- tor-relays - lists.torproject.org

Traffic stats without vidalia
by Name Withheld 19 Jun '12

19 Jun '12

I've done some searching, but I can't seem to find any references to how I check the traffic stats (current b/w use, total MB passed, etc) for my node when running on a linux (CentOS 6) platform. I've built a new vps with a huge pipe that's command-line-only to maximize performance, but I'm noticing that I can't tell if it's working well without being able to view basic statistical info within that CLI environment. Does anyone know the solution to this? Thank you very much.

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Problems with nameservers and permissions
by George 18 Jun '12

18 Jun '12

I've just started running a relay on Linux with Tor starting automatically, however arm reported that "all nameservers have failed" and, unsure what to do, I stopped Tor to go look up the problem. Then when I tried to start it in Terminal again I'm greeted with this: Jun 18 11:53:15.000 [warn] Couldn't open "/home/george/.tor/lock" for locking: Permission denied Jun 18 11:53:15.000 [err] set_options(): Bug: Acting on config options left us in a broken state. Dying. I've tried changing the permissions of the directory and the lock file but it still says permission denied. What should I do? I'm running Tor 0.2.3.17-beta-1 on Ubuntu 12.04. Thank you for any help, George

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Failed to bind one of the listener ports / V. 2.3.17
by Christian 18 Jun '12

18 Jun '12

Hi all, since the last update from the repositories took place where I replaced the torrc file by the new version, I get the error message indicating no binding to the listener ports. I use Ubuntu lucid and Tor 2.3.17-beta-1~lucid+1 as a bridge. My ORPort section reads as follows: ORPort 443 NoListen ORPort 0.0.0.0:9090 NoAdvertise Am I missing something? I have forwarded external port 443 to port 9090 on my machine on my router. The setup consists of only one machine and the router. It worked well until this afternoon. ;-) I read about a copy and paste issue in config.c on the web, but it had been marked solved in February and doesn't seem to be for non-compilers like me. I really appreciate your kind help and thank you in advance. Greetings, christian

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Tor Network Map advertising available B/W way too low
by Name Withheld 14 Jun '12

14 Jun '12

Hello, I just set up an exit node (PrivacyFoundation on the list), and while I've got 5mbps up, it only advertises as 80-90kb b/w available. That's not at all accurate, and I think it's meaning the connection is ending up way underutilized, since I'm not seeing much traffic on the b/w graph. How do I change the advertised b/w? Thanks!

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running first Relay, low budget VPS on a Gigabit line
by tim 12 Jun '12

12 Jun '12

Hi, I have installed my first Tor-Relay on a low priced test VPS (1 BTC/m) hosted in NL some days ago. Today iftop shows the VPS puts 35 MByte/s in both directions through the line. *Phew* The hosting plan includes 50GB per month so I'm a bit over the fair use. What would you do? Let it run? throttle down? do no harm? Other than expected I only got a short mail with ssh login from them. The answer to my question if customers get some kind of admin-panel was: no, this would be higher security risk. contact us we do it in 2 hours. Any suggestions how to measure the traffic would be appreciated, must be roughly 12 TB the last 2 days. -- http://www.fastmail.fm - Accessible with your email software or over the web

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ARM 1.4.5 has a very high cpu consumption
by tor-admin 10 Jun '12

10 Jun '12

Hi, today I updated arm from 1.4.4.1 to 1.4.5. After this update I noticed that the arm display is very unresponsive. The arm cpu jumps ever couple of seconds up to 90-100 %. If this happens arm does not update its display. This can be observed on all pages. I monitor two high capacity nodes with each about around 10K concurrent connections. With 1.4.4.1 the arm cpu was normally below 5 %. The tor server runs debian squeeze with python 2.6.6. Is this a known issue? Any options other that downgrading back to 1.4.4.1? Regards, Klaus

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rpm init script not setting ulimit properly
by Aaron Hopkins 06 Jun '12

