AssemblyNameInfo fuzzer (dotnet#107195)

* add initial AssemblyNameInfo Fuzzer

* fix the first bug that it has discovered

Author: adamsitnik

eng/pipelines/libraries/fuzzing/deploy-to-onefuzz.yml

@@ -65,6 +65,14 @@ extends:
 #         displayName: Send to OneFuzz
 
 # ONEFUZZ_TASK_WORKAROUND_START
+        - task: onefuzz-task@0
+          inputs:
+            onefuzzOSes: 'Windows'
+          env:
+            onefuzzDropDirectory: $(fuzzerProject)/deployment/AssemblyNameInfoFuzzer
+            SYSTEM_ACCESSTOKEN: $(System.AccessToken)
+          displayName: Send AssemblyNameInfoFuzzer to OneFuzz
+
         - task: onefuzz-task@0
           inputs:
             onefuzzOSes: 'Windows'

src/libraries/Fuzzing/DotnetFuzzing/Fuzzers/AssemblyNameInfoFuzzer.cs

@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Buffers;
+using System.Reflection.Metadata;
+using System.Runtime.InteropServices;
+
+namespace DotnetFuzzing.Fuzzers
+{
+    internal sealed class AssemblyNameInfoFuzzer : IFuzzer
+    {
+        public string[] TargetAssemblies => ["System.Reflection.Metadata"];
+
+        public string[] TargetCoreLibPrefixes => [];
+
+        public void FuzzTarget(ReadOnlySpan<byte> bytes)
+        {
+            ReadOnlySpan<char> chars = MemoryMarshal.Cast<byte, char>(bytes);
+
+            using PooledBoundedMemory<char> inputPoisonedBefore = PooledBoundedMemory<char>.Rent(chars, PoisonPagePlacement.Before);
+            using PooledBoundedMemory<char> inputPoisonedAfter = PooledBoundedMemory<char>.Rent(chars, PoisonPagePlacement.After);
+
+            Test(inputPoisonedBefore);
+            Test(inputPoisonedAfter);
+        }
+
+        private static void Test(PooledBoundedMemory<char> inputPoisoned)
+        {
+            bool shouldSucceed = AssemblyNameInfo.TryParse(inputPoisoned.Span, out _);
+
+            try
+            {
+                AssemblyNameInfo.Parse(inputPoisoned.Span);
+            }
+            catch (ArgumentException)
+            {
+                Assert.Equal(false, shouldSucceed);
+                return;
+            }
+
+            Assert.Equal(true, shouldSucceed);
+        }
+    }
+}

src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/AssemblyNameInfo.cs

@@ -193,7 +193,7 @@ public static AssemblyNameInfo Parse(ReadOnlySpan<char> assemblyName)
         public static bool TryParse(ReadOnlySpan<char> assemblyName, [NotNullWhen(true)] out AssemblyNameInfo? result)
         {
             AssemblyNameParser.AssemblyNameParts parts = default;
-            if (AssemblyNameParser.TryParse(assemblyName, ref parts))
+            if (!assemblyName.IsEmpty && AssemblyNameParser.TryParse(assemblyName, ref parts))
             {
                 result = new(parts);
                 return true;

src/libraries/System.Reflection.Metadata/tests/Metadata/AssemblyNameInfoTests.cs

@@ -98,6 +98,13 @@ public void RetargetableIsPropagated()
         public void EscapedSquareBracketIsNotAllowedInTheName()
             => Assert.False(AssemblyNameInfo.TryParse("Esc\\[aped".AsSpan(), out _));
 
+        [Fact]
+        public void EmptyInputIsInvalid()
+        {
+            Assert.False(AssemblyNameInfo.TryParse("".AsSpan(), out _));
+            Assert.Throws<ArgumentException>(() => AssemblyNameInfo.Parse("".AsSpan()));
+        }
+
         static void Roundtrip(AssemblyName source)
         {
             AssemblyNameInfo parsed = AssemblyNameInfo.Parse(source.FullName.AsSpan());