shadowsocksr/shadowsocks/obfsplugin/auth_chain.py

#!/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 math
import struct
import zlib
import hmac
import hashlib
import bisect

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

def create_auth_chain_a(method):
    return auth_chain_a(method)

def create_auth_chain_b(method):
    return auth_chain_b(method)

obfs_map = {
        'auth_chain_a': (create_auth_chain_a,),
        'auth_chain_b': (create_auth_chain_b,),
}

class xorshift128plus(object):
    max_int = (1 << 64) - 1
    mov_mask = (1 << (64 - 23)) - 1

    def __init__(self):
        self.v0 = 0
        self.v1 = 0

    def next(self):
        x = self.v0
        y = self.v1
        self.v0 = y
        x ^= ((x & xorshift128plus.mov_mask) << 23)
        x ^= (y ^ (x >> 17) ^ (y >> 26)) & xorshift128plus.max_int
        self.v1 = x
        return (x + y) & xorshift128plus.max_int

    def init_from_bin(self, bin):
        bin += b'\0' * 16
        self.v0 = struct.unpack('<Q', bin[:8])[0]
        self.v1 = struct.unpack('<Q', bin[8:16])[0]

    def init_from_bin_len(self, bin, length):
        bin += b'\0' * 16
        bin = struct.pack('<H', length) + bin[2:]
        self.v0 = struct.unpack('<Q', bin[:8])[0]
        self.v1 = struct.unpack('<Q', bin[8:16])[0]

        for i in range(4):
            self.next()

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

class auth_base(plain.plain):
    def __init__(self, method):
        super(auth_base, self).__init__(method)
        self.method = method
        self.no_compatible_method = ''
        self.overhead = 4

    def init_data(self):
        return ''

    def get_overhead(self, direction): # direction: true for c->s false for s->c
        return self.overhead

    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)

    def not_match_return(self, buf):
        self.raw_trans = True
        self.overhead = 0
        if self.method == self.no_compatible_method:
            return (b'E'*2048, False)
        return (buf, False)

class client_queue(object):
    def __init__(self, begin_id):
        self.front = begin_id - 64
        self.back = begin_id + 1
        self.alloc = {}
        self.enable = True
        self.last_update = time.time()
        self.ref = 0

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

    def addref(self):
        self.ref += 1

    def delref(self):
        if self.ref > 0:
            self.ref -= 1

    def is_active(self):
        return (self.ref > 0) and (time.time() - self.last_update < 60 * 10)

    def re_enable(self, connection_id):
        self.enable = True
        self.front = connection_id - 64
        self.back = connection_id + 1
        self.alloc = {}

    def insert(self, connection_id):
        if not self.enable:
            logging.warn('obfs auth: not enable')
            return False
        if not self.is_active():
            self.re_enable(connection_id)
        self.update()
        if connection_id < self.front:
            logging.warn('obfs auth: deprecated id, someone replay attack')
            return False
        if connection_id > self.front + 0x4000:
            logging.warn('obfs auth: wrong id')
            return False
        if connection_id in self.alloc:
            logging.warn('obfs auth: duplicate id, someone replay attack')
            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
        self.addref()
        return True

class obfs_auth_chain_data(object):
    def __init__(self, name):
        self.name = name
        self.user_id = {}
        self.local_client_id = b''
        self.connection_id = 0
        self.set_max_client(64) # max active client count

    def update(self, user_id, client_id, connection_id):
        if user_id not in self.user_id:
            self.user_id[user_id] = lru_cache.LRUCache()
        local_client_id = self.user_id[user_id]

        if client_id in local_client_id:
            local_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, 1024)

    def insert(self, user_id, client_id, connection_id):
        if user_id not in self.user_id:
            self.user_id[user_id] = lru_cache.LRUCache()
        local_client_id = self.user_id[user_id]

