/*

 * Copyright 2001-2024 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <string.h>

#include <openssl/ocsp.h>

#include <openssl/err.h>

#include "internal/sizes.h"

#include "ocsp_local.h"

static int ocsp_find_signer(const X509 **psigner, OCSP_BASICRESP *bs,

    const STACK_OF(X509) *certs, unsigned long flags);

static const X509 *ocsp_find_signer_sk(const STACK_OF(X509) *certs, OCSP_RESPID *id);

static int ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain);

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);

static int ocsp_req_find_signer(const X509 **psigner, OCSP_REQUEST *req,

    const X509_NAME *nm, const STACK_OF(X509) *certs,

    unsigned long flags);

/* Returns 1 on success, 0 on failure, or -1 on fatal error */

static int ocsp_verify_signer(const X509 *signer, int response,

    X509_STORE *st, unsigned long flags,

    STACK_OF(X509) *untrusted, STACK_OF(X509) **chain)

{

    X509_STORE_CTX *ctx = X509_STORE_CTX_new();

    X509_VERIFY_PARAM *vp;

    int ret = -1;

    if (ctx == NULL) {

        ERR_raise(ERR_LIB_OCSP, ERR_R_X509_LIB);

        goto end;

    }

    /*

     * TODO: The cast below can be dropped when #30076 lands

     */

    if (!X509_STORE_CTX_init(ctx, st, (X509 *)signer, untrusted)) {

        ERR_raise(ERR_LIB_OCSP, ERR_R_X509_LIB);

        goto end;

    }

    if ((vp = X509_STORE_CTX_get0_param(ctx)) == NULL)

        goto end;

    if ((flags & OCSP_PARTIAL_CHAIN) != 0)

        X509_VERIFY_PARAM_set_flags(vp, X509_V_FLAG_PARTIAL_CHAIN);

    if (response

        && X509_get_ext_by_NID(signer, NID_id_pkix_OCSP_noCheck, -1) >= 0)

        /*

         * Locally disable revocation status checking for OCSP responder cert.

         * Done here for CRLs; should be done also for OCSP-based checks.

         */

        X509_VERIFY_PARAM_clear_flags(vp, X509_V_FLAG_CRL_CHECK);

    X509_STORE_CTX_set_purpose(ctx, X509_PURPOSE_OCSP_HELPER);

    X509_STORE_CTX_set_trust(ctx, X509_TRUST_OCSP_REQUEST);

    ret = X509_verify_cert(ctx);

    if (ret <= 0) {

        int err = X509_STORE_CTX_get_error(ctx);

        ERR_raise_data(ERR_LIB_OCSP, OCSP_R_CERTIFICATE_VERIFY_ERROR,

            "Verify error: %s", X509_verify_cert_error_string(err));

        goto end;

    }

    if (chain != NULL)

        *chain = X509_STORE_CTX_get1_chain(ctx);

end:

    X509_STORE_CTX_free(ctx);

    return ret;

}

static int ocsp_verify(OCSP_REQUEST *req, OCSP_BASICRESP *bs,

    const X509 *signer, unsigned long flags)

{

    EVP_PKEY *skey;

    int ret = 1;

    if ((flags & OCSP_NOSIGS) == 0) {

        if ((skey = X509_get0_pubkey(signer)) == NULL) {

            ERR_raise(ERR_LIB_OCSP, OCSP_R_NO_SIGNER_KEY);

            return -1;

        }

        if (req != NULL)

            ret = OCSP_REQUEST_verify(req, skey, signer->libctx, signer->propq);

        else

            ret = OCSP_BASICRESP_verify(bs, skey, signer->libctx, signer->propq);

        if (ret <= 0)

            ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNATURE_FAILURE);

    }

    return ret;

}

/* Verify a basic response message */

int OCSP_basic_verify(OCSP_BASICRESP *bs, const STACK_OF(X509) *certs,

    X509_STORE *st, unsigned long flags)

{

    const X509 *signer, *x;

    STACK_OF(X509) *chain = NULL;

    STACK_OF(X509) *untrusted = NULL;

    int ret = ocsp_find_signer(&signer, bs, certs, flags);

    if (ret == 0) {

        ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);

        goto end;

    }

    if ((ret == 2) && (flags & OCSP_TRUSTOTHER) != 0)

        flags |= OCSP_NOVERIFY;

    if ((ret = ocsp_verify(NULL, bs, signer, flags)) <= 0)

        goto end;

    if ((flags & OCSP_NOVERIFY) == 0) {

        ret = -1;

        if ((flags & OCSP_NOCHAIN) == 0) {

            if ((untrusted = sk_X509_dup(bs->certs)) == NULL)

                goto end;

            if (!X509_add_certs(untrusted, certs, X509_ADD_FLAG_DEFAULT))

                goto end;

