Fix crash in unix users plugins if GID or UID is empty

dissect/target/plugins/os/unix/_os.py

@@ -75,7 +75,7 @@ def users(self, sessions: bool = False) -> Iterator[UnixUserRecord]:
         # Yield users found in passwd files.
         for passwd_file in PASSWD_FILES:
             if (path := self.target.fs.path(passwd_file)).exists():
-                for line in path.open("rt"):
+                for line in path.open("rt", errors="backslashreplace"):
                     line = line.strip()
                     if not line or line.startswith("#"):
                         continue
@@ -85,13 +85,12 @@ def users(self, sessions: bool = False) -> Iterator[UnixUserRecord]:
                     current_user = (pwent.get(0), pwent.get(5), pwent.get(6))
                     if current_user in seen_users:
                         continue
-
                     seen_users.add(current_user)
                     yield UnixUserRecord(
                         name=pwent.get(0),
                         passwd=pwent.get(1),
-                        uid=pwent.get(2),
-                        gid=pwent.get(3),
+                        uid=pwent.get(2) if pwent.get(2) != "" else None,
+                        gid=pwent.get(3) if pwent.get(3) != "" else None,
                         gecos=pwent.get(4),
                         home=posix_path(pwent.get(5)),
                         shell=pwent.get(6),

tests/conftest.py

@@ -441,6 +441,7 @@ def target_unix_users(target_unix: Target, fs_unix: Filesystem) -> Iterator[Targ
     passwd = """
     root:x:0:0:root:/root:/bin/bash
     user:x:1000:1000:user:/home/user:/bin/bash
+    +@ngtest:x:::::
     """
     fs_unix.map_file_fh("/etc/passwd", BytesIO(textwrap.dedent(passwd).encode()))
     yield target_unix

tests/plugins/os/unix/test__os.py

@@ -134,7 +134,7 @@ def test_parse_hostname_string(
 def test_users(target_unix_users: Target) -> None:
     users = list(target_unix_users.users())
 
-    assert len(users) == 2
+    assert len(users) == 3
 
     assert users[0].name == "root"
     assert users[0].uid == 0