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x509.py
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x509.py
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#!/usr/bin/env python
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2014 Thomas Voegtlin
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
from datetime import datetime
import sys
import util
from util import profiler, print_error
import ecdsa
import hashlib
# algo OIDs
ALGO_RSA_SHA1 = '1.2.840.113549.1.1.5'
ALGO_RSA_SHA256 = '1.2.840.113549.1.1.11'
ALGO_RSA_SHA384 = '1.2.840.113549.1.1.12'
ALGO_RSA_SHA512 = '1.2.840.113549.1.1.13'
ALGO_ECDSA_SHA256 = '1.2.840.10045.4.3.2'
# prefixes, see http://stackoverflow.com/questions/3713774/c-sharp-how-to-calculate-asn-1-der-encoding-of-a-particular-hash-algorithm
PREFIX_RSA_SHA256 = bytearray([0x30,0x31,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x01,0x05,0x00,0x04,0x20])
PREFIX_RSA_SHA384 = bytearray([0x30,0x41,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x02,0x05,0x00,0x04,0x30])
PREFIX_RSA_SHA512 = bytearray([0x30,0x51,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x03,0x05,0x00,0x04,0x40])
# types used in ASN1 structured data
ASN1_TYPES = {
'BOOLEAN': 0x01,
'INTEGER': 0x02,
'BIT STRING': 0x03,
'OCTET STRING': 0x04,
'NULL': 0x05,
'OBJECT IDENTIFIER': 0x06,
'SEQUENCE': 0x70,
'SET': 0x71,
'PrintableString': 0x13,
'IA5String': 0x16,
'UTCTime': 0x17,
'ENUMERATED': 0x0A,
'UTF8String': 0x0C,
'PrintableString': 0x13,
}
class CertificateError(Exception):
pass
# helper functions
def bitstr_to_bytestr(s):
if s[0] != '\x00':
raise BaseException('no padding')
return s[1:]
def bytestr_to_int(s):
i = 0
for char in s:
i <<= 8
i |= ord(char)
return i
def decode_OID(s):
s = map(ord, s)
r = []
r.append(s[0] / 40)
r.append(s[0] % 40)
k = 0
for i in s[1:]:
if i < 128:
r.append(i + 128*k)
k = 0
else:
k = (i - 128) + 128*k
return '.'.join(map(str, r))
def encode_OID(oid):
x = map(int, oid.split('.'))
s = chr(x[0]*40 + x[1])
for i in x[2:]:
ss = chr(i % 128)
while i > 128:
i = i / 128
ss = chr(128 + i % 128) + ss
s += ss
return s
class ASN1_Node(str):
def get_node(self, ix):
# return index of first byte, first content byte and last byte.
first = ord(self[ix+1])
if (ord(self[ix+1]) & 0x80) == 0:
length = first
ixf = ix + 2
ixl = ixf + length - 1
else:
lengthbytes = first & 0x7F
length = bytestr_to_int(self[ix+2:ix+2+lengthbytes])
ixf = ix + 2 + lengthbytes
ixl = ixf + length -1
return (ix, ixf, ixl)
def root(self):
return self.get_node(0)
def next_node(self, node):
ixs, ixf, ixl = node
return self.get_node(ixl + 1)
def first_child(self, node):
ixs, ixf, ixl = node
if ord(self[ixs]) & 0x20 != 0x20:
raise BaseException('Can only open constructed types.', hex(ord(self[ixs])))
return self.get_node(ixf)
def is_child_of(node1, node2):
ixs, ixf, ixl = node1
jxs, jxf, jxl = node2
return ( (ixf <= jxs) and (jxl <= ixl) ) or ( (jxf <= ixs) and (ixl <= jxl) )
def get_all(self, node):
# return type + length + value
ixs, ixf, ixl = node
return self[ixs:ixl+1]
def get_value_of_type(self, node, asn1_type):
# verify type byte and return content
ixs, ixf, ixl = node
if ASN1_TYPES[asn1_type] != ord(self[ixs]):
raise BaseException('Wrong type:', hex(ord(self[ixs])), hex(ASN1_TYPES[asn1_type]) )
return self[ixf:ixl+1]
def get_value(self, node):
ixs, ixf, ixl = node
return self[ixf:ixl+1]
def get_children(self, node):
nodes = []
ii = self.first_child(node)
nodes.append(ii)
while ii[2] < node[2]:
ii = self.next_node(ii)
nodes.append(ii)
return nodes
def get_sequence(self):
return map(lambda j: self.get_value(j), self.get_children(self.root()))
def get_dict(self, node):
p = {}
for ii in self.get_children(node):
for iii in self.get_children(ii):
iiii = self.first_child(iii)
oid = decode_OID(self.get_value_of_type(iiii, 'OBJECT IDENTIFIER'))
iiii = self.next_node(iiii)
value = self.get_value(iiii)
p[oid] = value
return p
