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Harden dbgutil Windows PE export walk against corrupted or incomplete module data #131363

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Harden dbgutil Windows PE export walk against corrupted or incomplete module data #131363

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19 changes: 17 additions & 2 deletions src/coreclr/debug/dbgutil/dbgutil.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -446,12 +446,21 @@ HRESULT ReadFromDataTarget(ICorDebugDataTarget* pDataTarget,
extern "C" bool
TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char* symbolName, uint64_t* symbolAddress)
{
*symbolAddress = 0;

DWORD exportTableRva;
Comment on lines 447 to 451
if (FAILED(GetMachineAndDirectoryAddress(dataTarget, baseAddress, IMAGE_DIRECTORY_ENTRY_EXPORT, nullptr, &exportTableRva)))
{
return false;
}

// A module with no export directory reports a zero RVA here; there is nothing to search and
// reading at baseAddress would parse the PE headers as an IMAGE_EXPORT_DIRECTORY.
if (exportTableRva == 0)
{
return false;
}

// Manually read the export directory from the target to find the requested symbol.
IMAGE_EXPORT_DIRECTORY exportDir{};
if (FAILED(ReadFromDataTarget(dataTarget, baseAddress + exportTableRva, (BYTE*)&exportDir, sizeof(exportDir))))
Expand All @@ -460,6 +469,7 @@ TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char*
}

uint32_t namePointerCount = VAL32(exportDir.NumberOfNames);
uint32_t exportAddressCount = VAL32(exportDir.NumberOfFunctions);
uint32_t addressTableRVA = VAL32(exportDir.AddressOfFunctions);
uint32_t ordinalTableRVA = VAL32(exportDir.AddressOfNameOrdinals);
uint32_t nameTableRVA = VAL32(exportDir.AddressOfNames);
Expand All @@ -481,7 +491,7 @@ TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char*
}
// Allocate a buffer for the memory that we'll read out of the target image.
// We can allocate as much space as the target symbol name as we gracefully handle reading
// inaccessable memory.
// inaccessible memory.
std::unique_ptr<char[]> namePointer(new char[symbolNameLength + 1]);
// If we fail to read the memory or the name doesn't match, then we don't have the right export.
if (SUCCEEDED(ReadFromDataTarget(dataTarget, baseAddress + namePointerRVA, (BYTE*)namePointer.get(), (UINT32)symbolNameLength + 1))
Expand All @@ -493,6 +503,12 @@ TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char*
{
return false;
}
// The ordinal indexes the export address table; reject an out-of-range value from
// untrusted image data before using it to compute a read offset.
if (ordinalForNamedExport >= exportAddressCount)
{
return false;
}
// If the name matches, we should be able to get the export
uint32_t exportRVA = 0;
if (FAILED(ReadFromDataTarget(dataTarget, baseAddress + addressTableRVA + sizeof(uint32_t) * ordinalForNamedExport, (BYTE*)&exportRVA, sizeof(exportRVA))))
Expand All @@ -505,7 +521,6 @@ TryGetSymbol(ICorDebugDataTarget* dataTarget, uint64_t baseAddress, const char*
}
}

*symbolAddress = 0;
return false;
}
#endif
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