Do not end the whole androidqf run on an encrypted backup.ab (#891)

from_ab() raises InvalidAndroidBackup instead of exiting when it runs as a
sub-command, which check-androidqf catches to skip the backup modules. The
two password branches still called sys.exit(1) unconditionally, and since
run_backup_cmd() runs inside finish(), that ended the parent run before the
intrusion-logs command and before the timeline, alerts, urls, info and run
manifest were stored — leaving an output directory that looks complete but
has no alerts.json.

Also drop "as backup.ab is malformed" from the skip warning: it covers a
missing or wrong password too.

src/mvt/android/cmd_check_androidqf.py

@@ -292,9 +292,7 @@ class CmdAndroidCheckAndroidQF(Command):
         try:
             cmd.from_ab(backup)
         except InvalidAndroidBackup as exc:
-            self.log.warning(
-                "Skipping backup modules as backup.ab is malformed: %s", exc
-            )
+            self.log.warning("Skipping backup modules: %s", exc)
             return False
 
         cmd.run()

src/mvt/android/cmd_check_backup.py

@@ -87,11 +87,15 @@ class CmdAndroidCheckBackup(Command):
         if header["encryption"] != "none":
             password = prompt_or_load_android_backup_password(log, self.module_options)
             if not password:
+                if self.sub_command:
+                    raise InvalidAndroidBackup("No backup password provided")
                 log.critical("No backup password provided.")
                 sys.exit(1)
         try:
             tardata = parse_backup_file(ab_file_bytes, password=password)
         except InvalidBackupPassword:
+            if self.sub_command:
+                raise InvalidAndroidBackup("Invalid backup password")
             log.critical("Invalid backup password")
             sys.exit(1)
         except AndroidBackupParsingError as exc:

tests/android/test_check_backup_optional_failure.py

@@ -0,0 +1,39 @@
+# Mobile Verification Toolkit (MVT)
+# Copyright (c) 2021-2023 The MVT Authors.
+# Use of this software is governed by the MVT License 1.1 that can be found at
+#   https://license.mvt.re/1.1/
+"""An encrypted backup.ab must not take the whole check-androidqf run with it.
+
+`CmdAndroidCheckBackup.from_ab()` already raises `InvalidAndroidBackup` instead
+of exiting when it runs as a sub-command (`check-androidqf` catches that and
+skips the backup modules), for a wrong file format and for a parse error. The
+password branches used to call `sys.exit(1)` unconditionally, which ends the
+parent run inside `finish()` — before the intrusion-logs command and before the
+timeline, alerts, urls, info and run-manifest are written.
+"""
+
+import pytest
+
+from mvt.android.cmd_check_backup import CmdAndroidCheckBackup, InvalidAndroidBackup
+
+ENCRYPTED_AB_HEADER = b"ANDROID BACKUP\n5\n0\nAES-256\n" + b"\x00" * 64
+
+
+class TestCheckBackupOptionalFailure:
+    def _cmd(self, tmp_path, sub_command):
+        return CmdAndroidCheckBackup(
+            target_path=None,
+            results_path=str(tmp_path),
+            module_options={"interactive": False},
+            sub_command=sub_command,
+        )
+
+    def test_missing_password_raises_when_nested(self, tmp_path):
+        cmd = self._cmd(tmp_path, sub_command=True)
+        with pytest.raises(InvalidAndroidBackup):
+            cmd.from_ab(ENCRYPTED_AB_HEADER)
+
+    def test_missing_password_still_exits_on_its_own_command(self, tmp_path):
+        cmd = self._cmd(tmp_path, sub_command=False)
+        with pytest.raises(SystemExit):
+            cmd.from_ab(ENCRYPTED_AB_HEADER)

tests/test_check_android_androidqf.py

@@ -155,7 +155,7 @@ class TestCheckAndroidqfCommand:
             result = runner.invoke(check_androidqf, [str(path)])
 
         assert result.exit_code == 0
-        assert "Skipping backup modules as backup.ab is malformed" in caplog.text
+        assert "Skipping backup modules: Invalid backup format" in caplog.text
         assert not any(
             record.levelname in {"CRITICAL", "FATAL"} for record in caplog.records
         )