Commit 4c1cf38e authored by Gaba's avatar Gaba 🦋
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Merge branch 'torsocks-notes' into 'main'

Add torsocks project notes

See merge request !9
parents bfa22950 d7d591be
......@@ -77,7 +77,7 @@ To add yourself to a group use the group's pad please.
## 2 Prototype network-namespace-based torsocks
- Pad: https://pad.riseup.net/p/2021-hackweek-network-namespace
- Notes: [torsocks](torsocks.md)
- Contact: jnewsome and/or dgoulet
- Summary: Use network namespaces (or maybe something else?) to run target software in an environment where it can't talk to the real network; it can only talk to the tor socks port and/or some "shim" adapter. Might be able to remove or lessen dependence on LD_PRELOAD (which isn't available everywhere, can be "escaped", and can be a bit fragile). If we continued to use LD_PRELOAD could at least be used to prevent accidental connections to the real network.
- Skills: C, familiarity with network namespaces and/or LD_PRELOAD would be helpful. New code could potentially be written in Rust.
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# PROJECT: Prototype network-namespace-based torsocks
## Summary: Reduce or remove torsocks's dependence on LD_PRELOAD
## Problems to address:
- Can't be completely confident that `LD_PRELOAD` intercepts all network requests.
- `LD_PRELOAD` can cause surprising breakages
- (Maybe) DNS leaks
## Solutions to explore:
- Network namespaces: Put target process(es) in a network namespace that can only talk to torsocks, getting higher confidence that there are no leaks. Stretch: create a synthetic network adapter that talks to tor, so we don't need to use `LD_PRELOAD` at all.
- SECCOMP: Create a seccomp filter that prevents network-related syscalls that don't originate from the `LD_PRELOAD`d shim, getting higher confidence that there are no leaks. Stretch: use ptrace to rewrite network-related syscalls instead of using `LD_PRELOAD`.
Alternative/fallback:
- Go through torsocks issues and increment/fix what we can through incremental improvements and cut a release. https://gitlab.torproject.org/tpo/core/torsocks/-/issues
## Skills Needed:
C, familiarity with network namespaces and/or `LD_PRELOAD` would be helpful. New code could potentially be written in Rust.
## Team:
jnewsome
~~dgoulet~~
boklm (https://gitlab.torproject.org/boklm/torsocks-netns)
## Relevant issues:
- FR to disable network: https://gitlab.torproject.org/tpo/core/torsocks/-/issues/26889. This mentions that `firejail` could be used for this. Looking at the man page for firejail, `--protocol=unix` seems like it'd do what we want.
- irssi: https://gitlab.torproject.org/tpo/core/torsocks/-/issues/11727. I'd thought there was a DNS leak, but maybe I misremembered. It looks like the issue is each process getting its own onion-address-resolution-table + irssi using multiple processes.
- torsocks support for unix sockets: https://gitlab.torproject.org/tpo/core/torsocks/-/issues/14132. (This would be let us disable net access completely)
## Notes:
- tor notes for how to set up a transparent proxy: https://gitlab.torproject.org/legacy/trac/-/wikis/doc/TransparentProxy
- Maybe we could write a wrapper script to set up a network namespace, configure all traffic in that ns to go through the transparent proxy, and then run the target program(s) in the namespace?
## Results:
- torsocks-netns: https://gitlab.torproject.org/boklm/torsocks-netns:
- Wrapper for torsocks that protects against inadvertent leaks.
- Puts torsocks + application in an empty network namespace and "smuggles" out to the tor socks port over a unix-pipe tunnel.
- No root or priveleges required!
- Proofs of concept without `torsocks/LD_PRELOAD`:
- Network namespace with ip tables rules + proxy (implemented via redsocks) to funnel everything to either tor's socks port or tor's DNS port. (Root/privelege required?)
- Tried using tor's transparent proxy functionality + iptables rules in a network namespace, but couldn't get it working. Creating a bridged adapter requires ~root. (Could use a priveleged binary like firejail if installed. firejail's default config doesn't allow it, though)
- Proof of concept using tor's shared onion pool (to address https://gitlab.torproject.org/tpo/core/torsocks/-/issues/11727, fixing torsocks+irssi)
- torsocks handles resolving onion addresses using "onion cookies"
- irssi uses different processes to resolve vs connect, so doesn't work
- tor now *natively* supports onion cookies
- Modified torsocks to use tor's native onion cookie support and successfully connected to an onion irc server
## Questions/follow-ups from demo:
- Jeremy: how does it compare to https://github.com/orjail/orjail
- Jeremy: stream isolation in these modes? (-i with torsocks)
- Matt: (torsocks.conf supports 'AllowOutboundLocalhost 0|1|2')
- Nick: Tor always returns its local addresses from a given range specified in VirtualAddrNetworkIPv[46] , so you could in theory detect them like that.
defaults are 127.192.0.0/10 and [FE80::]/10
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