tor-dev January 2017

tor-dev@lists.torproject.org

32 participants
27 discussions

non-anonymous ephemeral onion services with stem
by Micah Lee 30 Jan '18

30 Jan '18

The stem documentation for create_ephemeral_hidden_service [1] says: "Changed in version 1.5.0: Added support for non-anonymous services." But I can't figure out to actually use this feature. There doesn't seem to be a new argument to say if you want your onion service to be non-anonymous. It also says, "Changed in version 1.5.0: Added the basic_auth argument." But there's a new basic_auth argument you can pass into the function to use that. [1] https://stem.torproject.org/api/control.html#stem.control.Controller.create…

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Proposal 247 (Hidden Service Vanguards) Overhaul
by Mike Perry 09 Jun '17

09 Jun '17

I spent some time trying to clean up proposal 247 based on everyone's comments, as well as based on my own thoughts. Please have a look if you commented on the original proposal, and complain if I've not taken your thoughts into account. (Aaron: In particular, I made several tradeoffs in favor of performance and DoS resistance that may be at odds with some of your suggestions, but I think the end result is still OK after looking into the Sybil rates and thinking about the adversary model in more detail. You may disagree). I've attached my updated version of the proposal inline in this mail, but the canonical updated proposal is in my remote at: https://gitweb.torproject.org/user/mikeperry/torspec.git/tree/proposals/247… Here's a summary of the changes (which are also listed in Git): * Try to make a coherent threat model and specify its assumptions * Fold in my comments about using disjoint sets ("buckets") for the third level guard. * Make the parameter discussion subsection its own section, and include tables with far more detail for the Sybil success rates. * Put the rotation period in a separate subsection from the number of guards * Switch to using min(X,X) and max(X,X) for the distribution for the second and third layer guard lifespans, respectively. Add a subsection describing this distribution (3.2.3) * Changed the default parameters based on these tables, and based on my own intuition about Tor's performance properties. * Move the load balancing, torrc, and other performance considerations to their own section (Section 5). * Move "3.2. Distinguishing new HS circuits from normal HS circuits" to section 4.1. * Fold in some of "3.3. Circuit nodes can now be linked to specific hidden services" into 4.1. Some of it I just removed, though, because I did not find it credible. * Added Roger's concerns about guard linkability to Section 4.2. * Added a denial of service subsection to Section 4.3. ================================ Filename: 247-hs-guard-discovery.txt Title: Defending Against Guard Discovery Attacks using Vanguards Author: George Kadianakis Created: 2015-07-10 Status: Draft 0. Motivation A guard discovery attack allow attackers to determine the guard node of a Tor client. The hidden service rendezvous protocol provides an attack vector for a guard discovery attack since anyone can force an HS to construct a 3-hop circuit to a relay (#9001). Following the guard discovery attack with a compromise and/or coercion of the guard node can lead to the deanonymization of a hidden service. 1. Overview This document tries to make the above guard discovery + compromise attack harder to launch. It introduces an optional configuration option which makes the hidden service also pin the second and third hops of its circuits for a longer duration. With this new path selection, we force the adversary to perform a Sybil attack and two compromise attacks before succeeding. This is an improvement over the current state where the Sybil attack is trivial to pull off, and only a single compromise attack is required. With this new path selection, an attacker is forced to do a one or more node compromise attacks before learning the guard node of a hidden service. This increases the uncertainty of the attacker, since compromise attacks are costly and potentially detectable, so an attacker will have to think twice before beginning a chain of node compromise attacks that he might not be able to complete. 1.1. Visuals Here is how a hidden service rendezvous circuit currently looks like: -> middle_1 -> middle_A -> middle_2 -> middle_B -> middle_3 -> middle_C -> middle_4 -> middle_D HS -> guard -> middle_5 -> middle_E -> Rendezvous Point -> middle_6 -> middle_F -> middle_7 -> middle_G -> middle_8 -> middle_H -> ... -> ... -> middle_n -> middle_n this proposal pins the two middles nodes to a much more restricted set, as follows: -> guard_3A_A -> guard_2_A -> guard_3A_B -> guard_3A_C -> Rendezvous Point HS -> guard_1 -> guard_3B_D -> guard_2_B -> guard_3B_E -> guard_3B_F -> Rendezvous Point Note that the third level guards are partitioned into buckets such that they are only used with one specific second-level guard. In this way, we ensure that even if an adversary is able to execute a Sybil attack against the third layer, they only get to learn one of the second-layer Guards, and not all of them. This prevents the adversary from gaining the ability to take their pick of the weakest of the second-level guards for further attack. 