Fix/tlv unknown arbitrary offset#86
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brainstorm merged 2 commits intoApr 1, 2026
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TLV unknown packet can arbitrarily advance the stream. The decision here is disabling skipping unknown TLV types and instead let the ota handler fail
The result of this change is that on sending an incorrect (crafted) ota file the ssh-server aborts the ota-update. The client receives a Failure but that is not enough to close the connection. The crafted file was created editing the type immediately after OtaType (value 0) and giving it a value out of range (0x09)
brainstorm
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Apr 1, 2026
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Not sure if that error handling belongs on the side of SSH Stamp, but I'll be approving it now just in case I'm flat wrong: you decide, @jubeormk1 ;)
EDIT: Merging it after disabling the hil-ready branch rules, we'll re-enable them later... open another PR addressing my comments (if needed at all!).
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This PR is focus on Radically Open Security report on the possible arbitrary offset injection on TLV parameters that may lead to undefined behaviour.
An unknown TLV element in the ota packet now is rejected by the ota handler. The SftpServer response to the Write request in this case is sending back to the client a SSH_FX_OP_UNSUPPORTED status.
This fix blocks the client but does not block the server, that can receive other ssh or sftp connections after the failure.