# -*- coding: UTF-8 -*-

# Copyright (c) 2010 - 2014, Pascal Volk

# See COPYING for distribution information.

"""

    VirtualMailManager.password

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~

    VirtualMailManager's password module to generate password hashes from

    passwords or random passwords. This module provides following

    functions:

        hashed_password = pwhash(password[, scheme][, user])

        random_password = randompw()

        scheme, encoding = verify_scheme(scheme)

        schemes, encodings = list_schemes()

"""

import hashlib

from base64 import b64encode

from binascii import b2a_hex

from crypt import crypt

from random import SystemRandom

from subprocess import Popen, PIPE

from VirtualMailManager import ENCODING

from VirtualMailManager.emailaddress import EmailAddress

from VirtualMailManager.common import get_unicode, version_str

from VirtualMailManager.constants import VMM_ERROR

from VirtualMailManager.errors import VMMError

SALTCHARS = './0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

PASSWDCHARS = '._-+#*23456789abcdefghikmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'

DEFAULT_B64 = (None, 'B64', 'BASE64')

DEFAULT_HEX = (None, 'HEX')

CRYPT_ID_MD5 = 1

CRYPT_ID_BLF = '2a'

CRYPT_ID_SHA256 = 5

CRYPT_ID_SHA512 = 6

CRYPT_SALT_LEN = 2

CRYPT_BLF_ROUNDS_MIN = 4

CRYPT_BLF_ROUNDS_MAX = 31

CRYPT_BLF_SALT_LEN = 22

CRYPT_MD5_SALT_LEN = 8

CRYPT_SHA2_ROUNDS_DEFAULT = 5000

CRYPT_SHA2_ROUNDS_MIN = 1000

CRYPT_SHA2_ROUNDS_MAX = 999999999

CRYPT_SHA2_SALT_LEN = 16

SALTED_ALGO_SALT_LEN = 4

_ = lambda msg: msg

cfg_dget = lambda option: None

_sys_rand = SystemRandom()

_choice = _sys_rand.choice

_get_salt = lambda s_len: ''.join(_choice(SALTCHARS) for x in range(s_len))

def _dovecotpw(password, scheme, encoding):

    """Communicates with dovecotpw (Dovecot 2.0: `doveadm pw`) and returns

    the hashed password: {scheme[.encoding]}hash

    """

    if encoding:

        scheme = '.'.join((scheme, encoding))

    cmd_args = [cfg_dget('bin.dovecotpw'), '-s', scheme, '-p',

                get_unicode(password)]

    if cfg_dget('misc.dovecot_version') >= 0x20000a01:

        cmd_args.insert(1, 'pw')

    process = Popen(cmd_args, stdout=PIPE, stderr=PIPE)

    stdout, stderr = process.communicate()

    if process.returncode:

        raise VMMError(stderr.strip().decode(ENCODING), VMM_ERROR)

    hashed = stdout.strip().decode(ENCODING)

    if not hashed.startswith('{%s}' % scheme):

        raise VMMError('Unexpected result from %s: %s' %

                       (cfg_dget('bin.dovecotpw'), hashed), VMM_ERROR)

    return hashed

def _md4_new():

    """Returns an new MD4-hash object if supported by the hashlib -

    otherwise `None`.

    """

    try:

        return hashlib.new('md4')

    except ValueError as err:

        if err.args[0].startswith('unsupported hash type'):

            return None

        else:

            raise

def _format_digest(digest, scheme, encoding):

    """Formats the arguments to a string: {scheme[.encoding]}digest."""

    if not encoding:

        return '{%s}%s' % (scheme, digest)

    return '{%s.%s}%s' % (scheme, encoding, digest)

def _clear_hash(password, scheme, encoding):

    """Generates a (encoded) CLEARTEXT/PLAIN 'hash'."""

    password = password.decode(ENCODING)

    if encoding:

        if encoding == 'HEX':

            password = b2a_hex(password.encode()).decode()

        else:

            password = b64encode(password.encode()).decode()

        return _format_digest(password, scheme, encoding)

    return '{%s}%s' % (scheme, password)

def _get_crypt_blowfish_salt():