2. Design This feature requires the HiddenServiceGuardDiscovery torrc option to be enabled. When a hidden service picks its guard nodes, it also picks two additional sets of middle nodes `second_guard_set` and `third_guard_set` of size NUM_SECOND_GUARDS and NUM_THIRD_GUARDS respectively for each hidden service. These sets are unique to each hidden service created by a single Tor client, and must be kept separate and distinct. When a hidden service needs to establish a circuit to an HSDir, introduction point or a rendezvous point, it uses nodes from `second_guard_set` as the second hop of the circuit and nodes from that second hop's corresponding `third_guard_set` as third hops of the circuit. A hidden service rotates nodes from the 'second_guard_set' at a random time between MIN_SECOND_GUARD_LIFETIME hours and MAX_SECOND_GUARD_LIFETIME hours. A hidden service rotates nodes from the 'third_guard_set' at a random time between MIN_THIRD_GUARD_LIFETIME and MAX_THIRD_GUARD_LIFETIME hours. These extra guard nodes should be picked with the same path selection procedure that is used for regular middle nodes (though see Section 5.1 for performance reasons to restrict this slightly). Each node's rotation time is tracked independently, to avoid disclosing the rotation times of the primary and second-level guards. XXX how should proposal 241 ("Resisting guard-turnover attacks") be applied here? 2.1. Security parameters We set NUM_SECOND_GUARDS to 4 nodes and NUM_THIRD_GUARDS to 16 nodes (ie four sets of four). XXX: 3 and 12 might be another option here, in which case our rotation period for the second guard position can be reduced to 15 days. We set MIN_SECOND_GUARD_LIFETIME to 1 day, and MAX_SECOND_GUARD_LIFETIME to 33 days, for an average rotation rate of ~11 days, using the min(X,X) distribution specified in Section 3.2.2. We set MIN_THIRD_GUARD_LIFETIME to 1 hour, and MAX_THIRD_GUARD_LIFETIME to 18 hours, for an average rotation rate of ~12 hours, using the max(X,X) distribution specified in Section 3.2.2. XXX make all the above consensus parameters? Yes. Very yes, especially if we decide to change the primary guard lifespan. See Section 3 for more analysis on these constants. 3. Rationale and Security Parameter Selection 3.1. Threat model, Assumptions, and Goals Consider an adversary with the following powers: - Can launch a Sybil guard discovery attack against any node of a rendezvous circuit. The slower the rotation period of the node, the longer the attack takes. Similarly, the higher the percentage of the network is compromised, the faster the attack runs. - Can compromise any node on the network, but this compromise takes time and potentially even coercive action, and also carries risk of discovery. We also make the following assumptions about the types of attacks: 1. A Sybil attack is noisy. It will require either large amounts of traffic, multiple test circuits, or both. 2. A Sybil attack against the second or first layer Guards will be more noisy than a Sybil attack against the third layer guard, since the second and first layer Sybil attack requires a timing side channel in order to determine success, where as the Sybil success is almost immediately obvious to third layer guard, since it will now be returned as a rend point for circuits for the hidden service in question. 3. As soon as the adversary is confident they have won the Sybil attack, an even more aggressive circuit building attack will allow them to determine the next node very fast (an hour or less). 4. The adversary is strongly disincentivized from compromising nodes that may prove useless, as node compromise is even more risky for the adversary than a Sybil attack in terms of being noticed. Given this threat model, our security parameters were selected so that the first two layers of guards should be hard to attack using a Sybil guard discovery attack and hence require a node compromise attack. Ideally, we want the node compromise attacks to carry a non-negligible probability of being useless to the adversary by the time they complete. On the other hand, the outermost layer of guards should rotate fast enough to _require_ a Sybil attack. 3.2. Parameter Tuning 3.2.1. Sybil rotation counts for a given number of Guards The probability of Sybil success for Guard discovery can be modeled as the probability of choosing 1 or more malicious middle nodes for a sensitive circuit over some period of time. P(At least 1 bad middle) = 1 - P(All Good Middles) = 1 - P(One Good middle)^(num_middles) = 1 - (1 - c/n)^(num_middles) c/n is the adversary compromise percentage In the case of Vanguards, num_middles is the number of Guards you rotate through in a given time period. This is a function of the number of vanguards in that position (v), as well as the number of rotations (r). P(At least one bad middle) = 1 - (1 - c/n)^(v*r) Here's detailed tables in terms of the number of rotations required for a given Sybil success rate for certain number of guards. 