April 2013 - tor-dev - lists.torproject.org

New flash proxy facilitator domain fp-facilitator.org
by David Fifield 30 Jun '13

30 Jun '13

I moved the flash proxy facilitator to a new domain, fp-facilitator.org. This is to get it away from bamsoftware.com, which also has a lot of unrelated stuff. The old facilitator name tor-facilitator.bamsoftware.com will continue to work (the DNS for both points to the same place). https://trac.torproject.org/projects/tor/ticket/7160 is the ticket. David Fifield

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Vidalia 2.0 - an complete rewrite
by Leo Unglaub 28 Jun '13

28 Jun '13

Hey friends, i want to inform you that i am working on a complete new control tool for Tor. I know some people use Vidalia for it, but i never liked the program and the people i showed vidalia often got confused. So i started to rewrite it from scratch and i am close to the release of the source code. (Currently i need to clean up some classes in there) I had a few things on my feature list for the new control tool and i want to share/discuss it with you. Because maybe some of my ideas are bad or maybe you have some additional ideas for features. A: "native work flow". Thats one of the main goals of my rewrite. The current Vidalia does things a little bit different than people are used to do it. So they get confused, because it does not behave "naturally". So instead of QT i used GTK and followed as always the GNOME HIG. (http://developer.gnome.org/hig-book/3.5/) B: "Multi configuration setup". What do i mean by that? Well, in my case for example i use Tor on my laptop and i am often in different places where i need different settings for tor. For example, if i am at home i can give tor all the bandwith i have, because at home i don't care. In my company on the other hand i cant do that. I am allowed to run Tor in the company, but with a bandwith limit of 2000kbit/s. (Yes, my company allows this ... well, i am the technical directory, so it was my call :) ) But i need a different Tor configuration there. Or if i am giving a talk and only have mobile internet connections i need every bit of bandwith for checking my emails so i want no server, only Tor client support. Currently i have multiple torrc files for that and always move them arround. That works for command line junkies like me, but even i am anoyed to do this multiple times a day. So i added the "multi configuration" support into the tool. This allows you to define multiple configurations and simply change them with a click from the gnome2 notification panel. C: "GUI for config settings". Well, some users are simply not ready to modify config files on there own. So i provide a simple gui (tab based) for all config options i found in the normal torrc file. Always with an explonation (with needs spellchecking, because my spelling sucks in german and is even worse in english :) ) so the user can deside what an option would to. D: "Notifications": My control tool uses the normal desktop notifications to inform the user about changes in the running tor application. For example if there is a problem building the circuit or something you get the notifyd message and can simply react to events without having the arm log open all the time. Thats just a quick overview of what i am duing right now. The source code will be released soon and is of course 100% open source. If you have some addiional ideas, feedback, wishes, ... i would like to hear them. Thanks and greetings Leo PS: I am Germam and very sorry for every spelling error i did above. -- Leo Unglaub Nachreihengasse 39 / Top 7 A-1170 Vienna Austria Phone: 0650 / 6575103 Website: http://www.leo-unglaub.net Twitter: http://twitter.com/LeoUnglaub Send with Mozilla Thunderbird on Linux (Debian)

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[Stegotorus] Fundamental problem with ack/retransmission mechanism
by vmonmoonshine＠gmail.com 24 Jun '13

24 Jun '13

Hello Zack, In testing the retransmission algorithm, I encounter situations that the ack/retransmission algorithm is unable to resolve by design. It happens when the header of a packet gets deliver but the middle part gets dropped. For example in the following scenario Server sends packet 1 len 4k packet 1 gets lost Server sends packet 2 len 64k the last 60kb of packet 2 gets lost client receives packet 2 partially (4k) and waits for the 60k to come. client sends ack to the server saying that packet one is lost server retransmits pack 1 client consider packet 1 as a part of packet 2, and thinks that now it has 8k of packet 2 client again sends ack to the server saying that packet one is lost server retransmits pack 1 client thinks now it has 12K of packet 2 client again sends ack to the server saying that packet one is lost server retransmits pack 1 client thinks now it has 16k of packet 2 etc Soon the transmit queue on the client side will get filled up by the ack packets, cause the client won't realize its mistake before it receives 64k of garbage and be able to compute the mac. Hence the server and the clients will remain in this deadlock for ever. Originally, Stegotorus was dropping any circuit with full transmit queue. But this was causing lots of problem because lots of time the client lags behind the server for a while to process all the packet and sends ack. If ack/retransmit by design wasn't meant to recover from partial packet lost and was only a defense for complete packet lost, then the dropper proxy isn't doing a good job simulating the intended threat model. Otherwise, if the ack/retransmit was meant to withstand partial packet drop, then we need to redesign it so it doesn't get trapped in such a deadlock. Maybe we should have a timer so the circuits with full transmit queue gets a grace period before getting dropped. This is not specific to chop protocol. I'm wondering how TCP is dealing with such a situation. Thanks, Vmon

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GSoC 2013 project idea
by Sreenatha Bhatlapenumarthi 03 May '13

