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IOCTLbf v0.4 (Proof of Concept) _ _ _ ___ (_) _ | || | / __) _ ___ ____ _| |_| || |__ _| |__ | |/ _ \ / ___|_ _) || _ (_ __) | | |_| ( (___ | |_| || |_) )| | |_|\___/ \____) \__)\_)____/ |_| http://code.google.com/p/ioctlbf/ http://poppopret.blogspot.com email@example.com ===================================================================== Overview ===================================================================== IOCTLbf is just a small tool (Proof of Concept) that can be used to search vulnerabilities in Windows kernel drivers by performing two tasks: - Scanning for valid IOCTLs codes supported by drivers, - Generation-based IOCTL fuzzing An advantage of this tool is that it does not rely on captured IOCTLs. Therefore, it is able to detect valid IOCTLs codes supported by drivers and that are not often, or even never, used by applications from user land. For example, it may be the case for: - IOCTLs called in very specific conditions (not easy to discover and/or to reproduce). - IOCTLs used for debugging purpose that are sometimes let in drivers. Once scanning is done and valid IOCTLs have been found for a given driver, the user can choose one IOCTL in the list to begin the fuzzing process. Note that this tool only performs generation-based fuzzing. Compared to mutation-based fuzzing (which consists in taking valid IOCTL buffers and adding anomalies), the code coverage is of course less important. Note: for mutation-based IOCTL fuzzing, check out the great tool "IOCTL fuzzer" (http://code.google.com/p/ioctlfuzzer/). Basically, it hooks NtDeviceIoControlFile in order to take control of all IOCTL requests throughout the system. ===================================================================== Reminder about IOCTLs ===================================================================== IOCTL codes: ------------ According to winioctl.h: IOCTL's are defined by the following bit layout. [Common |Device Type|Required Access|Custom|Function Code|Transfer Type] 31 30 16 15 14 13 12 2 1 0 Common - 1 bit. This is set for user-defined device types. Device Type - This is the type of device the IOCTL belongs to. This can be user defined (Common bit set). This must match the device type of the device object. Required Access - FILE_READ_DATA, FILE_WRITE_DATA, etc. This is the required access for the device. Custom - 1 bit. This is set for user-defined IOCTL's. This is used in the same manner as "WM_USER". Function Code - This is the function code that the system or the user defined (custom bit set) Transfer Type - METHOD_IN_DIRECT, METHOD_OUT_DIRECT, METHOD_NEITHER, METHOD_BUFFERED, This the data transfer method to be used. For a given device, only the fields "Function Code" and "Transfer Type" change for the different supported IOCTL codes. Buffer specifications: --------------------- Buffer sizes: Input Size = nt!_IO_STACK_LOCATION.Parameters.DeviceIoControl.InputBufferLength Output Size = nt!_IO_STACK_LOCATION.Parameters.DeviceIoControl.OutputBufferLength The way buffers are passed from userland to kernelland, and from kernelland to userland, depends on the method which is used. Here are the differences: - METHOD_BUFFERED: Input Buffer = nt!_IRP.AssociatedIrp.SystemBuffer Output Buffer = nt!_IRP.AssociatedIrp.SystemBuffer input & output buffers use the same location, so the buffer allocated by the I/O manager is the size of the larger value (output vs. input). - METHOD_X_DIRECT: Input Buffer = nt!_IRP.AssociatedIrp.SystemBuffer Output Buffer = nt!_IRP.MdlAddress the input buffer is passed in using "BUFFERED" implementation. The output buffer is passed in using a MDL (which permits Direct Memory Access). The difference between "IN" and "OUT" is that with "IN", you can use the output buffer to pass in data! The "OUT" is only used to return data. - METHOD_NEITHER: Input Buffer = nt!_IO_STACK_LOCATION.Parameters.DeviceIoControl.Type3InputBuffer Output Buffer = nt!_IRP.UserBuffer input & output buffers sizes may be different. The I/O manager does not provide any system buffers or MDLs. The IRP supplies the user-mode virtual addresses of the input and output buffer ===================================================================== Command line options ===================================================================== >ioctlbf.EXE Usage ----- ioctlbf.EXE -d <deviceName> (-i <code>|-r <code>-<code>) [-u] [-q] [-f] [-e] Options ------- -d Symbolic device name (without \\.