    """Generates a salt for Blowfish crypt."""

    rounds = cfg_dget('misc.crypt_blowfish_rounds')

    if rounds < CRYPT_BLF_ROUNDS_MIN:

        rounds = CRYPT_BLF_ROUNDS_MIN

    elif rounds > CRYPT_BLF_ROUNDS_MAX:

        rounds = CRYPT_BLF_ROUNDS_MAX

    return '$%s$%02d$%s' % (CRYPT_ID_BLF, rounds,

                            _get_salt(CRYPT_BLF_SALT_LEN))

def _get_crypt_sha2_salt(crypt_id):

    """Generates a salt for crypt using the SHA-256 or SHA-512 encryption

    method.

    *crypt_id* must be either `5` (SHA-256) or `6` (SHA-512).

    """

    assert crypt_id in (CRYPT_ID_SHA256, CRYPT_ID_SHA512), 'invalid crypt ' \

           'id: %r' % crypt_id

    if crypt_id is CRYPT_ID_SHA512:

        rounds = cfg_dget('misc.crypt_sha512_rounds')

    else:

        rounds = cfg_dget('misc.crypt_sha256_rounds')

    if rounds < CRYPT_SHA2_ROUNDS_MIN:

        rounds = CRYPT_SHA2_ROUNDS_MIN

    elif rounds > CRYPT_SHA2_ROUNDS_MAX:

        rounds = CRYPT_SHA2_ROUNDS_MAX

    if rounds == CRYPT_SHA2_ROUNDS_DEFAULT:

        return '$%d$%s' % (crypt_id, _get_salt(CRYPT_SHA2_SALT_LEN))

    return '$%d$rounds=%d$%s' % (crypt_id, rounds,

                                 _get_salt(CRYPT_SHA2_SALT_LEN))

def _crypt_hash(password, scheme, encoding):

    """Generates (encoded) CRYPT/MD5/{BLF,MD5,SHA{256,512}}-CRYPT hashes."""

    if scheme == 'CRYPT':

        salt = _get_salt(CRYPT_SALT_LEN)

    elif scheme == 'BLF-CRYPT':

        salt = _get_crypt_blowfish_salt()

    elif scheme in ('MD5-CRYPT', 'MD5'):

        salt = '$%d$%s' % (CRYPT_ID_MD5, _get_salt(CRYPT_MD5_SALT_LEN))

    elif scheme == 'SHA256-CRYPT':

        salt = _get_crypt_sha2_salt(CRYPT_ID_SHA256)

    else:

        salt = _get_crypt_sha2_salt(CRYPT_ID_SHA512)

    encrypted = crypt(password.decode(ENCODING), salt)

    if encoding:

        if encoding == 'HEX':

            encrypted = b2a_hex(encrypted.encode()).decode()

        else:

            encrypted = b64encode(encrypted.encode()).decode()

    if scheme in ('BLF-CRYPT', 'SHA256-CRYPT', 'SHA512-CRYPT') and \

       cfg_dget('misc.dovecot_version') < 0x20000b06:

        scheme = 'CRYPT'

    return _format_digest(encrypted, scheme, encoding)

def _md4_hash(password, scheme, encoding):

    """Generates encoded PLAIN-MD4 hashes."""

    md4 = _md4_new()

    if md4:

        md4.update(password)

        if encoding in DEFAULT_HEX:

            digest = md4.hexdigest()

        else:

            digest = b64encode(md4.digest()).decode()

        return _format_digest(digest, scheme, encoding)

    return _dovecotpw(password, scheme, encoding)

def _md5_hash(password, scheme, encoding, user=None):

    """Generates DIGEST-MD5 aka PLAIN-MD5 and LDAP-MD5 hashes."""

