Tor Relay Setup

Use case for an entry node

• why run an entry node for your friends?
  • b/c the entry node is the only node that knows the origin of a request that passes through a tor circuit
  • if an attacker controls a lot of entry and exit nodes, they can run correlation attacks to connect entry packets to exit packets and defeat anonymity
  • if you control the entry node, you mitigate the possibility of attacker correlating entry and exit
  • (and running an exit node is hard)

Implementation Pointers

• don't do it on a VPS
  • security posture only as strong as its weakest link, smaller the system, the less likely a weaker link
• if you control your own hardware, the attack surface is smaller (eliminates a ton of uncertainties: what's generating entropy, what's in actual packets, where is machine?)
• use your favorite OS
  • debian dominates the space (which creates monoculture)
  • consider Open BSD, but work with whatever you're most comfortable with
  • use sshd with a password, use ed5519 (NOT RSA), change keys on regular basis
  • don't run *anything* else on it (not apache, note nginx, etc...)
  • restrict sshd access by ip address
  • remove config support for bluetooth, wifi, mysql, *anything* not tor
  • use a host-based firewall and network-based firewall
  • know your os enough to harden it, block all other possible uses
  • if running server on mac, might need to use MacPorts

• which release?
  • alpha & stable
  • if you can't update a lot (eg: incorporating into a product), use stable
  • if you can look at it weekly and care about resiliency against emerging attacks, run alpha

• config file (`.torrc`)
  • many are 1500-ish lines long: don't worry if you feel intimidated by it. that's natural!!! don't give up!!!!
  • tor has *fantastic* documentation: tor website manual, `man tor`, the config file has extensive commenting
  • you only need 5 lines to set up a working relay
  • for a sample config see `torbsd.github.io`(~ 300 lines long, configures a bunch of logging and has a bunch of comments)
  • minimally: need (1) socks port 0 (for talking to localhost), (2) or port 9001 (for onion routing over TCP)
  • can block exit traffic easily
  • can enable stats easily:
    • 2-digit ISO country codes for who is using service and how many
    • ie: for entry and bridge usage
  • and look at them in `var/db/tor` or `var/tor`

• hardware
  • doesn't need to be that beefy
  • minimally: 2gb of ram, dual core w/ 2ghz processing power
  • look at pcegnines.ch (alix boards are good and $100)

• host it on a physical box in a data center -> how to shop for data center?
  • look for dedicated colocation hosting
  • give you a box & a console login
  • rackspace: $100/month
  • NYII is good in NYC
  • if you can get cheap colo space in canada, it's maybe worth it...

Gotchas

• some risks
  • if you run a public node, your ip might get blocked by some sites (banks, hulu)
  • don't run public relay node at home, safe to run a bridge at home
    • worth running a bridge from home, use extra
  • ideal sites: universities, big software companies w/ social mission
• if you're running an entry relay for friends, make it public (diversifies traffic)
• some troubleshooting
  • cloudflare blocks tor (or captcha filters it), you can turn this off, many sites don't

• consensus weight
  • the higher "consensus weight", the more a node will get used
  • how do get consensus weight? reliablity, availability over time

• failure mode to avoid
  • under-resourced ngo's offer to be providers, mess it up, endganger people
  • also: it's impersonal: relies on people trusting an organization, when they could isntead place trust in a pre-existing social trust network of friends, family, etc..

Context & Training

• if running a bridge and want to give someone access:
  • give someone IP, name, & fingerprint, *NOT* just the IP

• if running a relay: TRAIN PEOPLE!!!
  • have a dedicated box that's dedicated to running tor (maybe has tails installed)

• how to talk about it:
  • mailing lists, irc channel, tor exchange site
  • tor helpdesks by country
  • tor talk
  • access now

Getting Help

• is there an information commons for rules of thumb?
  • things like good colos, good ISPs, config files, etc...
  • answer: no.
  • this is largely handled informally ATM, email G.!

• lots of sites to look at shape of network
  • atlas.torproject.org has good statistics
  • torstatus.__(?)