287 lines
13 KiB
Python
287 lines
13 KiB
Python
|
# -*- coding: ascii -*-
|
||
|
|
#
|
||
|
|
# Util/asn1.py : Minimal support for ASN.1 DER binary encoding.
|
||
|
|
#
|
||
|
|
# ===================================================================
|
||
|
|
# The contents of this file are dedicated to the public domain. To
|
||
|
|
# the extent that dedication to the public domain is not available,
|
||
|
|
# everyone is granted a worldwide, perpetual, royalty-free,
|
||
|
|
# non-exclusive license to exercise all rights associated with the
|
||
|
|
# contents of this file for any purpose whatsoever.
|
||
|
|
# No rights are reserved.
|
||
|
|
#
|
||
|
|
# 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 Crypto.Util.number import long_to_bytes, bytes_to_long
|
||
|
|
import sys
|
||
|
|
from Crypto.Util.py3compat import *
|
||
|
|
|
||
|
|
__all__ = [ 'DerObject', 'DerInteger', 'DerOctetString', 'DerNull', 'DerSequence', 'DerObjectId' ]
|
||
|
|
|
||
|
|
class DerObject:
|
||
|
|
"""Base class for defining a single DER object.
|
||
|
|
|
||
|
|
Instantiate this class ONLY when you have to decode a DER element.
|
||
|
|
"""
|
||
|
|
|
||
|
|
# Known TAG types
|
||
|
|
typeTags = { 'SEQUENCE': 0x30, 'BIT STRING': 0x03, 'INTEGER': 0x02,
|
||
|
|
'OCTET STRING': 0x04, 'NULL': 0x05, 'OBJECT IDENTIFIER': 0x06 }
|
||
|
|
|
||
|
|
def __init__(self, ASN1Type=None, payload=b('')):
|
||
|
|
"""Initialize the DER object according to a specific type.
|
||
|
|
|
||
|
|
The ASN.1 type is either specified as the ASN.1 string (e.g.
|
||
|
|
'SEQUENCE'), directly with its numerical tag or with no tag
|
||
|
|
at all (None)."""
|
||
|
|
if isInt(ASN1Type) or ASN1Type is None:
|
||
|
|
self.typeTag = ASN1Type
|
||
|
|
else:
|
||
|
|
if len(ASN1Type)==1:
|
||
|
|
self.typeTag = ord(ASN1Type)
|
||
|
|
else:
|
||
|
|
self.typeTag = self.typeTags.get(ASN1Type)
|
||
|
|
self.payload = payload
|
||
|
|
|
||
|
|
def isType(self, ASN1Type):
|
||
|
|
return self.typeTags[ASN1Type]==self.typeTag
|
||
|
|
|
||
|
|
def _lengthOctets(self, payloadLen):
|
||
|
|
"""Return a byte string that encodes the given payload length (in
|
||
|
|
bytes) in a format suitable for a DER length tag (L).
|
||
|
|
"""
|
||
|
|
if payloadLen>127:
|
||
|
|
encoding = long_to_bytes(payloadLen)
|
||
|
|
return bchr(len(encoding)+128) + encoding
|
||
|
|
return bchr(payloadLen)
|
||
|
|
|
||
|
|
def encode(self):
|
||
|
|
"""Return a complete DER element, fully encoded as a TLV."""
|
||
|
|
return bchr(self.typeTag) + self._lengthOctets(len(self.payload)) + self.payload
|
||
|
|
|
||
|
|
def _decodeLen(self, idx, der):
|
||
|
|
"""Given a (part of a) DER element, and an index to the first byte of
|
||
|
|
a DER length tag (L), return a tuple with the payload size,
|
||
|
|
and the index of the first byte of the such payload (V).
|
||
|
|
|
||
|
|
Raises a ValueError exception if the DER length is invalid.
|
||
|
|
Raises an IndexError exception if the DER element is too short.
|
||
|
|
"""
|
||
|
|
length = bord(der[idx])
|
||
|
|
if length<=127:
|
||
|
|
return (length,idx+1)
|
||
|
|
payloadLength = bytes_to_long(der[idx+1:idx+1+(length & 0x7F)])
|
||
|
|
if payloadLength<=127:
|
||
|
|
raise ValueError("Not a DER length tag.")
|
||
|
|
return (payloadLength, idx+1+(length & 0x7F))
|
||
|
|
|
||
|
|
def decode(self, derEle, noLeftOvers=0):
|
||
|
|
"""Decode a complete DER element, and re-initializes this
|
||
|
|
object with it.
|
||
|
|
|
||
|
|
@param derEle A complete DER element. It must start with a DER T
|
||
|
|
tag.
|
||
|
|
@param noLeftOvers Indicate whether it is acceptable to complete the
|
||
|
|
parsing of the DER element and find that not all
|
||
|
|
bytes in derEle have been used.
|
||
|
|
@return Index of the first unused byte in the given DER element.
|
||
|
|
|
||
|
|
Raises a ValueError exception in case of parsing errors.
|
||
|
|
Raises an IndexError exception if the DER element is too short.