06 Jun '12

I noticed my exit node (tordienet) hovering around 1024 connections open, and checked /proc/<pid>/limits (available on newer kernels) and noticed that the filedescriptor ulimit was at the default 1024, which is likely not a great plan. I'm using the stock /etc/init.d/tor startup script that came in the tor-0.2.3.12.alpha-tor.0.rh5_7 RPM offered by the YUM repo http://deb.torproject.org/torproject.org/rpm/centos5-experimental. It attempts to set ulimit, but at least at startup on my Centos 5.8 openvz container, there's a soft limit set at 1024 filedescriptors, which requires the -S flag to ulimit to override. I changed line 87 of /etc/init.d/tor to: if ulimit -SHn "$MAX_FILEDESCRIPTORS" ; then And /proc/<pid>/limits shows tor running with the appropriate limits now. Unfortunately, this is likely to get reverted with the next package update. Is anyone else using the stock RPMs seeing the same behavior? -- Aaron

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case law on for exit nodes
by Rejo Zenger 28 May '12

28 May '12

Hi, Who knows about cases where the owner of Tor exit node was prosecuted or taken to court for information that was up- or downloaded using his/her Tor node? Basically, I'm looking for case law on running Tor exit-nodes. I am especially interested in case law from countries in Europe, but other examples are most welcome as well. If there is an interesting set of verdicts, I'll compile a summary and I'll share it with this list. Thanks for your help! -- Rejo Zenger . <rejo(a)zenger.nl> . 0x21DBEFD4 . <https://rejo.zenger.nl> GPG encrypted e-mail preferred . +31.6.39642738 . @rejozenger

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Re: [tor-relays] tuning MaxAdvertisedBandwidth for CPU
by Scott Bennett 27 May '12

27 May '12

On Thu, 24 May 2012 13:13:56 -0400 micah anderson <micah(a)riseup.net> wrote: >i've got an exit node that is doing a fair bit of bandwidth, but I think it is CPU bound at this point because I am >getting these: > >Your computer is too slow to handle this many circuit creation requests! Please consider using the >MaxAdvertisedBandwidth config option > >i'm wondering what I should set the MaxAdvertisedBandwidth to if I am averaging this type of traffic: >http://torstatus.blutmagie.de/router_detail.php?FP=131b60b9afe6aea60042132d… > >it seems from the graphs, there are some clear plateaus at around >5100000, but I figured that folks here might have some suggestions that >are better than just setting MaxAdvertisedBandwidth just to that number Before you mess around with MaxAdvertisedBandwidth, which really doesn't work as advertised in the man page, try just adding this to your torrc file: MaxOnionsPending 250 That should take care of the occasional moments when the onion skin queue overflows. Scott Bennett, Comm. ASMELG, CFIAG ********************************************************************** * Internet: bennett at cs.niu.edu * *--------------------------------------------------------------------* * "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 * **********************************************************************

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New contact info for guard node Austrina
by Samuel Whited 26 May '12

26 May '12

Dear relay operators / users: I operate the guard node Austrina (fp: CA54 C9F2 AA56 FE26 D7A1 6F26 93F6 5385 E85E 2D75) and have recently updated my public key. Any sensitive communications should now use public key 0xEC2C9934 (fp: F259 8DED 56ED E408 FD41 484B FB39 BCF7 EC2C 9934) available from pgp.mit.edu. Please update your keystores, and verify that the new key is cross-signed with the old one (0x0DBB515F). Verification can also be performed via DNS — `dig +short sam._pka.samwhited.com TXT` should give the same fingerprint as above and provide an alternate download location. Contact info on the node should update shortly. Thanks, Sam -- Sam Whited pub 4096R/EC2C9934 SamWhited.com sam(a)samwhited.com 404.492.6008

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tuning MaxAdvertisedBandwidth for CPU
by micah anderson 26 May '12

26 May '12

i've got an exit node that is doing a fair bit of bandwidth, but I think it is CPU bound at this point because I am getting these: Your computer is too slow to handle this many circuit creation requests! Please consider using the MaxAdvertisedBandwidth config option i'm wondering what I should set the MaxAdvertisedBandwidth to if I am averaging this type of traffic: http://torstatus.blutmagie.de/router_detail.php?FP=131b60b9afe6aea60042132d… it seems from the graphs, there are some clear plateaus at around 5100000, but I figured that folks here might have some suggestions that are better than just setting MaxAdvertisedBandwidth just to that number thanks! micah --

