list-objects-filter: disable 'sparse:path' filters

If someone wants to use as a filter a sparse file that is in the
repository, something like "--filter=sparse:oid=<ref>:<path>"
already works.

So 'sparse:path' is only interesting if the sparse file is not in
the repository. In this case though the current implementation has
a big security issue, as it makes it possible to ask the server to
read any file, like for example /etc/password, and to explore the
filesystem, as well as individual lines of files.

If someone is interested in using a sparse file that is not in the
repository as a filter, then at the minimum a config option, such
as "uploadpack.sparsePathFilter", should be implemented first to
restrict the directory from which the files specified by
'sparse:path' can be read.

For now though, let's just disable 'sparse:path' filters.

Helped-by: Matthew DeVore <matvore@google.com>
Helped-by: Jeff Hostetler <git@jeffhostetler.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c
index c0036f7378..a15d0f7829 100644
--- a/list-objects-filter-options.c
+++ b/list-objects-filter-options.c
@@ -78,9 +78,12 @@ static int gently_parse_list_objects_filter(
 		return 0;
 
 	} else if (skip_prefix(arg, "sparse:path=", &v0)) {
-		filter_options->choice = LOFC_SPARSE_PATH;
-		filter_options->sparse_path_value = strdup(v0);
-		return 0;
+		if (errbuf) {
+			strbuf_addstr(
+				errbuf,
+				_("sparse:path filters support has been dropped"));
+		}
+		return 1;
 	}
 	/*
 	 * Please update _git_fetch() in git-completion.bash when you
@@ -136,7 +139,6 @@ void list_objects_filter_release(
 {
 	free(filter_options->filter_spec);
 	free(filter_options->sparse_oid_value);
-	free(filter_options->sparse_path_value);
 	memset(filter_options, 0, sizeof(*filter_options));
 }