1.0% Network Compromise: Sybil Success One Two Three Four Five Six Eight Nine Ten Twelve Sixteen 10% 11 6 4 3 3 2 2 2 2 1 1 15% 17 9 6 5 4 3 3 2 2 2 2 25% 29 15 10 8 6 5 4 4 3 3 2 50% 69 35 23 18 14 12 9 8 7 6 5 60% 92 46 31 23 19 16 12 11 10 8 6 75% 138 69 46 35 28 23 18 16 14 12 9 85% 189 95 63 48 38 32 24 21 19 16 12 90% 230 115 77 58 46 39 29 26 23 20 15 95% 299 150 100 75 60 50 38 34 30 25 19 99% 459 230 153 115 92 77 58 51 46 39 29 5.0% Network Compromise: Sybil Success One Two Three Four Five Six Eight Nine Ten Twelve Sixteen 10% 3 2 1 1 1 1 1 1 1 1 1 15% 4 2 2 1 1 1 1 1 1 1 1 25% 6 3 2 2 2 1 1 1 1 1 1 50% 14 7 5 4 3 3 2 2 2 2 1 60% 18 9 6 5 4 3 3 2 2 2 2 75% 28 14 10 7 6 5 4 4 3 3 2 85% 37 19 13 10 8 7 5 5 4 4 3 90% 45 23 15 12 9 8 6 5 5 4 3 95% 59 30 20 15 12 10 8 7 6 5 4 99% 90 45 30 23 18 15 12 10 9 8 6 10.0% Network Compromise: Sybil Success One Two Three Four Five Six Eight Nine Ten Twelve Sixteen 10% 2 1 1 1 1 1 1 1 1 1 1 15% 2 1 1 1 1 1 1 1 1 1 1 25% 3 2 1 1 1 1 1 1 1 1 1 50% 7 4 3 2 2 2 1 1 1 1 1 60% 9 5 3 3 2 2 2 1 1 1 1 75% 14 7 5 4 3 3 2 2 2 2 1 85% 19 10 7 5 4 4 3 3 2 2 2 90% 22 11 8 6 5 4 3 3 3 2 2 95% 29 15 10 8 6 5 4 4 3 3 2 99% 44 22 15 11 9 8 6 5 5 4 3 The rotation counts in these tables were generated with: def count_rotations(c, v, success): r = 0 while 1-math.pow((1-c), v*r) < success: r += 1 return r 3.2.2. Rotation Period As specified in Section 3.1, the primary driving force for the third layer selection was to ensure that these nodes rotate fast enough that it is not worth trying to compromise them, because it is unlikely for compromise to succeed and yield useful information before the nodes stop being used. For this reason we chose 1 to 18 hours, with a weighted distribution (Section 3.2.3) causing the expected average to be 12 hours. From the table in Section 3.2.1, it can be seen that this means that the Sybil attack will complete with near-certainty (99%) in 29*12 hours (14.5 days) for the 1% adversary, 3 days for the 5% adversary, and 1.5 days for the 10% adversary. Since rotation of each node happens independently, the distribution of when the adversary expects to win this Sybil attack in order to discover the next node up is uniform. This means that on average, the adversary should expect that half of the rotation period of the next node is already over by the time that they win the Sybil. With this fact, we choose our range and distribution for the second layer rotation to be short enough to cause the adversary to risk compromising nodes that are useless, yet long enough to require a Sybil attack to be noticeable in terms of client activity. For this reason, we choose a minimum second-layer guard lifetime of 1 day, since this gives the adversary a minimum expected value of 12 hours for during which they can compromise a guard before it might be rotated. If the total expected rotation rate is 11 days, then the adversary can expect overall to have 5.5 days remaining after completing their Sybil attack before a second-layer guard rotates away. 3.2.3. Rotation distribution In order to skew the distribution of the third layer guard towards higher values, we use max(X,X) for the distribution, where X is a random variable that takes on values from the uniform distribution. In order to skew the distribution of the second layer guard towards low values (to increase the risk of compromising useless nodes) we skew the distribution towards lower values, using min(X,X). Here's a table of expectation (arithmetic means) for relevant ranges of X (sampled from 0..N). The current choice for second-layer guards is noted with **, and the current choice for third-layer guards is noted with ***. Range Min(X,X) Max(X,X) 10 2.85 6.15 11 3.18 6.82 12 3.51 7.49 13 3.85 8.15 14 4.18 8.82 15 4.51 9.49 16 4.84 10.16 17 5.18 10.82*** 18 5.51 11.49 19 5.84 12.16 20 6.18 12.82 21 6.51 13.49 22 6.84 14.16 23 7.17 14.83 24 7.51 15.49 25 7.84 16.16 26 8.17 16.83 27 8.51 17.49 28 8.84 18.16 29 9.17 18.83 30 9.51 19.49 31 9.84 20.16 32 10.17** 20.83 33 10.51 21.49 34 10.84 22.16 35 11.17 22.83 36 11.50 23.50 37 11.84 24.16 38 12.17 24.83 39 12.50 25.50 4. Security concerns and mitigations 4.1. Mitigating fingerprinting of new HS circuits By pinning the middle nodes of rendezvous circuits, we make it easier for all hops of the circuit to detect that they are part of a special hidden service circuit with varying degrees of certainty. The Guard node is able to recognize a Vanguard client with a high degree of certainty because it will observe a client IP creating the overwhelming majority of its circuits to just a few middle nodes in any given 10-18 day time period. The middle nodes will be able to tell with a variable certainty that depends on both its traffic volume and upon the popularity of the service, because they will see a large number of circuits that tend to pick the same Guard and Exit. The final nodes will be able to tell with a similar level certainty that depends on their capacity and the service popularity, because they will see a lot of rend handshakes that all tend to have the same second hop. The most serious of these is the Guard fingerprinting issue. When proposal xxx-padding-negotiation is implemented, services that enable this feature should use those padding primitives to create fake circuits to random middle nodes that are not their guards, in an attempt to look more like a client. Additionally, if Tor Browser implements "virtual circuits" based on SOCKS username+password isolation in order to enforce the re-use of paths when SOCKS username+passwords are re-used, then the number of middle nodes in use during a typical user's browsing session will be proportional to the number of sites they are viewing at any one time. This is likely to be much lower than one new middle node every ten minutes, and for some users, may be close to the number of Vanguards we're considering. This same reasoning is also an argument for increasing the number of second-level guards beyond just two, as it will spread the hidden service's traffic over a wider set of middle nodes, making it both easier to cover, and behave closer to a client using SOCKS virtual circuit isolation. 