    md5 = hashlib.md5()

    if scheme == 'DIGEST-MD5':

        md5.update(user.localpart.encode() + b':' +

                   user.domainname.encode() + b':')

    md5.update(password)

    if (scheme in ('PLAIN-MD5', 'DIGEST-MD5') and encoding in DEFAULT_HEX) or \

       (scheme == 'LDAP-MD5' and encoding == 'HEX'):

        digest = md5.hexdigest()

    else:

        digest = b64encode(md5.digest()).decode()

    return _format_digest(digest, scheme, encoding)

def _ntlm_hash(password, scheme, encoding):

    """Generates NTLM hashes."""

    md4 = _md4_new()

    if md4:

        password = b''.join(bytes(x)

                            for x in zip(password, bytes(len(password))))

        md4.update(password)

        if encoding in DEFAULT_HEX:

            digest = md4.hexdigest()

        else:

            digest = b64encode(md4.digest()).decode()

        return _format_digest(digest, scheme, encoding)

    return _dovecotpw(password, scheme, encoding)

def _sha1_hash(password, scheme, encoding):

    """Generates SHA1 aka SHA hashes."""

    sha1 = hashlib.sha1(password)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha1.digest()).decode()

    else:

        digest = sha1.hexdigest()

    return _format_digest(digest, scheme, encoding)

def _sha256_hash(password, scheme, encoding):

    """Generates SHA256 hashes."""

    sha256 = hashlib.sha256(password)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha256.digest()).decode()

    else:

        digest = sha256.hexdigest()

    return _format_digest(digest, scheme, encoding)

def _sha512_hash(password, scheme, encoding):

    """Generates SHA512 hashes."""

    sha512 = hashlib.sha512(password)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha512.digest()).decode()

    else:

        digest = sha512.hexdigest()

    return _format_digest(digest, scheme, encoding)

def _smd5_hash(password, scheme, encoding):

    """Generates SMD5 (salted PLAIN-MD5) hashes."""

    md5 = hashlib.md5(password)

    salt = _get_salt(SALTED_ALGO_SALT_LEN).encode()

    md5.update(salt)

    if encoding in DEFAULT_B64:

        digest = b64encode(md5.digest() + salt).decode()

    else:

        digest = md5.hexdigest() + b2a_hex(salt).decode()

    return _format_digest(digest, scheme, encoding)

def _ssha1_hash(password, scheme, encoding):

    """Generates SSHA (salted SHA/SHA1) hashes."""

    sha1 = hashlib.sha1(password)

    salt = _get_salt(SALTED_ALGO_SALT_LEN).encode()

    sha1.update(salt)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha1.digest() + salt).decode()

    else:

        digest = sha1.hexdigest() + b2a_hex(salt).decode()

    return _format_digest(digest, scheme, encoding)

def _ssha256_hash(password, scheme, encoding):

    """Generates SSHA256 (salted SHA256) hashes."""

    sha256 = hashlib.sha256(password)

    salt = _get_salt(SALTED_ALGO_SALT_LEN).encode()

    sha256.update(salt)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha256.digest() + salt).decode()

    else:

        digest = sha256.hexdigest() + b2a_hex(salt).decode()

    return _format_digest(digest, scheme, encoding)

def _ssha512_hash(password, scheme, encoding):

    """Generates SSHA512 (salted SHA512) hashes."""

    salt = _get_salt(SALTED_ALGO_SALT_LEN).encode()

    sha512 = hashlib.sha512(password + salt)

    if encoding in DEFAULT_B64:

        digest = b64encode(sha512.digest() + salt).decode()

    else:

        digest = sha512.hexdigest() + b2a_hex(salt).decode()

    return _format_digest(digest, scheme, encoding)

_scheme_info = {

    'CLEAR': (_clear_hash, 0x2010df00),

    'CLEARTEXT': (_clear_hash, 0x10000f00),

    'CRAM-MD5': (_dovecotpw, 0x10000f00),

    'CRYPT': (_crypt_hash, 0x10000f00),

    'DIGEST-MD5': (_md5_hash, 0x10000f00),

    'HMAC-MD5': (_dovecotpw, 0x10000f00),

    'LANMAN': (_dovecotpw, 0x10000f00),

    'LDAP-MD5': (_md5_hash, 0x10000f00),

    'MD5': (_crypt_hash, 0x10000f00),

    'MD5-CRYPT': (_crypt_hash, 0x10000f00),

    'NTLM': (_ntlm_hash, 0x10000f00),

    'OTP': (_dovecotpw, 0x10100a01),

    'PLAIN': (_clear_hash, 0x10000f00),

    'PLAIN-MD4': (_md4_hash, 0x10000f00),

    'PLAIN-MD5': (_md5_hash, 0x10000f00),

    'RPA': (_dovecotpw, 0x10000f00),

    'SCRAM-SHA-1': (_dovecotpw, 0x20200a01),

    'SHA': (_sha1_hash, 0x10000f00),

    'SHA1': (_sha1_hash, 0x10000f00),

    'SHA256': (_sha256_hash, 0x10100a01),

    'SHA512': (_sha512_hash, 0x20000b03),

    'SKEY': (_dovecotpw, 0x10100a01),

    'SMD5': (_smd5_hash, 0x10000f00),

    'SSHA': (_ssha1_hash, 0x10000f00),

    'SSHA256': (_ssha256_hash, 0x10200a04),

    'SSHA512': (_ssha512_hash, 0x20000b03),

}

def list_schemes():

    """Returns the tuple (schemes, encodings).

    `schemes` is an iterator for all supported password schemes (depends on

    the used Dovecot version and features of the libc).

    `encodings` is a tuple with all usable encoding suffixes.

    """

    dcv = cfg_dget('misc.dovecot_version')

    schemes = (k for (k, v) in _scheme_info.items() if v[1] <= dcv)

    encodings = ('.B64', '.BASE64', '.HEX')

    return schemes, encodings

def verify_scheme(scheme):

    """Checks if the password scheme *scheme* is known and supported by the

    configured `misc.dovecot_version`.

    The *scheme* maybe a password scheme's name (e.g.: 'PLAIN') or a scheme

    name with a encoding suffix (e.g. 'PLAIN.BASE64').  If the scheme is

    known and supported by the used Dovecot version,

    a tuple ``(scheme, encoding)`` will be returned.

    The `encoding` in the tuple may be `None`.

    Raises a `VMMError` if the password scheme:

      * is unknown

      * depends on a newer Dovecot version

      * has a unknown encoding suffix

    """

    assert isinstance(scheme, str), 'Not a str: {!r}'.format(scheme)

    scheme_encoding = scheme.upper().split('.')

    scheme = scheme_encoding[0]

    if scheme not in _scheme_info:

        raise VMMError(_("Unsupported password scheme: '%s'") % scheme,

                       VMM_ERROR)

    if cfg_dget('misc.dovecot_version') < _scheme_info[scheme][1]:

        raise VMMError(_("The password scheme '%(scheme)s' requires Dovecot "

                         ">= v%(version)s.") % {'scheme': scheme,

                       'version': version_str(_scheme_info[scheme][1])},

                       VMM_ERROR)

    if len(scheme_encoding) > 1:

        if scheme_encoding[1] not in ('B64', 'BASE64', 'HEX'):

            raise VMMError(_("Unsupported password encoding: '%s'") %

                           scheme_encoding[1], VMM_ERROR)

        encoding = scheme_encoding[1]

    else:

        encoding = None

    return scheme, encoding

def pwhash(password, scheme=None, user=None):

    """Generates a password hash from the plain text *password* string.

    If no *scheme* is given the password scheme from the configuration will

    be used for the hash generation.  When 'DIGEST-MD5' is used as scheme,

    also an EmailAddress instance must be given as *user* argument.

    """

    if not isinstance(password, str):

        raise TypeError('Password is not a string: %r' % password)

    password = password.encode(ENCODING).strip()

    if not password:

        raise ValueError("Could not accept empty password.")