Running Linksys E4200 access point

I got one of Linksys wireless access points. The original idea was to install Linux into it with DD-WRT, but the operation failed miserably due the fact, that there are actually two kinds of E4200 APs. Guess who has the "wrong" kind. That would be my 3rd Linksys wireless access-point. I love their products due to extensive Linux-support and very high quality hardware. Now it looks like, this one didn't turn out like I planned.

Anyway, the thingie had a very old firmware and I thought that it would be a good idea to upload the newest factory firmware into it. That failed immediately, all I got was a "Image File Is Incorrect" error message. The message was spat out from the GUI almost immediately, so I decided to debug it. Here is the code I found:

var len = F.file.value.length;
var ext = new Array('.','i','m','g');
if (F.file.value == '') {
    alert(fwupgrade.upgradefile);
    return false;
}
var IMAGE = F.file.value.toLowerCase();
for (i=0; i < 4; i++) {
    if (ext[i] != IMAGE.charAt(len-4+i)){
        alert(hupgrade.wrimage);
        return false;
    }
}

Nice! The manufacturer designated file of FW_E4200_2.1.39.145204.SSA hardly matches the required .img file extension. Also on the code side: is the way of checking for the file extension completely braindead, or is it just me? Guess what would happen, if the filename would contain less than 4 characters.

It was safe to rename the file and upload the firmware. It didn't brick the thing. There seems to be plenty of people having the same issue. The unit seems to have interesting ports open, nobody knows why. Here are the port scan results:

Starting Nmap 6.25 ( http://nmap.org ) at 2013-08-07 13:47 EEST
Nmap scan report for 192.168.1.1
Host is up (0.0017s latency).
Not shown: 992 closed ports
PORT      STATE    SERVICE
53/tcp    open     domain
80/tcp    open     http
139/tcp   open     netbios-ssn
443/tcp   filtered https
445/tcp   open     microsoft-ds
8083/tcp  open     us-srv
49152/tcp open     unknown
49153/tcp open     unknown
MAC Address: 58:6D:8F:GG:2G:3G (Cisco-Linksys)

Nmap done: 1 IP address (1 host up) scanned in 1.32 seconds

There is a project to get Linux running on Marvell-chipsets also, but the site seems to be down. So, I'm linking the WikiDevi page instead: http://wikidevi.com/wiki/Linksys_E4200_v2
Hopefully that pans out and there will be support for DD-WRT some day.