03 May '13

Hi, My name is Sreenatha Bhatlapenumarthi (lucyd). I am a third year computer science undergraduate at IIITH. I am interested in participating in GSoC'13 with Tor. I've begun by submitting patches for stem tickets #7505, #8605 and #7713. I'd like to propose a new idea for a project with a blend of stem, TorBEL and pyobfsproxy. I've split the project into 3 modules. 1. Fix stem bugs and add new features if possible Although I can't think of any new functionality to add to stem(other than what Damian suggested) at this point of time, there are some bugs that need to be fixed. I went through the tracker and picked some stem-related bugs I'd like to fix as a part of the project. Please feel free to suggest new bugs or let me know if you think any these are of low priority and don't need to be included in the project. - #7910 (Port some of arm's connection utilities to stem) - #8255 - #8248 - #8249 2. Migrate TorBEL to Stem [0] This will involve porting TorBEL from TorCtl to Stem and making modifications to the stem API if necessary. Hopefully after fixing the bugs mentioned above, I'd have a better understanding of how stem works and I'd be able to do a better job. 3. Implement HTTP pluggable transport for pyobfsproxy I can think of two ways of doing this - Develop an actual pluggable transport for obfsproxy to impersonate HTTP traffic. I've looked at obfs2's protocol-spec and its python implementation and I think this would involve writing a separate module implementing the transport with a template similar to that of DummyTransport[1]. - Use a browser engine like webkit on client-side and a web server on the server-side as mentioned at ticket #8676[2]. Here are a couple of questions I have regarding the project: - What are the priorities of the modules I've proposed? - Do you think the project has enough scope and material for a SoC project? If not, can you please suggest some more features to add? - If the project seems overloaded, which module(s) do you suggest I drop? I would love to hear your opinions on these matters. If there's something you want me to take a look at or study, please do let me know. Thank you for your time. [0] - https://trac.torproject.org/projects/tor/ticket/8263 [1] - https://github.com/lucyd/obfsproxy/blob/master/obfsproxy/transports/dummy.py [2] - https://trac.torproject.org/projects/tor/ticket/8676 Cheers, Sreenatha

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Cell digest of relay cells destined for hidden services
by Frank Young 02 May '13

02 May '13

The digest of relay cells are running digests [ SHA_final() is never called ], so the digest of each cell is dependent on the previously computed digest destined for that node particular node. Hashing is seeded with values determine by the OR which responded with CREATED or REALY EXTENDED cell. I have noticed that, the payload of RELAY_COMMAND_RENDEZVOUS unlike CREATED OR RELAY EXTENDED cells made no provisions for the seeding bytes. This can be referenced in section 1.10 of https://gitweb.torproject.org/torspec.git?a=blob_plain;hb=HEAD;f=rend-spec.… I'm in a state of confusion concerning how the digest of relay cells destined for hidden services should be computed. [1] should the digests be independent of previously computed digests destined for the hidden services? OR [2] it should be a running digest but not seeded with any seeding value. I will like a little clarification on this. Thanks

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Re: [tor-dev] Stem Integ tests for Tor
by Ashish Patil 01 May '13

01 May '13

On Mon, Apr 29, 2013 at 17:44 PM, Nick Mathewson <nickm at alum.mit.edu> wrote: > Right now, all chutney > does is configure and launch a small Tor network, but the small > network requires a little babysitting to make it bootstrap. (For > example, you sometimes need to send the clients a SIGHUP once the > authorities have made their first consensus. So, the first bits for improving chutney would be to automate the network generation as much as possible (leaving no loose ends)? > What Chutney doesn't do (but should!) is actually test the network it > launches. Right now, to make sure the network has bootstrapped, you > have to read through its log files. If you want to test the network > with any traffic, you need to use an application of your choice to > send traffic through one of the Tor clients, and verify that the > output as is expected. And if you want to make sure that Tor is > running without weird warnings, you need to manually inspect the > log files again. It would be good if Chutney grew into, or were > replaced by, a tool that could actually do testing right that. Now, we want chutney to be robust enough to encompass all the manual that is mentioned above & automate it as much as possible or atleast print the tasks to be performed by the tester sequentially. We would need a set of static reliable web pages if we want to automate the traffic testing? Also, we would parse the log files for errors or warnings so that we dont have to manually check for them. * Construct a circuit to an exit which allows port 80 and request a site through it. * Do the same for an exit which rejects port 80. * Construct a one-hop circuit through an exit. * Try to use a circuit that runs through a bridge. * Let tor pick the path of a circuit and assert that the first relay's a guard and the last is an exit. * Attempt to request a page from a hidden service. * Host a hidden service and request something from ourselves. * Act as a relay and try to construct a circuit that includes ourselves. * ... etc... As Damian listed down all the tests one needs to carry out for actual network testing (keeping in mind unreliability of the network at times), what all additional tests would we like chutney to have?

