Re: [tor-relays] Relay configuration for FreedomBox

2014-03-23 Thread Roger Dingledine
On Tue, Mar 18, 2014 at 10:59:30PM -0400, James Valleroy wrote:
> The FreedomBox project [1] is planning to include Tor in the upcoming
> 0.2 release. FreedomBox is intended to be used as an always-on server,
> so its Tor node has been configured as a bridge relay.
> 
> There is also a need for FreedomBoxes to be able to find each other
> regardless of location or restrictive firewall. This feature is not
> yet completely implemented for FreedomBox, but it will likely involve
> each box running a Tor hidden service, and making the initial
> connection to other boxes over the Tor network.

Running as a bridge and a hidden service at the same time is likely fine,
but you should read through
https://blog.torproject.org/blog/protecting-bridge-operators-probing-attacks
to be aware of some potential issues there.

In short, running the bridge could make it easier for somebody
to guess-and-check whether that hidden service address is
associated with that bridge. So if the hidden service is primarily a
reachability-despite-NATs thing, rather than a "you'll never find out
where I am" thing, sounds great.

> Here is the configuration that we are currently using in /etc/tor/torrc:
> 
> ORPort 4431
> BridgeRelay 1
> Exitpolicy reject *:*

Are these things going to be on the network directly, i.e. without
requiring manual port forwarding by the operator? If so, you might
explore whether you prefer "ORPort auto" for more variety.

Also, if these things are going to *be* the network connection (I've
lost track of what all freedombox might be), you might also look at the
contributed traffic priority script:
https://gitweb.torproject.org/tor.git/blob/HEAD:/contrib/linux-tor-prio.sh
but a) if it's just a bridge, it's probably not so big a deal in terms
of competing with the user's traffic, and b) it looks like that script
really wants you to tell it about the network's speed, which will be
hard for you to guess. So nice idea in theory, but probably not worthwhile
in practice.

--Roger

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Re: [tor-relays] Relay configuration for FreedomBox

2014-03-23 Thread Roger Dingledine
On Sat, Mar 22, 2014 at 01:03:43PM -0700, Lance Hathaway wrote:
> On the plus side, obfs3 is still pretty strong, and it's one of the
> common pluggable transports right now. Scramblesuit is not live in the
> official bundles yet (AFAIK), but it just released and has some pretty
> robust-looking defenses against active probing and other attacks. If
> you're working on something new to deploy, these should be included,
> without a doubt. They may indeed be deprecated in future, and in the
> worst case may become unusable or make the bridge more susceptible to
> being blocked. But if you go with a plain bridge or obfs2, you're
> already in your worst-case scenario. You have nothing to lose and
> everything to gain by enabling the newest pluggable transports.

Agreed. If the goal in setting it up as a bridge is to be useful to
users who are otherwise censored from the Tor network, then running
pluggable transports like obfs3 and ScrambleSuit will go a long way
towards actually doing that.

For context, currently Tor works out-of-the-box (you don't even need a
bridge) in nearly all countries except China, where vanilla bridges and
obfs2 don't work currently:
https://blog.torproject.org/blog/how-to-read-our-china-usage-graphs

Periodically Iran and Syria block SSL by DPI, which also takes out
vanilla bridges.

If you want to be conservative, pick obfs3 and wait for ScrambleSuit
to get more mature.

> I would highly recommend adding the Tor package repository to the
> FreedomBoxes. As explained in [0], this won't always give you the
> latest version of tor, but it will provide security fixes. My hunch is
> that it will almost always also be a little fresher than Debian
> stable.

Yes -- I would consider doing this as much for security as for anything
else. Debian stable can lag pretty far behind the actual Tor stable
releases (depending on which year you're looking).

--Roger

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Re: [tor-relays] Relay configuration for FreedomBox

2014-03-22 Thread Lance Hathaway
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On 22/03/2014 11:56 AM, James Valleroy wrote:
> Thanks for the information. Is it likely that obfs3 and
> scramblesuit will be usable in the long-term? Or will they need to
> be deprecated at some point like obfs2?
> 
> Also, if obfs3 or scramblesuit were deprecated, but some
> FreedomBoxes continued to run those transports, what would be the
> result? Would the worst case be that the bridge is no longer usable
> by some, as in [0]?
> 
> The reason that I'm asking is that FreedomBox is currently working 
> within Debian "testing" but our target is Debian "stable". Once
> our packaged configuration is frozen for the next stable release,
> it will be more difficult for us to push changes other than
> security fixes.
> 
> [0] https://trac.torproject.org/projects/tor/ticket/10314

I can't speak to whether more pluggable transports will be deprecated
in future, but I'll go out on a limb here and say "probably." The
nature of things ensures that the capabilities of censors continue to
advance. And as they do, new approaches will be found and deployed to
bypass those advancing attempts to block the network.

When bridges were first deployed, the fact that they weren't all
openly listed in a public directory made them more difficult to block.
Now, most plain bridges are very easy to block. When obfs2 was first
deployed, it was a solid protocol (I have no doubt). These days, China
is actively hunting down and blocking obfs2. There is very little
point to deploying either a plain bridge or an obfs2 pluggable
transport these days, especially on a mass scale.

