[RFC] Safe remote Dom0 terminals

[Jean-Philippe Ouellet]

Hello,

While trying to get graphics pass-through working, I found myself
needing to see the output of an interactive terminal on a remote
machine.

The general idea is to split the input and output paths, using your
same trusted keyboard input path as before, and sending only the
output over a unidirectional channel to a remote machine.

All escape sequences are passed as normal, preserving functionality of
interactive things (tmux, top, vim, etc.).

I have documented my approach [1], and opened a PR to add it to the
docs under the debugging section [2] so that we have a better way to
track specific suggestions / objections / etc.

Thoughts?

[1]: https://github.com/jpouellet/qubes-doc/blob/safe-remote-ttys/debugging/safe-remote-ttys.md
[2]: https://github.com/QubesOS/qubes-doc/pull/225

[Marek Marczykowski-Górecki]

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On Sun, Nov 20, 2016 at 07:20:14PM -0500, Jean-Philippe Ouellet wrote:
> Hello,
>
> While trying to get graphics pass-through working, I found myself
> needing to see the output of an interactive terminal on a remote
> machine.
>
> The general idea is to split the input and output paths, using your
> same trusted keyboard input path as before, and sending only the
> output over a unidirectional channel to a remote machine.
>
> All escape sequences are passed as normal, preserving functionality of
> interactive things (tmux, top, vim, etc.).
>
> I have documented my approach [1], and opened a PR to add it to the
> docs under the debugging section [2] so that we have a better way to
> track specific suggestions / objections / etc.
>
> Thoughts?

As said on github: pretty smart approach! In principle looks good, but I
haven't tested it.

> [1]: https://github.com/jpouellet/qubes-doc/blob/safe-remote-ttys/debugging/safe-remote-ttys.md
> [2]: https://github.com/QubesOS/qubes-doc/pull/225
>

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[Frédéric Pierret (fepitre)]

Hi,
I'm trying your method but I have trouble with it:

When I try the first (to a different VM), xterm appears well but when entering anything it stays blocked, like if there were no response. Do you have an idea?

Thank you

[Jean-Philippe Ouellet]

On Mon, Oct 16, 2017 at 2:18 AM, Frédéric Pierret (fepitre)
<epitre....@gmail.com> wrote:
> Hi,
> I'm trying your method but I have trouble with it:
>
> When I try the first (to a different VM), xterm appears well but when
> entering anything it stays blocked, like if there were no response. Do you
> have an idea?
>
> Thank you
> Le lundi 21 novembre 2016 01:20:42 UTC+1, Jean-Philippe Ouellet a écrit :

It sounds like you're probably just typing into the wrong terminal.

You're not supposed to type into the xterm that opens, that's just to
show you the output. You type into the original terminal you started
the script(1) session in. The stuff you type in the original terminal
should be mirrored to the 2nd one.

It's an intentionally unidirectional flow of information such that the
machine you display the output on (the machine with the new xterm
window) doesn't need to be trusted because it does not control
anything.

>> Hello,
>>
>> While trying to get graphics pass-through working, I found myself
>> needing to see the output of an interactive terminal on a remote
>> machine.
>>
>> The general idea is to split the input and output paths, using your
>> same trusted keyboard input path as before, and sending only the
>> output over a unidirectional channel to a remote machine.
>>
>> All escape sequences are passed as normal, preserving functionality of
>> interactive things (tmux, top, vim, etc.).
>>
>> I have documented my approach [1], and opened a PR to add it to the
>> docs under the debugging section [2] so that we have a better way to
>> track specific suggestions / objections / etc.
>>
>> Thoughts?
>>
>> [1]:
>> https://github.com/jpouellet/qubes-doc/blob/safe-remote-ttys/debugging/safe-remote-ttys.md
>> [2]: https://github.com/QubesOS/qubes-doc/pull/225
>
>

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