GraphQL Interface Protection Bypass

Remediation

To prevent GraphQL interface protection bypass vulnerabilities, implement comprehensive authorization controls:

1. Implement field-level authorization: Ensure authorization checks are applied at the field level, not just at the query level.

   Example (GraphQL Shield for field-level protection):

   const { shield, rule, and } = require('graphql-shield');
      
   const isAuthenticated = rule({ cache: 'contextual' })(
     async (parent, args, context) => {
       return context.user !== null;
     }
   );
      
   const isOwner = rule({ cache: 'contextual' })(
     async (parent, args, context) => {
       return context.user && parent.userId === context.user.id;
     }
   );
      
   const permissions = shield({
     User: {
       sensitiveField: and(isAuthenticated, isOwner)
     },
     UserInterface: {
       '*': isAuthenticated // Apply to all interface fields
     }
   });
   

2. Validate interface implementations: Ensure that all implementations of GraphQL interfaces maintain the same security policies.

   Example (Consistent authorization across interface implementations):

   const resolvers = {
     User: {
       __resolveType(obj) {
         if (obj.type === 'admin') return 'AdminUser';
         return 'RegularUser';
       },
       sensitiveData: (parent, args, context) => {
         // Authorization check applies to all implementing types
         if (!context.user || context.user.id !== parent.userId) {
           throw new ForbiddenError('Access denied');
         }
         return parent.sensitiveData;
       }
     }
   };
   

3. Use GraphQL directives for authorization: Implement custom directives to enforce consistent authorization across interfaces and their implementations.

   Example (Custom authorization directive):

   const { SchemaDirectiveVisitor } = require('apollo-server-express');
      
   class AuthDirective extends SchemaDirectiveVisitor {
     visitFieldDefinition(field) {
       const { resolve = defaultFieldResolver } = field;
       const requiredRole = this.args.requires;
          
       field.resolve = async function(...args) {
         const [, , context] = args;
         if (!context.user || !context.user.roles.includes(requiredRole)) {
           throw new ForbiddenError('Insufficient permissions');
         }
         return resolve.apply(this, args);
       };
     }
   }
   

4. Implement role-based access control (RBAC): Use comprehensive RBAC that accounts for interface inheritance and field-level permissions.

About

GraphQL interface protection bypass vulnerabilities occur when authorization controls are not properly implemented across GraphQL interfaces and their concrete implementations. GraphQL interfaces define a common set of fields that multiple types can implement, but if authorization checks are only applied to specific implementing types rather than the interface itself, attackers may be able to access restricted fields by querying through the interface. This vulnerability is particularly dangerous because it can allow unauthorized access to sensitive data across multiple related types that implement the same interface.

Risks

The risks associated with GraphQL interface protection bypass include:

• Unauthorized data access: Attackers can bypass field-level authorization by accessing restricted fields through less-protected interface queries.
• Privilege escalation: Users may gain access to administrative or sensitive functionality by exploiting interface implementations with weaker security controls.
• Data leakage: Sensitive information intended for specific user roles may be exposed through interface queries that bypass authorization checks.
• Inconsistent security policies: Different implementations of the same interface may have varying security controls, creating attack vectors through the weakest implementation.