Use managed Mach-O signer on non-Mac hosts

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets

@@ -803,7 +803,7 @@ Copyright (c) .NET Foundation. All rights reserved.
           Condition="'$(UseAppHost)' == 'true' and '$(_IsExecutable)' == 'true'">
     <PropertyGroup>
       <_UseWindowsGraphicalUserInterface Condition="($(RuntimeIdentifier.StartsWith('win')) or $(DefaultAppHostRuntimeIdentifier.StartsWith('win'))) and '$(OutputType)'=='WinExe'">true</_UseWindowsGraphicalUserInterface>
-      <_EnableMacOSCodeSign Condition="'$(_EnableMacOSCodeSign)' == '' and $([MSBuild]::IsOSPlatform(`OSX`)) and Exists('/usr/bin/codesign') and
+      <_EnableMacOSCodeSign Condition="'$(_EnableMacOSCodeSign)' == '' and
                                       ($(RuntimeIdentifier.StartsWith('osx')) or $(AppHostRuntimeIdentifier.StartsWith('osx')))">true</_EnableMacOSCodeSign>
       <_UseSingleFileHostForPublish Condition="'$(PublishSingleFile)' == 'true' and
                                                '$(SelfContained)' == 'true' and

test/Microsoft.NET.Build.Tests/AppHostTests.cs

@@ -3,6 +3,7 @@
 
 #nullable disable
 
+using System.Buffers.Binary;
 using System.Diagnostics;
 using System.Reflection.PortableExecutable;
 using System.Text.RegularExpressions;
@@ -152,71 +153,46 @@ public void It_does_not_try_to_codesign_non_osx_app_hosts(string targetFramework
             Directory.Delete(buildProjDir, true);
         }
 
-        [PlatformSpecificTheory(TestPlatforms.OSX)]
-        [InlineData("netcoreapp3.1")]
-        [InlineData("net5.0")]
-        [InlineData(ToolsetInfo.CurrentTargetFramework)]
-        public void It_codesigns_a_framework_dependent_app(string targetFramework)
-        {
-            var testAsset = _testAssetsManager
-                .CopyTestAsset("HelloWorld", identifier: targetFramework)
-                .WithSource()
-                .WithTargetFramework(targetFramework);
-
-            var buildCommand = new BuildCommand(testAsset);
-            buildCommand
-                .Execute()
-                .Should()
-                .Pass();
-
-            var outputDirectory = buildCommand.GetOutputDirectory(targetFramework);
-            var appHostFullPath = Path.Combine(outputDirectory.FullName, "HelloWorld");
-
-            // Check that the apphost is signed
-            var codesignPath = @"/usr/bin/codesign";
-            new RunExeCommand(Log, codesignPath, new string[] { "-s", "-", appHostFullPath })
-                .Execute()
-                .Should()
-                .Fail()
-                .And
-                .HaveStdErrContaining($"{appHostFullPath}: is already signed");
-        }
-
-        [PlatformSpecificTheory(TestPlatforms.OSX)]
-        [InlineData("netcoreapp3.1", false)]
-        [InlineData("netcoreapp3.1", true)]
-        [InlineData("net5.0", false)]
-        [InlineData("net5.0", true)]
-        [InlineData(ToolsetInfo.CurrentTargetFramework, false)]
-        [InlineData(ToolsetInfo.CurrentTargetFramework, true)]
-        public void It_codesigns_an_app_targeting_osx(string targetFramework, bool selfContained)
+        [Theory]
+        [InlineData("net6.0", "osx-x64")]
+        [InlineData("net6.0", "osx-arm64")]
+        [InlineData(ToolsetInfo.CurrentTargetFramework, "osx-x64")]
+        [InlineData(ToolsetInfo.CurrentTargetFramework, "osx-arm64")]
+        public void It_codesigns_an_app_targeting_osx(string targetFramework, string rid)
         {
+            const string testAssetName = "HelloWorld";
             var testAsset = _testAssetsManager
-                .CopyTestAsset("HelloWorld", identifier: targetFramework, allowCopyIfPresent: true)
+                .CopyTestAsset(testAssetName, identifier: targetFramework)
                 .WithSource()
                 .WithTargetFramework(targetFramework);
 
             var buildCommand = new BuildCommand(testAsset);
-            var buildArgs = new List<string>() { $"/p:RuntimeIdentifier={RuntimeInformation.RuntimeIdentifier}" };
-            if (!selfContained)
-                buildArgs.Add("/p:PublishSingleFile=true");
-
+            var buildArgs = new List<string>() { $"/p:RuntimeIdentifier={rid}" };
             buildCommand
                 .Execute(buildArgs.ToArray())
                 .Should()
                 .Pass();
 
