backend-app-api,auth: move token typ claim to be a header param

Co-authored-by: Camila Belo <camilaibs@gmail.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/backend-app-api/src/services/implementations/auth/authServiceFactory.ts

@@ -22,16 +22,13 @@ import {
   BackstageServicePrincipal,
   BackstageNonePrincipal,
   BackstageUserPrincipal,
-  IdentityService,
   coreServices,
   createServiceFactory,
 } from '@backstage/backend-plugin-api';
 import { AuthenticationError } from '@backstage/errors';
-import {
-  IdentityApiGetIdentityRequest,
-  TokenTypes,
-} from '@backstage/plugin-auth-node';
-import { base64url, decodeJwt } from 'jose';
+import { TokenTypes } from '@backstage/plugin-auth-node';
+import { base64url, decodeJwt, decodeProtectedHeader } from 'jose';
+import { UserTokenHandler } from './UserTokenHandler';
 
 /** @internal */
 export type InternalBackstageCredentials<TPrincipal = unknown> =
@@ -115,7 +112,8 @@ class DefaultAuthService implements AuthService {
 
   // allowLimitedAccess is currently ignored, since we currently always use the full user tokens
   async authenticate(token: string): Promise<BackstageCredentials> {
-    const { typ, sub, aud } = decodeJwt(token);
+    const { typ } = decodeProtectedHeader(token);
+    const { sub, aud } = decodeJwt(token);
 
     if (typ) {
       switch (typ) {
@@ -244,13 +242,13 @@ class DefaultAuthService implements AuthService {
     const limitedUserToken = [
       base64url.encode(
         JSON.stringify({
+          typ: 'vnd.backstage.limited-user',
           alg: header.alg,
           kid: header.kid,
         }),
       ),
       base64url.encode(
         JSON.stringify({
-          typ: 'vnd.backstage.limited-user',
           sub: payload.sub,
           ent: payload.ent,
           iat: payload.iat,

plugins/auth-backend/src/identity/TokenFactory.ts

@@ -115,14 +115,17 @@ export class TokenFactory implements TokenIssuer {
     const signingKey = await importJWK(key);
 
     const uip = await this.createUserIdentityClaim({
-      header: { alg: key.alg, kid: key.kid },
-      payload: { typ: TokenTypes.limitedUser.typClaim, sub, ent, iat, exp },
+      header: {
+        typ: TokenTypes.limitedUser.typParam,
+        alg: key.alg,
+        kid: key.kid,
+      },
+      payload: { sub, ent, iat, exp },
       key: signingKey,
     });
 
     const claims: BackstageTokenPayload = {
       ...additionalClaims,
-      typ: TokenTypes.user.typClaim,
       iss,
       sub,
       ent,
@@ -133,7 +136,11 @@ export class TokenFactory implements TokenIssuer {
     };
 
     const token = await new SignJWT(claims)
-      .setProtectedHeader({ alg: key.alg, kid: key.kid })
+      .setProtectedHeader({
+        typ: TokenTypes.user.typParam,
+        alg: key.alg,
+        kid: key.kid,
+      })
       .sign(signingKey);
 
     if (token.length > MAX_TOKEN_LENGTH) {
@@ -243,6 +250,7 @@ export class TokenFactory implements TokenIssuer {
   // JWS.
   private async createUserIdentityClaim(options: {
     header: {
+      typ: string;
       alg: string;
       kid?: string;
     };
@@ -257,12 +265,12 @@ export class TokenFactory implements TokenIssuer {
     // then append the signature.
 
     const header = {
+      typ: options.header.typ,
       alg: options.header.alg,
       ...(options.header.kid ? { kid: options.header.kid } : {}),
     };
 
     const payload = {
-      typ: options.payload.typ,
       sub: options.payload.sub,
       ent: options.payload.ent,
       iat: options.payload.iat,

plugins/auth-node/src/types.ts

@@ -383,14 +383,14 @@ export type CookieConfigurer = (ctx: {
  */
 export const TokenTypes = Object.freeze({
   user: Object.freeze({
-    typClaim: 'vnd.backstage.user',
+    typParam: 'vnd.backstage.user',
     audClaim: 'backstage',
   }),
   limitedUser: Object.freeze({
-    typClaim: 'vnd.backstage.limited-user',
+    typParam: 'vnd.backstage.limited-user',
   }),
   service: Object.freeze({
-    typClaim: 'vnd.backstage.service',
+    typParam: 'vnd.backstage.service',
   }),
 });
 
@@ -400,11 +400,6 @@ export const TokenTypes = Object.freeze({
  * @public
  */
 export interface BackstageTokenPayload {
-  /**
-   * The token type
-   */
-  typ: typeof TokenTypes.user.typClaim;
-
   /**
    * The issuer of the token, currently the discovery URL of the auth backend
    */
@@ -452,11 +447,6 @@ export interface BackstageTokenPayload {
  * @public
  */
 export interface BackstageUserIdentityProofPayload {
-  /**
-   * The token type
-   */
-  typ: typeof TokenTypes.limitedUser.typClaim;
-
   /**
    * The entity ref of the user
    */