@Magnus ran into this issue yesterday, and I experienced it just now: occasionally, the Stretch bastion seems to close SSH connections just before authentication succeeds. At normal verbosity, it looks like this:
$ ssh toolforge Connection closed by 185.15.56.48 port 22
With -vvv, here are the last few lines of output:
… debug1: Next authentication method: publickey debug1: Offering public key: /home/lucas/.ssh/[KEY] ED25519 SHA256:[HASH] explicit agent debug3: send packet: type 50 debug2: we sent a publickey packet, wait for reply debug3: receive packet: type 60 debug1: Server accepts key: /home/lucas/.ssh/[KEY] ED25519 SHA256:[HASH] explicit agent debug3: sign_and_send_pubkey: ED25519 SHA256:[HASH] debug3: sign_and_send_pubkey: signing using ssh-ed25519 debug3: send packet: type 50 Connection closed by 185.15.56.48 port 22
The problem usually seems to resolve itself within minutes; here’s the corresponding output of a successful session immediately afterwards, at the same verbosity level:
… debug1: Next authentication method: publickey debug1: Offering public key: /home/lucas/.ssh/[KEY] ED25519 SHA256:[HASH] explicit agent debug3: send packet: type 50 debug2: we sent a publickey packet, wait for reply debug3: receive packet: type 60 debug1: Server accepts key: /home/lucas/.ssh/[KEY] ED25519 SHA256:[HASH] explicit agent debug3: sign_and_send_pubkey: ED25519 SHA256:[HASH] debug3: sign_and_send_pubkey: signing using ssh-ed25519 debug3: send packet: type 50 debug3: receive packet: type 52 debug1: Authentication succeeded (publickey). Authenticated to login-stretch.tools.wmflabs.org ([185.15.56.48]:22). …
Still, it would be nice if this worked more realiably… any ideas what’s going on?