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too many abuse reports
by mick 23 May '12

23 May '12

Hi I have today, reluctantly, switched my node torofotheworld.aibohphobia.org from an exit node to relay only. My ISP has stayed faithful over several abuse reports in the past, but this week following two more in quick sucession (from brazilian government services by the look of it) they have asked that I shut down the exit policy. Rather than lose the node entirely, I have agreed. Some bozo has been using sqlmap to scan servers through tor. Mick --------------------------------------------------------------------- blog: baldric.net fingerprint: E8D2 8882 F7AE DEB7 B2AA 9407 B9EA 82CC 1092 7423 ---------------------------------------------------------------------

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Configuring a Tor relay to *not* accept torrent traffic
by Red Rover 20 May '12

20 May '12

Hi there, :-) I am running a Tor relay on a VPS. How do I configure it to NOT accept torrent traffic? I have just received an abuse report from my hosting company. All the best, Redrover

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reg : closing circuits and corresponding TLS connections when application terminates
by Sambuddho Chakravarty 19 May '12

19 May '12

Hi all I am playing around with an experimental setup of a private Tor network and I am using the control protocol to setup custom circuits. Before establishing the custom circuits on the Tor client , I set the following options: __DisablePredictedCircuits:1 MaxOnionsPending : 1 newcircuitperiod : 999999999 maxcircuitdirtiness : 999999999 CircuitStreamTimeout : 999999999 CircuitIdleTimeout : 999999999 Thereafter, I turn off existing circuits on the client and establish my own circuit using nodes in my private Tor network. Then the client communicates to a server via this circuit. When the client-server communication ends, the circuit closes by itself. Thereafter, in sometime the corresponding OP-OR connections also close. Is there a way to keep the circuit and/or OP-OR connections alive long after the client-server communication has terminated ? Secondly, I don't see all TLS connections corresponding to the requested circuit in all the relays. Eg. I am using thee hosts -- A, B and C for the private network where, A runs two directory authorities and an OR, while B and C run only ORs. The Tor client of my setup establishes circuit through A, B and C using the above configuration parameters. 'getinfo' reports that the requested circuit has been established but I only see TLS connection betwen A and C..is there a reason why this is the case. Also, in my network, C has no exit policies, while A and B have 'reject *:*' exit policies (just to make sure that all TCP connections exit via C). Thanks Sambuddho

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If you're using OpenSSL 1.0.1, upgrade to 1.0.1c
by Nick Mathewson 10 May '12

10 May '12

Hi, all! If you are using any version of openssl 1.0.1, 1.0.1a, or 1.0.1b, you should know that it's affected by a recent security advisory: https://www.openssl.org/news/secadv_20120510.txt If I am reading the diffs for this bug right, it looks like it would attacker to crash a server remotely. To avoid that, I'd recommend that all Tor nodes running any version of OpenSSL 1.0.1 should upgrade to 1.0.1c. Non-1.0.1 version of OpenSSL have this bug in their DTLS implementations, but Tor doesn't use DTLS. We'll try to get new packages out soon. yrs, -- Nick

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Verizon Abuse Notice from Limited relay
by Michael Millspaugh 10 May '12

