more complex ssh setups

What do you need to know in order to create more complex ssh setups (for instance if you have two gitolite servers you are administering)? Once more unto the breach, here's more ssh magic!

In this document:

files on client
files on the server
sanity checks
two gitolite servers to manage?

But before we get to all that, let's clarify that all this is applicable only to the gitolite admin. He's the only one who needs both a shell and gitolite access, so he has two pubkeys in play.

Normal users have only one pubkey, since they are only allowed to access gitolite itself. They do not need to worry about any of this ~/.ssh/config stuff, and their repo urls are very simple, like: git@my.git.server:reponame.git.

files on client

default keypair; used to get shell access to servers. You would have copied this pubkey to the gitolite server in order to log in without a password. (On Linux systems you may have used ssh-copy-id to do that). You would have done this before you ran the easy install script, because otherwise easy install won't run!
```
~/.ssh/id_rsa
~/.ssh/id_rsa.pub
```
gitolite keypair; the "sitaram" in this is the 3rd argument to the src/00-easy-install.sh command you ran; the easy install script does the rest
```
~/.ssh/sitaram
~/.ssh/sitaram.pub
```

files on the server

the authkeys file; this contains one line containing the pubkey of each user who is permitted to login without a password.

Pubkey lines that give shell access look like this:
```
ssh-rsa AAAAB3NzaC[snip]uPjrUiAUew== /home/sitaram/.ssh/id_rsa
```
On a typical server there will be only one or two of these lines.

Note that the last bit (/home/sitaram/.ssh/id_rsa) is purely a comment field and can be anything. Also, the actual lines are much longer, about 400 characters; I snipped 'em in the middle, as you can see.

In contrast, pubkey lines that give access to git repos hosted by gitolite looks like this:
```
command="[some path]src/gl-auth-command sitaram",[some restrictions] ssh-rsa AAAAB3NzaC[snip]s18OnB42oQ== sitaram@sita-lt
```
You will have many more of these lines -- one for every pubkey file in keydir/ of your gitolite-admin repo, with the corresponding username in place of "sitaram" in the example above.

The "command=" at the beginning ensures that when someone with the corresponding private key logs in, they don't get a shell. Instead, the gl-auth-command program is run, and (in this example) is given the argument sitaram. This is how gitolite is invoked, (and is told the user logging in is "sitaram").
config file; this file has an entry for gitolite access:
```
~/.ssh/config
```
Let's step back a bit. Normally, you might expect to access gitolite repos like this:
```
ssh://git@server/reponame.git
```
But this won't work, because this ends up using the default keypair (normally), which gives you a command line. Which means it won't invoke the gl-auth-command program at all, and so none of gitolite's access control will work.

You need to force ssh to use the other keypair when performing a git operation. With just ssh, that would be
```
ssh -i ~/.ssh/sitaram git@server
```
but git does not support putting an alternate keypair in the URL.

Luckily, ssh has a very convenient way of capturing all the mundane information (username, hostname, port number (if it's not the default 22), and keypair to be used) in one "paragraph". This is what the para looks like for us (the easy install script puts it there the first time):
```
host gitolite
     user git
     hostname server
     identityfile ~/.ssh/sitaram
```
(The "gitolite" can be anything you want of course; it's like an alias for all the stuff below it). This ensures that typing
```
ssh gitolite
```
is equivalent to
```
ssh -i ~/.ssh/sitaram git@server
```
and therefore this:
```
git clone gitolite:reponame.git
```
now works as expected, invoking the special keypair instead of the default one.

sanity checks

ssh gitolite should get you the SSH_ORIGINAL_COMMAND error. If you get a command line, something is wrong
conversely, ssh git@server should get you a command line
the "origin" URL in any clones should look like gitolite:reponame.git instead of something more complex

two gitolite servers to manage?

they can have the same key; no harm there (example, sitaram.pub)

instead of just one ssh/config para, you now have two (assuming that the remote user on both machines is called "git"):

host gitolite
     user git
     hostname server
     identityfile ~/.ssh/sitaram

host gitolite2
     user git
     hostname server2
     identityfile ~/.ssh/sitaram

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more complex ssh setups

files on client

files on the server

sanity checks

two gitolite servers to manage?

5 KiB

Raw Blame History