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[release/8.0-rc2] Make HostModel PEUtils always read/write little endian #92441

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merged 2 commits into from
Sep 22, 2023
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[release/8.0-rc2] Make HostModel PEUtils always read/write little endian #92441

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0566e7d
Make HostModel PEUtils always read/write little endian
elinor-fung Sep 21, 2023
d39f18e
PR feeback - helper methods
elinor-fung Sep 21, 2023
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121 changes: 39 additions & 82 deletions src/installer/managed/Microsoft.NET.HostModel/AppHost/PEUtils.cs
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Original file line number Diff line number Diff line change
@@ -1,8 +1,11 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Buffers.Binary;
using System.IO;
using System.IO.MemoryMappedFiles;
using System.Reflection.PortableExecutable;

namespace Microsoft.NET.HostModel.AppHost
{
Expand All @@ -15,29 +18,13 @@ public static class PEUtils
/// <returns>true if the accessor represents a PE image, false otherwise.</returns>
internal static unsafe bool IsPEImage(MemoryMappedViewAccessor accessor)
{
byte* pointer = null;
if (accessor.Capacity < PEOffsets.DosStub.PESignatureOffset + sizeof(uint))
return false;

try
{
accessor.SafeMemoryMappedViewHandle.AcquirePointer(ref pointer);
byte* bytes = pointer + accessor.PointerOffset;

// https://en.wikipedia.org/wiki/Portable_Executable
// Validate that we're looking at Windows PE file
if (((ushort*)bytes)[0] != PEOffsets.DosImageSignature
|| accessor.Capacity < PEOffsets.DosStub.PESignatureOffset + sizeof(uint))
{
return false;
}
return true;
}
finally
{
if (pointer != null)
{
accessor.SafeMemoryMappedViewHandle.ReleasePointer();
}
}
// https://en.wikipedia.org/wiki/Portable_Executable
// Validate that we're looking at Windows PE file
ushort signature = AsLittleEndian(accessor.ReadUInt16(0));
return signature == PEOffsets.DosImageSignature;
}

public static bool IsPEImage(string filePath)
Expand All @@ -60,40 +47,15 @@ public static bool IsPEImage(string filePath)
/// <param name="accessor">The memory accessor which has the apphost file opened.</param>
internal static unsafe void SetWindowsGraphicalUserInterfaceBit(MemoryMappedViewAccessor accessor)
{
byte* pointer = null;

try
{
accessor.SafeMemoryMappedViewHandle.AcquirePointer(ref pointer);
byte* bytes = pointer + accessor.PointerOffset;

// https://en.wikipedia.org/wiki/Portable_Executable
uint peHeaderOffset = ((uint*)(bytes + PEOffsets.DosStub.PESignatureOffset))[0];

if (accessor.Capacity < peHeaderOffset + PEOffsets.PEHeader.Subsystem + sizeof(ushort))
{
throw new AppHostNotPEFileException("Subsystem offset out of file range.");
}

ushort* subsystem = ((ushort*)(bytes + peHeaderOffset + PEOffsets.PEHeader.Subsystem));

// https://docs.microsoft.com/en-us/windows/desktop/Debug/pe-format#windows-subsystem
// The subsystem of the prebuilt apphost should be set to CUI
if (subsystem[0] != (ushort)PEOffsets.Subsystem.WindowsCui)
{
throw new AppHostNotCUIException(subsystem[0]);
}

// Set the subsystem to GUI
subsystem[0] = (ushort)PEOffsets.Subsystem.WindowsGui;
}
finally
{
if (pointer != null)
{
accessor.SafeMemoryMappedViewHandle.ReleasePointer();
}
}
// https://learn.microsoft.com/windows/win32/debug/pe-format#windows-subsystem
// The subsystem of the prebuilt apphost should be set to CUI
uint peHeaderOffset;
ushort subsystem = GetWindowsSubsystem(accessor, out peHeaderOffset);
if (subsystem != (ushort)Subsystem.WindowsCui)
throw new AppHostNotCUIException(subsystem);