10 May '12

Hey all - I've been running a relay here for about 2-3 years now, with limited problems, especially since I switched to the more restrictive reduced exit policy (only allowing a few ports). However, I just received this today, which is new and alarming. I've replied with the boilerplate, but I'm worried as I've never heard from verizon since I went reduced, and they are the fastest and most reliable ISP (fiber to the home) in my part of the states. Here's the message, truncated: On 05-09-2011, your account was reported to have been used in an attempt to gain unauthorized access to another system, or to transmit malicious traffic to another Internet user. It is possible your system may have been infected by a virus or a botnet that is causing this action. Report and/or Logs: Timestamp: 2012-05-09 11:28:55 (GMT) Alert: COSED [CSG-GOP-009] SCAN Sqlmap SQL Injection Scan Source: 96.242.209.159 (49608) Destination: 200.189.113.50 (80) Content: LL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,% 20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,% 20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,% 20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,%20NULL,% 20NULL,%20NULL,%20NULL--%20%20AND%20%27tysA%27%3D%27tysA& codigo=09590039044&orgcom=116100&serie=E000874295&tipo= DEFESA%20PREVIA&result=INDEFERIDO&motivo=015&auto=116100-E000874295 HTTP/1.1 Accept-Encoding: identity Accept-Language: en-us,en;q=0.5 Connection: close Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 User-Agent: sqlmap/1.0-dev (r4997) (http://www.sqlmap.org) Accept-Charset: ISO-8859-15,utf-8;q=0.7,*;q=0.7 Host: celepar7.pr.gov.br Pragma: no-cache Cache-Control: no-cache,no-store -- TERMS OF USE. By reading this e-mail, you agree, on behalf of your employer, to release me from all obligations and waivers arising from any and all NON-NEGOTIATED agreements, terms-of-use, licenses, terms-of-service, shrinkwrap, clickwrap, browsewrap, confidentiality, non-disclosure, non-compete and acceptable use policies ("BOGUS AGREEMENTS") that I have entered into with your employer, its partners, licensors, agents and assigns, in perpetuity, without prejudice to my ongoing rights and privileges. You further represent that you have the authority to release me from any BOGUS AGREEMENTS on behalf of your employer.

3 2

bridge usage summary in vidalia bridge bundle
by eliaz 10 May '12

10 May '12

When I installed Vidalia/Tor from vidalia-bridge-bundle-0.2.2.35-0.2.17, the Bridge Usage Summary the program never appeared. This turned out to be because by default the installed program points to geiop at AppData\Roaming\tor\ . This is incorrect, the file is in AppData\Local\Tor\ . Writing GeoIPFile C:\...\...\AppData\Local\Tor\geoip into torrc fixes this and now the Bridge Usage Summary appears. I don't know if this is just a glitch of my machine (Vista x 64) or if the code needs to be corrected, but I thought I'd report it. By default the bridge bundle places files in three separate folders in AppData\Local\ and Appdata\Roaming\ . Collecting these in one place would make it a bit easier for the user to reconfigure if necessary. - eliaz ---- gpg: 0xE498E90D

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sustained bandwidth drop through noisetor
by Andy Isaacson 04 May '12

04 May '12

noisetor-01 was pushing 300-400 Mbps of traffic from 2012-02-15 through 2012-04-13. Since mid-April we've seen traffic decrease significantly; over the last week, our daily peak has been 260 Mbps (versus 450 Mbps in March) and our daily trough has been 100 Mbps (versus 300 Mbps in March). The traffic levels dropped off in a smooth fashion over a 10 day period, April 15-25 if I read the graphs correctly. There's no sign that anything is amiss on the node; CPU and memory usage are consistently lower, today, than they were in March -- as expected, given the lower utilization. The logs are silent. I've been postprocessing torstatus's Tor_query_EXPORT.csv regularly, and it appears that the overall exit throughput of the network has gone up slightly over the last few months; some new significant nodes came online during 2012Q1 and may have affected the traffic distribution. However, while noisetor has seen a significant drop, other families of exit nodes have seen their bandwidth go up or stay steady. Has there been a change in the routing algorithm, or any other network changes that might explain this drop? Thanks, -andy

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Re: [tor-relays] [tor-dev] Can we stop sanitizing nicknames in bridge descriptors?
by Karsten Loesing 03 May '12

