Merge bitcoin/bitcoin#28602: descriptors: Disallow hybrid and uncompressed keys when inferring

74c77825e5 test: Unit test for inferring scripts with hybrid and uncompressed keys (Andrew Chow)
f895f97014 test: Scripts with hybrid pubkeys are migrated to watchonly (Andrew Chow)
37b9b73477 descriptors: Move InferScript's pubkey validity checks to InferPubkey (Andrew Chow)
b7485f11ab descriptors: Check result of InferPubkey (Andrew Chow)

Pull request description:

  `InferDescriptor` was not always checking that the pubkey it was placing into the descriptor was an allowed pubkey. For example, given a P2WPKH script that uses an uncompressed pubkey, it would produce a `wpkh()` with the uncompressed key. Additionally, the hybrid key check was only being done for `pk()` scripts, where it should've been done for all scripts.

  This PR moves the key checking into `InferPubkey`. If the key is not valid for the context, then `nullptr` is returned and the inferring will fall through to the defaults of either `raw()` or `addr()`.

  This also resolves an issue with migrating legacy wallets that contain hybrid pubkeys as such watchonly scripts will become `raw()` or `addr()` and go to the watchonly wallet. Note that a legacy wallet cannot sign for hybrid pubkeys. A test has been added for the migration case.

  Also added unit tests for `InferDescriptor` itself as the edge cases with that function are not covered by the descriptor roundtrip test.

ACKs for top commit:
  furszy:
    ACK 74c77825
  Sjors:
    utACK 74c77825e5

Tree-SHA512: ed5f63e42a2e46120245a6b0288b90d2a6912860814c6c08fe393332add1cb364dc5eca72f16980352143570aef0c07bf1a91acd294099463bd028b6ce2fe40c

test/functional/wallet_migration.py

@@ -6,8 +6,13 @@
 
 import random
 import shutil
-from test_framework.address import script_to_p2sh
+from test_framework.address import (
+    script_to_p2sh,
+    key_to_p2pkh,
+    key_to_p2wpkh,
+)
 from test_framework.descriptors import descsum_create
+from test_framework.key import ECPubKey
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.messages import COIN, CTransaction, CTxOut
 from test_framework.script_util import key_to_p2pkh_script, script_to_p2sh_script, script_to_p2wsh_script
@@ -770,6 +775,58 @@ class WalletMigrationTest(BitcoinTestFramework):
 
         wallet.unloadwallet()
 
+    def test_hybrid_pubkey(self):
+        self.log.info("Test migration when wallet contains a hybrid pubkey")
+
+        wallet = self.create_legacy_wallet("hybrid_keys")
+
+        # Get the hybrid pubkey for one of the keys in the wallet
+        normal_pubkey = wallet.getaddressinfo(wallet.getnewaddress())["pubkey"]
+        first_byte = bytes.fromhex(normal_pubkey)[0] + 4 # Get the hybrid pubkey first byte
+        parsed_pubkey = ECPubKey()
+        parsed_pubkey.set(bytes.fromhex(normal_pubkey))
+        parsed_pubkey.compressed = False
+        hybrid_pubkey_bytes = bytearray(parsed_pubkey.get_bytes())
+        hybrid_pubkey_bytes[0] = first_byte # Make it hybrid
+        hybrid_pubkey = hybrid_pubkey_bytes.hex()
+
+        # Import the hybrid pubkey
+        wallet.importpubkey(hybrid_pubkey)
+        p2pkh_addr = key_to_p2pkh(hybrid_pubkey)
+        p2pkh_addr_info = wallet.getaddressinfo(p2pkh_addr)
+        assert_equal(p2pkh_addr_info["iswatchonly"], True)
+        assert_equal(p2pkh_addr_info["ismine"], False) # Things involving hybrid pubkeys are not spendable
+
+        # Also import the p2wpkh for the pubkey to make sure we don't migrate it
+        p2wpkh_addr = key_to_p2wpkh(hybrid_pubkey)
+        wallet.importaddress(p2wpkh_addr)
+
+        migrate_info = wallet.migratewallet()
+
+        # Both addresses should only appear in the watchonly wallet
+        p2pkh_addr_info = wallet.getaddressinfo(p2pkh_addr)
+        assert_equal(p2pkh_addr_info["iswatchonly"], False)
+        assert_equal(p2pkh_addr_info["ismine"], False)
+        p2wpkh_addr_info = wallet.getaddressinfo(p2wpkh_addr)
+        assert_equal(p2wpkh_addr_info["iswatchonly"], False)
+        assert_equal(p2wpkh_addr_info["ismine"], False)
+
+        watchonly_wallet = self.nodes[0].get_wallet_rpc(migrate_info["watchonly_name"])
+        watchonly_p2pkh_addr_info = watchonly_wallet.getaddressinfo(p2pkh_addr)
+        assert_equal(watchonly_p2pkh_addr_info["iswatchonly"], False)
+        assert_equal(watchonly_p2pkh_addr_info["ismine"], True)
+        watchonly_p2wpkh_addr_info = watchonly_wallet.getaddressinfo(p2wpkh_addr)
+        assert_equal(watchonly_p2wpkh_addr_info["iswatchonly"], False)
+        assert_equal(watchonly_p2wpkh_addr_info["ismine"], True)
+
+        # There should only be raw or addr descriptors
+        for desc in watchonly_wallet.listdescriptors()["descriptors"]:
+            if desc["desc"].startswith("raw(") or desc["desc"].startswith("addr("):
+                continue
+            assert False, "Hybrid pubkey watchonly wallet has more than just raw() and addr()"
+
+        wallet.unloadwallet()
+
     def run_test(self):
         self.generate(self.nodes[0], 101)
 
@@ -787,6 +844,7 @@ class WalletMigrationTest(BitcoinTestFramework):
         self.test_addressbook()
         self.test_migrate_raw_p2sh()
         self.test_conflict_txs()
+        self.test_hybrid_pubkey()
 
 if __name__ == '__main__':
     WalletMigrationTest().main()