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Improved Security and Cost Control in Federation Composition

Kamil Kisiela
Kamil Kisiela

We recently improved authorization and demand control directives validation in our federation composition library. These changes ensure your federated GraphQL schemas are more secure, predictable, and properly validated across all subgraphs.

Stricter Authorization Directive

Authentication directives (@authenticated, @requiresScopes, and @policy) are critical for securing federated GraphQL APIs. To prevent misconfigurations that could compromise security, we’ve introduced stricter rules.

Authorization Directive on Interfaces

Auth directives are now restricted to object types, their fields, enums, and scalars only. Attempting to place these directives on interfaces, interface fields, or @interfaceObject types will result in a composition error with the new AUTH_REQUIREMENTS_APPLIED_ON_INTERFACE rule.

Interface types and fields now inherit @authenticated, @requiresScopes, and @policy directives from the object types that implement them. This reduces configuration overhead and ensures consistent security policies across your schema.

Authorization directives are not allowed on interfaces
interface Node @authenticated {
  id: ID!
}

type User implements Node {
  id: ID!
}
Authorization directives
# ✅ Node interface inherits the auth directive
interface Node {
  id: ID!
}

type User implements Node @authenticated {
  id: ID!
}

The composed schema will pass authorization directives from implementing object types to interfaces.

Supergraph
interface Node @authenticated {
  id: ID!
}

type User implements Node @authenticated {
  id: ID!
}

This prevents security configurations from being silently ignored or applied incorrectly in your schema.

Fields with @requires Directive

We added transitive auth requirements checking to the validation phase of the federation composition. Fields using the @requires directive must now specify at least the auth requirements of all fields they depend on.

If a field doesn’t carry forward the @authenticated, @requiresScopes, or @policy requirements from its dependencies, composition fails with a clear MISSING_TRANSITIVE_AUTH_REQUIREMENTS error.

Subgraph A
type User @key(fields: "id") {
  id: ID!
  email: String @requiresScopes(scopes: [["email:read"]])
}
type User @key(fields: "id") {
  id: ID!
  email: String @external
  # Misses auth requirements from `email` field,
  # expected to have `@requiresScopes(scopes: [["email:read"]])`
  contactInfo: ContactInfo @requires(fields: "email")
}
type User @key(fields: "id") {
  id: ID!
  email: String @external
  # Carries forward minimum auth requirements from `email` field.
  contactInfo: ContactInfo @requires(fields: "email") @requiresScopes(scopes: [["email:read"]])
}

This ensures that authorization requirements flow correctly through your query execution paths.

Improved Demand Control Directives

The @cost and @listSize directives provide crucial safeguards against expensive queries. We’ve enhanced their validation to catch configuration errors early.

@cost Directive Restrictions

The @cost directive can no longer be placed on interface types, their fields, or field arguments. Invalid placements now result in clear composition errors instead of being silently accepted.

This ensures cost calculations remain predictable and properly aligned with your schema structure.

Enhanced @listSize Validation

  • Field Type Validation - The sizedFields argument now validates that referenced fields are actually list types, not integer counters.
  • Argument Validation - The slicingArguments are now validated to ensure they exist in all subgraphs. Only valid arguments are retained, and invalid ones trigger clear errors.
# Raises error: sizedFields must point to list fields
type Query {
  users(first: Int): UserConnection @listSize(sizedFields: ["count"], slicingArguments: ["first"])
}

type UserConnection {
count: Int!
edges: [User!]!
}
# sizedFields points to the actual list field
type Query {
  users(first: Int): UserConnection @listSize(sizedFields: ["edges"], slicingArguments: ["first"])
}

type UserConnection {
  count: Int!
  edges: [User!]!
}

More Reliable Federation Composition

These changes strengthen the composition process by:

  • Preventing security misconfigurations that could weaken API protection
  • Ensuring auth requirements are properly propagated through your schema
  • Catching cost calculation errors early before they reach production
  • Reducing silent failures with clear, actionable error messages