03 May '12

[Cc'ing tor-relays, because this discussion might be relevant for relay/bridge operators, too. Please keep the discussion on tor-dev. See https://lists.torproject.org/pipermail/tor-dev/2012-May/003489.html for the whole thread.] Hi Sebastian, On 5/2/12 9:35 PM, Sebastian G. <bastik.tor> wrote: > [...] > > Do similar names actually mean that bridges are located where the relay > is? (Apparently you've got the data to see these correlations) A fine question. How do we define "similar" and "located where the relay is?" I can see how a relay "bastik1" and a bridge "bastik2" have similar nicknames, but would we also teach a program that "bastikrelay" and "bastikbridge" are similar? And are two IP address in the same, say, /30 located nearby, or is the same /28 or even /24 okay, too? So, while we have the data to see these correlations, I think that whatever similarity algorithm we come up with, somebody else might come up with something smarter. If we do the analysis you suggest and learn that it's safe to include nicknames, that doesn't say very much. Only because we have the data to confirm how well our attack would works doesn't automatically mean we're in a good position to design the attack. If you want to run this analysis with the 2008 tarball (assuming there won't be general objections within the next two weeks), I'm happy to take your list of likely bridge IP addresses and tell you how accurate your algorithm is. > "We don't need it, so better remove it." I really like that. I think we're really conservative with giving out bridge data, and that's good. At the same time there's a value in giving out information about bridges, so that "remove everything" is not a good answer. For example, I think if we give bridge operators better feedback how their bridge is doing, we'll suddenly have a lot more bridges. Making it easy for bridge operators to use Atlas would be a good step into that direction. The same applies to funders who realize from our statistics how successful the Tor Cloud project is and who then want to fund it more to make it more usable, support more cloud providers, etc. >> And are we giving away anything else with the nicknames? > > Maybe it's location ;) > > As I read "hints on the location" for the first time; I though it would > mean that "TowerBridge" or "BridgeofLondon" would be bad since it could > hint to London. Well, in that case you'd learn that there's a (Tor) bridge in London. But that wouldn't help you very much, would it? > Could it make sense to ask the same question on the tor-relay list? Here > you (the Tor people) have more data again and know who subscribed to > both lists. I for myself assume that relay and bridge operators, which > could object, because it's their naming scheme that could reveal > something, are more likely to be subscribed to tor-relays. Good idea. I added tor-relays to the Cc to let relay/bridge operators know. Let's keep this discussion on tor-dev though. >> And if nobody >> screams, I'll provide the remaining tarballs containing original >> nicknames another two weeks later. > > Probably two weeks later, since unpacking, processing and re-packing > takes some time :) I know the sanitized ones are large when they are > unpacked. Windows needs some time to delete the extracted files. Right. :) I'll probably start sanitizing all bridge descriptors at once in two weeks, starting with the 2008 ones, and provide only the 2008 tarball then. It's going to keep my CPU and disks busy for a while. Thanks for your input! Best, Karsten

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Towards a Tor Node Best Best Practices Document
by Mike Perry 01 May '12

