GraphQL Interface Exploit

Remediation

To prevent GraphQL interface exploitation, implement robust authorization and validation controls:

1. Implement consistent field-level authorization: Ensure authorization checks are consistently applied across all interface implementations.

   Example (Resolver-level authorization):

   const resolvers = {
     UserInterface: {
       __resolveType(obj, context, info) {
         // Ensure user has permission to access this interface type
         if (!context.user) {
           throw new AuthenticationError('Authentication required');
         }
         return obj.__typename;
       }
     },
     User: {
       sensitiveField: (parent, args, context) => {
         // Consistent authorization for all User implementations
         if (context.user.role !== 'admin' && context.user.id !== parent.id) {
           throw new ForbiddenError('Access denied to sensitive field');
         }
         return parent.sensitiveField;
       }
     }
   };
   

2. Validate interface usage: Implement validation to ensure interfaces are only used in authorized contexts.

   Example (Custom validation rule):

   const interfaceAuthRule = (context) => {
     return {
       InlineFragment(node) {
         if (node.typeCondition && isRestrictedInterface(node.typeCondition.name.value)) {
           const userRole = context.getContext().user?.role;
           if (userRole !== 'admin') {
             context.reportError(
               new GraphQLError('Unauthorized interface access', [node])
             );
           }
         }
       }
     };
   };
   

3. Use type-specific resolvers: Implement specific resolvers for different interface implementations to ensure appropriate authorization.

   Example (Type-specific authorization):

   const resolvers = {
     AdminUser: {
       adminOnlyField: (parent, args, context) => {
         if (context.user.role !== 'admin') {
           throw new ForbiddenError('Admin access required');
         }
         return parent.adminOnlyField;
       }
     },
     RegularUser: {
       adminOnlyField: () => {
         throw new ForbiddenError('Field not available for regular users');
       }
     }
   };
   

4. Monitor interface usage: Implement logging and monitoring for interface queries to detect potential exploitation attempts.

About

GraphQL interface exploitation occurs when attackers abuse GraphQL interfaces to bypass authorization controls and access sensitive fields that should be restricted. This vulnerability takes advantage of the way GraphQL interfaces work - they define a contract that multiple concrete types can implement, but if authorization is not properly enforced at the interface level, attackers can use inline fragments or interface queries to access fields they shouldn’t have permission to read. The exploitation typically involves crafting queries that use interfaces to access sensitive data from different implementing types without proper authorization validation.

Risks

The risks associated with GraphQL interface exploitation include:

• Authorization bypass: Attackers can circumvent field-level and type-level authorization controls by accessing data through interface queries.
• Sensitive data exposure: Personal information, administrative data, or confidential business information may be exposed through interface-based queries.
• Privilege escalation: Users may gain access to higher-privilege functionality by exploiting interface implementations with insufficient authorization controls.
• Cross-type data leakage: Information from different implementing types may be accessible through a single interface query, potentially exposing data from multiple contexts or user roles.