Blank admin page after successful login for one specific IP address ...

Question

Since a few days logging in to our Magento (1.8.1) backend is impossible - but only from one specific IP address, the IP address that used to be set at System -> Configuration -> Advanced -> Developer -> Developer Client Restrictions.

The issue at hand is that the login seems to be successful, yet I receive a blank admin page instead of the dashboard.

While trying to troubleshoot this issue I have of course changed this IP address to another IP address (1.2.3.4), cleared sessions and caches, even rebooted our server, but no luck.

Still receiving a blank page.

I activated all of the possible logging / developer options hoping this would give me a clue of what's wrong, maybe even on infamous fatal error, but no. Just a white screen and no suspicious or clueful entries in nginx, php or magento logs.

What makes it more strange is that this problem happens on multiple computers/browsers behind one specific (and fixed) IP address, yet if - for instance - I connect one of these computers to a 3G Hotspot (and as such connect using a dynamic IP address) I am able to successfully login to our backend. Now if I disconnect from the hotspot and on to the regular wifi (and as such continue using the fixed / problematic IP address) it works perfectly. I can navigate all pages of the backend -including the dashboard- without any issues.

Once logged off or timed out the issue re-appears.

Someone somewhere any clue on why this is happening and how to solve this?

Answer 1

In the end I found the problem. It was in the Amasty Errors Detector module (http://amasty.com/errors-detector.html). This module has functionality to log failed login attempts and put these IP addresses on a blacklist.

Even though we are using 1Password at this specific IP address apparently 4 failed logins where recorded and this IP address was put on the blacklist.

Completely forgot about the functionality of this extension and while looking for something else I saw this IP address on the blacklist.. Luckily the extension comes with a whitelist as well ;)

Answer 2

I think the admin screen becomes blank, is with the cookies that are set by the magento. Follow the below procedure.

Go to app/code/core/Mage/Core/Model/Session/Abstract/Varien.php file within your magento directory. At line no.88 you will find the below code.

$cookieParams = array(
    'lifetime' => $cookie->getLifetime(),
    'path'     => $cookie->getPath(),
    'domain'   => $cookie->getConfigDomain(),
    'secure'   => $cookie->isSecure(),
    'httponly' => $cookie->getHttponly()
);

Replace the above code with below:

$cookieParams = array(
    'lifetime' => $cookie->getLifetime(),
    'path'     => $cookie->getPath()
//  'domain'   => $cookie->getConfigDomain(),
//  'secure'   => $cookie->isSecure(),
//  'httponly' => $cookie->getHttponly()
);

Clear the cache and browser cache too and reload the page.