gitolite/README.mkd

# gitolite

Gitolite is an access control layer on top of git, which allows access control
down to the branch level, including specifying who can and cannot *rewind* a
given branch.

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In this document:

  * <a href="#A1">what</a>
  * <a href="#A2">why</a>
  * <a href="#A3">other features</a>
  * <a href="#A4">security</a>
  * <a href="#A5">contact and license</a>

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<a name="A1"></a>

### what

Gitolite allows a server to host many git repositories and provide access to
many developers, without having to give them real userids on or shell access
to the server.  The essential magic in doing this is ssh's pubkey access and
the `authorized_keys` file, and the inspiration was an older program called
gitosis.

Gitolite can restrict who can read from (clone/fetch) or write to (push) a
repository.  It can also restrict who can push to what branch or tag, which is
very important in a corporate environment.  Gitolite can be installed without
requiring root permissions, and with no additional software than git itself
and perl.  It also has several other neat features described below and
elsewhere in the [doc/][docs] directory.

<a name="A2"></a>

### why

Gitolite is separate from git, and needs to be installed and configured.  So...
why do we bother?

Gitolite is useful in any server that is going to host multiple git
repositories, each with many developers, where some sort of access control is
required.

In theory, this can be done with plain old Unix permissions: each user is a
member of one or more groups, each group "owns" one or more repositories, and
using unix permissions (especially the setgid bit -- `chmod g+s`) you can
allow/disallow users access to repos.

But there are several disadvantages here:

  * every user needs a userid and password on the server.  This is usually a
    killer...!
  * adding/removing access rights involves complex `usermod -G ...` mumblings
    which most admins would rather not deal with, thanks to you-know-who
  * *viewing* (aka auditing) the current set of permissions requires running
    multiple commands to list directories and their permissions/ownerships,
    users and their group memberships, and then correlating all these manually
  * auditing historical permissions or permission changes is pretty much
    impossible without extraneous tools
  * errors or omissions in setting the permissions exactly can cause problems
    of either kind: false accepts or false rejects
  * without going into ACLs it is not possible to give someone read-only
    access to a repo; they either get read-write access or no access
  * it is absolutely impossible to restrict pushing by branch name or tag
    name.

Gitolite does away with all this:

  * it uses ssh magic to remove the need to give actual unix userids to
    developers
  * it uses a simple but powerful config file format to specify access rights
  * access control changes are affected by modifying this file, adding or
    removing user's public keys, and "compiling" the configuration
  * this also makes auditing trivial -- all the data is in one place, and
    changes to the configuration are also logged, so you can audit them.
  * finally, the config file allows distinguishing between read-only and
    read-write access, not only at the repository level, but at the branch
    level within repositories.

<a name="A3"></a>

### other features

The most important feature I needed was **per-branch permissions**.  This is
pretty much mandatory in a corporate environment, and is almost the single
reason I started *thinking* about writing gitolite.

It's not just "read-only" versus "read-write".  Rewinding a branch (aka "non
fast forward push") is potentially dangerous, but sometimes needed.  So is
deleting a branch (which is really just an extreme form of rewind).  I needed
something in between allowing anyone to do it (the default) and disabling it
completely (`receive.denyNonFastForwards` or `receive.denyDeletes`).

Here're **some more features**.  All of them, and more, are documented in
detail somewhere in gitolite's [doc/][docs] subdirectory.

  * simple, yet powerful, config file syntax, including specifying
    gitweb/daemon access.  You'll need this power if you manage lots of
    users+repos+combinations of access
  * apart from branch-name based restrictions, you can also restrict by
    file/dir name changed (i.e., output of `git diff --name-only`)
  * if your requirements are still too complex, you can split up the config
    file and delegate authority over parts of it
  * easy to specify gitweb owner, description and gitweb/daemon access
  * easy to sync gitweb (http) authorisation with gitolite's access config
  * comprehensive logging [aka: management does not think "blame" is just a
    synonym for "annotate" :-)]
  * "personal namespace" prefix for each dev
  * migration guide and simple converter for gitosis conf file
  * "exclude" (or "deny") rights at the branch/tag level
  * specify repos using patterns (patterns may include creator's name)
  * define powerful operations on the server side, even github-like forking

<a name="A4"></a>

### security

Due to the environment in which this was created and the need it fills, I
consider this a "security" program, albeit a very modest one.

For the first person to find a security hole in it, defined as allowing a
normal user (not the gitolite admin) to read a repo, or write/rewind a ref,
that the config file says he shouldn't, and caused by a bug in *code* that is
in the "master" branch, (not in the other branches, or the configuration file
or in Unix, perl, shell, etc.)...  well I can't afford 1000 USD rewards like
djb, so you'll have to settle for 5000 INR (Indian Rupees) as a "token" prize
:-)

However, there are a few optional features (which must be explicitly enabled
in the RC file) where I just haven't had the time to reason about security
thoroughly enough.  Please read the comments in `conf/example.gitolite.rc` for
details, looking for the word "security".

----

<a name="A5"></a>

### contact and license

Gitolite is released under GPL v2.  See COPYING for details.

sitaramc@gmail.com
mailing list: gitolite@googlegroups.com

[docs]: http://github.com/sitaramc/gitolite/blob/pu/doc