4.2. Hidden service linkability Multiple hidden services on the same Tor instance should use separate second and third level guard sets, otherwise an adversary is trivially able to determine that the two hidden services are co-located by inspecting their current chosen rend point nodes. Unfortunately, if the adversary is still able to determine that two or more hidden services are run on the same Tor instance through some other means, then they are able to take advantage of this fact to execute a Sybil attack more effectively, since there will now be an extra set of guard nodes for each hidden service in use. For this reason, if Vanguards are enabled, and more than one hidden service is configured, the user should be advised to ensure that they do not accidentally leak that the two hidden services are from the same Tor instance. 4.3. Denial of service Since it will be fairly trivial for the adversary to enumerate the current set of rend nodes for a hidden service, denial of service becomes a serious risk for Vanguard users. For this reason, it is important to support a large number of third-level guards, to increase the amount of resources required to bring a hidden service offline by DoSing just a few Tor nodes. 5. Performance considerations The switch to a restricted set of nodes will very likely cause significant performance issues, especially for high-traffic hidden services. If any of the nodes they select happen to be temporarily overloaded, performance will suffer dramatically until the next rotation period. 5.1. Load Balancing Since the second and third level "guards" are chosen from the set of all nodes eligible for use in the "middle" hop (as per hidden services today), this proposal should not significantly affect the long-term load on various classes of the Tor network, and should not require any changes to either the node weight equations, or the bandwidth authorities. Unfortunately, transient load is another matter, as mentioned previously. It is very likely that this scheme will increase instances of transient overload at nodes selected by high-traffic hidden services. One option to reduce the impact of this transient overload is to restrict the set of middle nodes that we chose from to some percentage of the fastest middle-capable relays in the network. This may have some impact on load balancing, but since the total volume of hidden service traffic is low, it may be unlikely to matter. 5.2. Circuit build timeout The adaptive circuit build timeout mechanism in Tor is what corrects for instances of transient node overload right now. The timeout will naturally tend to select the current fastest and least-loaded paths even through this set of restricted routes, but it may fail to behave correctly if there are a very small set of nodes in each guard set, as it is based upon assumptions about the current path selection algorithm, and it may need to be tuned specifically for Vanguards, especially if the set of possible routes is small. 5.3. OnionBalance At first glance, it seems that this scheme makes multi-homed hidden services such as OnionBalance[1] even more important for high-traffic hidden services. Unfortunately, if it is equally damaging to the user for any of their multi-homed hidden service locations to be discovered, then OnionBalance is strictly equivalent to simply increasing the number of second-level guard nodes in use, because an active adversary can perform simultaneous Sybil attacks against all of the rend points offered by the multi-homed OnionBalance introduction points. 5.4. Default vs optional behavior We suggest this torrc option to be optional because it changes path selection in a way that may seriously impact hidden service performance, especially for high traffic services that happen to pick slow guard nodes. However, by having this setting be disabled by default, we make hidden services who use it stand out a lot. For this reason, we should in fact enable this feature globally, but only after we verify its viability for high-traffic hidden services, and ensure that it is free of second-order load balancing effects. Even after that point, until Single Onion Services are implemented, there will likely still be classes of very high traffic hidden services for whom some degree of location anonymity is desired, but for which performance is much more important than the benefit of Vanguards, so there should always remain a way to turn this option off. 6. Future directions Here are some more ideas for improvements that should be done sooner or later: - Maybe we should make the size and rotation period of secondary/third guard sets to be configurable by the user. - To make it harder for an adversary, a hidden service MAY extend the path length of its circuits by an additional static hop. This forces the adversary to use another coercion attack to walk the chain up to the hidden service. 7. Acknowledgments Thanks to Aaron Johnson, John Brooks, Mike Perry and everyone else who helped with this idea. 1. https://onionbalance.readthedocs.org/en/latest/design.html#overview -- Mike Perry

