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cdoc_tools.py
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cdoc_tools.py
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#!/usr/bin/python3
# apt-get install python3-m2crypto python3-pyasn1 python3-pycryptodome
import sys, os, math, hashlib, codecs
from M2Crypto import X509, EC
from pyasn1.codec.der import decoder
from Cryptodome.Cipher import AES
from Cryptodome.Util.strxor import strxor
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import (Cipher, algorithms, modes)
def ib(i, l=0):
s = b""
while i or l > 0:
s = bytes([0xff & i]) + s
i >>= 8
l-=1
return s
def concatKDF_SHA384(z, outlen, otherinfo):
reps = int(math.ceil(outlen/32.0))
output = b""
for i in range(1,reps+1):
output+= hashlib.sha384(ib(i,4)+z+otherinfo).digest()
return output[:outlen]
def aes_wrap(kek, plain):
encrypt = AES.new(kek, AES.MODE_ECB).encrypt
n = len(plain)//8
R = [None] + [plain[i*8:i*8+8] for i in range(0, n)]
A = codecs.decode("A6A6A6A6A6A6A6A6", 'hex')
for j in range(0, 6):
for i in range(1, n+1):
plaintext = A + R[i]
B = encrypt(plaintext)
A = strxor(B[:8], ib(n*j+i,8))
R[i] = B[8:]
R[0] = A
return b"".join(R)
def aes_gcm_encrypt(key, plaintext, iv):
encryptor = Cipher(algorithms.AES(key), modes.GCM(iv), backend=default_backend()).encryptor()
ciphertext = encryptor.update(plaintext)
encryptor.finalize()
return (ciphertext, encryptor.tag)
def encrypt_cdoc(filename, content, certs, outfile = None):
#print(f"Creating {outfile} for {len(certs)} certs...")
xml = """<?xml version="1.0" encoding="UTF-8"?>
<denc:EncryptedData xmlns:denc="http://www.w3.org/2001/04/xmlenc#" MimeType="application/octet-stream">
<denc:EncryptionMethod Algorithm="http://www.w3.org/2009/xmlenc11#aes256-gcm"/>
<ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">%keyinfos%
</ds:KeyInfo>
<denc:CipherData>
<denc:CipherValue>%ciphervalue%
</denc:CipherValue>
</denc:CipherData>
<denc:EncryptionProperties>
<denc:EncryptionProperty Name="LibraryVersion">qdigidocclient|3.13.2.1498</denc:EncryptionProperty>
<denc:EncryptionProperty Name="Filename">%filename%</denc:EncryptionProperty>
<denc:EncryptionProperty Name="DocumentFormat">ENCDOC-XML|1.1</denc:EncryptionProperty>
<denc:EncryptionProperty Name="orig_file">%filename%|%filesize%|application/octet-stream|D0</denc:EncryptionProperty>
</denc:EncryptionProperties>
</denc:EncryptedData>
"""
#content = bytes(data, "utf-8")
xml = xml.replace('%filename%', os.path.basename(filename))
xml = xml.replace('%filesize%', str(len(content)))
# AES encrypt the data
aes_key = os.urandom(32)
iv = os.urandom(12)
ciphertext, tag = aes_gcm_encrypt(aes_key, content, iv)
ciphertext = iv + ciphertext + tag
xml = xml.replace('%ciphervalue%', codecs.encode(ciphertext, 'base64').strip().decode())
xml_encryptedkey_RSA = """
<denc:EncryptedKey Recipient="%recipient%">
<denc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5"/>
<ds:KeyInfo>
<ds:X509Data>
<ds:X509Certificate>%x509certificate%
</ds:X509Certificate>
</ds:X509Data>
</ds:KeyInfo>
<denc:CipherData>
<denc:CipherValue>%ciphervalue%
</denc:CipherValue>
</denc:CipherData>
</denc:EncryptedKey>"""