01 May '12

It's occurred to me that we have yet to provide any official recommendations with respect to best practices for operating Tor relays. This post is my attempt to define a reasonable threat model and use it to develop some recommendations. My plan is to post it here first, to subject it to review by the relay operator community. After operators have a chance to comment, the plan is to relocate the document to the Tor Wiki and/or a blog post. As always, to focus our thoughts, we start with the adversary's goals. Adversary Goals There is a significant difference between adversaries that can see inside of router-to-router TLS vs those that cannot. I believe this capability distinction governs the adversary goals in terms of compromising relays as opposed to merely externally observing them. Adversaries that can unwrap router TLS can perform every attack that an actual node can perform, at any location between the user and the node, and/or between the node and other nodes. In particular, adversaries that can see inside router TLS can perform tagging attacks (see https://lists.torproject.org/pipermail/tor-dev/2012-March/003361.html) as well as perform circuit-specific active and passive timing analysis. These attacks can be quite severe. An adversary that is able to obtain Guard identity keys is free to perform a tagging attack anywhere on the Internet. In other words, if the adversary is interested in monitoring a particular user, the adversary need only obtain the identity keys for that user's 3 guard nodes, and from that point on, the adversary will be able to transparently monitor everything that user does by way of using tagging to bias the users paths to connect only to surveilled exit nodes who also have had their identity keys compromised. Based on this distinction, it seems that some simple best practices can increase the costs of an adversary that wishes to compromise tor traffic. Let's now consider how the adversary goes about compromising router TLS. Attack Vectors There are two high-level vectors towards seeing inside node-to-node TLS (which uses ephemeral keys that are rotated daily and authenticated via the node's identity key). Both high-level vectors therefore revolve around node identity key theft. Attack Vector #1: One-Time Key Theft The one-time adversary is interested in performing a grab of keys and then operating transparently upstream afterwords. This adversary will take the form of a coercive request at a datacenter/ISP to extract identity node key material and from then on, operate externally as a transparent upstream MITM, creating fake ephemeral TLS keys authenticated with the stolen identity key. Tor nodes that encounter this adversary will likely see it in the form of unexplained reboots/mysterious downtime, which are inevitable in the lifespan of any Tor node. Attack Vector #2: Advanced Persistent Threat Key Theft If one-time methods fail or are beyond reach, the adversary has to resort to persistent machine compromise to retain access to node key material. The APT attacker can use the same vector as #1 or perhaps an external vector such as daemon compromise, but they then must also plant a backdoor that would do something like trawl through the RAM of a machine, sniff out the keys (perhaps even grabbing the ephemeral TLS keys directly), and transmit them offsite for collection. This is a significantly more expensive position for the adversary to maintain, because it is possible to notice upon a thorough forensic investigation during a perhaps unrelated incident, and it may trigger firewall warnings or other common least privilege defense alarms inadvertently. Unfortunately, it is also a more expensive attack to defend against, because it requires extensive auditing and assurance mechanisms on the part of the relay operator. Defenses It seems clear that the above indicates that at minimum relays should protect against one-time key compromise. Some further thought shows that it is possible to make the APT adversary's task harder as well, albeit with significantly more effort. Let's deal with defending against each vector in turn. Prevent Vector #1 (One-Time Key Theft): Deploy Ephemeral Identity Keys The simplest way to defend against the adversary who attempts to extract relay keys through a reboot is to take advantage of the fact that even node identity keys can be ephemeral, and do not need to persist long term (certainly not past a reboot). This can be achieved with a boot script that wipes your keys (they live in /var/lib/tor/keys) at startup, or by using a ramdisk: http://www.cyberciti.biz/faq/howto-create-linux-ram-disk-filesystem/ Of the two, the ramdisk option is superior, since it will prevent the adversary from easily re-using your old keys after you begin using the new ones. Additionally, ssh server key theft is another one-time vector that can be used to quickly bootstrap into node key theft. For this reason, node admins should always use ssh key auth for tor node administration accounts, since it prevents ssh server key theft from implying continuous server compromise: http://www.gremwell.com/ssh-mitm-public-key-authentication Issues With Ephemeral Identity Keys There are a few issues with deploying ephemeral identity keys. Issues With Ephemeral Identity Keys: Client guard node loss The primary issue with ephemeral identity keys is client Guard node loss. If your relay obtains the Guard flag, you should endeavor to keep it. If you have planned maintenance and controlled reboots, you should copy your identity keys to a safe location prior to reboot so that clients aren't forced to rotate their guards prematurely due to unnecessary rekeying. Issues With Ephemeral Identity Keys: MyFamily The next issue is that identity key rotation makes the use of MyFamily very complicated. For large families, it's nearly impossible to update the MyFamily line of each node instance after every unexpected reboot. We've filed a bug to see if we can find a more convenient way to provide the same feature, but it's not clear that