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[RFC] Proposal for the encoding of prop224 onion addresses
by George Kadianakis 28 Mar '17

28 Mar '17

Hello list, we've had discussions over the past years about how to encode prop224 onion addresses. Here is the latest thread: https://lists.torproject.org/pipermail/tor-dev/2016-December/011734.html Bikeshedding is over; it's time to finally pick a scheme! My suggested scheme basically follows from the discussion on that thread, and is heavily based on the Bitcoin address format: https://en.bitcoin.it/wiki/Base58Check_encoding https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addres… Here is the suggested scheme: onion_address = base32(version + pubkey + checksum) checksum = SHA3(".onion checksum" + version + pubkey) where: pubkey is 32 bytes (ed25519) version is one byte checksum is _truncated_ to two bytes With the above construction onion_address ends up being 56 bytes long (excluding the ".onion"): tbi5tdxbosiotphawjyu7f5pw5tlnvbvfjrj7meskbsnwr2bqbu2t4gg.onion tcrdnadkefvbdm3u56kz6lfh6v5lr24fpog5vzsy4n3djr2ymueu34ws.onion tcdw7lwmtp5pbwj2w7wf6amxdhmc62qitj2teu376r5s2fqke4r3uiq6.onion If people like the above suggestion, I will take the effort to engrave it in prop224. Here is the discussion section. Please provide feedback! [D1] How to use version field: The version field is one byte long. If we use it as an integer we can encode 256 values in it; if we use it as a bitmap we could encode properties and such. My suggestion is to simply use it as an integer like Bitcoin does. So we can assign value \x01 to normal onion services, and in the future we can assign more version tags if we need to. For example, we can give a different version field to onion services in the testnet. We can also reserve a range of values for application-specific purposes. [D1.1] Default version value: The next question is what version value to assign to normal onion services. In the above scheme where: onion_address = base32(version + pubkey + checksum) the value of 'version' basically determines the first two characters of the onion address. In Bitcoin, they've made it such that the default version value basically prefixes addresses with "1"; so all normal Bitcoin addresses start with 1 as in 14tDWDT9zqDufWZmiLqoaT9qJyHi7RRZPE What should we do in Tor? My suggestion is to use '\x98' as the default version value which prefixes all addresses with 't' (as in Tor). Check the examples I cited above. An alternative is to turn the scheme to: onion_address = base32(pubkey + checksum + version) where the version byte is at the end with no effect at usability. A heavier alternative would be to have two bytes of version so that we can just prefix them all with 'tor'... [D2] Checksum strength: In the suggested scheme we use a hash-based checksum of two bytes (16 bits). This means that in case of an address typo, we have 1/65536 probability to not detect the error (false negative). It also means that after 256 typos we will have 50% probability to miss an error (happy birthday!). I feel like the above numbers are pretty good given the small checksum size. The alternative would be to make the checksum four bytes (like in Bitcoin). This would _greatly_ increase the strength of our checksum but it would also increase our address length by 4 base32 characters (and also force us to remove leading padding from base32 output). This is how these 60-character addresses look like: tc2dty3zowj6oyhbyb5n3a2h3luztlx22hy2cwdvn37omsv7quy7rxiysn3a.onion tbdczrndtadzdhb6iyemnxf7f4i6x7yojnunarlrvt2virtmrecmwgx5golq.onion tc6pcgyorusw3jj5tosxakmcwfmcend2q4g2qnbjtkhuuh4dcgvs4rl4rdaa.onion You probably don't notice the size difference compared to the 56-character addresses, which perhaps is an argument for adopting a four byte checksum. Let me know what you think about this. [D3] Do we like base32??? In this proposal I suggest we keep the base32 encoding since we've been using it for a while; but this is the perfect time to switch if we feel the need to. For example, Bitcoin is using base58 which is much more compact than base32, and also has much better UX properties than base64: https://en.bitcoin.it/wiki/Base58Check_encoding#Background If we wanted to get a more compact encoding, we could adopt base58 or make our own adaptation of it. In this proposal I'm using base32 for everything, but I could be persuaded that now is the time to use a better encoding. Let me know what you think! Thanks :)

