SSH keys in Bitbucket Cloud

[Svetlozar Petkov]

My pipeline fails when it starts to initialize the git pull command with the following error:

Host key verification failed

I created a key pair in the SSH keys section of the repository settings and added the public key to the authorized_keys file of the custom user I created on my server which uses a linux shell runner from bitbucket. I tried everything from importing the public key of the user to the my personal keys, create a known hosts file as said in some documentation and basically almost everything else, but the error persists. Can anyone provide insight as to why this is happening and how to fix it ?

[Patrik S · Accepted solution]

Hello @Svetlozar Petkov and thank you for reaching out to Atlassian Community!

When connecting to a server over SSH, one of the first things that SSH will do if to verify if the server's fingerprint match with any entry on the local known_hosts file. If no entry is found that matches your server's fingerprint, the connection will fail with "Host key verification failed".

As pipelines steps are executed in docker containers, each execution of a step is a fresh start of the container, meaning the known_hosts file within the container will just contain the default entries of the docker image you are using, which likely does not container the entry for your external server (unless you are using a custom image where you added it).

In this case, you can use the Pipelines Known Hosts feature to save your server's known hosts, so pipelines will automatically add the fingerprint to the known_hosts inside the container when the build starts. For that, you can follow below instructions:

1. Navigate to Repository Settings > SSH keys (under pipelines section)
2. Provide your server's IP address or domain name and click on Fetch
   
   
3. Bitbucket will try to fetch the fingerprint from the server. After the fingerprint is fetched, click on the now available Add Host button, as this will save that fingerprint on Bitbucket.
4. Now, for your subsequent builds, that fingerprint should be automatically added by pipelines inside the container's known_hosts file.

Hope that helps! Let me know in case you have any questions.

Thank you, @Svetlozar Petkov !

Patrik S