;
                        return 1;
                }
        }

        signer = X509_find_by_subject(certs, nm);
        if (signer) {
                *psigner = signer;
                return 2;
        }
        return 0;
}