revisit handling of /var/lib/dbus/machine-id

[phabricator-migrator]

Information

ID: 582
PHID: PHID-TASK-5jh4m7266hal3mv2k2is
Author: Patrick
Status at Migration Time: open
Priority at Migration Time: Normal

Description

• [apparmor] [profile: plugin-container] the dbus machine-id: deny or allow 'r'?
• https://labs.riseup.net/code/issues/7100#change-64065

Comments

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madaidan

2019-05-10 17:27:48 UTC

Would it cause any issues if the machine-id was just deleted or replaced with a bunch of 0s?

What would happen if the permissions for /etc/machine-id and /var/lib/dbus/machine-id were restricted to root only?

Would it be possible to do either of these?

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Patrick

2019-05-11 07:57:43 UTC

! In T582#18461, @madaidan wrote:
Would it cause any issues if the machine-id was just deleted or replaced with a bunch of 0s?

Could be.

What would happen if the permissions for /etc/machine-id and /var/lib/dbus/machine-id were restricted to root only?

[apparmor] [profile: plugin-container] the dbus machine-id: deny or allow 'r'? says it is used for various things so it might break some things.

Would it be possible to do either of these?

Possible, yes. Since these files aren’t owned by any packages it is easy to ship them.

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madaidan

2019-05-11 17:27:32 UTC

[apparmor] [profile: plugin-container] the dbus machine-id: deny or allow 'r'? says it is used for various things so it might break some things.

Wouldn’t using a fake machine-id e.g. a bunch of zeroes fix this? The programs are still able to use a machine-id and it isn’t unique.

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Patrick

2019-05-12 01:41:41 UTC

madaidan (madaidan):

madaidan added a comment.

[apparmor] [profile: plugin-container] the dbus machine-id: deny or allow 'r'? says it is used for various things so it might break some things.

Wouldn’t using a fake machine-id e.g. a bunch of zeroes fix this?

Using something similar. Not using all zeros. A generated
/var/lib/dbus/machine-id which is shared among all Whonix users.

dist-base-files/var/lib/dbus/machine-id at master · Kicksecure/dist-base-files · GitHub

I don’t think using all zeros would be superior to a generated one. Pros
all zeros: more obvious to reviewer it’s non-standard. Cons all zeros:
might fail a sanity test of some application? Pros generated: won’t fail
any sanity test. Cons generated: not obvious to reviewer that it’s
shared among all Whonix users.

All zero vs the current shared one probably makes no big difference.

The question that Tails asks in their issue tracker:

Decide what to do with machine-id (#7100) · Issues · tails / tails · GitLab

Modern GNU/Linux tools (D-Bus, systemd) relies more and more on /etc/machine-id and/or /var/lib/dbus/machine-id (depending on the OS, versions, etc.). In most situations we care about, if not all, this ID should not be leaked to the network. If it is, then:

• if we set the same machine-id everywhere, then users are all in the same anonymity set; but this also leaks that they’re using Tails
• if we set unique machine-id on boot, then we don’t leak that users are using Tails, and applications that rely on machine-id working on the LAN work; OTOH, if machine-id leaks on the Internet, then the fact that users are not in the same anonymity set can be a problem

We should first evaluate if/how machine-id can be leaked, and then think about this all, and decide something.

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madaidan

2019-05-12 12:36:08 UTC

The way it is now looks fine. Why would it need to be changed?

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Patrick

2019-05-12 15:36:53 UTC

Maybe there is no need. It’s just when Tails has a ticket, we should
check it at Whonix too. Thank you for looking into this, too!

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Patrick

2019-06-27 08:33:51 UTC

Will keep watching what Tails is doing.