-            var outputDirectory = buildCommand.GetOutputDirectory(targetFramework, runtimeIdentifier: RuntimeInformation.RuntimeIdentifier);
-            var appHostFullPath = Path.Combine(outputDirectory.FullName, "HelloWorld");
+            var outputDirectory = buildCommand.GetOutputDirectory(targetFramework: targetFramework, runtimeIdentifier: rid);
+            var appHostFullPath = Path.Combine(outputDirectory.FullName, testAssetName);
 
             // Check that the apphost is signed
-            var codesignPath = @"/usr/bin/codesign";
-            new RunExeCommand(Log, codesignPath, new string[] { "-s", "-", appHostFullPath })
-                .Execute()
-                .Should()
-                .Fail()
-                .And
-                .HaveStdErrContaining($"{appHostFullPath}: is already signed");
+            HasMachOSignatureLoadCommand(new FileInfo(appHostFullPath)).Should().BeTrue();
+            // When on a Mac, use the codesign tool to verify the signature as well
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            {
+                var codesignPath = @"/usr/bin/codesign";
+                new RunExeCommand(Log, codesignPath, ["-s", "-", appHostFullPath])
+                    .Execute()
+                    .Should()
+                    .Fail()
+                    .And
+                    .HaveStdErrContaining($"{appHostFullPath}: is already signed");
+                new RunExeCommand(Log, codesignPath, ["-v", appHostFullPath])
+                    .Execute()
+                    .Should()
+                    .Pass();
+            }
         }
 
         [Theory]
@@ -511,5 +487,62 @@ private static bool IsPE32(string path)
                 return reader.PEHeaders.PEHeader.Magic == PEMagic.PE32;
             }
         }
+
+        // Reads the Mach-O load commands and returns true if an LC_CODE_SIGNATURE command is found, otherwise returns false
+        static bool HasMachOSignatureLoadCommand(FileInfo file)
+        {
+            /* Mach-O files have the following structure:
+             * 32 byte header beginning with a magic number and info about the file and load commands
+             * A series of load commands with the following structure:
+             * - 4-byte command type
+             * - 4-byte command size
+             * - variable length command-specific data
+             */
+            const uint LC_CODE_SIGNATURE = 0x1D;
+            using (var stream = file.OpenRead())
+            {
+                // Read the MachO magic number to determine endianness
+                Span<byte> eightByteBuffer = stackalloc byte[8];
+                stream.ReadExactly(eightByteBuffer);
+                // Determine if the magic number is in the same or opposite endianness as the runtime
+                bool reverseEndinanness = BitConverter.ToUInt32(eightByteBuffer.Slice(0, 4)) switch
+                {
+                    0xFEEDFACF => false,
+                    0xCFFAEDFE => true,
+                    _ => throw new InvalidOperationException("Not a 64-bit Mach-O file")
+                };
+                // 4-byte value at offset 16 is the number of load commands
+                // 4-byte value at offset 20 is the size of the load commands
+                stream.Position = 16;
+                ReadUInts(stream, eightByteBuffer, out uint loadCommandsCount, out uint loadCommandsSize);
+                // Mach-0 64 byte headers are 32 bytes long, and the first load command will be right after
+                stream.Position = 32;
+                bool hasSignature = false;
+                for (int commandIndex = 0; commandIndex < loadCommandsCount; commandIndex++)
+                {
+                    ReadUInts(stream, eightByteBuffer, out uint commandType, out uint commandSize);
+                    if (commandType == LC_CODE_SIGNATURE)
+                    {
+                        hasSignature = true;
+                    }
+                    stream.Position += commandSize - eightByteBuffer.Length;
+                }
+                Debug.Assert(stream.Position == loadCommandsSize + 32);
+                return hasSignature;
+
+                void ReadUInts(Stream stream, Span<byte> buffer, out uint val1, out uint val2)
+                {
+                    stream.ReadExactly(buffer);
+                    val1 = BitConverter.ToUInt32(buffer.Slice(0, 4));
+                    val2 = BitConverter.ToUInt32(buffer.Slice(4, 4));
+                    if (reverseEndinanness)
+                    {
+                        val1 = BinaryPrimitives.ReverseEndianness(val1);
+                        val2 = BinaryPrimitives.ReverseEndianness(val2);
+                    }
+                }
+            }
+        }
+
     }
 }