S2N_CLEANUP_RESULT s2n_connection_apply_error_blinding()

in tls/s2n_connection.c [1313:1360]

• 31 lines of code
• 9 McCabe index (conditional complexity)

S2N_CLEANUP_RESULT s2n_connection_apply_error_blinding(struct s2n_connection **conn)
{
    RESULT_ENSURE_REF(conn);
    if (*conn == NULL) {
        return S2N_RESULT_OK;
    }

    /* Ensure that conn->in doesn't contain any leftover invalid or unauthenticated data. */
    RESULT_GUARD_POSIX(s2n_stuffer_wipe(&(*conn)->in));

    int error_code = s2n_errno;
    int error_type = s2n_error_get_type(error_code);

    switch (error_type) {
        case S2N_ERR_T_OK:
            /* Ignore no error */
            return S2N_RESULT_OK;
        case S2N_ERR_T_BLOCKED:
            /* All blocking errors are retriable and should trigger no further action. */
            return S2N_RESULT_OK;
        default:
            break;
    }

    switch (error_code) {
        /* Don't invoke blinding on some of the common errors.
         *
         * Be careful adding new errors here. Disabling blinding for an
         * error that can be triggered by secret / encrypted values can
         * potentially lead to a side channel attack.
         *
         * We may want to someday add an explicit error type for these errors.
         */
        case S2N_ERR_CLOSED:
        case S2N_ERR_CANCELLED:
        case S2N_ERR_CIPHER_NOT_SUPPORTED:
        case S2N_ERR_PROTOCOL_VERSION_UNSUPPORTED:
        case S2N_ERR_CONFIG_NULL_BEFORE_CH_CALLBACK:
            RESULT_GUARD(s2n_connection_set_closed(*conn));
            break;
        default:
            /* Apply blinding to all other errors */
            RESULT_GUARD(s2n_connection_kill(*conn));
            break;
    }

    return S2N_RESULT_OK;
}