AUTH_MAGIC
if ((r = sshbuf_put(encoded, AUTH_MAGIC, sizeof(AUTH_MAGIC))) != 0 ||
if (sshbuf_len(decoded) < sizeof(AUTH_MAGIC) ||
memcmp(sshbuf_ptr(decoded), AUTH_MAGIC, sizeof(AUTH_MAGIC))) {
if ((r = sshbuf_consume(decoded, sizeof(AUTH_MAGIC))) != 0 ||
if ((r = sshbuf_consume(decoded, sizeof(AUTH_MAGIC))) != 0 ||