int s2n_prf_server_finished()

in tls/s2n_prf.c [672:728]

• 49 lines of code
• 5 McCabe index (conditional complexity)

int s2n_prf_server_finished(struct s2n_connection *conn)
{
    POSIX_ENSURE_REF(conn);
    POSIX_ENSURE_REF(conn->secure);
    POSIX_ENSURE_REF(conn->handshake.hashes);

    struct s2n_blob master_secret, md5, sha;
    uint8_t md5_digest[MD5_DIGEST_LENGTH];
    uint8_t sha_digest[SHA384_DIGEST_LENGTH];
    uint8_t server_finished_label[] = "server finished";
    struct s2n_blob server_finished = { 0 };
    struct s2n_blob label = { 0 };

    if (conn->actual_protocol_version == S2N_SSLv3) {
        return s2n_prf_sslv3_server_finished(conn);
    }

    server_finished.data = conn->handshake.server_finished;
    server_finished.size = S2N_TLS_FINISHED_LEN;
    POSIX_GUARD_RESULT(s2n_handshake_set_finished_len(conn, server_finished.size));
    label.data = server_finished_label;
    label.size = sizeof(server_finished_label) - 1;

    master_secret.data = conn->secrets.version.tls12.master_secret;
    master_secret.size = sizeof(conn->secrets.version.tls12.master_secret);
    if (conn->actual_protocol_version == S2N_TLS12) {
        switch (conn->secure->cipher_suite->prf_alg) {
            case S2N_HMAC_SHA256:
                POSIX_GUARD(s2n_hash_copy(&conn->handshake.hashes->hash_workspace, &conn->handshake.hashes->sha256));
                POSIX_GUARD(s2n_hash_digest(&conn->handshake.hashes->hash_workspace, sha_digest, SHA256_DIGEST_LENGTH));
                sha.size = SHA256_DIGEST_LENGTH;
                break;
            case S2N_HMAC_SHA384:
                POSIX_GUARD(s2n_hash_copy(&conn->handshake.hashes->hash_workspace, &conn->handshake.hashes->sha384));
                POSIX_GUARD(s2n_hash_digest(&conn->handshake.hashes->hash_workspace, sha_digest, SHA384_DIGEST_LENGTH));
                sha.size = SHA384_DIGEST_LENGTH;
                break;
            default:
                POSIX_BAIL(S2N_ERR_PRF_INVALID_ALGORITHM);
        }

        sha.data = sha_digest;
        return s2n_prf(conn, &master_secret, &label, &sha, NULL, NULL, &server_finished);
    }

    POSIX_GUARD(s2n_hash_copy(&conn->handshake.hashes->hash_workspace, &conn->handshake.hashes->md5));
    POSIX_GUARD(s2n_hash_digest(&conn->handshake.hashes->hash_workspace, md5_digest, MD5_DIGEST_LENGTH));
    md5.data = md5_digest;
    md5.size = MD5_DIGEST_LENGTH;

    POSIX_GUARD(s2n_hash_copy(&conn->handshake.hashes->hash_workspace, &conn->handshake.hashes->sha1));
    POSIX_GUARD(s2n_hash_digest(&conn->handshake.hashes->hash_workspace, sha_digest, SHA_DIGEST_LENGTH));
    sha.data = sha_digest;
    sha.size = SHA_DIGEST_LENGTH;

    return s2n_prf(conn, &master_secret, &label, &md5, &sha, NULL, &server_finished);
}