Changes between Version 13 and Version 14 of doc/FAQUnanswered


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Timestamp:
Apr 23, 2010, 4:48:47 AM (9 years ago)
Author:
trac
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  • doc/FAQUnanswered

    v13 v14  
    11This is a list of questions people wish were answered in the [:../TorFAQ]; please add some more.  Better yet answer one and move it to [:../TorFAQ].  Finally you can vote for a question to be answered by incrementing the number after the question in parens.
    22
    3 '''Please do not report bugs here; instead, send email to {{{tor-bugs@freehaven.net}}}.'''  Soon, we'll designate one of the proposed bug servers as official, and you'll be able to post bugs there too.
     3'''Please do not report bugs here; instead, use the [https://bugs.torproject.org/flyspray/index.php?tasks=all&project=4 bug tracker].'''  Soon, we'll designate one of the proposed bug servers as official, and you'll be able to post bugs there too.
     4
     5Also, this is '''not the place''' for random ''it doesn't work'' or ''how do I do foo'' questions.  Support questions are really better asked and answered on the
     6[http://archives.seul.org/or/talk/ or-talk mailinglist].  Also, always a good read: [http://www.catb.org/~esr/faqs/smart-questions.html How To Ask Questions The Smart Way].
    47
    58= Unanswered FAQ Questions =
     9
     101) '''Hidden services are currently very vulnerable to attacks by web hosts who come to suspect a machine in their network is being used for Tor. Since they can power cycle the server in question (and likely blame it on technical difficulties without arousing suspicion) they can make an unambiguous identification of a hidden service host.
     11This could be prevented if the directory servers supported more than one provider for a hidden service and so could direct requests away from a non-responsive server (there may be other solutions). Of course this could also help provide more reliable hidden services in general. Is there any chance of this getting implemented in the near future?'''
     12
     132) '''Why do I keep getting messages telling me that my clock has just jumped ahead and that my circuits will be assumed broken? ''(eg.
     14Oct 02 10:14:53.619 [notice] Your clock just jumped 1056 seconds forward; assuming established circuits no longer work.'') I've got a cron job to sync the time every eight hours and it's never out by more than a second.'''
     15
     16-- On my system, this happens when Vidalia gets into trouble. It seems that when tor and V communicate, tor can wind up waiting for V to respond, or for the V process to be killed.
     17
     18
     193)'''If an attacker has access to past logs of ISP and any given visted site, does the prng of the tor client allow the attacker to guess which circuit it used next?'''
     20
     21Tor uses cryptographically strong random numbers provided by OpenSSL when choosing nodes to use in a circuit. How OpenSSL implements this is operating system specific. If there's a weakness in Tor's method of choosing nodes, it probably isn't in the random number generator.
     22
     23*** Hmm, if the prng is deterministic, and you can narrow one result of calling it by knowing what host was chosen, can you, knowing the algorithm, however good it is, thereby narrow the result of the next call to it?  This question might be a bit ignorant; for example the prng might use other data on the client computer instead of following an algorithm to return the next item.
     24
     25*** Thanks for your comments, BTW, as a lot of us are wondering the answers to these FAQU.
     26
     27*** It has nothing todo with determinism. It is a matter of predictability. Without using real entropy, everything done on conventional computers should be deterministic (try teling that to people who use Windows ;). However, the part that we are interested in is whether someone can predict what Tor is going to next choose.
     28
     29  Cryptographic number generators have the property that they (shouldn't) give up their internal state by their external outputs quickly. So, unless the attacker gets to see a lot of outputs - node choices - without reseeding from real entropy they are pretty much screwed provided the cryptograpphic prng isn't broken.
     30
     31
     32'''Is there a signal i can send the tor client to tell it to switch circuits immediately?'''
     33
     34You can connect to Tor's control port and send "authenticateCRLFsignal newnymCRLF" where CRLF is a carriage return line feed pair.
     35
     36'''Why does Firefox/Privoxy/Tor return Privoxy 404 pages so frequently -- almost every time -- when properly configured, even on sites like google.com?  How to mitigate?  The tor process is running fine.'''
     37(Votes: 2)
     38
     39The first problem is that Privoxy doesn't retry in case of
     40DNS errors. It shows the 404 no such domain message right away.
     41The second problem is that some browser cache Privoxy's error
     42messages and Firefox is one of them.
     43
     44The Privoxy patch described at
     45http://www.fabiankeil.de/sourcecode/privoxy/
     46lets Privoxy retry in case of connection problems
     47and makes sure, the browser doesn't reuse a cached
     48error message.
     49
     50'''For that matter, why is DNS the main failure mode?  Who is timing out and why?  Can Tor (1) change the timeout, (2) deprecate bad servers, or (3) cache DNS locally so it doesn't have to make a long, slow, failure-prone DNS lookup every time?'''
     51
     52You should be sending hostnames to Tor over SOCKS4a or SOCKS5. In that case, the Tor exit node will resolve the hostname before making a connection for you. Unless the exit node is misconfigured, there shouldn't be a problem with DNS resolves timing out.
