commit 5d844a1e3768d8c536169a754802b4bf8ebdd64c
from: Stefan Sperling <stsp@stsp.name>
date: Tue Aug 13 13:41:46 2019 UTC

don't attempt to parse Git's "leightweight" tags as real tag objects

commit - 34ca489849f1d73f5e1ac4a68208fbb0601901fb
commit + 5d844a1e3768d8c536169a754802b4bf8ebdd64c
blob - 2a63d8f1f0a6106de69dbfe0a9a3082b29b5c066
blob + 263bc2cb88607d7fc3ebf4d3c07422a39951de68
--- got/got.c
+++ got/got.c
@@ -1402,8 +1402,13 @@ print_commit(struct got_commit_object *commit, struct 
 			name += 8;
 		if (strncmp(name, "tags/", 5) == 0) {
 			err = got_object_open_as_tag(&tag, repo, re->id);
-			if (err)
-				return err;
+			if (err) {
+				if (err->code != GOT_ERR_OBJ_TYPE)
+					return err;
+				/* Ref points at something other than a tag. */
+				err = NULL;
+				tag = NULL;
+			}
 		}
 		cmp = got_object_id_cmp(tag ?
 		    got_object_tag_get_object_id(tag) : re->id, id);
blob - 63fbc857f6aca730ac30a8872e56c453ca7b60a3
blob + 79ee0f0c8347e32173b918ab6724d3456a467899
--- lib/object.c
+++ lib/object.c
@@ -1307,6 +1307,8 @@ open_tag(struct got_tag_object **tag, struct got_repos
 	struct got_packidx *packidx = NULL;
 	int idx;
 	char *path_packfile = NULL;
+	struct got_object *obj = NULL;
+	int obj_type = GOT_OBJ_TYPE_ANY;
 
 	if (check_cache) {
 		*tag = got_repo_get_cached_tag(repo, id);
@@ -1332,14 +1334,36 @@ open_tag(struct got_tag_object **tag, struct got_repos
 			if (err)
 				goto done;
 		}
-		err = read_packed_tag_privsep(tag, pack,
-		    packidx, idx, id);
+
+		/* Beware of "leightweight" tags: Check object type first. */
+		err = read_packed_object_privsep(&obj, repo, pack, packidx,
+		    idx, id);
+		if (err)
+			goto done;
+		obj_type = obj->type;
+		got_object_close(obj);
+		if (obj_type != GOT_OBJ_TYPE_TAG) {
+			err = got_error(GOT_ERR_OBJ_TYPE);
+			goto done;
+		}
+		err = read_packed_tag_privsep(tag, pack, packidx, idx, id);
 	} else if (err->code == GOT_ERR_NO_OBJ) {
 		int fd;
 
 		err = open_loose_object(&fd, id, repo);
 		if (err)
 			return err;
+		err = read_object_header_privsep(&obj, repo, fd);
+		if (err)
+			return err;
+		obj_type = obj->type;
+		got_object_close(obj);
+		if (obj_type != GOT_OBJ_TYPE_TAG)
+			return got_error(GOT_ERR_OBJ_TYPE);
+
+		err = open_loose_object(&fd, id, repo);
+		if (err)
+			return err;
 		err = read_tag_privsep(tag, fd, repo);
 	}
 
blob - 68b3bebcf73256d66fd1896739ae25c59583aa4d
blob + 330cb7270dac76c013148197dd78c6c658c5b281
--- tog/tog.c
+++ tog/tog.c
@@ -998,8 +998,13 @@ build_refs_str(char **refs_str, struct got_reflist_hea
 			name += 8;
 		if (strncmp(name, "tags/", 5) == 0) {
 			err = got_object_open_as_tag(&tag, repo, re->id);
-			if (err)
-				break;
+			if (err) {
+				if (err->code != GOT_ERR_OBJ_TYPE)
+					break;
+				/* Ref points at something other than a tag. */
+				err = NULL;
+				tag = NULL;
+			}
 		}
 		cmp = got_object_id_cmp(tag ?
 		    got_object_tag_get_object_id(tag) : re->id, id);