Comment by shakna | Hacker News Reader

Comment by shakna | Hacker News Reader

> A hardcoded credential vulnerability was identified in the “zyfwp” user account in some Zyxel firewalls and AP controllers. The account was designed to deliver automatic firmware updates to connected access points through FTP.

Also translated as:

In the name of "improving security" we created a backdoor, which is known throughout the entire industry as "removing all security". We are very sorry we were caught so easily.

It does not take much to understand this was a terrible idea. Or that there are so many better ways to build and deploy automatic updates. You absolutely do not need to be able to control a machine remotely to deploy automatic updates. But counting the ways they went wrong building this update system makes it extremely hard to believe that was the intent.

> After a thorough investigation, we’ve identified the vulnerable products that are within their warranty and support period and are releasing firmware patches to address the issue, as shown in the table below.

That they went to the effort of identifying their minimal viable liability and all released patches for that, makes it even more disingenuous.

This is a company whose business is supposed to be about enhancing security. They should know better.

> 2020-12-02: Zyxel requests more information about how the vulnerability was discovered

Sorry, but how did you figure it out? Can we hide it better next time?

More like- did you violate any eula’s or laws in discovering this so we can sue you and call you a “convicted criminal hacker”

>This is a company whose business is supposed to be about enhancing security. They should know better.

Except they don't.

Having owned a Zyxel NAS (comically named "NSA" back then), i can tell you their firmware, updates and support are even worse than you can imagine.

After this NAS, i vowed to never ever buy or touch any kind of Zyxel hardware again.

> You absolutely do not need to be able to control a machine remotely to deploy automatic updates.

Huh? How are you supposed to deploy the update then, or make it effective? I think the definition of "remotely control" differs somewhat from mine.

I could agree that you don't need to uniquely address a remote machine to deploy updates, but having control over the machine (if only for a moment) is the purpose of the update process.

"control remotely" as in "issue arbitrary commands" is absolutely _not_ required for an update mechanism.

The machine _itself_ can check for updates, and issue _only_ those commands that are _necessary_. You don't need complete control over a machine for an update mechanism.

But the entire update infrastructure has issues... Firmware binaries downloaded over unprotected basic FTP... No checksums... No authenticated signatures... And arbitrary commands issued at the root level.

> The machine _itself_ can check for updates, and issue _only_ those commands that are _necessary_.

The problem with this statement is that the machine doesn't know what sequence of actions is necessary to put the system into the "updated" state. If it knew, it wouldn't have to contact anything in order to update itself. It would already have known.

Where in „client pulls a signed image with a secure and trusted process from the update server, flashes it, then swaps it with its previous image“ does the update server command any control over the client?

That depends on the contents of the supplied image. But I agree, it's more about the need for the ability to take over control rather than exercising the ability.

> If it knew, it wouldn't have to contact anything in order to update itself. It would already have known.

Eh? That's how most package managers work. They only issue a very small number of commands to put them into an "updated" state. They don't generally do arbitrary things.

For example, if we take a look into aptitude, the deb packages it eventually fetches after running various authentications, contains:

+ A directory listing. (Contents-<arch>.gz)

+ Paths and checksums. (Release)

+ Signing information.

It doesn't have an arbitrary listing of commands to put it into the "updated" set - that's already decided by the format. The machine _does_ know the sequence of actions that is necessary. You don't need some kind of Turing complete monstrosity that can do absolutely anything to update it.

In the case of a _firmware update_ that's even simpler! Most of the time you're either replacing a kernel, or flashing the firmware to a pre-decided memory address. Both of those actions are decided long before you even begin issuing updates.

If you deploy a firmware update it contains new instructions that can do anything. The problem is the hardcoded credentials that an other 3rd party could dump from a device and then could be used to attack other devices. What they should have done if they wanted automatic updates was just have a public key on devices. They could then sign any updates with their private key.

Still with automatic updates you have to trust the vendor. However, with what they did updates/commands could be coming from anyone willing to dump device firmware.

Machines can pull rather than manufacturers push, using cryptographic signatures to verify origin. At no point during, say, a Linux embedded device doing an "apt-get upgrade" in a cron job, is anyone remotely controlling the machine.

I see, the difference is that I still consider it remote control even when the act of programming is separated by time from the act of execution.

...the all software in the world is a form of "remote control" on the initial installation.

I don't disagree with that :)

Let me summarize the issue:

"I was surprised to find a user account 'zyfwp' with a password hash"

"this account seemed to work on both the SSH and web interface"

"Globally, more than 100.000 devices have exposed their web interface to the internet"

Linux manages to auto update itself by fetching updates from the outside, when IT wants to do so.

Zyxel tried to add a function where THEY can access devices over the internet and do who-knows-what whenever they wanted.

And they did such a poor job of that, that they managed to give access to the devices to everybody.

For something this severe, it should be made to everyone regardless of their current 'warranty and support period' status.

You'd be surprised, but it often comes to "nobody knows how to build that 10 year old piece of firmware anymore".

This. That's why I prefer to buy devices that have known compatibility with OpenWRT.

> It seemed the vulnerability had been introduced in the latest firmware version. Even though older versions do not have this vulnerability, they do have others (such as this buffer overflow) so you should still update.

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