// Set the subsystem to GUI
accessor.Write(peHeaderOffset + PEOffsets.PEHeader.Subsystem, AsLittleEndian((ushort)Subsystem.WindowsGui));
}

public static unsafe void SetWindowsGraphicalUserInterfaceBit(string filePath)
Expand All @@ -113,32 +75,7 @@ public static unsafe void SetWindowsGraphicalUserInterfaceBit(string filePath)
/// <param name="accessor">The memory accessor which has the apphost file opened.</param>
internal static unsafe ushort GetWindowsGraphicalUserInterfaceBit(MemoryMappedViewAccessor accessor)
{
byte* pointer = null;

try
{
accessor.SafeMemoryMappedViewHandle.AcquirePointer(ref pointer);
byte* bytes = pointer + accessor.PointerOffset;

// https://en.wikipedia.org/wiki/Portable_Executable
uint peHeaderOffset = ((uint*)(bytes + PEOffsets.DosStub.PESignatureOffset))[0];

if (accessor.Capacity < peHeaderOffset + PEOffsets.PEHeader.Subsystem + sizeof(ushort))
{
throw new AppHostNotPEFileException("Subsystem offset out of file range.");
}

ushort* subsystem = ((ushort*)(bytes + peHeaderOffset + PEOffsets.PEHeader.Subsystem));

return subsystem[0];
}
finally
{
if (pointer != null)
{
accessor.SafeMemoryMappedViewHandle.ReleasePointer();
}
}
return GetWindowsSubsystem(accessor, out _);
}

public static unsafe ushort GetWindowsGraphicalUserInterfaceBit(string filePath)
Expand All @@ -151,5 +88,25 @@ public static unsafe ushort GetWindowsGraphicalUserInterfaceBit(string filePath)
}
}
}

private static ushort GetWindowsSubsystem(MemoryMappedViewAccessor accessor, out uint peHeaderOffset)
{
// https://en.wikipedia.org/wiki/Portable_Executable
if (accessor.Capacity < PEOffsets.DosStub.PESignatureOffset + sizeof(uint))
throw new AppHostNotPEFileException("PESignature offset out of file range.");

peHeaderOffset = AsLittleEndian(accessor.ReadUInt32(PEOffsets.DosStub.PESignatureOffset));
if (accessor.Capacity < peHeaderOffset + PEOffsets.PEHeader.Subsystem + sizeof(ushort))
throw new AppHostNotPEFileException("Subsystem offset out of file range.");

// https://learn.microsoft.com/windows/win32/debug/pe-format#windows-subsystem
return AsLittleEndian(accessor.ReadUInt16(peHeaderOffset + PEOffsets.PEHeader.Subsystem));
}

private static ushort AsLittleEndian(ushort value)
=> BitConverter.IsLittleEndian ? value : BinaryPrimitives.ReverseEndianness(value);

private static uint AsLittleEndian(uint value)
=> BitConverter.IsLittleEndian ? value : BinaryPrimitives.ReverseEndianness(value);
}
}
6 changes: 5 additions & 1 deletion ...Microsoft.NET.HostModel.Tests/Microsoft.NET.HostModel.AppHost.Tests/AppHostUpdateTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
using Microsoft.NET.HostModel.AppHost;
using Microsoft.DotNet.CoreSetup.Test;
using System.Diagnostics;
using System.Reflection.PortableExecutable;

namespace Microsoft.NET.HostModel.Tests
{
Expand Down Expand Up @@ -111,7 +112,9 @@ public void ItCanSetWindowsGUISubsystem()
BitConverter
.ToUInt16(File.ReadAllBytes(destinationFilePath), SubsystemOffset)
.Should()
.Be(2);
.Be((ushort)Subsystem.WindowsGui);

Assert.Equal((ushort)Subsystem.WindowsGui, PEUtils.GetWindowsGraphicalUserInterfaceBit(destinationFilePath));
}
}

Expand Down Expand Up @@ -153,6 +156,7 @@ public void ItFailsToSetGUISubsystemWithWrongDefault()
string destinationFilePath = Path.Combine(testDirectory.Path, "DestinationAppHost.exe.mock");
string appBinaryFilePath = "Test/App/Binary/Path.dll";

Assert.Equal(42, PEUtils.GetWindowsGraphicalUserInterfaceBit(sourceAppHostMock));
Assert.Throws<AppHostNotCUIException>(() =>
HostWriter.CreateAppHost(
sourceAppHostMock,
Expand Down