Repository: badgateway/oauth2-client (ts)

Issue:
Revoke token
Hi there, looking at the client, I don't see a way to revoke a token. I believe (correct me if I'm wrong) that this is part of the OAuth spec, so it seems reasonable that the client ought to support it. For instance, the discovery server I'm working with returns a `revocation_endpoint`.

If there's already a way to do this with the client, I apologize. Please point me in the right direction. Otherwise, I would be happy to take a stab at a PR.

Pull request description:
Add support for token revocation
This PR adds support for token revocation. It's implemented similarly to how token introspection is implemented. Let me know what you think. Happy to write tests too just let me know how you'd like them structured and where. I didn't see an obvious place for the tests to live.

Usage:

```javascript
const client = new OAuth2Client({
  // ...
  
  // Can also be auto-discovered if discoveryEndpoint is supplied
  revocationEndpoint: '/revoke'
});

const token = await client.clientCredentials();

await client.revoke(token);

// can also supply tokenTypeHint (default is 'access_token')
await client.revoke(token, 'access_token');

// To revoke a refresh token
await client.revoke(token, 'refresh_token');
```

Fixes #125 

Patch:
diff --git a/README.md b/README.md
index fd4257b..0ea5fbe 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ since Node 18 (but it works with Polyfills on Node 14 and 16).
 
 ## Highlights
 
-* 11KB minified (3.7KB gzipped).
+* 12KB minified (3.8KB gzipped).
 * No dependencies.
 * `authorization_code` grant with optional [PKCE][1] support.
 * `password` and `client_credentials` grant.
@@ -18,7 +18,7 @@ since Node 18 (but it works with Polyfills on Node 14 and 16).
 * OAuth2 endpoint discovery via the Server metadata document ([RFC8414][2]).
 * OAuth2 Token Introspection ([RFC7662][3]).
 * Resource Indicators for OAuth 2.0 ([RFC8707][5]).
-
+* OAuth2 Token Revocation ([RFC7009][6]).
 
 ## Installation
 
@@ -440,3 +440,4 @@ if (global.btoa === undefined) {
 [3]: https://datatracker.ietf.org/doc/html/rfc7662 "OAuth 2.0 Token Introspection"
 [4]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Crypto_API "Web Crypto API"
 [5]: https://datatracker.ietf.org/doc/html/rfc8707 "https://datatracker.ietf.org/doc/html/rfc8707"
+[6]: https://datatracker.ietf.org/doc/html/rfc7009 "OAuth 2.0 Token Revocation"
diff --git a/changelog.md b/changelog.md
index 61056c1..5cf406b 100644
--- a/changelog.md
+++ b/changelog.md
@@ -6,8 +6,9 @@ Changelog
 
 * Fix for #128: If there's no secret, we should never use Basic auth to encode
   the `client_id`.
-* Support for the 'resource' parameter from RFC 8707.
-* Add support for "scope" parameter to "refresh().
+* Support for the `resource` parameter from RFC 8707.
+* Add support for `scope` parameter to `refresh()`.
+* Support for RFC 7009, Token Revocation.
 
 
 2.2.4 (2023-09-05)
diff --git a/src/client.ts b/src/client.ts
index 0e626a8..ae00b2b 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -5,7 +5,9 @@ import {
   IntrospectionRequest,
   IntrospectionResponse,
   PasswordRequest,
+  OAuth2TokenTypeHint,
   RefreshRequest,
+  RevocationRequest,
   ServerMetadataResponse,
   TokenResponse,
 } from './messages';
@@ -104,6 +106,14 @@ export interface ClientSettings {
    */
   introspectionEndpoint?: string;
 
+  /**
+   * Revocation endpoint.
+   *
+   * Required for revoking tokens. Not supported by all servers.
+   * If not provided we'll try to discover it, or otherwise default to /revoke
+   */
+  revocationEndpoint?: string;
+
   /**
    * OAuth 2.0 Authorization Server Metadata endpoint or OpenID
    * Connect Discovery 1.0 endpoint.
@@ -135,7 +145,7 @@ export interface ClientSettings {
 }
 
