Ensure directory permissions are correctly applied. (#372)

* Add link ownership rules.

* Reorder directories when creating.

src/archive.rs

@@ -238,6 +238,15 @@ impl Archive<dyn Read + '_> {
                 file.unpack_in(dst)?;
             }
         }
+
+        // Apply the directories.
+        //
+        // Note: the order of application is important to permissions. That is, we must traverse
+        // the filesystem graph in topological ordering or else we risk not being able to create
+        // child directories within those of more restrictive permissions. See [0] for details.
+        //
+        // [0]: <https://github.com/alexcrichton/tar-rs/issues/242>
+        directories.sort_by(|a, b| b.path_bytes().cmp(&a.path_bytes()));
         for mut dir in directories {
             dir.unpack_in(dst)?;
         }

tests/all.rs

@@ -420,6 +420,43 @@ fn writing_and_extracting_directories() {
     check_dirtree(&td);
 }
 
+#[test]
+fn writing_and_extracting_directories_complex_permissions() {
+    let td = t!(TempBuilder::new().prefix("tar-rs").tempdir());
+
+    // Archive with complex permissions which would fail to unpack if one attempted to do so
+    // without reordering of entries.
+    let mut ar = Builder::new(Vec::new());
+    let tmppath = td.path().join("tmpfile");
+    t!(t!(File::create(&tmppath)).write_all(b"c"));
+
+    // Root dir with very stringent permissions
+    let data: &[u8] = &[];
+    let mut header = Header::new_gnu();
+    header.set_mode(0o555);
+    header.set_entry_type(EntryType::Directory);
+    t!(header.set_path("a"));
+    header.set_size(0);
+    header.set_cksum();
+    t!(ar.append(&header, data));
+
+    // Nested dir
+    header.set_mode(0o777);
+    header.set_entry_type(EntryType::Directory);
+    t!(header.set_path("a/b"));
+    header.set_cksum();
+    t!(ar.append(&header, data));
+
+    // Nested file.
+    t!(ar.append_file("a/c", &mut t!(File::open(&tmppath))));
+    t!(ar.finish());
+
+    let rdr = Cursor::new(t!(ar.into_inner()));
+    let mut ar = Archive::new(rdr);
+    ar.unpack(td.path()).unwrap();
+    check_dirtree(&td);
+}
+
 #[test]
 fn writing_directories_recursively() {
     let td = t!(TempBuilder::new().prefix("tar-rs").tempdir());