Support SSL Request V2 packet

[bgrainger]

If mariadb-corporation/mariadb-connector-c#227 is accepted, then MySqlConnector should also support the new TLS handshake.

Exact details are in that case and subject to change, but at a high level:

• Server exposes "supports SSL Request V2" bit
• Client sends new two-byte SSL Request V2 packet
• Client should (must?) verify CA to avoid MitM
• Client sends handshake response with "supports SSL Request V2" bit set

[dlenski]

Thanks for creating this!

As I just noted in mariadb-corporation/mariadb-connector-c#227 (comment) …

I also moved the CLIENT_CAN_SSL_V2 capability bit from the MariaDB extensions (1ULL << 37) to the shared MySQL/MariaDB capability bits (1ULL << 28).

MySQL is affected by these vulnerabilities as well, and if we want to enable a better TLS handshake for all client/server combinations, this capability bit needs to be sent between all client/server combinations.

I believe this will be necessary for non-MariaDB-specific clients like yours to receive the appropriate capability bit from the server (Server exposes "supports SSL Request V2" bit ).

[dlenski]

• Client sends handshake response with "supports SSL Request V2" bit set

As it's currently implemented in mariadb-corporation/mariadb-connector-c#227 and MariaDB/server#2684, the client's initial (plaintext) packet will contain only the CLIENT_SSL bit.

However, in the post-TLS packet, the client should send the CLIENT_CAN_SSL_V2 bit, because this will allow the server to detect a downgrade attack in which a MITM has forced the client not to use the SSL V2 handshake.

https://github.com/MariaDB/server/pull/2684/files#diff-df544694418bef1c4bc6cdc5211ca133e7ad4d31901f16d0fdee8df6e4debe89R12792-R12813

[bgrainger]

• Client sends handshake response with "supports SSL Request V2" bit set

However, in the post-TLS packet, the client should send the CLIENT_CAN_SSL_V2 bit

Yes, that's what I meant in my issue. The handshake packet is now only sent after TLS is negotiated (because what would have been the first "handshake response" is now replaced with "SSL Request V2").