configured sslciphers not respected.

[eebssk1]

The issue

I configed sslCiphers=DHE-RSA-CHACHA20-POLY1305 in server ini to disable AES.
However when starting server the following indicating it's not respected and clients still connecting with AES encryption.

2024-06-12 13:01:34.054 MetaParams: TLS cipher preference is "TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256:DHE-RSA-CHACHA20-POLY1305"

Mumble version

1.5.634

Mumble component

Server

OS

Linux

Additional information

No response

[eebssk1]

I had to clear tls1.3 and unintended ciphers in openssl.cnf to make it work.

[Krzmbrzl]

openssl.cnf as in the OpenSSL config file? The intended way is that this is not required 🤔

Does the Mumble config setting (without changed OpenSSL config) come into effect when you create a fresh server (that doesn't reuse the old's database)?

[eebssk1]

openssl.cnf as in the OpenSSL config file? The intended way is that this is not required 🤔

Does the Mumble config setting (without changed OpenSSL config) come into effect when you create a fresh server (that doesn't reuse the old's database)?

So I digged a little.

It looks like official client does not support chacha20 in (EC)DHE mode. And it seems the sslciphers config options does not accept ciphersuit name.
Which means the only way for me is to remove the AES one from openssl.cnf ciphersuit so chacha20 one is the prefered.
Maybe it's better to seprate the config options for TLS1.3 and TLS1.2_and_older, as indicated by openssl that they are unrelated.

[eebssk1]

So for clafirication. I'm still using TLS 1.3 but with only chacha20 one. I removed AES ciphersuit from openssl.cnf since mumble config does not regconise ciphersuit name which means i can not set the preference there.

[Krzmbrzl]

When using the sslciphers config option, you should get a message like MetaParams: TLS cipher preference is ... when starting up the server. Does this message agree with what you have configured in the INI file?

'cause what is printed there should also be used for the actual connections if I read the code correctly 🤔

[eebssk1]

When using the sslciphers config option, you should get a message like MetaParams: TLS cipher preference is ... when starting up the server. Does this message agree with what you have configured in the INI file?

'cause what is printed there should also be used for the actual connections if I read the code correctly 🤔

Server won't startup. The TLS1.3 cipher string is not recognized by the option.

[eebssk1]

When using the sslciphers config option, you should get a message like MetaParams: TLS cipher preference is ... when starting up the server. Does this message agree with what you have configured in the INI file?
'cause what is printed there should also be used for the actual connections if I read the code correctly 🤔

Server won't startup. The TLS1.3 cipher string is not recognized by the option.

It's very weired that MetaParams automatically prepend tls1.3 ciphers,but the options does not recognize it when manually entered.

[Krzmbrzl]

The appending of additional ciphers is actually done by OpenSSL, it seems. The cipher list entering

mumble/src/SSL.cpp

Lines 49 to 108 in 9f0b143

	QList< QSslCipher > MumbleSSL::ciphersFromOpenSSLCipherString(QString cipherString) {
	QList< QSslCipher > chosenCiphers;
	SSL_CTX *ctx = nullptr;
	SSL *ssl = nullptr;
	const SSL_METHOD *meth = nullptr;
	int i = 0;
	QByteArray csbuf = cipherString.toLatin1();
	const char *ciphers = csbuf.constData();
	meth = SSLv23_server_method();
	if (!meth) {
	qWarning("MumbleSSL: unable to get SSL method");
	goto out;
	}
	// We use const_cast to be compatible with OpenSSL 0.9.8.
	ctx = SSL_CTX_new(const_cast< SSL_METHOD * >(meth));
	if (!ctx) {
	qWarning("MumbleSSL: unable to allocate SSL_CTX");
	goto out;
	}
	if (!SSL_CTX_set_cipher_list(ctx, ciphers)) {
	qWarning("MumbleSSL: error parsing OpenSSL cipher string in ciphersFromOpenSSLCipherString");
	goto out;
	}
	ssl = SSL_new(ctx);
	if (!ssl) {
	qWarning("MumbleSSL: unable to create SSL object in ciphersFromOpenSSLCipherString");
	goto out;
	}
	while (1) {
	const char *name = SSL_get_cipher_list(ssl, i);
	if (!name) {
	break;
	}
	#if QT_VERSION >= 0x050300
	QSslCipher c = QSslCipher(QString::fromLatin1(name));
	if (!c.isNull()) {
	chosenCiphers << c;
	}
	#else
	foreach (const QSslCipher &c, QSslSocket::supportedCiphers()) {
	if (c.name() == QString::fromLatin1(name)) {
	chosenCiphers << c;
	}
	}
	#endif
	++i;
	}
	out:
	SSL_CTX_free(ctx);
	SSL_free(ssl);
	return chosenCiphers;
	}

is the one from the INI file but the one leaving this function contains the extra ciphers.

[eebssk1]

According to https://manpages.debian.org/testing/libssl-doc/OPENSSL_config.3ssl.en.html
Maybe we could set OPENSSL_CONF to load the modded conf instead of loading/modifying the global one.
Since the function will always called by qt dependencies(it seems), this way might work.