While Tor Browser has automatic updates, why the Tor client doesn't have an integrated automatic update mechanism?

Question

While Tor Browser has automatic updates, why the Tor client doesn't have an integrated automatic update mechanism? Because if you look at this graph

You can see that a lot of relays are still using old versions such as 0.2.4 ! It seems i2p already has an automatic updater that works... So why doesn't Tor come with one?

Answer 1

Many reasons:

1. The Tor Project doesn't control how it's software is installed on any given system and cannot ensure the automatic updater could run
2. Tor being able to write to it's own binary is a means for a hacker to gain persistence.
3. Tor being able to write to it's own binary is a privileged escalation vulnerability on most common installations.
4. Running a diverse software set helps prevent mass exploitation by a single exploit.
5. 0.2.4 isn't considered broken yet and is still within the set of recommended versions.
6. Some administrators would, for obvious reasons, look suspiciously at the ability of the Tor Project to push and execute software on their systems with no interaction on their part.

Conversely:

The Tor Project runs repos for Debian, Ubuntu, CentOS and Redhat which allow system administrators to use a centralised software update mechanism to update Tor when an update is available.

Answer 2

Auto-updating/unattended-updating mechanisms can be a doomsday backdoor, Moxie Marlynspike has demonstrated it well on DEFCON - it allows/opens-a-potential-ability to replace the updated system's any component by an attacker