MyFamily is worth maintaining: https://trac.torproject.org/projects/tor/ticket/5565 It is very likely that the security benefit from maintaining MyFamily pales in comparison the gain from deploying ephemeral identity keys, and MyFamily should be abandoned entirely. Issues With Ephemeral Identity Keys: Tor Weather The final issue with ephemeral identity keys is that node monitoring mechanisms such as Tor Weather become difficult to use in the face of rotating keys. We've filed this bug to improve Weather's subscription mechanisms: https://trac.torproject.org/projects/tor/ticket/5564 Preventing Vector #2: Isolation Hardening and Readonly Runtime Once one-time key theft has been dealt with, you can begin to consider how to deal with the Advanced Persistent Threat. The effort required to defend against this adversary is considerable, and it is not expected that all operators will devote the effort to do so. To limit scope, we are not going to deal with the daemon compromise vector; for that see your OS least-privilege mechanisms (such as SElinux, AppArmor, Grsec RBAC, Seatbelt, etc). Instead, we will deal with how you can attempt to protect your identity keys once an adversary already has root access. If you are serious about defending against this adversary, the first thing you will want to do is disable access to the 'ptrace' system call from userland, which allows easy key theft using debugging tools. Note that all current built-in kernel mechanisms to do this still allow root users to use ptrace on arbitrary processes. In order to disable ptrace for root users, you need to load a kernel module to patch the syscall table to remove access to the syscall itself. Two options for this are: https://gist.github.com/1216637 http://people.baicom.com/~agramajo/misc/no-ptrace.c Once access to the ptrace system call is removed, you need to disable module loading to prevent it from being restored. On Linux, this is accomplished via 'sysctl kernel.modules_disabled=1'. You should perform this operation as early in the boot process as possible. One technique that works on Redhat-based systems is to place a shell script in /etc/rc.modules to load the modules you need for operation, insert the ptrace module, and then issue the sysctl to disable further module loading. Redhat-derivatives launch /etc/rc.modules first thing at the top of /etc/rc.sysinit. After that comes ensuring runtime integrity. There are several ways to achieve this, but most are easily subverted by an attacker with direct access to the hardware. The most robust approach seems to be to create a small encrypted loopback filesystem that contains all of the libraries required to run the 'tor' process as well as all of the requisite configuration files. Requisite libraries can be determined via 'ldd /usr/bin/tor'. The encrypted loopback filesystem doesn't need to be more than ~25M in size, but you will also need an auxillary var loopback that needs to be a hundred megs or so. Here are the commands for creating the root loopback filesystem: dd if=/dev/urandom of=./tor-root.img bs=1k count=25k losetup /dev/loop1 ./tor-root.img cryptsetup luksFormat /dev/loop1 cryptsetup luksOpen /dev/loop1 tor-root mkfs.ext4 /dev/mapper/tor-root Once this encrypted loop is created such that it can run your relay's Tor processes, you should take the sha1sum of the file and store it offsite. When you use this loopback, you will mount it readonly, and mount an unencrypted var directory inside of it, and a ramdisk for your keys inside of that: dd if=/dev/urandom of=./tor-var.img bs=1k count=200k losetup /dev/loop2 ./tor-var.img mkfs.ext4 /dev/loop2 mount /dev/mapper/tor-root /mnt/tor-root -o ro mount /dev/loop2 /mnt/tor-root/var mkfs -q /dev/ram1 128 mount /dev/ram1 /mnt/tor-root/var/lib/tor/keys cd /mnt/tor-root/ chroot . start_tor.sh Once you start your tor process(es), you will want to copy your identity key offsite, and then remove it. Tor does not need it to remain on disk after startup, and removing it ensures that an attacker must deploy a kernel exploit to obtain it from memory. While you should not re-use the identity key after unexplained reboots, you may want to retain a copy for planned reboots and tor maintenance. scp /mnt/tor-root/var/lib/tor/keys/secret_id_key offsite_backup:/mnt/usb/tor_key rm /mnt/tor-root/var/lib/tor/keys/secret_id_key Upon suspicious reboots, you can verify the integrity of your tor image by simply calculating the sha1sum (perhaps copying the image offsite first). You do not need to do anything special with the var loopback. These steps should prevent even adversaries who compromise the root account on your system (by rebooting it, for example) from obtaining your identity keys directly, forcing them to resort to kernel exploits and memory gymnastics in order to do so. Don't forget to periodically update the libraries stored on your loopback root using a trusted offsite source, as they won't receive security updates from your distribution. One alternative to make your loopback fs creation, tor startup, and maintenance process simpler is to statically compile your image's tor binary on an offsite, trusted computer. If you do this, you should no longer need to bother with chrooting your tor processes or copying libraries around. However, it still does not save you from the need to recompile that binary whenever there is a security update to the underlying libraries, and it may come at a cost of exploit resistance due to the loss of per-library ASLR. Ok, that's it. What do people think? Personally, I think that if we can require a kernel exploit and/or weird memory gymnastics for key compromise, that would be a *huge* improvement. Do the above recommendations actually accomplish that? If so, should we work on providing scripts to make the loopback filesystem creation process easier, and/or provide loopback images themselves? Even the APT defenses end up not working out, I would sleep a lot better at night if most relays deployed only the defenses to one-time key theft... Thoughts on that? -- Mike Perry

