update.detect-dup-pubkeys

#!/bin/bash

# update "hooklet" to detect duplicate public keys

# This particular hooklet also serves as an example for people writing others.
# [It should be quite easy to figure out what parts apply to any hooklet and
# what parts are specific to *this* hooklet and its function.]

# see hooks/common/update.secondary.sample for instructions on *enabling*
# hooklets

# a hooklet is called as follows:
#   git-receive-pack --> 'update' --> 'update.secondary' --> this script
# note: the same three arguments that git passes to the update hook are passed
# along to each hooklet.

# the update hook, and therefore the hooklets, are called for *every* repo out
# there.  If you want this hooklet to run only for certain repos, here's how:
[ "$GL_REPO" = "gitolite-admin" ] || exit 0

# superfluous, since update.secondary already did it, but I'd like to
# emphasise that all output MUST go to STDERR
exec >&2

# ----

# the main functionality of the hooklet starts here.  In this one (and I
# suspect many others) we want to examine the actual files from the commit
# that was pushed.

# get the tip commit being pushed
sha=$3

# git sets this; and we don't want it at this point...
unset GIT_DIR

# paranoia
set -e

# setup the temp area
export TMPDIR=$GL_REPO_BASE_ABS
export tmp=$(mktemp -d -t gl-internal-temp-repo.XXXXXXXXXX);
trap "rm -rf $tmp" EXIT;

# now get the files into $tmp.
    # (note: if your task does not require the actual files, and you can
    # manage with "git cat-file -s" and so on, then you may not even need a
    # $tmp; you may be able to do it all right in the repo.git directory)

git archive $sha keydir | tar -C $tmp -xf -
    # DO NOT try, say, 'GIT_WORK_TREE=$tmp git checkout $sha'.  It'll screw up
    # both the 'index' and 'HEAD' of the repo.git.  Screwing up the index is
    # BAD because now it goes out of sync with $GL_ADMINDIR.  Think of a push
    # that had a deleted pubkey but failed a hooklet for some reason.  A
    # subsequent push that fixes the error will now result in a $GL_ADMINDIR
    # that still *has* that deleted pubkey!!

    # And this is equally applicable to cases where you're using a
    # post-receive or similar hook to live update a web site or something,
    # which is a pretty common usage, I am given to understand.

cd $tmp

# ----

# *finally*, the actual check you need to do in this hook: look for duplicate
# pubkeys and exit 1 if dups are found
for f in `find keydir -name "*.pub"`
do
    ssh-keygen -l -f "$f"
done | perl -ane '
    die "$F[2] is a duplicate of $seen{$F[1]}\n" if $seen{$F[1]};
    $seen{$F[1]} = $F[2];
'