tor-dev February 2011

tor-dev@lists.torproject.org

11 participants
8 discussions

Re: [tor-dev] xxx-triangleboy-transport.txt (+comments on pluggable-transport)
by Mike Perry 03 Mar '11

03 Mar '11

Thus spake Nick Mathewson (nickm(a)freehaven.net): > On Tue, Feb 1, 2011 at 12:08 AM, Mike Perry <mikeperry(a)fscked.org> wrote: > [...] > > > > Appendix: List of key xxx-pluggable-transport.txt shortcomings > > > > 1. This pluggable transport does not need any intelligence or process > > launching on the Client side, aside from a way to tell Tor not to be > > so pedantic about ensuring identity key and IP address consistency. > > What pedanticism exactly do you mean? Matching the IP addr in the > netinfo cell, or something else? I actually don't know the full list there. I think the last time we tried to enumerate this, we decided that "try it and see what actually breaks" was a more efficient approach. > > 2. The relay side needs to be able to detect if it has both the > > permissions and the network ability to send spoofed packets. It needs > > to communicate this fact with the Relay Plugin by responding with the > > appropriate extrainfo lines, or with "METHODS: NONE" to indicate > > error. This relay-side handshake should be specified in the > > pluggable-transport spec. > > To be clear, you mean that the plugin checks whether it can spoof (and > tell Tor "I do nothing!" if it can't), or that Tor needs to find out > whether it can spoof and tell the plugin that whether it can spoof or > not. The first sounds reasonable. The second doesn't so much: most > Tors won't want to try to spoof, so building the checks into Tor > wouldn't make sense to me, unless I'm missing something. Yes, the first is what we want here. > > 3. The relay plugin side needs some way to communicate EXTRAINFO lines > > to be added to its extrainfo descriptor. In this proposal, we use the > > SMETHOD reply to do this. > > Needs spec, not just an example. Ok. Well, does the example I gave look like an instance of what we want to specify as the behavior? > > 4. Is extrainfo really the best place to keep this information? > > Shouldn't it just be in the relay/bridge descriptor? Putting it in > > extrainfo requires our TransportBridges to enable the wasteful > > DownloadExtraInfo=1 torrc setting, which will consume more scarce > > resources and RAM on what will probably be cheap routers with 32-64M > > of RAM. > > Hm. Relay/bridge descriptor should be okay, I guess. I'm not sure > why the TransportBridges are getting those anyway, though: I see why > the client needs it, but not what the transportbridge needs it. The transport bridge should avoid being an open proxy. I suppose it can only properly carry full TCP streams to an endpoint, but without restricting who those endpoints are, it becomes a reflector open to abuse such as portscans. > Also, why are transportbridges even running tor? They don't seem to > be doing anything particularly tor-like. Mostly for the consensus, for reasons above. Not strictly required, if we don't mind being an arbitrary SYN proxy. > > 5. How would we go about chaining an actual obfuscation mechanism with > > this transport? Would we just create new and separate transport called > > TriangleBoyOverHTTP, for example, or is there a better way to chain > > different mechanisms? > > On the client side, socks-over-socks-over-socks is not actually a > terrible way of doing things there. We'll need to distinguish between > which transports are chainable and which aren't, though[*], and maybe > revise the design to make sure there's a way to tell to tell tor to do > said chaining. > > On the server side, you need some way to distinguish which processing > method to do for incoming data. Separate ports seems ok there. We > still need to figure out the server side. > > [*] generally, obfuscation is chainable but transport isn't. This is not a bad generalization. Do we want to make this distinction (between obfuscation vs transport) elsewhere in the spec, I wonder? -- Mike Perry Mad Computer Scientist fscked.org evil labs

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SSL Observatory Observations
by Tim Wilde 25 Feb '11

