Descriptor checksum

3 files changed, 73 insertions, 9 deletions

diff --git a/test/functional/rpc_scantxoutset.py b/test/functional/rpc_scantxoutset.py
index 11b4db6ec5..29074c6af3 100755
--- a/test/functional/rpc_scantxoutset.py
+++ b/test/functional/rpc_scantxoutset.py
@@ -97,9 +97,9 @@ class ScantxoutsetTest(BitcoinTestFramework):
         assert_equal(self.nodes[0].scantxoutset("start", [ {"desc": "combo(tpubD6NzVbkrYhZ4WaWSyoBvQwbpLkojyoTZPRsgXELWz3Popb3qkjcJyJUGLnL4qHHoQvao8ESaAstxYSnhyswJ76uZPStJRJCTKvosUCJZL5B/1/1/*)", "range": 1500}])['total_amount'], Decimal("28.672"))
 
         # Test the reported descriptors for a few matches
-        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ {"desc": "combo(tprv8ZgxMBicQKsPd7Uf69XL1XwhmjHopUGep8GuEiJDZmbQz6o58LninorQAfcKZWARbtRtfnLcJ5MQ2AtHcQJCCRUcMRvmDUjyEmNUWwx8UbK/0h/0'/*)", "range": 1499}])), ["pkh([0c5f9a1e/0'/0'/0]026dbd8b2315f296d36e6b6920b1579ca75569464875c7ebe869b536a7d9503c8c)", "pkh([0c5f9a1e/0'/0'/1]033e6f25d76c00bedb3a8993c7d5739ee806397f0529b1b31dda31ef890f19a60c)"])
-        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ "combo(tprv8ZgxMBicQKsPd7Uf69XL1XwhmjHopUGep8GuEiJDZmbQz6o58LninorQAfcKZWARbtRtfnLcJ5MQ2AtHcQJCCRUcMRvmDUjyEmNUWwx8UbK/1/1/0)"])), ["pkh([0c5f9a1e/1/1/0]03e1c5b6e650966971d7e71ef2674f80222752740fc1dfd63bbbd220d2da9bd0fb)"])
-        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ {"desc": "combo(tpubD6NzVbkrYhZ4WaWSyoBvQwbpLkojyoTZPRsgXELWz3Popb3qkjcJyJUGLnL4qHHoQvao8ESaAstxYSnhyswJ76uZPStJRJCTKvosUCJZL5B/1/1/*)", "range": 1500}])), ['pkh([0c5f9a1e/1/1/0]03e1c5b6e650966971d7e71ef2674f80222752740fc1dfd63bbbd220d2da9bd0fb)', 'pkh([0c5f9a1e/1/1/1500]03832901c250025da2aebae2bfb38d5c703a57ab66ad477f9c578bfbcd78abca6f)', 'pkh([0c5f9a1e/1/1/1]030d820fc9e8211c4169be8530efbc632775d8286167afd178caaf1089b77daba7)'])
+        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ {"desc": "combo(tprv8ZgxMBicQKsPd7Uf69XL1XwhmjHopUGep8GuEiJDZmbQz6o58LninorQAfcKZWARbtRtfnLcJ5MQ2AtHcQJCCRUcMRvmDUjyEmNUWwx8UbK/0h/0'/*)", "range": 1499}])), ["pkh([0c5f9a1e/0'/0'/0]026dbd8b2315f296d36e6b6920b1579ca75569464875c7ebe869b536a7d9503c8c)#dzxw429x", "pkh([0c5f9a1e/0'/0'/1]033e6f25d76c00bedb3a8993c7d5739ee806397f0529b1b31dda31ef890f19a60c)#43rvceed"])
+        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ "combo(tprv8ZgxMBicQKsPd7Uf69XL1XwhmjHopUGep8GuEiJDZmbQz6o58LninorQAfcKZWARbtRtfnLcJ5MQ2AtHcQJCCRUcMRvmDUjyEmNUWwx8UbK/1/1/0)"])), ["pkh([0c5f9a1e/1/1/0]03e1c5b6e650966971d7e71ef2674f80222752740fc1dfd63bbbd220d2da9bd0fb)#cxmct4w8"])
+        assert_equal(descriptors(self.nodes[0].scantxoutset("start", [ {"desc": "combo(tpubD6NzVbkrYhZ4WaWSyoBvQwbpLkojyoTZPRsgXELWz3Popb3qkjcJyJUGLnL4qHHoQvao8ESaAstxYSnhyswJ76uZPStJRJCTKvosUCJZL5B/1/1/*)", "range": 1500}])), ['pkh([0c5f9a1e/1/1/0]03e1c5b6e650966971d7e71ef2674f80222752740fc1dfd63bbbd220d2da9bd0fb)#cxmct4w8', 'pkh([0c5f9a1e/1/1/1500]03832901c250025da2aebae2bfb38d5c703a57ab66ad477f9c578bfbcd78abca6f)#vchwd07g', 'pkh([0c5f9a1e/1/1/1]030d820fc9e8211c4169be8530efbc632775d8286167afd178caaf1089b77daba7)#z2t3ypsa'])
 
