DDevelopment & Design

Wicket form submit not safe for redirecting to intercept page

The problem When you have a form, that anybody can see, but only logged on users can POST, you may want to redirect the user to the login page, and back to the form after login Using wicket 1.3/1.4, if you do that using redirectToInterceptPage(loginP…The problem When you have a form, that anybody can see, but only logged on users can POST, you may want to redirect the user to the login page, and back to the form after login Using wicket 1.3/1.4, if you do that using redirectToInterceptPage(loginP…

The problem

When you have a form, that anybody can see, but only logged on users can POST, you may want to redirect the user to the login page, and back to the form after login

Using wicket 1.3/1.4, if you do that using redirectToInterceptPage(loginPage) or RestartResponseAtInterceptPageException, after returning, the client will loose all the data entered to the form.

The details

The reason why this happens, is because of how redirectToInterceptPage works. It saves the URL of the requested page, and later, when continueToOriginalDestination is called, it redirects the client to the saved URL using GET. When the last call from the client was a non-ajax POST to the form, the client will be redirected without any posted data. Wicket will handle the situation issuing  HTTP 302 and redirecting the user again, but all the data is already lost.

The funny thing is that the data is actually getting to the form, because of the first POST, but then it’s overwritten with nulls on the redirected GET. To make it clear, here’s the HTTP conversation:

Client: POST http://localhost:8080/test?wicket:interface=:3:form::IFormSubmitListener:: (post to the form)
Server: HTTP 302 Moved Temporarily (the input was parsed, the model was updated, but you are being redirected to the login page because of redirectToInterceptPage or exception)
Client: GET http://localhost:8080/?wicket:interface=:4:::: 
Server: HTTP 200 OK (server is responding with the login page)
Client: POST  https://localhost:8443/j_spring_security_check.... (post login and password, here using spring security)
Server: HTTP 302 Moved Temporarily (validation is done. Now you are redirected from spring security to the page with wicket redirectToInterceptPage)
Client: GET https://localhost:8443/redirectAfterLogin  (here  redirectToInterceptPage is called)
Server: HTTP 302 Moved Temporarily (you are being redirected the original URL)
Client: GET http://localhost:8080/test?wicket:interface=:3:form::IFormSubmitListener:: (the same URL as the first POST but this time without post data. now your form is being submitted again, but with nulls instead of entered data)
Server: HTTP 302 Moved Temporarily (being redirected by wicket, because of Redirect After Post pattern)
Client: GET http://localhost:8080/?wicket:interface=:3:1::: (back on the form page)
Server: HTTP 200 OK (the form is empty by now)

As you see, if wicket would not redirect you at the end to the url requested by POST, but to the one called by last GET before the original POST, your data would be there.

The issue was reported two years ago. Doesn’t look like it’s getting fixed any time soon.

The walkaround

If you can require your users to be logged in before you show them the form, you are safe. If not, you can submit the form by AJAX. This will solve the problem, because wicket will recognize, that it cannot redirect the user to the AJAX POST target (is not exactly what the user would like to have rendered in the browser), and will redirect with GET to the URL of the last page instead, which was also requested by GET. And since the data was converted to the form model in the first POST (line 1), all is well.

And in case you don’t want to have a partial page update via AJAX, but would rather like to render the whole page, all you need to do is add setResponsePage(getPage()) to your button. For example like this:

class AjaxSendButton extends AjaxFallbackButton {
    public AjaxSendButton(String id, Form form) {
        super(id, form);
    }

    @Override
    protected void onSubmit(AjaxRequestTarget target, Form form) {
        //process your form input here
        setResponsePage(getPage());
    }
}

Now your ajax form behaves just like a non ajax form, but can be redirected to an intercept page

The catch

When submitting forms via AJAX you have to be aware, that your form may be submitted without your submit button being clicked on. This may have unforseen consequences. For the whole problem description and a solution go here

Solution Architect @ TouK

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DDevelopment & Design

Phonegap / Cordova and cross domain ssl request problem on android.

