/usr/share/pyshared/tlslite/utils/ASN1Parser.py is in python-tlslite 0.3.8-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | """Class for parsing ASN.1"""
from compat import *
from codec import *
#Takes a byte array which has a DER TLV field at its head
class ASN1Parser:
def __init__(self, bytes):
p = Parser(bytes)
p.get(1) #skip Type
#Get Length
self.length = self._getASN1Length(p)
#Get Value
self.value = p.getFixBytes(self.length)
#Assuming this is a sequence...
def getChild(self, which):
p = Parser(self.value)
for x in range(which+1):
markIndex = p.index
p.get(1) #skip Type
length = self._getASN1Length(p)
p.getFixBytes(length)
return ASN1Parser(p.bytes[markIndex : p.index])
#Decode the ASN.1 DER length field
def _getASN1Length(self, p):
firstLength = p.get(1)
if firstLength<=127:
return firstLength
else:
lengthLength = firstLength & 0x7F
return p.get(lengthLength)
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