On the plus side, obfs3 is still pretty strong, and it's one of the
common pluggable transports right now. Scramblesuit is not live in the
official bundles yet (AFAIK), but it just released and has some pretty
robust-looking defenses against active probing and other attacks. If
you're working on something new to deploy, these should be included,
without a doubt. They may indeed be deprecated in future, and in the
worst case may become unusable or make the bridge more susceptible to
being blocked. But if you go with a plain bridge or obfs2, you're
already in your worst-case scenario. You have nothing to lose and
everything to gain by enabling the newest pluggable transports.

I would highly recommend adding the Tor package repository to the
FreedomBoxes. As explained in [0], this won't always give you the
latest version of tor, but it will provide security fixes. My hunch is
that it will almost always also be a little fresher than Debian
stable. And given that network censors and network developers are
always going to be in an escalating arms race, enabling new releases
of Tor (and obfsproxy) directly from the project is going to make the
FreedomBox much more useful in the long term.

 -Lance

[0] https://www.torproject.org/docs/debian
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Re: [tor-relays] Relay configuration for FreedomBox

2014-03-22 Thread Lunar
James Valleroy:
> The reason that I'm asking is that FreedomBox is currently working
> within Debian "testing" but our target is Debian "stable". Once our
> packaged configuration is frozen for the next stable release, it will
> be more difficult for us to push changes other than security fixes.

(Debian hat on:) I try to keep Debian backports as up-to-date as possible.
Are official backports out of your set of allowed packages as well?

-- 
Lunar 


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Re: [tor-relays] Relay configuration for FreedomBox

2014-03-22 Thread James Valleroy
On Wed, Mar 19, 2014 at 9:25 AM, Lance Hathaway  wrote:
> If you're going to be running these as bridges, it seems to make sense
> to include obfsproxy support, probably with obfs3 and scramblesuit [0]
> enabled right off the bat.

Thanks for the information. Is it likely that obfs3 and scramblesuit
will be usable in the long-term? Or will they need to be deprecated at
some point like obfs2?

Also, if obfs3 or scramblesuit were deprecated, but some FreedomBoxes
continued to run those transports, what would be the result? Would the
worst case be that the bridge is no longer usable by some, as in [0]?

The reason that I'm asking is that FreedomBox is currently working
within Debian "testing" but our target is Debian "stable". Once our
packaged configuration is frozen for the next stable release, it will
be more difficult for us to push changes other than security fixes.

[0] https://trac.torproject.org/projects/tor/ticket/10314
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Re: [tor-relays] Relay configuration for FreedomBox

2014-03-19 Thread Lance Hathaway
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On 18/03/2014 7:59 PM, James Valleroy wrote:
> Do you see any vulnerabilities, attacks, or risks with the current 
> configuration, and are there any changes that you would recommend?
> 
> [1] https://wiki.debian.org/FreedomBox [2]
> https://www.torproject.org/docs/bridges#RunningABridge

If you're going to be running these as bridges, it seems to make sense
to include obfsproxy support, probably with obfs3 and scramblesuit [0]
enabled right off the bat.

Note that scramblesuit requires tor 0.2.5.1 or higher [1], and
obfsproxy should be at 0.2.7 or higher [3].

Lines to add to the torrc:
1. ServerTransportPlugin obfs3,scramblesuit exec /usr/bin/obfsproxy
managed ([0])
2. ServerTransportListenAddr obfs3 0.0.0.0: (if you want
to preset your obfs3 port, will be random otherwise) ([3])
3. ServerTransportListenAddr scramblesuit 0.0.0.0: (if
you want to preset your scramblesuit port, will be random otherwise) ([3])
4. ExtORPort auto (used internally between tor and obfsproxy, does not
need to be forwarded externally, so auto should be fine) ([4])

If I'm giving bad advice, somebody please speak up to correct me!

 -Lance


[0]
https://lists.torproject.org/pipermail/tor-relays/2014-February/003886.html
[1]
https://lists.torproject.org/pipermail/tor-relays/2014-February/003898.html
[2]
https://lists.torproject.org/pipermail/tor-relays/2014-March/004074.html
[3]
https://www.torproject.org/projects/obfsproxy-debian-instructions.html.en
[4]
https://lists.torproject.org/pipermail/tor-relays/2014-February/003962.html
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[tor-relays] Relay configuration for FreedomBox

2014-03-18 Thread James Valleroy
Hello,

The FreedomBox project [1] is planning to include Tor in the upcoming
0.2 release. FreedomBox is intended to be used as an always-on server,
so its Tor node has been configured as a bridge relay.

There is also a need for FreedomBoxes to be able to find each other
regardless of location or restrictive firewall. This feature is not
yet completely implemented for FreedomBox, but it will likely involve
each box running a Tor hidden service, and making the initial
connection to other boxes over the Tor network.

Here is the configuration that we are currently using in /etc/tor/torrc:

ORPort 4431
BridgeRelay 1
Exitpolicy reject *:*

It is based on example configuration for bridge relays given in the
Tor documentation [2] but modified to still allow SOCKS connections.

Do you see any vulnerabilities, attacks, or risks with the current
configuration, and are there any changes that you would recommend?

[1] https://wiki.debian.org/FreedomBox
[2] https://www.torproject.org/docs/bridges#RunningABridge

Thanks
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