crypto: hard-code tlsSocket.getCipher().version

This aligns the documentation with reality. This API never did what Node
claims it did.

The SSL_CIPHER_get_version function just isn't useful. In OpenSSL 1.0.2,
it always returned the string "TLSv1/SSLv3" for anything but SSLv2
ciphers, which Node does not support. Note how test-tls-multi-pfx.js
claims that ECDHE-ECDSA-AES256-GCM-SHA384 was added in TLSv1/SSLv3 which
is not true. That cipher is new as of TLS 1.2. The OpenSSL 1.0.2
implementation is:

char *SSL_CIPHER_get_version(const SSL_CIPHER *c)
{
    int i;

    if (c == NULL)
        return ("(NONE)");
    i = (int)(c->id >> 24L);
    if (i == 3)
        return ("TLSv1/SSLv3");
    else if (i == 2)
        return ("SSLv2");
    else
        return ("unknown");
}

In OpenSSL 1.1.0, SSL_CIPHER_get_version changed to actually behave as
Node documented it, but this changes the semantics of the function and
breaks tests. The cipher's minimum protocol version is not a useful
notion to return to the caller here, so just hardcode the string at
"TLSv1/SSLv3" and document it as legacy.

PR-URL: https://github.com/nodejs/node/pull/16130


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>