Trouble interpolating RSA signatures between Python and Java/Scala

Question

I'm writing a client in Python2 with the python-crypto API to digitally sign an XML file and I have a service written in Scala that is suppose to verify the signature. My Python code looks something like this:

from Crypto.PublicKey import RSA
from Crypto.Hash import SHA
from os import urandom
import logging

...
...

To generate the keys (keysize is 2048):

self.__key = RSA.generate(self.keySize,urandom)
self.__private_key = self.__key.exportKey()
self.__public_key = self.__key.publickey().exportKey()
with open(pubPath,'w') as fpub:
    logging.info("Writing Public Key to %s" % pubPath)
    fpub.write(self.__public_key)
with open(priPath,'w') as fpri:
    logging.info("Writing Private Key to %s" % priPath)
    fpri.write(self.__private_key)

And for reading in the keys:

self.__private_key = fpri.read()
self.__public_key = fpub.read()
self.__key = RSA.importKey(self.__private_key)

And to digitally sign

logging.debug('Data to sign: "%s"' % data)
digest = SHA.new(data.strip()).digest()
return str(self.__key.sign(digest, None)[0])

Then in Scala/Java, I use the following:

package com.example.security
import com.example.action.ActionRequest
import java.io.BufferedInputStream
import java.security.spec.X509EncodedKeySpec
import java.security.KeyFactory
import java.security.PublicKey
import java.security.Signature
import org.apache.log4j.Logger

class SignatureSecurityManageer extends SecurityManagerTrait {

    def loadPublicKey() : PublicKey = {
        val stream : BufferedInputStream = new BufferedInputStream(this.getClass().getResourceAsStream("/com/example/security/key.der"))
        var key = new Array[Byte](stream.available())
        stream.read(key)
        KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(key))
    }

    def securityFilter(req : ActionRequest) : Boolean = {

        var parts = req.data.split("\n\n")

        var log : Logger = Logger.getLogger(this.getClass());
        log.trace("Data \"%s\"".format(parts(0)))
        log.trace("Sig \"%s\"".format(parts(1)))

         var sg = Signature.getInstance("SHA1withRSA");
         sg.initVerify(loadPublicKey())
         sg.update(parts(0).trim().getBytes())
         sg.verify(parts(1).trim().getBytes())
    }
}

I transform the PEM public key generated by the client into a binary public key so it can be read by Java:

openssl rsa -in src/com/example/security/key.pub -inform PEM -out src/com/example/security/key.der -outform DER -pubin

In the transport, I separate the XML and the signature with double new lines. I realize trailing whitespace can present problems so I added those strip/trims above and I check the logs and verify that the data is identical:

Python Client:

2012-04-09 14:24:51,089: Data to sign: "<?xml version="1.0" ?><AgraData><package id="Local-Laptop" timestamp="1333945491074"><sensors><sensor id="SUMTEMP001" type="Temperature" units="C"><data>8</data></sensor><sensor id="SUMVOL001" type="Volume" units="l"><data>27</data></sensor><sensor id="SUMFLO001" type="FlowRate" units="l"><data>41.142</data></sensor></sensors></package></AgraData>"

Scala Service:

[2012-04-09 14:24:51,771] com.urbanalta.agrastore.security.SignatureSecurityManageer TRACE - Data "<?xml version="1.0" ?><AgraData><package id="Local-Laptop" timestamp="1333945491074"><sensors><sensor id="SUMTEMP001" type="Temperature" units="C"><data>8</data></sensor><sensor id="SUMVOL001" type="Volume" units="l"><data>27</data></sensor><sensor id="SUMFLO001" type="FlowRate" units="l"><data>41.142</data></sensor></sensors></package></AgraData>"

But within the Scala service, it returns false when I try to verify the signature. I think somewhere I'm not specifying the right signature/key type, but I'm not sure where.

Answer 1

This might be another instance of this submission where it's not just the digest but the AlgorithmIdentifier and the digest that are signed.