What is the risks/benefits of setting USB and Net to be the same?

[apparatus]

I’m honestly trying to understand the specific case you’re talking about in which the sys-net qube can compromise the devices in sys-usb qube so I’m asking for a details of the configuration/qubes usage that could lead to it.
If you feel that I’m trolling than we can just stop the discussion.

[tempmail]

@apparatus

I’m honestly trying to understand the specific case you’re talking about in which the sys-net qube can compromise the devices in sys-usb qube so I’m asking for a details of the configuration/qubes usage that could lead to it.

I’ll try one more time and then give up on this B&F.

1. @fslover looks like he understood what I’m talking about and quoted this topic:
   Which one is more secure: "sys-usb" or "sys-net as sys-usb"?

On that short topic, also another topic is quoted, so I’ll re-qoute it here

Running ethernet sys-net in PVH mode

After several months of learning Qubes, I realized that the ethernet sys-net (not to say wifi) is the weakest link in Qubes, only to find out that it was already been discussed here, which proves what I concluded: I decided to start a new topic due to its visibility and the idea I got, but please merge it with above if you find it more appropriate. Now, after thinking through and reading a lot, these are the facts: Ethernet is safer than internal or external wifi. Ethernet sys-net has t…

That topic is short too. If you read it (which makes me think you didn’t, otherwise you’d ask what is not clear there, not here), it is exactly the situation where you can compromise your sys-usb via sys-net.

2. You could have your ethernet controller attached to sys-net, while having any other network device (internal or external) attached to USB controller(s). I’m repeating myself for the last time here.
   So you choose to go online via your USB network device online (in parallel with sys-net or alone, it doesn’t matter). So, that scenario would compromise your USB devices too, and what’s more dangerous - controller on which USB network device is attached to, and even more dangerous, all other USB controllers that are attached to the same sys-usb, regardless of the fact that you have separate sys-net and sys-usb.

3. I can attach some PCI and USB controllers to a sys-net, and other USB controllers to a sys-usb. All USB devices attached to a sys-net will be compromised once sys-net is compromised, regardless of the fact that you have separate sys-net and sys-usb.

So your claim

@apparatus

If you have separate sys-net and sys-usb qube then sys-net compromise using network won’t affect your USB devices in sys-usb.

… is not correct and complete (see 2. and 3.) and could mislead users to a false sense of security, because your claim is correct in only one scenario:

• user have all network devices and controllers they’re attached to in a sys-net, and devices from those controller(s) aren’t later attached to sys-usb and vice versa, and you’re not attaching any other USB device to that controller residing in a sys-net.

I tried to point this, but it looks like you’re insisting your claim is one and only that is correct, so I’m leaving you there.

From this point on, I’d reply only users that are further interested in explanation, but only if they confirmed they read all the quoted topics, and the posts here, explicitly quoting claims that aren’t clear enough for them.

[gonzalo-bulnes]

Moderation note:

By the time one feels the need to write abrasive comments or state own assumptions beyond what people tell of their motivations, it might be time to take a step back. If a topic is not yielding expected outcomes, sometimes giving it some time for other folks to join the conversation goes a long way.

Quick abrasive two-people conversations are less likely to encourage anyone to join, and the forum isn’t an appropriate place to discuss private grievances.

[apparatus]

Ok, I understand your point now, thank you for the clarification.
I was talking about two default configurations provided by the Qubes OS installer:

@apparatus

The Qubes OS installer offers you two configuration choices:

• separate sys-net and sys-usb qubes
  Use a qube to hold all USB controllers option is checked
  Use sys-net qube for both networking and USB devices option is unchecked
  In this case all PCI network controllers will be attached to sys-net and all PCI USB network controllers will be attached to sys-usb.
• conjoined sys-net/sys-usb qube
  Use a qube to hold all USB controllers option is checked
  Use sys-net qube for both networking and USB devices option is checked
  In this case both all PCI network controllers and all PCI USB network controllers will be attached to sys-net qube.

I agree that my statement:

@apparatus

If you have separate sys-net and sys-usb qube then sys-net compromise using network won’t affect your USB devices in sys-usb.

Won’t be true for all cases e.g. if user decides to make any changes to the default sys-net/sys-usb configuration created by Qubes OS installer.

E.g. as I stated before:

@apparatus

So you mean attaching USB device from sys-usb to sys-net?
Then if sys-net is compromised using network then the attacker will have access to the USB device passed to sys-net and maybe this could lead to further compromise of the USB controller in sys-usb and compromise of other USB devices.
But it’s still better than conjoined sys-net/sys-usb where compromise using network will directly lead to the USB devices compromise.

But you answer:

@tempmail

@apparatus

So you mean attaching USB device from sys-usb to sys-net?

I never said that. Can you quote it, please?

Confused me and I thought that you meant something else.

If user adds a PCI USB controller from sys-usb to sys-net to use a USB network adapter connected to this USB controller and then attach some other USB devices to the same USB controller this won’t conflict with my statement but the other USB devices connected to the PCI USB controller attached to the sys-net qube will be compromised as well with sys-net compromise so it could worth to mention this.

Also as mentioned in the topic that you linked, there is also a concern that having a PCI network controller in sys-net could lead to a side-channel attack (e.g. DMA attack) and this could lead to the compromise of USB devices in sys-usb as well. But there is a greater concern in this situation, because this attack could lead to a dom0 compromise as well.

[tempmail]

Now, that’s an add up and as I see it, now the topic has the most comprehensive overview on the much broader potential issues the subject of this topic actually hides (arises), than it might look at the first glance, especially to the novices.