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Re: [tor-dev] Flashproxy has been Deactivated by Stanford? Why?
by David Fifield 12 Mar '17

12 Mar '17

On Tue, Dec 20, 2016 at 01:21:04AM +0800, tomli(a)riseup.net wrote: > It turned out that the entire code has been commented out and apparently > Flashproxy became > out of service. Why? Has the project discontinued, or just down for > maintenance? Flash proxy is basically retired now. It was removed from Tor Browser a year ago (https://bugs.torproject.org/17428) after it had been supplanted by more effective transports. I don't know why there was a blog post on December 16 promoting flash proxy, because it's no longer used. Even when flash proxy was part of Tor Browser, it had very few users (less than 100; see https://metrics.torproject.org/userstats-bridge-transport.html?start=2013-0…), probably because of the difficulty of running it as a client (https://trac.torproject.org/projects/tor/wiki/doc/PluggableTransports/Flash…). Compare those user numbers to meek (current about 10K) or obfs4 (30K). The reason I haven't asked people to stop running the flash proxy badge is we're working on a new pluggable transport along the same lines but without the usability challenges: https://trac.torproject.org/projects/tor/wiki/doc/Snowflake. I was thinking about adapting existing flash proxy badges to provide capacity to Snowflake instead. This would go for Cupcake as well. The need to get the badge running again hasn't been pressing because Snowflake isn't deployed yet, but we're getting close. The badge was deactivated by Stanford (without my knowledge, but I found out a while ago). I arranged with them to move it to alternate hosting and have them install a redirect, but that has been a low priority behind other work on Snowflake. I'm sorry about the confusion. If I get some time I'll add a notice to the flash proxy main page saying that it's been retired.

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archive.is and archive.fo are using CloudFlare. Is the TorBrowser add-on cfc useless now?
by Christian Pietsch 07 Feb '17

07 Feb '17

Hi Yawning, hi all, sorry if this is old news, but I just noticed that archive.is not only redirects me to archive.fo (which I noticed before), but archive.fo now greets me with a CloudFlare captcha. Considering that cfc was created in order to evade the CloudFlare captcha, this is quite a disappointment. Is cfc useless now? Can it be fixed? David F suggested using Memento which I think is an interesting idea, having participated in one of their hackathons. One caveat: Memento would point to to various archives not all of which might be suitable. What is the reason why archive.org is not used? I hear they are almost done setting up an onion service for the Internet Archive. Cheers, C: On Mon, Apr 18, 2016 at 10:16:31PM +0000, Yawning Angel wrote: > Source: https://git.schwanenlied.me/yawning/cfc -- Christian Pietsch, volunteering for Digitalcourage e.V., Bielefeld, Germany Nominations sought for the German Big Brother Awards: https://bigbrotherawards.de Verfassungsbeschwerde gegen Vorratsdatenspeicherung: https://digitalcourage.de/weg-mit-vds Appell gegen den geplanten Datenschutz-Abbau: https://digitalcourage.de/rettet-den-datenschutz Umfrage zum Datenschutztag 2017: https://datenschutztag.org/survey/

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onionoo: understanding 'exit_policy_v6_summary'
by nusenu 01 Feb '17

