Subject: [PATCH 1/1] upload-pack.c: fix filter spec quoting bug

From: Jacob Vosmaer <[email-masked]>
Date: Fri, 22 Jan 2021 15:21:37 +0100

This fixes a bug that occurs when you combine partial clone and
uploadpack.packobjectshook. You can reproduce it as follows:

git clone -u 'git -c uploadpack.allowfilter '\
'-c uploadpack.packobjectshook=" exec" '\
'upload-pack' --filter=blob:none --no-local \
src.git dst.git

Be careful with the line endings because this has a long quoted string
as the -u argument. Note that there is an intentional space before
'exec'. Without that space, run-command.c tries to be smart and the
command fails for the wrong reason.

The error I get when I run this is:

Cloning into '/tmp/broken'...
remote: fatal: invalid filter-spec ''blob:none''
error: git upload-pack: git-pack-objects died with error.
fatal: git upload-pack: aborting due to possible repository corruption on the remote side.
remote: aborting due to possible repository corruption on the remote side.
fatal: early EOF
fatal: index-pack failed

The problem is an unnecessary and harmful layer of quoting. I tried
digging through the history of this function and I think this quoting
was there from the start. My best guess is that it stems from a
misunderstanding of what use_shell=1 means. The code seems to assume
it means "arguments get joined into one big string, then fed to
/bin/sh". But that is not what it means: use_shell=1 means that the
first argument in the arguments array may be a shell script and if so
should be passed to /bin/sh. All other arguments are passed as normal
arguments.

The solution is simple: never quote the filter spec.
---
 upload-pack.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/upload-pack.c b/upload-pack.c
index 3b66bf92ba..eae1fdbc55 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -305,14 +305,7 @@ static void create_pack_file(struct upload_pack_data *pack_data,
 	if (pack_data->filter_options.choice) {
 		const char *spec =
 			expand_list_objects_filter_spec(&pack_data->filter_options);
-		if (pack_objects.use_shell) {
-			struct strbuf buf = STRBUF_INIT;
-			sq_quote_buf(&buf, spec);
-			strvec_pushf(&pack_objects.args, "--filter=%s", buf.buf);
-			strbuf_release(&buf);
-		} else {
-			strvec_pushf(&pack_objects.args, "--filter=%s", spec);
-		}
+		strvec_pushf(&pack_objects.args, "--filter=%s", spec);
 	}
 	if (uri_protocols) {
 		for (i = 0; i < uri_protocols->nr; i++)
-- 
2.30.0