        if local_client_id.get(client_id, None) is None or not local_client_id[client_id].enable:
            if local_client_id.first() is None or len(local_client_id) < self.max_client:
                if client_id not in local_client_id:
                    #TODO: check
                    local_client_id[client_id] = client_queue(connection_id)
                else:
                    local_client_id[client_id].re_enable(connection_id)
                return local_client_id[client_id].insert(connection_id)

            if not local_client_id[local_client_id.first()].is_active():
                del local_client_id[local_client_id.first()]
                if client_id not in local_client_id:
                    #TODO: check
                    local_client_id[client_id] = client_queue(connection_id)
                else:
                    local_client_id[client_id].re_enable(connection_id)
                return local_client_id[client_id].insert(connection_id)

            logging.warn(self.name + ': no inactive client')
            return False
        else:
            return local_client_id[client_id].insert(connection_id)

    def remove(self, user_id, client_id):
        if user_id in self.user_id:
            local_client_id = self.user_id[user_id]
            if client_id in local_client_id:
                local_client_id[client_id].delref()

class auth_chain_a(auth_base):
    def __init__(self, method):
        super(auth_chain_a, self).__init__(method)
        self.hashfunc = hashlib.md5
        self.recv_buf = b''
        self.unit_len = 2800
        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 * 24 # time dif (second) setting
        self.salt = b"auth_chain_a"
        self.no_compatible_method = 'auth_chain_a'
        self.pack_id = 1
        self.recv_id = 1
        self.user_id = None
        self.user_id_num = 0
        self.user_key = None
        self.overhead = 4
        self.client_over_head = 4
        self.last_client_hash = b''
        self.last_server_hash = b''
        self.random_client = xorshift128plus()
        self.random_server = xorshift128plus()
        self.encryptor = None

    def init_data(self):
        return obfs_auth_chain_data(self.method)

    def get_overhead(self, direction): # direction: true for c->s false for s->c
        return self.overhead

    def set_server_info(self, server_info):
        self.server_info = server_info
        try:
            max_client = int(server_info.protocol_param.split('#')[0])
        except:
            max_client = 64
        self.server_info.data.set_max_client(max_client)

    def trapezoid_random_float(self, d):
        if d == 0:
            return random.random()
        s = random.random()
        a = 1 - d
        return (math.sqrt(a * a + 4 * d * s) - a) / (2 * d)

    def trapezoid_random_int(self, max_val, d):
        v = self.trapezoid_random_float(d)
        return int(v * max_val)

    def rnd_data_len(self, buf_size, last_hash, random):
        if buf_size > 1440:
            return 0
        random.init_from_bin_len(last_hash, buf_size)
        if buf_size > 1300:
            return random.next() % 31
        if buf_size > 900:
            return random.next() % 127
        if buf_size > 400:
            return random.next() % 521
        return random.next() % 1021

    def udp_rnd_data_len(self, last_hash, random):
        random.init_from_bin(last_hash)
        return random.next() % 127

    def rnd_start_pos(self, rand_len, random):
        if rand_len > 0:
            return random.next() % 8589934609 % rand_len
        return 0

    def rnd_data(self, buf_size, buf, last_hash, random):
        rand_len = self.rnd_data_len(buf_size, last_hash, random)

        rnd_data_buf = os.urandom(rand_len)

        if buf_size == 0:
            return rnd_data_buf
        else:
            if rand_len > 0:
                start_pos = self.rnd_start_pos(rand_len, random)
                return rnd_data_buf[:start_pos] + buf + rnd_data_buf[start_pos:]
            else:
                return buf

    def pack_client_data(self, buf):
        buf = self.encryptor.encrypt(buf)
        data = self.rnd_data(len(buf), buf, self.last_client_hash, self.random_client)
        data_len = len(data) + 8
        mac_key = self.user_key + struct.pack('<I', self.pack_id)
        length = len(buf) ^ struct.unpack('<H', self.last_client_hash[14:])[0]
        data = struct.pack('<H', length) + data
        self.last_client_hash = hmac.new(mac_key, data, self.hashfunc).digest()
        data += self.last_client_hash[:2]
        self.pack_id = (self.pack_id + 1) & 0xFFFFFFFF
        return data

