interimap/tests/tls-protocols/t, branch debian/buster-backports

test suite: use stock OpenSSL config except for tests/tls-protocols.

2020-12-17T12:47:09Z

It's best to use a stock (clean) environment when possible. We only need to test TLS protocol version <1.2 for tests/tls-protocols.

typofix

2020-12-13T22:47:15Z

test suite: ensure we haven't started speaking IMAP when the SSL/TLS handshake is aborted.

2020-12-13T16:38:07Z

(Unless STARTTLS is used to upgrade the connection.)

libinterimap: deprecate SSL_protocols and introduce SSL_protocol_{min,max}.

2020-12-11T18:33:30Z

Using the libssl interface simplifies our protocol black/whitelist greatly; this only allows simple min/max bounds, but holes are arguably not very useful here. Using the new settings bumps the required libssl version to 1.1.0.

libinterimap: remove default SSL_protocols value.

2020-12-11T17:32:16Z

Namely, use the system default instead of "!SSLv2 !SSLv3 !TLSv1 !TLSv1.1". As of Debian Buster (OpenSSL 1.1.1) this does not make a difference, however using the system default provides better compatibility with future libssl versions.

Test suite: add new tests for SSL/TLS.

2019-11-13T05:23:57Z

SSL connections are accepted on TCP port 10993. Also, fix STARTTLS directive, broken since fba1c36…