class X509(object):
def __init__(self, b):
self.bytes = bytearray(b)
der = ASN1_Node(str(b))
root = der.root()
cert = der.first_child(root)
# data for signature
self.data = der.get_all(cert)
# optional version field
if der.get_value(cert)[0] == chr(0xa0):
version = der.first_child(cert)
serial_number = der.next_node(version)
else:
serial_number = der.first_child(cert)
self.serial_number = bytestr_to_int(der.get_value_of_type(serial_number, 'INTEGER'))
# signature algorithm
sig_algo = der.next_node(serial_number)
ii = der.first_child(sig_algo)
self.sig_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))
# issuer
issuer = der.next_node(sig_algo)
self.issuer = der.get_dict(issuer)
# validity
validity = der.next_node(issuer)
ii = der.first_child(validity)
self.notBefore = der.get_value_of_type(ii, 'UTCTime')
ii = der.next_node(ii)
self.notAfter = der.get_value_of_type(ii, 'UTCTime')
# subject
subject = der.next_node(validity)
self.subject = der.get_dict(subject)
subject_pki = der.next_node(subject)
public_key_algo = der.first_child(subject_pki)
ii = der.first_child(public_key_algo)
self.public_key_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))
# pubkey modulus and exponent
subject_public_key = der.next_node(public_key_algo)
spk = der.get_value_of_type(subject_public_key, 'BIT STRING')
spk = ASN1_Node(bitstr_to_bytestr(spk))
r = spk.root()
modulus = spk.first_child(r)
exponent = spk.next_node(modulus)
rsa_n = spk.get_value_of_type(modulus, 'INTEGER')
rsa_e = spk.get_value_of_type(exponent, 'INTEGER')
self.modulus = ecdsa.util.string_to_number(rsa_n)
self.exponent = ecdsa.util.string_to_number(rsa_e)
# extensions
self.CA = False
self.AKI = None
self.SKI = None
i = subject_pki
while i[2] < cert[2]:
i = der.next_node(i)
d = der.get_dict(i)
for oid, value in d.items():
value = ASN1_Node(value)
if oid == '2.5.29.19':
# Basic Constraints
self.CA = bool(value)
elif oid == '2.5.29.14':
# Subject Key Identifier
r = value.root()
value = value.get_value_of_type(r, 'OCTET STRING')
self.SKI = value.encode('hex')
elif oid == '2.5.29.35':
# Authority Key Identifier
self.AKI = value.get_sequence()[0].encode('hex')
else:
pass
# cert signature
cert_sig_algo = der.next_node(cert)
ii = der.first_child(cert_sig_algo)
self.cert_sig_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))
cert_sig = der.next_node(cert_sig_algo)
self.signature = der.get_value(cert_sig)[1:]
def get_keyID(self):
# http://security.stackexchange.com/questions/72077/validating-an-ssl-certificate-chain-according-to-rfc-5280-am-i-understanding-th
return self.SKI if self.SKI else repr(self.subject)
def get_issuer_keyID(self):
return self.AKI if self.AKI else repr(self.issuer)
def get_common_name(self):
return self.subject.get('2.5.4.3', 'unknown')
def get_signature(self):
return self.cert_sig_algo, self.signature, self.data
def check_ca(self):
return self.CA
def check_date(self):
import time
now = time.time()
TIMESTAMP_FMT = '%y%m%d%H%M%SZ'
not_before = time.mktime(time.strptime(self.notBefore, TIMESTAMP_FMT))
not_after = time.mktime(time.strptime(self.notAfter, TIMESTAMP_FMT))
if not_before > now:
raise CertificateError('Certificate has not entered its valid date range. (%s)'%self.get_common_name())
if not_after <= now:
raise CertificateError('Certificate has expired. (%s)'%self.get_common_name())
def getFingerprint(self):
return hashlib.sha1(self.bytes).digest()
@profiler
def load_certificates(ca_path):
import pem
ca_list = {}
ca_keyID = {}
with open(ca_path, 'r') as f:
s = f.read()
bList = pem.dePemList(s, "CERTIFICATE")
for b in bList:
try:
x = X509(b)
x.check_date()
except BaseException as e:
util.print_error("cert error:", e)
continue
fp = x.getFingerprint()
ca_list[fp] = x
ca_keyID[x.get_keyID()] = fp
return ca_list, ca_keyID
if __name__ == "__main__":
import requests
util.set_verbosity(True)
ca_path = requests.certs.where()
ca_list, ca_keyID = load_certificates(ca_path)