#!/usr/bin/env python

# Copyright (c) 2014, Jan Varho
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""Scrypt implementation that calls into system libsodium"""


import base64
import ctypes, ctypes.util
from ctypes import c_char_p, c_size_t, c_uint64, c_uint32, c_void_p
import hashlib, hmac
import numbers
import platform
import struct
import sys

from . import mcf as mcf_mod
from .common import *

if platform.python_implementation() == 'PyPy':
    from . import pypyscrypt_inline as scr_mod
else:
    from . import pylibsodium_salsa as scr_mod


def _get_libsodium():
    '''
    Locate the nacl c libs to use
    '''

    __SONAMES = (13, 10, 5, 4)
    # Import libsodium from system
    sys_sodium = ctypes.util.find_library('sodium')
    if sys_sodium is None:
        sys_sodium = ctypes.util.find_library('libsodium')

    if sys_sodium:
        return ctypes.CDLL(sys_sodium)

    # Import from local path
    if sys.platform.startswith('win'):

        try:
            return ctypes.cdll.LoadLibrary('libsodium')
        except OSError:
            pass
        for soname_ver in __SONAMES:
            try:
                return ctypes.cdll.LoadLibrary(
                    'libsodium-{0}'.format(soname_ver)
                )
            except OSError:
                pass
    elif sys.platform.startswith('darwin'):
        try:
            return ctypes.cdll.LoadLibrary('libsodium.dylib')
        except OSError:
            pass
    else:
        try:
            return ctypes.cdll.LoadLibrary('libsodium.so')
        except OSError:
            pass

        for soname_ver in __SONAMES:
            try:
                return ctypes.cdll.LoadLibrary(
                    'libsodium.so.{0}'.format(soname_ver)
                )
            except OSError:
                pass


_lib = _get_libsodium()
if _lib is None:
    raise ImportError('Unable to load libsodium')

try:
    _scrypt_ll = _lib.crypto_pwhash_scryptsalsa208sha256_ll
    _scrypt_ll.argtypes = [
        c_void_p,  # passwd
        c_size_t,  # passwdlen
        c_void_p,  # salt
        c_size_t,  # saltlen
        c_uint64,  # N
        c_uint32,  # r
        c_uint32,  # p
        c_void_p,  # buf
        c_size_t,  # buflen
    ]
except AttributeError:
    _scrypt_ll = None

try:
    _scrypt = _lib.crypto_pwhash_scryptsalsa208sha256
    _scrypt_str = _lib.crypto_pwhash_scryptsalsa208sha256_str
    _scrypt_str_chk = _lib.crypto_pwhash_scryptsalsa208sha256_str_verify
    _scrypt_str_bytes = _lib.crypto_pwhash_scryptsalsa208sha256_strbytes()
    _scrypt_salt = _lib.crypto_pwhash_scryptsalsa208sha256_saltbytes()
    if _scrypt_str_bytes != 102 and not _scrypt_ll:
        raise ImportError('Incompatible libsodium: ' + _lib_soname)
except AttributeError:
    try:
        _scrypt = _lib.crypto_pwhash_scryptxsalsa208sha256
        _scrypt_str = _lib.crypto_pwhash_scryptxsalsa208sha256_str
        _scrypt_str_chk = _lib.crypto_pwhash_scryptxsalsa208sha256_str_verify
        _scrypt_str_bytes = _lib.crypto_pwhash_scryptxsalsa208sha256_strbytes()
        _scrypt_salt = _lib.crypto_pwhash_scryptxsalsa208sha256_saltbytes
        _scrypt_salt = _scrypt_salt()
        if _scrypt_str_bytes != 102 and not _scrypt_ll:
            raise ImportError('Incompatible libsodium: ' + _lib_soname)
    except AttributeError:
        if not _scrypt_ll:
            raise ImportError('Incompatible libsodium: ' + _lib_soname)

_scrypt.argtypes = [
    c_void_p,  # out
    c_uint64,  # outlen
    c_void_p,  # passwd
    c_uint64,  # passwdlen
    c_void_p,  # salt
    c_uint64,  # opslimit
    c_size_t,  # memlimit
]

_scrypt_str.argtypes = [
    c_void_p,  # out (102 bytes)
    c_void_p,  # passwd
    c_uint64,  # passwdlen
    c_uint64,  # opslimit
    c_size_t,  # memlimit
]

_scrypt_str_chk.argtypes = [
    c_char_p,  # str (102 bytes)
    c_void_p,  # passwd
    c_uint64,  # passwdlen
]


def scrypt(password, salt, N=SCRYPT_N, r=SCRYPT_r, p=SCRYPT_p, olen=64):
    """Returns a key derived using the scrypt key-derivarion function

    N must be a power of two larger than 1 but no larger than 2 ** 63 (insane)
    r and p must be positive numbers such that r * p < 2 ** 30

    The default values are:
    N -- 2**14 (~16k)
    r -- 8
    p -- 1

    Memory usage is proportional to N*r. Defaults require about 16 MiB.
    Time taken is proportional to N*p. Defaults take <100ms of a recent x86.

