[RFC PATCH] list-objects-filter: disable 'sparse:path' filters

[Christian Couder <christian.couder@gmail.com>]

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.
---
 list-objects-filter-options.c |  9 ++++++---
 list-objects-filter-options.h |  2 --
 list-objects-filter.c         | 22 ----------------------
 3 files changed, 6 insertions(+), 27 deletions(-)

diff --git a/list-objects-filter-options.c b/list-objects-filter-options.c
index c0036f7378..007c104b93 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 are now disabled"));
+		}
+		return 1;
 	}
 	/*
 	 * Please update _git_fetch() in git-completion.bash when you
diff --git a/list-objects-filter-options.h b/list-objects-filter-options.h
index e3adc78ebf..c54f0000fb 100644
--- a/list-objects-filter-options.h
+++ b/list-objects-filter-options.h
@@ -13,7 +13,6 @@ enum list_objects_filter_choice {
 	LOFC_BLOB_LIMIT,
 	LOFC_TREE_DEPTH,
 	LOFC_SPARSE_OID,
-	LOFC_SPARSE_PATH,
 	LOFC__COUNT /* must be last */
 };
 
@@ -44,7 +43,6 @@ struct list_objects_filter_options {
 	 * choice.
 	 */
 	struct object_id *sparse_oid_value;
-	char *sparse_path_value;
 	unsigned long blob_limit_value;
 	unsigned long tree_exclude_depth;
 };
diff --git a/list-objects-filter.c b/list-objects-filter.c
index ee449de3f7..53f90442c5 100644
--- a/list-objects-filter.c
+++ b/list-objects-filter.c
@@ -478,27 +478,6 @@ static void *filter_sparse_oid__init(
 	return d;
 }
 
-static void *filter_sparse_path__init(
-	struct oidset *omitted,
-	struct list_objects_filter_options *filter_options,
-	filter_object_fn *filter_fn,
-	filter_free_fn *filter_free_fn)
-{
-	struct filter_sparse_data *d = xcalloc(1, sizeof(*d));
-	d->omits = omitted;
-	if (add_excludes_from_file_to_list(filter_options->sparse_path_value,
-					   NULL, 0, &d->el, NULL) < 0)
-		die("could not load filter specification");
-
-	ALLOC_GROW(d->array_frame, d->nr + 1, d->alloc);
-	d->array_frame[d->nr].defval = 0; /* default to include */
-	d->array_frame[d->nr].child_prov_omit = 0;
-
-	*filter_fn = filter_sparse;
-	*filter_free_fn = filter_sparse_free;
-	return d;
-}
-
 typedef void *(*filter_init_fn)(
 	struct oidset *omitted,
 	struct list_objects_filter_options *filter_options,
@@ -514,7 +493,6 @@ static filter_init_fn s_filters[] = {
 	filter_blobs_limit__init,
 	filter_trees_depth__init,
 	filter_sparse_oid__init,
-	filter_sparse_path__init,
 };
 
 void *list_objects_filter__init(
-- 
2.22.0.rc1