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Tenda firmware (multiple versions) contains hidden authentication backdoor

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Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#91

> The associated username is not validated, so any provided username will succeed when paired with the backdoor password. Great. I am really wondering why should the customers trust these manufacturers. At this point I would not use any router with vendor-provided black box firmware. Full stop. I would always install OpenWRT or something similar on it before using it. And if that is not possible for whatever reason,…

Hm, do you ever go over 1gbit? If my understanding is correct, good affordable routers like Mikrotik's CCR2004 are fully closed, so the only option is to build your own shitty box which will be much less energy efficient than their specialized switch chips.

Because of lax security in commercial routers, this backdoor being a prime example of what I'm concerned about, I'd have my own shitty box as a firewall between them and my other kit anyway, so there isn't an efficiency saving either way. It is just a choice of where the walls are, and therefor where my shitty box(es) is/are, not whether my shitty box exists or not.

Currently my primary shitty box router does everything wrt external connectivity and a bought AP/router sits inside offering WiFi. I'd like to remove that AP completely with a WiFi adaptor controlled by my shitty box, but I've not got around to that as it would mean learning to configure a mesh (and so at least one more of my own shitty boxes!) to get good coverage everywhere (I only have a small place, but there are still a couple of blind-ish spots depending on where I put the primary AP). Not trusting a bought router/AP to not have back doors like this raises the question: if they are going to add backdoors for direct outside connections, what is to stop the firmware instead/also trying to tunnel out and letting unwanted connections in that way? (other than this having less “plausible deniability” once discovered)

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#92
post #83

Typical for Chinese companies. Of course US companies also provide backdoors, but more official and more secure..

No backdoor is secure. Read the "Keys under Doormats" paper from 2015:

https://www.schneier.com/wp-content/uploads/2016/09/paper-ke...

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#93

Oh this is amazing! I have a few of their cube routers sitting around and I always hated how app-locked their firmware was when it really is just a wifi repeater with a few extras (mesh) on top. Root access will do wonders to bypassing the app now (and also disabling their ping-for-green-light mechanism which spams the network with a constant dns resolution to microsoft.com lol). Also honest take this looks less like…

Yes, it is randomized but due to a quirk in the universal probability waveform it always randomizes to 'rzadmin'. Scientists are baffled.

Pulled out of fair hat. Guaranteed to be random.

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#94
post #5

> Tenda is a supplier of home and business network devices such as routers, switches, wireless access points, and video surveillance equipment. I was unfamiliar with Tenda. > Shenzhen Tenda Technology Co.,Ltd. ( https://www.tendacn.com/us/profile ) Tenda may just rebrand, right? It seems like many chinese brands will either rebrand or have a 'competing' brand with the same internals but different externals. (I have n…

My ex used to work in their sales department lol. But I'd seen them anyway, in the context of cheap unmanaged switches on Amazon. They are not a state owned company or anything so I doubt this is anything too nefarious, likely just absolutely not giving a crap about quality.

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#95
post #21
post #13

And this is why I handroll my own routers/firewalls, using commodity hardware and a Linux distribution.

Looking to do this to get off stock isp leased router. What's your hardware/distro rec?

You can use basically any hardware. I've done it with trash-picked laptops and USB ethernet adapters. Best option these days is a N100/N150 mini-pc with multiple NICs onboard, but with the price of everything going up maybe trashpicking will make a return.

https://nbailey.ca/post/router

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#96

Earlier quoted context omitted.

I mean, it's 99% sure this was supposed to be a debug feature...

and "accidentally" they forgot to disable it when releasing

Believe it or not, shit happens in the software business.

I know this from personal experience.

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#98
post #76

Earlier quoted context omitted.

His point is that in security, the opposite applies. The supposed "incompetence" is just plausible deniability for a malicious act.

Yes, and my point is that hasn’t been the case in my experience.

It's because you (like me) aren't quite as paranoid as security people are. Personally I couldn't sleep at night if I was security people.

It's really a matter of context. Security people tend to only be involved when things are already nefarious where as boring old normal people like us see get to see the mundane everyday mistakes so not just the nefarious bits.

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#99

Earlier quoted context omitted.

That backdoor is so up front about it. We might as well call it a frontdoor.

I mean, it's 99% sure this was supposed to be a debug feature...

I have done this accidentally at least once - we shipped a full-stack app, and telemetry started lighting up that on certain older phones and browsers (no points for guessing which brand and browser), the release version didn't load. The minifier did something in the release build that it didn't like.

So after a quick test, it was decided to deploy the debug version of just the frontend as a bandaid. Next day we saw we managed to deploy the debug version of the backend with admin stuff like this as well..

Re: Tenda firmware (multiple versions) contains hidden authentication backdoor

#100
post #39

Earlier quoted context omitted.

Sounds like a convenience feature for a dev that they forgot to remove before distribution, since it's this poorly hidden.

In computer security, never attribute to ignorance that which is adequately explained by malice.

Dunno, if I were to backdoor a piece of my code, I would definitely put in an exploit instead of a deliberate bypass.

Plausible deniability is important.

A lot of the stuff I worked on already had glaring issues like that without me having to add it..

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