        }

        ret = ocsp_verify_signer(signer, 1, st, flags, untrusted, &chain);

        if (ret <= 0)

            goto end;

        if ((flags & OCSP_NOCHECKS) != 0) {

            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);

        /* 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) != 0)

            goto end;

        x = sk_X509_value(chain, sk_X509_num(chain) - 1);

        /*

         * TODO: Cast below can be dropped when #30071 lands

         */

        if (X509_check_trust((X509 *)x, NID_OCSP_sign, 0) != X509_TRUST_TRUSTED) {

            ERR_raise(ERR_LIB_OCSP, OCSP_R_ROOT_CA_NOT_TRUSTED);

            ret = 0;

            goto end;

        }

        ret = 1;

    }

end:

    OSSL_STACK_OF_X509_free(chain);

    sk_X509_free(untrusted);

    return ret;

}

int OCSP_resp_get0_signer(OCSP_BASICRESP *bs, const X509 **signer,

    const STACK_OF(X509) *extra_certs)

{

    return ocsp_find_signer(signer, bs, extra_certs, 0) > 0;

}

static int ocsp_find_signer(const X509 **psigner, OCSP_BASICRESP *bs,

    const STACK_OF(X509) *certs, unsigned long flags)

{

    const X509 *signer;

    OCSP_RESPID *rid = &bs->tbsResponseData.responderId;

    if ((signer = ocsp_find_signer_sk(certs, rid)) != NULL) {

        *psigner = signer;

        return 2;

    }

    if ((flags & OCSP_NOINTERN) == 0 && (signer = ocsp_find_signer_sk(bs->certs, rid))) {

        *psigner = signer;

        return 1;

    }

    /* Maybe lookup from store if by subject name */

    *psigner = NULL;

    return 0;

}

static const X509 *ocsp_find_signer_sk(const STACK_OF(X509) *certs, OCSP_RESPID *id)

{

    int i, r;

    unsigned char tmphash[SHA_DIGEST_LENGTH], *keyhash;

    EVP_MD *md;

    X509 *x;

    /* Easy if lookup by name */

    if (id->type == V_OCSP_RESPID_NAME)

        return X509_find_by_subject(certs, id->value.byName);

    /* Lookup by key hash */

    /* If key hash isn't SHA1 length then forget it */

    if (id->value.byKey->length != SHA_DIGEST_LENGTH)

        return NULL;

    keyhash = id->value.byKey->data;

    /* Calculate hash of each key and compare */

    for (i = 0; i < sk_X509_num(certs); i++) {

        if ((x = sk_X509_value(certs, i)) != NULL) {

            if ((md = EVP_MD_fetch(x->libctx, SN_sha1, x->propq)) == NULL)

                break;

            r = X509_pubkey_digest(x, md, tmphash, NULL);

            EVP_MD_free(md);

            if (!r)

                break;

            if (memcmp(keyhash, tmphash, SHA_DIGEST_LENGTH) == 0)

                return x;

        }

    }

    return NULL;

}

static int ocsp_check_issuer(OCSP_BASICRESP *bs, STACK_OF(X509) *chain)

{

    STACK_OF(OCSP_SINGLERESP) *sresp = bs->tbsResponseData.responses;

    X509 *signer, *sca;

    OCSP_CERTID *caid = NULL;

    int ret;

    if (sk_X509_num(chain) <= 0) {

        ERR_raise(ERR_LIB_OCSP, OCSP_R_NO_CERTIFICATES_IN_CHAIN);

        return -1;

    }

    /* See if the issuer IDs match. */

    ret = ocsp_check_ids(sresp, &caid);

    /* If ID mismatch or other error then return */

    if (ret <= 0)

        return ret;

    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);

        ret = ocsp_match_issuerid(sca, caid, sresp);

        if (ret < 0)

            return ret;

        if (ret != 0) {

            /* We have a match, if extensions OK then success */

            if (ocsp_check_delegated(signer))

                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) {

        ERR_raise(ERR_LIB_OCSP, 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)) {

            /* If algorithm mismatch let caller deal with it */

            if (OBJ_cmp(tmpid->hashAlgorithm.algorithm,

                    cid->hashAlgorithm.algorithm))

                return 2;

            /* Else mismatch */

            return 0;

        }

    }

    /* All IDs match: only need to check one ID */

    *ret = cid;

    return 1;

}

/*

 * Match the certificate issuer ID.

 * Returns -1 on fatal error, 0 if there is no match and 1 if there is a match.

