Git asks for password when using SSH URL, ssh does not

Question

I have three servers (two ubuntu 16.04, one mac mini) and several macbooks.

One server ubuntu is for gitlab and the other is an internal site server. The mac mini is running a CI.

Recently the gitlab server was replaced with another gitlab server. (Hardware replaced, same IP address and hostname, new software, new ssh key, all other hardware (the other servers and laptops) are using the ssh keys as before).

Any of the macbooks can SSH into either of the servers (using the username/password of a user on the server) and they can use Git to clone, push, etc with the git server via public key.

The site server can SSH (via public key) into the git server but once the welcome message appears the connection is terminated. The site server can not use git via public key as Git prompts for a password, except for when it doesn't and works using the public key which lasts for some time, it only starts to work using testing in the users documents directory, if I attempt to clone in the /var/www directory git breaks again (this may be coincidence, it has only worked twice).

The CI has no issues connecting with the git server.

Using ssh -v the output shows ssh is using the correct public key.

So running the following command on the site server

ssh [email protected] 

connects (and then disconnects) but

git clone [email protected]:somerepo.git

asks for the password of the git user.

The site server has a user (with a ssh key) registered on gitlab.

Example output from multiple calls: https://pastebin.com/QH0AntK7

Answer 1

I stumbled upon the same issue and the problem was that I did some operations in the git user's home directory as root so the authorized SSH keys file couldn't be read.

The fix was to run:

$ chown -R git:git /home/git/.ssh

Answer 2

First thing to test is whether key based SSH from site server to git server works or not. From your description, it seems it doesn't. Have your cat the public key of user on site server to git user's ~/.ssh/authoried_keys prior your run of ssh?

Answer 3

After creating the log for @LazyBadger, I've realised it only fails when run with sudo because it's using a different ssh key.

I've included the root users ssh key on the site servers account on the git server and now it works.

Answer 4

Although the OP found a solution, I was struggling as a result of another way that this can occur.

Connecting with ssh will succeed, but git fetch will ask for a password if you have configured sshcommand to use a different key in your .git/config or in your ~/.gitconfig. For example, I had something as follows (key name changed):

[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
    sshcommand = ssh -i /home/user/.ssh/repo_deploy
[remote "origin"]
    ...

Since I had used ssh-copy-id to copy /home/user/.ssh/id_rsa rather than /home/user/.ssh/repo_deploy, I had very similar outcome to the OP.