25 Feb '11

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 G'morning all! Last weekend's hackfest inspired me to attempt to run some numbers on the EFF SSL Observatory data[1], in particular looking at two things: the commonality of the "Internet Widgits Pty" organization string (a default in OpenSSL's CSR generator) in self-signed certificate subjects, and, further to that, the most commonly seen self-signed certificates in the data. Using the CSV data from the observatory, I found that out of 5,618,558 total certs in the all-certs file, only 8,891 contained subjects that matched the regex /Internet Widg[ie]ts Pty/ (a quick search observed both spellings; my OpenSSL used Widgits, FWIW. I further recorded the subjects of all certs where subject == issuer, and counted each, with the following results for the top 10: ' C=--, ST=SomeState, L=SomeCity, O=SomeOrganization, OU=SomeOrganizationalUnit, CN=localhost.localdomain/emailAddress=root(a)localhost.localdomain': 154867 ' C=US, ST=California, L=Sunnyvale, O=HTTPS Management Certificate for SonicWALL (self-signed), OU=HTTPS Management Certificate for SonicWALL (self-signed), CN=192.168.168.168': 111453 ' C=US, ST=Virginia, L=Herndon, O=Parallels, OU=Plesk, CN=plesk/emailAddress=info(a)plesk.com': 82689 ' CN=Fortinet, O=Fortinet Ltd.': 54975 ' C=US, ST=Virginia, L=Herndon, O=SWsoft, Inc., OU=Plesk, CN=plesk/emailAddress=info(a)plesk.com': 53184 ' C=USA, ST=California, L=Sunnyvale, O=HTTPS Management Certificate for SonicWALL (self-signed), OU=HTTPS Management Certificate for SonicWALL (self-signed), CN=192.168.168.168': 22987 ' CN=SpeedTouch 605, O=THOMSON, OU=DSL Internet Gateway Device': 16790 ' C=US, ST=Someprovince, L=Sometown, O=none, OU=none, CN=localhost/emailAddress=webaster@localhost': 16638 ' CN=SpeedTouch 5x6, O=THOMSON, OU=DSL Internet Gateway Device': 15286 ' C=US, ST=CA, L=Sunnyvale, O=SonicWALL, Inc., OU=SSL-VPN, CN=192.168.200.1': 11760 (Apologies for the lousy wrapping; initial spaces are present in the source data.) The numbers after the colons are, as you may guess, the total number of self-signed certificates with that subject. It may be instructive to dig into the netblocks where these subjects occur and attempt to determine the context in which they occur. For the purposes of making Tor appear unblockable due to collateral damage, my strong suspicion is that these will not be all that helpful, as they are quite likely (and in some cases, clearly) used by CPE devices and the like for internal management, and thus won't really be likely to cause much difficulty for the censors if blocked. My personal thinking is that the methodology in Jake's TLS normalization proposal[2] makes a lot of sense. Perhaps one modification, per the discussion at the hackfest, would be to stick to making the server's presented certificates self-signed, as that is probably more normal than having random unknown issuers, and less provably false than faking a known issuer like GoDaddy. Even ignoring the question of whether or not a censor may be willing to sustain the collateral damage of blocking one of the common self-signed subjects above, by using a commonName that varies per bridge/relay and other certificate fields that also vary widely (and in fact may be randomized to some extent), we don't present any blockable static values in our certificate subject or issuer and can focus on other fun stuff in the certs. :) Hopefully Jake hasn't already made this all a moot point while I was in the other room working with Andrew on Saturday and I just haven't heard about it yet. :) Further thoughts/discussions/flames welcome (but only if the flames come from Mike). Regards, Tim [1] https://www.eff.org/observatory [2] https://gitweb.torproject.org/tor.git/blob/HEAD:/doc/spec/proposals/ideas/x… - -- Tim Wilde, Senior Software Engineer, Team Cymru, Inc. twilde(a)cymru.com | +1-630-230-5433 | http://www.team-cymru.org/ -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAk1idPgACgkQluRbRini9tgmZACfSBNRhJ+ozVgIyDIdA4nWbOpI 25oAnRbbXvMkA+ttGkStfB2VFkcal1jd =vU04 -----END PGP SIGNATURE-----

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Re: [tor-dev] Publishing sanitized bridge pool assignments
by Karsten Loesing 25 Feb '11

25 Feb '11

On Thu, Feb 10, 2011 at 12:00:40PM +0100, Karsten Loesing wrote: > So, I implemented the new sanitizing algorithm that replaces bridge IPs > with 10.x.x.x addresses derived from the original bridge IPs. I also > sanitized the descriptors from November 2008 and performed an early > analysis on the results. > > The last remaining step is to sanitize our archives of bridge descriptors > once again and make the sanitized data available. I don't expect to have > new tarballs before next Tuesday. The new tarballs are available here: https://metrics.torproject.org/data.html#bridgedesc > Before publishing the new tarballs, I'd like to invite people to review > the new sanitizing process: > > - A specification-like description of the sanitizing process is in > Section 3 of https://metrics.torproject.org/papers/data-2011-02-10.pdf > > - The early analysis results of bridges changing their IP addresses are > here: https://trac.torproject.org/projects/tor/ticket/2435#comment:3 > > - The tarball with sanitized bridge descriptors from November 2008 is > here (6.2M): > http://freehaven.net/~karsten/volatile/bridge-descriptors-hashed-ips-2008-1… > > Any questions, comments, and concerns are highly appreciated! Feedback still much appreciated! Best, Karsten

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Proposal idea: Require majority of authorities to vote for consensus parameters
by Sebastian Hahn 22 Feb '11

