fix(kaitai): restrict sizes for Kaitai struct

[kruton]

Let Kaitai Struct handle more of the validation logic by supplying the expected sizes where possible.

Fixes GHSA-ch3q-cw5r-f4hg

[Copilot]

Pull request overview

This PR strengthens SSH/Kaitai parsing robustness to address GHSA-ch3q-cw5r-f4hg by adding explicit size/count validations in Kaitai .ksy specs and by standardizing how Kaitai validation/parse failures are surfaced to callers (e.g., as TransportException) with new regression tests.

Changes:

• Add Kaitai valid expressions to ensure declared lengths/counts cannot exceed remaining bytes (and basic sanity constraints for packet framing).
• Introduce a shared helper (kaitaiParseFailureOrNull) to detect Kaitai/underflow parse failures and wrap them into TransportException at key boundaries.
• Add/extend unit tests covering malformed packet/agent frames and length validation failures.

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
sshlib/src/main/kotlin/org/connectbot/sshlib/transport/PacketIO.kt	Wrap Kaitai payload-parse failures as TransportException("Malformed SSH packet payload", …)
sshlib/src/main/kotlin/org/connectbot/sshlib/KaitaiParsing.kt	Add helper to detect Kaitai/underflow parse failures in exception cause chains
sshlib/src/main/kotlin/org/connectbot/sshlib/client/SshConnection.kt	Wrap Kaitai parse failures from packet loop into a transport-level error (needs adjustment)
sshlib/src/main/kotlin/org/connectbot/sshlib/client/AgentProtocolHandler.kt	Treat Kaitai parse failures as malformed agent requests and return SSH_AGENT_FAILURE
sshlib/src/test/kotlin/org/connectbot/sshlib/transport/PacketIOTest.kt	Add regression test for wrapping Kaitai validation failures
sshlib/src/test/kotlin/org/connectbot/sshlib/SshClientTest.kt	Add regression test for connect returning ProtocolError on malformed server packet
sshlib/src/test/kotlin/org/connectbot/sshlib/protocol/KaitaiLengthValidationTest.kt	New tests asserting Kaitai valid length/count validations trip correctly
sshlib/src/test/kotlin/org/connectbot/sshlib/AgentProtocolTest.kt	Add tests for rejecting malformed agent frames/payloads and not masking provider exceptions
protocol/src/main/resources/kaitai/ascii_string.ksy	Add remaining-bytes validation to length field
protocol/src/main/resources/kaitai/byte_string.ksy	Add remaining-bytes validation to length field
protocol/src/main/resources/kaitai/ecdsa_signature_blob.ksy	Add remaining-bytes validation to blob length
protocol/src/main/resources/kaitai/encrypted_packet.ksy	Validate encrypted payload length matches remaining bytes (excluding MAC)
protocol/src/main/resources/kaitai/etm_mac.ksy	Validate encrypted packet length matches remaining bytes
protocol/src/main/resources/kaitai/mpint.ksy	Add remaining-bytes validation to length field
protocol/src/main/resources/kaitai/name_list.ksy	Add remaining-bytes validation to entries length
protocol/src/main/resources/kaitai/restrict_destination_constraint.ksy	Bound keyspec counts by remaining bytes
protocol/src/main/resources/kaitai/ssh_agent_identities_answer.ksy	Bound identity count by remaining bytes
protocol/src/main/resources/kaitai/ssh_agent_message.ksy	Validate agent frame length matches remaining bytes
protocol/src/main/resources/kaitai/ssh_msg_ext_info.ksy	Bound extension count by remaining bytes
protocol/src/main/resources/kaitai/ssh_msg_userauth_info_request.ksy	Bound prompt count by remaining bytes
protocol/src/main/resources/kaitai/ssh_msg_userauth_info_response.ksy	Bound response count by remaining bytes
protocol/src/main/resources/kaitai/ssh_public_key.ksy	Add remaining-bytes validation to algorithm name length
protocol/src/main/resources/kaitai/ssh_signature.ksy	Add remaining-bytes validation to algorithm name length
protocol/src/main/resources/kaitai/unencrypted_packet.ksy	Validate packet framing fields (len_packet, padding length)
protocol/src/main/resources/kaitai/userauth_request_gssapi_with_mic.ksy	Bound mechanism count by remaining bytes
protocol/src/main/resources/kaitai/utf8_string.ksy	Add remaining-bytes validation to length field

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[Copilot]

Pull request overview

Copilot reviewed 29 out of 30 changed files in this pull request and generated 2 comments.