EcsJsonConfiguration - With converters to protect against bad types

src/Elastic.CommonSchema/Serialization/JsonConfiguration.cs

@@ -18,14 +18,33 @@ public static class EcsJsonConfiguration
 			PropertyNamingPolicy = new SnakeCaseJsonNamingPolicy(),
 			Converters =
 			{
-				new EcsDocumentJsonConverterFactory()
+				new EcsDocumentJsonConverterFactory(),
+				new EcsJsonStringConverter<System.Reflection.Assembly>(),	// Cannot transfer assembly-objects over the wire
+				new EcsJsonStringConverter<System.Reflection.Module>(),		// Cannot transfer module-objects over the wire
+				new EcsJsonStringConverter<System.Reflection.MemberInfo>(),	// Cannot transfer method-addresses over the wire
+				new EcsJsonStringConverter<System.Delegate>(),				// Cannot transfer methods over the wire
+				new EcsJsonStringConverter<System.IO.Stream>(),				// Stream-properties often throws exceptions
 			},
-
 		};
 
 		internal static readonly JsonConverter<DateTimeOffset> DateTimeOffsetConverter =
 			(JsonConverter<DateTimeOffset>)SerializerOptions.GetConverter(typeof(DateTimeOffset));
 
 		public static readonly EcsDocumentJsonConverter DefaultEcsDocumentJsonConverter = new();
+
+		private sealed class EcsJsonStringConverter<T> : JsonConverter<T>
+		{
+			public override bool CanConvert(Type typeToConvert) => typeof(T).IsAssignableFrom(typeToConvert);
+
+			public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) => default;
+
+			public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+			{
+				if (value is null)
+					writer.WriteNullValue();
+				else
+					writer.WriteStringValue(value.ToString());
+			}
+		}
 	}
 }

tests/Elastic.CommonSchema.NLog.Tests/MessageTests.cs

@@ -49,6 +49,41 @@ public void SeesMessageWithProp() => TestLogger((logger, getLogEvents) =>
 			y.Should().HaveValue().And.Be(2.2);
 		});
 
+		[Fact]
+		public void SeesMessageWithEvilProp() => TestLogger((logger, getLogEvents) =>
+		{
+			logger.Info("Info {EvilValue}", new BadObject());
+
+			var logEvents = getLogEvents();
+			logEvents.Should().HaveCount(1);
+
+			var ecsEvents = ToEcsEvents(logEvents);
+
+			var (_, info) = ecsEvents.First();
+			info.Message.Should().Be("Info Elastic.CommonSchema.NLog.Tests.MessageTests+BadObject");
+			info.Metadata.Should().ContainKey("EvilValue");
+
+			var x = info.Metadata["EvilValue"] as System.Collections.Generic.Dictionary<string, object>;
+			x.Should().NotBeNull().And.NotBeEmpty();
+		});
+
+		class BadObject
+		{
+			// public IEnumerable<object> Recursive => new List<object>(new[] { "Hello", (object)this })
+
+			// public string EvilProperty => throw new NotSupportedException()
+
+			public System.Type TypeProperty { get; } = typeof(BadObject);
+
+			public System.Reflection.MethodInfo MethodInfoProperty { get; } = typeof(BadObject).GetProperty(nameof(MethodInfoProperty)).GetMethod;
+
+			public System.Action DelegateProperty { get; } = new System.Action(() => throw new NotSupportedException());
+
+			public System.Collections.IEqualityComparer ComparerProperty { get; } = StringComparer.OrdinalIgnoreCase;
+
+			public System.IFormatProvider CultureProperty { get; } = System.Globalization.CultureInfo.InvariantCulture;
+		}
+
 		[Fact]
 		public void SeesMessageWithException() => TestLogger((logger, getLogEvents) =>
 		{