#########################################################
# 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
#########################################################
"""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 = '$1$'                        # Magic string
ITOA64 = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

import md5

def to64 (v, n):
    ret = ''
    while (n - 1 >= 0):
        n = n - 1
        ret = ret + ITOA64[v & 0x3f]
        v = v >> 6
    return ret


def crypt(pw, salt, magic=None):
    if magic is None:
        magic = MAGIC
    # Take care of the magic string if present
    if salt[:len(magic)] == magic:
        salt = salt[len(magic):]
    # salt can have up to 8 characters:
    salt = salt.split('$', 1)[0]
    salt = salt[:8]
    ctx = pw + magic + salt
    final = md5.md5(pw + salt + pw).digest()
    for pl in xrange(len(pw), 0, -16):
        if pl > 16:
            ctx = ctx + final[:16]
        else:
            ctx = ctx + final[:pl]
    # Now the 'weird' xform (??)
    i = len(pw)
    while i:
        if i & 1:
            ctx = ctx + chr(0)  #if ($i & 1) { $ctx->add(pack("C", 0)); }
        else:
            ctx = ctx + pw[0]
        i = i >> 1
    final = md5.md5(ctx).digest()
    # The following is supposed to make
    # things run slower. 
    # my question: WTF???
    for i in xrange(1000):
        ctx1 = ''
        if i & 1:
            ctx1 = ctx1 + pw
        else:
            ctx1 = ctx1 + final[:16]
        if i % 3:
            ctx1 = ctx1 + salt
        if i % 7:
            ctx1 = ctx1 + pw
        if i & 1:
            ctx1 = ctx1 + final[:16]
        else:
            ctx1 = ctx1 + pw
        final = md5.md5(ctx1).digest()
    # Final xform
    passwd = ''
    passwd = passwd + to64((int(ord(final[0])) << 16)
                           |(int(ord(final[6])) << 8)
                           |(int(ord(final[12]))),4)
    passwd = passwd + to64((int(ord(final[1])) << 16)
                           |(int(ord(final[7])) << 8)
                           |(int(ord(final[13]))), 4)
    passwd = passwd + to64((int(ord(final[2])) << 16)
                           |(int(ord(final[8])) << 8)
                           |(int(ord(final[14]))), 4)
    passwd = passwd + to64((int(ord(final[3])) << 16)
                           |(int(ord(final[9])) << 8)
                           |(int(ord(final[15]))), 4)
    passwd = passwd + to64((int(ord(final[4])) << 16)
                           |(int(ord(final[10])) << 8)
                           |(int(ord(final[5]))), 4)
    passwd = passwd + to64((int(ord(final[11]))), 2)
    return salt + '$' + passwd