 
-type OAuth2Endpoint = 'tokenEndpoint' | 'authorizationEndpoint' | 'discoveryEndpoint' | 'introspectionEndpoint';
+type OAuth2Endpoint = 'tokenEndpoint' | 'authorizationEndpoint' | 'discoveryEndpoint' | 'introspectionEndpoint' | 'revocationEndpoint';
 
 export class OAuth2Client {
 
@@ -244,6 +254,27 @@ export class OAuth2Client {
 
   }
 
+  /**
+   * Revoke a token
+   *
+   * This will revoke a token, provided that the server supports this feature.
+   *
+   * @see https://datatracker.ietf.org/doc/html/rfc7009
+   */
+  async revoke(token: OAuth2Token, tokenTypeHint: OAuth2TokenTypeHint = 'access_token'): Promise<void> {
+    let tokenValue = token.accessToken;
+    if (tokenTypeHint === 'refresh_token') {
+      tokenValue = token.refreshToken!;
+    }
+
+    const body: RevocationRequest = {
+      token: tokenValue,
+      token_type_hint: tokenTypeHint,
+    };
+    return this.request('revocationEndpoint', body);
+
+  }
+
   /**
    * Returns a url for an OAuth2 endpoint.
    *
@@ -277,6 +308,8 @@ export class OAuth2Client {
         return resolve('/.well-known/oauth-authorization-server', this.settings.server);
       case 'introspectionEndpoint':
         return resolve('/introspect', this.settings.server);
+      case 'revocationEndpoint':
+        return resolve('/revoke', this.settings.server);
     }
 
   }
@@ -314,6 +347,7 @@ export class OAuth2Client {
       ['authorization_endpoint', 'authorizationEndpoint'],
       ['token_endpoint', 'tokenEndpoint'],
       ['introspection_endpoint', 'introspectionEndpoint'],
+      ['revocation_endpoint', 'revocationEndpoint'],
     ] as const;
 
     if (this.serverMetadata === null) return;
@@ -334,6 +368,7 @@ export class OAuth2Client {
    */
   async request(endpoint: 'tokenEndpoint', body: RefreshRequest | ClientCredentialsRequest | PasswordRequest | AuthorizationCodeRequest): Promise<TokenResponse>;
   async request(endpoint: 'introspectionEndpoint', body: IntrospectionRequest): Promise<IntrospectionResponse>;
+  async request(endpoint: 'revocationEndpoint', body: RevocationRequest): Promise<void>;
   async request(endpoint: OAuth2Endpoint, body: Record<string, any>): Promise<unknown> {
 
     const uri = await this.getEndpoint(endpoint);
@@ -378,24 +413,24 @@ export class OAuth2Client {
       headers,
     });
 
+    let responseBody;
+    if (resp.status !== 204 && resp.headers.has('Content-Type') && resp.headers.get('Content-Type')!.startsWith('application/json')) {
+      responseBody = await resp.json();
+    }
     if (resp.ok) {
-      return await resp.json();
+      return responseBody;
     }
 
-    let jsonError;
     let errorMessage;
     let oauth2Code;
-    if (resp.headers.has('Content-Type') && resp.headers.get('Content-Type')!.startsWith('application/json')) {
-      jsonError = await resp.json();
-    }
 
-    if (jsonError?.error) {
+    if (responseBody.error) {
       // This is likely an OAUth2-formatted error
-      errorMessage = 'OAuth2 error ' + jsonError.error + '.';
-      if (jsonError.error_description) {
-        errorMessage += ' ' + jsonError.error_description;
+      errorMessage = 'OAuth2 error ' + responseBody.error + '.';
+      if (responseBody.error_description) {
+        errorMessage += ' ' + responseBody.error_description;
       }
-      oauth2Code = jsonError.error;
+      oauth2Code = responseBody.error;
 
