fapi2.diff

diff --git a/examples/oauth.ts b/examples/fapi2.ts
index cc6d632..80ec0f4 100644
--- a/examples/oauth.ts
+++ b/examples/fapi2.ts
@@ -8,12 +8,22 @@ let algorithm!:
   | 'oidc' /* For .well-known/openid-configuration discovery */
   | undefined /* Defaults to 'oidc' */
 let client_id!: string
-let client_secret!: string
 /**
  * Value used in the authorization request as redirect_uri pre-registered at the Authorization
  * Server.
  */
 let redirect_uri!: string
+/**
+ * In order to take full advantage of DPoP you shall generate a random private key for every
+ * session. In the browser environment you shall use IndexedDB to persist the generated
+ * CryptoKeyPair.
+ */
+let DPoP!: CryptoKeyPair
+/**
+ * A key that the client has pre-registered at the Authorization Server for use with Private Key JWT
+ * client authentication method.
+ */
+let clientPrivateKey!: CryptoKey
 
 // End of prerequisites
 
@@ -23,38 +33,68 @@ const as = await oauth
 
 const client: oauth.Client = {
   client_id,
-  client_secret,
-  token_endpoint_auth_method: 'client_secret_basic',
+  token_endpoint_auth_method: 'private_key_jwt',
 }
 
 const code_challenge_method = 'S256'
 /**
  * The following MUST be generated for every redirect to the authorization_endpoint. You must store
- * the code_verifier and nonce in the end-user session such that it can be recovered as the user
- * gets redirected from the authorization server back to your application.
+ * the code_verifier in the end-user session such that it can be recovered as the user gets
+ * redirected from the authorization server back to your application.
  */
 const code_verifier = oauth.generateRandomCodeVerifier()
 const code_challenge = await oauth.calculatePKCECodeChallenge(code_verifier)
-let state: string | undefined
+
+// Pushed Authorization Request & Response (PAR)
+let request_uri: string
+{
+  const params = new URLSearchParams()
+  params.set('client_id', client.client_id)
+  params.set('code_challenge', code_challenge)
+  params.set('code_challenge_method', code_challenge_method)
+  params.set('redirect_uri', redirect_uri)
+  params.set('response_type', 'code')
+  params.set('scope', 'api:read')
+
+  const pushedAuthorizationRequest = () =>
+    oauth.pushedAuthorizationRequest(as, client, params, {
+      DPoP,
+      clientPrivateKey,
+    })
+  let response = await pushedAuthorizationRequest()
+  let challenges: oauth.WWWAuthenticateChallenge[] | undefined
+  if ((challenges = oauth.parseWwwAuthenticateChallenges(response))) {
+    for (const challenge of challenges) {
+      console.error('WWW-Authenticate Challenge', challenge)
+    }
+    throw new Error() // Handle WWW-Authenticate Challenges as needed
+  }
+
+  const processPushedAuthorizationResponse = () =>
+    oauth.processPushedAuthorizationResponse(as, client, response)
+  let result = await processPushedAuthorizationResponse()
+  if (oauth.isOAuth2Error(result)) {
+    console.error('Error Response', result)
+    if (result.error === 'use_dpop_nonce') {
+      // the AS-signalled nonce is now cached, retrying
+      response = await pushedAuthorizationRequest()
+      result = await processPushedAuthorizationResponse()
+      if (oauth.isOAuth2Error(result)) {
+        throw new Error() // Handle OAuth 2.0 response body error
+      }
+    } else {
+      throw new Error() // Handle OAuth 2.0 response body error
+    }
+  }
+
+  ;({ request_uri } = result)
+}
 