    def pack_server_data(self, buf):
        buf = self.encryptor.encrypt(buf)
        data = self.rnd_data(len(buf), buf, self.last_server_hash, self.random_server)
        data_len = len(data) + 8
        mac_key = self.user_key + struct.pack('<I', self.pack_id)
        length = len(buf) ^ struct.unpack('<H', self.last_server_hash[14:])[0]
        data = struct.pack('<H', length) + data
        self.last_server_hash = hmac.new(mac_key, data, self.hashfunc).digest()
        data += self.last_server_hash[:2]
        self.pack_id = (self.pack_id + 1) & 0xFFFFFFFF
        return data

    def pack_auth_data(self, auth_data, buf):
        data = auth_data
        data_len = 12 + 4 + 16 + 4
        data = data + (struct.pack('<H', self.server_info.overhead) + struct.pack('<H', 0))
        mac_key = self.server_info.iv + self.server_info.key

        check_head = os.urandom(4)
        self.last_client_hash = hmac.new(mac_key, check_head, self.hashfunc).digest()
        check_head += self.last_client_hash[:8]

        if b':' in to_bytes(self.server_info.protocol_param):
            try:
                items = to_bytes(self.server_info.protocol_param).split(b':')
                self.user_key = items[1]
                uid = struct.pack('<I', int(items[0]))
            except:
                uid = os.urandom(4)
        else:
            uid = os.urandom(4)
        if self.user_key is None:
            self.user_key = self.server_info.key

        encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + self.salt, 'aes-128-cbc', b'\x00' * 16)

        uid = struct.unpack('<I', uid)[0] ^ struct.unpack('<I', self.last_client_hash[8:12])[0]
        uid = struct.pack('<I', uid)
        data = uid + encryptor.encrypt(data)[16:]
        self.last_server_hash = hmac.new(self.user_key, data, self.hashfunc).digest()
        data = check_head + data + self.last_server_hash[:4]
        self.encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + to_bytes(base64.b64encode(self.last_client_hash)), 'rc4')
        return data + self.pack_client_data(buf)

    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''
        ogn_data_len = len(buf)
        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_client_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_client_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) > 4:
            mac_key = self.user_key + struct.pack('<I', self.recv_id)
            data_len = struct.unpack('<H', self.recv_buf[:2])[0] ^ struct.unpack('<H', self.last_server_hash[14:16])[0]
            rand_len = self.rnd_data_len(data_len, self.last_server_hash, self.random_server)
            length = data_len + rand_len
            if length >= 4096:
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data error')

            if length + 4 > len(self.recv_buf):
                break

            server_hash = hmac.new(mac_key, self.recv_buf[:length + 2], self.hashfunc).digest()
            if server_hash[:2] != self.recv_buf[length + 2 : length + 4]:
                logging.info('%s: checksum error, data %s' % (self.no_compatible_method, binascii.hexlify(self.recv_buf[:length])))
                self.raw_trans = True
                self.recv_buf = b''
                raise Exception('client_post_decrypt data uncorrect checksum')

            pos = 2
            if data_len > 0 and rand_len > 0:
                pos = 2 + self.rnd_start_pos(rand_len, self.random_server)
            out_buf += self.encryptor.decrypt(self.recv_buf[pos : data_len + pos])
            self.last_server_hash = server_hash
            if self.recv_id == 1:
                self.server_info.tcp_mss = struct.unpack('<H', out_buf[:2])[0]
                out_buf = out_buf[2:]
            self.recv_id = (self.recv_id + 1) & 0xFFFFFFFF
            self.recv_buf = self.recv_buf[length + 4:]

