Allow disabling introspection (#1227, #456)

- implement `validation::rules::disable_introspection`
- add `RootNode::disable_introspection()` and `RootNode::enable_introspection()` methods

juniper/CHANGELOG.md

@@ -70,6 +70,7 @@ All user visible changes to `juniper` crate will be documented in this file. Thi
 - `LookAheadMethods::applies_for()` method. ([#1138], [#1145])
 - `LookAheadMethods::field_original_name()` and `LookAheadMethods::field_alias()` methods. ([#1199])
 - [`anyhow` crate] integration behind `anyhow` and `backtrace` [Cargo feature]s. ([#1215], [#988])
+- `RootNode::disable_introspection()` applying additional `validation::rules::disable_introspection`, and `RootNode::enable_introspection()` reverting it. ([#1227], [#456])
 
 ### Changed
 
@@ -88,6 +89,7 @@ All user visible changes to `juniper` crate will be documented in this file. Thi
 - Stack overflow on nested GraphQL fragments. ([CVE-2022-31173])
 
 [#113]: /../../issues/113
+[#456]: /../../issues/456
 [#503]: /../../issues/503
 [#528]: /../../issues/528
 [#750]: /../../issues/750
@@ -140,6 +142,7 @@ All user visible changes to `juniper` crate will be documented in this file. Thi
 [#1209]: /../../pull/1209
 [#1215]: /../../pull/1215
 [#1221]: /../../pull/1221
+[#1227]: /../../pull/1227
 [ba1ed85b]: /../../commit/ba1ed85b3c3dd77fbae7baf6bc4e693321a94083
 [CVE-2022-31173]: /../../security/advisories/GHSA-4rx6-g5vg-5f3j
 

juniper/src/lib.rs

@@ -58,7 +58,10 @@ use crate::{
     executor::{execute_validated_query, get_operation},
     introspection::{INTROSPECTION_QUERY, INTROSPECTION_QUERY_WITHOUT_DESCRIPTIONS},
     parser::parse_document_source,
-    validation::{validate_input_values, visit_all_rules, ValidatorContext},
+    validation::{
+        rules, validate_input_values, visit as visit_rule, visit_all_rules, MultiVisitorNil,
+        ValidatorContext,
+    },
 };
 
 pub use crate::{
@@ -158,6 +161,13 @@ where
     {
         let mut ctx = ValidatorContext::new(&root_node.schema, &document);
         visit_all_rules(&mut ctx, &document);
+        if root_node.introspection_disabled {
+            visit_rule(
+                &mut MultiVisitorNil.with(rules::disable_introspection::factory()),
+                &mut ctx,
+                &document,
+            );
+        }
 
         let errors = ctx.into_errors();
         if !errors.is_empty() {
@@ -201,6 +211,13 @@ where
     {
         let mut ctx = ValidatorContext::new(&root_node.schema, &document);
         visit_all_rules(&mut ctx, &document);
+        if root_node.introspection_disabled {
+            visit_rule(
+                &mut MultiVisitorNil.with(rules::disable_introspection::factory()),
+                &mut ctx,
+                &document,
+            );
+        }
 
         let errors = ctx.into_errors();
         if !errors.is_empty() {
@@ -246,6 +263,13 @@ where
     {
         let mut ctx = ValidatorContext::new(&root_node.schema, &document);
         visit_all_rules(&mut ctx, &document);
+        if root_node.introspection_disabled {
+            visit_rule(
+                &mut MultiVisitorNil.with(rules::disable_introspection::factory()),
+                &mut ctx,
+                &document,
+            );
+        }
 
         let errors = ctx.into_errors();
         if !errors.is_empty() {

juniper/src/schema/model.rs

@@ -44,6 +44,8 @@ pub struct RootNode<
     pub subscription_info: SubscriptionT::TypeInfo,
     #[doc(hidden)]
     pub schema: SchemaType<'a, S>,
+    #[doc(hidden)]
+    pub introspection_disabled: bool,
 }
 
 /// Metadata for a schema
@@ -147,7 +149,7 @@ where
         mutation_info: MutationT::TypeInfo,
         subscription_info: SubscriptionT::TypeInfo,
     ) -> Self {
-        RootNode {
+        Self {
             query_type: query_obj,
             mutation_type: mutation_obj,
             subscription_type: subscription_obj,
@@ -159,9 +161,65 @@ where
             query_info,
             mutation_info,
             subscription_info,
+            introspection_disabled: false,
         }
     }
 
+    /// Disables introspection for this [`RootNode`], making it to return a [`FieldError`] whenever
+    /// its `__schema` or `__type` field is resolved.
+    ///
+    /// By default, all introspection queries are allowed.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # use juniper::{
+    /// #     graphql_object, graphql_vars, EmptyMutation, EmptySubscription, GraphQLError,
+    /// #     RootNode,
+    /// # };
+    /// #
+    /// pub struct Query;
+    ///
+    /// #[graphql_object]
+    /// impl Query {
+    ///     fn some() -> bool {
+    ///         true
+    ///     }
+    /// }
+    ///
+    /// type Schema = RootNode<'static, Query, EmptyMutation<()>, EmptySubscription<()>>;
+    ///
+    /// let schema = Schema::new(Query, EmptyMutation::new(), EmptySubscription::new())
+    ///     .disable_introspection();
+    ///
+    /// # // language=GraphQL
+    /// let query = "query { __schema { queryType { name } } }";
+    ///
+    /// match juniper::execute_sync(query, None, &schema, &graphql_vars! {}, &()) {
+    ///     Err(GraphQLError::ValidationError(errs)) => {
+    ///         assert_eq!(
+    ///             errs.first().unwrap().message(),
+    ///             "GraphQL introspection is not allowed, but the operation contained `__schema`",
+    ///         );
+    ///     }
+    ///     res => panic!("expected `ValidationError`, returned: {res:#?}"),
+    /// }
+    /// ```
+    pub fn disable_introspection(mut self) -> Self {
+        self.introspection_disabled = true;
+        self
+    }
+
+    /// Enables introspection for this [`RootNode`], if it was previously [disabled][1].
+    ///
+    /// By default, all introspection queries are allowed.
+    ///
+    /// [1]: RootNode::disable_introspection
+    pub fn enable_introspection(mut self) -> Self {
+        self.introspection_disabled = false;
+        self
+    }
+
     #[cfg(feature = "schema-language")]
     /// The schema definition as a `String` in the
     /// [GraphQL Schema Language](https://graphql.org/learn/schema/#type-language)

