submodule: ignore submodules which include path traversal in their name

If the we decide that the "name" of the submodule (i.e. its path inside
`.git/modules/`) is trying to escape that directory or otherwise trick us, we
ignore the configuration for that submodule.

This leaves us with a half-configured submodule when looking it up by path, but
it's the same result as if the configuration really were missing.

The name check is potentially more strict than it needs to be, but it lets us
re-use the check we're doing for the checkout. The function that encapsulates
this logic is ready to be exported but we don't want to do that in a security
release so it remains internal for now.

1 files changed, 17 insertions, 12 deletions

diff --git a/tests/submodule/escape.c b/tests/submodule/escape.c
index 18d238f24..576d7884b 100644
--- a/tests/submodule/escape.c
+++ b/tests/submodule/escape.c
@@ -32,29 +32,34 @@ void test_submodule_escape__from_gitdir(void)
 	git_config *cfg;
 	git_submodule *sm;
 	git_buf buf = GIT_BUF_INIT;
+	unsigned int sm_location;
 
 	g_repo = setup_fixture_submodule_simple();
 
 	cl_git_pass(git_buf_joinpath(&buf, git_repository_workdir(g_repo), ".gitmodules"));
-	cl_git_pass(git_config_open_ondisk(&cfg, git_buf_cstr(&buf)));
-
-	/* We don't have a function to rename a subsection so we do it manually */
-	cl_git_pass(git_submodule_lookup(&sm, g_repo, "testrepo"));
-	cl_git_pass(git_config_set_string(cfg, "submodule." EVIL_SM_NAME ".path", git_submodule_path(sm)));
-	cl_git_pass(git_config_set_string(cfg, "submodule." EVIL_SM_NAME ".url", git_submodule_url(sm)));
-	cl_git_pass(git_config_delete_entry(cfg, "submodule.testrepo.path"));
-	cl_git_pass(git_config_delete_entry(cfg, "submodule.testrepo.url"));
-	git_config_free(cfg);
+	cl_git_rewritefile(buf.ptr,
+			   "[submodule \"" EVIL_SM_NAME "\"]\n"
+			   "    path = testrepo\n"
+			   "    url = ../testrepo.git\n");
 
 	/* We also need to update the value in the config */
 	cl_git_pass(git_repository_config__weakptr(&cfg, g_repo));
-	cl_git_pass(git_config_set_string(cfg, "submodule." EVIL_SM_NAME ".url", git_submodule_url(sm)));
 	cfg = NULL;
 
 	/* Find it all the different ways we know about it */
-	cl_git_fail_with(GIT_ENOTFOUND, git_submodule_lookup(&sm, g_repo, EVIL_SM_NAME));
-	cl_git_fail_with(GIT_ENOTFOUND, git_submodule_lookup(&sm, g_repo, "testrepo"));
 	foundit = 0;
 	cl_git_pass(git_submodule_foreach(g_repo, find_evil, &foundit));
 	cl_assert_equal_i(0, foundit);
+	cl_git_fail_with(GIT_ENOTFOUND, git_submodule_lookup(&sm, g_repo, EVIL_SM_NAME));
+	/*
+	 * We do know about this as it's in the index and HEAD, but the data is
+	 * incomplete as there is no configured data for it (we pretend it
+	 * doesn't exist). This leaves us with an odd situation but it's
+	 * consistent with what we would do if we did add a submodule with no
+	 * configuration.
+	 */
+	cl_git_pass(git_submodule_lookup(&sm, g_repo, "testrepo"));
+	cl_git_pass(git_submodule_location(&sm_location, sm));
+	cl_assert_equal_i(GIT_SUBMODULE_STATUS_IN_INDEX | GIT_SUBMODULE_STATUS_IN_HEAD, sm_location);
+	git_submodule_free(sm);
 }