01 Feb '17

Hi Karsten, given this torrc configuration and exit policy: https://lists.torproject.org/pipermail/tor-relays/2017-January/011806.html would you expect onionoo's 'exit_policy_v6_summary' to be not set? [1] https://onionoo.torproject.org/protocol.html#details writes: > Missing if the relay rejects all connections to IPv6 addresses. thanks, nusenu [1] https://atlas.torproject.org/#details/5E762A58B1F7FF92E791A1EA4F18695CAC667… {"nickname":"sorrentini","fingerprint":"5E762A58B1F7FF92E791A1EA4F18695CAC6677CE","or_addresses":["128.199.76.145:443","[2400:6180:0:d0::18a7:d001]:443"],"last_seen":"2017-01-27 13:00:00","last_changed_address_or_port":"2017-01-11 09:00:00","first_seen":"2016-11-30 03:00:00","running":true,"flags":["Exit","Fast","Running","Stable","Valid"],"country":"sg","country_name":"Singapore","region_name":"Central Singapore Community Development Council","city_name":"Singapore","latitude":1.2855,"longitude":103.8565,"as_number":"AS133165","as_name":"Digital Ocean, Inc.","consensus_weight":420,"host_name":"128.199.76.145","last_restarted":"2017-01-21 03:29:31","bandwidth_rate":1073741824,"bandwidth_burst":1073741824,"observed_bandwidth":1225379,"advertised_bandwidth":1225379,"exit_policy":["reject 0.0.0.0/8:*","reject 169.254.0.0/16:*","reject 127.0.0.0/8:*","reject 192.168.0.0/16:*","reject 10.0.0.0/8:*","reject 172.16.0.0/12:*","reject 128.199.76.145:*","accept *:53","accept *:80","accept *:110","accept *:143","accept *:220","accept *:443","accept *:873","accept *:989-990","accept *:991","accept *:992","accept *:993","accept *:995","accept *:1194","accept *:1293","accept *:3690","accept *:4321","accept *:5222-5223","accept *:5228","accept *:9418","accept *:11371","accept *:64738","reject *:*"],"exit_policy_summary":{"accept":["53","80","110","143","220","443","873","989-993","995","1194","1293","3690","4321","5222-5223","5228","9418","11371","64738"]},"contact":"0x44BB1BA79F6C6333 <tor-admin AT zumbi dot com dot ar>","platform":"Tor 0.2.9.8 on Linux","effective_family":["$82C92FBAF2196EC346670D12BB9650FE9FF55741","$EFD2EEB91E5C5D8CB999B1EC68D89E51F8776AC7"],"consensus_weight_fraction":8.568019E-6,"guard_probability":0.0,"middle_probability":0.0,"exit_probability":3.799685E-5,"recommended_version":true,"measured":true}

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[RFC] Directory structure of prop224 onion services
by George Kadianakis 01 Feb '17

01 Feb '17

Hey list, with service-side prop224 implementation moving forward, we need to pin down the directory structure of prop224 onion services. This will be very similar to the current directory structure, but with some mods to facilitate assymetric client authorization keys and offline keys. As people have pointed out, the HS directory structure matters less after the introduction of ephemeral ADD_ONION onion services, but still it's an important part of onion service sysadmin UX. So the HiddenServiceDir directory will contain the following items: - "./hostname" [FILE] This is a file containing the onion address of the onion service. As you can see it's the same filename as in v2. Should we suffix it with v3 to make it clear that it's v3 onion? Would we ever have v2 and v3 onions living in the same directory? - "./private_key_ed25519" [FILE] This is the file containing the private master ed25519 key of the onion service. If offline keys are _enabled_, then this file doesn't exist and instead a directory is made containing blinded keys for every day [TODO: The directory format here will be specified in the future]. - "./client_authorized_pubkeys" [FILE] If client authorization is _enabled_, this is a newline-separated file of "<client name> <pubkey>" entries for authorized clients. You can think of it as the ~/.ssh/authorized_keys of onion services. - "./client_authorized_privkeys/" [DIRECTORY] "./client_authorized_privkeys/alice" [FILE] "./client_authorized_privkeys/bob" [FILE] "./client_authorized_privkeys/charlie" [FILE] If client authorization is _enabled_ _AND_ if the hidden service is responsible for generating and distributing private keys for its clients, then this directory contains files with client's private keys. The idea is that these files can be shredded and deleted after the private key has been passed to the client. For more context here, please read the client authorization thread in [tor-dev] and see 'Appendix F' of prop224 for more details on how this works. So this is it. The above should handle most uses of onion services + client authorization. The directory format of offline keys will be specified as we move forward with implementation. Hope things here are not too controversial. Looking forward to your feedback. In a few days, I will add a small Appendix section to prop224 with the above, and also fix the parts of 'Appendix F' that got outdated since then. Cheers!