 {
   // redirect user to as.authorization_endpoint
   const authorizationUrl = new URL(as.authorization_endpoint!)
   authorizationUrl.searchParams.set('client_id', client.client_id)
-  authorizationUrl.searchParams.set('redirect_uri', redirect_uri)
-  authorizationUrl.searchParams.set('response_type', 'code')
-  authorizationUrl.searchParams.set('scope', 'api:read')
-  authorizationUrl.searchParams.set('code_challenge', code_challenge)
-  authorizationUrl.searchParams.set('code_challenge_method', code_challenge_method)
-
-  /**
-   * We cannot be sure the AS supports PKCE so we're going to use state too. Use of PKCE is
-   * backwards compatible even if the AS doesn't support it which is why we're using it regardless.
-   */
-  if (as.code_challenge_methods_supported?.includes('S256') !== true) {
-    state = oauth.generateRandomState()
-    authorizationUrl.searchParams.set('state', state)
-  }
+  authorizationUrl.searchParams.set('request_uri', request_uri)
 
   // now redirect the user to authorizationUrl.href
 }
@@ -65,19 +105,16 @@ let access_token: string
 {
   // @ts-expect-error
   const currentUrl: URL = getCurrentUrl()
-  const params = oauth.validateAuthResponse(as, client, currentUrl, state)
+  const params = oauth.validateAuthResponse(as, client, currentUrl)
   if (oauth.isOAuth2Error(params)) {
     console.error('Error Response', params)
     throw new Error() // Handle OAuth 2.0 redirect error
   }
 
-  const response = await oauth.authorizationCodeGrantRequest(
-    as,
-    client,
-    params,
-    redirect_uri,
-    code_verifier,
-  )
+  const authorizationCodeGrantRequest = () =>
+    oauth.authorizationCodeGrantRequest(as, client, params, redirect_uri, code_verifier, { DPoP })
+
+  let response = await authorizationCodeGrantRequest()
 
   let challenges: oauth.WWWAuthenticateChallenge[] | undefined
   if ((challenges = oauth.parseWwwAuthenticateChallenges(response))) {
@@ -87,10 +124,22 @@ let access_token: string
     throw new Error() // Handle WWW-Authenticate Challenges as needed
   }
 
-  const result = await oauth.processAuthorizationCodeOAuth2Response(as, client, response)
+  const processAuthorizationCodeOAuth2Response = () =>
+    oauth.processAuthorizationCodeOAuth2Response(as, client, response)
+
+  let result = await processAuthorizationCodeOAuth2Response()
   if (oauth.isOAuth2Error(result)) {
     console.error('Error Response', result)
-    throw new Error() // Handle OAuth 2.0 response body error
+    if (result.error === 'use_dpop_nonce') {
+      // the AS-signalled nonce is now cached, retrying
+      response = await authorizationCodeGrantRequest()
+      result = await processAuthorizationCodeOAuth2Response()
+      if (oauth.isOAuth2Error(result)) {
+        throw new Error() // Handle OAuth 2.0 response body error
+      }
+    } else {
+      throw new Error() // Handle OAuth 2.0 response body error
+    }
   }
 
   console.log('Access Token Response', result)
@@ -99,18 +148,33 @@ let access_token: string
 
 // Protected Resource Request
 {
-  const response = await oauth.protectedResourceRequest(
-    access_token,
-    'GET',
-    new URL('https://rs.example.com/api'),
-  )
+  const protectedResourceRequest = () =>
+    oauth.protectedResourceRequest(
+      access_token,
+      'GET',
+      new URL('https://rs.example.com/api'),
+      undefined,
+      undefined,
+      { DPoP },
+    )
+  let response = await protectedResourceRequest()
 
   let challenges: oauth.WWWAuthenticateChallenge[] | undefined
   if ((challenges = oauth.parseWwwAuthenticateChallenges(response))) {
-    for (const challenge of challenges) {
-      console.error('WWW-Authenticate Challenge', challenge)
+    const { 0: challenge, length } = challenges
+    if (
+      length === 1 &&
+      challenge.scheme === 'dpop' &&
+      challenge.parameters.error === 'use_dpop_nonce'
+    ) {
+      // the AS-signalled nonce is now cached, retrying
+      response = await protectedResourceRequest()
+    } else {
+      for (const challenge of challenges) {
+        console.error('WWW-Authenticate Challenge', challenge)
+      }
+      throw new Error() // Handle WWW-Authenticate Challenges as needed
     }
-    throw new Error() // Handle WWW-Authenticate Challenges as needed
   }
 
   console.log('Protected Resource Response', await response.json())