94 lines
2.7 KiB
Python
94 lines
2.7 KiB
Python
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"""Classes for reading/writing binary data (such as TLS records)."""
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from compat import *
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class Writer:
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def __init__(self, length=0):
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#If length is zero, then this is just a "trial run" to determine length
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self.index = 0
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self.bytes = createByteArrayZeros(length)
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def add(self, x, length):
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if self.bytes:
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newIndex = self.index+length-1
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while newIndex >= self.index:
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self.bytes[newIndex] = x & 0xFF
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x >>= 8
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newIndex -= 1
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self.index += length
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def addFixSeq(self, seq, length):
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if self.bytes:
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for e in seq:
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self.add(e, length)
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else:
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self.index += len(seq)*length
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def addVarSeq(self, seq, length, lengthLength):
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if self.bytes:
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self.add(len(seq)*length, lengthLength)
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for e in seq:
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self.add(e, length)
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else:
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self.index += lengthLength + (len(seq)*length)
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class Parser:
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def __init__(self, bytes):
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self.bytes = bytes
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self.index = 0
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def get(self, length):
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if self.index + length > len(self.bytes):
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raise SyntaxError()
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x = 0
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for count in range(length):
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x <<= 8
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x |= self.bytes[self.index]
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self.index += 1
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return x
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def getFixBytes(self, lengthBytes):
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bytes = self.bytes[self.index : self.index+lengthBytes]
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self.index += lengthBytes
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return bytes
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def getVarBytes(self, lengthLength):
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lengthBytes = self.get(lengthLength)
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return self.getFixBytes(lengthBytes)
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def getFixList(self, length, lengthList):
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l = [0] * lengthList
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for x in range(lengthList):
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l[x] = self.get(length)
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return l
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def getVarList(self, length, lengthLength):
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lengthList = self.get(lengthLength)
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if lengthList % length != 0:
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raise SyntaxError()
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lengthList = int(lengthList/length)
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l = [0] * lengthList
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for x in range(lengthList):
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l[x] = self.get(length)
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return l
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def startLengthCheck(self, lengthLength):
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self.lengthCheck = self.get(lengthLength)
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self.indexCheck = self.index
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def setLengthCheck(self, length):
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self.lengthCheck = length
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self.indexCheck = self.index
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def stopLengthCheck(self):
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if (self.index - self.indexCheck) != self.lengthCheck:
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raise SyntaxError()
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def atLengthCheck(self):
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if (self.index - self.indexCheck) < self.lengthCheck:
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return False
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elif (self.index - self.indexCheck) == self.lengthCheck:
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return True
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else:
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raise SyntaxError()
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