check-acls.pl - Git::Hooks plugin for branch/tag access control.
This Git::Hooks plugin can act as any of the below hooks to guarantee that only allowed users can push commits and tags to specific branches.
update
This hook is invoked multiple times in the remote repository during git push, once per branch being updated, checking if the user performing the push can update the branch in question.
git push
pre-receive
This hook is invoked once in the remote repository during git push, checking if the user performing the push can update every affected branch.
To enable it you should define the appropriate Git configuration option:
git config --add githooks.update check-acls.pl git config --add githooks.pre-receive check-acls.pl
The plugin is configured by the following git options.
When Git is performing its chores in the server to serve a push request it's usually invoked via the SSH or a web service, which take care of the authentication procedure. These services normally make the autenticated user name available in an environment variable. You may tell this hook which environment variable it is by setting this option to the variable's name. If not set, the hook will try to get the user's name from the USER environment variable and die if it's not set.
USER
You can define user groups in order to make it easier to configure general acls. Use this option to tell where to find group definitions in one of these ways:
As a text file named by PATH/TO/FILE, which may be absolute or relative to the hooks current directory, which is usually the repository's root in the server. It's syntax is very simple. Blank lines are skipped. The hash (#) character starts a comment that goes to the end of the current line. Group definitions are lines like this:
groupA = userA userB @groupB userC
Each group must be defined in a single line. Spaces are significant only between users and group references.
Note that a group can reference other groups by name. To make a group reference, simple prefix its name with an at sign (@). Group references must reference groups previously defined in the file.
If the option's value doesn't start with any of the above prefixes, it must contain the group definitions itself.
When this hook is installed, by default no user can change any reference in the repository, unless she has an explicit allowance given by one ACL (se the check-acls.acl option below). It may be usefull to give full access to a group of admins who shouldn't be subject to the ACL specifications. You may use one or more such options to give admin access to a group of people. The value of each option is interpreted in one of these ways:
A username specifying a single user. The username specification must match "/^\w+$/i" and will be compared to the authenticated user's name case sensitively.
username
A groupname specifying a single group. The groupname specification must follow the same rules as the username above.
groupname
A regex which will be matched against the authenticated user's name case-insensitively. The caret is part of the regex, meaning that it's anchored at the start of the username.
regex
The authorization specification for a repository is defined by the set of ACLs defined by this option. Each ACL specify 'who' has 'what' kind of access to which refs, by means of a string with three components separated by spaces:
who what refs
By default, nobody has access to anything, except the above-specified admins. During an update, all the ACLs are processed in the order defined by the git config --list command. The first ACL matching the authenticated username and the affected reference name (usually a branch) defines what operations are allowed. If no ACL matches username and reference name, then the operation is denied.
git config --list
The 'who' component specifies to which users this ACL gives access. It can be specified in the same three ways as was explained to the check-acls.admin option above.
The 'what' component specifies what kind of access to allow. It's specified as a string of one or more of the following opcodes:
Create a new ref.
Rewind/Rebase an existing ref. (With commit loss.)
Update an existing ref. (A fast-forward with no commit loss.)
Delete an existing ref.
You may specify that the user has no access whatsoever to the references by using a single hifen (-) as the what component.
-
The 'refs' component specifies which refs this ACL applies to. It can be specified in one of these formats:
A regular expression anchored at the beginning of the reference name. For example, "^refs/heads", meaning every branch.
A negated regular expression. For example, "!^refs/heads/master", meaning everything but the master branch.
The complete name of a reference. For example, "refs/heads/master".
The refs component can embed strings in the format {VAR}. These strings are substituted by the corresponding environment's variable VAR value. This interpolation ocurrs before the refs component is matched agains the reference name.
{VAR}
This is useful, for instance, if you want developers to be restricted in what they can do to oficial branches but to have complete control with their own branch namespace.
git config check-acls.acl '^. CRUD ^refs/heads/{USER}/' git config check-acls.acl '^. U ^refs/heads'
In this example, every user (^.) has complete control (CRUD) to the branches below "refs/heads/{USER}". Supposing the environment variable USER contains the user's login name during a "pre-receive" hook. For all other branches (^refs/heads) the users have only update (U) rights.
This script is heavily inspired (and, in some places, derived) from the update-paranoid example hook which comes with the Git distribution (https://github.com/gitster/git/blob/b12905140a8239ac687450ad43f18b5f0bcfb62e/contrib/hooks/update-paranoid).
To install Git::Hooks, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Git::Hooks
CPAN shell
perl -MCPAN -e shell install Git::Hooks
For more information on module installation, please visit the detailed CPAN module installation guide.