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Certificate.py
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Certificate.py
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import base64
from Crypto.Hash import *
from Common import *
RSA_algorithms = {
sha1WithRSAEncryption: SHA,
sha256WithRSAEncryption: SHA256,
sha384WithRSAEncryption: SHA384,
}
root_CA = { }
def add_root_CA(certificate):
global root_CA
try:
tree, _ = ASN1(certificate)
name = tree[0][5][-1][0][1]
publicKey = tree[0][6][1][0]
if publicKey[0:1] == b'\x00':
publicKey = publicKey[1:]
h = SHA256.new()
h.update(publicKey)
root_CA[h.digest()] = bytes_to_int(publicKey)
except Exception as e:
# print(e)
pass
def load_root_CAs(body):
lines = body.split('\n')
status = None
for line in lines:
if status is None and line == '-----BEGIN CERTIFICATE-----':
status = 'capture'
certificate = ''
elif status == 'capture' and line != '-----END CERTIFICATE-----':
certificate += line
elif status == 'capture' and line == '-----END CERTIFICATE-----':
add_root_CA(base64.b64decode(certificate))
status = None
def ASN1(body):
content_type = body[0:1]
# print('Content type: 0x' + bytes_to_str(bytes_to_hex(content_type)))
# null
if content_type == b'\x05':
return (0x00, 2)
# A0
if content_type == b'\xA0':
size = bytes_to_int(body[1:2])
elt, offset = ASN1(body[2:2+size])
return ([ elt ], 2 + size)
size = bytes_to_int(body[1:2])
if size > 128:
size -= 128
offset = 2 + size
size = bytes_to_int(body[2:2+size])
else:
offset = 2
# number, object identifier, UTF8string, printable string, UTC time
if content_type in [b'\x02', b'\x06', b'\x0C', b'\x13', b'\x17']:
return (body[offset:offset+size], offset + size)
# octet string, bit string
if content_type in [b'\x13', b'\x03', b'\xA3']:
if body[offset:offset+1] == b'\x00':
offset += 1
size -= 1
elt, _ = ASN1(body[offset:offset+size])
return (elt, offset + size)
# sequence, set
if content_type in [b'\x30', b'\x31']:
elements = []
pos = offset
size += offset
while pos < size:
elt, offset = ASN1(body[pos:])
pos += offset
elements.append(elt)
return (elements, size)
return (body, len(body))
class Certificate:
def __init__(self, certificates):
size = bytes_to_int(certificates[0:3])
certificate = certificates[3:3+size]
self.body, _ = ASN1(certificate)
size_signed_data = bytes_to_int(certificate[6:8])
self.signed_data = certificate[4:8+size_signed_data]
self.RSA_n = bytes_to_int(self.body[0][6][1][0])
self.RSA_e = bytes_to_int(self.body[0][6][1][1])
self.domain = bytes_to_str(self.body[0][5][-1][0][1])
self.signature = self.body[2]
self.algorithm = self.body[1][0]
if len(certificates) > size + 3:
self.next = Certificate(certificates[3+size:])
else:
self.next = None
def verify_signature(self, signed_data, signature, signature_algo):
hash_size = signature_algo.digest_size
hash1 = nb_to_bytes(pow(bytes_to_int(signature), self.RSA_e, self.RSA_n))[-hash_size:]
h = signature_algo.new()
h.update(signed_data)
hash2 = h.digest()
if hash1 != hash2:
print("Certificate signature failure:")
print(bytes_to_hex(hash1))
print(bytes_to_hex(hash2))
return False
return True
def verify(self, signed_data, signature, algo, domain=None):
# algo = RSA_algorithms[algo]
print("SSL Certificate: " + self.domain)
if domain is not None:
if self.domain.split('.')[0] == '*':
self.domain = '.'.join(self.domain.split('.')[1:])
domain = '.'.join(domain.split('.')[1:])
if self.domain != domain:
print("WARNING: wrong domain: %s != %s" % (self.domain, domain))
if self.algorithm not in RSA_algorithms:
raise Exception("Unknown SSL Certificate verification algorithm: %s" % bytes_to_hex(self.algorithm))
if signed_data is not None:
self.verify_signature(signed_data, signature, algo)
# If there is a parent Certificate, verify it
if self.next is not None:
self.next.verify(self.signed_data, self.signature, RSA_algorithms[self.algorithm])
return
# algo = RSA_algorithms[self.algorithm]
# self.verify_signature(self.signed_data, self.signature, algo)
# We have reached the root CA
h = SHA256.new()
h.update(nb_to_bytes(self.RSA_n))
hash = h.digest()
if hash not in root_CA:
print("WARNING: Root CA unknown: " + self.domain)
return
if self.RSA_n != root_CA[hash]:
print("WARNING: Wrong Root CA")
# print(bytes_to_hex(self.signed_data))
# print(bytes_to_hex(root_CA[hash]))