Use claude to devise more testing

[kruton]

Actually came up with some nice bugs.

[Copilot]

Pull request overview

This PR strengthens SSH transport/client security and robustness by adding new tests and tightening implementations around integrity checks, compression limits, signature verification, and channel flow-control window handling.

Changes:

• Add negative-path tests for MAC tampering (encrypt-and-MAC and ETM), DH GEX parameter validation, ECDH all-zero secrets, channel window bounds, and zlib decompression limits.
• Harden implementations: constant-time MAC comparison, zlib decompression output cap, stricter DH group validation, and stricter signature verification (including negotiated algorithm enforcement).
• Refactor channel window tracking into a shared LocalChannelWindow helper and apply it across session/forwarding/agent channels.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sshlib/src/test/kotlin/org/connectbot/sshlib/transport/PacketIOTest.kt	Adds a regression test ensuring tampered MACs are rejected in encrypt-and-MAC mode.
sshlib/src/test/kotlin/org/connectbot/sshlib/transport/PacketIOEtmTest.kt	Adds a regression test ensuring tampered MACs are rejected in ETM mode.
sshlib/src/test/kotlin/org/connectbot/sshlib/crypto/ZlibCompressorTest.kt	Adds tests for decompression-bomb rejection and within-limit decompression acceptance.
sshlib/src/test/kotlin/org/connectbot/sshlib/crypto/SignatureVerifierTest.kt	New tests asserting negotiated-signature-algorithm enforcement for RSA SHA-2 vs SHA-1.
sshlib/src/test/kotlin/org/connectbot/sshlib/crypto/EcdhKeyExchangeTest.kt	Adds test rejecting an all-zero ECDH shared secret.
sshlib/src/test/kotlin/org/connectbot/sshlib/crypto/DiffieHellmanGroupExchangeTest.kt	Adds tests for DH GEX group parameter validation (bit sizes, generator bounds, parity).
sshlib/src/test/kotlin/org/connectbot/sshlib/client/SessionChannelTest.kt	Adds tests for window-adjust validation and local-window enforcement on incoming data.
sshlib/src/test/kotlin/org/connectbot/sshlib/client/LocalChannelWindowTest.kt	New unit tests for LocalChannelWindow window consumption and adjustment rules.
sshlib/src/main/kotlin/org/connectbot/sshlib/transport/PacketIO.kt	Switches MAC comparisons to constant-time MessageDigest.isEqual.
sshlib/src/main/kotlin/org/connectbot/sshlib/crypto/ZlibCompressor.kt	Adds an uncompressed-output cap to mitigate decompression-bomb DoS.
sshlib/src/main/kotlin/org/connectbot/sshlib/crypto/SignatureVerifier.kt	Enforces negotiated signature algorithm during KEX; adds key-type compatibility verifier for self-described signatures.
sshlib/src/main/kotlin/org/connectbot/sshlib/crypto/EcdhKeyExchange.kt	Rejects all-zero shared secret via a new helper used by the main compute path.
sshlib/src/main/kotlin/org/connectbot/sshlib/crypto/DiffieHellmanGroupExchange.kt	Adds basic DH group sanity checks (min/max size, odd p, generator range).
sshlib/src/main/kotlin/org/connectbot/sshlib/client/SshConnection.kt	Plumbs negotiated host key algorithm into SignatureVerifier.verify.
sshlib/src/main/kotlin/org/connectbot/sshlib/client/SessionChannel.kt	Replaces ad-hoc window tracking with LocalChannelWindow.
sshlib/src/main/kotlin/org/connectbot/sshlib/client/LocalChannelWindow.kt	New helper to centralize channel window accounting and validation.
sshlib/src/main/kotlin/org/connectbot/sshlib/client/ForwardingChannel.kt	Replaces ad-hoc window tracking with LocalChannelWindow.
sshlib/src/main/kotlin/org/connectbot/sshlib/client/AgentProtocolHandler.kt	Uses verifyWithKeyType for session-bind signature verification.
sshlib/src/main/kotlin/org/connectbot/sshlib/client/AgentChannel.kt	Adds local window enforcement and migrates remote window tracking to LocalChannelWindow.

Comments suppressed due to low confidence (1)

sshlib/src/main/kotlin/org/connectbot/sshlib/client/ForwardingChannel.kt:92

• Same issue as SessionChannel: window.remoteRemaining.toInt() can overflow when the remote window exceeds Int.MAX_VALUE (valid for SSH uint32 windows). Calculate chunkSize using Long min bounds (including maxPacketSize) and then convert safely to Int.

            while (window.remoteRemaining <= 0) {
                windowAvailable.receive()
            }
            val chunkSize = minOf(
                data.size - offset,
                window.remoteRemaining.toInt(),
                maxPacketSize,
            )

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