Prevent stack overflow in MiscFilters.WriteJson (#352)

Fixes #351
sebastienros · May 27, 2021 · 7ef1948 · 7ef1948
1 parent d798185
commit 7ef1948
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Showing 2 changed files with 88 additions and 2 deletions.
diff --git a/Fluid.Tests/MiscFiltersTests.cs b/Fluid.Tests/MiscFiltersTests.cs
@@ -520,6 +520,33 @@ public async Task JsonShouldHideMembers()
             Assert.Equal(expected, result.ToStringValue());
         }
 
+        [Fact]
+        public async Task JsonShouldHandleCircularReferences()
+        {
+            var model = TestObjects.RecursiveReferenceObject;
+            var input = FluidValue.Create(model, TemplateOptions.Default);
+            var to = new TemplateOptions();
+            to.MemberAccessStrategy.Register<TestObjects.Node>();
+
+            var result = await MiscFilters.Json(input, new FilterArguments(), new TemplateContext(to));
+
+            Assert.Equal("{\"Name\":\"Object1\",\"NodeRef\":{\"Name\":\"Child1\",\"NodeRef\":\"circular reference detected.\"}}", result.ToStringValue());
+        }
+
+        [Fact]
+        public async Task JsonShouldHandleCircularReferencesOnSiblingPropertiesSeparately()
+        {
+            var model = TestObjects.SiblingPropertiesHaveSameReferenceObject;
+            var input = FluidValue.Create(model, TemplateOptions.Default);
+            var to = new TemplateOptions();
+            to.MemberAccessStrategy.Register<TestObjects.Node>();
+            to.MemberAccessStrategy.Register<TestObjects.MultipleNode>();
+
+            var result = await MiscFilters.Json(input, new FilterArguments(), new TemplateContext(to));
+
+            Assert.Equal("{\"Name\":\"MultipleNode1\",\"Node1\":{\"Name\":\"Object1\",\"NodeRef\":{\"Name\":\"Child1\",\"NodeRef\":\"circular reference detected.\"}},\"Node2\":{\"Name\":\"Object1\",\"NodeRef\":{\"Name\":\"Child1\",\"NodeRef\":\"circular reference detected.\"}}}", result.ToStringValue());
+        }
+
         [Theory]
         [InlineData("", "", "", "0")]
         [InlineData(123456, "", "", "123456")]
@@ -565,6 +592,57 @@ public async Task FormatString(object input, object[] args, string culture, stri
             Assert.Equal(expected, result.ToStringValue());
         }
 
+        public static class TestObjects
+        {
+            public class Node
+            {
+                public string Name { get; set; }
+                public Node NodeRef { get; set; }
+            }
+
+            public class MultipleNode
+            {
+                public string Name { get; set; }
+
+                public Node Node1 { get; set; }
+
+                public Node Node2 { get; set; }
+            }
+
+            public static Node RecursiveReferenceObject
+            {
+                get
+                {
+                    var parent = new Node
+                    {
+                        Name = "Object1",
+                    };
+                    var child = new Node
+                    {
+                        Name = "Child1",
+                        NodeRef = parent
+                    };
+                    parent.NodeRef = child;
+                    return parent;
+                }
+            }
+
+            public static object SiblingPropertiesHaveSameReferenceObject
+            {
+                get
+                {
+                    var n = RecursiveReferenceObject;
+                    var m = new MultipleNode
+                    {
+                        Name = "MultipleNode1",
+                        Node1 = n,
+                        Node2 = n
+                    };
+                    return m;
+                }
+            }
+        }
+
         private class JsonAccessStrategy
         {
             public string Visible { get; set; } = "Visible";

diff --git a/Fluid/Filters/MiscFilters.cs b/Fluid/Filters/MiscFilters.cs
@@ -542,7 +542,7 @@ private static bool TryGetDateTimeInput(FluidValue input, TemplateContext contex
             return true;
         }
 
-        private static async ValueTask WriteJson(Utf8JsonWriter writer, FluidValue input, TemplateContext ctx)
+        private static async ValueTask WriteJson(Utf8JsonWriter writer, FluidValue input, TemplateContext ctx, HashSet<object> stack = null)
         {
             switch (input.Type)
             {
@@ -614,14 +614,22 @@ private static async ValueTask WriteJson(Utf8JsonWriter writer, FluidValue input
                                 value = access.Get(obj, name, ctx);
                             }
 
+                            stack ??= new HashSet<object>();
+                            if (stack.Contains(value))
+                            {
+                                value = "circular reference detected.";
+                            }
+
                             var fluidValue = FluidValue.Create(value, ctx.Options);
                             if (fluidValue.IsNil())
                             {
                                 continue;
                             }
 
                             writer.WritePropertyName(name);
-                            await WriteJson(writer, fluidValue, ctx);
+                            stack.Add(obj);
+                            await WriteJson(writer, fluidValue, ctx, stack);
+                            stack.Remove(obj);
                         }
 
                         writer.WriteEndObject();