/* Provenance: openssl/openssl tls1_check_sig_alg (fixed).
 * repo: openssl/openssl
 * commit: a87f3fe01a5a894aa27ccd6a239155fd129988e4
 * parent: 3656c08ab4b1b892730cb5e808b6f4298b08a2e6
 * commit_url: https://github.com/openssl/openssl/commit/a87f3fe01a5a894aa27ccd6a239155fd129988e4
 * cve: CVE-2020-1967
 * license: OpenSSL License
 * function: tls1_check_sig_alg
 * relpath: ssl/t1_lib.c
 */

static int tls1_check_sig_alg(SSL *s, X509 *x, int default_nid)
{
    int sig_nid, use_pc_sigalgs = 0;
    size_t i;
    const SIGALG_LOOKUP *sigalg;
    size_t sigalgslen;
    if (default_nid == -1)
        return 1;
    sig_nid = X509_get_signature_nid(x);
    if (default_nid)
        return sig_nid == default_nid ? 1 : 0;

    if (SSL_IS_TLS13(s) && s->s3.tmp.peer_cert_sigalgs != NULL) {
        /*
         * If we're in TLSv1.3 then we only get here if we're checking the
         * chain. If the peer has specified peer_cert_sigalgs then we use them
         * otherwise we default to normal sigalgs.
         */
        sigalgslen = s->s3.tmp.peer_cert_sigalgslen;
        use_pc_sigalgs = 1;
    } else {
        sigalgslen = s->shared_sigalgslen;
    }
    for (i = 0; i < sigalgslen; i++) {
        sigalg = use_pc_sigalgs
                 ? tls1_lookup_sigalg(s->s3.tmp.peer_cert_sigalgs[i])
                 : s->shared_sigalgs[i];
        if (sigalg != NULL && sig_nid == sigalg->sigandhash)
            return 1;
    }
    return 0;
}