BitBucket SSH authentication not working

[dreibh]

SSH authentication stopped working. Until a few days ago, everything worked fine. Now, the BitBucket server just breaks the connection without providing any useful debugging information.

$ ssh -v git@bitbucket.org 
OpenSSH_9.6p1 Ubuntu-3ubuntu13.16, OpenSSL 3.0.13 30 Jan 2024 
debug1: Reading configuration data /etc/ssh/ssh_config 
debug1: Connecting to bitbucket.org [2401:1d80:3210::bbc:1:df7c] port 22. 
debug1: Connection established. 
debug1: identity file /home/dreibh/.ssh/id_rsa type 0 
debug1: identity file /home/dreibh/.ssh/id_rsa-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_ecdsa type -1 
debug1: identity file /home/dreibh/.ssh/id_ecdsa-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_ecdsa_sk type -1 
debug1: identity file /home/dreibh/.ssh/id_ecdsa_sk-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_ed25519 type -1 
debug1: identity file /home/dreibh/.ssh/id_ed25519-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_ed25519_sk type -1 
debug1: identity file /home/dreibh/.ssh/id_ed25519_sk-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_xmss type -1 
debug1: identity file /home/dreibh/.ssh/id_xmss-cert type -1 
debug1: identity file /home/dreibh/.ssh/id_dsa type -1 
debug1: identity file /home/dreibh/.ssh/id_dsa-cert type -1 
debug1: Local version string SSH-2.0-OpenSSH_9.6p1 Ubuntu-3ubuntu13.16 
debug1: Remote protocol version 2.0, remote software version conker_20260710-1d8daf58a8 b3292a363f5c 
debug1: compat_banner: no match: conker_20260710-1d8daf58a8 b3292a363f5c 
debug1: Authenticating to bitbucket.org:22 as 'git' 
debug1: load_hostkeys: fopen /home/dreibh/.ssh/known_hosts2: No such file or directory 
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 
debug1: SSH2_MSG_KEXINIT sent 
debug1: SSH2_MSG_KEXINIT received 
debug1: kex: algorithm: curve25519-sha256@libssh.org 
debug1: kex: host key algorithm: ssh-ed25519 
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none 
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none 
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY 
debug1: SSH2_MSG_KEX_ECDH_REPLY received 
debug1: Server host key: ssh-ed25519 SHA256:ybgmFkzwOSotHTHLJgHO0QN8L0xErw6vd0VhFA9m3SM 
DNS lookup error: data does not exist 
debug1: load_hostkeys: fopen /home/dreibh/.ssh/known_hosts2: No such file or directory 
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 
debug1: Host 'bitbucket.org' is known and matches the ED25519 host key. 
debug1: Found key in /home/dreibh/.ssh/known_hosts:136 
debug1: ssh_packet_send2_wrapped: resetting send seqnr 3 
debug1: rekey out after 134217728 blocks 
debug1: SSH2_MSG_NEWKEYS sent 
debug1: expecting SSH2_MSG_NEWKEYS 
debug1: ssh_packet_read_poll2: resetting read seqnr 3 
debug1: SSH2_MSG_NEWKEYS received 
debug1: rekey in after 134217728 blocks 
debug1: SSH2_MSG_EXT_INFO received 
debug1: kex_ext_info_client_parse: server-sig-algs=<ssh-ed25519,sk-ssh-ed25519@openssh.com,sk-ecdsa-sha2-nistp256@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp5
21,rsa-sha2-256,rsa-sha2-512,ssh-rsa,ssh-dss> 
debug1: kex_ext_info_check_ver: ping@openssh.com=<0> 
debug1: SSH2_MSG_SERVICE_ACCEPT received 
debug1: Authentications that can continue: publickey 
debug1: Next authentication method: publickey 
debug1: get_agent_identities: bound agent to hostkey 
debug1: get_agent_identities: agent returned 1 keys 
debug1: Will attempt key: /home/dreibh/.ssh/id_rsa RSA SHA256:OUs3OwJDBnP68AygPjefw+4Nm01RiHMg0QANOIqpcSY agent 
debug1: Will attempt key: /home/dreibh/.ssh/id_ecdsa  
debug1: Will attempt key: /home/dreibh/.ssh/id_ecdsa_sk  
debug1: Will attempt key: /home/dreibh/.ssh/id_ed25519  
debug1: Will attempt key: /home/dreibh/.ssh/id_ed25519_sk  
debug1: Will attempt key: /home/dreibh/.ssh/id_xmss  
debug1: Will attempt key: /home/dreibh/.ssh/id_dsa  
debug1: Offering public key: /home/dreibh/.ssh/id_rsa RSA SHA256:OUs3OwJDBnP68AygPjefw+4Nm01RiHMg0QANOIqpcSY agent 
Connection closed by 2401:1d80:3210::bbc:1:df7c port 22

[Ben]

Hi @dreibh 

May I know your timezone so I can raise a support ticket on your behalf?

Cheers!

- Ben (Bitbucket Cloud Support)

[dreibh]

CEST (i.e. UTC+2).

[dreibh]

The problem still exists:

• My key still does not work with BitBucket. I already verified that the configured key's fingerprint matches with my key (under https://bitbucket.org/account/settings/ssh-keys/).
• Trying to add the same key again (under https://bitbucket.org/account/settings/ssh-keys/) results in "That SSH key is invalid.", without further explanation.
• The key is a 16384-bit RSA key.

[Ben]

Hi @dreibh 

I've raised a support ticket on your behalf with our AMER region team, please check your inbox for further responses :) 

Cheers!

- Ben (Bitbucket Cloud Support)

[dreibh]

I think I cannot open a ticket. Tried https://support.atlassian.com/contact/#/ , but it does not show an option to create a ticket. I am using a free account.

My SSH key is an RSA key, on an up-to-date Ubuntu 24.04 LTS. The key worked with BitBucket until a few days ago. The key is working fine for other services, so I assume my SSH client configuration is okay. The BitBucket SSH server just disconnects the TCP session when it is offered the key. There is no useful error message.

[Arkadiusz Wroblewski]

Hello @dreibh 

I have some ideas but so far I understand your ticket, that will probably need engineer investigation.

Are you able open ticket?

Best,

Arek 🤠