sigil/tests/test_sealed.py

"""Sealed store: encryption at rest for the Sigil database file.

Finding: digests stop a stolen DB from yielding live credentials, but the file
still holds the agent roster, revocation state and audit history in the clear.
SealedStore wraps on-disk bytes in AES-256-GCM so that material is unreadable
without the passphrase. Short of SQLCipher (no page-level encryption while
open); real working seal of the sensitive file.
"""

from __future__ import annotations

import os
import sqlite3
import tempfile
import unittest

from sigil import identity, keys
from sigil.sealed import (
    MAGIC,
    SealedStore,
    is_sealed_file,
    seal_bytes,
    unseal_bytes,
)
from sigil.store import Store
from tests import helpers


PASS = "test-seal-passphrase-ok"


class TestSealBytes(unittest.TestCase):
    def test_round_trip(self):
        blob = seal_bytes(b"SQLite format 3\x00hello", PASS)
        self.assertTrue(blob.startswith(MAGIC))
        self.assertEqual(unseal_bytes(blob, PASS), b"SQLite format 3\x00hello")

    def test_wrong_passphrase_refused(self):
        blob = seal_bytes(b"secret-db-bytes", PASS)
        with self.assertRaises(ValueError):
            unseal_bytes(blob, "wrong-passphrase!!")

    def test_short_passphrase_refused(self):
        with self.assertRaises(ValueError):
            seal_bytes(b"x", "short")

    def test_corrupt_magic_refused(self):
        with self.assertRaises(ValueError):
            unseal_bytes(b"NOTSEALED" + b"\x00" * 40, PASS)


class TestSealedStore(unittest.TestCase):
    def setUp(self):
        self.tmp = tempfile.TemporaryDirectory()
        self.addCleanup(self.tmp.cleanup)
        self.path = os.path.join(self.tmp.name, "sigil.seal")

    def test_flush_writes_ciphertext_without_sqlite_header(self):
        store = SealedStore(self.path, PASS)
        helpers.enrol(store, "bigpickle")
        store.flush()
        with open(self.path, "rb") as handle:
            raw = handle.read()
        self.assertTrue(raw.startswith(MAGIC))
        self.assertNotIn(b"SQLite format 3", raw)
        self.assertTrue(is_sealed_file(self.path))
        # Agent id must not appear in the clear on disk.
        self.assertNotIn(b"bigpickle", raw)
        store.close()

    def test_reopen_with_passphrase_recovers_agents(self):
        with SealedStore(self.path, PASS) as store:
            private, _ = helpers.enrol(store, "bigpickle")
            store.flush()
        with SealedStore(self.path, PASS) as store:
            row = store.get_agent("bigpickle")
            self.assertIsNotNone(row)
            self.assertEqual(row["fingerprint"], keys.fingerprint(
                keys.public_from_private(private)
            ))

    def test_reopen_with_wrong_passphrase_fails(self):
        with SealedStore(self.path, PASS) as store:
            helpers.enrol(store, "bigpickle")
            store.flush()
        with self.assertRaises(ValueError):
            SealedStore(self.path, "definitely-wrong-passphrase")

    def test_stolen_seal_is_not_a_sqlite_database(self):
        with SealedStore(self.path, PASS) as store:
            helpers.enrol(store, "bigpickle")
            identity.challenge(store, "bigpickle")
            store.flush()
        with self.assertRaises(sqlite3.DatabaseError):
            sqlite3.connect(self.path).execute("SELECT name FROM sqlite_master")

    def test_refuses_to_open_cleartext_db_as_sealed(self):
        clear = os.path.join(self.tmp.name, "clear.db")
        Store(clear)  # creates a normal sqlite file
        with self.assertRaises(ValueError) as ctx:
            SealedStore(clear, PASS)
        self.assertIn("not a Sigil sealed store", str(ctx.exception))

    def test_seal_permissions_are_owner_only(self):
        with SealedStore(self.path, PASS) as store:
            helpers.enrol(store, "bigpickle")
            store.flush()
        mode = os.stat(self.path).st_mode & 0o777
        self.assertEqual(mode, 0o600)

    def test_sealed_store_works_with_offbox_anchor(self):
        tip = os.path.join(self.tmp.name, "chain.tip")
        with SealedStore(self.path, PASS, anchor_path=tip) as store:
            private, _ = helpers.enrol(store, "bigpickle")
            identity.challenge(store, "bigpickle")
            result = store.checkpoint(private, "bigpickle", "sealed-daily")
            self.assertEqual(result.get("anchor_path"), tip)
            self.assertTrue(os.path.exists(tip))
            self.assertTrue(store.verify_external_anchors()["ok"])
            store.flush()
        self.assertTrue(is_sealed_file(self.path))
        self.assertTrue(os.path.exists(tip))


if __name__ == "__main__":
    unittest.main()


class TestPlaintextWorkingCopyHardening(unittest.TestCase):
    """R5: plaintext tmp must be 0600; SQLCipher remains deferred."""

    def test_plaintext_working_copy_is_owner_only(self):
        import tempfile
        from sigil.sealed import SealedStore
        from sigil import identity, keys

        d = tempfile.mkdtemp()
        path = os.path.join(d, "sealed.db")
        store = SealedStore(path, "test-passphrase-ok")
        try:
            mode = os.stat(store._plain_path).st_mode & 0o777
            self.assertEqual(mode, 0o600, oct(mode))
            dir_mode = os.stat(store._tmpdir.name).st_mode & 0o777
            self.assertEqual(dir_mode, 0o700, oct(dir_mode))
            secret = identity.seed_bootstrap(store, "alice")
            _, pub = keys.generate()
            identity.enrol(store, "alice", keys.export_public_b64(pub), secret)
            store.flush()
            # export.db must not linger world-readable after flush
            export = os.path.join(store._tmpdir.name, "export.db")
            self.assertFalse(os.path.exists(export))
        finally:
            store.close()