PDF Signing using hardware token (DSC) in Python

Hardware based tokens are widely used in India to generate signed PDF’s like invoices and agreement. We wrote small Python code to sign the invoices automatically where token was attached to a local server.

Windows drives are widely available but rare to find linux drivers are listed https://www.e-mudhra.com/Repository/index.html

You can uncomment to get the token name print(self.pkcs11.getSlotList(tokenPresent=True))
print(self.pkcs11.getTokenInfo(1)) to get token name, for PROXKey the name "WD PROXKey" was generated.

#!/usr/bin/env vpython3
# *-* coding: utf-8 *-*
import sys
import datetime
from endesive import pdf, hsm

import os
import sys

if sys.platform == 'win32':
    dllpath = r'c:\windows\system32\cryptoCertum3PKCS.dll'
else:
    dllpath = '/usr/lib/WatchData/ProxKey/lib/libwdpkcs_SignatureP11.so'

import PyKCS11 as PK11

class Signer(hsm.HSM):
    def certificate(self):
        #print(self.pkcs11.getSlotList(tokenPresent=True))
        #print(self.pkcs11.getTokenInfo(1))
#        print(self.pkcs11.getTokenInfo(2))
#        print(self.pkcs11.getTokenInfo(3))


#        print(self.pkcs11.getSlotInfo(1))
        self.login("WD PROXKey","12345678") # WF PROXKey is token name.
        keyid = [0x5e, 0x9a, 0x33, 0x44, 0x8b, 0xc3, 0xa1, 0x35, 0x33, 0xc7, 0xc2, 0x02, 0xf6, 0x9b, 0xde, 0x55, 0xfe, 0x83, 0x7b, 0xde]
        #keyid = [0x3f, 0xa6, 0x63, 0xdb, 0x75, 0x97, 0x5d, 0xa6, 0xb0, 0x32, 0xef, 0x2d, 0xdc, 0xc4, 0x8d, 0xe8]
        keyid = bytes(keyid)
        try:
            pk11objects = self.session.findObjects([(PK11.CKA_CLASS, PK11.CKO_CERTIFICATE)])
            all_attributes = [
                #PK11.CKA_SUBJECT,
                PK11.CKA_VALUE,
                #PK11.CKA_ISSUER,
                #PK11.CKA_CERTIFICATE_CATEGORY,
                #PK11.CKA_END_DATE,
                PK11.CKA_ID,
            ]

            for pk11object in pk11objects:
                try:
                    attributes = self.session.getAttributeValue(pk11object, all_attributes)
                except PK11.PyKCS11Error as e:
                    continue

                attrDict = dict(list(zip(all_attributes, attributes)))
                cert = bytes(attrDict[PK11.CKA_VALUE])
                #if keyid == bytes(attrDict[PK11.CKA_ID]):
                return bytes(attrDict[PK11.CKA_ID]), cert
        finally:
            self.logout()
        return None, None

    def sign(self, keyid, data, mech):
        self.login("WD PROXKey","12345678")
        try:
            privKey = self.session.findObjects([(PK11.CKA_CLASS, PK11.CKO_PRIVATE_KEY)])[0]
            mech = getattr(PK11, 'CKM_%s_RSA_PKCS' % mech.upper())
            sig = self.session.sign(privKey, data, PK11.Mechanism(mech, None))
            return bytes(sig)
        finally:
            self.logout()

def main():
    date = datetime.datetime.utcnow() - datetime.timedelta(hours=12)
    date = date.strftime('%Y%m%d%H%M%S+00\'00\'')
    dct = {
        "sigflags": 3,
        "sigpage": 0,
        "sigbutton": True,
        "contact": "madhurendra@tikaj.com",
        "location": 'India',
        "signingdate": date.encode(),
        "reason": 'Sample sign',
        "signature": 'Madhurendra Sachan',
        "signaturebox": (0, 0, 100, 100),
    }
    clshsm = Signer(dllpath)
    fname = 'sample.pdf'
    datau = open(fname, 'rb').read()
    datas = pdf.cms.sign(datau, dct,
        None, None,
        [],
        'sha256',
        clshsm,
    )
    fname = fname.replace('.pdf', '-signed.pdf')
    with open(fname, 'wb') as fp:
        fp.write(datau)
        fp.write(datas)


main()

.dll/.so path for common tokens

• For Windows the file will be in Windows\SysWOW64″ or “WINDOWS\system32” or “WINNT\system32”
• For Linux machine the file will be in /usr/local/lib/ or /usr/lib/

Hardware Token Type	Library file (Windows)	Library file (Linux)
SafeSign	aetpkss1.dll	aetpkss1.so
eMudhra	eMudhra\eMudhra CSPV1.0\wdpkcs.dll	1. WatchData/eMudhra_3.4.3/lib/libpkcs11wrapper.so 2. WatchData/eMudhra_3.4.3/lib/libwdpkcs_eMudhra_343.so
Trust Key	1. TRUST KEY\TRUST KEY CSP V1.0\wdpkcs.dll 2. C:\Windows\System32\TRUSTKEYP11_ND_v34.dll	1. WatchData/TRUSTKEY/lib/libpkcs11wrapper.so 2. WatchData/TRUSTKEY/lib/libwdpkcs_TRUSTKEY.so
Belgium eID MiddleWare	beidpkcs11.dll	beidpkcs11.so
Gemalto Cryptocard Token	libgtop11dotnet.dll	libgtop11dotnet.so
EPass	eps2003csp11.dll
Aladdin eToken	eTPKCS11.dll
Safenet iKey	dkck201.dll
Starkey	aetpkss1.dll
Watchdata PROXkey	SignatureP11.dll	WatchData/ProxKey/lib/libwdpkcs_SignatureP11.so