如何在Python中使用ASN1库解码.BER

Question

I have an encoded file with .BER format that I can't decode.

After searching, I got that I need to use ASN1 library to be able to decode this file and to be readable.

Can someone guide me how to decode .BER file using ASN1 library on python?

I have checked online and found that there are some online ASN1 decoder that correctly decode my file. However, I won't be able to use them as I need to decode it on my own not using an online tool. I don't know how to get this tag and value in the script below.

import asn1 import re import os import future Input_directory=open("D:\\Encoded_Nokia.ber","rb")

for lines in Input_directory: decoder = asn1.Decoder() output=decoder.start(lines) tag,output=decoder.read()

Those are the errors i got:

  File "C:\Python34\lib\site-packages\asn1.py", line 421, in read
    value = self._read_value(tag.nr, length)
  File "C:\Python34\lib\site-packages\asn1.py", line 508, in _read_value
    bytes_data = self._read_bytes(length)
  File "C:\Python34\lib\site-packages\asn1.py", line 541, in _read_bytes
    raise Error('Premature end of input.')
asn1.Error: Premature end of input.

Answer 1

BER may use an indefinite length encoding for some constructed data values. The error you got suggests that you passed truncated bytes into the decoder. This means that you should pass the entire content of the decoder like this:

Input_directory=open("D:\Encoded_Nokia.ber","rb")

# reads everything
content = Input_directory.read()
output=decoder.start(content)