Several TLS issues

[Marcus Bointon]

The TLS options config section allows various useful options, however, it's missing some important ones:

• prefer server cipher order
• cipher list
• disable Secure Client-Initiated Renegotiation

Nice-to-have options would be to allow the use of ECC (ECDSA) certificates, since they are smaller, stronger, and faster - there are some mentions of these in the release notes, but no comments in the documentation about how to use multiple certificates (e.g. RSA and ECC) for browser compatibility.

Testing monit with testssl.sh shows all these problems quite clearly.

[Marcus Bointon]

I should have mentioned - those three I listed are considered security vulnerabilities because they may allow attackers to intercept, downgrade, expose and otherwise interfere with supposedly secure traffic.

[Tildeslash]

Monit uses currently the following hardcoded ciphers string for both client and server role:

ALL:!DES:!RC4:!aNULL:!LOW:!EXP:!IDEA:!MD5:@STRENGTH

Vulnerable ciphers are disabled by default. It's true the option to override this cipher list without recompilation is not present currently (we plan to add it), but it's not vulnerability.

[Marcus Bointon]

Thanks for the info.

[Tildeslash]

New: The Monit HTTP interface now allows to set the SSL/TLS version as well. The syntax follows the generic SSL/TLS options settings, which was introduced in Monit 5.15, example:

set httpd port 2812
    with ssl {
       pemfile: /etc/ssl/certs/monit.pem
       version: TLSv12
    }
    allow admin:monit

New: The SSL 3DES ciphers are disabled by default now (vulnerable to Sweet32 attacks).

Fixed Issue #509: Added support to override the SSL/TLS ciphers list and enabled server-side ciphers preference. Example (using monit's default ciphers string):

set ssl {
    ciphers: "ALL:!DES:!3DES:!RC4:!aNULL:!LOW:!EXP:!IDEA:!MD5:@STRENGTH"
}

Fixed Issue #510: The "set ssl" options defaults had no effect on the Monit HTTPD interface.

→ <<cset eb2f060d1356>>