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Git.pm: trust rev-parse to find bare repositories

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When initializing a repository object, we run "git rev-parse --git-dir"
to let the C version of Git find the correct directory. But curiously,
if this fails we don't automatically say "not a git repository".
Instead, we do our own pure-perl check to see if we're in a bare
repository.

This makes little sense, as rev-parse will report both bare and non-bare
directories. This logic comes from d5c7721d58 (Git.pm: Add support for
subdirectories inside of working copies, 2006-06-24), but I don't see
any reason given why we can't just rely on rev-parse. Worse, because we
treat any non-error response from rev-parse as a non-bare repository,
we'll erroneously set the object's WorkingCopy, even in a bare
repository.

But it gets worse. Since 8959555cee (setup_git_directory(): add an owner
check for the top-level directory, 2022-03-02), it's actively wrong (and
dangerous). The perl code doesn't implement the same ownership checks.
And worse, after "finding" the bare repository, it sets GIT_DIR in the
environment, which tells any subsequent Git commands that we've
confirmed the directory is OK, and to trust us. I.e., it re-opens the
vulnerability plugged by 8959555cee when using Git.pm's repository
discovery code.

We can fix this by just relying on rev-parse to tell us when we're not
in a repository, which fixes the vulnerability. Furthermore, we'll ask
its --is-bare-repository function to tell us if we're bare or not, and
rely on that.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2022-10-22 18:08:59 -04:00
committed by Junio C Hamano
parent 77a1310e6b
commit 20da61f25f
3 changed files with 32 additions and 20 deletions
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36
perl/Git.pm
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@ -177,16 +177,27 @@ sub repository {
-d $opts{Directory} or throw Error::Simple("Directory not found: $opts{Directory} $!");
my $search = Git->repository(WorkingCopy => $opts{Directory});
my $dir;
# This rev-parse will throw an exception if we're not in a
# repository, which is what we want, but it's kind of noisy.
# Ideally we'd capture stderr and relay it, but doing so is
# awkward without depending on it fitting in a pipe buffer. So
# we just reproduce a plausible error message ourselves.
my $out;
try {
$dir = $search->command_oneline(['rev-parse', '--git-dir'],
STDERR => 0);
# Note that "--is-bare-repository" must come first, as
# --git-dir output could contain newlines.
$out = $search->command([qw(rev-parse --is-bare-repository --git-dir)],
STDERR => 0);
} catch Git::Error::Command with {
$dir = undef;
throw Error::Simple("fatal: not a git repository: $opts{Directory}");
};
chomp $out;
my ($bare, $dir) = split /\n/, $out, 2;
require Cwd;
if ($dir) {
if ($bare ne 'true') {
require File::Spec;
File::Spec->file_name_is_absolute($dir) or $dir = $opts{Directory} . '/' . $dir;
$opts{Repository} = Cwd::abs_path($dir);
@ -204,21 +215,6 @@ sub repository {
$opts{WorkingSubdir} = $prefix;
} else {
# A bare repository? Let's see...
$dir = $opts{Directory};
unless (-d "$dir/refs" and -d "$dir/objects" and -e "$dir/HEAD") {
# Mimic git-rev-parse --git-dir error message:
throw Error::Simple("fatal: Not a git repository: $dir");
}
my $search = Git->repository(Repository => $dir);
try {
$search->command('symbolic-ref', 'HEAD');
} catch Git::Error::Command with {
# Mimic git-rev-parse --git-dir error message:
throw Error::Simple("fatal: Not a git repository: $dir");
};
$opts{Repository} = Cwd::abs_path($dir);
}