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Add magic bytes validation for Mach-O binaries in DotnetHostHelper #15230

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Merged
merged 2 commits into from
Jul 17, 2025
Merged

Add magic bytes validation for Mach-O binaries in DotnetHostHelper #15230

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Copilot Jul 17, 2025
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Add magic bytes validation for Mach-O binaries in DotnetHostHelper
Copilot Jul 17, 2025
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15 changes: 15 additions & 0 deletions src/Microsoft.TestPlatform.CoreUtilities/Helpers/DotnetHostHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,13 @@ public class DotnetHostHelper : IDotnetHostHelper
{
public const string MONOEXENAME = "mono";

// Mach-O magic numbers from https://en.wikipedia.org/wiki/Mach-O
private const uint MachOMagic32BigEndian = 0xfeedface; // 32-bit big-endian
private const uint MachOMagic64BigEndian = 0xfeedfacf; // 64-bit big-endian
private const uint MachOMagic32LittleEndian = 0xcefaedfe; // 32-bit little-endian
private const uint MachOMagic64LittleEndian = 0xcffaedfe; // 64-bit little-endian
private const uint MachOMagicFatBigEndian = 0xcafebabe; // Multi-architecture big-endian

private readonly IFileHelper _fileHelper;
private readonly IEnvironment _environment;
private readonly IWindowsRegistryHelper _windowsRegistryHelper;
Expand Down Expand Up @@ -414,6 +421,14 @@ public bool TryGetDotnetPathByArchitecture(
ReadExactly(headerReader, cpuInfoBytes, 0, cpuInfoBytes.Length);

var magic = BitConverter.ToUInt32(magicBytes, 0);

// Validate magic bytes to ensure this is a valid Mach-O binary
if (magic is not (MachOMagic32BigEndian or MachOMagic64BigEndian or MachOMagic32LittleEndian or MachOMagic64LittleEndian or MachOMagicFatBigEndian))
{
EqtTrace.Error($"DotnetHostHelper.GetMuxerArchitectureByMachoOnMac: Invalid Mach-O magic bytes: 0x{magic:X8}");
return null;
}

var cpuInfo = BitConverter.ToUInt32(cpuInfoBytes, 0);
PlatformArchitecture? architecture = (MacOsCpuType)cpuInfo switch
{
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