Abe Estrada

Initially after upgrading everything was working great until I tried to SSH into an older legacy linux server and was greeted with this lovely message:

sign_and_send_pubkey: no mutual signature supported
user@example.com: Permission denied (publickey).

The reason for this issue is that MacOS 13 ships with OpenSSH_9.0p1 which has disabled RSA signatures on SHA-1 hash algorithms. If upgrading OpenSSH on the server and/or regenerating your SSH key isn’t an option you can workaround this issue by adding the following to your ~/.ssh/config file

Host *
  HostkeyAlgorithms +ssh-rsa
  PubkeyAcceptedAlgorithms +ssh-rsa

If you don’t want to add this across the board you can also pass an SSH option when connecting via SSH as follows:

ssh -o 'PubkeyAcceptedKeyTypes +ssh-rsa' -i ~/.ssh/yourkey user@example.com