feat(#462): add federation scope enforcement service (#672)

apps/gateway/src/federation/server/scope.service.ts

@@ -0,0 +1,272 @@
+/**
+ * FederationScopeService — M3 server-side scope enforcement pipeline.
+ *
+ * Pure trust-boundary service: it validates the grant scope, asks an injected
+ * native RBAC evaluator what the subject user can read locally, intersects that
+ * answer with the federation scope filters, and returns a query filter for the
+ * verb controllers. The service performs no DB calls directly.
+ */
+
+import { Injectable } from '@nestjs/common';
+import {
+  FEDERATION_RESOURCE_VALUES,
+  type FederationResource,
+  FederationScopeError,
+  parseFederationScope,
+} from '../scope-schema.js';
+import type { FederationContext } from './federation-context.js';
+
+const federationResourceSet: ReadonlySet<string> = new Set<string>(FEDERATION_RESOURCE_VALUES);
+
+export type FederationScopeDenyStage =
+  | 'scope_parse'
+  | 'resource_allowlist'
+  | 'resource_exclusion'
+  | 'native_rbac'
+  | 'row_cap';
+
+export type FederationScopeDenyCode =
+  | 'invalid_scope'
+  | 'invalid_resource'
+  | 'resource_not_granted'
+  | 'resource_excluded'
+  | 'native_rbac_denied'
+  | 'invalid_limit';
+
+export type FederationScopeDenyStatus = 400 | 403;
+
+export interface FederationScopeDenyDetails {
+  readonly [key: string]: string | number | boolean | readonly string[];
+}
+
+export interface FederationScopeDenyReason {
+  readonly code: FederationScopeDenyCode;
+  readonly stage: FederationScopeDenyStage;
+  readonly statusCode: FederationScopeDenyStatus;
+  readonly message: string;
+  readonly grantId: string;
+  readonly peerId: string;
+  readonly subjectUserId: string;
+  readonly resource: string;
+  readonly details?: FederationScopeDenyDetails;
+}
+
+export interface FederationNativeRbacRequest {
+  readonly grantId: string;
+  readonly peerId: string;
+  readonly subjectUserId: string;
+  readonly resource: FederationResource;
+}
+
+export interface FederationNativeRbacAccess {
+  /** Whether this user may read personal rows for this resource. */
+  readonly includePersonal: boolean;
+
+  /** Team IDs this user may read for this resource under native RBAC. */
+  readonly teamIds: readonly string[];
+}
+
+export interface FederationNativeRbacAllowedResult {
+  readonly allowed: true;
+  readonly access: FederationNativeRbacAccess;
+}
+
+export interface FederationNativeRbacDeniedResult {
+  readonly allowed: false;
+  readonly reason?: string;
+  readonly details?: FederationScopeDenyDetails;
+}
+
+export type FederationNativeRbacResult =
+  | FederationNativeRbacAllowedResult
+  | FederationNativeRbacDeniedResult;
+
+export interface FederationNativeRbacEvaluator {
+  evaluateReadAccess(request: FederationNativeRbacRequest): Promise<FederationNativeRbacResult>;
+}
+
+export interface FederationScopeEvaluationInput {
+  readonly context: FederationContext;
+  readonly resource: string;
+  readonly requestedLimit?: number;
+  readonly nativeRbac: FederationNativeRbacEvaluator;
+}
+
+export interface FederationScopeQueryFilter {
+  readonly resource: FederationResource;
+  readonly subjectUserId: string;
+  readonly includePersonal: boolean;
+  readonly teamIds: readonly string[];
+  readonly limit: number;
+  readonly maxRowsPerQuery: number;
+}
+
+export interface FederationScopeAllowedResult {
+  readonly allowed: true;
+  readonly filter: FederationScopeQueryFilter;
+}
+
+export interface FederationScopeDeniedResult {
+  readonly allowed: false;
+  readonly deny: FederationScopeDenyReason;
+}
+
+export type FederationScopeEvaluationResult =
+  | FederationScopeAllowedResult
+  | FederationScopeDeniedResult;
+
+function isFederationResource(resource: string): resource is FederationResource {
+  return federationResourceSet.has(resource);
+}
+
+function uniqueStrings(values: readonly string[]): readonly string[] {
+  return Array.from(new Set<string>(values));
+}
+
+function intersectTeamIds(
+  nativeTeamIds: readonly string[],
+  scopedTeamIds: readonly string[] | undefined,
+): readonly string[] {
+  const uniqueNativeTeamIds = uniqueStrings(nativeTeamIds);
+
+  if (scopedTeamIds === undefined) {
+    return uniqueNativeTeamIds;
+  }
+
+  const nativeSet = new Set<string>(uniqueNativeTeamIds);
