teor teor2345@gmail.com wrote:
On 6 Dec 2017, at 19:13, Scott Bennett bennett@sdf.org wrote:
null null@omuravpn.com wrote:
@ x9p:
[stuff deleted --SB]
relays. Since our relays are all in the same declared family, it is very difficult to see how this traffic is legitimate. If it's valid
But it could be legitimate. As has been discussed here previously,they may be connections from a relay that actually is in the consensus, but either a) uses an OutboundBindAddress or b) is on a LAN that has multiple connections to the Internet.
Relays try very hard to have at most one connection to each other relay.
Good. That tendency must have improved a lot over the years, then.
(And only two relays are allowed in the consensus per IPv4 address.)
Yes.
Clients try to make one connection to one or two guards.
Or however many are specified in torrc. Sometimes one needs, say, three to five guards for better capacity or lower latency or better reliability.
So it's far more likely to be a collection of Tor clients in a network with only a few public IPv4 addresses. (There are entire countries and large networks that only have a few allocated IPv4 addresses.)
An excellent point. Thank you.
Or, it might be a bug in Tor, a misconfiguration, or a denial of service attack. We'd like to know more, so we can find out and fix it.
If it's a LAN with many users and few external IPv4 addresses (or, perhaps, even IPv6 addresses if NATed to the outside via only a few), then there really is nothing to fix.
(Snip) A script similar to the one used to reveal and make available the otherwise unidentified source IP addresses of exits could be run by the project to gather the hidden addresses of currently running relays, and a list of such addresses could be made available on a compromise basis, e.g., by having a relay at the project that would serve those lists only over tunneled directory connections *from relays*, were it not for obstinacy. Such a list could then be included into our packet filters' "free pass" lists without putting the list up on the project's web site like the exit list is.
Outbound addresses aren't secret, because they are used for connections.
Roger has claimed here that some of them are indeed secret in the sense that their owners do *not* want them to be published, one possible reason for which being that they do not want their relays blocked successfully by governments, e.g., China, Iran. (How hiding the source address of a published relay would evade the Great Firewall escapes me somehow, except perhaps for hidden services based inside China that might be reached via those hidden source addresses. Given that most source addresses of relays *are* published, the chances of getting a circuit into China seem rather slim anyway.) I guess tor project members are not all in agreement over such matters.
Anyone is free to volunteer to create and maintain a list of outbound relay addresses. It is technically feasible: it requires a few thousand Tor connections per day, one via each relay, to a relay that reports the
Ideally, per hour, but that is why it should only be done by one site. Note that Exit relays might be skippable because their outbound addresses are already identified by one site, namely, the tor project, and published. IOW, only entry/middle and non-Exit exit nodes need be tested, which would shrink the list by several hundred to a thousand or so.
remote address of each inbound relay connection.
It just needs to be done safely, in a way that doesn't collect client addresses, and avoids attaching a timestamp or order to relay connections.
Why would client addresses ever be involved? What would be gathered are the addresses from which *relays* connect to other relays (N.B. *not* to destinations). The only timestamps that I see might be relevant would be the starting and ending times for each script run, so that an administrator's own script(s) for incorporating those addresses into his "free pass" list might easily discern out-of-date script output files from current script output files.
A torrc option to fetch the list whenever updates were available could default to not fetching the list, so relays whose operators who do not use packet filter defenses would not automatically fetch the hidden address list of non-exit relays.
If someone created a list, and showed that it had value to other relay operators, then it might gain support, and be supported by Tor, just like other features have:
There is an exit_addresses field for relays in Onionoo and Relay Search that gives the outbound exit addresses of every exit (when they differ from the relay address). It gathers addresses using exitmap. (Rather than relays self-reporting, which is unreliable.)
Right.
There is also a torrc option that has the side effect of making every address on the machine public, even unused addresses, because it blocks them in the exit policy. (ExitPolicyRejectLocalInterfaces, off by default.)
Here's how someone could work on this feature:
Create a scanner, publish a list, and show that it has value.
Because such a list would include addresses whose owners might not be pleased about those addresses being published (see above), such a list should *not* be published, but perhaps could be sent to someone in the tor project. Better still, the generating script could be sent to someone in the tor project to enable the project to run the script, rather than encouraging many relay operators all to duplicate the network load of running it.
Or start with a proposal, ask for advice, then create the scanner.
Try for something independent of Tor, like exitmap, because it will be more accurate. (Tor doesn't always know what its outbound address is.)
