Authorization flow handoff

src/server/auth/crypto.ts

@@ -0,0 +1,5 @@
+import crypto from "node:crypto";
+
+export function generateToken(): string {
+  return crypto.randomBytes(32).toString("hex");
+}

src/server/auth/handlers/authorize.ts

@@ -1,20 +1,19 @@
 import { RequestHandler } from "express";
 import { z } from "zod";
-import { OAuthRegisteredClientsStore } from "../clients.js";
 import { isValidUrl } from "../validation.js";
+import { OAuthServerProvider } from "../provider.js";
 
 export type AuthorizationHandlerOptions = {
-  /**
-   * A store used to read information about registered OAuth clients.
-   */
-  store: OAuthRegisteredClientsStore;
+  provider: OAuthServerProvider;
 };
 
+// Parameters that must be validated in order to issue redirects.
 const ClientAuthorizationParamsSchema = z.object({
   client_id: z.string(),
   redirect_uri: z.string().optional().refine((value) => value === undefined || isValidUrl(value), { message: "redirect_uri must be a valid URL" }),
 });
 
+// Parameters that must be validated for a successful authorization request. Failure can be reported to the redirect URI.
 const RequestAuthorizationParamsSchema = z.object({
   response_type: z.literal("code"),
   code_challenge: z.string(),
@@ -23,7 +22,7 @@ const RequestAuthorizationParamsSchema = z.object({
   state: z.string().optional(),
 });
 
-export function authorizationHandler({ store }: AuthorizationHandlerOptions): RequestHandler {
+export function authorizationHandler({ provider }: AuthorizationHandlerOptions): RequestHandler {
   return async (req, res) => {
     if (req.method !== "GET" && req.method !== "POST") {
       res.status(405).end("Method Not Allowed");
@@ -38,7 +37,7 @@ export function authorizationHandler({ store }: AuthorizationHandlerOptions): Re
       return;
     }
 
-    const client = await store.getClient(client_id);
+    const client = await provider.clientsStore.getClient(client_id);
     if (!client) {
       res.status(400).end("Bad Request: invalid client_id");
       return;
@@ -67,8 +66,9 @@ export function authorizationHandler({ store }: AuthorizationHandlerOptions): Re
       return;
     }
 
+    let requestedScopes: string[] = [];
     if (params.scope !== undefined && client.scope !== undefined) {
-      const requestedScopes = params.scope.split(" ");
+      requestedScopes = params.scope.split(" ");
       const allowedScopes = new Set(client.scope.split(" "));
 
       // If any requested scope is not in the client's registered scopes, error out
@@ -83,8 +83,12 @@ export function authorizationHandler({ store }: AuthorizationHandlerOptions): Re
       }
     }
 
-    // TODO: Store code challenge
-    // TODO: Generate authorization code
-    // TODO: Redirect to redirect_uri (handle in calling code)
+    await provider.authorize({
+      client,
+      state: params.state,
+      scopes: requestedScopes,
+      redirectUri: redirect_uri,
+      codeChallenge: params.code_challenge,
+    }, res);
   };
 }

src/server/auth/handlers/register.ts

@@ -8,7 +8,7 @@ export type ClientRegistrationHandlerOptions = {
   /**
    * A store used to save information about dynamically registered OAuth clients.
    */
-  store: OAuthRegisteredClientsStore;
+  clientsStore: OAuthRegisteredClientsStore;
 
   /**
    * The number of seconds after which to expire issued client secrets, or 0 to prevent expiration of client secrets (not recommended).
@@ -20,8 +20,8 @@ export type ClientRegistrationHandlerOptions = {
 
 const DEFAULT_CLIENT_SECRET_EXPIRY_SECONDS = 30 * 24 * 60 * 60; // 30 days
 
-export function clientRegistrationHandler({ store, clientSecretExpirySeconds = DEFAULT_CLIENT_SECRET_EXPIRY_SECONDS }: ClientRegistrationHandlerOptions): RequestHandler {
-  if (!store.registerClient) {
+export function clientRegistrationHandler({ clientsStore, clientSecretExpirySeconds = DEFAULT_CLIENT_SECRET_EXPIRY_SECONDS }: ClientRegistrationHandlerOptions): RequestHandler {
+  if (!clientsStore.registerClient) {
     throw new Error("Client registration store does not support registering clients");
   }
 
@@ -55,7 +55,7 @@ export function clientRegistrationHandler({ store, clientSecretExpirySeconds = D
       client_secret_expires_at: clientSecretExpirySeconds > 0 ? clientIdIssuedAt + clientSecretExpirySeconds : 0
     };
 
-    clientInfo = await store.registerClient!(clientInfo);
+    clientInfo = await clientsStore.registerClient!(clientInfo);
     return clientInfo;
   }
 

src/server/auth/provider.ts

@@ -0,0 +1,32 @@
+import { Response } from "express";
+import { OAuthRegisteredClientsStore } from "./clients.js";
+import { OAuthClientInformationFull } from "../../shared/auth.js";
+
+export type AuthorizationParams = {
+  client: OAuthClientInformationFull;
+  state?: string;
+  scopes?: string[];
+  codeChallenge: string;
+  redirectUri: string;
+};
+
+/**
+ * Implements an end-to-end OAuth server.
+ */
+export interface OAuthServerProvider {
+  /**
+   * A store used to read information about registered OAuth clients.
+   */
+  get clientsStore(): OAuthRegisteredClientsStore;
+
+  /**
+   * Begins the authorization flow, which can either be implemented by this server itself or via redirection to a separate authorization server. 
+   * 
+   * An authorization code can be generated using the `generateToken` function.
+   * 
+   * This server must eventually issue a redirect with an authorization response or an error response to the given redirect URI. Per OAuth 2.1:
+   * - In the successful case, the redirect MUST include the `code` and `state` (if present) query parameters.
+   * - In the error case, the redirect MUST include the `error` query parameter, and MAY include an optional `error_description` query parameter.
+   */
+  authorize(params: AuthorizationParams, res: Response): Promise<void>;
+}