juniper/src/validation/mod.rs

@@ -3,7 +3,7 @@
 mod context;
 mod input_value;
 mod multi_visitor;
-mod rules;
+pub mod rules;
 mod traits;
 mod visitor;
 

juniper/src/validation/rules/disable_introspection.rs

@@ -0,0 +1,203 @@
+//! Validation rule checking whether a GraphQL operation contains introspection (`__schema` or
+//! `__type` fields).
+
+use crate::{
+    ast::Field,
+    parser::Spanning,
+    validation::{ValidatorContext, Visitor},
+    value::ScalarValue,
+};
+
+/// Validation rule checking whether a GraphQL operation contains introspection (`__schema` or
+/// `__type` fields).
+pub struct DisableIntrospection;
+
+/// Produces a new [`DisableIntrospection`] validation rule.
+#[inline]
+#[must_use]
+pub fn factory() -> DisableIntrospection {
+    DisableIntrospection
+}
+
+impl<'a, S> Visitor<'a, S> for DisableIntrospection
+where
+    S: ScalarValue,
+{
+    fn enter_field(
+        &mut self,
+        context: &mut ValidatorContext<'a, S>,
+        field: &'a Spanning<Field<S>>,
+    ) {
+        let field_name = field.item.name.item;
+        if matches!(field_name, "__schema" | "__type") {
+            context.report_error(&error_message(field_name), &[field.item.name.span.start]);
+        }
+    }
+}
+
+fn error_message(field_name: &str) -> String {
+    format!("GraphQL introspection is not allowed, but the operation contained `{field_name}`")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{error_message, factory};
+
+    use crate::{
+        parser::SourcePosition,
+        validation::{expect_fails_rule, expect_passes_rule, RuleError},
+        value::DefaultScalarValue,
+    };
+
+    #[test]
+    fn allows_regular_fields() {
+        // language=GraphQL
+        expect_passes_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                user {
+                    name
+                    ... on User {
+                        email
+                    }
+                    alias: email
+                    ... {
+                        typeless
+                    }
+                    friends {
+                        name
+                    }
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn allows_typename_field() {
+        // language=GraphQL
+        expect_passes_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                __typename
+                user {
+                    __typename
+                    ... on User {
+                        __typename
+                    }
+                    ... {
+                        __typename
+                    }
+                    friends {
+                        __typename
+                    }
+                }
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn forbids_query_schema() {
+        // language=GraphQL
+        expect_fails_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                __schema {
+                    queryType {
+                       name
+                    }
+                }
+            }
+            "#,
+            &[RuleError::new(
+                &error_message("__schema"),
+                &[SourcePosition::new(37, 2, 16)],
+            )],
+        );
+    }
+
+    #[test]
+    fn forbids_query_type() {
+        // language=GraphQL
+        expect_fails_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                __type(
+                   name: "Query"
+                ) {
+                   name
+                }
+            }
+            "#,
+            &[RuleError::new(
+                &error_message("__type"),
+                &[SourcePosition::new(37, 2, 16)],
+            )],
+        );
+    }
+
+    #[test]
+    fn forbids_field_type() {
+        // language=GraphQL
+        expect_fails_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                user {
+                    name
+                    ... on User {
+                        email
+                    }
+                    alias: email
+                    ... {
+                        typeless
+                    }
+                    friends {
+                        name
+                    }
+                    __type
+                }
+            }
+            "#,
+            &[RuleError::new(
+                &error_message("__type"),
+                &[SourcePosition::new(370, 14, 20)],
+            )],
+        );
+    }
+
+    #[test]
+    fn forbids_field_schema() {
+        // language=GraphQL
+        expect_fails_rule::<_, _, DefaultScalarValue>(
+            factory,
+            r#"
+            query {
+                user {
+                    name
+                    ... on User {
+                        email
+                    }
+                    alias: email
+                    ... {
+                        typeless
+                    }
+                    friends {
+                        name
+                    }
+                    __schema
+                }
+            }
+            "#,
+            &[RuleError::new(
+                &error_message("__schema"),
+                &[SourcePosition::new(370, 14, 20)],
+            )],
+        );
+    }
+}

juniper/src/validation/rules/mod.rs

@@ -1,5 +1,8 @@
+//! Definitions of rules for validation.
+
 mod arguments_of_correct_type;
 mod default_values_of_correct_type;
+pub mod disable_introspection;
 mod fields_on_correct_type;
 mod fragments_on_composite_types;
 mod known_argument_names;
@@ -23,12 +26,13 @@ mod unique_variable_names;
 mod variables_are_input_types;
 mod variables_in_allowed_position;
 
+use std::fmt::Debug;
+
 use crate::{
     ast::Document,
     validation::{visit, MultiVisitorNil, ValidatorContext},
     value::ScalarValue,
 };
-use std::fmt::Debug;
 
 #[doc(hidden)]
 pub fn visit_all_rules<'a, S: Debug>(ctx: &mut ValidatorContext<'a, S>, doc: &'a Document<S>)