Add NoSchemaIntrospectionCustomRule

src/index.d.ts

@@ -335,6 +335,8 @@ export {
   UniqueFieldDefinitionNamesRule,
   UniqueDirectiveNamesRule,
   PossibleTypeExtensionsRule,
+  // Custom validation rules
+  NoSchemaIntrospectionCustomRule,
   ValidationRule,
 } from './validation/index';
 

src/index.js

@@ -333,6 +333,8 @@ export {
   UniqueFieldDefinitionNamesRule,
   UniqueDirectiveNamesRule,
   PossibleTypeExtensionsRule,
+  // Custom validation rules
+  NoSchemaIntrospectionCustomRule,
 } from './validation/index';
 
 export type { ValidationRule } from './validation/index';

src/validation/__tests__/NoSchemaIntrospectionCustomRule-test.js

@@ -0,0 +1,142 @@
+// @flow strict
+
+import { describe, it } from 'mocha';
+
+import { buildSchema } from '../../utilities/buildASTSchema';
+
+import { NoSchemaIntrospectionCustomRule } from '../rules/custom/NoSchemaIntrospectionCustomRule';
+
+import { expectValidationErrorsWithSchema } from './harness';
+
+function expectErrors(queryStr) {
+  return expectValidationErrorsWithSchema(
+    schema,
+    NoSchemaIntrospectionCustomRule,
+    queryStr,
+  );
+}
+
+function expectValid(queryStr) {
+  expectErrors(queryStr).to.deep.equal([]);
+}
+
+const schema = buildSchema(`
+  type Query {
+    someQuery: SomeType
+  }
+
+  type SomeType {
+    someField: String
+    introspectionField: __EnumValue
+  }
+`);
+
+describe('Validate: Prohibit introspection queries', () => {
+  it('ignores valid fields including __typename', () => {
+    expectValid(`
+      {
+        someQuery {
+          __typename
+          someField
+        }
+      }
+    `);
+  });
+
+  it('ignores fields not in the schema', () => {
+    expectValid(`
+      {
+        __introspect
+      }
+    `);
+  });
+
+  it('reports error when a field with an introspection type is requested', () => {
+    expectErrors(`
+      {
+        __schema {
+          queryType {
+            name
+          }
+        }
+      }
+    `).to.deep.equal([
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "__schema".',
+        locations: [{ line: 3, column: 9 }],
+      },
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "queryType".',
+        locations: [{ line: 4, column: 11 }],
+      },
+    ]);
+  });
+
+  it('reports error when a field with an introspection type is requested and aliased', () => {
+    expectErrors(`
+      {
+        s: __schema {
+          queryType {
+            name
+          }
+        }
+      }
+      `).to.deep.equal([
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "__schema".',
+        locations: [{ line: 3, column: 9 }],
+      },
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "queryType".',
+        locations: [{ line: 4, column: 11 }],
+      },
+    ]);
+  });
+
+  it('reports error when using a fragment with a field with an introspection type', () => {
+    expectErrors(`
+      {
+        ...QueryFragment
+      }
+
+      fragment QueryFragment on Query {
+        __schema {
+          queryType {
+            name
+          }
+        }
+      }
+    `).to.deep.equal([
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "__schema".',
+        locations: [{ line: 7, column: 9 }],
+      },
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "queryType".',
+        locations: [{ line: 8, column: 11 }],
+      },
+    ]);
+  });
+
+  it('reports error for non-standard introspection fields', () => {
+    expectErrors(`
+      {
+        someQuery {
+          introspectionField
+        }
+      }
+    `).to.deep.equal([
+      {
+        message:
+          'GraphQL introspection has been disabled, but the requested query contained the field "introspectionField".',
+        locations: [{ line: 4, column: 11 }],
+      },
+    ]);
+  });
+});

src/validation/index.d.ts

@@ -90,3 +90,6 @@ export { UniqueEnumValueNamesRule } from './rules/UniqueEnumValueNamesRule';
 export { UniqueFieldDefinitionNamesRule } from './rules/UniqueFieldDefinitionNamesRule';
 export { UniqueDirectiveNamesRule } from './rules/UniqueDirectiveNamesRule';
 export { PossibleTypeExtensionsRule } from './rules/PossibleTypeExtensionsRule';
+
+// Optional rules not defined by the GraphQL Specification
+export { NoSchemaIntrospectionCustomRule } from './rules/custom/NoSchemaIntrospectionCustomRule';

src/validation/index.js

@@ -94,3 +94,6 @@ export { UniqueEnumValueNamesRule } from './rules/UniqueEnumValueNamesRule';
 export { UniqueFieldDefinitionNamesRule } from './rules/UniqueFieldDefinitionNamesRule';
 export { UniqueDirectiveNamesRule } from './rules/UniqueDirectiveNamesRule';
 export { PossibleTypeExtensionsRule } from './rules/PossibleTypeExtensionsRule';
+
+// Optional rules not defined by the GraphQL Specification
+export { NoSchemaIntrospectionCustomRule } from './rules/custom/NoSchemaIntrospectionCustomRule';

src/validation/rules/custom/NoSchemaIntrospectionCustomRule.d.ts

@@ -0,0 +1,16 @@
+import { ASTVisitor } from '../../../language/visitor';
+import { ValidationContext } from '../../ValidationContext';
+
+/**
+ * Prohibit introspection queries
+ *
+ * A GraphQL document is only valid if all fields selected are not fields that
+ * return an introspection type.
+ *
+ * Note: This rule is optional and is not part of the Validation section of the
+ * GraphQL Specification. This rule effectively disables introspection, which
+ * does not reflect best practices and should only be done if absolutely necessary.
+ */
+export function NoSchemaIntrospectionCustomRule(
+  context: ValidationContext,
+): ASTVisitor;

src/validation/rules/custom/NoSchemaIntrospectionCustomRule.js

@@ -0,0 +1,39 @@
+// @flow strict
+
+import { GraphQLError } from '../../../error/GraphQLError';
+
+import type { FieldNode } from '../../../language/ast';
+import type { ASTVisitor } from '../../../language/visitor';
+
+import { getNamedType } from '../../../type/definition';
+import { isIntrospectionType } from '../../../type/introspection';
+
+import type { ValidationContext } from '../../ValidationContext';
+
+/**
+ * Prohibit introspection queries
+ *
+ * A GraphQL document is only valid if all fields selected are not fields that
+ * return an introspection type.
+ *
+ * Note: This rule is optional and is not part of the Validation section of the
+ * GraphQL Specification. This rule effectively disables introspection, which
+ * does not reflect best practices and should only be done if absolutely necessary.
+ */
+export function NoSchemaIntrospectionCustomRule(
+  context: ValidationContext,
+): ASTVisitor {
+  return {
+    Field(node: FieldNode) {
+      const type = getNamedType(context.getType());
+      if (type && isIntrospectionType(type)) {
+        context.reportError(
+          new GraphQLError(
+            `GraphQL introspection has been disabled, but the requested query contained the field "${node.name.value}".`,
+            node,
+          ),
+        );
+      }
+    },
+  };
+}