Add field merging budget

src/HotChocolate/Core/benchmarks/Validation.Benchmarks/OverlappingFieldsMergedBenchmark.cs

@@ -149,7 +149,7 @@ public void FragmentHeavyQuery()
     private DocumentValidatorContext CreateContext(DocumentNode document)
     {
         var context = new DocumentValidatorContext();
-        context.Initialize(_schema, default, document, 100, 100, null);
+        context.Initialize(_schema, default, document, 100, 100, 1_000, null);
         return context;
     }
 

src/HotChocolate/Core/src/Types.Analyzers/Errors.cs

@@ -52,7 +52,7 @@ public static class Errors
 
     public static readonly DiagnosticDescriptor InterfaceTypeStaticKeywordMissing =
         new(
-            id: "HC0107",
+            id: "HC0112",
             title: "Static Keyword Missing",
             messageFormat: "A split interface type class needs to be a static class",
             category: "TypeSystem",
@@ -79,7 +79,7 @@ public static class Errors
 
     public static readonly DiagnosticDescriptor DataLoaderCannotBeGeneric =
         new(
-            id: "HC0085",
+            id: "HC0111",
             title: "DataLoader Cannot Be Generic",
             messageFormat: "The DataLoader source generator cannot generate generic DataLoaders",
             category: "DataLoader",
@@ -88,7 +88,7 @@ public static class Errors
 
     public static readonly DiagnosticDescriptor ConnectionSingleGenericTypeArgument =
         new(
-            id: "HC0086",
+            id: "HC0110",
             title: "Invalid Connection Structure",
             messageFormat: "A generic connection/edge type must have a single generic type argument that represents the node type",
             category: "TypeSystem",
@@ -97,7 +97,7 @@ public static class Errors
 
     public static readonly DiagnosticDescriptor ConnectionNameFormatIsInvalid =
         new(
-            id: "HC0087",
+            id: "HC0109",
             title: "Invalid Connection/Edge Name Format",
             messageFormat: "A connection/edge name must be in the format `{0}Edge` or `{0}Connection`",
             category: "TypeSystem",
@@ -106,7 +106,7 @@ public static class Errors
 
     public static readonly DiagnosticDescriptor ConnectionNameDuplicate =
         new(
-            id: "HC0088",
+            id: "HC0108",
             title: "Invalid Connection/Edge Name",
             messageFormat: "The type `{0}` cannot be mapped to the GraphQL type name `{1}` as `{2}` is already mapped to it",
             category: "TypeSystem",

src/HotChocolate/Core/src/Types/Execution/DependencyInjection/RequestExecutorBuilderExtensions.Validation.cs

@@ -328,6 +328,36 @@ public static IRequestExecutorBuilder RemoveMaxAllowedFieldCycleDepthRule(
         return builder;
     }
 
+    /// <summary>
+    /// Sets the maximum allowed field merge comparisons during
+    /// overlapping-fields-can-be-merged validation.
+    /// </summary>
+    /// <param name="builder">
+    /// The <see cref="IRequestExecutorBuilder"/>.
+    /// </param>
+    /// <param name="maxAllowedFieldMergeComparisons">
+    /// The maximum number of field-merge comparisons.
+    /// </param>
+    /// <returns>
+    /// Returns an <see cref="IRequestExecutorBuilder"/> that can be used to chain
+    /// configuration.
+    /// </returns>
+    /// <exception cref="ArgumentNullException">
+    /// <paramref name="builder"/> is <c>null</c>.
+    /// </exception>
+    public static IRequestExecutorBuilder SetMaxAllowedFieldMergeComparisons(
+        this IRequestExecutorBuilder builder,
+        int maxAllowedFieldMergeComparisons)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
+
+        ConfigureValidation(
+            builder,
+            (_, b) => b.ModifyOptions(o => o.MaxAllowedFieldMergeComparisons = maxAllowedFieldMergeComparisons));
+
+        return builder;
+    }
+
     /// <summary>
     /// Configures the underlying <see cref="DocumentValidatorBuilder"/>.
     /// </summary>

src/HotChocolate/Core/src/Types/Execution/DependencyInjection/RequestExecutorServiceCollectionExtensions.cs

