xman随机数相关题目

参加xman夏令营，大佬给我们带来了密码学课程。其中随机数部分感受颇深，记录下几个脚本。

1. 以时间作为种子的随机数

https://www.jarvisoj.com/ 的[xman2019]babyrpd

服务端代码

 class Unbuffered(object):

    def __init__(self, stream):

        self.stream = stream

    def write(self, data):

        self.stream.write(data)

        self.stream.flush()

    def __getattr__(self, attr):

        return getattr(self.stream, attr)

 import sys

 sys.stdout = Unbuffered(sys.stdout)

 import signal

 signal.alarm(600)

 import random

 import time

 flag=open("/root/level0/flag","r").read()

 random.seed(int(time.time()))

 def check():

     recv=int(raw_input())

     if recv==random.randint(0,2**64):

         print flag

         return True

     else:

         print "atum tql"

         return False

 while 1:

     if check():

         break

解决方法：

预测时间种子，进行攻击

 #coding=utf-8

 import socket

 import random

 import time

 while True:

     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

     host = '47.97.215.88'

     port = 20000

     random.seed(int(time.time()+2))  #加上延迟所以+2秒

     s.connect((host, port))

     s.send(str(random.randint(0,2**64))+'\n')

     print s.recv(1024)

2. java的Random随机数

https://www.jarvisoj.com/ 的[xman2019]mediumrpd

服务端代码：

 class Unbuffered(object):

    def __init__(self, stream):

        self.stream = stream

    def write(self, data):

        self.stream.write(data)

        self.stream.flush()

    def __getattr__(self, attr):

        return getattr(self.stream, attr)

 import sys

 sys.stdout = Unbuffered(sys.stdout)

 import signal

 signal.alarm(600)

 import os

 os.chdir("/root/level1")

 flag=open("flag","r").read()

 import subprocess

 o = subprocess.check_output(["java", "Main"])

 tmp=[]

 for i in o.split("\n")[0:3]:

     tmp.append(int(i.strip()))

 v1=tmp[0] % 0xffffffff

 v2=tmp[1] % 0xffffffff

 v3=tmp[2] % 0xffffffff

 print v1

 print v2

 v3_get=int(raw_input())

 if v3_get==v3:

     print flag

 import java.util.Random;

 public class Main {

     public static void main(String[] args) {

         Random random = new Random();

         System.out.println(random.nextInt());

         System.out.println(random.nextInt());

         System.out.println(random.nextInt());

     }

 }

攻击方法

从题目获取到两个随机数v1,v2，通过已知公式，可以计算出v3

 import socket

 import random

 import time

 def liner (seed):

     return ((seed*25214903917+11)&0xffffffffffff)

 while True:

     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

     host = '47.97.215.88'

     port = 20001

     s.connect((host, port))

     v1=int(s.recv(1024))

     v2=int(s.recv(1024))

     for i in range(65536):

         seed=v1*65536+i

         if liner(seed)>>16==v2:

             print seed

             v3=liner(liner(seed))>>16

             s.send(str(v3)+'\n')

             print s.recv(1024)

3. python的random

来源是：Mersenne Twister

大佬说php的mt_rand（可以用php_mt_seed攻击）,ruby的rand()，python的random都可以攻击，但我只弄出python的版本

题目为https://www.jarvisoj.com/ 的[xman2019]hardrpd

参考文章：https://ddaa.tw/30c3ctf_2013_number_100_guess.html

https://jazzy.id.au/2010/09/22/cracking_random_number_generators_part_3.html

服务端代码：

 class Unbuffered(object):

    def __init__(self, stream):

        self.stream = stream

    def write(self, data):

        self.stream.write(data)

        self.stream.flush()

    def __getattr__(self, attr):

        return getattr(self.stream, attr)

 import sys

 sys.stdout = Unbuffered(sys.stdout)

 import os

 os.chdir("/root/level2")

 from random import *

 while 1:

     a=raw_input("#")

     target=getrandbits(32)

     if a!=str(target):

         print target

     else:

         print open("flag","rb").read()

攻击脚本：（改写至TokyoWestern CTF WriteUp by r3kapig）

 #coding=utf-8

 import socket

 import random

 import time

 def unBitshiftRightXor (value,shift):

     i = 0

     result = 0

     while i * shift < 32:

          partMask = right((-1 << (32 - shift)) , (shift * i))

          part = value & partMask

          value ^= right(part , shift)

          result |= part

          i+=1

     return result

 def unBitshiftLeftXor(value, shift, mask):

     i = 0;

     result = 0;

     while i * shift < 32:

         partMask = right(-1 , (32 - shift)) << (shift * i)

         part = value & partMask

         value ^= (part << shift) & mask

         result |= part

         i += 1

     return result

 def rev(nums):

     state=[]

     for i in nums:

         value = i;

         value = unBitshiftRightXor(value, 18)

         value = unBitshiftLeftXor(value, 15, 0xefc60000)

         value = unBitshiftLeftXor(value, 7, 0x9d2c5680)

         state.append(unBitshiftRightXor(value, 11))

     return state

 def sign(iv):

     if(iv&0x80000000):

         iv = -0x100000000 + iv

     return iv

 def nextState(state):

     for i in range(624):

         y = (state[i] & 0x80000000) + (state[(i + 1) % 624] & 0x7fffffff)

         next = right(y,1);

         next ^= state[(i + 397) % 624]

         if ((y & 1L) == 1L):

             next ^= 0x9908b0df

         state[i] = next

 def nextNumber(state):

     currentIndex=0

     tmp = state[currentIndex];

     tmp ^= right(tmp , 11)

     tmp ^= (tmp << 7) & 0x9d2c5680

     tmp ^= (tmp << 15) & 0xefc60000

     tmp ^= right(tmp , 18)

     return tmp

 def right(n,bit): #python没有>>>运算符，这个函数用作代替

     x=n

     if n<0 and bit>0:

         n=(2147483648*2+n)>>bit

     else:

         n=n>>bit

     return n

 def crack_prng(outputs_624_list):

     state=rev(outputs_624_list)

     stateList = state[:]

     nextState(state)

     r = random.Random()

     state = (3, tuple(stateList + [624]), None)

     r.setstate(state)

     return r

 '''

 #本地测试代码

 n=[random.getrandbits(32) for i in range(625)]

 r=crack_prng(n[:-1])

 print n[-1],r.getrandbits(32)

 '''

 n=[]

 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

 host = '47.97.215.88'

 port = 20002

 s.connect((host, port))

 for i in range(624):

     print s.recv(1024),i,

     s.send('\n')

     n.append(int(s.recv(1024)))

 r=crack_prng(n)

 s.send(str(r.getrandbits(32))+'\n')

 print s.recv(1024),s.recv(1024)

巴特西

xman随机数相关题目

1. 以时间作为种子的随机数

2. java的Random随机数

3. python的random

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