        return out_buf

    def server_pre_encrypt(self, buf):
        if self.raw_trans:
            return buf
        ret = b''
        if self.pack_id == 1:
            tcp_mss = self.server_info.tcp_mss if self.server_info.tcp_mss < 1500 else 1500
            self.server_info.tcp_mss = tcp_mss
            buf = struct.pack('<H', tcp_mss) + buf
            self.unit_len = tcp_mss - self.client_over_head
        while len(buf) > self.unit_len:
            ret += self.pack_server_data(buf[:self.unit_len])
            buf = buf[self.unit_len:]
        ret += self.pack_server_data(buf)
        return ret

    def server_post_decrypt(self, buf):
        if self.raw_trans:
            return (buf, False)
        self.recv_buf += buf
        out_buf = b''
        sendback = False

        if not self.has_recv_header:
            if len(self.recv_buf) >= 12 or len(self.recv_buf) in [7, 8]:
                recv_len = min(len(self.recv_buf), 12)
                mac_key = self.server_info.recv_iv + self.server_info.key
                md5data = hmac.new(mac_key, self.recv_buf[:4], self.hashfunc).digest()
                if md5data[:recv_len - 4] != self.recv_buf[4:recv_len]:
                    return self.not_match_return(self.recv_buf)

            if len(self.recv_buf) < 12 + 24:
                return (b'', False)

            self.last_client_hash = md5data
            uid = struct.unpack('<I', self.recv_buf[12:16])[0] ^ struct.unpack('<I', md5data[8:12])[0]
            self.user_id_num = uid
            uid = struct.pack('<I', uid)
            if uid in self.server_info.users:
                self.user_id = uid
                self.user_key = self.server_info.users[uid]
                self.server_info.update_user_func(uid)
            else:
                self.user_id_num = 0
                if not self.server_info.users:
                    self.user_key = self.server_info.key
                else:
                    self.user_key = self.server_info.recv_iv

            md5data = hmac.new(self.user_key, self.recv_buf[12 : 12 + 20], self.hashfunc).digest()
            if md5data[:4] != self.recv_buf[32:36]:
                logging.error('%s data uncorrect auth HMAC-MD5 from %s:%d, data %s' % (self.no_compatible_method, self.server_info.client, self.server_info.client_port, binascii.hexlify(self.recv_buf)))
                if len(self.recv_buf) < 36:
                    return (b'', False)
                return self.not_match_return(self.recv_buf)

            self.last_server_hash = md5data
            encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + self.salt, 'aes-128-cbc')
            head = encryptor.decrypt(b'\x00' * 16 + self.recv_buf[16:32] + b'\x00') # need an extra byte or recv empty
            self.client_over_head = struct.unpack('<H', head[12:14])[0]

            utc_time = struct.unpack('<I', head[:4])[0]
            client_id = struct.unpack('<I', head[4:8])[0]
            connection_id = struct.unpack('<I', head[8:12])[0]
            time_dif = common.int32(utc_time - (int(time.time()) & 0xffffffff))
            if time_dif < -self.max_time_dif or time_dif > self.max_time_dif:
                logging.info('%s: wrong timestamp, time_dif %d, data %s' % (self.no_compatible_method, time_dif, binascii.hexlify(head)))
                return self.not_match_return(self.recv_buf)
            elif self.server_info.data.insert(self.user_id, client_id, connection_id):
                self.has_recv_header = True
                self.client_id = client_id
                self.connection_id = connection_id
            else:
                logging.info('%s: auth fail, data %s' % (self.no_compatible_method, binascii.hexlify(out_buf)))
                return self.not_match_return(self.recv_buf)

            self.encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + to_bytes(base64.b64encode(self.last_client_hash)), 'rc4')
            self.recv_buf = self.recv_buf[36:]
            self.has_recv_header = True
            sendback = True

        while len(self.recv_buf) > 4:
            mac_key = self.user_key + struct.pack('<I', self.recv_id)
            data_len = struct.unpack('<H', self.recv_buf[:2])[0] ^ struct.unpack('<H', self.last_client_hash[14:16])[0]
            rand_len = self.rnd_data_len(data_len, self.last_client_hash, self.random_client)
            length = data_len + rand_len
            if length >= 4096:
                self.raw_trans = True
                self.recv_buf = b''
                if self.recv_id == 0:
                    logging.info(self.no_compatible_method + ': over size')
                    return (b'E'*2048, False)
                else:
                    raise Exception('server_post_decrype data error')