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GSOC - Internet Censorship Virtual Machine Based Simulator
by Claudiu Perta 01 May '13

01 May '13

* Hi Tor team, I'm Claudiu, a second year PhD student in CS at Sapienza University (Rome, Italy) and I would like to work on your GSOC idea to build a VB-based simulator for OONI. My main research topics are network neutrality and broadband measurement and I'm currently working on a project on traffic shaping detection. I also partecipated to last year GSOC when I developed in Python a server selection mechanism for M-Lab ( https://code.google.com/p/m-lab/source/browse/?repo=ns) I've worked in the past with Netkit ( http://wiki.netkit.org/index.php/Main_Page<http://wiki.netkit.org/index.php/Main_Page>) and I think it meets all the requirements of this GSOC project. Netkit is an open source project,based on user-mode linux[1], a linux kernel that can be executed as a user process on a standard linux box. In particular, each virtual machine in Netkit can be configured to play the role of a regular host, of a router, or even of a switch. For this project, each test could be set up as a ‘netkit lab’, which is a set of preconfigured virtual machines that can be started and halted together. For example, one virtual machine running ooniprobe could be connected to the external world through a second virtual machine that implements various censorship policies, specific to each test. Regards, Claudiu [1] http://user-mode-linux.sourceforge.net/ *

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New Google Summer of Code idea
by Milosz Godlewski 30 Apr '13

30 Apr '13

Greetings everyone, I want to share with you my idea to increase security. I would like to create a add-on to the Tor Browser Bundle application, which will ensure protection and control of out- and in- connections. That add-on will enable setting a maximum time of data transfer between the user and the web, thus we can radically improve the privacy of user in web. For this purpose we are going to add one of open source firewall to the Tor Browser Bundle application. This extension will inform the user about request of connection and then, dependently on the user’s choice will block (or not) whole in- and out- traffic, in order to allocate time of execute into every web site (every server) in a bookmark, Firefox or Flash animation. After the report of connection request trough any web application, it would be possible to add the maximal time, gave to the application for data transfer. It gives the possibility to block the unlike sending and downloading information in the background, for example after receiving whole content of the site. Example: block the chat in Facebook or block the execution of application, working in the background (bootnet type) It could be also possible to set a temporary time of blocking OR unblocking applications ( in future maybe also external). This application can start working on the console, but it’s worth to add pop out information after some time. In the other window it will be possible to show a list of active applications (which actively downloading data) in order to unfold and “take a look” which card is downloading files from server. In other words we would like to block all applications’ access to the internet without the users knowledge, when Tor works. Hope you will like it :) Miłosz Godlewski

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Improving the HTTP interface of BridgeDB: bridges.torproject.org
by George Kadianakis 30 Apr '13

30 Apr '13

Hi list, it's high time to write a better website for https://bridges.torproject.org since it currently looks like the homepage of an academic professor. The new website should promote the use of pluggable transports (over normal bridges) and should be explanatory and friendly to end-users. I started writing a skeleton and some strings for the new website. I'm also attaching an image of how the website looked like in my head while I was writing the strings (although the person who codes, should choose the interface). Sathya (cc'ed) said that he would be interested in coding the web part. The relevant trac ticket is https://trac.torproject.org/projects/tor/ticket/7296 . If you have ideas on making the web frontend (or my proposed strings) better, please write them there. Thanks!

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GSoC 2013: Enable flashproxy to use WebRTC
by Danilo Carvalho 30 Apr '13

30 Apr '13

Hello, My name is Danilo Carvalho, I am from ITA, Brazil, and I'm thinking about enabling flash proxy to use WebRTC, specially Data Channels, to connect between the client and the flash proxy. Some of the benefits involved would be: 1 - Flash proxies now would be able to receive incoming connections, this would remove the current need for the flash proxy to connect to the client. With the client being able to connect to the flash proxy, ticket( https://trac.torproject.org/projects/tor/ticket/5426) would be solved. If the client is the one controlling the connection, it wouldn't be needed for the flash proxy to guess his usage time. 2 - We could use the built in resources of the WebRTC to do nat traversal, through ICE and STUN servers. Although it isn't quite right to use public, company-owned ICE and STUN servers for that, we could build that functionality into the flash proxy, allowing the ones that are not behind nat to work as STUN and ICE servers for the others. Also, with the WebRTC already in use, it would be easy to port to NAT-PMP or UPnP, with I believe will be integrated into it in the future. Now, on the regards of how well spread WebRTC is, it's already built into Firefox and Chrome, and they both interoperate( http://blog.chromium.org/2013/02/hello-firefox-this-is-chrome-calling.html) On how much work it would demand: Some work would be required to enable the use of WebRTC in the javascript part of the flash proxy, and probably some parts will require rewriting, since the flash proxy will not operate in the same way anymore. The client plugin will need big changes, since it will need to connect via Data Channels, that is not trivial( https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-04#section-1) and most of the controlling would be done there. On the facilitator part, I believe only minor parts will require change, mostly to handle the flash proxy address giveaway(It should be controlled in some way, else an attacker could keep polling enough address to know the majority of them). Well, that's about it, I'll be pleased to hear your opinions about it, Greetings, Danilo

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