SSL_CTX_set_ciphersuites() sets the TLSv1.3 cipher suites.
SSL_CTX_set_cipher_list() sets the ciphers for TLSv1.2 and below.
The current TLS configuration logic will not perform SSL_CTX_set_cipher_list()
to configure TLSv1.2 ciphers if the call to SSL_CTX_set_ciphersuites() was
successful. The call to SSL_CTX_set_ciphersuites() is successful if any TLSv1.3
cipher suite is passed into `--ssl-cipher`.
This is a potential security vulnerability because users trying to restrict
specific secure ciphers for TLSv1.3 and TLSv1.2, would unknowingly still have
the database support insecure TLSv1.2 ciphers.
For example:
If setting `--ssl_cipher=TLS_AES_128_GCM_SHA256:ECDHE-RSA-AES128-GCM-SHA256`,
the database would still support all possible TLSv1.2 ciphers rather than only
ECDHE-RSA-AES128-GCM-SHA256.
The solution is to execute both SSL_CTX_set_ciphersuites() and
SSL_CTX_set_cipher_list() even if the first call succeeds.
This allows the configuration of exactly which TLSv1.3 and TLSv1.2 ciphers to
support.
Note that there is 1 behavior change with this. When specifying only TLSv1.3
ciphers to `--ssl-cipher`, the database will not support any TLSv1.2 cipher.
However, this does not impose a security risk and considering TLSv1.3 is the
modern protocol, this behavior should be fine.
All TLSv1.3 ciphers are still supported if only TLSv1.2 ciphers are specified
through `--ssl-cipher`.
All new code of the whole pull request, including one or several files that are
either new files or modified ones, are contributed under the BSD-new license. I
am contributing on behalf of my employer Amazon Web Services, Inc.