@@ -85,6 +85,7 @@ public static IServiceCollection AddGraphQLCore(this IServiceCollection services
                     maxAllowedNodes: options.MaxAllowedNodes,
                     maxAllowedTokens: options.MaxAllowedTokens,
                     maxAllowedFields: options.MaxAllowedFields,
+                    maxAllowedDirectives: options.MaxAllowedDirectives,
                     maxAllowedRecursionDepth: options.MaxAllowedRecursionDepth);
             });
 

src/HotChocolate/Core/src/Types/Execution/Options/RequestParserOptions.cs

@@ -55,6 +55,15 @@ public sealed class RequestParserOptions
     /// </summary>
     public int MaxAllowedFields { get; set; } = 2048;
 
+    /// <summary>
+    /// <para>
+    /// The maximum number of directives allowed per location (e.g. per field,
+    /// per operation, per fragment definition). Repeatable directives can be used
+    /// to exhaust CPU and memory resources if not limited.
+    /// </para>
+    /// </summary>
+    public int MaxAllowedDirectives { get; set; } = 4;
+
     /// <summary>
     /// <para>
     /// The maximum allowed recursion depth when parsing a document.

src/HotChocolate/Core/src/Validation/DocumentValidator.cs

@@ -18,6 +18,7 @@ public sealed class DocumentValidator
     private readonly IDocumentValidatorRule[] _nonCacheableRules;
     private readonly int _maxAllowedErrors;
     private readonly int _maxLocationsPerError;
+    private readonly int _maxAllowedFragmentVisits;
 
     /// <summary>
     /// Initializes a new instance of <see cref="DocumentValidator"/>.
@@ -34,11 +35,15 @@ public sealed class DocumentValidator
     /// <param name="maxLocationsPerError">
     /// The maximum number of locations that will be added to a validation error.
     /// </param>
+    /// <param name="maxAllowedFragmentVisits">
+    /// The maximum number of fragment visits allowed during validation.
+    /// </param>
     internal DocumentValidator(
         ObjectPool<DocumentValidatorContext> contextPool,
         IDocumentValidatorRule[] rules,
         int maxAllowedErrors,
-        int maxLocationsPerError)
+        int maxLocationsPerError,
+        int maxAllowedFragmentVisits)
     {
         ArgumentNullException.ThrowIfNull(rules);
         ArgumentNullException.ThrowIfNull(contextPool);
@@ -49,6 +54,7 @@ internal DocumentValidator(
         _nonCacheableRules = [.. rules.Where(rule => !rule.IsCacheable)];
         _maxAllowedErrors = maxAllowedErrors > 0 ? maxAllowedErrors : 1;
         _maxLocationsPerError = maxLocationsPerError > 0 ? maxLocationsPerError : 1;
+        _maxAllowedFragmentVisits = maxAllowedFragmentVisits > 0 ? maxAllowedFragmentVisits : 1;
     }
 
     /// <summary>
@@ -158,7 +164,7 @@ private DocumentValidatorContext RentContext(
         IFeatureCollection? features)
     {
         var context = _contextPool.Get();
-        context.Initialize(schema, documentId, document, _maxAllowedErrors, _maxLocationsPerError, features);
+        context.Initialize(schema, documentId, document, _maxAllowedErrors, _maxLocationsPerError, _maxAllowedFragmentVisits, features);
         return context;
     }
 

src/HotChocolate/Core/src/Validation/DocumentValidatorBuilder.cs

@@ -229,7 +229,8 @@ public DocumentValidator Build()
             contextPool,
             [.. rules],
             _options.MaxAllowedErrors,
-            _options.MaxLocationsPerError);
+            _options.MaxLocationsPerError,
+            _options.MaxAllowedFragmentVisits);
     }
 
     private static T CreateInstance<T>(

src/HotChocolate/Core/src/Validation/DocumentValidatorContext.cs

@@ -144,6 +144,7 @@ public void Initialize(
         DocumentNode document,
         int maxAllowedErrors,
         int maxLocationsPerError,
+        int maxAllowedFragmentVisits,
         IFeatureCollection? features)
     {
         ArgumentNullException.ThrowIfNull(schema);
@@ -156,6 +157,8 @@ public void Initialize(
         _maxAllowedErrors = maxAllowedErrors;
         _maxLocationsPerError = maxLocationsPerError;
 
