Calling argument to function and getting the file hashes

Question

I'm attempting to get the hashes of the file which is the argument supplied. Here is my current code:

import hashlib
import argparse


md5 = hashlib.md5()
sha1 = hashlib.sha1()
sha256 = hashlib.sha256()
BUF_SIZE = 32768

parse = argparse.ArgumentParser()
parse.add_argument("-test", help = 'testing')
args = parse.parse_args()


def hashing(hashThis=args.test):
    with open(hashThis, 'rb') as f:
        while True:
            data = f.read(BUF_SIZE)
            if not data:
                break
        md5.update(data)
        sha1.update(data)
        sha256.update(data)
    #print hashes
    print('MD5: {0}'.format(md5.hexdigest()))   
    print('SHA1: {0}'.format(sha1.hexdigest()))
    print('SHA256: {0}'.format(sha256.hexdigest()))

hashing(hashThis=args.test)

This gives me the following output:

user@user:~/Testing$ python test.py -test test.txt
MD5: d41d8cd98f00b204e9800998ecf8427e
SHA1: da39a3ee5e6b4b0d3255bfef95601890afd80709
SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

The issue is that the hashes given are for an empty file, by using sha256sum of the same file I get

user@user:~/Testing$ sha256sum test.txt
8f434346648f6b96df89dda901c5176b10a6d83961dd3c1ac88b59b2dc327aa4  test.txt

Its not pulling the data from the file, and it works if I use the same code outside of a function. I feel like I'm missing something obvious, but can't figure it out.

Answer 1

You need to be updating the hash objects within the while loop - right now the while loop only exits once 'data' is empty, so all you hash is that empty byte array