Gavin_Andresen - 2010-09-13 12:38:24

This bitcoind address validator is a subclass of the Django forms.CharField class, but could easily be adapted to other frameworks or to be standalone code.

It does a "deep" validation, checking that the checksum built into every bitcoin address matches the address. It needs the PyCrypto library for the SHA256 function.

I hereby release this code into the public domain, do with it what you will. And please let me know if you find any bugs in it.

BCAddressField.py:

Code:

#
# DJango field type for a Bitcoin Address
#
import re
from django import forms
from django.forms.util import ValidationError
from Crypto.Hash import SHA256

class BCAddressField(forms.CharField):
  default_error_messages = {
   'invalid': 'Invalid Bitcoin address.',
   }

  def __init__(self, *args, **kwargs):
   super(BCAddressField, self).__init__(*args, **kwargs)

  def clean(self, value):
   value = value.strip()
   if re.match(r"[a-zA-Z1-9]{27,35}$", value) is None:
   raise ValidationError(self.error_messages['invalid'])
   version = get_bcaddress_version(value)
   if version is None:
   raise ValidationError(self.error_messages['invalid'])
   return value

import math

__b58chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
__b58base = len(__b58chars)

def b58encode(v):
  """ encode v, which is a string of bytes, to base58.
  """

  long_value = 0L
  for (i, c) in enumerate(v[::-1]):
   long_value += (256**i) * ord(c)

  result = ''
  while long_value >= __b58base:
   div, mod = divmod(long_value, __b58base)
   result = __b58chars[mod] + result
   long_value = div
  result = __b58chars[long_value] + result

  # Bitcoin does a little leading-zero-compression:
  # leading 0-bytes in the input become leading-1s
  nPad = 0
  for c in v:
   if c == '\0': nPad += 1
   else: break

  return (__b58chars[0]*nPad) + result

def b58decode(v, length):
  """ decode v into a string of len bytes
  """
  long_value = 0L
  for (i, c) in enumerate(v[::-1]):
   long_value += __b58chars.find(c) * (__b58base**i)

  result = ''
  while long_value >= 256:
   div, mod = divmod(long_value, 256)
   result = chr(mod) + result
   long_value = div
  result = chr(long_value) + result

  nPad = 0
  for c in v:
   if c == __b58chars[0]: nPad += 1
   else: break

  result = chr(0)*nPad + result
  if length is not None and len(result) != length:
   return None

  return result

def get_bcaddress_version(strAddress):
  """ Returns None if strAddress is invalid. Otherwise returns integer version of address. """
  addr = b58decode(strAddress,25)
  if addr is None: return None
  version = addr[0]
  checksum = addr[-4:]
  vh160 = addr[:-4] # Version plus hash160 is what is checksummed
  h3=SHA256.new(SHA256.new(vh160).digest()).digest()
  if h3[0:4] == checksum:
   return ord(version)
  return None

October 20: Fixed bug with bitcoin addresses with leading-1's.

Gavin Andresen - 2010-09-13 12:38:24