22 Feb '11

Filename: xxx-param-voting.txt Title: Require majority of authorities to vote for consensus parameters Author: Sebastian Hahn Created: 16-Feb-2011 Status: Draft Overview: The consensus that the directory authorities create may contain one or more parameters (32-bit signed integers) that influence the behavior of Tor nodes (see proposal 167, "Vote on network parameters in consensus" for more details). Currently (as of consensus method 11), a consensus will end up containing a parameter if at least one directory authority votes for that paramater. The value of the parameter will be the low-median of all the votes for this parameter. This proposal aims at changing this voting process to be more secure against tampering by a non-majority of directory authorities. Motivation: To prevent a minority of the directory authorities from influencing the value of a parameter unduly, the majority of directory authorities has to vote for that parameter. This is not currently happening, and it was in fact not uncommon for a single authority to govern the value of a consensus parameter. Design: When the consensus is generated, the directory authorities ensure that a param is only included in the list of params if at least half of the total number of authorities votes for that param. The value chosen is the low-median of all the votes. We don't mandate that the authorities have to vote on exactly the same value for it to be included because some consensus parameters could be the result of active measurements that individual authorities make. Security implications: This change is aimed at improving the security of Tor nodes against attacks carried out by a minority of directory authorities. It is possible that a consensus parameter that would be helpful to the network is not included because not enough directory authorities voted for it, but since clients are required to have sane defaults in case the parameter is absent this does not carry a security risk. Specification: dir-spec section 3.4 currently says: Entries are given on the "params" line for every keyword on which any authority voted. The values given are the low-median of all votes on that keyword. It is proposed that the above is changed to: Entries are given on the "params" line for every keyword on which a majority of authorities (total authorities, not just those participating this vote) voted on. The values given are the low-median of all votes on that keyword. XXX note previous behaviour. The following should be added to the bottom of section 3.4.: * If consensus method 12 or later is used, only consensus parameters that more than half of the total number of authorities voted for are included in the consensus. The following line should be added to the bottom of section 3.4.1.: "12" -- Params are only included if a majority voted for them Compatibility: A sufficient number of directory authorities must upgrade to the new consensus method used to calculate the params in the way this proposal calls for, otherwise the old mechanism is used. Nodes that do not act as directory authorities do not need to be upgraded and should experience no change in behaviour. Implementation: An example implementation of this feature can be found in https://gitweb.torproject.org/sebastian/tor.git, branch safer_params.

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Re: [tor-dev] xxx-draft-spec-for-TLS-normalization.txt
by Nick Mathewson 21 Feb '11

21 Feb '11

Aha. Let's see if I have the tor-dev address right at long long last. Apologies to Peter, who will have received more than one copy of this already. (Apparently , I am told, the "lists." in tor-dev(a)lists.torproject.org is not optional.) On Mon, Feb 21, 2011 at 12:52 PM, Nick Mathewson <nickm(a)freehaven.net> wrote: > On Sun, Feb 20, 2011 at 10:49 PM, Peter Gutmann > <pgut001(a)cs.auckland.ac.nz> wrote: >> Nick Mathewson <nickm(a)freehaven.net> writes: >> >>>Preliminary results suggest that there wasn't actually a crowd here: the >>>reason that we switched the browser DH paramaters in the most recent releases >>>is that the old (standard!) primes were in fact blocked by at least one >>>nation-level censor because we used them. It seems that in practice, if we >>>want to blend with a crowd, we need to use the hardwired DH parameters from >>>mod_ssl. >> >> So the SSL handshake was blocked if you used the Oakley (RFC 2412) DH values? > > Just the 1024-bit one, I would guess (the one in section E.2 of > RFC2412, a.k.a. the one from RFC2409 section 6.2, a.k.a Second Oakley > Group). Or to be precise, we used to use that group, and then we were > blocked, and when we changed to a different group, we weren't. It > might be that they were blocking based on more than one factor, only > one of which was the use of the prime in a TLS ephemeral DH handshake. > >> Is there a server in said location for which access gets blocked that I could >> test against? I'd love to try some variations on SSL handshakes to see what >> gets blocked and what doesn't. > > The use in question was a client in the country trying to connect to a > server outside the country, and the server providing this DH parameter > value. I'll ask our contacts if they can get you shell access there.

