Public bug reported: Users are unable to connect to Ubuntu when using openssh client 7.8. We have seen this with both xenial and bionic, but this affects connecting to ANY host running openssh <7.8.
The only known recourse at this time is either downgrade clients to 7.7 or a previous version of openssh, or create new keys/certificates with a different alg that is acceptable for both the older server and newer client. The error message via ssh -vvv is: debug1: Next authentication method: publickey debug1: Offering public key: RSA SHA256:REDACTED debug1: send_pubkey_test: no mutual signature algorithm It appears that the change noted here in the release notes[1] for 7.8 is related: * sshd(8): the semantics of PubkeyAcceptedKeyTypes and the similar HostbasedAcceptedKeyTypes options have changed. These now specify signature algorithms that are accepted for their respective authentication mechanism, where previously they specified accepted key types. This distinction matters when using the RSA/SHA2 signature algorithms "rsa-sha2-256", "rsa-sha2-512" and their certificate counterparts. Configurations that override these options but omit these algorithm names may cause unexpected authentication failures (no action is required for configurations that accept the default for these options). This is also affecting other Linux distributions as well: https://bugzilla.redhat.com/show_bug.cgi?id=1623929 https://bugs.archlinux.org/task/59838 [1] https://www.openssh.com/releasenotes.html ** Affects: openssh (Ubuntu) Importance: Undecided Status: Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1790963 Title: Unable to connect with openssh 7.8 client To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1790963/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