+        Fragments.SetMaxAllowedFragmentVisits(maxAllowedFragmentVisits);
+
         _features.Initialize(features);
 
         foreach (var definitionNode in document.Definitions)
@@ -247,6 +250,8 @@ public sealed class FragmentContext
     {
         private readonly HashSet<string> _visited = [];
         private readonly Dictionary<string, FragmentDefinitionNode> _fragments = new(StringComparer.Ordinal);
+        private int _maxAllowedFragmentVisits;
+        private int _fragmentVisits;
 
         public IEnumerable<string> Names => _fragments.Keys;
 
@@ -267,9 +272,16 @@ public bool TryGet(FragmentSpreadNode spread, [NotNullWhen(true)] out FragmentDe
 
         public bool TryEnter(FragmentSpreadNode spread, [NotNullWhen(true)] out FragmentDefinitionNode? fragment)
         {
+            if (_fragmentVisits >= _maxAllowedFragmentVisits)
+            {
+                fragment = null;
+                return false;
+            }
+
             if (_visited.Add(spread.Name.Value)
                 && _fragments.TryGetValue(spread.Name.Value, out fragment))
             {
+                _fragmentVisits++;
                 return true;
             }
 
@@ -286,13 +298,22 @@ public void Leave(FragmentDefinitionNode fragment)
         public bool Exists(FragmentSpreadNode spread)
             => _fragments.ContainsKey(spread.Name.Value);
 
+        internal void SetMaxAllowedFragmentVisits(int maxAllowedFragmentVisits)
+        {
+            _maxAllowedFragmentVisits = maxAllowedFragmentVisits;
+        }
+
         internal void Reset()
-            => _visited.Clear();
+        {
+            _visited.Clear();
+            _fragmentVisits = 0;
+        }
 
         internal void Clear()
         {
             _visited.Clear();
             _fragments.Clear();
+            _fragmentVisits = 0;
         }
     }
 }

src/HotChocolate/Core/src/Validation/Extensions/ValidationBuilderExtensions.cs

@@ -119,7 +119,7 @@ public static DocumentValidatorBuilder AddFieldRules(
         return builder
             .AddRule<FieldSelectionsRule>()
             .AddRule<LeafFieldSelectionsRule>()
-            .AddRule<OverlappingFieldsCanBeMergedRule>();
+            .AddRule((_, o) => new OverlappingFieldsCanBeMergedRule(o.MaxAllowedFieldMergeComparisons));
     }
 
     /// <summary>

src/HotChocolate/Core/src/Validation/Options/ValidationOptions.cs

@@ -80,4 +80,50 @@ public ushort MaxAllowedListRecursiveDepth
         get;
         set => field = value > 0 ? value : (ushort)16;
     } = 1;
+
+    /// <summary>
+    /// <para>
+    /// The maximum number of field-merge comparisons allowed during
+    /// overlapping-fields-can-be-merged validation. This prevents
+    /// adversarial queries with deeply nested inline fragments from
+    /// consuming unbounded CPU.
+    /// </para>
+    /// <para>Default: <c>100,000</c></para>
+    /// </summary>
+    public int MaxAllowedFieldMergeComparisons
+    {
+        get;
+        set
+        {
+            if (value < 1)
+            {
+                value = 100_000;
+            }
+
+            field = value;
+        }
+    } = 100_000;
+
+    /// <summary>
+    /// <para>
+    /// The maximum number of fragment visits allowed during validation.
+    /// Each time a fragment spread is entered counts as one visit.
+    /// This prevents adversarial queries with deeply nested or repeated
+    /// fragment spreads from consuming unbounded CPU.
+    /// </para>
+    /// <para>Default: <c>1,000</c></para>
+    /// </summary>
+    public int MaxAllowedFragmentVisits
+    {
+        get;
+        set
+        {
+            if (value < 1)
+            {
+                value = 1_000;
+            }
+
+            field = value;
+        }
+    } = 1_000;
 }