Validate the maximum number of route segments (#911)

src/Microsoft.AspNetCore.Routing/Template/RoutePrecedence.cs

@@ -20,6 +20,8 @@ namespace Microsoft.AspNetCore.Routing.Template
         //       /api/template/{id:int} == 1.12
         public static decimal ComputeInbound(RouteTemplate template)
         {
+            ValidateSegementLength(template.Segments.Count);
+
             // Each precedence digit corresponds to one decimal place. For example, 3 segments with precedences 2, 1,
             // and 4 results in a combined precedence of 2.14 (decimal).
             var precedence = 0m;
@@ -40,6 +42,8 @@ namespace Microsoft.AspNetCore.Routing.Template
         // See description on ComputeInbound(RouteTemplate)
         internal static decimal ComputeInbound(RoutePattern routePattern)
         {
+            ValidateSegementLength(routePattern.PathSegments.Count);
+
             var precedence = 0m;
 
             for (var i = 0; i < routePattern.PathSegments.Count; i++)
@@ -62,6 +66,8 @@ namespace Microsoft.AspNetCore.Routing.Template
         //       /api/template/{id:int} == 5.54
         public static decimal ComputeOutbound(RouteTemplate template)
         {
+            ValidateSegementLength(template.Segments.Count);
+
             // Each precedence digit corresponds to one decimal place. For example, 3 segments with precedences 2, 1,
             // and 4 results in a combined precedence of 2.14 (decimal).
             var precedence = 0m;
@@ -82,6 +88,8 @@ namespace Microsoft.AspNetCore.Routing.Template
         // see description on ComputeOutbound(RouteTemplate)
         internal static decimal ComputeOutbound(RoutePattern routePattern)
         {
+            ValidateSegementLength(routePattern.PathSegments.Count);
+
             // Each precedence digit corresponds to one decimal place. For example, 3 segments with precedences 2, 1,
             // and 4 results in a combined precedence of 2.14 (decimal).
             var precedence = 0m;
@@ -99,6 +107,15 @@ namespace Microsoft.AspNetCore.Routing.Template
             return precedence;
         }
 
+        private static void ValidateSegementLength(int length)
+        {
+            if (length > 28)
+            {
+                // An OverflowException will be thrown by Math.Pow when greater than 28
+                throw new InvalidOperationException("Route exceeds the maximum number of allowed segments of 28 and is unable to be processed.");
+            }
+        }
+
         // Segments have the following order:
         // 5 - Literal segments
         // 4 - Multi-part segments && Constrained parameter segments

test/Microsoft.AspNetCore.Routing.Tests/Template/RoutePatternPrecedenceTests.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNetCore.Routing.Patterns;
+
+namespace Microsoft.AspNetCore.Routing.Template
+{
+    public class RoutePatternPrecedenceTests : RoutePrecedenceTestsBase
+    {
+        protected override decimal ComputeMatched(string template)
+        {
+            return ComputeRoutePattern(template, RoutePrecedence.ComputeInbound);
+        }
+
+        protected override decimal ComputeGenerated(string template)
+        {
+            return ComputeRoutePattern(template, RoutePrecedence.ComputeOutbound);
+        }
+
+        private static decimal ComputeRoutePattern(string template, Func<RoutePattern, decimal> func)
+        {
+            var parsed = RoutePatternFactory.Parse(template);
+            return func(parsed);
+        }
+    }
+}

test/Microsoft.AspNetCore.Routing.Tests/Template/RoutePrecedenceTestsBase.cs

@@ -2,13 +2,11 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using Microsoft.Extensions.Options;
-using Moq;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Routing.Template
 {
-    public class RoutePrecedenceTests
+    public abstract class RoutePrecedenceTestsBase
     {
         [Theory]
         [InlineData("Employees/{id}", "Employees/{employeeId}")]
@@ -100,22 +98,34 @@ namespace Microsoft.AspNetCore.Routing.Template
             Assert.True(xPrecedence > yPrecedence);
         }
 
-        private static decimal ComputeMatched(string template)
+        [Fact]
+        public void ComputeGenerated_TooManySegments_ThrowHumaneError()
         {
-            return Compute(template, RoutePrecedence.ComputeInbound);
-        }
-        private static decimal ComputeGenerated(string template)
-        {
-            return Compute(template, RoutePrecedence.ComputeOutbound);
+            var ex = Assert.Throws<InvalidOperationException>(() =>
+            {
+                // Arrange & Act
+                ComputeGenerated("{a}/{b}/{c}/{d}/{e}/{f}/{g}/{h}/{i}/{j}/{k}/{l}/{m}/{n}/{o}/{p}/{q}/{r}/{s}/{t}/{u}/{v}/{w}/{x}/{y}/{z}/{a2}/{b2}/{b3}");
+            });
+
+            // Assert
+            Assert.Equal("Route exceeds the maximum number of allowed segments of 28 and is unable to be processed.", ex.Message);
         }
 
-        private static decimal Compute(string template, Func<RouteTemplate, decimal> func)
+        [Fact]
+        public void ComputeMatched_TooManySegments_ThrowHumaneError()
         {
-            var options = new Mock<IOptions<RouteOptions>>();
-            options.SetupGet(o => o.Value).Returns(new RouteOptions());
+            var ex = Assert.Throws<InvalidOperationException>(() =>
+            {
+                // Arrange & Act
+                ComputeMatched("{a}/{b}/{c}/{d}/{e}/{f}/{g}/{h}/{i}/{j}/{k}/{l}/{m}/{n}/{o}/{p}/{q}/{r}/{s}/{t}/{u}/{v}/{w}/{x}/{y}/{z}/{a2}/{b2}/{b3}");
+            });
 
-            var parsed = TemplateParser.Parse(template);
-            return func(parsed);
+            // Assert
+            Assert.Equal("Route exceeds the maximum number of allowed segments of 28 and is unable to be processed.", ex.Message);
         }
+
+        protected abstract decimal ComputeMatched(string template);
+
+        protected abstract decimal ComputeGenerated(string template);
     }
 }

test/Microsoft.AspNetCore.Routing.Tests/Template/RouteTemplatePrecedenceTests.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Routing.Template
+{
+    public class RouteTemplatePrecedenceTests : RoutePrecedenceTestsBase
+    {
+        protected override decimal ComputeMatched(string template)
+        {
+            return ComputeRouteTemplate(template, RoutePrecedence.ComputeInbound);
+        }
+
+        protected override decimal ComputeGenerated(string template)
+        {
+            return ComputeRouteTemplate(template, RoutePrecedence.ComputeOutbound);
+        }
+
+        private static decimal ComputeRouteTemplate(string template, Func<RouteTemplate, decimal> func)
+        {
+            var parsed = TemplateParser.Parse(template);
+            return func(parsed);
+        }
+    }
+}