Specify an SSH key for git push for a given domain

Question

I have the following use case: I would like to be able to push to git@git.company.com:gitolite-admin using the private key of user gitolite-admin, while I want to push to git@git.company.com:some_repo using 'my own' private key. AFAIK, I can't solve this using ~/.ssh/config, because the user name and server name are identical in both cases. As I mostly use my own private key, I have that defined in ~/.ssh/config for git@git.company.com. Does anyone know of a way to override the key that is used for a single git invocation?

(Aside: gitolite distinguishes who is doing the pushing based on the key, so it's not a problem, in terms of access, ownership and auditing, that the user@server string is identical for different users.)

Answer 1

Even if the user and host are the same, they can still be distinguished in ~/.ssh/config. For example, if your configuration looks like this:

Host gitolite-as-alice
  HostName git.company.com
  User git
  IdentityFile /home/whoever/.ssh/id_rsa.alice
  IdentitiesOnly yes

Host gitolite-as-bob
  HostName git.company.com
  User git
  IdentityFile /home/whoever/.ssh/id_dsa.bob
  IdentitiesOnly yes

Then you just use gitolite-as-alice and gitolite-as-bob instead of the hostname in your URL:

git remote add alice git@gitolite-as-alice:whatever.git
git remote add bob git@gitolite-as-bob:whatever.git

Note

You want to include the option IdentitiesOnly yes to prevent the use of default ids. Otherwise, if you also have id files matching the default names, they will get tried first because unlike other config options (which abide by "first in wins") the IdentityFile option appends to the list of identities to try. See: https://serverfault.com/questions/450796/how-could-i-stop-ssh-offering-a-wrong-key/450807#450807

Answer 2

An alternative approach to the one offered above by Mark Longair is to use an alias that will run any git command, on any remote, with an alternative SSH key. The idea is basically to switch your SSH identity when running the git commands.

Advantages relative to the host alias approach in the other answer:

• Will work with any git commands or aliases, even if you can't specify the remote explicitly.
• Easier to work with many repositories because you only need to set it up once per client machine, not once per repository on each client machine.

I use a few small scripts and a git alias admin. That way I can do, for example:

git admin push 

To push to the default remote using the alternative ("admin") SSH key. Again, you could use any command (not just push) with this alias. You could even do git admin clone ... to clone a repository that you would only have access to using your "admin" key.

Step 1: Create the alternative SSH keys, optionally set a passphrase in case you're doing this on someone else's machine.

Step 2: Create a script called “ssh-as.sh” that runs stuff that uses SSH, but uses a given SSH key rather than the default:

#!/bin/bash
exec ssh ${SSH_KEYFILE+-i "$SSH_KEYFILE"} "$@"

Step 3: Create a script called “git-as.sh” that runs git commands using the given SSH key.

#!/bin/bash
SSH_KEYFILE=$1 GIT_SSH=${BASH_SOURCE%/*}/ssh-as.sh exec git "${@:2}"

Step 4: Add an alias (using something appropriate for “PATH_TO_SCRIPTS_DIR” below):

# Run git commands as the SSH identity provided by the keyfile ~/.ssh/admin
git config --global alias.admin \!"PATH_TO_SCRIPTS_DIR/git-as.sh ~/.ssh/admin"

More details at: http://noamlewis.wordpress.com/2013/01/24/git-admin-an-alias-for-running-git-commands-as-a-privileged-ssh-identity/

Answer 3

You can utilize git environment variable GIT_SSH_COMMAND. Run this in your terminal under your git repository:

GIT_SSH_COMMAND='ssh -i ~/.ssh/your_private_key' git submodule update --init

Replace ~/.ssh/your_private_key with the path of ssh private key you wanna use. And you can change the subsequent git command (in the example is git submodule update --init) to others like git pull, git fetch, etc.

Answer 4

One Unix based systems (Linux, BSD, Mac OS X), the default identity is stored in the directory $HOME/.ssh, in 2 files: private key: $HOME/.ssh/id_rsa public key: $HOME/.ssh/id_rsa.pub When you use ssh without option -i, it uses the default private key to authenticate with remote system.

If you have another private key you want to use, for example $HOME/.ssh/deploy_key, you have to use ssh -i ~/.ssh/deploy_key ...

It is annoying. You can add the following lines in to your $HOME/.bash_profile : ssh-add ~/.ssh/deploy_key ssh-add ~/.ssh/id_rsa

So each time you use ssh or git or scp (basically ssh too), you don't have to use option -i anymore.

You can add as many keys as you like in the file $HOME/.bash_profile.

Answer 5

Another alternative is to use ssh-ident, to manage your ssh identities.

It automatically loads and uses different keys based on your current working directory, ssh options, and so on... which means you can easily have a work/ directory and private/ directory that transparently end up using different keys and identities with ssh.

Answer 6

I am using Git Bash on Win7. The following worked for me.

Create a config file at ~/.ssh/config or c:/users/[your_user_name]/.ssh/config. In the file enter:

Host your_host.com
     IdentityFile [absolute_path_to_your_.ssh]\id_rsa

I guess the host has to be a URL and not just a "name" or ref for your host. For example,

Host github.com
     IdentityFile c:/users/[user_name]/.ssh/id_rsa

The path can also be written in /c/users/[user_name]/.... format

The solution provided by Giordano Scalzo is great too. https://stackoverflow.com/a/9149518/1738546

Answer 7

If using Git's version of ssh on windows, the identity file line in the ssh config looks like

IdentityFile /c/Users/Whoever/.ssh/id_rsa.alice

where /c is for c:

To check, in git's bash do

cd ~/.ssh
pwd 

Answer 8

You might need to remove (or comment out) default Host configuration

Answer 9

From git 2.10 upwards it is also possible to use the gitconfig sshCommand setting. Docs state :

If this variable is set, git fetch and git push will use the specified command instead of ssh when they need to connect to a remote system. The command is in the same form as the GIT_SSH_COMMAND environment variable and is overridden when the environment variable is set.

An usage example would be: git config core.sshCommand "ssh -i ~/.ssh/[insert_your_keyname]

In some cases this doesn't work because ssh_config overriding the command, in this case try ssh -i ~/.ssh/[insert_your_keyname] -F /dev/null to not use the ssh_config.

Answer 10

you most specified in the file config key ssh:

# Default GitHub user
Host one
 HostName gitlab.com
 User git
 PreferredAuthentications publickey
 IdentityFile ~/.ssh/key-one
 IdentitiesOnly yes

#two user
Host two
 HostName gitlab.com
 User git
 PreferredAuthentications publickey
 IdentityFile ~/.ssh/key-two
 IdentitiesOnly yes