I have a git server where people set up remote repositories over ssh, and there's a git user that they all connect as which has secure permissions and whatnot.
I'm editing the pre-receive hook in a repo so that it sees if the environment variable, $GIT_USER, matches the list of allowed users for that repo to prevent unauthorized users from pushing.
This environment variable is set individually in the git user's .ssh/authorized_keys file.
However, I don't want environment variables to be set for ssh for any user besides git.
Is there any way to edit /etc/ssh/sshd_config such that PermitUserEnvironment is only enabled for the git user?
You can set "PermitUserEnvironment no" and at the bottom of sshd_config you can override settings on a per-user basis:
Match User git
PermitUserEnvironment yes
That should accomplish what you want.