Security enhancement: TLS configuration

[dreibh]

In neat_security.c: neat_security_install():

SSL_CTX_set_options(private->ctx, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3):
What about adding SSL_OP_NO_TLSv1 and SSL_OP_NO_TLSv1_1 as well, in order to enforce at least TLS 1.2 by default? If a user program wants to allow older versions (TLS 1.0, TLS 1.1), it must explicitly override the default.

SSL_CTX_set_cipher_list(private->ctx, "DEFAULT:-RC4");
This deactivates RC4, which is good. But the TLS ciphers also contain algorithms like DES and SHA-1. What about using only state-of-the-art ciphers by default? If a user program wants to allow weaker algorithms, it must explicitly override the default. NEAT needs an API for setting the ciphers.

[mcmanus]

i don't think actually wants an api for setting ciphers - this is something it should simply do correctly as a design choice. but its a design choice and ymmv - but its consistent with the purpose of the api.

the ciphers should be restricted further, I agree.

tls 1.0 and 1.1 are considered acceptable best practice right now (in a way that ssl and rc4 are not) and removing them would break compat with many legacy servers.. as neat endeavors to communicate with non neat system I think the best policy is to keep neat updated with best practices and have it updated independently of the applications it is linked to.

[dreibh]

TLS 1.2 is already more than 8 years old. If users really want to use very old legacy systems, they should explicitly request backwards compatibility (or better fix their systems to have state-of-the-art security). The default should be state-of-the-art security, not legacy support.

[mcmanus]

feel free to make the change if you like.