the ssh service at git.launchpad.net offers only the deprecated ssh-rsa HostKeyAlgorithm

Asked by dkg on 2020-10-13

Currently, an ssh client that deliberately drops `ssh-rsa` from its list of HostKeyAlgorithms as a conservative defense against known SHA1 attacks cannot connect to git.launchpad.net.

The command line error for me shows:

    Unable to negotiate with 91.189.94.79 port 22: no matching host key type found. Their offer: ssh-rsa

This is because the ssh service at git.launchpad.net offers only the `ssh-rsa` HostKeyAlgorithm, which is deprecated due to its reliance on SHA1:

(see: https://github.com/jtesta/ssh-audit#v220-2020-03-11 as an example)

git.launchpad.net's ssh service should provide a newer form of ssh host key. If you want to stick with RSA, there are several options that do not depend on SHA1, like rsa-sha2-512 or rsa-sha2-256. Or if you're ok with elliptic curves, you could offer ssh-ed25519. Or you could offer multiple host keys for the service.

Question information

Language:
English Edit question
Status:
Answered
For:
Launchpad itself Edit question
Assignee:
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Last query:
2020-10-13
Last reply:
2020-10-13
Colin Watson (cjwatson) said : #1

This is essentially similar to https://bugs.launchpad.net/launchpad/+bug/1813793 in many ways, but I agree it would in addition be wise to offer rsa-sha2-512 and/or rsa-sha2-256. I'll just link this to that bug, since requests for software changes should be tracked as bug reports rather than support requests.

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