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Arm Release 1.4.5
by Damian Johnson 29 Apr '12

29 Apr '12

Hi all. A new release of arm [1] is now available which includes numerous fixes of mounting importance [2]. In particular this corrects several issues around arm's connection panel, terminal glitches due to disruption of the curses module by readline [3], and incompatibility with tor's new development releases [4][5]. This release does not include any new features, nor are any planned in the near future. Most of my attention is going to stem right now [6][7], and my next foray into arm will be to work with Ravi to migrate it to the new library this summer [8]. That said, if you encounter any problems then let me know! -Damian [1] http://www.atagar.com/arm/ [2] http://www.atagar.com/arm/releaseNotes.php [3] https://gitweb.torproject.org/arm.git/commitdiff/b86e5bf [4] https://lists.torproject.org/pipermail/tor-talk/2012-April/023961.html [5] https://trac.torproject.org/projects/tor/ticket/3313 [6] https://gitweb.torproject.org/stem.git [7] https://trac.torproject.org/projects/tor/wiki/doc/stem [8] https://www.torproject.org/about/gsocProposal/gsoc12-proposal-stemImproveme…

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"who has used my bridge" in vidalia bridge bundle?
by eliaz 24 Apr '12

24 Apr '12

After running bridge relays in the TBB for a long time I now get "who has used my bridge" results quite quickly after restarts. But in the stable bridge bundle, this function seems not to work - I've had the bundle running for well over a day and am still getting the msg "no clients have used your relay recently," while the Bandwidth Usage is sailing away to beat the band. Is there a way to fix this? - eli ---- gpg: 0xC3E1E38D

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What to do about icecat.biz abuse complaints?
by Steve Snyder 14 Apr '12

14 Apr '12

I often get abuse complaints from icecat,biz saying that a "RIP attempt" was seen from the IP address of my exit node. Apparently this involves too many connections in a given period of time. I've tried to contact them but get no answer from the e-mail address included in the abuse reports. The Administrator listed in the icecat.biz whois says he just provides the network and can't provide any info about the company or who to contact within it. The abuse reports each say that my IP address will be blacklisted for a week. Fine with me. I'd just as soon they blacklist it forever but as they are unresponsive to e-mail communication I can't tell them that. Short of turning my exit node into a middle node, what can I do about these frequent abuse reports?

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Mystery of bridge utilization
by Steve Snyder 02 Apr '12

02 Apr '12

I've got 2 bridges, with 1 IP address in each of 2 servers in the same geographical area. The IP addresses are not consecutive. Both servers have the same hardware and software configurations. Both were established in mid-January and (excepting a few brief periods of down time) have been running since then. So why then in March did one server handle 200GB of traffic while the other handled only 2GB? (Yes, a x100 difference.) Also: is there something I can do to make my under-utilized bridge more attractive to the Bridge Authorities? Thanks.

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hardware accel option in tor alpha
by Sebastian Urbach 01 Apr '12

01 Apr '12

Hi, I want to use the "hardware accel" feature with the actual tor alpha version 0.2.3.12-alpha1. My CPUs support the Intel AES NI function and the kernel module is enabled and running well. Im running OpenSSL 1.0.1, the debian dev told me that there is no dynamic loadable aes ni shipped though its supporting th function. Im pretty confused about the options int the torrc right now. I have enabled "hardware accel" but did not define any dynamic loadable engine anymore because there is no one according to the debian dev and also the output from "openssl engine". The debug log does not show any enabled aes / evp functions what so ever. Im stuck right now, does anybody have some advice, woudl be awesome ;-) ? Thanks -- Mit freundlichen Grüßen / Yours sincerely Sebastian Urbach -------------------------------------------------------- Religion is something left over from the infancy of our intelligence, it will fade away as we adopt reason and science as our guidelines. -------------------------------------------------------- Bertrand Arthur William Russell (1872-1970), British philosopher, logician, mathematician, historian, and social critic.

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