In one app I have participated, there was a use case:
  • User fill up a form.
  • User submit the form.
  • System send data via https to server and show a response.
During development there wasn’t any problem, but when we were going to release production version then some unsuspected situation occurred. I prepare the production version accordingly with standard flow for Android environment:
  • ant release
  • align
  • signing
During conduct tests on that version, every time I try to submit the form, a connection error appear. In that situation, at the first you should check whitelist in cordova settings. Every URL you want to connect to, must be explicit type in: 
res/xml/cordova.xml
If whitelist looks fine, the error is most likely caused by inner implementation of Android System. The Android WebView does not allow by default self-signed SSL certs. When app is debug-signed the SSL error is ignored, but if app is release-signed connection to untrusted services is blocked.



Workaround


You have to remember that secure connection to service with self-signed certificate is risky and unrecommended. But if you know what you are doing there is some workaround of the security problem. Behavior of method 
CordovaWebViewClient.onReceivedSslError
must be changed.


Thus add new class extended CordovaWebViewClient and override ‘onReceivedSslError’. I strongly suggest to implement custom onReceiveSslError as secure as possible. I know that the problem occours when app try connect to example.domain.com and in spite of self signed certificate the domain is trusted, so only for that case the SslError is ignored. 

public class MyWebViewClient extends CordovaWebViewClient {

   private static final String TAG = MyWebViewClient.class.getName();
   private static final String AVAILABLE_SLL_CN 
                               = "example.domain.com";

   public MyWebViewClient(DroidGap ctx) {
       super(ctx);
   }

   @Override
   public void onReceivedSslError(WebView view, 
                                  SslErrorHandler handler, 
                                  android.net.http.SslError error) {

       String errorSourceCName = error.getCertificate().
                                  getIssuedTo().getCName();

       if( AVAILABLE_SLL_CN.equals(errorSourceCName) ) {
           Log.i(TAG, "Detect ssl connection error: " + 
                       error.toString() + 
                       „ so the error is ignored”);

           handler.proceed();
           return;
       }

       super.onReceivedSslError(view, handler, error);
   }
}
Next step is forcing yours app to  use custom implementation of WebViewClient. 

public class Start extends DroidGap
{
   private static final String TAG = Start.class.getName();

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState);
       super.setIntegerProperty("splashscreen", R.drawable.splash);
       super.init();

       MyWebViewClient myWebViewClient = new MyWebViewClient(this);
       myWebViewClient.setWebView(this.appView);

       this.appView.setWebViewClient(myWebViewClient);
       
       // yours code

   }
}
That is all ypu have to do if minSdk of yours app is greater or equals 8. In older version of Android there is no class 
android.net.http.SslError
So in class MyCordovaWebViewClient class there are errors because compliator doesn’t see SslError class. Fortunately Android is(was) open source, so it is easy to find source of the class. There is no inpediments to ‘upgrade’ app and just add the file to project. I suggest to keep original packages. Thus after all operations the source tree looks like:

Class SslError placed in source tree. 
 Now the app created in release mode can connect via https to services with self-signed SSl certificates.
DDevelopment & Design

Grails render as JSON catch

One of a reasons your controller doesn't render a proper response in JSON format might be wrong package name that you use. It is easy to overlook. Import are on top of a file, you look at your code and everything seems to be fine. Except response is still not in JSON format.

Consider this simple controller:

class RestJsonCatchController {
def grailsJson() {
render([first: 'foo', second: 5] as grails.converters.JSON)
    }

def netSfJson() {
render([first: 'foo', second: 5] as net.sf.json.JSON)
    }
}

And now, with finger crossed... We have a winner!

$ curl localhost:8080/example/restJsonCatch/grailsJson
{"first":"foo","second":5}
$ curl localhost:8080/example/restJsonCatch/netSfJson
{first=foo, second=5}

As you can see only grails.converters.JSON converts your response to JSON format. There is no such converter for net.sf.json.JSON, so Grails has no converter to apply and it renders Map normally.

Conclusion: always carefully look at your imports if you're working with JSON in Grails!

Edit: Burt suggested that this is a bug. I've submitted JIRA issue here: GRAILS-9622 render as class that is not a codec should throw exception