192 lines
6.1 KiB
Text
192 lines
6.1 KiB
Text
From: Junio C Hamano <gitster@pobox.com> and Carl Baldwin <cnb@fc.hp.com>
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Subject: control access to branches.
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Date: Thu, 17 Nov 2005 23:55:32 -0800
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Message-ID: <7vfypumlu3.fsf@assigned-by-dhcp.cox.net>
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Abstract: An example hooks/update script is presented to
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implement repository maintenance policies, such as who can push
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into which branch and who can make a tag.
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Content-type: text/asciidoc
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How to use the update hook
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==========================
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When your developer runs git-push into the repository,
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git-receive-pack is run (either locally or over ssh) as that
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developer, so is hooks/update script. Quoting from the relevant
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section of the documentation:
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Before each ref is updated, if $GIT_DIR/hooks/update file exists
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and executable, it is called with three parameters:
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$GIT_DIR/hooks/update refname sha1-old sha1-new
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The refname parameter is relative to $GIT_DIR; e.g. for the
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master head this is "refs/heads/master". Two sha1 are the
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object names for the refname before and after the update. Note
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that the hook is called before the refname is updated, so either
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sha1-old is 0{40} (meaning there is no such ref yet), or it
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should match what is recorded in refname.
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So if your policy is (1) always require fast-forward push
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(i.e. never allow "git-push repo +branch:branch"), (2) you
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have a list of users allowed to update each branch, and (3) you
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do not let tags to be overwritten, then you can use something
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like this as your hooks/update script.
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[jc: editorial note. This is a much improved version by Carl
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since I posted the original outline]
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----------------------------------------------------
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#!/bin/bash
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umask 002
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# If you are having trouble with this access control hook script
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# you can try setting this to true. It will tell you exactly
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# why a user is being allowed/denied access.
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verbose=false
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# Default shell globbing messes things up downstream
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GLOBIGNORE=*
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function grant {
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$verbose && echo >&2 "-Grant- $1"
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echo grant
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exit 0
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}
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function deny {
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$verbose && echo >&2 "-Deny- $1"
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echo deny
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exit 1
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}
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function info {
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$verbose && echo >&2 "-Info- $1"
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}
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# Implement generic branch and tag policies.
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# - Tags should not be updated once created.
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# - Branches should only be fast-forwarded unless their pattern starts with '+'
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case "$1" in
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refs/tags/*)
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git rev-parse --verify -q "$1" &&
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deny >/dev/null "You can't overwrite an existing tag"
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;;
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refs/heads/*)
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# No rebasing or rewinding
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if expr "$2" : '0*$' >/dev/null; then
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info "The branch '$1' is new..."
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else
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# updating -- make sure it is a fast-forward
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mb=$(git merge-base "$2" "$3")
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case "$mb,$2" in
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"$2,$mb") info "Update is fast-forward" ;;
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*) noff=y; info "This is not a fast-forward update.";;
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esac
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fi
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;;
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*)
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deny >/dev/null \
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"Branch is not under refs/heads or refs/tags. What are you trying to do?"
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;;
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esac
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# Implement per-branch controls based on username
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allowed_users_file=$GIT_DIR/info/allowed-users
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username=$(id -u -n)
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info "The user is: '$username'"
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if test -f "$allowed_users_file"
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then
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rc=$(cat $allowed_users_file | grep -v '^#' | grep -v '^$' |
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while read heads user_patterns
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do
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# does this rule apply to us?
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head_pattern=${heads#+}
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matchlen=$(expr "$1" : "${head_pattern#+}")
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test "$matchlen" = ${#1} || continue
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# if non-ff, $heads must be with the '+' prefix
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test -n "$noff" &&
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test "$head_pattern" = "$heads" && continue
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info "Found matching head pattern: '$head_pattern'"
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for user_pattern in $user_patterns; do
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info "Checking user: '$username' against pattern: '$user_pattern'"
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matchlen=$(expr "$username" : "$user_pattern")
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if test "$matchlen" = "${#username}"
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then
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grant "Allowing user: '$username' with pattern: '$user_pattern'"
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fi
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done
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deny "The user is not in the access list for this branch"
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done
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)
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case "$rc" in
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grant) grant >/dev/null "Granting access based on $allowed_users_file" ;;
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deny) deny >/dev/null "Denying access based on $allowed_users_file" ;;
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*) ;;
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esac
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fi
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allowed_groups_file=$GIT_DIR/info/allowed-groups
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groups=$(id -G -n)
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info "The user belongs to the following groups:"
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info "'$groups'"
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if test -f "$allowed_groups_file"
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then
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rc=$(cat $allowed_groups_file | grep -v '^#' | grep -v '^$' |
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while read heads group_patterns
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do
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# does this rule apply to us?
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head_pattern=${heads#+}
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matchlen=$(expr "$1" : "${head_pattern#+}")
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test "$matchlen" = ${#1} || continue
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# if non-ff, $heads must be with the '+' prefix
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test -n "$noff" &&
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test "$head_pattern" = "$heads" && continue
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info "Found matching head pattern: '$head_pattern'"
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for group_pattern in $group_patterns; do
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for groupname in $groups; do
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info "Checking group: '$groupname' against pattern: '$group_pattern'"
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matchlen=$(expr "$groupname" : "$group_pattern")
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if test "$matchlen" = "${#groupname}"
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then
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grant "Allowing group: '$groupname' with pattern: '$group_pattern'"
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fi
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done
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done
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deny "None of the user's groups are in the access list for this branch"
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done
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)
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case "$rc" in
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grant) grant >/dev/null "Granting access based on $allowed_groups_file" ;;
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deny) deny >/dev/null "Denying access based on $allowed_groups_file" ;;
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*) ;;
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esac
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fi
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deny >/dev/null "There are no more rules to check. Denying access"
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----------------------------------------------------
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This uses two files, $GIT_DIR/info/allowed-users and
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allowed-groups, to describe which heads can be pushed into by
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whom. The format of each file would look like this:
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refs/heads/master junio
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+refs/heads/pu junio
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refs/heads/cogito$ pasky
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refs/heads/bw/.* linus
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refs/heads/tmp/.* .*
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refs/tags/v[0-9].* junio
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With this, Linus can push or create "bw/penguin" or "bw/zebra"
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or "bw/panda" branches, Pasky can do only "cogito", and JC can
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do master and pu branches and make versioned tags. And anybody
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can do tmp/blah branches. The '+' sign at the pu record means
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that JC can make non-fast-forward pushes on it.
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