[tor-talk] Newbie with a bunch of questions for Tor Cloud

Runa A. Sandvik runa.sandvik at gmail.com
Sun Mar 23 01:21:38 UTC 2014

On Thu, Mar 20, 2014 at 3:32 AM, Soul Plane <soulplane11 at gmail.com> wrote:
> On Wed, Mar 19, 2014 at 6:01 PM, Runa A. Sandvik <runa.sandvik at gmail.com>wrote:
>> On Wed, Mar 19, 2014 at 9:05 PM, Soul Plane <soulplane11 at gmail.com> wrote:
>> > More questions:
>> >
>> > Why is the only region available for the Tor images us-east virginia? I
>> > thought I could use the free tier in other places. Wouldn't it be better
>> to
>> > vary the regions instead of sticking them all in one place?
>> We initially had images in all regions, but due to a bug/issue (see
>> https://trac.torproject.org/projects/tor/ticket/10318) I decided to
>> temporarily remove all images except the ones in us-east-1. The goal
>> is to bring back images for the other regions at some point.
> Thanks, I read the bug and the AWS thread and it looks like there is
> something wrong with the image copy process. If I wanted to setup in a
> location other than Virginia would I be able to use your build script to do
> that or would I run into the same image copy problem?

The copy problem may have been fixed, but I have yet to try it out
myself. If you want to set up a bridge in a location other than
Virginia, spin up an Ubuntu instance and go through the steps in

> Also I noticed in
> ec2-prep.sh you have:
> curl -m 5
> That address is invalid, what is the reservation id for?

>> > I read in Tor Weekly News today that the obfs3 protocol is vulnerable to
>> > active probing attacks and there is a replacement ScrambleSuit. If I
>> setup
>> > the AWS Obfsproxy image now does that mean the Chinese can detect it and
>> > block it? Is that image obfs2 or 3 or both? Should I just wait until
>> > ScrambleSuit is supported, or can I modify the config file to only use
>> > ScrambleSuit, or is that not a good idea at this point? I don't want to
>> run
>> > something that nobody is going to be able to use because governments can
>> > just detect it and block it.
>> The current image is a "standard" bridge, an obfs2 bridge, and an
>> obfs3 bridge. ScrambleSuit is not included. If you create an SSH key
>> when setting up the instance, you can log on and change whatever you
>> want. The Great Firewall of China blocks "standard" bridges and obfs2,
>> but I believe it has yet to block obfs3.
> Ok so after I do a build if I want scramblesuit I change this line:
> ServerTransportPlugin obfs2,obfs3 exec /usr/bin/obfsproxy --managed
> to this:
> ServerTransportPlugin scramblesuit exec /usr/bin/obfsproxy --managed

If you want your bridge to just support the scramblesuit transport, yes.

> According to this here I need to update obfsproxy first? Is that relevant
> here?
> https://lists.torproject.org/pipermail/tor-relays/2014-February/003886.html

Yes. The ec2-prep.sh script will only pull packages from the Ubuntu repository.

>> > Is Tor obfuscation specifically more likely to come under attack from
>> > repressive governments?
>> More likely than what?
> Than regular tor bridges. Are obfs3 bridges special bridges that users in
> repressive countries are more likely to use because other bridges are
> blocked? Maybe I don't understand.


>> > How is security handled. For example suppose there's a known
>> vulnerability
>> > in Tor or Ubuntu does the server shut down until it's fixed and an update
>> > is available or does the server stay up and risk being hacked? Is there
>> any
>> > notification sent to the AWS administrator in these cases? I would
>> imagine
>> > even a small window is gold for some state run group to break in.
>> The server stays up and checks for regular package updates from
>> Ubuntu. If someone were to break in, they would not learn anything
>> more than if they had set up a bridge themselves.
> Ok. Let's say there was a security vulnerability being exploited in Tor
> bridges. Is there any warning from Tor staff? Like when there is one in
> Flash or Microsoft etc I will get a CERT or a security advisory saying "xxx
> is being actively exploited", view such and such a page for more
> information. In those cases I will just turn off flash or run the fix it.

There will be emails on the tor-talk mailing list and posts on the blog.

>> > How can I determine the integrity of the server and do I have any
>> > responsibility to do that? Do you guys who are running these instances in
>> > the Tor Cloud just set it and forget it or is there some oversight
>> required?
>> The Ubuntu image the Tor Cloud image is based off of is verified when
>> the image is built. The Tor package is verified as it is installed
>> (which happens within the first five minutes you boot the server for
>> the very first time).
> Thanks I took a look at the script.
>> > I would take an active role in securing the instance if necessary but I
>> > need to know what to do. What do you guys do?
>> The image has been configured to automatically check for package
>> updates. In addition, it is recommended that you only open certain
>> ports in the firewall (22 for SSH, plus 443, 40872 and 52176 for Tor).
> Is there any obfuscation benefit to using random ports, like changing
> 40872  to 1234 etc.

Some, yes, you can change the ports if you want.

Runa A. Sandvik

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