            if length + 4 > len(self.recv_buf):
                break

            client_hash = hmac.new(mac_key, self.recv_buf[:length + 2], self.hashfunc).digest()
            if client_hash[:2] != self.recv_buf[length + 2 : length + 4]:
                logging.info('%s: checksum error, data %s' % (self.no_compatible_method, binascii.hexlify(self.recv_buf[:length])))
                self.raw_trans = True
                self.recv_buf = b''
                if self.recv_id == 0:
                    return (b'E'*2048, False)
                else:
                    raise Exception('server_post_decrype data uncorrect checksum')

            self.recv_id = (self.recv_id + 1) & 0xFFFFFFFF
            pos = 2
            if data_len > 0 and rand_len > 0:
                pos = 2 + self.rnd_start_pos(rand_len, self.random_client)
            out_buf += self.encryptor.decrypt(self.recv_buf[pos : data_len + pos])
            self.last_client_hash = client_hash
            self.recv_buf = self.recv_buf[length + 4:]
            if data_len == 0:
                sendback = True

        if out_buf:
            self.server_info.data.update(self.user_id, self.client_id, self.connection_id)
        return (out_buf, sendback)

    def client_udp_pre_encrypt(self, buf):
        if self.user_key is None:
            if b':' in to_bytes(self.server_info.protocol_param):
                try:
                    items = to_bytes(self.server_info.protocol_param).split(':')
                    self.user_key = self.hashfunc(items[1]).digest()
                    self.user_id = struct.pack('<I', int(items[0]))
                except:
                    pass
            if self.user_key is None:
                self.user_id = os.urandom(4)
                self.user_key = self.server_info.key
        authdata = os.urandom(3)
        mac_key = self.server_info.key
        md5data = hmac.new(mac_key, authdata, self.hashfunc).digest()
        uid = struct.unpack('<I', self.user_id)[0] ^ struct.unpack('<I', md5data[:4])[0]
        uid = struct.pack('<I', uid)
        rand_len = self.udp_rnd_data_len(md5data, self.random_client)
        encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + to_bytes(base64.b64encode(md5data)), 'rc4')
        out_buf = encryptor.encrypt(buf)
        buf = out_buf + os.urandom(rand_len) + authdata + uid
        return buf + hmac.new(self.user_key, buf, self.hashfunc).digest()[:1]

    def client_udp_post_decrypt(self, buf):
        if len(buf) <= 8:
            return (b'', None)
        if hmac.new(self.user_key, buf[:-1], self.hashfunc).digest()[:1] != buf[-1:]:
            return (b'', None)
        mac_key = self.server_info.key
        md5data = hmac.new(mac_key, buf[-8:-1], self.hashfunc).digest()
        rand_len = self.udp_rnd_data_len(md5data, self.random_server)
        encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(self.user_key)) + to_bytes(base64.b64encode(md5data)), 'rc4')
        return encryptor.decrypt(buf[:-8 - rand_len])

    def server_udp_pre_encrypt(self, buf, uid):
        if uid in self.server_info.users:
            user_key = self.server_info.users[uid]
        else:
            uid = None
            if not self.server_info.users:
                user_key = self.server_info.key
            else:
                user_key = self.server_info.recv_iv
        authdata = os.urandom(7)
        mac_key = self.server_info.key
        md5data = hmac.new(mac_key, authdata, self.hashfunc).digest()
        rand_len = self.udp_rnd_data_len(md5data, self.random_server)
        encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(user_key)) + to_bytes(base64.b64encode(md5data)), 'rc4')
        out_buf = encryptor.encrypt(buf)
        buf = out_buf + os.urandom(rand_len) + authdata
        return buf + hmac.new(user_key, buf, self.hashfunc).digest()[:1]