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
self.typeTag = bord(derEle[0])
|
||
|
|
if (self.typeTag & 0x1F)==0x1F:
|
||
|
|
raise ValueError("Unsupported DER tag")
|
||
|
|
(length,idx) = self._decodeLen(1, derEle)
|
||
|
|
if noLeftOvers and len(derEle) != (idx+length):
|
||
|
|
raise ValueError("Not a DER structure")
|
||
|
|
self.payload = derEle[idx:idx+length]
|
||
|
|
except IndexError:
|
||
|
|
raise ValueError("Not a valid DER SEQUENCE.")
|
||
|
|
return idx+length
|
||
|
|
|
||
|
|
class DerInteger(DerObject):
|
||
|
|
def __init__(self, value = 0):
|
||
|
|
"""Class to model an INTEGER DER element.
|
||
|
|
|
||
|
|
Limitation: only non-negative values are supported.
|
||
|
|
"""
|
||
|
|
DerObject.__init__(self, 'INTEGER')
|
||
|
|
self.value = value
|
||
|
|
|
||
|
|
def encode(self):
|
||
|
|
"""Return a complete INTEGER DER element, fully encoded as a TLV."""
|
||
|
|
self.payload = long_to_bytes(self.value)
|
||
|
|
if bord(self.payload[0])>127:
|
||
|
|
self.payload = bchr(0x00) + self.payload
|
||
|
|
return DerObject.encode(self)
|
||
|
|
|
||
|
|
def decode(self, derEle, noLeftOvers=0):
|
||
|
|
"""Decode a complete INTEGER DER element, and re-initializes this
|
||
|
|
object with it.
|
||
|
|
|
||
|
|
@param derEle A complete INTEGER DER element. It must start with a DER
|
||
|
|
INTEGER tag.
|
||
|
|
@param noLeftOvers Indicate whether it is acceptable to complete the
|
||
|
|
parsing of the DER element and find that not all
|
||
|
|
bytes in derEle have been used.
|
||
|
|
@return Index of the first unused byte in the given DER element.
|
||
|
|
|
||
|
|
Raises a ValueError exception if the DER element is not a
|
||
|
|
valid non-negative INTEGER.
|
||
|
|
Raises an IndexError exception if the DER element is too short.
|
||
|
|
"""
|
||
|
|
tlvLength = DerObject.decode(self, derEle, noLeftOvers)
|
||
|
|
if self.typeTag!=self.typeTags['INTEGER']:
|
||
|
|
raise ValueError ("Not a DER INTEGER.")
|
||
|
|
if bord(self.payload[0])>127:
|
||
|
|
raise ValueError ("Negative INTEGER.")
|
||
|
|
self.value = bytes_to_long(self.payload)
|
||
|
|
return tlvLength
|
||
|
|
|
||
|
|
class DerSequence(DerObject):
|
||
|
|
"""Class to model a SEQUENCE DER element.
|
||
|
|
|
||
|
|
This object behave like a dynamic Python sequence.
|
||
|
|
Sub-elements that are INTEGERs, look like Python integers.
|
||
|
|
Any other sub-element is a binary string encoded as the complete DER
|
||
|
|
sub-element (TLV).
|
||
|
|
"""
|
||
|
|
|
||
|
|
def __init__(self, startSeq=None):
|
||
|
|
"""Initialize the SEQUENCE DER object. Always empty
|
||
|
|
initially."""
|
||
|
|
DerObject.__init__(self, 'SEQUENCE')
|
||
|
|
if startSeq==None:
|
||
|
|
self._seq = []
|
||
|
|
else:
|
||
|
|
self._seq = startSeq
|
||
|
|
|
||
|
|
## A few methods to make it behave like a python sequence
|
||
|
|
|
||
|
|
def __delitem__(self, n):
|
||
|
|
del self._seq[n]
|
||
|
|
def __getitem__(self, n):
|
||
|
|
return self._seq[n]
|
||
|
|
def __setitem__(self, key, value):
|
||
|
|
self._seq[key] = value
|
||
|
|
def __setslice__(self,i,j,sequence):
|
||
|
|
self._seq[i:j] = sequence
|
||
|
|
def __delslice__(self,i,j):
|
||
|
|
del self._seq[i:j]
|
||
|
|
def __getslice__(self, i, j):
|
||
|
|
return self._seq[max(0, i):max(0, j)]
|
||
|
|
def __len__(self):
|
||
|
|
return len(self._seq)
|
||
|
|
def append(self, item):
|
||
|
|
return self._seq.append(item)
|
||
|
|
|
||
|
|
def hasInts(self):
|
||
|
|
"""Return the number of items in this sequence that are numbers."""
