Python - How can I avoid b"\n" being written in a text file with "wb" causing a line break?

Question

Here is my case:

# Small hashing script example
import hashlib
import os

def original_pass(Password):
    salt = os.urandom(64)
    hashed = hashlib.pbkdf2_hmac("sha512", Password.encode(), salt, 300000, dklen = 124)
    with open("Hash.txt", "wb") as file:
        file.write(salt + b"\n" + hashed)
        file.close()

def check_pass(New_Pass):
    with open("Hash.txt", "rb") as file:
            f = file.readlines()
            print (f)
            check_hash = hashlib.pbkdf2_hmac("sha512", New_Pass.encode(), f[0].strip(b"\n"), 300000, dklen = 124)   
            file.close()     
    if check_hash == f[1]:
        return True
    else:
        return False

original_pass("Password")
print (check_pass("Password"))

My problem is that occasionally the hash will contain characters such as \n. E.G. b"x004\n4\no5". This line gets split into b"x004\n", b"4\no5". This causes errors when I try to read things like the salt, since it may be split up into multiple pieces. Is there any way of avoiding it being read like that, or just stopping it from writing it that way?

To address the duplicate remark

I am dealing specifically with byte strings here and not regular strings. Both are a distinct data type, moreso in python 3 (the version I'm using) as seen here: What is the difference between a string and a byte string?. This distinction means that certain string methods such as .encode() don't work on byte strings. Thus there is a clear difference in the data types I'm dealing with and how they are manipulated, etc...

You could encode your hashes in a representation that doesn't use the `b'\n'` byte - base64, for example - or you could stop using line breaks to determine where each hash ends. — user2357112, Aug 27 '17 at 23:40
Possible duplicate of [casting raw strings python](https://stackoverflow.com/questions/2428117/casting-raw-strings-python) — Rajan Chauhan, Aug 27 '17 at 23:40
Well the line is being broken into a new line when "\n" pops up in the file, like it would in a normal string, except since it occurs randomly in the hash it's causes unwanted line breaks within the text file. — Maximillion Billiony, Aug 27 '17 at 23:41
@RajanChauhan I'm dealing with bytes so there is a distinction. — Maximillion Billiony, Aug 27 '17 at 23:43
@user2357112 I have decided to use your solution using base64, it all works perfectly now, thank you! — Maximillion Billiony, Aug 27 '17 at 23:57
@jasonharper True, I understand what you mean. I just meant a file where binary was being written. — Maximillion Billiony, Aug 28 '17 at 00:02
If using Python 3.5 or later, byte strings have a `.hex()` method. You could write your binary strings to a text file. Read them back and convert back to byte strings with `bytes.fromhex(...)`. — Mark Tolonen, Aug 28 '17 at 00:18
The salt you're creating is a fixed length, so you don't need the newline delimiter at all. Just read the first 64 bytes as the salt and the rest as the hash. — Blckknght, Aug 28 '17 at 00:39

score 1 · Accepted Answer · answered Aug 28 '17 at 00:51

Based on @Blckknght comment, code using knowledge of fixed length salt:

import hashlib
import os

SALT_LEN = 64

def hash(password,salt):
    return hashlib.pbkdf2_hmac('sha512',password.encode(),salt,300000,dklen=124)

def original_pass(password):
    salt = os.urandom(SALT_LEN)
    hashed = hash(password,salt)    
    with open('hash.bin','wb') as file:
        file.write(salt + hashed)

def check_pass(password):
    with open('hash.bin','rb') as file:
        data = file.read()
    salt,hashed = data[:SALT_LEN],data[SALT_LEN:]
    check_hash = hash(password,salt)    
    return check_hash == hashed

original_pass('Password')
print(check_pass('Password'))

Python - How can I avoid b"\n" being written in a text file with "wb" causing a line break?

1 Answers1