New class for decoding asn1 structures
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ThomasV
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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# MA 02110-1301, USA.
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# This is a simple and fast ASN1 decoder without external libraries.
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#
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# In order to browse through the ASN1 structure you need only 3
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# functions allowing you to navigate:
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# asn1_node_root(...), asn1_node_next(...) and asn1_node_first_child(...)
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#
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####################### BEGIN ASN1 DECODER ############################
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# Author: Jens Getreu, 8.11.2014
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##### NAVIGATE
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# The following 4 functions are all you need to parse an ASN1 structure
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# gets the first ASN1 structure in der
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def asn1_node_root(der):
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return asn1_read_length(der,0)
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# gets the next ASN1 structure following (ixs,ixf,ixl)
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def asn1_node_next(der, (ixs,ixf,ixl)):
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return asn1_read_length(der,ixl+1)
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# opens the container (ixs,ixf,ixl) and returns the first ASN1 inside
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def asn1_node_first_child(der, (ixs,ixf,ixl)):
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if ord(der[ixs]) & 0x20 != 0x20:
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raise ValueError('Error: can only open constructed types. '
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+'Found type: 0x'+der[ixs].encode("hex"))
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return asn1_read_length(der,ixf)
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# is true if one ASN1 chunk is inside another chunk.
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def asn1_node_is_child_of((ixs,ixf,ixl), (jxs,jxf,jxl)):
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return ( (ixf <= jxs ) and (jxl <= ixl) ) or \
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( (jxf <= ixs ) and (ixl <= jxl) )
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##### END NAVIGATE
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##### ACCESS PRIMITIVES
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# get content and verify type byte
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def asn1_get_value_of_type(der,(ixs,ixf,ixl),asn1_type):
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asn1_type_table = {
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'BOOLEAN': 0x01, 'INTEGER': 0x02,
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'BIT STRING': 0x03, 'OCTET STRING': 0x04,
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'NULL': 0x05, 'OBJECT IDENTIFIER': 0x06,
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'SEQUENCE': 0x70, 'SET': 0x71,
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'PrintableString': 0x13, 'IA5String': 0x16,
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'UTCTime': 0x17, 'ENUMERATED': 0x0A,
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'UTF8String': 0x0C, 'PrintableString': 0x13,
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}
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if asn1_type_table[asn1_type] != ord(der[ixs]):
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raise ValueError('Error: Expected type was: '+
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hex(asn1_type_table[asn1_type])+
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' Found: 0x'+der[ixs].encode('hex'))
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return der[ixf:ixl+1]
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# get value
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def asn1_get_value(der,(ixs,ixf,ixl)):
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return der[ixf:ixl+1]
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# get type+length+value
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def asn1_get_all(der,(ixs,ixf,ixl)):
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return der[ixs:ixl+1]
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##### END ACCESS PRIMITIVES
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##### HELPER FUNCTIONS
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# converter
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def bitstr_to_bytestr(bitstr):
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if bitstr[0] != '\x00':
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raise ValueError('Error: only 00 padded bitstr can be converted to bytestr!')
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return bitstr[1:]
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# converter
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def bytestr_to_int(s):
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# converts bytestring to integer
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i = 0
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for char in s:
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i <<= 8
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i |= ord(char)
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return i
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# ix points to the first byte of the asn1 structure
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# Returns first byte pointer, first content byte pointer and last.
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def asn1_read_length(der,ix):
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first= ord(der[ix+1])
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if (ord(der[ix+1]) & 0x80) == 0:
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length = first
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ix_first_content_byte = ix+2
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ix_last_content_byte = ix_first_content_byte + length -1
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else:
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lengthbytes = first & 0x7F
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length = bytestr_to_int(der[ix+2:ix+2+lengthbytes])
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ix_first_content_byte = ix+2+lengthbytes
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ix_last_content_byte = ix_first_content_byte + length -1
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return (ix,ix_first_content_byte,ix_last_content_byte)
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##### END HELPER FUNCTIONS
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####################### END ASN1 DECODER ############################
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def decode_OID(s):
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s = map(ord, s)
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r = []
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r.append(s[0] / 40)
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r.append(s[0] % 40)
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k = 0
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for i in s[1:]:
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if i < 128:
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r.append(i + 128*k)
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k = 0
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else:
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k = (i - 128) + 128*k
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return '.'.join(map(str, r))
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def encode_OID(oid):
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x = map(int, oid.split('.'))
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s = chr(x[0]*40 + x[1])
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for i in x[2:]:
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ss = chr(i % 128)
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while i > 128:
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i = i / 128
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ss = chr(128 + i % 128) + ss
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s += ss
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return s
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def asn1_get_children(der, i):
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nodes = []
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ii = asn1_node_first_child(der,i)
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nodes.append(ii)
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while ii[2]<i[2]:
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ii = asn1_node_next(der,ii)
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nodes.append(ii)
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return nodes
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def asn1_get_sequence(s):
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return map(lambda j: asn1_get_value(s, j), asn1_get_children(s, asn1_node_root(s)))
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def asn1_get_dict(der, i):
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p = {}
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for ii in asn1_get_children(der, i):
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for iii in asn1_get_children(der, ii):
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iiii = asn1_node_first_child(der, iii)
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oid = decode_OID(asn1_get_value_of_type(der, iiii, 'OBJECT IDENTIFIER'))
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iiii = asn1_node_next(der, iiii)
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value = asn1_get_value(der, iiii)
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p[oid] = value
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return p
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233
lib/x509.py
233
lib/x509.py
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@ -19,11 +19,8 @@
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from datetime import datetime
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import sys
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import util
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from util import profiler, print_error
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from asn1tinydecoder import *
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import ecdsa
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import hashlib
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@ -40,11 +37,142 @@ PREFIX_RSA_SHA256 = bytearray([0x30,0x31,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01
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PREFIX_RSA_SHA384 = bytearray([0x30,0x41,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x02,0x05,0x00,0x04,0x30])
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PREFIX_RSA_SHA512 = bytearray([0x30,0x51,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x03,0x05,0x00,0x04,0x40])
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# types used in ASN1 structured data
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ASN1_TYPES = {
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'BOOLEAN': 0x01,
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'INTEGER': 0x02,
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'BIT STRING': 0x03,
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'OCTET STRING': 0x04,
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'NULL': 0x05,
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'OBJECT IDENTIFIER': 0x06,
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'SEQUENCE': 0x70,
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'SET': 0x71,
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'PrintableString': 0x13,
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'IA5String': 0x16,
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'UTCTime': 0x17,
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'ENUMERATED': 0x0A,
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'UTF8String': 0x0C,
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'PrintableString': 0x13,
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}
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class CertificateError(Exception):
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pass
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# helper functions
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def bitstr_to_bytestr(s):
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if s[0] != '\x00':
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raise BaseException('no padding')
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return s[1:]
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def bytestr_to_int(s):
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i = 0
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for char in s:
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i <<= 8
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i |= ord(char)
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return i
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def decode_OID(s):
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s = map(ord, s)
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r = []
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r.append(s[0] / 40)
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r.append(s[0] % 40)
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k = 0
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for i in s[1:]:
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if i < 128:
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r.append(i + 128*k)
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k = 0
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else:
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k = (i - 128) + 128*k
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return '.'.join(map(str, r))
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def encode_OID(oid):
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x = map(int, oid.split('.'))
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s = chr(x[0]*40 + x[1])
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for i in x[2:]:
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ss = chr(i % 128)
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while i > 128:
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i = i / 128
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ss = chr(128 + i % 128) + ss
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s += ss
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return s
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class ASN1_Node(str):
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def get_node(self, ix):
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# return index of first byte, first content byte and last byte.
