clone: prevent hooks from running during a clone

Critical security issues typically combine relatively common
vulnerabilities such as case confusion in file paths with other
weaknesses in order to raise the severity of the attack.

One such weakness that has haunted the Git project in many a
submodule-related CVE is that any hooks that are found are executed
during a clone operation. Examples are the `post-checkout` and
`fsmonitor` hooks.

However, Git's design calls for hooks to be disabled by default, as only
disabled example hooks are copied over from the templates in
`<prefix>/share/git-core/templates/`.

As a defense-in-depth measure, let's prevent those hooks from running.

Obviously, administrators can choose to drop enabled hooks into the
template directory, though, _and_ it is also possible to override
`core.hooksPath`, in which case the new check needs to be disabled.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

1 files changed, 51 insertions, 0 deletions

diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh
index fd02984330..20deca0231 100755
--- a/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@ -771,6 +771,57 @@ test_expect_success 'batch missing blob request does not inadvertently try to fe
 	git clone --filter=blob:limit=0 "file://$(pwd)/server" client
 '
 
+test_expect_success 'clone with init.templatedir runs hooks' '
+	git init tmpl/hooks &&
+	write_script tmpl/hooks/post-checkout <<-EOF &&
+	echo HOOK-RUN >&2
+	echo I was here >hook.run
+	EOF
+	git -C tmpl/hooks add . &&
+	test_tick &&
+	git -C tmpl/hooks commit -m post-checkout &&
+
+	test_when_finished "git config --global --unset init.templateDir || :" &&
+	test_when_finished "git config --unset init.templateDir || :" &&
+	(
+		sane_unset GIT_TEMPLATE_DIR &&
+		NO_SET_GIT_TEMPLATE_DIR=t &&
+		export NO_SET_GIT_TEMPLATE_DIR &&
+
+		git -c core.hooksPath="$(pwd)/tmpl/hooks" \
+			clone tmpl/hooks hook-run-hookspath 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-hookspath/hook.run &&
+
+		git -c init.templateDir="$(pwd)/tmpl" \
+			clone tmpl/hooks hook-run-config 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-config/hook.run &&
+
+		git clone --template=tmpl tmpl/hooks hook-run-option 2>err &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-option/hook.run &&
+
+		git config --global init.templateDir "$(pwd)/tmpl" &&
+		git clone tmpl/hooks hook-run-global-config 2>err &&
+		git config --global --unset init.templateDir &&
+		! grep "active .* hook found" err &&
+		test_path_is_file hook-run-global-config/hook.run &&
+
+		# clone ignores local `init.templateDir`; need to create
+		# a new repository because we deleted `.git/` in the
+		# `setup` test case above
+		git init local-clone &&
+		cd local-clone &&
+
+		git config init.templateDir "$(pwd)/../tmpl" &&
+		git clone ../tmpl/hooks hook-run-local-config 2>err &&
+		git config --unset init.templateDir &&
+		! grep "active .* hook found" err &&
+		test_path_is_missing hook-run-local-config/hook.run
+	)
+'
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd