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diff --git a/Documentation/howto/update-hook-example.txt b/Documentation/howto/update-hook-example.txt new file mode 100644 index 000000000000..89821ec74fe1 --- /dev/null +++ b/Documentation/howto/update-hook-example.txt @@ -0,0 +1,192 @@ +From: Junio C Hamano <gitster@pobox.com> and Carl Baldwin <cnb@fc.hp.com> +Subject: control access to branches. +Date: Thu, 17 Nov 2005 23:55:32 -0800 +Message-ID: <7vfypumlu3.fsf@assigned-by-dhcp.cox.net> +Abstract: An example hooks/update script is presented to + implement repository maintenance policies, such as who can push + into which branch and who can make a tag. +Content-type: text/asciidoc + +How to use the update hook +========================== + +When your developer runs git-push into the repository, +git-receive-pack is run (either locally or over ssh) as that +developer, so is hooks/update script. Quoting from the relevant +section of the documentation: + + Before each ref is updated, if $GIT_DIR/hooks/update file exists + and executable, it is called with three parameters: + + $GIT_DIR/hooks/update refname sha1-old sha1-new + + The refname parameter is relative to $GIT_DIR; e.g. for the + master head this is "refs/heads/master". Two sha1 are the + object names for the refname before and after the update. Note + that the hook is called before the refname is updated, so either + sha1-old is 0{40} (meaning there is no such ref yet), or it + should match what is recorded in refname. + +So if your policy is (1) always require fast-forward push +(i.e. never allow "git-push repo +branch:branch"), (2) you +have a list of users allowed to update each branch, and (3) you +do not let tags to be overwritten, then you can use something +like this as your hooks/update script. + +[jc: editorial note. This is a much improved version by Carl +since I posted the original outline] + +---------------------------------------------------- +#!/bin/bash + +umask 002 + +# If you are having trouble with this access control hook script +# you can try setting this to true. It will tell you exactly +# why a user is being allowed/denied access. + +verbose=false + +# Default shell globbing messes things up downstream +GLOBIGNORE=* + +function grant { + $verbose && echo >&2 "-Grant- $1" + echo grant + exit 0 +} + +function deny { + $verbose && echo >&2 "-Deny- $1" + echo deny + exit 1 +} + +function info { + $verbose && echo >&2 "-Info- $1" +} + +# Implement generic branch and tag policies. +# - Tags should not be updated once created. +# - Branches should only be fast-forwarded unless their pattern starts with '+' +case "$1" in + refs/tags/*) + git rev-parse --verify -q "$1" && + deny >/dev/null "You can't overwrite an existing tag" + ;; + refs/heads/*) + # No rebasing or rewinding + if expr "$2" : '0*$' >/dev/null; then + info "The branch '$1' is new..." + else + # updating -- make sure it is a fast-forward + mb=$(git merge-base "$2" "$3") + case "$mb,$2" in + "$2,$mb") info "Update is fast-forward" ;; + *) noff=y; info "This is not a fast-forward update.";; + esac + fi + ;; + *) + deny >/dev/null \ + "Branch is not under refs/heads or refs/tags. What are you trying to do?" + ;; +esac + +# Implement per-branch controls based on username +allowed_users_file=$GIT_DIR/info/allowed-users +username=$(id -u -n) +info "The user is: '$username'" + +if test -f "$allowed_users_file" +then + rc=$(cat $allowed_users_file | grep -v '^#' | grep -v '^$' | + while read heads user_patterns + do + # does this rule apply to us? + head_pattern=${heads#+} + matchlen=$(expr "$1" : "${head_pattern#+}") + test "$matchlen" = ${#1} || continue + + # if non-ff, $heads must be with the '+' prefix + test -n "$noff" && + test "$head_pattern" = "$heads" && continue + + info "Found matching head pattern: '$head_pattern'" + for user_pattern in $user_patterns; do + info "Checking user: '$username' against pattern: '$user_pattern'" + matchlen=$(expr "$username" : "$user_pattern") + if test "$matchlen" = "${#username}" + then + grant "Allowing user: '$username' with pattern: '$user_pattern'" + fi + done + deny "The user is not in the access list for this branch" + done + ) + case "$rc" in + grant) grant >/dev/null "Granting access based on $allowed_users_file" ;; + deny) deny >/dev/null "Denying access based on $allowed_users_file" ;; + *) ;; + esac +fi + +allowed_groups_file=$GIT_DIR/info/allowed-groups +groups=$(id -G -n) +info "The user belongs to the following groups:" +info "'$groups'" + +if test -f "$allowed_groups_file" +then + rc=$(cat $allowed_groups_file | grep -v '^#' | grep -v '^$' | + while read heads group_patterns + do + # does this rule apply to us? + head_pattern=${heads#+} + matchlen=$(expr "$1" : "${head_pattern#+}") + test "$matchlen" = ${#1} || continue + + # if non-ff, $heads must be with the '+' prefix + test -n "$noff" && + test "$head_pattern" = "$heads" && continue + + info "Found matching head pattern: '$head_pattern'" + for group_pattern in $group_patterns; do + for groupname in $groups; do + info "Checking group: '$groupname' against pattern: '$group_pattern'" + matchlen=$(expr "$groupname" : "$group_pattern") + if test "$matchlen" = "${#groupname}" + then + grant "Allowing group: '$groupname' with pattern: '$group_pattern'" + fi + done + done + deny "None of the user's groups are in the access list for this branch" + done + ) + case "$rc" in + grant) grant >/dev/null "Granting access based on $allowed_groups_file" ;; + deny) deny >/dev/null "Denying access based on $allowed_groups_file" ;; + *) ;; + esac +fi + +deny >/dev/null "There are no more rules to check. Denying access" +---------------------------------------------------- + +This uses two files, $GIT_DIR/info/allowed-users and +allowed-groups, to describe which heads can be pushed into by +whom. The format of each file would look like this: + + refs/heads/master junio + +refs/heads/pu junio + refs/heads/cogito$ pasky + refs/heads/bw/.* linus + refs/heads/tmp/.* .* + refs/tags/v[0-9].* junio + +With this, Linus can push or create "bw/penguin" or "bw/zebra" +or "bw/panda" branches, Pasky can do only "cogito", and JC can +do master and pu branches and make versioned tags. And anybody +can do tmp/blah branches. The '+' sign at the pu record means +that JC can make non-fast-forward pushes on it. |