Intercept POST requests in a WebView

Question

I'm developping an Android application filtering the requests (with a white list) and using a custom SSLSocketFactory. For this, I've developed a custom WebViewClient and I have overridden the shouldInterceptRequest method. I can filter and use my SocketFactory with the GET requests but I can't intercept the POST requests.

So, is there a way to intercept the POST requests in a WebView ?

Here is the code of the shouldInterceptRequest method :

public final WebResourceResponse shouldInterceptRequest(WebView view, String urlStr) {
    URI uri = URI.create(urlStr);
    String scheme = uri.getScheme();
    // If scheme not http(s), let the default webview manage it
    if(!"http".equals(scheme) && !"https".equals(scheme)) {
        return null;
    }
    URL url = uri.toURL();

    if(doCancelRequest(url)) {
        // Empty response
        Log.d(TAG, "URL filtered: " + url);
        return new WebResourceResponse("text/plain", "UTF-8", new EmptyInputStream());

    } else {
        Log.d(TAG, "URL: " + url);

        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestProperty("User-Agent", mSettings.getUserAgentString());

        // Configure connections
        configureConnection(conn);

        String mimeType = conn.getContentType();
        String encoding = conn.getContentEncoding();

        if(mimeType != null && mimeType.contains(CONTENT_TYPE_SPLIT)) {
            String[] split = mimeType.split(CONTENT_TYPE_SPLIT);
            mimeType = split[0];

            Matcher matcher = CONTENT_TYPE_PATTERN.matcher(split[1]);
            if(matcher.find()) {
                encoding = matcher.group(1);
            }
        }

        InputStream is = conn.getInputStream();
        return new WebResourceResponse(mimeType, encoding, is);
    }
}

Answer 1

I was facing the same issue a few days ago.

So I built a library that solves it:

https://github.com/KonstantinSchubert/request_data_webviewclient

It is a WebViewClient with a custom WebResourceRequest that contains the POST/PUT/... payload of XMLHttpRequest requests.

It only works for these though - not for forms and other kind of request sources.

The hack works, basically, by injecting a script into the HTML that intercepts XMLHttpRequest calls. It records the post/put/... content and sends it to an android.webkit.JavascriptInterface. There, the request is stashed until the shouldInterceptRequest method is called by Android ...