lnutil: test ImportedChannelBackupStorage.from_bytes

regression test - we should not inadvertently break deserialising existing backups

electrum/lnutil.py

@@ -16,7 +16,7 @@ from .util import list_enabled_bits
 from .util import ShortID as ShortChannelID
 from .util import format_short_id as format_short_channel_id
 
-from .crypto import sha256
+from .crypto import sha256, pw_decode_with_version_and_mac
 from .transaction import (Transaction, PartialTransaction, PartialTxInput, TxOutpoint,
                           PartialTxOutput, opcodes, TxOutput)
 from .ecc import CURVE_ORDER, sig_string_from_der_sig, ECPubkey, string_to_number
@@ -281,7 +281,7 @@ class ImportedChannelBackupStorage(ChannelBackupStorage):
         return bytes(vds.input)
 
     @staticmethod
-    def from_bytes(s):
+    def from_bytes(s: bytes) -> "ImportedChannelBackupStorage":
         vds = BCDataStream()
         vds.write(s)
         version = vds.read_int16()
@@ -302,6 +302,13 @@ class ImportedChannelBackupStorage(ChannelBackupStorage):
             host = vds.read_string(),
             port = vds.read_int16())
 
+    @staticmethod
+    def from_encrypted_str(data: str, *, password: str) -> "ImportedChannelBackupStorage":
+        if not data.startswith('channel_backup:'):
+            raise ValueError("missing or invalid magic bytes")
+        encrypted = data[15:]
+        decrypted = pw_decode_with_version_and_mac(encrypted, password)
+        return ImportedChannelBackupStorage.from_bytes(decrypted)
 
 
 class ScriptHtlc(NamedTuple):

electrum/lnworker.py

@@ -2452,11 +2452,8 @@ class LNWallet(LNWorker):
             raise Exception(f'Unknown channel {channel_id.hex()}')
 
     def import_channel_backup(self, data):
-        assert data.startswith('channel_backup:')
-        encrypted = data[15:]
         xpub = self.wallet.get_fingerprint()
-        decrypted = pw_decode_with_version_and_mac(encrypted, xpub)
-        cb_storage = ImportedChannelBackupStorage.from_bytes(decrypted)
+        cb_storage = ImportedChannelBackupStorage.from_encrypted_str(data, password=xpub)
         channel_id = cb_storage.channel_id()
         if channel_id.hex() in self.db.get_dict("channels"):
             raise Exception('Channel already in wallet')

electrum/tests/test_lnutil.py

@@ -9,12 +9,15 @@ from electrum.lnutil import (RevocationStore, get_per_commitment_secret_from_see
                              derive_pubkey, make_htlc_tx, extract_ctn_from_tx, UnableToDeriveSecret,
                              get_compressed_pubkey_from_bech32, split_host_port, ConnStringFormatError,
                              ScriptHtlc, extract_nodeid, calc_fees_for_commitment_tx, UpdateAddHtlc, LnFeatures,
-                             ln_compare_features, IncompatibleLightningFeatures, ChannelType)
+                             ln_compare_features, IncompatibleLightningFeatures, ChannelType,
+                             ImportedChannelBackupStorage)
 from electrum.util import bfh, MyEncoder
 from electrum.transaction import Transaction, PartialTransaction, Sighash
 from electrum.lnworker import LNWallet
+from electrum.wallet import restore_wallet_from_text, Standard_Wallet
+from electrum.simple_config import SimpleConfig
 
-from . import ElectrumTestCase
+from . import ElectrumTestCase, as_testnet
 
 
 funding_tx_id = '8984484a580b825b9972d7adb15050b3ab624ccd731946b3eeddb92f4e7ef6be'
@@ -903,3 +906,29 @@ class TestLNUtil(ElectrumTestCase):
         # ignore unknown channel types
         channel_type = ChannelType(0b10000000001000000000010).discard_unknown_and_check()
         self.assertEqual(ChannelType(0b10000000001000000000000), channel_type)
+
+    @as_testnet
+    async def test_decode_imported_channel_backup(self):
+        encrypted_cb = "channel_backup:Adn87xcGIs9H2kfp4VpsOaNKWCHX08wBoqq37l1cLYKGlJamTeoaLEwpJA81l1BXF3GP/mRxqkY+whZG9l51G8izIY/kmMSvnh0DOiZEdwaaT/1/MwEHfsEomruFqs+iW24SFJPHbMM7f80bDtIxcLfZkKmgcKBAOlcqtq+dL3U3yH74S8BDDe2L4snaxxpCjF0JjDMBx1UR/28D+QlIi+lbvv1JMaCGXf+AF1+3jLQf8+lVI+rvFdyArws6Ocsvjf+ANQeSGUwW6Nb2xICQcMRgr1DO7bO4pgGu408eYRr2v3ayJBVtnKwSwd49gF5SDSjTDAO4CCM0uj9H5RxyzH7fqotkd9J80MBr84RiBXAeXKz+Ap8608/FVqgQ9BOcn6LhuAQdE5zXpmbQyw5jUGkPvHuseR+rzthzncy01odUceqTNg=="
+        config = SimpleConfig({'electrum_path': self.electrum_path})
+        d = restore_wallet_from_text("9dk", path=None, gap_limit=2, config=config)
+        wallet1 = d['wallet']  # type: Standard_Wallet
+        decoded_cb = ImportedChannelBackupStorage.from_encrypted_str(encrypted_cb, password=wallet1.get_fingerprint())
+        self.assertEqual(
+            ImportedChannelBackupStorage(
+                funding_txid='97767fdefef3152319363b772914d71e5eb70e793b835c13dce20037d3ac13fe',
+                funding_index=1,
+                funding_address='tb1qfsxllwl2edccpar9jas9wsxd4vhcewlxqwmn0w27kurkme3jvkdqn4msdp',
+                is_initiator=True,
+                node_id=bfh('02bf82e22f99dcd7ac1de4aad5152ce48f0694c46ec582567f379e0adbf81e2d0f'),
+                privkey=bfh('7e634853dc47f0bc2f2e0d1054b302fcb414371ddbd889f29ba8aa4e8b62c772'),
+                host='lightning.electrum.org',
+                port=9739,
+                channel_seed=bfh('ce9bad44ff8521d9f57fd202ad7cdedceb934f0056f42d0f3aa7a576b505332a'),
+                local_delay=1008,
+                remote_delay=720,
+                remote_payment_pubkey=bfh('02a1bbc818e2e88847016a93c223eb4adef7bb8becb3709c75c556b6beb3afe7bd'),
+                remote_revocation_pubkey=bfh('022f28b7d8d1f05768ada3df1b0966083b8058e1e7197c57393e302ec118d7f0ae'),
+            ),
+            decoded_cb,
+        )