Skip to content

fix: modify GEX parameters in SSH key exchange configuration so that it uses 2048 bits#1659

Merged
Eugeny merged 3 commits intowarp-tech:mainfrom
joseluisgonzalezca:main
Jan 7, 2026
Merged

fix: modify GEX parameters in SSH key exchange configuration so that it uses 2048 bits#1659
Eugeny merged 3 commits intowarp-tech:mainfrom
joseluisgonzalezca:main

Conversation

@joseluisgonzalezca
Copy link
Copy Markdown
Contributor

@joseluisgonzalezca joseluisgonzalezca commented Jan 7, 2026

This PR modifies the default SSH client configuration related to key exchange algorithms.

When using GEX (Group Exchange) algorithms, the underlying SSH library enforces a minimum key size greater than 3000 bits (reference). This causes the key exchange negotiation to fail on some legacy devices (p.e, MikroTik routers running older versions of RouterOS). These devices only support a maximum of 2048 bits.

With this change, the SSH client configuration is adjusted to allow compatibility with these systems, enabling successful SSH connections while maintaining existing behavior for supported environments.

@Eugeny
Copy link
Copy Markdown
Member

Eugeny commented Jan 7, 2026

The russh GEX group size defaults are based on OpenSSH - but you can make this size reduction only kick in when allow_insecure_algos is set

@joseluisgonzalezca
Copy link
Copy Markdown
Contributor Author

Hi @Eugeny!

I've committed the latest changes with your suggestion. Could you verify that everything is alright?

Thanks!

@Eugeny
Copy link
Copy Markdown
Member

Eugeny commented Jan 7, 2026

Looks good now, thanks!

@Eugeny Eugeny merged commit 0872234 into warp-tech:main Jan 7, 2026
14 checks passed
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels

None yet

Projects

None yet

Development

Successfully merging this pull request may close these issues.

2 participants