 if __name__ == '__main__':
     ScantxoutsetTest().main()
diff --git a/test/functional/test_framework/descriptors.py b/test/functional/test_framework/descriptors.py
new file mode 100644
index 0000000000..29482ce01e
--- /dev/null
+++ b/test/functional/test_framework/descriptors.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+# Copyright (c) 2019 Pieter Wuille
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Utility functions related to output descriptors"""
+
+INPUT_CHARSET = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ "
+CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+GENERATOR = [0xf5dee51989, 0xa9fdca3312, 0x1bab10e32d, 0x3706b1677a, 0x644d626ffd]
+
+def descsum_polymod(symbols):
+    """Internal function that computes the descriptor checksum."""
+    chk = 1
+    for value in symbols:
+        top = chk >> 35
+        chk = (chk & 0x7ffffffff) << 5 ^ value
+        for i in range(5):
+            chk ^= GENERATOR[i] if ((top >> i) & 1) else 0
+    return chk
+
+def descsum_expand(s):
+    """Internal function that does the character to symbol expansion"""
+    groups = []
+    symbols = []
+    for c in s:
+        if not c in INPUT_CHARSET:
+            return None
+        v = INPUT_CHARSET.find(c)
+        symbols.append(v & 31)
+        groups.append(v >> 5)
+        if len(groups) == 3:
+            symbols.append(groups[0] * 9 + groups[1] * 3 + groups[2])
+            groups = []
+    if len(groups) == 1:
+        symbols.append(groups[0])
+    elif len(groups) == 2:
+        symbols.append(groups[0] * 3 + groups[1])
+    return symbols
+
+def descsum_create(s):
+    """Add a checksum to a descriptor without"""
+    symbols = descsum_expand(s) + [0, 0, 0, 0, 0, 0, 0, 0]
+    checksum = descsum_polymod(symbols) ^ 1
+    return s + '#' + ''.join(CHECKSUM_CHARSET[(checksum >> (5 * (7 - i))) & 31] for i in range(8))
+
+def descsum_check(s, require=True):
+    """Verify that the checksum is correct in a descriptor"""
+    if not '#' in s:
+        return not require
+    if s[-9] != '#':
+        return False
+    if not all(x in CHECKSUM_CHARSET for x in s[-8:]):
+        return False
+    symbols = descsum_expand(s[:-9]) + [CHECKSUM_CHARSET.find(x) for x in s[-8:]]
+    return descsum_polymod(symbols) == 1
diff --git a/test/functional/wallet_address_types.py b/test/functional/wallet_address_types.py
index bafa556aad..027229111e 100755
--- a/test/functional/wallet_address_types.py
+++ b/test/functional/wallet_address_types.py
@@ -54,6 +54,10 @@ from decimal import Decimal
 import itertools
 
 from test_framework.test_framework import BitcoinTestFramework
+from test_framework.descriptors import (
+    descsum_create,
+    descsum_check,
+)
 from test_framework.util import (
     assert_equal,
     assert_greater_than,
@@ -167,24 +171,29 @@ class AddressTypeTest(BitcoinTestFramework):
             assert_equal(deriv['path'][0], 'm')
             key_descs[deriv['pubkey']] = '[' + deriv['master_fingerprint'] + deriv['path'][1:] + ']' + deriv['pubkey']
 
+        # Verify the descriptor checksum against the Python implementation
+        assert(descsum_check(info['desc']))
+        # Verify that stripping the checksum and recreating it using Python roundtrips
+        assert(info['desc'] == descsum_create(info['desc'][:-9]))
+
         if not multisig and typ == 'legacy':
             # P2PKH
-            assert_equal(info['desc'], "pkh(%s)" % key_descs[info['pubkey']])
+            assert_equal(info['desc'], descsum_create("pkh(%s)" % key_descs[info['pubkey']]))
         elif not multisig and typ == 'p2sh-segwit':
             # P2SH-P2WPKH
-            assert_equal(info['desc'], "sh(wpkh(%s))" % key_descs[info['pubkey']])
+            assert_equal(info['desc'], descsum_create("sh(wpkh(%s))" % key_descs[info['pubkey']]))
         elif not multisig and typ == 'bech32':
             # P2WPKH
-            assert_equal(info['desc'], "wpkh(%s)" % key_descs[info['pubkey']])
+            assert_equal(info['desc'], descsum_create("wpkh(%s)" % key_descs[info['pubkey']]))
         elif typ == 'legacy':
             # P2SH-multisig
-            assert_equal(info['desc'], "sh(multi(2,%s,%s))" % (key_descs[info['pubkeys'][0]], key_descs[info['pubkeys'][1]]))
+            assert_equal(info['desc'], descsum_create("sh(multi(2,%s,%s))" % (key_descs[info['pubkeys'][0]], key_descs[info['pubkeys'][1]])))
         elif typ == 'p2sh-segwit':
             # P2SH-P2WSH-multisig
-            assert_equal(info['desc'], "sh(wsh(multi(2,%s,%s)))" % (key_descs[info['embedded']['pubkeys'][0]], key_descs[info['embedded']['pubkeys'][1]]))
+            assert_equal(info['desc'], descsum_create("sh(wsh(multi(2,%s,%s)))" % (key_descs[info['embedded']['pubkeys'][0]], key_descs[info['embedded']['pubkeys'][1]])))
         elif typ == 'bech32':
             # P2WSH-multisig
-            assert_equal(info['desc'], "wsh(multi(2,%s,%s))" % (key_descs[info['pubkeys'][0]], key_descs[info['pubkeys'][1]]))
+            assert_equal(info['desc'], descsum_create("wsh(multi(2,%s,%s))" % (key_descs[info['pubkeys'][0]], key_descs[info['pubkeys'][1]])))
         else:
             # Unknown type
             assert(False)