add userinfo endpoint

src/main.rs

@@ -404,23 +404,27 @@ async fn authenticate_endpoint(mut req: Request<AppState>) -> tide::Result {
         }
     }
 
-    // The token is random because there are no resources protected by the token anyway.
-    let mut access_token = [0u8; 32];
-    SystemRandom::new().fill(&mut access_token)?;
-    let access_token = base64_coder::URL_SAFE_NO_PAD.encode(&access_token);
+    let id_token = create_id_token(
+        req.state(),
+        &credentials.0,
+        &code_info.account,
+        code_info.nonce,
+    )?;
 
     req.state()
         .successful_logins
         .fetch_add(1, Ordering::Relaxed);
 
     // give access code
-    Ok(Response::builder(200).body(json!({
-        "access_token": access_token,
-        "token_type": "Bearer",
-        "expires_in": TOKEN_EXPIRATION,
-        "id_token": create_id_token(req.state(), &credentials.0, &code_info.account, code_info.nonce)?,
-        "scope": "openid profile email"
-    })).into())
+    Ok(Response::builder(200)
+        .body(json!({
+            "access_token": id_token,
+            "token_type": "Bearer",
+            "expires_in": TOKEN_EXPIRATION,
+            "id_token": id_token,
+            "scope": "openid profile email"
+        }))
+        .into())
 }
 
 async fn jwks_endpoint(req: Request<AppState>) -> tide::Result {
@@ -445,6 +449,7 @@ async fn configuration_endpoint(req: Request<AppState>) -> tide::Result {
             "issuer": uri,
             "authorization_endpoint": uri.join("/authorize")?,
             "token_endpoint": uri.join("/token")?,
+            "userinfo_endpoint": uri.join("/userinfo")?,
             "jwks_uri": uri.join("/jwks")?,
             "response_types_supported": ["code"],
             "subject_types_supported": ["pairwise"],
@@ -493,6 +498,60 @@ logins_success {}
         .into())
 }
 
+/// We expect the ID token as our access token
+async fn userinfo_endpoint(req: Request<AppState>) -> tide::Result {
+    // this is all wrapped, because if something fails, then its the
+    // client's fault anyways (if there aren't any bugs, oh well...)
+    let resp = || {
+        let jwt = req
+            .header("Authorization")
+            .and_then(|v| v.get(0).unwrap().as_str().strip_prefix("Bearer "))
+            .ok_or(anyhow!("no bearer token"))?; // extract token
+
+        let (message, signature) = jwt.rsplit_once(".").ok_or(anyhow!("bad token form"))?;
+
+        let pk: ring::rsa::PublicKeyComponents<Vec<u8>> = req.state().signing_key.public().into();
+
+        pk.verify(
+            &ring::signature::RSA_PKCS1_2048_8192_SHA256,
+            message.as_bytes(),
+            &base64_coder::URL_SAFE_NO_PAD.decode(signature)?,
+        )?;
+
+        let (_header, claims) = message.rsplit_once(".").ok_or(anyhow!("bad token form"))?;
+        let decoded_claims = base64_coder::URL_SAFE_NO_PAD.decode(claims)?;
+        let decoded_claims: serde_json::Value = serde_json::from_slice(&decoded_claims)?;
+
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .expect("no time travelling allowed before 1970")
+            .as_secs();
+
+        if decoded_claims["exp"]
+            .as_u64()
+            .ok_or(anyhow!("invalid exp"))?
+            < now
+        {
+            Err(anyhow!("token expired"))
+        } else {
+            Ok(Response::builder(200)
+                .content_type("application/json")
+                .body(decoded_claims)
+                .build())
+        }
+    };
+
+    #[allow(unused_variables)] // rustc complains when building in release mode
+    resp().or_else(|e| {
+        #[cfg(debug_assertions)]
+        log::debug!("userinfo error: {}", e);
+
+        Ok(Response::builder(401)
+            .header("WWW-Authenticate", "Bearer error=\"invalid_token\"")
+            .build())
+    })
+}
+
 pub struct AuthStore {
     pub auths: HashMap<String, Authorization>,
     pub expirations: LinkedList<(String, u64)>,
@@ -563,6 +622,7 @@ async fn main() -> Result<()> {
         .get(configuration_endpoint);
     app.at("/new-account").get(create_account_endpoint);
     app.at("/metrics").get(metrics_endpoint);
+    app.at("/userinfo").get(userinfo_endpoint);
 
     auto_serve_dir!(app, "/static", "static");