NULL mag Issue 07 31 SAUCE record read

Published in

· 26 Dec 2020

  

 

  A simple function in Python3 to get some SAUCE data. It wont retrieve all 
  data as we pad the last 32 bytes and also it will ignore any COMMENTS  
  block. Your homework is to extend it... :p 
   

-- use python3 
#!/usr/bin/python3 

-- import libraries that we need 
import os 
import sys 

-- the struct library is the important stuff here. with it we will get the 
   sauce structure and unpack it to values that we can use. 
import struct 

-- the script needs a filename/path as its first parameter. 
filename = sys.argv[1] 

-- now let's get that sauce data... 
def getsauce(filename): 

    -- open the given file for reading as binary file. 
    f = open(filename, 'rb') 
     
    -- go to the 128th byte before the end of the file, because that's where 
       the sauce data is being stored. 
    f.seek(-128,2) 
     
    -- define the structure that we are going to read. 
    saucestr = "<5s2s35s20s20s8si32x" 
     
    -- calculate the size of the structure 
    sf = struct.calcsize(saucestr) 
     
    -- and read it from the file 
    sauce = f.read(sf) 
    s = struct.unpack(saucestr,sauce) 
     
    -- close the file 
    f.close() 
     
    -- if our variable, contains a SAUCE string, this means the file has  
       sauce data, otherwise it doesn't. 
    if ''.join(str(s[0]).strip("b'")) == "SAUCE": 
        -- return all the sauce data, as a string, as the result of the  
           function 
        return s 
    else: 
        return -1 

-- if successful this will pring the sauce data of the file. 
print(getsauce(filename))   

 
  complete script below. copy/paste into a text file and make it executable. 
   
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#!/usr/bin/python3 

import os 
import struct 
import sys 

filename = sys.argv[1] 

def getsauce(filename): 
    f = open(filename, 'rb') 
    f.seek(-128,2) 
    saucestr = "<5s2s35s20s20s8si32x" 
    sf = struct.calcsize(saucestr) 
    sauce = f.read(sf) 
    s = struct.unpack(saucestr,sauce) 
    f.close() 
    if ''.join(str(s[0]).strip("b'")) == "SAUCE": 
        return s 
    else: 
        return -1 

print(getsauce(filename)) 

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