sshbuf_dtob64_string
if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL)
if ((b64 = sshbuf_dtob64_string(b, 1)) == NULL)
char *sshbuf_dtob64_string(const struct sshbuf *buf, int wrap);
if ((uu = sshbuf_dtob64_string(b, 0)) == NULL) {