Like I wrote before, a script would do it, although an actual program could also do it. Execution speed is probably not relevant because the orders-of-magnitude larger delays will come from circuit construction times, which consist primarily of network delays and delays caused by other relays. After putting it off for many years, I'm now going through a small book on python. Aside from a couple of very annoying misfeatures I've run across so far, it looks to be a fairly straightforward language to learn to write. Then I'll need to study the tor project's stem library documentation before writing the script, which I doubt will need to be very complex. The output, after all, should only be a list of otherwise unpublished IP addresses from which connections from relays may arrive at any other relay. No other information need be included, other than possibly the aforementioned file generation timestamps (similar to consensus document timestamps, though perhaps less frequent).
And try to have list downloads rely on existing Tor features, like onion services. They'll be faster to deploy that way.
AFAIK, tor has no such feature. If a relay is to download nothing more than a file of IP addresses, which feature are you suggesting will do that upon demand by a relay (and only an identified relay)? Yes, a relay can ask for a directory download (and so can a client). Yes, a relay can ask for a directory update download (and so can a client). Yes, a relay can ask for ExtraInfo document downloads. How does a relay ask to download a kind of file that doesn't yet exist? Is there already some undocumented, generic feature that a identified relay (but nothing else) can ask a directory mirror or authority to "give me your latest version of file x"? If you mean that the downloading process could be spun off to a worker thread, then yes, of course, it should be, but the actual implementation in tor would be up to the tor developers, not to me.
Here's a description of the proposal process:
https://gitweb.torproject.org/torspec.git/tree/proposals/001-process.txt
Tor clients, they are behaving very strangely, and in either case we need to limit their impact. As such we've implemented connlimits by /24 as suggested (with a much higher limit to err on the side of not rejecting valid traffic). We can already see that this has improved our situation.
And it will likely get you roundly denounced by tor project membersand certain other individuals on this list. :-(
I sketched a proposal like this in another thread just a few days ago. I'm happy to work with others to include inbound or outbound connection limits in the draft proposal. (My initial proposal had outbound circuit and stream limits.)
You will also see your Fast and HSDir flags come and go at random, depending upon how many authorities creating testing circuits to reach and test your node(s) go through a node that used a hidden outbound address as the source address that fails your filter to connect to your node.
If you set the connection limit at or above 512 connections per /24, it will be impossible for well-behaved consensus relays to go above the limit:
2 relays per IPv4 * 256 IPv4 addresses per /24 = 512 connections
Apparently, the aforementioned effort to limit each relay pair to a single connection does not apply to hidden service connections, as can be readily seen on a Fast HSDir relay when bursts of connections occur. There is also little to prevent many thousands of clients from connecting simultaneously. A number of high-capacity relay operators have mentioned here in the past that they have had to increase their OS's fd limit to a value far greater than its default in order to prevent relay death under the heavy connection loads typical of such relays. My relay is a relatively low-capacity relay, yet when it has the Fast flag, and especially with an additional HSDir flag, it often has several thousand connections at any given time.
Or you could check how many relays are in the most popular /24, and use that to work out a limit.
(Snip)
@ Scott Bennett:
(Snip)
Nonetheless, we're not opposed to disabling HidServDirectoryV2 to rule it out. However it appears that option is deprecated (on 0.3.1.9). Enabling it causes this in the log:
[WARN] Skipping obsolete configuration option 'HidServDirectoryV2'
It's also no longer listed in the Tor manual (https://www.torproject.org/docs/tor-manual.html.en). It looks like we might be able to achieve the same effect with something like this
Sigh. My apologies. You are indeed correct on this matter. It hadslipped my mind that tor no longer is distributed with a man page.
Tor source is distributed with an asciidoc man page.
But not a UNIX/LINUX man page, either as *roff source or plain, ASCII text. If it doesn't have a file that works with the man command, then it does not have a man page, by definition.
It might not be on your system because the packager left it out, or left out asciidoc as a build dependency.
Thanks for the info. I'll try to check into that. asciidoc is in the build dependency list if either the DOCUMENTATION or the MANPAGES configuration option for the port is selected. The MANPAGES option is on by default in the port's Makefile, yet no man page gets installed as nearly as I can see.
Scott Bennett, Comm. ASMELG, CFIAG ********************************************************************** * Internet: bennett at sdf.org *xor* bennett at freeshell.org * *--------------------------------------------------------------------* * "A well regulated and disciplined militia, is at all times a good * * objection to the introduction of that bane of all free governments * * -- a standing army." * * -- Gov. John Hancock, New York Journal, 28 January 1790 * **********************************************************************