From 5212353f4c6ed15b1a0be5ec35221e16eca598d9 Mon Sep 17 00:00:00 2001
From: Rolf Kristensen <sweaty1@hotmail.com>
Date: Sat, 10 Sep 2022 12:48:11 +0200
Subject: [PATCH] MetadataDictionaryConverter - Protect against bad types

---
 .../Serialization/JsonConfiguration.cs        | 24 +++++++++++++--
 .../MetadataDictionaryConverter.cs            | 21 +++++++++-----
 .../MessageTests.cs                           | 29 +++++++++++++++++++
 3 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/src/Elastic.CommonSchema/Serialization/JsonConfiguration.cs b/src/Elastic.CommonSchema/Serialization/JsonConfiguration.cs
index b1353720..c2111424 100644
--- a/src/Elastic.CommonSchema/Serialization/JsonConfiguration.cs
+++ b/src/Elastic.CommonSchema/Serialization/JsonConfiguration.cs
@@ -3,6 +3,8 @@
 // See the LICENSE file in the project root for more information
 
 using System;
+using System.Buffers.Text;
+using System.Buffers;
 using System.Text.Encodings.Web;
 using System.Text.Json;
 using System.Text.Json.Serialization;
@@ -18,14 +20,32 @@ public static class EcsJsonConfiguration
 			PropertyNamingPolicy = new SnakeCaseJsonNamingPolicy(),
 			Converters =
 			{
-				new EcsDocumentJsonConverterFactory()
+				new EcsDocumentJsonConverterFactory(),
+				new JsonStringConverter<System.Reflection.Assembly>(),	// Cannot transfer assembly-objects over the wire
+				new JsonStringConverter<System.Reflection.Module>(),	// Cannot transfer module-objects over the wire
+				new JsonStringConverter<System.Reflection.MemberInfo>(),// Cannot transfer method-addresses over the wire
+				new JsonStringConverter<System.Delegate>(),				// Cannot transfer methods over the wire
+				new JsonStringConverter<System.Type>(),					// Cannot transfer types over the wire
+				new JsonStringConverter<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();
+
+		public class JsonStringConverter<T> : JsonConverter<T>
+		{
+			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());
+			}
+		}
 	}
 }
diff --git a/src/Elastic.CommonSchema/Serialization/MetadataDictionaryConverter.cs b/src/Elastic.CommonSchema/Serialization/MetadataDictionaryConverter.cs
index 6df8358a..79f29f53 100644
--- a/src/Elastic.CommonSchema/Serialization/MetadataDictionaryConverter.cs
+++ b/src/Elastic.CommonSchema/Serialization/MetadataDictionaryConverter.cs
@@ -63,17 +63,24 @@ private object ExtractValue(ref Utf8JsonReader reader, JsonSerializerOptions opt
 		{
 			switch (reader.TokenType)
 			{
-				case JsonTokenType.String when reader.TryGetDateTime(out var date): return date;
-				case JsonTokenType.String: return reader.GetString();
-				case JsonTokenType.False: return false;
-				case JsonTokenType.True: return true;
-				case JsonTokenType.Null: return null;
-				case JsonTokenType.Number: return reader.TryGetInt64(out var result) ? result : reader.TryGetDouble(out var d) ? d : reader.GetDecimal();
+				case JsonTokenType.String when reader.TryGetDateTime(out var date):
+					return date;
+				case JsonTokenType.String:
+					return reader.GetString();
+				case JsonTokenType.False:
+					return false;
+				case JsonTokenType.True:
+					return true;
+				case JsonTokenType.Null:
+					return null;
+				case JsonTokenType.Number:
+					return reader.TryGetInt64(out var result) ? result : reader.TryGetDouble(out var d) ? d : reader.GetDecimal();
 				case JsonTokenType.StartObject:
 					return Read(ref reader, null, options);
 				case JsonTokenType.StartArray:
 					var list = new List<object>();
-					while (reader.Read() && reader.TokenType != JsonTokenType.EndArray) list.Add(ExtractValue(ref reader, options));
+					while (reader.Read() && reader.TokenType != JsonTokenType.EndArray)
+						list.Add(ExtractValue(ref reader, options));
 					return list;
 				case JsonTokenType.None:
 				case JsonTokenType.EndObject:
diff --git a/tests/Elastic.CommonSchema.NLog.Tests/MessageTests.cs b/tests/Elastic.CommonSchema.NLog.Tests/MessageTests.cs
index e9755b3e..22524c21 100644
--- a/tests/Elastic.CommonSchema.NLog.Tests/MessageTests.cs
+++ b/tests/Elastic.CommonSchema.NLog.Tests/MessageTests.cs
@@ -49,6 +49,35 @@ 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.Action WeirdProperty { get; } = new System.Action(() => throw new NotSupportedException());
+		}
+
 		[Fact]
 		public void SeesMessageWithException() => TestLogger((logger, getLogEvents) =>
 		{