    The last one differs from libscrypt defaults, but matches the 'interactive'
    work factor from the original paper. For long term storage where runtime of
    key derivation is not a problem, you could use 16 as in libscrypt or better
    yet increase N if memory is plentiful.
    """
    check_args(password, salt, N, r, p, olen)

    if _scrypt_ll:
        out = ctypes.create_string_buffer(olen)
        if _scrypt_ll(password, len(password), salt, len(salt),
                      N, r, p, out, olen):
            raise ValueError
        return out.raw

    if len(salt) != _scrypt_salt or r != 8 or (p & (p - 1)) or (N*p <= 512):
        return scr_mod.scrypt(password, salt, N, r, p, olen)

    s = next(i for i in range(1, 64) if 2**i == N)
    t = next(i for i in range(0, 30) if 2**i == p)
    m = 2**(10 + s)
    o = 2**(5 + t + s)
    if s > 53 or t + s > 58:
        raise ValueError
    out = ctypes.create_string_buffer(olen)
    if _scrypt(out, olen, password, len(password), salt, o, m) != 0:
        raise ValueError
    return out.raw


def scrypt_mcf(password, salt=None, N=SCRYPT_N, r=SCRYPT_r, p=SCRYPT_p,
               prefix=SCRYPT_MCF_PREFIX_DEFAULT):
    """Derives a Modular Crypt Format hash using the scrypt KDF

    Parameter space is smaller than for scrypt():
    N must be a power of two larger than 1 but no larger than 2 ** 31
    r and p must be positive numbers between 1 and 255
    Salt must be a byte string 1-16 bytes long.

    If no salt is given, a random salt of 128+ bits is used. (Recommended.)
    """
    if N < 2 or (N & (N - 1)):
        raise ValueError('scrypt N must be a power of 2 greater than 1')
    if p > 255 or p < 1:
        raise ValueError('scrypt_mcf p out of range [1,255]')
    if N > 2**31:
        raise ValueError('scrypt_mcf N out of range [2,2**31]')

    if (salt is not None or r != 8 or (p & (p - 1)) or (N*p <= 512) or
        prefix not in (SCRYPT_MCF_PREFIX_7, SCRYPT_MCF_PREFIX_s1,
                       SCRYPT_MCF_PREFIX_ANY) or
        _scrypt_ll):
        return mcf_mod.scrypt_mcf(scrypt, password, salt, N, r, p, prefix)

    s = next(i for i in range(1, 32) if 2**i == N)
    t = next(i for i in range(0, 8) if 2**i == p)
    m = 2**(10 + s)
    o = 2**(5 + t + s)
    mcf = ctypes.create_string_buffer(102)
    if _scrypt_str(mcf, password, len(password), o, m) != 0:
        return mcf_mod.scrypt_mcf(scrypt, password, salt, N, r, p, prefix)

    if prefix in (SCRYPT_MCF_PREFIX_7, SCRYPT_MCF_PREFIX_ANY):
        return mcf.raw.strip(b'\0')

    _N, _r, _p, salt, hash, olen = mcf_mod._scrypt_mcf_decode_7(mcf.raw[:-1])
    assert _N == N and _r == r and _p == p, (_N, _r, _p, N, r, p, o, m)
    return mcf_mod._scrypt_mcf_encode_s1(N, r, p, salt, hash)


def scrypt_mcf_check(mcf, password):
    """Returns True if the password matches the given MCF hash"""
    if mcf_mod._scrypt_mcf_7_is_standard(mcf) and not _scrypt_ll:
        return _scrypt_str_chk(mcf, password, len(password)) == 0
    return mcf_mod.scrypt_mcf_check(scrypt, mcf, password)


if __name__ == "__main__":
    import sys
    from . import tests
    try:
        from . import pylibscrypt
        scr_mod = pylibscrypt
    except ImportError:
        pass
    tests.run_scrypt_suite(sys.modules[__name__])