\) -i IOCTL code used as reference for scanning (see also -u) -r IOCTL codes range (format: 00004000-00008000) to fuzz -u Fuzz only the IOCTL specified with -i -f Filter out IOCTLs with no buffer length restriction -q Quiet mode (do not display hexdumps when fuzzing) -e Display error codes during IOCTL codes scanning -h Display this help Examples -------- Scanning by Function code + Transfer type bruteforce from given valid IOCTL: > ioctlbf.EXE -d deviceName -i 00004000 -q Scanning a given IOCTL codes range (filter enabled): > ioctlbf.EXE -d deviceName -r 00004000-00004fff -f Fuzzing only a given IOCTL (quiet mode): > ioctlbf.EXE -d deviceName -i 00004000 -u -q ===================================================================== Usage ===================================================================== 1. First of all, it is necessary to locate the target driver. A tool like "DriverView" (http://www.nirsoft.net/utils/driverview.html) can be used in order to easily spot non-Microsoft drivers (third-party drivers). 2. Then, it is necessary to check the device(s) associated with the target driver. A good tool to do this is "DeviceTree" for example (http://www.osronline.com/article.cfm?article=97) 3. Check the security attributes (DACL) of the device(s). It should be available for limited users in order to make it interesting from an attacker point of view. Indeed, vulnerabilities in drivers may lead to Local Privilege Escalation on the system, or just Denial of Service when it is not exploitable. 4. Retrieve the symbolic link used by applications to communicate with one device of the target driver. All symbolic links can be listed with the Sysinternal's tool "WinObj" in the "GLOBAL??" section (http://technet.microsoft.com/en-us/sysinternals/bb896657). 5. Finally, it is necessary to know at least one valid IOCTL code supported by the target driver. For example, it can be easily done by monitoring IRPs with a tool like "OSR's IrpTracker Utility" (http://www.osronline.com/article.cfm?article=199). Make sure to apply a filter on "DEVICE_CONTROL" only and to select only the target driver. Of course, it is also possible to retrieve valid IOCTL codes directly by reverse engineering the driver. 6. Once a valid IOCTL code is retrieved, "ioctlbf" can be used. One of the following IOCTL codes scanning modes can be chosen: - Function code + Transfer type bruteforce - IOCTL codes range - Single IOCTL code The scanning process returns supported IOCTL codes and accepted buffer sizes for each one. 7. The next step simply consists in chosing one IOCTL to fuzz. The fuzzing process actually follows the following steps: - [if method != METHOD_BUFFERED] Invalid addresses of input/output buffers - Check for trivial kernel overflows - Fuzzing with predetermined DWORDs (invalid addresses, addresses pointing to long ascii/unicode strings, address pointing to a table of invalid addresses). - Fuzzing with fully random data ===================================================================== Example ===================================================================== >ioctlbf.EXE -d aswSnx -i 82ac0200 -q [~] Open handle to the device \\.\aswSnx ... OK Summary ------- IOCTL scanning mode : Function + transfer type bf 0x82ac0000 - 0x82ac3fff Filter mode : Filter disabled Symbolic Device Name : \\.\aswSnx Device Type : 0x000082ac Device handle : 0x000007dc [~] Bruteforce function code + transfer type and determine input sizes... ................ [+] 11 valid IOCTL have been found Valid IOCTLs found ------------------ 0x82ac0204 function code: 0x0081 transfer type: METHOD_BUFFERED input bufsize: fixed size = 240 (0xf0) 0x82ac00cc function code: 0x0033 transfer type: METHOD_BUFFERED input bufsize: min = 4 (0x4) | max = 4096 (0x1000) [...] [?] Choose an IOCTL to fuzz...  0x82ac0204  0x82ac00cc  0x82ac0098  0x82ac0074  0x82ac0070  0x82ac0068  0x82ac0064  0x82ac0060  0x82ac0058  0x82ac0054  0x82ac0014 Choice : 0 FuzZing IOCTL 0x82ac0204 ------------------------ [0x82ac0204] Checking for trivial kernel overflows ... ................DONE [0x82ac0204] Fuzzing with predetermined DWORDs, max buffer size... (Ctrl+C to pass to the next step) [...] ===================================================================== Building from sources ===================================================================== 1. Go to the directory .\src\ 2. Edit the file "makefile.txt" (set correct API directories "API_DIRx") and the PATH in the file "build.bat" 3. Execute ".\build.bat release"