(This is hypothetical, but based on a real-life problem I've had)
I am developing an (embedded) device which includes a few exposed network services. I'm responsible for security, not developing these services, so I don't know how they're built.
I do some testing (send targeted Client Hello messages to the device services with specific cipher suites) and find that some of these services accept weak TLS cipher suites.
I am now tasked with addressing this problem, preferably by fixing the problem as far back in the stack as possible (e.g. I would prefer to avoid having to look at the code/configuration of each individual application and would instead like to fix it at the system level).
- I know that OpenSSL is the only crypto library/program in use on the system.
Now some questions:
What options do I have for preventing network services from allowing weak TLS ciphers? (e.g. change OpenSSL itself, change OpenSSL configuration files, change OS configuration, etc.)
Which options are reasonably "safe"? e.g. I suppose I could modify the OpenSSL code and remove every mention of these cipher suites, recompile, and integrate. This would prevent applications from sending the suites (even if they ask for them). However, this seems like a dangerous solution and difficult to maintain long term.
Is this even possible, or do I necessarily need to look at each service?