proxy: support proxies behind SSH - #57
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A classical technique to authenticate proxies is to piggy back existing SSH authnz systems and perform SSH forwards to access an unprotected proxy. To ease migrations on users with existing proxy fleet, we allow daisychaining to these sorts of proxies. We implement a very opinionated support of SSH: - .ssh/config must contain an entry with proper preconfiguration for User, etc. - Portail configuration needs proxy-host (must match a .ssh/config entry) and target-address (final proxy target, can be 127.0.0.1) - An SSH agent over UDS must be provided (otherwise it's guessed from the environment variable SSH_AUTH_AGENT_SOCKET) and should be able to authenticate over the SSH server - The server must already be trusted in the standard known-hosts file from OpenSSH If these conditions are reunited, the connection will succeed. Signed-off-by: Ryan Lahfa <ryan.lahfa.ext@numerique.gouv.fr>
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March 27, 2026 23:25
rlahfa-dinum
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Mar 27, 2026
| &mut self, | ||
| server_public_key: &russh::keys::ssh_key::PublicKey, | ||
| ) -> Result<bool, Self::Error> { | ||
| // TODO: check known hosts keys |
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this is checking it now
rlahfa-dinum
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Mar 27, 2026
| target_port: config.port(), | ||
| }; | ||
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| // TODO: this is using whoami as a last resort... |
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If I am not mistaken, for our use case, this fallback is always wrong. However I don't see a security problem. So I don't have a strong opinion either way.
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At one point, we might want to store the ssh session, call session.channel_open_direct_tcpip many times on it and have a mecanism to refresh it
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A classical technique to authenticate proxies is to piggy back existing SSH authnz systems and perform SSH forwards to access an unprotected proxy.
To ease migrations on users with existing proxy fleet, we allow daisychaining to these sorts of proxies.
TODO: