fix(echcheck): do not attempt a TLS handshake when the TCP connect failed - #1817
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fix(echcheck): do not attempt a TLS handshake when the TCP connect failed#1817macintoshi-nakamoto wants to merge 1 commit into
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…iled When the dial fails, conn is nil and tls.Client(nil, ...).HandshakeContext panics inside crypto/tls. This is what users saw with min-ng.test.defo.ie once its port 15443 stopped answering. Return the test keys after recording the failed TCP connect instead; that is the measurement. Adds a localhost regression test that dials a closed port with and without GREASE. It panics without the fix. Closes ooni#1728
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handshake()ininternal/experiment/echcheckdials the target and then callstls.Client(conn, ...).HandshakeContext()without checking whether the dial succeeded. When it did not,connis nil andcrypto/tlspanics while writing the ClientHello. This is the trace reported in #1725 and tracked in #1728: it shows up whenever a target stops answering on its port, asmin-ng.test.defo.ie:15443did.The change returns the test keys right after the failed TCP connect has been recorded, since that is the measurement: a
tcp_connectsentry with the failure and notls_handshakesentry, because no handshake was attempted. No shape ofTestKeyschanges.The regression test binds a port on localhost, closes it, and runs
startHandshakeagainst it with and without GREASE. Without the fix the test panics with the same nil pointer dereference as the issue; with the fix it passes. Verified withgo test -short ./internal/experiment/echcheck/.Small side observation, not addressed here to keep the diff minimal: the TLS conn is never closed after the handshake, so a successful handshake leaks the socket until the process exits. Happy to send that as a separate PR if you want it.