#!/usr/bin/env python
#
# pyapr1 - A Python implementation of the APR1 algorithm
#
# Copyright (c) 2015, Tilman Blumenbach
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this
#   list of conditions and the following disclaimer.
#
# * Redistributions in binary form must reproduce the above copyright notice,
#   this list of conditions and the following disclaimer in the documentation
#   and/or other materials provided with the distribution.
#
# * Neither the name of pyapr1 nor the names of its
#   contributors may be used to endorse or promote products derived from
#   this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# The to64() and hash_apr1() functions are based on code from the Apache Portable
# Runtime Utility Library (namely, on the two functions to64() and
# apr_md5_encode() from the file crypto/apr_md5.c). The licenses for that original
# material are included below:
#
# ============================================================================
#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
#
#
# The apr_md5_encode() routine uses much code obtained from the FreeBSD 3.0
# MD5 crypt() function, which is licenced as follows:
# ----------------------------------------------------------------------------
# "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
# ----------------------------------------------------------------------------
#
# ============================================================================

from hashlib import md5


def to64(data, n_out):
    chars = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
    out = ""

    for i in range(n_out):
        out += chars[data & 0x3f]
        data >>= 6

    return out


def mkint(data, *indexes):
    r = 0
    for i, idx in enumerate(indexes):
        r |= data[idx] << 8 * (len(indexes) - i - 1)

    return r


def hash_apr1(salt, password):
    sb = bytes(salt, "ascii")
    pb = bytes(password, "iso-8859-1")
    ph = md5()

    # First, the password.
    ph.update(pb)
    # Then, the magic string.
    ph.update(b"$apr1$")
    # Then, the salt.
    ph.update(sb)

    # Weird stuff.
    sandwich = md5(pb + sb + pb).digest()
    ndig, nrem = divmod(len(pb), ph.digest_size)
    for n in ndig * [ph.digest_size] + [nrem]:
        ph.update(sandwich[:n])

    # Even more weird stuff.
    i = len(pb)
    while i:
        if i & 1:
            ph.update(b'\0')
        else:
            ph.update(pb[:1])

        i >>= 1

    final = ph.digest()
    for i in range(1000):
        maelstrom = md5()

        if i & 1:
            maelstrom.update(pb)
        else:
            maelstrom.update(final)

        if i % 3:
            maelstrom.update(sb)

        if i % 7:
            maelstrom.update(pb)

        if i & 1:
            maelstrom.update(final)
        else:
            maelstrom.update(pb)

        final = maelstrom.digest()

    pw_ascii = to64(mkint(final, 0, 6, 12), 4) + \
               to64(mkint(final, 1, 7, 13), 4) + \
               to64(mkint(final, 2, 8, 14), 4) + \
               to64(mkint(final, 3, 9, 15), 4) + \
               to64(mkint(final, 4, 10, 5), 4) + \
               to64(mkint(final, 11), 2)

    return "$apr1$%s$%s" % (salt, pw_ascii)