|
||
|
|
return len(list(filter(isInt, self._seq)))
|
||
|
|
|
||
|
|
def hasOnlyInts(self):
|
||
|
|
"""Return True if all items in this sequence are numbers."""
|
||
|
|
return self._seq and self.hasInts()==len(self._seq)
|
||
|
|
|
||
|
|
def encode(self):
|
||
|
|
"""Return the DER encoding for the ASN.1 SEQUENCE, containing
|
||
|
|
the non-negative integers and longs added to this object.
|
||
|
|
|
||
|
|
Limitation: Raises a ValueError exception if it some elements
|
||
|
|
in the sequence are neither Python integers nor complete DER INTEGERs.
|
||
|
|
"""
|
||
|
|
self.payload = b('')
|
||
|
|
for item in self._seq:
|
||
|
|
try:
|
||
|
|
self.payload += item
|
||
|
|
except:
|
||
|
|
try:
|
||
|
|
self.payload += DerInteger(item).encode()
|
||
|
|
except:
|
||
|
|
raise ValueError("Trying to DER encode an unknown object")
|
||
|
|
return DerObject.encode(self)
|
||
|
|
|
||
|
|
def decode(self, derEle, noLeftOvers=0):
|
||
|
|
"""Decode a complete SEQUENCE DER element, and re-initializes this
|
||
|
|
object with it.
|
||
|
|
|
||
|
|
@param derEle A complete SEQUENCE DER element. It must start with a DER
|
||
|
|
SEQUENCE tag.
|
||
|
|
@param noLeftOvers Indicate whether it is acceptable to complete the
|
||
|
|
parsing of the DER element and find that not all
|
||
|
|
bytes in derEle have been used.
|
||
|
|
@return Index of the first unused byte in the given DER element.
|
||
|
|
|
||
|
|
DER INTEGERs are decoded into Python integers. Any other DER
|
||
|
|
element is not decoded. Its validity is not checked.
|
||
|
|
|
||
|
|
Raises a ValueError exception if the DER element is not a
|
||
|
|
valid DER SEQUENCE.
|
||
|
|
Raises an IndexError exception if the DER element is too short.
|
||
|
|
"""
|
||
|
|
|
||
|
|
self._seq = []
|
||
|
|
try:
|
||
|
|
tlvLength = DerObject.decode(self, derEle, noLeftOvers)
|
||
|
|
if self.typeTag!=self.typeTags['SEQUENCE']:
|
||
|
|
raise ValueError("Not a DER SEQUENCE.")
|
||
|
|
# Scan one TLV at once
|
||
|
|
idx = 0
|
||
|
|
while idx<len(self.payload):
|
||
|
|
typeTag = bord(self.payload[idx])
|
||
|
|
if typeTag==self.typeTags['INTEGER']:
|
||
|
|
newInteger = DerInteger()
|
||
|
|
idx += newInteger.decode(self.payload[idx:])
|
||
|
|
self._seq.append(newInteger.value)
|
||
|
|
else:
|
||
|
|
itemLen,itemIdx = self._decodeLen(idx+1,self.payload)
|
||
|
|
self._seq.append(self.payload[idx:itemIdx+itemLen])
|
||
|
|
idx = itemIdx + itemLen
|
||
|
|
except IndexError:
|
||
|
|
raise ValueError("Not a valid DER SEQUENCE.")
|
||
|
|
return tlvLength
|
||
|
|
|
||
|
|
class DerOctetString(DerObject):
|
||
|
|
def __init__(self, value = b('')):
|
||
|
|
DerObject.__init__(self, 'OCTET STRING')
|
||
|
|
self.payload = value
|
||
|
|
|
||
|
|
def decode(self, derEle, noLeftOvers=0):
|
||
|
|
p = DerObject.decode(derEle, noLeftOvers)
|
||
|
|
if not self.isType("OCTET STRING"):
|
||
|
|
raise ValueError("Not a valid OCTET STRING.")
|
||
|
|
return p
|
||
|
|
|
||
|
|
class DerNull(DerObject):
|
||
|
|
def __init__(self):
|
||
|
|
DerObject.__init__(self, 'NULL')
|
||
|
|
|
||
|
|
class DerObjectId(DerObject):
|
||
|
|
def __init__(self):
|
||
|
|
DerObject.__init__(self, 'OBJECT IDENTIFIER')
|
||
|
|
|
||
|
|
def decode(self, derEle, noLeftOvers=0):
|
||
|
|
p = DerObject.decode(derEle, noLeftOvers)
|
||
|
|
if not self.isType("OBJECT IDENTIFIER"):
|
||
|
|
raise ValueError("Not a valid OBJECT IDENTIFIER.")
|
||
|
|
return p
|
||
|
|
|
||
|
|
def isInt(x):
|
||
|
|
test = 0
|
||
|
|
try:
|
||
|
|
test += x
|
||
|
|
except TypeError:
|
||
|
|
return 0
|
||
|
|
return 1
|
||
|
|
|