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Re: [tor-dev] GAEuploader
by Katherine Li 01 Feb '17

01 Feb '17

Hi Tim, Thank you for your insightful questions! My responses are below: *> Is this the cheapest zone/region for computation or bandwidth? If I am not in the US, would it be faster or cheaper for me to use a local google data center?* Yes, it would be faster for you to use a local google data center <https://cloud.google.com/appengine/docs/locations>. I have added a variable "REGION" in the script of the uploader. You can now change the region by replacing "us-central" with another region. I have also added an explanation of how to do this in the README. Below is a list of all the regions: REGION SUPPORTS STANDARD SUPPORTS FLEXIBLE asia-northeast1 YES YES europe-west YES NO us-central YES YES us-east1 YES YES You can also obtain this list via the following terminal command <https://cloud.google.com/sdk/gcloud/reference/app/regions/list>(with GAEuploader as your current directory): ./google-cloud-sdk/bin/gcloud app regions list As you pointed out, I have set the zone to zone3 in my original code. However, it turned out that zone is relevant only when working with Google Compute Engine <https://cloud.google.com/compute/>, which is not the case for GAEuploader. So I have removed the line "subprocess.check_call([" ./google-cloud-sdk/bin/gcloud", "beta", "config", "set", "compute/zone", " zone3"]) *> Which tor bridge does the traffic for these instances go through? (Or does this set up a tor bridge as well?)* The bridge uses https://meek.bamsoftware.com/, which is on the same host as the meek-azure bridge, but not rate-limited like meek-azure is. You can find more information on Tor relays at its Atlas page: https://atlas.torproject.org/#details/C20658946DD706A7A2181159A1A04C D838570D04 If you want to use a different bridge, you can edit the file appengine/reflect.go before running uploader: forwardURL = "https://meek.bamsoftware.com/" Thanks again for your input! Please let me know if you have any more questions/feedback. Best, Katherine Li

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git-update: transparently torified git pulls
by carlo von lynX 31 Jan '17

31 Jan '17

Hi, here it is. Style may be crude as I usually write perl. #!/bin/sh # # A variant of git pull which operates over Tor and # - figures out when 'torify' needs to be used # - shows the changes that were made to the repository # - before attempting to merge # --lynX & heldensaga, 2017 # # I recommend piping the output into # vim -R "+set syntax=diff" # but since that isn't everybody's choice of editor # I won't work it into this script... # would be more elegant to tell you how to # configure this in your .git/config? gitdiff="git diff -b -M77% --minimal" # 'resolve' has served me well as default strategy gitmerge="git merge -s resolve" branch="$*" if test x"$*" = x; then branch="origin" fi # echo $branch url=`git remote get-url $branch` if test x"$url" = x; then exit fi # echo $url case $url in http*) torify="" echo "*** Fetching from $url via web proxy" ;; *) torify="torsocks" echo "*** Fetching from $url via torsocks" esac # echo $torify $torify git fetch $branch \ && $gitdiff master..$branch/master \ && exec $gitmerge $branch/master

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ExitPortStatistics interpretation
by nusenu 30 Jan '17

30 Jan '17

Hi, I'm looking at ExitPortStatistics. Since the spec [1] is not very specific, I wanted to confirm that my assumption is correct: The current tor implementation includes the 10 most relevant ports, correct? (highest number of bytes or stream) example: exit-streams-opened 80=5178868,182=1092,443=3499276,5000=29600,5753=8920,6881=43496,8080=31184,8333=472,8999=16572,51413=51496,other=1925104 so the ports 80 182 443 5000 5753 6881 8080 8333 8999 51413 are the most used exit ports on that given relay (not by that order). thanks, nusenu [1] https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n1082: > "exit-kibibytes-written" port=N,port=N,... NL > [At most once.] > "exit-kibibytes-read" port=N,port=N,... NL > [At most once.] > > List of mappings from ports to the number of kibibytes that the > relay has written to or read from exit connections to that port, > rounded up to the next full kibibyte. Relays may limit the > number of listed ports and subsume any remaining kibibytes under > port "other". > > "exit-streams-opened" port=N,port=N,... NL > [At most once.] > > List of mappings from ports to the number of opened exit streams > to that port, rounded up to the nearest multiple of 4. Relays may > limit the number of listed ports and subsume any remaining opened > streams under port "other".

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tor-dev January 2017