    def server_udp_post_decrypt(self, buf):
        mac_key = self.server_info.key
        md5data = hmac.new(mac_key, buf[-8:-5], self.hashfunc).digest()
        uid = struct.unpack('<I', buf[-5:-1])[0] ^ struct.unpack('<I', md5data[:4])[0]
        uid = struct.pack('<I', uid)
        if uid in self.server_info.users:
            user_key = self.server_info.users[uid]
        else:
            uid = None
            if not self.server_info.users:
                user_key = self.server_info.key
            else:
                user_key = self.server_info.recv_iv
        if hmac.new(user_key, buf[:-1], self.hashfunc).digest()[:1] != buf[-1:]:
            return (b'', None)
        rand_len = self.udp_rnd_data_len(md5data, self.random_client)
        encryptor = encrypt.Encryptor(to_bytes(base64.b64encode(user_key)) + to_bytes(base64.b64encode(md5data)), 'rc4')
        out_buf = encryptor.decrypt(buf[:-8 - rand_len])
        return (out_buf, uid)

    def dispose(self):
        self.server_info.data.remove(self.user_id, self.client_id)

class auth_chain_b(auth_chain_a):
    def __init__(self, method):
        super(auth_chain_b, self).__init__(method)
        self.salt = b"auth_chain_b"
        self.no_compatible_method = 'auth_chain_b'
        # NOTE
        # 补全后长度数组
        # 随机在其中选择一个补全到的长度
        # 为每个连接初始化一个固定内容的数组
        self.data_size_list = []
        self.data_size_list2 = []

    def init_data_size(self, key):
        if self.data_size_list:
            self.data_size_list = []
            self.data_size_list2 = []
        random = xorshift128plus()
        random.init_from_bin(key)
        # 补全数组长为4~12-1
        list_len = random.next() % 8 + 4
        for i in range(0, list_len):
            self.data_size_list.append((int)(random.next() % 2340 % 2040 % 1440))
        self.data_size_list.sort()
        # 补全数组长为8~24-1
        list_len = random.next() % 16 + 8
        for i in range(0, list_len):
            self.data_size_list2.append((int)(random.next() % 2340 % 2040 % 1440))
        self.data_size_list2.sort()

    def set_server_info(self, server_info):
        self.server_info = server_info
        try:
            max_client = int(server_info.protocol_param.split('#')[0])
        except:
            max_client = 64
        self.server_info.data.set_max_client(max_client)
        self.init_data_size(self.server_info.key)

    def rnd_data_len(self, buf_size, last_hash, random):
        if buf_size >= 1440:
            return 0
        random.init_from_bin_len(last_hash, buf_size)
        pos = bisect.bisect_left(self.data_size_list, buf_size + self.server_info.overhead)
        final_pos = pos + random.next() % (len(self.data_size_list))
        # 假设random均匀分布，则越长的原始数据长度越容易if false
        if final_pos < len(self.data_size_list):
            return self.data_size_list[final_pos] - buf_size - self.server_info.overhead

        # 上面if false后选择2号补全数组，此处有更精细的长度分段
        pos = bisect.bisect_left(self.data_size_list2, buf_size + self.server_info.overhead)
        final_pos = pos + random.next() % (len(self.data_size_list2))
        if final_pos < len(self.data_size_list2):
            return self.data_size_list2[final_pos] - buf_size - self.server_info.overhead
        # final_pos 总是分布在pos~(data_size_list2.len-1)之间
        if final_pos < pos + len(self.data_size_list2) - 1:
            return 0
        # 有1/len(self.data_size_list2)的概率不满足上一个if  ?
        # 理论上不会运行到此处，因此可以插入运行断言  ?
        # assert False

        if buf_size > 1300:
            return random.next() % 31
        if buf_size > 900:
            return random.next() % 127
        if buf_size > 400:
            return random.next() % 521
        return random.next() % 1021