fix(passport): ignore static state and nonce passed to Strategy() (#556)

Co-authored-by: Filip Skokan <panva.ip@gmail.com>

docs/README.md

@@ -840,7 +840,7 @@ Creates a new Strategy
 
 - `options`: `<Object>`
   - `client`: `<Client>` Client instance. The strategy will use it.
-  - `params`: `<Object>` Authorization Request parameters. The strategy will use these.
+  - `params`: `<Object>` Authorization Request parameters. The strategy will use these for every authorization request.
   - `passReqToCallback`: `<boolean>` Boolean specifying whether the verify function should get
     the request object as first argument instead. **Default:** 'false'
   - `usePKCE`: `<boolean>` &vert; `<string>` The PKCE method to use. When 'true' it will resolve based
@@ -857,6 +857,16 @@ Creates a new Strategy
 
 ---
 
+The strategy automatically generates `state` and `nonce` parameters when required. To provide one for a flow where it is optional (for example the `nonce` for the Authorization Code Flow), it can be passed in the optional `options` argument to `passport.authenticate()`:
+
+```js
+app.post('/auth/oidc', function(req, res, next) {
+  passport.authenticate('oidc', { nonce: crypto.randomBytes(16).toString('base64url') })(req, res, next);
+});
+```
+
+---
+
 ## generators
 
 <!-- TOC generators START -->

lib/passport_strategy.js

@@ -41,6 +41,11 @@ function OpenIDConnectStrategy(
   this._usePKCE = usePKCE;
   this._key = sessionKey || `oidc:${url.parse(this._issuer.issuer).hostname}`;
   this._params = cloneDeep(params);
+
+  // state and nonce should be provided or generated below on each authenticate()
+  delete this._params.state;
+  delete this._params.nonce;
+
   this._extras = cloneDeep(extras);
 
   if (!this._params.response_type) this._params.response_type = resolveResponseType.call(client);