Is 'gcloud compute ssh' busted in the new release?

[Gene S]

Seems like some problem with the SSL config. It worked just fine 4 days ago when I used it last time. SSH works fine from the web (console.cloud.google.com). The only thing that changed in the last 4 days is the new release of gcloud CLI.

I'm on Mac M1, the instance is debian-9-stretch-v20200309, it's been up and running for several months.

Any suggestions?

% gcloud compute ssh gene@sandbox -- -vvv
OpenSSH_8.6p1, LibreSSL 3.3.6
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: include /etc/ssh/ssh_config.d/* matched no files
debug1: /etc/ssh/ssh_config line 54: Applying options for *
debug2: resolve_canonicalize: hostname 104.196.xx.xx is address
debug1: Authenticator provider $SSH_SK_PROVIDER did not resolve; disabling
debug3: ssh_connect_direct: entering
debug1: Connecting to 104.196.xx.xx [104.196.xx.xx] port 22.
debug3: set_sock_tos: set socket 3 IP_TOS 0x48
debug1: Connection established.
debug1: identity file /Users/gene/.ssh/google_compute_engine type 0
debug1: identity file /Users/gene/.ssh/google_compute_engine-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4p1 Debian-10+deb9u7
debug1: compat_banner: match: OpenSSH_7.4p1 Debian-10+deb9u7 pat OpenSSH_7.0*,OpenSSH_7.1*,OpenSSH_7.2*,OpenSSH_7.3*,OpenSSH_7.4*,OpenSSH_7.5*,OpenSSH_7.6*,OpenSSH_7.7* compat 0x04000002
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 104.196.xx.xx:22 as 'gene'
debug1: using hostkeyalias: compute.5011771574355214033
debug3: record_hostkey: found key type ECDSA in file /Users/gene/.ssh/google_compute_known_hosts:4
debug3: load_hostkeys_file: loaded 1 keys from compute.5011771574355214033
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nis...@openssh.com,ecdsa-sha2-nistp256
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve255...@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: ecdsa-sha2-nis...@openssh.com,ecdsa-sha2-nistp256,ssh-ed2551...@openssh.com,ecdsa-sha2-nis...@openssh.com,ecdsa-sha2-nis...@openssh.com,sk-ssh-ed25...@openssh.com,sk-ecdsa-sha2-n...@openssh.com,rsa-sha2-5...@openssh.com,rsa-sha2-2...@openssh.com,ssh-rsa-...@openssh.com,ssh-ed25519,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,sk-ssh-...@openssh.com,sk-ecdsa-sh...@openssh.com,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20...@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes12...@openssh.com,aes25...@openssh.com
debug2: ciphers stoc: chacha20...@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes12...@openssh.com,aes25...@openssh.com
debug2: MACs ctos: umac-...@openssh.com,umac-1...@openssh.com,hmac-sha...@openssh.com,hmac-sha...@openssh.com,hmac-s...@openssh.com,uma...@openssh.com,umac...@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-...@openssh.com,umac-1...@openssh.com,hmac-sha...@openssh.com,hmac-sha...@openssh.com,hmac-s...@openssh.com,uma...@openssh.com,umac...@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zl...@openssh.com,zlib
debug2: compression stoc: none,zl...@openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve255...@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: chacha20...@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes12...@openssh.com,aes25...@openssh.com
debug2: ciphers stoc: chacha20...@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes12...@openssh.com,aes25...@openssh.com
debug2: MACs ctos: umac-...@openssh.com,umac-1...@openssh.com,hmac-sha...@openssh.com,hmac-sha...@openssh.com,hmac-s...@openssh.com,uma...@openssh.com,umac...@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-...@openssh.com,umac-1...@openssh.com,hmac-sha...@openssh.com,hmac-sha...@openssh.com,hmac-s...@openssh.com,uma...@openssh.com,umac...@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zl...@openssh.com
debug2: compression stoc: none,zl...@openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20...@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20...@openssh.com MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
Connection closed by 104.196.xx.xx port 22

Recommendation: To check for possible causes of SSH connectivity issues and get
recommendations, rerun the ssh command with the --troubleshoot option.

gcloud compute ssh sandbox --project=xxxxx-1000 --zone=us-east1-c --troubleshoot

Or, to investigate an IAP tunneling issue:
gcloud compute ssh sandbox --project=xxxxx-1000 --zone=us-east1-c --troubleshoot --tunnel-through-iap

ERROR: (gcloud.compute.ssh) [/usr/bin/ssh] exited with return code [255].

[Ernesto Contreras Pinon]

I tried using the latest version of the gcloud CLI as of now (387.0.0) from a Linux machine and could not get this error to appear when connecting to my GCE instances through SSH. It could be possible that this error (code 255) is caused after a configuration change within gcloud or your instances. The command shown in the linked thread “gcloud compute config-ssh” is used to generate the required configuration files to connect to your instances. Have you tried it after seeing this error?