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Fw: curvecpclient+curvecpserver alpha test
by Robert Ransom 21 Feb '11

21 Feb '11

See below. Robert Ransom Begin forwarded message: Date: 21 Feb 2011 02:51:21 -0000 From: "D. J. Bernstein" <djb(a)cr.yp.to> To: curvecp(a)list.cr.yp.to Subject: curvecpclient+curvecpserver alpha test Hi everybody, I've posted information about CurveCP at http://curvecp.org; and today's release of NaCl includes command-line curvecpclient and curvecpserver tools. There are many reasons that this curvecpclient+curvecpserver software isn't ready for users yet---among other things, * the software hasn't gone through anywhere near my usual levels of testing and security review; * the software prioritizes simplicity over efficiency in several ways, missing some of the speed that CurveCP can provide; and * the software handles only CurveCP, without HTTPCurve, SMTPCurve, etc. ---but if you're a programmer interested in CurveCP then I think this software is a reasonable starting point for experimentation and further development. ---D. J. Bernstein Research Professor, Computer Science, University of Illinois at Chicago

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Re: [tor-dev] Thoughts on https://trac.torproject.org/projects/tor/wiki/dev/SupportPolicy
by Lucky Green 21 Feb '11

21 Feb '11

On 2011-02-02 09:02, Nick Mathewson wrote: > > On Tue, Jan 25, 2011 at 9:04 AM, Lucky Green <shamrock(a)cypherpunks.to> wrote: >> >> On 2011-01-25 01:09, Erinn Clark wrote: [...] >> >> Erinn, >> >> My feedback is that the Tor Project really, really will want a written >> >> and published policy of how far back an OS is supposed to be supported. >> >> Otherwise, you will get to have this discussion every time a new OS >> >> version is released. >> >> >> >> Industry standard for consumer software that goes into the far corners >> >> of the world is "current and previous major version", which has >> >> different meanings depending on OS. > > > > Hi, Lucky! I generally agree with you, but I do want to point out a > > point that makes me balk at applying your experience without more > > consideration. > > > > It seems to me that the "industry standard for computer consumer > > software" is chosen to serve the goals of the software industry: that > > is, to sell software to people who can pay for it. As a means to that > > end, commercial software enterprises sometimes additionally support > > marginal userbases (those who can't pay, those who can't pay much) in > > order to increase the install base of their software and provide > > positive network effects for their paying customers. > > > > We're in a slightly different position: we're achieving our mission to > > the extent that lots of users -- whether they can pay or not! -- can > > use our software. Also, we want volunteers with free (to them) > > bandwidth to be able to run our server software on the hardware and > > software they have lying around. > > > > I suspect that, when all is said and done, the set of operating > > systems that it makes sense to support in the commercial software > > industry will work out to be almost the same as the ones Tor want to > > support -- but the reasoning is a little different, since industry > > needs to optimize profit-per-developer-hour, and we're trying to > > optimize social-benefit-per-developer-hour. Hmm. My emails on this topic must have been quite poorly written to result in your feedback about them focusing on what I had intended to be little more than a footnote or parenthetical at the very end of the communication thread. I am aware of and concur that Tor's success metrics are different from those of most commercial software vendors. My analysis was entirely focused on helping Tor devise the best OS version support policy possible while assuming Tor's goal of "social-benefit-per-developer-hour". My bad if that was not clear from my writings. Though I am not quite certain what the best path would have been for me to take: omit any references to commercial software development best practices, even in annexes and footnotes, when discussing open source software? Somehow that doesn't strike me as the optimal answer. But be that as it may, I assure you wholeheartedly that my analysis was solely intended to guide Tor and its ecosystem, not that of commercial software development. Either way, even more core to my advice than which particular OS versions to support (the one area where any dichotomy between open source and the commercial world may or may not come in) was my point that Tor needs a written and published OS support policy, agreed-upon by the Tor team. Whichever version support policy the Tor team may arrive at and for whatever reasons. And whether or not the Tor team takes my advice as to which particular versions to support. --Lucky

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Re: [tor-dev] or-dev mailing list migration February 19, 2011
by Andrew Lewman 20 Feb '11

20 Feb '11

And this is complete. Mail archive migration is coming soon. On Sun, 13 Feb 2011 21:37:20 -0500 Andrew Lewman <andrew(a)torproject.org> wrote: > A reminder that this migration occurs this weekend. > > On Mon, 24 Jan 2011 15:28:30 -0500 > Andrew Lewman <andrew(a)torproject.org> wrote: > > > Hello or-dev subscribers, > > > > On February 19, 2011, we are migrating or-dev from or-dev(a)seul.org > > to tor-dev(a)lists.torproject.org. We will migrate your e-mail > > address's subscription to the new list. You will receive a > > confirmation from the new mailing list software on the 19th. > > > > Current or-dev archives will be migrated. Roger plans to leave the > > current archives in place at seul.org as well. > > > > We're using this migration to spread administration out to Tor's > > sysadmin team rather than making Roger do everything himself. The > > secondary benefits of having the lists on the torproject.org domain > > include SSL-enabled login, archives, and easier account management. > > > > You can subscribe to the new list at > > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > > > > I will send out a reminder on the day of the migration. > > > > Please e-mail tor-assistants(a)torproject.org with any questions. > > > > Thank you. > > > > > -- Andrew pgp 0x74ED336B

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tor-dev February 2011