 */

static int ocsp_match_issuerid(X509 *cert, OCSP_CERTID *cid,

    STACK_OF(OCSP_SINGLERESP) *sresp)

{

    int ret = -1;

    EVP_MD *dgst = NULL;

    /* If only one ID to match then do it */

    if (cid != NULL) {

        char name[OSSL_MAX_NAME_SIZE];

        const X509_NAME *iname;

        int mdlen;

        unsigned char md[EVP_MAX_MD_SIZE];

        OBJ_obj2txt(name, sizeof(name), cid->hashAlgorithm.algorithm, 0);

        dgst = EVP_MD_fetch(NULL, name, NULL);

        if (dgst == NULL) {

            ERR_raise(ERR_LIB_OCSP, OCSP_R_UNKNOWN_MESSAGE_DIGEST);

            goto end;

        }

        mdlen = EVP_MD_get_size(dgst);

        if (mdlen <= 0) {

            ERR_raise(ERR_LIB_OCSP, OCSP_R_DIGEST_SIZE_ERR);

            goto end;

        }

        if (cid->issuerNameHash.length != mdlen || cid->issuerKeyHash.length != mdlen) {

            ret = 0;

            goto end;

        }

        iname = X509_get_subject_name(cert);

        if (!X509_NAME_digest(iname, dgst, md, NULL))

            goto end;

        if (memcmp(md, cid->issuerNameHash.data, mdlen) != 0) {

            ret = 0;

            goto end;

        }

        if (!X509_pubkey_digest(cert, dgst, md, NULL)) {

            ERR_raise(ERR_LIB_OCSP, OCSP_R_DIGEST_ERR);

            goto end;

        }

        ret = memcmp(md, cid->issuerKeyHash.data, mdlen) == 0;

        goto end;

    } else {

        /* We have to match the whole lot */

        int i;

        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;

end:

    EVP_MD_free(dgst);

    return ret;

}

static int ocsp_check_delegated(X509 *x)

{

    if ((X509_get_extension_flags(x) & EXFLAG_XKUSAGE)

        && (X509_get_extended_key_usage(x) & XKU_OCSP_SIGN))

        return 1;

    ERR_raise(ERR_LIB_OCSP, OCSP_R_MISSING_OCSPSIGNING_USAGE);

    return 0;

}

/*

 * Verify an OCSP request. This is much easier than OCSP response verify.

 * Just find the signer's certificate and verify it against a given trust value.

 * Returns 1 on success, 0 on failure and on fatal error.

 */

int OCSP_request_verify(OCSP_REQUEST *req, const STACK_OF(X509) *certs,

    X509_STORE *store, unsigned long flags)

{

    const X509 *signer;

    const X509_NAME *nm;

    GENERAL_NAME *gen;

    int ret;

    if (!req->optionalSignature) {

        ERR_raise(ERR_LIB_OCSP, OCSP_R_REQUEST_NOT_SIGNED);

        return 0;

    }

    gen = req->tbsRequest.requestorName;

    if (!gen || gen->type != GEN_DIRNAME) {

        ERR_raise(ERR_LIB_OCSP, OCSP_R_UNSUPPORTED_REQUESTORNAME_TYPE);

        return 0; /* not returning -1 here for backward compatibility*/

    }

    nm = gen->d.directoryName;

    ret = ocsp_req_find_signer(&signer, req, nm, certs, flags);

    if (ret <= 0) {

        ERR_raise(ERR_LIB_OCSP, OCSP_R_SIGNER_CERTIFICATE_NOT_FOUND);

        return 0; /* not returning -1 here for backward compatibility*/

    }

    if ((ret == 2) && (flags & OCSP_TRUSTOTHER) != 0)

        flags |= OCSP_NOVERIFY;

    if ((ret = ocsp_verify(req, NULL, signer, flags)) <= 0)

        return 0; /* not returning 'ret' here for backward compatibility*/

    if ((flags & OCSP_NOVERIFY) != 0)

        return 1;

    return ocsp_verify_signer(signer, 0, store, flags,

               (flags & OCSP_NOCHAIN) != 0 ? NULL : req->optionalSignature->certs, NULL)

        > 0;

    /* using '> 0' here to avoid breaking backward compatibility returning -1 */

}

static int ocsp_req_find_signer(const X509 **psigner, OCSP_REQUEST *req,

    const X509_NAME *nm, const STACK_OF(X509) *certs,

    unsigned long flags)

{

    const X509 *signer;

    if ((flags & OCSP_NOINTERN) == 0) {

        signer = X509_find_by_subject(req->optionalSignature->certs, nm);

        if (signer != NULL) {

            *psigner = signer;

            return 1;

        }

    }

    if ((signer = X509_find_by_subject(certs, nm)) != NULL) {

        *psigner = signer;

        return 2;

    }

    return 0;

}