mirror of
https://github.com/QubesOS/qubes-doc.git
synced 2024-12-27 16:29:28 -05:00
118 lines
4.9 KiB
Markdown
118 lines
4.9 KiB
Markdown
---
|
|
lang: en
|
|
layout: doc
|
|
permalink: /doc/vm-sudo/
|
|
redirect_from:
|
|
- /en/doc/vm-sudo/
|
|
- /doc/VMSudo/
|
|
- /wiki/VMSudo/
|
|
ref: 165
|
|
title: Passwordless root access in qubes
|
|
---
|
|
|
|
Background (`/etc/sudoers.d/qubes` in VM):
|
|
|
|
```
|
|
user ALL=(ALL) NOPASSWD: ALL
|
|
|
|
# WTF?! Have you lost your mind?!
|
|
#
|
|
# In Qubes VMs there is no point in isolating the root account from
|
|
# the user account. This is because all the user data is already
|
|
# accessible from the user account, so there is no direct benefit for
|
|
# the attacker if she could escalate to root (there is even no benefit
|
|
# in trying to install some persistent rootkits, as the VM's root
|
|
# filesystem modifications are lost upon each start of a VM).
|
|
#
|
|
# One might argue that some hypothetical attacks against the
|
|
# hypervisor or the few daemons/backends in Dom0 (so VM escape
|
|
# attacks) most likely would require root access in the VM to trigger
|
|
# the attack.
|
|
#
|
|
# That's true, but mere existence of such a bug in the hypervisor or
|
|
# Dom0 that could be exploited by a malicious VM, no matter whether
|
|
# requiring user, root, or even kernel access in the VM, would be
|
|
# FATAL. In such situation (if there was such a bug in Xen) there
|
|
# really is no comforting that: "oh, but the mitigating factor was
|
|
# that the attacker needed root in VM!" We're not M$, and we're not
|
|
# gonna BS our users that there are mitigating factors in that case,
|
|
# and for sure, root/user isolation is not a mitigating factor.
|
|
#
|
|
# Because, really, if somebody could find and exploit a bug in the Xen
|
|
# hypervisor -- as of 2016, there have been only three publicly disclosed
|
|
# exploitable bugs in the Xen hypervisor from a VM -- then it would be
|
|
# highly unlikely if that person couldn't also found a user-to-root
|
|
# escalation in VM (which as we know from history of UNIX/Linux
|
|
# happens all the time).
|
|
#
|
|
# At the same time allowing for easy user-to-root escalation in a VM
|
|
# is simply convenient for users, especially for update installation.
|
|
#
|
|
# Currently this still doesn't work as expected, because some idotic
|
|
# piece of software called PolKit uses own set of policies. We're
|
|
# planning to address this in Beta 2. (Why PolKit is an idiocy? Do a
|
|
# simple experiment: start 'xinput test' in one xterm, running as
|
|
# user, then open some app that uses PolKit and asks for root
|
|
# password, e.g. gpk-update-viewer -- observe how all the keystrokes
|
|
# with root password you enter into the "secure" PolKit dialog box can
|
|
# be seen by the xinput program...)
|
|
#
|
|
# joanna.
|
|
```
|
|
|
|
Below is a complete list of configuration made according to the above statement, with (not necessary complete) list of mechanisms depending on each of them:
|
|
|
|
1. sudo (`/etc/sudoers.d/qubes`):
|
|
|
|
```
|
|
user ALL=(ALL) NOPASSWD: ALL
|
|
(...)
|
|
```
|
|
|
|
- Easy user -> root access (main option for the user).
|
|
- `qvm-usb` (not really working, as of R2).
|
|
|
|
2. PolicyKit (`/etc/polkit-1/rules.d/00-qubes-allow-all.rules`):
|
|
|
|
```
|
|
//allow any action, detailed reasoning in sudoers.d/qubes
|
|
polkit.addRule(function(action,subject) { return polkit.Result.YES; });
|
|
```
|
|
|
|
and `/etc/polkit-1/localauthority/50-local.d/qubes-allow-all.pkla`:
|
|
|
|
```
|
|
[Qubes allow all]
|
|
Identity=*
|
|
Action=*
|
|
ResultAny=yes
|
|
ResultInactive=yes
|
|
ResultActive=yes
|
|
```
|
|
|
|
- NetworkManager configuration from normal user (`nm-applet`).
|
|
- Updates installation (`gpk-update-viewer`).
|
|
- User can use pkexec just like sudo Note: above is needed mostly because Qubes user GUI session isn't treated by PolicyKit/logind as "local" session because of the way in which X server and session is started.
|
|
Perhaps we will address this issue in the future, but this is really low priority.
|
|
Patches welcomed anyway.
|
|
|
|
3. Empty root password:
|
|
- Used for access to 'root' account from text console (`qvm-console-dispvm`) - the only way to access the VM when GUI isn't working.
|
|
- Can be used for easy 'su -' from user to root.
|
|
|
|
Replacing passwordless root access with Dom0 user prompt
|
|
--------------------------------------------------------
|
|
|
|
While the Qubes developers support the statement above, some Qubes users may wish to enable user/root isolation in VMs anyway.
|
|
We do not support this in any of our packages, but of course nothing is preventing a user from modifying his or her own system.
|
|
A list of steps to do so is provided in the [Qubes community guide, Replacing passwordless root with a dom0 prompt
|
|
](https://forum.qubes-os.org/t/replacing-passwordless-root-with-a-dom0-prompt/19074) **without any guarantee of safety, accuracy, or completeness.
|
|
Proceed at your own risk.
|
|
Do not rely on this for extra security.**
|
|
|
|
Dom0 passwordless root access
|
|
-----------------------------
|
|
|
|
There is also passwordless user->root access in dom0.
|
|
As stated in the comment in sudo configuration there (which is different from the one in individual qubes), there is really no point in user/root isolation, because all the user data (and VM management interface) is already accessible from dom0 user level, so there is nothing more to get from dom0 root account.
|