gistfile1.py

#!/usr/bin/python
import re
import sys
import base64
import urllib 

from M2Crypto import BIO, RSA, EVP 
pem = """-----BEGIN PUBLIC KEY-----MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCt8WGFD2HH1sHbdtrZ0MspHueVDb2vjk2G11qLoxZiTehfRTmlKivFMkdC/4PMtF73Z4kjHDr+7lU9b4DmkcNyZ03DsrRtudY9cGWh0cYCCsODjScjSCKpfTPUj/3Rxe6hcqhfIWw3XuduaALBnT31NR499Qodp859RnBpuwSieQIDAQAB-----END PUBLIC KEY-----""" 
bio = BIO.MemoryBuffer(pem)
rsa = RSA.load_pub_key_bio(bio)
pubkey = EVP.PKey()
pubkey.assign_rsa(rsa) 

if len(sys.argv) == 2:    
  qs = sys.argv[1];    
  signature= base64.decodestring(urllib.unquote(re.match(r".*signature=([Verify signature^&]*).*",qs).group(1)))    
  qs = re.compile("signature=[Verify signature^&]*").sub("signature=",qs)     
  
  print "\nUsing the following publickey:"    
  print pem    
  print "\nVerifying the signature of the following query string:"    
  print "[" + qs + "]"     
  
  pubkey.reset_context(md='sha1')    
  pubkey.verify_init()    
  pubkey.verify_update(qs)     
  
  if pubkey.verify_final(signature) == 1:        
    print "\nRESULT:signature is valid"        
    sys.exit(0)    
  else:        
    print "\nRESULT:could not verify signature"        
    sys.exit(1)
else:
  print "must specify the querystring as an argument"