Add GoodBad C# example project, integration test (#2148)

.github/workflows/ci.yml

@@ -524,6 +524,11 @@ jobs:
           (cd libfuzzer-aarch64-crosscompile; make)
           cp -r libfuzzer-aarch64-crosscompile/fuzz.exe libfuzzer-aarch64-crosscompile/inputs artifacts/linux-libfuzzer-aarch64-crosscompile
 
+          # C# target.
+          sudo apt-get install -y dotnet-sdk-6.0
+          (cd GoodBad; dotnet publish -c Release -o out)
+          mv GoodBad/out artifacts/GoodBadDotnet
+
     - uses: actions/upload-artifact@v2.2.2
       with:
         name: integration-test-artifacts
@@ -603,3 +608,36 @@ jobs:
       with:
         name: integration-test-artifacts
         path: src/integration-tests/artifacts
+  integration-tests-linux:
+    runs-on: ubuntu-18.04
+    needs:
+      - build-integration-tests-linux
+      - dotnet-fuzzing-tools-linux
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/download-artifact@v2.0.8
+        with:
+          name: build-artifacts
+          path: build-artifacts
+      - uses: actions/download-artifact@v2.0.8
+        with:
+          name: integration-test-artifacts
+          path: integration-test-artifacts
+      - name: test
+        shell: bash
+        run: |
+          set -ex -o pipefail
+
+          # Must be absolute paths.
+          export GOODBAD_DOTNET="${GITHUB_WORKSPACE}/integration-test-artifacts/GoodBadDotnet"
+
+          export LIBFUZZER_DOTNET="${GITHUB_WORKSPACE}/build-artifacts/third-party/dotnet-fuzzing-linux/libfuzzer-dotnet/libfuzzer-dotnet"
+          chmod +x $LIBFUZZER_DOTNET
+
+          export LIBFUZZER_DOTNET_LOADER="${GITHUB_WORKSPACE}/build-artifacts/third-party/dotnet-fuzzing-linux/LibFuzzerDotnetLoader/LibFuzzerDotnetLoader"
+          chmod +x $LIBFUZZER_DOTNET_LOADER
+
+          export SHARPFUZZ="${GITHUB_WORKSPACE}/build-artifacts/third-party/dotnet-fuzzing-linux/sharpfuzz/SharpFuzz.CommandLine"
+          chmod +x $SHARPFUZZ
+
+          ./src/ci/test-libfuzzer-dotnet.sh

src/ci/test-libfuzzer-dotnet.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+set -ex -o pipefail
+
+# Required environment variables:
+# - GOODBAD_DOTNET
+# - LIBFUZZER_DOTNET
+# - LIBFUZZER_DOTNET_LOADER
+# - SHARPFUZZ
+
+export GOODBAD_DLL='GoodBad/GoodBad.dll'
+
+TMP=$(mktemp -d)
+cd $TMP
+
+cp -r ${GOODBAD_DOTNET} GoodBad
+
+# Instrument DLL under test.
+${SHARPFUZZ} GoodBad/GoodBad.dll
+
+# Create seed and crash inputs.
+printf 'good' > good.txt
+printf 'bad!' > bad.txt
+
+# Test individual env vars.
+export LIBFUZZER_DOTNET_TARGET_ASSEMBLY="${GOODBAD_DLL}"
+export LIBFUZZER_DOTNET_TARGET_CLASS='GoodBad.Fuzzer'
+export LIBFUZZER_DOTNET_TARGET_METHOD='TestInput'
+
+${LIBFUZZER_DOTNET} --target_path=${LIBFUZZER_DOTNET_LOADER} good.txt
+
+# Expect nonzero exit.
+! ${LIBFUZZER_DOTNET} --target_path=${LIBFUZZER_DOTNET_LOADER} bad.txt
+
+# Test delimited env var.
+export LIBFUZZER_DOTNET_TARGET="${LIBFUZZER_DOTNET_TARGET_ASSEMBLY}:${LIBFUZZER_DOTNET_TARGET_CLASS}:${LIBFUZZER_DOTNET_TARGET_METHOD}"
+unset LIBFUZZER_DOTNET_TARGET_ASSEMBLY
+unset LIBFUZZER_DOTNET_TARGET_CLASS
+unset LIBFUZZER_DOTNET_TARGET_METHOD
+
+${LIBFUZZER_DOTNET} --target_path=${LIBFUZZER_DOTNET_LOADER} good.txt
+
+# Expect nonzero exit.
+! ${LIBFUZZER_DOTNET} --target_path=${LIBFUZZER_DOTNET_LOADER} bad.txt
+
+rm -rf $TMP

src/integration-tests/GoodBad/GoodBad.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace GoodBad;
+
+public class BinaryParser
+{
+    int count = 0;
+
+    public void ProcessInput(ReadOnlySpan<byte> data) {
+        if (data.Length < 4) {
+            return;
+        }
+
+        if (data[0] == 'b') { count++; }
+        if (data[1] == 'a') { count++; }
+        if (data[2] == 'd') { count++; }
+        if (data[3] == '!') { count++; }
+
+        // Simulate an out-of-bounds access while parsing.
+        if (count >= 4) {
+            var _ = data[0xdead];
+        }
+    }
+}
+
+public class Fuzzer {
+    /// Preferred test method.
+    public static void TestInput(ReadOnlySpan<byte> data) {
+            var parser = new BinaryParser();
+            parser.ProcessInput(data);
+    }
+
+    /// Backwards-compatible test method for legacy code that can't use `Span` types.
+    ///
+    /// Incurs an extra copy of `data` per fuzzing iteration.
+    public static void TestInputCompat(byte[] data) {
+            var parser = new BinaryParser();
+            parser.ProcessInput(data);
+    }
+
+    /// Invalid static method that has a fuzzing-incompatible signature.
+    public static void BadSignature(ReadOnlySpan<int> data) {
+        return;
+    }
+}

src/integration-tests/GoodBad/GoodBad.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <LangVersion>10.0</LangVersion>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>