> I am writing a SSL/TLS client (using Boost.Beast but underlying it's using > OpenSSL) and although I have set on the SSL context the 'verify_peer' flag, > there is no verification to prove the server presents an X509 which > contains in the Subject Alternative Names the hostname of that server. > > As this is probably the dumbest type of attack someone could do (using a > valid certificate with another domain name), I am thinking I'm doing > something wrong. But from the documentation, I saw that using "verify_peer" > should perform all the verifications...
It verifies the trust chain. To also verify the peer name, you need to specify the peer name via: SSL_set1_host() > Now if not even this simple check is being done, how about expiration of > the certificate, revocation status and other checks? Should they be > performed manually as well? No, that's what VERIFY_PEER is for. > For now I am using X509_VERIFY_PARAM_set1_host with SSL_CTX_set1_param to > do this specific check. That's the slightly less convenient legacy API from OpenSSL 1.0.2. In 1.1.0 and later, you can use SSL_set1_host() (and in some cases also SSL_add1_host()). See the SSL_set1_host(3) manpage for details. --------------------------- Indeed I re-read the docs and it says that users should not assume that hostnames are validated by default without explicitly calling the API, I must've missed that bit and thank you for letting me know. I will shift towards using the newer SSL_set1_host together with some flags (I don't want any wildcards). Now just to be extra safe I'm still asking: will the VERIFY_PEER option together with SSL_set1_host instruct OpenSSL to perform all possible checks on the certificate presented by the server such that no security breach remains at this level? Is there anything else that I should call or perform manually? -- Theodor