c15.py

from pals import utils

a = b"ICE ICE BABY\x04\x04\x04\x04" 
b = b"ICE ICE BABY\x05\x05\x05\x05"
c = b"ICE ICE BABY\x01\x02\x03\x04"

tests = [a, b, c]

for s in tests:
    try:
        utils.unpad(s)
        print('good: {}'.format(s))
    except:
        print('bad:  {}'.format(s))

'''

PKCS#7 padding validation
Write a function that takes a plaintext, determines if it 
has valid PKCS#7 padding, and strips the padding off.

The string:

"ICE ICE BABY\x04\x04\x04\x04"
... has valid padding, and produces the result "ICE ICE BABY".

The string:

"ICE ICE BABY\x05\x05\x05\x05"
... does not have valid padding, nor does:

"ICE ICE BABY\x01\x02\x03\x04"
If you are writing in a language with exceptions, like Python 
or Ruby, make your function throw an exception on bad padding.

Crypto nerds know where we're going with this. Bear with us.
'''