bech32+lnaddr: Add Support for Segwit Fallback Adressess

Author: MPins

bech32.py

@@ -41,25 +41,33 @@ def bech32_hrp_expand(hrp):
     return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp]
 
 
-def bech32_verify_checksum(hrp, data):
+def bech32_verify_checksum(hrp, data, segwit_version):
     """Verify a checksum given HRP and converted data characters."""
-    return bech32_polymod(bech32_hrp_expand(hrp) + data) == 1
+    if segwit_version == 0:
+        const = 1  # Bech32
+    else:
+        const = 0x2bc830a3  # Bech32m   
+    return bech32_polymod(bech32_hrp_expand(hrp) + data) == const
 
 
-def bech32_create_checksum(hrp, data):
+def bech32_create_checksum(hrp, data, segwit_version):
     """Compute the checksum values given HRP and data."""
     values = bech32_hrp_expand(hrp) + data
-    polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ 1
+    if segwit_version == 0:
+        const = 1  # Bech32
+    else:
+        const = 0x2bc830a3  # Bech32m
+    polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ const
     return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)]
 
 
-def bech32_encode(hrp, data):
+def bech32_encode(hrp, data, segwit_version=0):
     """Compute a Bech32 string given HRP and data values."""
-    combined = data + bech32_create_checksum(hrp, data)
+    combined = data + bech32_create_checksum(hrp, data, segwit_version)
     return hrp + '1' + ''.join([CHARSET[d] for d in combined])
 
 
-def bech32_decode(bech):
+def bech32_decode(bech, segwit_version_verify=False):
     """Validate a Bech32 string, and determine HRP and data."""
     if ((any(ord(x) < 33 or ord(x) > 126 for x in bech)) or
             (bech.lower() != bech and bech.upper() != bech)):
@@ -72,7 +80,7 @@ def bech32_decode(bech):
         return (None, None)
     hrp = bech[:pos]
     data = [CHARSET.find(x) for x in bech[pos+1:]]
-    if not bech32_verify_checksum(hrp, data):
+    if not bech32_verify_checksum(hrp, data, data[0] if segwit_version_verify else 0):
         return (None, None)
     return (hrp, data[:-6])
 

lnaddr.py

@@ -78,7 +78,7 @@ def encode_fallback(fallback, currency):
     """ Encode all supported fallback addresses.
     """
     if currency == 'bc' or currency == 'tb' or currency == 'tbs' or currency == 'bcrt':
-        fbhrp, witness = bech32_decode(fallback)
+        fbhrp, witness = bech32_decode(fallback, segwit_version_verify=True)
         if fbhrp:
             if fbhrp != currency:
                 raise ValueError("Not a bech32 address for this currency")
@@ -109,7 +109,7 @@ def parse_fallback(fallback, currency):
             addr=base58.b58encode_check(bytes([base58_prefix_map[currency][1]])
                                         + fallback[5:].tobytes())
         elif wver <= 16:
-            addr=bech32_encode(currency, bitarray_to_u5(fallback))
+            addr=bech32_encode(currency, bitarray_to_u5(fallback), wver)
         else:
             return None
     else: