#!/usr/bin/env python
#
# Copyright 2015-2015 breakwa11
#
# Licensed 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.

from __future__ import absolute_import, division, print_function, \
    with_statement

import os
import sys
import hashlib
import logging
import binascii
import base64
import time
import datetime
import random
import struct
import zlib
import hmac
import hashlib

import shadowsocks
from shadowsocks import common
from shadowsocks.obfsplugin import plain
from shadowsocks.common import to_bytes, to_str, ord, chr

def create_auth_simple(method):
    return auth_simple(method)

def create_auth_sha1(method):
    return auth_sha1(method)

obfs_map = {
        'auth_simple': (create_auth_simple,),
        'auth_sha1': (create_auth_sha1,),
        'auth_sha1_compatible': (create_auth_sha1,),
}

def match_begin(str1, str2):
    if len(str1) >= len(str2):
        if str1[:len(str2)] == str2:
            return True
    return False

class obfs_verify_data(object):
    def __init__(self):
        pass

class verify_base(plain.plain):
    def __init__(self, method):
        super(verify_base, self).__init__(method)
        self.method = method

    def init_data(self):
        return ''

    def set_server_info(self, server_info):
        self.server_info = server_info

    def client_encode(self, buf):
        return buf

    def client_decode(self, buf):
        return (buf, False)

    def server_encode(self, buf):
        return buf

    def server_decode(self, buf):
        return (buf, True, False)

class client_queue(object):
    def __init__(self, begin_id):
        self.front = begin_id
        self.back = begin_id
        self.alloc = {}
        self.enable = True
        self.last_update = time.time()

    def update(self):
        self.last_update = time.time()

    def is_active(self):
        return time.time() - self.last_update < 60 * 3

    def re_enable(self, connection_id):
        self.enable = True
        self.alloc = {}
        self.front = connection_id
        self.back = connection_id

    def insert(self, connection_id):
        self.update()
        if not self.enable:
            logging.warn('auth_simple: not enable')
            return False
        if connection_id < self.front:
            logging.warn('auth_simple: duplicate id')
            return False
        if not self.is_active():
            self.re_enable(connection_id)
        if connection_id > self.front + 0x4000:
            logging.warn('auth_simple: wrong id')
            return False
        if connection_id in self.alloc:
            logging.warn('auth_simple: duplicate id 2')
            return False
        if self.back <= connection_id:
            self.back = connection_id + 1
        self.alloc[connection_id] = 1
        while (self.front in self.alloc) or self.front + 0x1000 < self.back:
            if self.front in self.alloc:
                del self.alloc[self.front]
            self.front += 1
        return True

class obfs_auth_data(object):
    def __init__(self):
        self.client_id = {}
        self.startup_time = int(time.time() - 30) & 0xFFFFFFFF
        self.local_client_id = b''
        self.connection_id = 0
        self.set_max_client(16) # max active client count

    def update(self, client_id, connection_id):
        if client_id in self.client_id:
            self.client_id[client_id].update()

    def set_max_client(self, max_client):
        self.max_client = max_client
        self.max_buffer = max(self.max_client * 2, 256)

    def insert(self, client_id, connection_id):
        if client_id not in self.client_id or not self.client_id[client_id].enable:
            active = 0
            for c_id in self.client_id:
                if self.client_id[c_id].is_active():
                    active += 1
            if active >= self.max_client:
                logging.warn('auth_simple: max active clients exceeded')
                return False

            if len(self.client_id) < self.max_client:
                if client_id not in self.client_id:
                    self.client_id[client_id] = client_queue(connection_id)
                else:
                    self.client_id[client_id].re_enable(connection_id)
                return self.client_id[client_id].insert(connection_id)
            keys = self.client_id.keys()
            random.shuffle(keys)
            for c_id in keys:
                if not self.client_id[c_id].is_active() and self.client_id[c_id].enable:
                    if len(self.client_id) >= self.max_buffer:
                        del self.client_id[c_id]
                    else:
                        self.client_id[c_id].enable = False
                    if client_id not in self.client_id:
                        self.client_id[client_id] = client_queue(connection_id)
                    else:
                        self.client_id[client_id].re_enable(connection_id)
                    return self.client_id[client_id].insert(connection_id)
            logging.warn('auth_simple: no inactive client [assert]')
            return False
        else:
            return self.client_id[client_id].insert(connection_id)

class auth_simple(verify_base):
    def __init__(self, method):
        super(auth_simple, self).__init__(method)
        self.recv_buf = b''
        self.unit_len = 8100
        self.decrypt_packet_num = 0
        self.raw_trans = False
        self.has_sent_header = False
        self.has_recv_header = False
        self.client_id = 0
        self.connection_id = 0
        self.max_time_dif = 60 * 5 # time dif (second) setting

    def init_data(self):
        return obfs_auth_data()

    def set_server_info(self, server_info):
        self.server_info = server_info
        try:
            max_client = int(server_info.protocol_param)
        except:
            max_client = 16
        self.server_info.data.set_max_client(max_client)

    def pack_data(self, buf):
        if len(buf) == 0:
            return b''
        rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 16)
        data = common.chr(len(rnd_data) + 1) + rnd_data + buf
        data = struct.pack('>H', len(data) + 6) + data
        crc = (0xffffffff - binascii.crc32(data)) & 0xffffffff
        data += struct.pack('<I', crc)
        return data

    def auth_data(self):
        utc_time = int(time.time()) & 0xFFFFFFFF
        if self.server_info.data.connection_id > 0xFF000000:
            self.server_info.data.local_client_id = b''
        if not self.server_info.data.local_client_id:
            self.server_info.data.local_client_id = os.urandom(4)
            logging.debug("local_client_id %s" % (binascii.hexlify(self.server_info.data.local_client_id),))
            self.server_info.data.connection_id = struct.unpack('<I', os.urandom(4))[0] & 0xFFFFFF
        self.server_info.data.connection_id += 1
        return b''.join([struct.pack('<I', utc_time),
                self.server_info.data.local_client_id,
                struct.pack('<I', self.server_info.data.connection_id)])

    def client_pre_encrypt(self, buf):
        ret = b''
        if not self.has_sent_header:
            head_size = self.get_head_size(buf, 30)
            datalen = min(len(buf), random.randint(0, 31) + head_size)
            ret += self.pack_data(self.auth_data() + buf[:datalen])
            buf = buf[datalen:]
            self.has_sent_header = True
        while len(buf) > self.unit_len:
            ret += self.pack_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_data(buf)
        return ret

    def client_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return None
                else:
                    raise Exception('client_post_decrypt data error')
            if length > len(self.recv_buf):
                break

            if (binascii.crc32(self.recv_buf[:length]) & 0xffffffff) != 0xffffffff:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return None
                else:
                    raise Exception('client_post_decrypt data uncorrect CRC32')

            pos = common.ord(self.recv_buf[2]) + 2
            out_buf += self.recv_buf[pos:length - 4]
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.decrypt_packet_num += 1
        return out_buf

    def server_pre_encrypt(self, buf):
        ret = b''
        while len(buf) > self.unit_len:
            ret += self.pack_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_data(buf)
        return ret

    def server_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    logging.info('auth_simple: over size')
                    return b'E'
                else:
                    raise Exception('server_post_decrype data error')
            if length > len(self.recv_buf):
                break

            if (binascii.crc32(self.recv_buf[:length]) & 0xffffffff) != 0xffffffff:
                logging.info('auth_simple: crc32 error, data %s' % (binascii.hexlify(self.recv_buf[:length]),))
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return b'E'
                else:
                    raise Exception('server_post_decrype data uncorrect CRC32')

            pos = common.ord(self.recv_buf[2]) + 2
            out_buf += self.recv_buf[pos:length - 4]
            if not self.has_recv_header:
                if len(out_buf) < 12:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: too short')
                    return b'E'
                utc_time = struct.unpack('<I', out_buf[:4])[0]
                client_id = struct.unpack('<I', out_buf[4:8])[0]
                connection_id = struct.unpack('<I', out_buf[8:12])[0]
                time_dif = common.int32((int(time.time()) & 0xffffffff) - utc_time)
                if time_dif < -self.max_time_dif or time_dif > self.max_time_dif \
                        or common.int32(utc_time - self.server_info.data.startup_time) < 0:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
                    return b'E'
                elif self.server_info.data.insert(client_id, connection_id):
                    self.has_recv_header = True
                    out_buf = out_buf[12:]
                    self.client_id = client_id
                    self.connection_id = connection_id
                else:
                    self.raw_trans = True
                    self.recv_buf = b''
                    logging.info('auth_simple: auth fail, data %s' % (binascii.hexlify(out_buf),))
                    return b'E'
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.server_info.data.update(self.client_id, self.connection_id)
            self.decrypt_packet_num += 1
        return out_buf

class auth_sha1(verify_base):
    def __init__(self, method):
        super(auth_sha1, self).__init__(method)
        self.recv_buf = b''
        self.unit_len = 8100
        self.decrypt_packet_num = 0
        self.raw_trans = False
        self.has_sent_header = False
        self.has_recv_header = False
        self.client_id = 0
        self.connection_id = 0
        self.max_time_dif = 60 * 60 # time dif (second) setting

    def init_data(self):
        return obfs_auth_data()

    def set_server_info(self, server_info):
        self.server_info = server_info
        try:
            max_client = int(server_info.protocol_param)
        except:
            max_client = 64
        self.server_info.data.set_max_client(max_client)

    def pack_data(self, buf):
        if len(buf) == 0:
            return b''
        rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 16)
        data = common.chr(len(rnd_data) + 1) + rnd_data + buf
        data = struct.pack('>H', len(data) + 6) + data
        adler32 = zlib.adler32(data) & 0xFFFFFFFF
        data += struct.pack('<I', adler32)
        return data

    def pack_auth_data(self, buf):
        if len(buf) == 0:
            return b''
        rnd_data = os.urandom(common.ord(os.urandom(1)[0]) % 128)
        data = common.chr(len(rnd_data) + 1) + rnd_data + buf
        data = struct.pack('>H', len(data) + 16) + data
        crc = binascii.crc32(self.server_info.key)
        data = struct.pack('<I', crc) + data
        data += hmac.new(self.server_info.iv + self.server_info.key, data, hashlib.sha1).digest()[:10]
        return data

    def auth_data(self):
        utc_time = int(time.time()) & 0xFFFFFFFF
        if self.server_info.data.connection_id > 0xFF000000:
            self.server_info.data.local_client_id = b''
        if not self.server_info.data.local_client_id:
            self.server_info.data.local_client_id = os.urandom(4)
            logging.debug("local_client_id %s" % (binascii.hexlify(self.server_info.data.local_client_id),))
            self.server_info.data.connection_id = struct.unpack('<I', os.urandom(4))[0] & 0xFFFFFF
        self.server_info.data.connection_id += 1
        return b''.join([struct.pack('<I', utc_time),
                self.server_info.data.local_client_id,
                struct.pack('<I', self.server_info.data.connection_id)])

    def client_pre_encrypt(self, buf):
        ret = b''
        if not self.has_sent_header:
            head_size = self.get_head_size(buf, 30)
            datalen = min(len(buf), random.randint(0, 31) + head_size)
            ret += self.pack_auth_data(self.auth_data() + buf[:datalen])
            buf = buf[datalen:]
            self.has_sent_header = True
        while len(buf) > self.unit_len:
            ret += self.pack_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_data(buf)
        return ret

    def client_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return None
                else:
                    raise Exception('client_post_decrypt data error')
            if length > len(self.recv_buf):
                break

            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return None
                else:
                    raise Exception('client_post_decrypt data uncorrect checksum')

            pos = common.ord(self.recv_buf[2]) + 2
            out_buf += self.recv_buf[pos:length - 4]
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.decrypt_packet_num += 1
        return out_buf

    def server_pre_encrypt(self, buf):
        if self.raw_trans:
            return buf
        ret = b''
        while len(buf) > self.unit_len:
            ret += self.pack_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_data(buf)
        return ret

    def server_post_decrypt(self, buf):
        if self.raw_trans:
            return buf
        self.recv_buf += buf
        out_buf = b''
        if not self.has_recv_header:
            if len(self.recv_buf) < 4:
                return b''
            crc = struct.pack('<I', binascii.crc32(self.server_info.key) & 0xFFFFFFFF)
            if crc != self.recv_buf[:4]:
                if self.method == 'auth_sha1':
                    return b'E'
                else:
                    self.raw_trans = True
                    return self.recv_buf
            length = struct.unpack('>H', self.recv_buf[4:6])[0]
            if length > len(self.recv_buf):
                return b''
            sha1data = hmac.new(self.server_info.recv_iv + self.server_info.key, self.recv_buf[:length - 10], hashlib.sha1).digest()[:10]
            if sha1data != self.recv_buf[length - 10:length]:
                logging.error('auth_sha1 data uncorrect auth HMAC-SHA1')
                return b'E'
            pos = common.ord(self.recv_buf[6]) + 6
            out_buf = self.recv_buf[pos:length - 10]
            if len(out_buf) < 12:
                self.raw_trans = True
                self.recv_buf = b''
                logging.info('auth_sha1: too short')
                return b'E'
            utc_time = struct.unpack('<I', out_buf[:4])[0]
            client_id = struct.unpack('<I', out_buf[4:8])[0]
            connection_id = struct.unpack('<I', out_buf[8:12])[0]
            time_dif = common.int32((int(time.time()) & 0xffffffff) - utc_time)
            if time_dif < -self.max_time_dif or time_dif > self.max_time_dif \
                    or common.int32(utc_time - self.server_info.data.startup_time) < -self.max_time_dif / 2:
                self.raw_trans = True
                self.recv_buf = b''
                logging.info('auth_sha1: wrong timestamp, time_dif %d, data %s' % (time_dif, binascii.hexlify(out_buf),))
                return b'E'
            elif self.server_info.data.insert(client_id, connection_id):
                self.has_recv_header = True
                out_buf = out_buf[12:]
                self.client_id = client_id
                self.connection_id = connection_id
            else:
                self.raw_trans = True
                self.recv_buf = b''
                logging.info('auth_sha1: auth fail, data %s' % (binascii.hexlify(out_buf),))
                return b'E'
            self.recv_buf = self.recv_buf[length:]
            self.has_recv_header = True

        while len(self.recv_buf) > 2:
            length = struct.unpack('>H', self.recv_buf[:2])[0]
            if length >= 8192 or length < 7:
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    logging.info('auth_sha1: over size')
                    return b'E'
                else:
                    raise Exception('server_post_decrype data error')
            if length > len(self.recv_buf):
                break

            if struct.pack('<I', zlib.adler32(self.recv_buf[:length - 4]) & 0xFFFFFFFF) != self.recv_buf[length - 4:length]:
                logging.info('auth_sha1: checksum error, data %s' % (binascii.hexlify(self.recv_buf[:length]),))
                self.raw_trans = True
                self.recv_buf = b''
                if self.decrypt_packet_num == 0:
                    return b'E'
                else:
                    raise Exception('server_post_decrype data uncorrect checksum')

            pos = common.ord(self.recv_buf[2]) + 2
            out_buf += self.recv_buf[pos:length - 4]
            self.recv_buf = self.recv_buf[length:]

        if out_buf:
            self.server_info.data.update(self.client_id, self.connection_id)
            self.decrypt_packet_num += 1
        return out_buf