UA-.NETStandard/Fuzzing/Common/Fuzz.Tests/FuzzTargetTestsBase.cs

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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using NUnit.Framework;
using Opc.Ua.Tests;

namespace Opc.Ua.Fuzzing
{
    [TestFixture]
    [Category("Fuzzing")]
    public abstract class FuzzTargetTestsBase
    {
        public static readonly TestcaseAsset[] GoodTestcases =
        [
            .. AssetCollection<TestcaseAsset>.CreateFromFiles(
                TestUtils.EnumerateTestAssets("Testcases", "*.*"))
        ];

        public static readonly TestcaseAsset[] CrashAssets =
        [
            .. AssetCollection<TestcaseAsset>.CreateFromFiles(
                TestUtils.EnumerateTestAssets("Assets", "crash*.*"))
        ];

        public static readonly TestcaseAsset[] TimeoutAssets =
        [
            .. AssetCollection<TestcaseAsset>.CreateFromFiles(
                TestUtils.EnumerateTestAssets("Assets", "timeout*.*"))
        ];

        public static readonly TestcaseAsset[] SlowAssets =
        [
            .. AssetCollection<TestcaseAsset>.CreateFromFiles(
                TestUtils.EnumerateTestAssets("Assets", "slow*.*"))
        ];

        [DatapointSource]
        public static readonly string[] TestcaseEncoderSuffixes =
            TestUtils.DiscoverTestcaseEncoderSuffixes("Testcases");

        protected abstract Type FuzzableCodeType { get; }

        public delegate void LibFuzzTemplate(ReadOnlySpan<byte> span);

        [Theory]
        public void FuzzGoodTestcases(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(GoodTestcases))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        [Theory]
        public void FuzzEmptyByteArray(FuzzTargetFunction fuzzableCode)
        {
            FuzzTarget(fuzzableCode, []);
        }

        [Theory]
        public void FuzzCrashAssets(FuzzTargetFunction fuzzableCode)
        {
            var failures = new List<string>();
            foreach (TestcaseAsset messageEncoder in CrashAssets)
            {
                try
                {
                    TestContext.Out.WriteLine(messageEncoder);
                    FuzzTarget(fuzzableCode, messageEncoder.Testcase);
                }
                catch (Exception ex)
                {
                    failures.Add(
                        $"asset={messageEncoder} -> {ex.GetType().Name}: {ex.Message}");
                    TestContext.Error.WriteLine($"Failed: {messageEncoder}\n{ex}");
                }
            }

            // A crash asset under Assets/crash*.* is by definition an input that
            // already produced an unhandled exception in a prior libfuzzer run.
            // The contract is: once the regression has been fixed in the fuzz
            // target (or the matching producer/decoder), replaying the asset
            // through the target must NOT throw any more. The asset's continued
            // existence in the tree therefore acts as a permanent regression
            // gate. See https://github.com/OPCFoundation/UA-.NETStandard/issues/3546
            // for the historical context that flipped this from
            // log-and-swallow to assert-and-fail.
            Assert.That(
                failures,
                Is.Empty,
                "One or more crash assets reproduced under target " +
                $"'{fuzzableCode.MethodInfo.Name}'. Each surfaced bug must be " +
                "fixed (in the decoder/encoder/parser/whitelist) before the " +
                "corresponding asset is left in place. Failures:" +
                Environment.NewLine +
                string.Join(Environment.NewLine, failures));
        }

        [Theory]
        [CancelAfter(1000)]
        public void FuzzTimeoutAssets(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(TimeoutAssets))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        [Theory]
        [CancelAfter(1000)]
        public void FuzzSlowAssets(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(SlowAssets))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        protected static FuzzTargetFunction[] CreateFuzzTargetFunctions(Type fuzzableCodeType)
        {
            return
            [
                .. fuzzableCodeType
                    .GetMethods(BindingFlags.Static | BindingFlags.Public)
                    .Where(f => f.GetParameters().Length == 1)
                    .Select(f => new FuzzTargetFunction(f))
            ];
        }

        protected virtual void OnFuzzTargetSetup(ITelemetryContext telemetry)
        {
        }

        private void FuzzTarget(FuzzTargetFunction fuzzableCode, byte[] blob)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            OnFuzzTargetSetup(telemetry);

            ParameterInfo[] parameters = fuzzableCode.MethodInfo.GetParameters();
            if (parameters.Length != 1)
            {
                throw new InvalidOperationException(
                    "Fuzzable function must have exactly one parameter.");
            }
            if (parameters[0].ParameterType == typeof(string))
            {
                string text = Encoding.UTF8.GetString(blob);
                _ = fuzzableCode.MethodInfo.Invoke(null, [text]);
            }
            else if (typeof(Stream).IsAssignableFrom(parameters[0].ParameterType))
            {
                using var stream = new MemoryStream(blob);
                _ = fuzzableCode.MethodInfo.Invoke(null, [stream]);
            }
            else if (parameters[0].ParameterType == typeof(ReadOnlySpan<byte>))
            {
                var span = new ReadOnlySpan<byte>(blob);
#if NET8_0_OR_GREATER || NETSTANDARD2_1_OR_GREATER
                LibFuzzTemplate fuzzFunction = fuzzableCode.MethodInfo
                    .CreateDelegate<LibFuzzTemplate>();
#else
                var fuzzFunction = (LibFuzzTemplate)fuzzableCode.MethodInfo
                    .CreateDelegate(typeof(LibFuzzTemplate));
#endif
                fuzzFunction(span);
            }
        }
    }
}