121 lines
3.7 KiB
C
121 lines
3.7 KiB
C
// Copyright (c) 1992 - 1997 Microsoft Corporation. All Rights Reserved.
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#ifndef _CHECKBMI_H_
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#define _CHECKBMI_H_
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#ifdef __cplusplus
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extern "C" {
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#endif
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// Helper
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__inline BOOL MultiplyCheckOverflow(DWORD a, DWORD b, __deref_out_range(==, a * b) DWORD *pab) {
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*pab = a * b;
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if ((a == 0) || (((*pab) / a) == b)) {
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return TRUE;
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}
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return FALSE;
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}
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// Checks if the fields in a BITMAPINFOHEADER won't generate
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// overlows and buffer overruns
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// This is not a complete check and does not guarantee code using this structure will be secure
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// from attack
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// Bugs this is guarding against:
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// 1. Total structure size calculation overflowing
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// 2. biClrUsed > 256 for 8-bit palettized content
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// 3. Total bitmap size in bytes overflowing
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// 4. biSize < size of the base structure leading to accessessing random memory
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// 5. Total structure size exceeding know size of data
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//
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__success(return != 0) __inline BOOL ValidateBitmapInfoHeader(
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const BITMAPINFOHEADER *pbmi, // pointer to structure to check
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__out_range(>=, sizeof(BITMAPINFOHEADER)) DWORD cbSize // size of memory block containing structure
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)
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{
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DWORD dwWidthInBytes;
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DWORD dwBpp;
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DWORD dwWidthInBits;
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DWORD dwHeight;
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DWORD dwSizeImage;
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DWORD dwClrUsed;
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// Reject bad parameters - do the size check first to avoid reading bad memory
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if (cbSize < sizeof(BITMAPINFOHEADER) ||
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pbmi->biSize < sizeof(BITMAPINFOHEADER) ||
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pbmi->biSize > 4096) {
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return FALSE;
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}
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// Reject 0 size
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if (pbmi->biWidth == 0 || pbmi->biHeight == 0) {
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return FALSE;
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}
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// Use bpp of 200 for validating against further overflows if not set for compressed format
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dwBpp = 200;
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if (pbmi->biBitCount > dwBpp) {
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return FALSE;
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}
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// Strictly speaking abs can overflow so cast explicitly to DWORD
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dwHeight = (DWORD)abs(pbmi->biHeight);
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if (!MultiplyCheckOverflow(dwBpp, (DWORD)pbmi->biWidth, &dwWidthInBits)) {
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return FALSE;
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}
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// Compute correct width in bytes - rounding up to 4 bytes
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dwWidthInBytes = (dwWidthInBits / 8 + 3) & ~3;
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if (!MultiplyCheckOverflow(dwWidthInBytes, dwHeight, &dwSizeImage)) {
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return FALSE;
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}
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// Fail if total size is 0 - this catches indivual quantities being 0
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// Also don't allow huge values > 1GB which might cause arithmetic
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// errors for users
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if (dwSizeImage > 0x40000000 ||
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pbmi->biSizeImage > 0x40000000) {
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return FALSE;
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}
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// Fail if biClrUsed looks bad
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if (pbmi->biClrUsed > 256) {
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return FALSE;
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}
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if (pbmi->biClrUsed == 0 && pbmi->biBitCount <= 8 && pbmi->biBitCount > 0) {
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dwClrUsed = (1 << pbmi->biBitCount);
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} else {
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dwClrUsed = pbmi->biClrUsed;
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}
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// Check total size
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if (cbSize < pbmi->biSize + dwClrUsed * sizeof(RGBQUAD) +
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(pbmi->biCompression == BI_BITFIELDS ? 3 * sizeof(DWORD) : 0)) {
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return FALSE;
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}
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// If it is RGB validate biSizeImage - lots of code assumes the size is correct
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if (pbmi->biCompression == BI_RGB || pbmi->biCompression == BI_BITFIELDS) {
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if (pbmi->biSizeImage != 0) {
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DWORD dwBits = (DWORD)pbmi->biWidth * (DWORD)pbmi->biBitCount;
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DWORD dwWidthInBytes = ((DWORD)((dwBits+31) & (~31)) / 8);
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DWORD dwTotalSize = (DWORD)abs(pbmi->biHeight) * dwWidthInBytes;
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if (dwTotalSize > pbmi->biSizeImage) {
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return FALSE;
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}
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}
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}
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return TRUE;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif // _CHECKBMI_H_
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