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[IIS] Manually parse exe bitness #61894

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Merged
merged 3 commits into from
May 20, 2025
Merged

[IIS] Manually parse exe bitness #61894

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[IIS] Manually parse exe bitness
BrennanConroy May 12, 2025
a52751b
init
BrennanConroy May 14, 2025
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BrennanConroy May 19, 2025
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70 changes: 59 additions & 11 deletions src/Servers/IIS/AspNetCoreModuleV2/CommonLib/HostFxrResolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -197,7 +197,7 @@ HostFxrResolver::TryGetHostFxrPath(
size_t size = MAX_PATH * 2;
hostfxrPath.resize(size);

get_hostfxr_parameters params;
get_hostfxr_parameters params{};
params.size = sizeof(get_hostfxr_parameters);
params.assembly_path = applicationPath.c_str();
params.dotnet_root = dotnetRoot.c_str();
Expand Down Expand Up @@ -393,7 +393,7 @@ HostFxrResolver::GetAbsolutePathToDotnetFromHostfxr(const fs::path& hostfxrPath)
// Tries to call where.exe to find the location of dotnet.exe.
// Will check that the bitness of dotnet matches the current
// worker process bitness.
// Returns true if a valid dotnet was found, else false.R
// Returns true if a valid dotnet was found, else false.
//
std::optional<fs::path>
HostFxrResolver::InvokeWhereToFindDotnet()
Expand All @@ -416,7 +416,6 @@ HostFxrResolver::InvokeWhereToFindDotnet()
STRU struDotnetSubstring;
STRU struDotnetLocationsString;
DWORD dwNumBytesRead = 0;
DWORD dwBinaryType = 0;
INT index = 0;
INT prevIndex = 0;
std::optional<fs::path> result;
Expand Down Expand Up @@ -521,14 +520,7 @@ HostFxrResolver::InvokeWhereToFindDotnet()

LOG_INFOF(L"Processing entry '%ls'", struDotnetSubstring.QueryStr());

if (LOG_LAST_ERROR_IF(!GetBinaryTypeW(struDotnetSubstring.QueryStr(), &dwBinaryType)))
{
continue;
}

LOG_INFOF(L"Binary type %d", dwBinaryType);

if (fIsCurrentProcess64Bit == (dwBinaryType == SCS_64BIT_BINARY))
if (fIsCurrentProcess64Bit == IsX64(struDotnetSubstring.QueryStr()))
{
// The bitness of dotnet matched with the current worker process bitness.
return std::make_optional(struDotnetSubstring.QueryStr());
Expand All @@ -539,6 +531,62 @@ HostFxrResolver::InvokeWhereToFindDotnet()
return result;
}

BOOL HostFxrResolver::IsX64(const WCHAR* dotnetPath)
{
// Errors while reading from the file shouldn't throw unless
// file.exception(bits) is set
std::ifstream file(dotnetPath, std::ios::binary);
if (!file.is_open())
{
LOG_TRACEF(L"Failed to open file %ls", dotnetPath);
return false;
}

// Read the DOS header
IMAGE_DOS_HEADER dosHeader{};
file.read(reinterpret_cast<char*>(&dosHeader), sizeof(dosHeader));
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Copilot AI May 13, 2025

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Consider verifying that the file.read operation successfully read the expected number of bytes for the DOS header to handle cases of incomplete or corrupted files.

Suggested change
file.read(reinterpret_cast<char*>(&dosHeader), sizeof(dosHeader));
if (!file.read(reinterpret_cast<char*>(&dosHeader), sizeof(dosHeader)))
{
LOG_INFOF(L"Failed to read DOS header from %ls", dotnetPath);
return false;
}

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Doesn't seem too interesting, worst case there is nothing left to read and dosHeader.e_magic will be zero and not match IMAGE_DOS_SIGNATURE.

if (dosHeader.e_magic != IMAGE_DOS_SIGNATURE) // 'MZ'
{
LOG_TRACEF(L"%ls is not a valid executable file (missing MZ header).", dotnetPath);
return false;
}

// Seek to the PE header
file.seekg(dosHeader.e_lfanew, std::ios::beg);
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Check the result of file.seekg to ensure that the PE header offset is valid before proceeding with reading the PE header.

Suggested change
file.seekg(dosHeader.e_lfanew, std::ios::beg);
file.seekg(dosHeader.e_lfanew, std::ios::beg);
if (file.fail())
{
LOG_INFOF(L"Failed to seek to PE header in file %ls. Invalid e_lfanew offset: %ld", dotnetPath, dosHeader.e_lfanew);
return false;
}

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Same here, not interesting.

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Assuming something interesting does happen here, what does the failure mode look like? Does something higher up handle the exception gracefully?


// Read the PE header
DWORD peSignature{};
file.read(reinterpret_cast<char*>(&peSignature), sizeof(peSignature));
if (peSignature != IMAGE_NT_SIGNATURE) // 'PE\0\0'
{
LOG_TRACEF(L"%ls is not a valid PE file (missing PE header).", dotnetPath);
return false;
}

// Read the file header
IMAGE_FILE_HEADER fileHeader{};
file.read(reinterpret_cast<char*>(&fileHeader), sizeof(fileHeader));

// Read the optional header magic field
WORD magic{};
file.read(reinterpret_cast<char*>(&magic), sizeof(magic));

// Determine the architecture based on the magic value
if (magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC)
{
LOG_INFOF(L"%ls is 32-bit", dotnetPath);
return false;
}
else if (magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC)
{
LOG_INFOF(L"%ls is 64-bit", dotnetPath);
return true;
}

LOG_INFOF(L"%ls is unknown architecture %i", dotnetPath, fileHeader.Machine);
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? include the magic

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Magic only really has 3 values. So by default this is the 3rd case so won't have an interesting value to log.

return false;
}

std::optional<fs::path>
HostFxrResolver::GetAbsolutePathToDotnetFromProgramFiles()
{
Expand Down
2 changes: 2 additions & 0 deletions src/Servers/IIS/AspNetCoreModuleV2/CommonLib/HostFxrResolver.h
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,8 @@ class HostFxrResolver
const std::filesystem::path & requestedPath
);

static BOOL IsX64(const WCHAR* dotnetPath);

struct LocalFreeDeleter
{
void operator ()(_In_ LPWSTR* ptr) const
Expand Down
2 changes: 1 addition & 1 deletion src/Servers/IIS/build/Build.Lib.Settings
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Expand Up @@ -9,7 +9,7 @@

<ItemDefinitionGroup>
<ClCompile>
<SDLCheck>false</SDLCheck>
<SDLCheck>true</SDLCheck>
<PreprocessorDefinitions>_LIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
<ConformanceMode>true</ConformanceMode>
</ClCompile>
Expand Down
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