xml_encryptedkey_ECC = """
<denc:EncryptedKey Recipient="%recipient%">
<denc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#kw-aes256"/>
<ds:KeyInfo>
<denc:AgreementMethod Algorithm="http://www.w3.org/2009/xmlenc11#ECDH-ES">
<denc11:KeyDerivationMethod xmlns:denc11="http://www.w3.org/2009/xmlenc11#" Algorithm="http://www.w3.org/2009/xmlenc11#ConcatKDF">
<denc11:ConcatKDFParams AlgorithmID="00%AlgorithmID%" PartyUInfo="00%PartyUInfo%" PartyVInfo="00%PartyVInfo%">
<ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha384"/>
</denc11:ConcatKDFParams>
</denc11:KeyDerivationMethod>
<denc:OriginatorKeyInfo>
<ds:KeyValue>
<dsig11:ECKeyValue xmlns:dsig11="http://www.w3.org/2009/xmldsig11#">
<dsig11:NamedCurve URI="urn:oid:%curve_oid%"/>
<dsig11:PublicKey>%ephemeral_pubkey%
</dsig11:PublicKey>
</dsig11:ECKeyValue>
</ds:KeyValue>
</denc:OriginatorKeyInfo>
<denc:RecipientKeyInfo>
<ds:X509Data>
<ds:X509Certificate>%x509certificate%
</ds:X509Certificate>
</ds:X509Data>
</denc:RecipientKeyInfo>
</denc:AgreementMethod>
</ds:KeyInfo>
<denc:CipherData>
<denc:CipherValue>%ciphervalue%
</denc:CipherValue>
</denc:CipherData>
</denc:EncryptedKey>"""
keyinfos = ""
for cert_string in certs: # add EncryptedKey element for every recipient
cert = X509.load_cert_string(cert_string, X509.FORMAT_PEM)
subject = cert.get_subject()
# print(subject)
# if subject.OU != "authentication":
# print("[-] Only authentication certificates are supported (%s): %s" % (certfile, subject.OU))
# sys.exit(1)
recipient = subject.CN
if "\x00" in subject.CN:
recipient = subject.CN.decode('utf_16_be').encode('utf8')
# if subject.O == "ESTEID":
# recipient+=",ID-KAART"
# elif subject.O == "ESTEID (DIGI-ID)":
# recipient+=",DIGI-ID"
# else:
# print("[-] Unknown type of certificate (%s): %s" % (certfile, subject.O))
# sys.exit(1)
# encrypt AES transport key
pub_key = cert.get_pubkey()
# ECC case
EC_pubkey = EC.pub_key_from_der(pub_key.as_der())
EC_keypair = EC.gen_params(EC.NID_secp384r1)
EC_keypair.gen_key()
shared_secret = EC_keypair.compute_dh_key(EC_pubkey)
# format public key
der = EC_keypair.pub().get_der()
curve_oid = str(decoder.decode(bytes(der))[0][0][1])
pubkey_bits = list(decoder.decode(bytes(der))[0][1])
pubkey = ib((int(''.join(map(str, pubkey_bits)), 2)))
# derive wrap key (KEK) from shared secret
wrap_key = concatKDF_SHA384(shared_secret, 32, b"ENCDOC-XML|1.1"+pubkey+cert.as_der())
ciphertext = aes_wrap(wrap_key, aes_key)
keyinfos += xml_encryptedkey_ECC\
.replace('%recipient%', recipient)\
.replace('%AlgorithmID%', codecs.encode(b"ENCDOC-XML|1.1", 'hex').decode().upper())\
.replace('%PartyUInfo%', codecs.encode(pubkey, 'hex').decode().upper())\
.replace('%PartyVInfo%', codecs.encode(cert.as_der(), 'hex').decode().upper())\
.replace('%curve_oid%', curve_oid)\
.replace('%ephemeral_pubkey%', codecs.encode(pubkey, 'base64').strip().decode())\
.replace('%x509certificate%', codecs.encode(cert.as_der(), 'base64').strip().decode())\
.replace('%ciphervalue%', codecs.encode(ciphertext, 'base64').strip().decode())
xml = xml.replace('%keyinfos%', keyinfos)
if outfile:
open(outfile, 'wb').write(xml.encode())
else:
return xml.encode()