+  return uniqueStrings(scopedTeamIds).filter((teamId: string): boolean => nativeSet.has(teamId));
+}
+
+function makeDenyReason(params: {
+  readonly code: FederationScopeDenyCode;
+  readonly stage: FederationScopeDenyStage;
+  readonly statusCode?: FederationScopeDenyStatus;
+  readonly message: string;
+  readonly context: FederationContext;
+  readonly resource: string;
+  readonly details?: FederationScopeDenyDetails;
+}): FederationScopeDeniedResult {
+  return {
+    allowed: false,
+    deny: {
+      code: params.code,
+      stage: params.stage,
+      statusCode: params.statusCode ?? 403,
+      message: params.message,
+      grantId: params.context.grantId,
+      peerId: params.context.peerId,
+      subjectUserId: params.context.subjectUserId,
+      resource: params.resource,
+      ...(params.details !== undefined ? { details: params.details } : {}),
+    },
+  };
+}
+
+@Injectable()
+export class FederationScopeService {
+  async evaluateAccess(
+    input: FederationScopeEvaluationInput,
+  ): Promise<FederationScopeEvaluationResult> {
+    const { context, resource, requestedLimit, nativeRbac } = input;
+
+    let scope: ReturnType<typeof parseFederationScope>;
+    try {
+      scope = parseFederationScope(context.scope);
+    } catch (error: unknown) {
+      const message =
+        error instanceof FederationScopeError
+          ? 'Federation grant scope is invalid'
+          : 'Federation grant scope could not be parsed';
+      const details = error instanceof Error ? { reason: error.message } : undefined;
+      return makeDenyReason({
+        code: 'invalid_scope',
+        stage: 'scope_parse',
+        statusCode: 400,
+        message,
+        context,
+        resource,
+        ...(details !== undefined ? { details } : {}),
+      });
+    }
+
+    if (!isFederationResource(resource)) {
+      return makeDenyReason({
+        code: 'invalid_resource',
+        stage: 'resource_allowlist',
+        message: 'Requested federation resource is not supported',
+        context,
+        resource,
+        details: { supportedResources: FEDERATION_RESOURCE_VALUES },
+      });
+    }
+
+    if (scope.excluded_resources.includes(resource)) {
+      return makeDenyReason({
+        code: 'resource_excluded',
+        stage: 'resource_exclusion',
+        message: 'Requested federation resource is explicitly excluded by grant scope',
+        context,
+        resource,
+      });
+    }
+
+    if (!scope.resources.includes(resource)) {
+      return makeDenyReason({
+        code: 'resource_not_granted',
+        stage: 'resource_allowlist',
+        message: 'Requested federation resource is not granted by scope',
+        context,
+        resource,
+        details: { grantedResources: scope.resources },
+      });
+    }
+
+    if (requestedLimit !== undefined && (!Number.isInteger(requestedLimit) || requestedLimit < 1)) {
+      return makeDenyReason({
+        code: 'invalid_limit',
+        stage: 'row_cap',
+        statusCode: 400,
+        message: 'Requested row limit must be a positive integer',
+        context,
+        resource,
+        details: { requestedLimit },
+      });
+    }
+
+    const nativeResult = await nativeRbac.evaluateReadAccess({
+      grantId: context.grantId,
+      peerId: context.peerId,
+      subjectUserId: context.subjectUserId,
+      resource,
+    });
+
+    if (!nativeResult.allowed) {
+      return makeDenyReason({
+        code: 'native_rbac_denied',
+        stage: 'native_rbac',
+        message: nativeResult.reason ?? 'Subject user is not allowed to read this resource',
+        context,
+        resource,
+        ...(nativeResult.details !== undefined ? { details: nativeResult.details } : {}),
+      });
+    }
+
+    const scopeFilter = scope.filters?.[resource];
+    const includePersonal =
+      Boolean(scopeFilter?.include_personal ?? true) && nativeResult.access.includePersonal;
+    const teamIds = intersectTeamIds(nativeResult.access.teamIds, scopeFilter?.include_teams);
+    const limit = Math.min(requestedLimit ?? scope.max_rows_per_query, scope.max_rows_per_query);
+
+    return {
+      allowed: true,
+      filter: {
+        resource,
+        subjectUserId: context.subjectUserId,
+        includePersonal,
+        teamIds,
+        limit,
+        maxRowsPerQuery: scope.max_rows_per_query,
+      },
+    };
+  }
+}