# md5crypt.py

#

# 0423.2000 by michal wallace http://www.sabren.com/

# based on perl's Crypt::PasswdMD5 by Luis Munoz (lem@cantv.net)

# based on /usr/src/libcrypt/crypt.c from FreeBSD 2.2.5-RELEASE

#

# MANY THANKS TO

#

#  Carey Evans - http://home.clear.net.nz/pages/c.evans/

#  Dennis Marti - http://users.starpower.net/marti1/

#

#  For the patches that got this thing working!

#

# modification by logilab:

# * remove usage of the string module

# * don't include the magic string in the output string

#   for true crypt.crypt compatibility

# * use hashlib module instead of md5

#########################################################

"""md5crypt.py - Provides interoperable MD5-based crypt() function

SYNOPSIS

        import md5crypt.py

        cryptedpassword = md5crypt.md5crypt(password, salt);

DESCRIPTION

unix_md5_crypt() provides a crypt()-compatible interface to the

rather new MD5-based crypt() function found in modern operating systems.

It's based on the implementation found on FreeBSD 2.2.[56]-RELEASE and

contains the following license in it:

 "THE BEER-WARE LICENSE" (Revision 42):

 <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you

 can do whatever you want with this stuff. If we meet some day, and you think

 this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp

"""

MAGIC = b'$1$'                        # Magic string

ITOA64 = b"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

from hashlib import md5 # pylint: disable=E0611

def to64 (v, n):

    ret = bytearray()

    while (n - 1 >= 0):

        n = n - 1

        ret.append(ITOA64[v & 0x3f])

        v = v >> 6

    return ret

def crypt(pw, salt):

    if isinstance(pw, str):

        pw = pw.encode('utf-8')

    if isinstance(salt, str):

        salt = salt.encode('ascii')

    # Take care of the magic string if present

    if salt.startswith(MAGIC):

        salt = salt[len(MAGIC):]

    # salt can have up to 8 characters:

    salt = salt.split(b'$', 1)[0]

    salt = salt[:8]

    ctx = pw + MAGIC + salt

    final = md5(pw + salt + pw).digest()

    for pl in range(len(pw), 0, -16):

        if pl > 16:

            ctx = ctx + final[:16]

        else:

            ctx = ctx + final[:pl]

    # Now the 'weird' xform (??)

    i = len(pw)

    while i:

        if i & 1:

            ctx = ctx + b'\0'  #if ($i & 1) { $ctx->add(pack("C", 0)); }

        else:

            ctx = ctx + pw[0]

        i = i >> 1

    final = md5(ctx).digest()

    # The following is supposed to make

    # things run slower.

    # my question: WTF???

    for i in range(1000):

        ctx1 = b''

        if i & 1:

            ctx1 = ctx1 + pw

        else:

            ctx1 = ctx1 + final[:16]

        if i % 3:

            ctx1 = ctx1 + salt

        if i % 7:

            ctx1 = ctx1 + pw

        if i & 1:

            ctx1 = ctx1 + final[:16]

        else:

            ctx1 = ctx1 + pw

        final = md5(ctx1).digest()

    # Final xform

    passwd = b''

    passwd += to64((final[0] << 16)

                   |(final[6] << 8)

                   |(final[12]),4)

    passwd += to64((final[1] << 16)

                   |(final[7] << 8)

                   |(final[13]), 4)

    passwd += to64((final[2] << 16)

                   |(final[8] << 8)

                   |(final[14]), 4)

    passwd += to64((final[3] << 16)

                   |(final[9] << 8)

                   |(final[15]), 4)

    passwd += to64((final[4] << 16)

                   |(final[10] << 8)

                   |(final[5]), 4)

    passwd += to64((final[11]), 2)

    return passwd