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RUB-NDS / Terrapin-Scanner

This repository contains a simple vulnerability scanner for the Terrapin attack present in the paper "Terrapin Attack: Breaking SSH Channel Integrity By Sequence Number Manipulation".
https://terrapin-attack.com
Apache License 2.0
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When neither chacha nor cbm-EtM ciphers are supported by the server the report misleadingly states Terrapin mitigations are in place #22

Closed hellt closed 10 months ago

hellt commented 10 months ago

Thank you for the scanner tool!

It might be that the report message should be different when neither of vulnerable ciphers are supported by the server; e.g.:

❯ ./Terrapin_Scanner_Linux_amd64 --connect clab-sros-sros
================================================================================
==================================== Report ====================================
================================================================================

Remote Banner: SSH-2.0-OpenSSH_8.9

ChaCha20-Poly1305 support:   false
CBC-EtM support:             false

Strict key exchange support: false

The scanned peer supports Terrapin mitigations and can establish
connections that are NOT VULNERABLE to Terrapin. Glad to see this.
For strict key exchange to take effect, both peers must support it.

Since neither cipher is supported it might be not desirable to say that scanned peer supports Terrapin mitigations since strict kex is not in place?

I can see how disabled ciphers can be considered as a mitigation action, but still it feels like the message might be more precise in that case

hellt commented 10 months ago

After reading more on this I think my proposal is not legit.