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first = ord(self[ix+1])
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if (ord(self[ix+1]) & 0x80) == 0:
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length = first
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ixf = ix + 2
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ixl = ixf + length - 1
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else:
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lengthbytes = first & 0x7F
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length = bytestr_to_int(self[ix+2:ix+2+lengthbytes])
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ixf = ix + 2 + lengthbytes
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ixl = ixf + length -1
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return (ix, ixf, ixl)
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def root(self):
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return self.get_node(0)
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def next_node(self, node):
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ixs, ixf, ixl = node
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return self.get_node(ixl + 1)
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def first_child(self, node):
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ixs, ixf, ixl = node
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if ord(self[ixs]) & 0x20 != 0x20:
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raise BaseException('Can only open constructed types.', hex(ord(self[ixs])))
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return self.get_node(ixf)
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def is_child_of(node1, node2):
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ixs, ixf, ixl = node1
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jxs, jxf, jxl = node2
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return ( (ixf <= jxs) and (jxl <= ixl) ) or ( (jxf <= ixs) and (ixl <= jxl) )
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def get_all(self, node):
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# return type + length + value
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ixs, ixf, ixl = node
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return self[ixs:ixl+1]
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def get_value_of_type(self, node, asn1_type):
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# verify type byte and return content
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ixs, ixf, ixl = node
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if ASN1_TYPES[asn1_type] != ord(self[ixs]):
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raise BaseException('Wrong type:', hex(ord(self[ixs])), hex(ASN1_TYPES[asn1_type]) )
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return self[ixf:ixl+1]
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def get_value(self, node):
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ixs, ixf, ixl = node
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return self[ixf:ixl+1]
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def get_children(self, node):
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nodes = []
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ii = self.first_child(node)
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nodes.append(ii)
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while ii[2] < node[2]:
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ii = self.next_node(ii)
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nodes.append(ii)
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return nodes
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def get_sequence(self):
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return map(lambda j: self.get_value(j), self.get_children(self.root()))
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def get_dict(self, node):
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p = {}
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for ii in self.get_children(node):
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for iii in self.get_children(ii):
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iiii = self.first_child(iii)
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oid = decode_OID(self.get_value_of_type(iiii, 'OBJECT IDENTIFIER'))
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iiii = self.next_node(iiii)
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value = self.get_value(iiii)
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p[oid] = value
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return p
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class X509(object):
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@ -53,55 +181,53 @@ class X509(object):
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self.bytes = bytearray(b)
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der = str(b)
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root = asn1_node_root(der)
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cert = asn1_node_first_child(der, root)
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der = ASN1_Node(str(b))
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root = der.root()
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cert = der.first_child(root)
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# data for signature
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self.data = asn1_get_all(der, cert)
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self.data = der.get_all(cert)
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# optional version field
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if asn1_get_value(der, cert)[0] == chr(0xa0):
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version = asn1_node_first_child(der, cert)
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serial_number = asn1_node_next(der, version)
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if der.get_value(cert)[0] == chr(0xa0):
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version = der.first_child(cert)
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serial_number = der.next_node(version)
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else:
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serial_number = asn1_node_first_child(der, cert)
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self.serial_number = bytestr_to_int(asn1_get_value_of_type(der, serial_number, 'INTEGER'))
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serial_number = der.first_child(cert)
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self.serial_number = bytestr_to_int(der.get_value_of_type(serial_number, 'INTEGER'))
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# signature algorithm
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sig_algo = asn1_node_next(der, serial_number)
