git/Documentation/git-shell.txt
Jonathan Nieder 35297089e5 shell: new no-interactive-login command to print a custom message
If I disable git-shell's interactive mode by removing the
~/git-shell-commands directory, attempts to ssh in to the service
produce a message intended for the administrator:

	$ ssh git@myserver
	fatal: Interactive git shell is not enabled.
	hint: ~/git-shell-commands should exist and have read and execute access.
	$

That is helpful for the new admin who is wondering "What? Why isn't
the git-shell I just set up working?", but once the site setup is
complete, it would be better to give the user a friendly hint that she
is on the right track, like GitHub does.

	Hi <username>! You've successfully authenticated, but
	GitHub does not provide shell access.

An appropriate greeting might even include more complex dynamic
information, like gitolite's list of repositories the user has access
to.  Add support for a ~/git-shell-commands/no-interactive-login
command that generates an arbitrary greeting.  When the user tries to
log in:

 * If the file ~/git-shell-commands/no-interactive-login exists,
   run no-interactive-login to let the server say what it likes,
   then hang up.

 * Otherwise, if ~/git-shell-commands/ is present, start an
   interactive read-eval-print loop.

 * Otherwise, print the usual configuration hint and hang up.

Reported-by: Ethan Reesor <firelizzard@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Improved-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-09 23:21:35 -08:00

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git-shell(1)
============
NAME
----
git-shell - Restricted login shell for Git-only SSH access
SYNOPSIS
--------
[verse]
'chsh' -s $(command -v git-shell) <user>
'git clone' <user>`@localhost:/path/to/repo.git`
'ssh' <user>`@localhost`
DESCRIPTION
-----------
This is a login shell for SSH accounts to provide restricted Git access.
It permits execution only of server-side Git commands implementing the
pull/push functionality, plus custom commands present in a subdirectory
named `git-shell-commands` in the user's home directory.
COMMANDS
--------
'git shell' accepts the following commands after the '-c' option:
'git receive-pack <argument>'::
'git upload-pack <argument>'::
'git upload-archive <argument>'::
Call the corresponding server-side command to support
the client's 'git push', 'git fetch', or 'git archive --remote'
request.
'cvs server'::
Imitate a CVS server. See linkgit:git-cvsserver[1].
If a `~/git-shell-commands` directory is present, 'git shell' will
also handle other, custom commands by running
"`git-shell-commands/<command> <arguments>`" from the user's home
directory.
INTERACTIVE USE
---------------
By default, the commands above can be executed only with the '-c'
option; the shell is not interactive.
If a `~/git-shell-commands` directory is present, 'git shell'
can also be run interactively (with no arguments). If a `help`
command is present in the `git-shell-commands` directory, it is
run to provide the user with an overview of allowed actions. Then a
"git> " prompt is presented at which one can enter any of the
commands from the `git-shell-commands` directory, or `exit` to close
the connection.
Generally this mode is used as an administrative interface to allow
users to list repositories they have access to, create, delete, or
rename repositories, or change repository descriptions and
permissions.
If a `no-interactive-login` command exists, then it is run and the
interactive shell is aborted.
EXAMPLE
-------
To disable interactive logins, displaying a greeting instead:
+
----------------
$ chsh -s /usr/bin/git-shell
$ mkdir $HOME/git-shell-commands
$ cat >$HOME/git-shell-commands/no-interactive-login <<\EOF
#!/bin/sh
printf '%s\n' "Hi $USER! You've successfully authenticated, but I do not"
printf '%s\n' "provide interactive shell access."
exit 128
EOF
$ chmod +x $HOME/git-shell-commands/no-interactive-login
----------------
SEE ALSO
--------
ssh(1),
linkgit:git-daemon[1],
contrib/git-shell-commands/README
GIT
---
Part of the linkgit:git[1] suite