smtp does not accept EHLO keywords in lowercase

[MegaManSec]

I did this

RFC5321 states that " Although EHLO keywords may be specified in upper, lower, or mixedcase, they MUST always be recognized and processed in a case-insensitive manner. " (src)

curl does not do this, and works with only uppercase:

curl/lib/smtp.c

Lines 992 to 1056 in af7d67d

	if(len >= 8 && !memcmp(line, "STARTTLS", 8))
	smtpc->tls_supported = TRUE;
	/* Does the server support the SIZE capability? */
	else if(len >= 4 && !memcmp(line, "SIZE", 4))
	smtpc->size_supported = TRUE;
	/* Does the server support the UTF-8 capability? */
	else if(len >= 8 && !memcmp(line, "SMTPUTF8", 8))
	smtpc->utf8_supported = TRUE;
	/* Does the server support authentication? */
	else if(len >= 5 && !memcmp(line, "AUTH ", 5)) {
	smtpc->auth_supported = TRUE;
	/* Advance past the AUTH keyword */
	line += 5;
	len -= 5;
	/* Loop through the data line */
	for(;;) {
	size_t llen;
	size_t wordlen;
	unsigned short mechbit;
	while(len &&
	(*line == ' ' || *line == '\t' ||
	*line == '\r' || *line == '\n')) {
	line++;
	len--;
	}
	if(!len)
	break;
	/* Extract the word */
	for(wordlen = 0; wordlen < len && line[wordlen] != ' ' &&
	line[wordlen] != '\t' && line[wordlen] != '\r' &&
	line[wordlen] != '\n';)
	wordlen++;
	/* Test the word for a matching authentication mechanism */
	mechbit = Curl_sasl_decode_mech(line, wordlen, &llen);
	if(mechbit && llen == wordlen)
	smtpc->sasl.authmechs |= mechbit;
	line += wordlen;
	len -= wordlen;
	}
	}
	if(smtpcode != 1) {
	if(data->set.use_ssl && !Curl_conn_is_ssl(data->conn, FIRSTSOCKET)) {
	/* We do not have an SSL/TLS connection yet, but SSL is requested */
	if(smtpc->tls_supported)
	/* Switch to TLS connection now */
	result = smtp_perform_starttls(data, smtpc);
	else if(data->set.use_ssl == CURLUSESSL_TRY)
	/* Fallback and carry on with authentication */
	result = smtp_perform_authentication(data, smtpc);
	else {
	failf(data, "STARTTLS not supported.");
	result = CURLE_USE_SSL_FAILED;
	}

which means if a server advertises for e.g. STARTTLS as starttls, it is skipped (sad-face).

I expected the following

starttls to work when the server advertises it in lowercase

curl/libcurl version

curl 8.2.0

operating system

All of them