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ii = asn1_node_first_child(der, sig_algo)
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self.sig_algo = decode_OID(asn1_get_value_of_type(der, ii, 'OBJECT IDENTIFIER'))
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sig_algo = der.next_node(serial_number)
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ii = der.first_child(sig_algo)
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self.sig_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))
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# issuer
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issuer = asn1_node_next(der, sig_algo)
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self.issuer = asn1_get_dict(der, issuer)
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issuer = der.next_node(sig_algo)
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self.issuer = der.get_dict(issuer)
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# validity
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validity = asn1_node_next(der, issuer)
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ii = asn1_node_first_child(der, validity)
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self.notBefore = asn1_get_value_of_type(der, ii, 'UTCTime')
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ii = asn1_node_next(der,ii)
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self.notAfter = asn1_get_value_of_type(der, ii, 'UTCTime')
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validity = der.next_node(issuer)
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ii = der.first_child(validity)
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self.notBefore = der.get_value_of_type(ii, 'UTCTime')
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ii = der.next_node(ii)
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self.notAfter = der.get_value_of_type(ii, 'UTCTime')
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# subject
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subject = asn1_node_next(der, validity)
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self.subject = asn1_get_dict(der, subject)
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subject_pki = asn1_node_next(der, subject)
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public_key_algo = asn1_node_first_child(der, subject_pki)
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ii = asn1_node_first_child(der, public_key_algo)
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self.public_key_algo = decode_OID(asn1_get_value_of_type(der, ii, 'OBJECT IDENTIFIER'))
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subject = der.next_node(validity)
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self.subject = der.get_dict(subject)
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subject_pki = der.next_node(subject)
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public_key_algo = der.first_child(subject_pki)
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ii = der.first_child(public_key_algo)
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self.public_key_algo = decode_OID(der.get_value_of_type(ii, 'OBJECT IDENTIFIER'))
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# pubkey modulus and exponent
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subject_public_key = asn1_node_next(der, public_key_algo)
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spk = asn1_get_value_of_type(der, subject_public_key, 'BIT STRING')
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spk = bitstr_to_bytestr(spk)
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r = asn1_node_root(spk)
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modulus = asn1_node_first_child(spk, r)
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exponent = asn1_node_next(spk, modulus)
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rsa_n = asn1_get_value_of_type(spk, modulus, 'INTEGER')
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rsa_e = asn1_get_value_of_type(spk, exponent, 'INTEGER')
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subject_public_key = der.next_node(public_key_algo)
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spk = der.get_value_of_type(subject_public_key, 'BIT STRING')
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spk = ASN1_Node(bitstr_to_bytestr(spk))
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r = spk.root()
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modulus = spk.first_child(r)
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exponent = spk.next_node(modulus)
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rsa_n = spk.get_value_of_type(modulus, 'INTEGER')
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rsa_e = spk.get_value_of_type(exponent, 'INTEGER')
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self.modulus = ecdsa.util.string_to_number(rsa_n)
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self.exponent = ecdsa.util.string_to_number(rsa_e)
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@ -111,30 +237,31 @@ class X509(object):
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self.SKI = None
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i = subject_pki
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while i[2] < cert[2]:
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i = asn1_node_next(der, i)
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d = asn1_get_dict(der, i)
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i = der.next_node(i)
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d = der.get_dict(i)
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for oid, value in d.items():
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value = ASN1_Node(value)
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if oid == '2.5.29.19':
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# Basic Constraints
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||||
self.CA = bool(value)
|
||||
elif oid == '2.5.29.14':
|
||||
# Subject Key Identifier
|
||||
r = asn1_node_root(value)
|
||||
value = asn1_get_value_of_type(value, r, 'OCTET STRING')
|
||||
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 = asn1_get_sequence(value)[0].encode('hex')
|
||||
self.AKI = value.get_sequence()[0].encode('hex')
|
||||
else:
|
||||
pass
|
||||
|
||||
# cert signature
|
||||
cert_sig_algo = asn1_node_next(der, cert)
|
||||
ii = asn1_node_first_child(der, cert_sig_algo)
|
||||
self.cert_sig_algo = decode_OID(asn1_get_value_of_type(der, ii, 'OBJECT IDENTIFIER'))
|
||||
cert_sig = asn1_node_next(der, cert_sig_algo)
|
||||
self.signature = asn1_get_value(der, cert_sig)[1:]
|
||||
|
||||
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)
|
||||
|
|
@ -190,3 +317,11 @@ def load_certificates(ca_path):
|
|||
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)
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue