[PATCH 6/8] hooks(clone protections): special-case current Git LFS hooks

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

A notable regression in v2.45.1 and friends (all the way down to
v2.39.4) has been that Git LFS-enabled clones error out with a message
indicating that the `post-checkout` hook has been tampered with while
cloning, and as a safety measure it is not executed.

A generic fix for benign third-party applications wishing to write hooks
during clone operations has been implemented in the parent of this
commit: said applications are expected to add `safe.hook.sha256` values
to a protected config.

However, the current version of Git LFS, v3.5.1, cannot be adapted
retroactively; Therefore, let's just hard-code the SHA-256 values for
this version. That way, Git LFS usage will no longer be broken, and the
next Git LFS version can be taught to add those `safe.hook.sha256`
entries.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 hook.c          | 11 +++++++++++
 t/t1800-hook.sh | 20 ++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/hook.c b/hook.c
index a2479738451..f810ee133be 100644
--- a/hook.c
+++ b/hook.c
@@ -75,6 +75,17 @@ static int is_hook_safe_during_clone(const char *name, const char *path, char *s
 	if (get_sha256_of_file_contents(path, sha256) < 0)
 		return 0;
 
+	/* Hard-code known-safe values for Git LFS v3.4.0..v3.5.1 */
+	if ((!strcmp("pre-push", name) &&
+	     !strcmp(sha256, "df5417b2daa3aa144c19681d1e997df7ebfe144fb7e3e05138bd80ae998008e4")) ||
+	    (!strcmp("post-checkout", name) &&
+	     !strcmp(sha256, "791471b4ff472aab844a4fceaa48bbb0a12193616f971e8e940625498b4938a6")) ||
+	    (!strcmp("post-commit", name) &&
+	     !strcmp(sha256, "21e961572bb3f43a5f2fbafc1cc764d86046cc2e5f0bbecebfe9684a0b73b664")) ||
+	    (!strcmp("post-merge", name) &&
+	     !strcmp(sha256, "75da0da66a803b4b030ad50801ba57062c6196105eb1d2251590d100edb9390b")))
+		return 1;
+
 	if (!safe_hook_sha256s_initialized) {
 		safe_hook_sha256s_initialized = 1;
 		git_protected_config(safe_hook_cb, &safe_hook_sha256s);
diff --git a/t/t1800-hook.sh b/t/t1800-hook.sh
index 0f74c9154d0..af66999aff3 100755
--- a/t/t1800-hook.sh
+++ b/t/t1800-hook.sh
@@ -192,4 +192,24 @@ test_expect_success '`safe.hook.sha256` and clone protections' '
 	test "called hook" = "$(cat safe-hook/safe-hook.log)"
 '
 
+write_lfs_pre_push_hook () {
+	write_script "$1" <<-\EOF
+	command -v git-lfs >/dev/null 2>&1 || { echo >&2 "\nThis repository is configured for Git LFS but 'git-lfs' was not found on your path. If you no longer wish to use Git LFS, remove this hook by deleting the 'pre-push' file in the hooks directory (set by 'core.hookspath'; usually '.git/hooks').\n"; exit 2; }
+	git lfs pre-push "$@"
+	EOF
+}
+
+test_expect_success 'Git LFS special-handling in clone protections' '
+	git init lfs-hooks &&
+	write_lfs_pre_push_hook lfs-hooks/.git/hooks/pre-push &&
+	write_script git-lfs <<-\EOF &&
+	echo "called $*" >fake-git-lfs.log
+	EOF
+
+	PATH="$PWD:$PATH" GIT_CLONE_PROTECTION_ACTIVE=true \
+		git -C lfs-hooks hook run pre-push &&
+	test_write_lines "called pre-push" >expect &&
+	test_cmp lfs-hooks/fake-git-lfs.log expect
+'
+
 test_done
-- 
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