     } else {
       errorMessage = 'HTTP Error ' + resp.status + ' ' + resp.statusText;
diff --git a/src/messages.ts b/src/messages.ts
index 72adff3..0aa5961 100644
--- a/src/messages.ts
+++ b/src/messages.ts
@@ -281,6 +281,16 @@ export type IntrospectionResponse = {
 
 }
 
+/**
+ * Revocaton request.
+ *
+ * https://datatracker.ietf.org/doc/html/rfc7009#section-2.1
+ */
+export type RevocationRequest = {
+  token: string;
+  token_type_hint?: OAuth2TokenTypeHint;
+}
+
 export type OAuth2ErrorCode =
   | 'invalid_request'
   | 'invalid_client'
@@ -293,4 +303,3 @@ export type OAuth2ErrorCode =
    * RFC 8707
    */
   | 'invalid_target';
-


Test patch:
diff --git a/test/revoke.ts b/test/revoke.ts
new file mode 100644
index 0000000..0ea5851
--- /dev/null
+++ b/test/revoke.ts
@@ -0,0 +1,68 @@
+import { testServer } from './test-server';
+import { OAuth2Client } from '../src';
+import { expect } from 'chai';
+
+describe('Token revocation', () => {
+  const server = testServer();
+  describe('should revoke access token when requested', async () => {
+
+    const client = new OAuth2Client({
+      server: server.url,
+      tokenEndpoint: '/token',
+      revocationEndpoint: '/revoke',
+      clientId: 'test-client-id',
+      clientSecret: 'test-client-secret',
+    });
+
+    const token = await client.clientCredentials();
+
+    describe('When token type hint is not specified', () => {
+      it('should assume token type is access token', async () => {
+        await client.revoke(token);
+
+        const request = server.lastRequest();
+        expect(request.body).to.eql({
+          token: token.accessToken,
+          token_type_hint: 'access_token',
+        });
+      });
+    });
+
+    describe('When token type is specified as access token', () => {
+      it('should supply access token', async () => {
+        await client.revoke(token, 'access_token');
+
+        const request = server.lastRequest();
+        expect(request.body).to.eql({
+          token: token.accessToken,
+          token_type_hint: 'access_token',
+        });
+      });
+    });
+
+    describe('When token type is specified as refresh token', () => {
+      it('should supply access token', async () => {
+        await client.revoke(token, 'refresh_token');
+
+        const request = server.lastRequest();
+        expect(request.body).to.eql({
+          token: token.refreshToken,
+          token_type_hint: 'refresh_token',
+        });
+      });
+    });
+  });
+
+  describe('Discovery', () => {
+    const client = new OAuth2Client({
+      server: server.url,
+      discoveryEndpoint: '/discover',
+      clientId: 'test-client-id',
+    });
+
+    it('Should discover revocation endpoint', async () => {
+      const result = await client.getEndpoint('revocationEndpoint');
+      expect(result).to.equal(server.url + '/revoke');
+    });
+  });
+});
diff --git a/test/test-server.ts b/test/test-server.ts
index df6ddb8..40cdefa 100644
--- a/test/test-server.ts
+++ b/test/test-server.ts
@@ -27,6 +27,8 @@ export function testServer() {
     return next();
   });
   app.use(issueToken);
+  app.use(revokeToken);
+  app.use(discover);
   const port = 40000 + Math.round(Math.random()*9999);
   const server = app.listen(port);
 
@@ -65,3 +67,27 @@ const issueToken: Middleware = (ctx, next) => {
   };
 
 };
+
+
+const revokeToken: Middleware = (ctx, next) => {
+
+  if (ctx.path !== '/revoke') {
+    return next();
+  }
+
+  ctx.response.type = 'application/octet-stream';
+  ctx.response.body = 'SUCCESS!';
+};
+
+
+const discover: Middleware = (ctx, next) => {
+
+  if (ctx.path !== '/discover') {
+    return next();
+  }
+
+  ctx.response.type = 'application/json';
+  ctx.response.body = {
+    revocation_endpoint: '/revoke',
+  };
+};