1 Filename: 107-uptime-sanity-checking.txt
2 Title: Uptime Sanity Checking
5 Author: Kevin Bauer & Damon McCoy
8 Implemented-In: 0.2.0.x
12 This document describes how to cap the uptime that is used when computing
13 which routers are marked as stable such that highly stable routers cannot
14 be displaced by malicious routers that report extremely high uptime
17 This is similar to how bandwidth is capped at 1.5MB/s.
21 It has been pointed out that an attacker can displace all stable nodes and
22 entry guard nodes by reporting high uptimes. This is an easy fix that will
23 prevent highly stable nodes from being displaced.
25 Security implications:
27 It should decrease the effectiveness of routing attacks that report high
28 uptimes while not impacting the normal routing algorithms.
32 So we could patch Section 3.1 of dir-spec.txt to say:
34 "Stable" -- A router is 'Stable' if it is running, valid, not
35 hibernating, and either its uptime is at least the median uptime for
36 known running, valid, non-hibernating routers, or its uptime is at
37 least 30 days. Routers are never called stable if they are running
38 a version of Tor known to drop circuits stupidly. (0.1.1.10-alpha
39 through 0.1.1.16-rc are stupid this way.)
43 There should be no compatibility issues due to uptime capping.
47 Implemented and merged into dir-spec in 0.2.0.0-alpha-dev (r9788).
51 Initially, this proposal set the maximum at 60 days, not 30; the 30 day
52 limit and spec wording was suggested by Roger in an or-dev post on 9 March
55 This proposal also led to 108-mtbf-based-stability.txt