Previously when encountering a CA-signed cert that failed verification with "Hostname mismatch",
we would
1. erroneously mark it as self-signed
2. save its cert to pin it
3. when connecting to it later, and being served a CA-signed cert, we would reject the connection
- I think this is because we use the saved cert (the peer cert, just the last cert in the chain) as if it was a root CA,
and then during the connection we try to verify against that root. This fails as we are served a different root then.
Error logged in step(3):
```
3.85 | W | i/interface.[wirg2tsto7rme7n26lkd3ivbvxmjyy2pktlozwjuep22jcsfsghfqbqd.onion:50002] | Cannot connect to main server due to SSL error (maybe cert changed compared to "/home/user/.electrum/testnet/certs/wirg2tsto7rme7n26lkd3ivbvxmjyy2pktlozwjuep22jcsfsghfqbqd.onion"). Exc: ConnectError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1007)'))
```
This commit fixes step(1), we won't mark the cert as self-signed, instead the error is propagated out and the connection closed.
```
35.05 | I | i/interface.[wirg2tsto7rme7n26lkd3ivbvxmjyy2pktlozwjuep22jcsfsghfqbqd.onion:50002] | disconnecting due to: ErrorGettingSSLCertFromServer(ConnectError(SSLCertVerificationError(1, "[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: Hostname mismatch, certificate is not valid for 'wirg2tsto7rme7n26lkd3ivbvxmjyy2pktlozwjuep22jcsfsghfqbqd.onion'. (_ssl.c:1007)")))
```
Compare:
- SSLCertVerificationError(1, "[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: Hostname mismatch, certificate is not valid for 'wirg2tsto7rme7n26lkd3ivbvxmjyy2pktlozwjuep22jcsfsghfqbqd.onion'. (_ssl.c:1007)")
- verify_code=62
- SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate (_ssl.c:1007)')
- verify_code=18
Note: the verify_code constants look stable, though they might be openssl-specific. I guess that's ok(?)
140540189c/include/openssl/x509_vfy.h.in (L224)
02a9ab80be