     53
     54*** Actually, for me this happens most of the time.  I am sending through Privoxy, and tried both sockses.  So why would I be hitting so many exit nodes that FREQUENTLY time out on DNS?  Firefox 1.5, most recent stable Tor.
     55
     56'''Is the reason that gmail rarely works: gmail, tor, privoxy, firefox, your own bandwidth/latency, tor's bw/latency, or some combination?  Is it fixable?'''
     57
     58*** For Gmail for me, it's even worse; I have to try 5 or 6 times before I get a page.
     59
     60-- I know that improvements to DNS handling are due in 1.2.x-final (see bug #364).
     61-- I've just tried a comparison of Firefox loading gmail using privoxy and polipo under Tor 0.1.2.17.  Using privoxy the site did not load, but with polipo it loaded normally.  Can anyone confirm this?
     62
     63'''Why is the argument against more than 3 hops that both-ends attacks are the enemy?  Wouldn't it be better to have more than 3 if the enemy cannot mount a both-ends attack?'''
     64
     65This is two questions, really.
     66
     67To understand it better, think from the perspective of an attacker. They have a choice: they can make a both-ends attack, an attack comprising the hops and both.
     68
     69Now, at this point you need to think what attacker you are trying to defend against. The NSA? Sorry, your screwed - find something else. A big company? Some rogue ISP's? Ok, now that's something that Tor may be able to defend against...
     70
     71Now, what information are you - the attacker - trying to find? Who is talking to who? Content of some transmissions? Both?
     72
     73Well, for finding content of transmissions your best way is to just listen in on some exit nodes.. or create some malicious ones. That's not the attack threat we're trying to defend against, then.
     74For finding who is talking to who? Ok, let's say that's what we're trying to find out.
     75
     76From this perspective, what is needed to mount a both-ends attack? Listening on both ends. If there is some mitigation technique used - like random timing - compromising those both ends could come in handy (at this point, more hops would really be useful). But there isn't - AFAIK - and so we shall suppose that listening on both ends is enough.
     77
     78Now, what is the alternative option? Listening to all the hops AS WELL? Oh dear, that's a little harder.. and what does it bring us? Well, we can get slightly more accurate results - maybe - as we can more closely correlate. This, of course, gets yet better if we compromise some of those hops.
     79
     80The key word here is slightly. Provided the number of hops is a constant - so you can get a reasonably accurate latency estimate - then, over a longer enough period of time, you will be able to correlate and get your results.
     81
     82The key word here is slightly. Provided the number of hops is a constant - so you can get a reasonably accurate latency estimate - then, over a longer enough period of time, you will be able to correlate and get your results.
     83
     84So, yes, the hops will make it slightly more secure. But only slightly. And yes, in some cases, it may be really useful.. but in those cases, you probably should be using something with much stronger anonymity than tor (if someone knowing what your saying is unacceptable, don't use tor.. not, at any rate, on it's own).
     85
     86Now, then, what are the disadvantages to more hops? More bandwidth is used. Latency is increased.
     87
     88Despite this, it's possible that having number of hops as an easily configurable option is not a bad idea... I would guess that there is an excess of middle-man nodes with the recent draconian laws in some parts of the Western oh so free world that make people interested in privacy yet at the same time too scared to actually stick their neck out. In this case, Tor as a network would likely not lose much by doing that.
     89
     90*** I ommitted elaboration of the cases where more hops would be really useful (I think I forgot about it..). These cases are generally when traffic originating from an exit node is wanted to be tracked down and a response can be made quickly, but does not have global observer capabilities. In that case, in order to find the entry node, going through each hop is the only sensible solution in a network with > 50 servers. How much you would gain from extra hops is difficult to answer.. it would depend, I think, on how often circuits rotate and the probability of a hop being out of the grasp of the attackers. Hops are, I think, probably most useful when you - or your data - specifically are being targeted..
     91
     92'''How can I be sure that sending DNS through tor doesn't get spoofed sites?'''
     93
     94Use a method for authenticating the site you want to connect to, such as ensuring an SSL certificate is associated with the domain name and signed by a trusted authority, or verifying an SSH fingerprint out-of-band. Hidden services on Tor are not subject to this problem because their .onion names are self-authenticating as hashes of their public keys.
     95
     96'''How does tor relate to ipv6 and how should typical applications handle ipv6 if they use tor (or tor via Privoxy)?'''
     97
     98Like a dog talking to a quasar... I never was good with similes.
     99
     100Tor carries TCP data (does it? Maybe it just carries some data that is then transported over TCP... I know, for instance, that it also contains IP and port... TCP doesn't) over another layer - currently IPv4. There is work to make Tor work with IPV6, but I am not aware of it being completed.
     101
     102As for how an application would interface with it -- depends. It could use SOCKS; in that case, I think it would have to use SOCKS5 in the event of addressing IPv6 (rather than domains). This could be hacked around by adding a .ipv6 domain - nasty.
     103
     104Privoxy? Same as currently, if it handles it..
     105
     106'''What version of libevent should I be using?'''
     107
     108the latest.  at least 1.1
     109
     110'''How to use Tor in squid? For using Tor on a network using Squid as proxy, for example...'''
     111
     112'''How to use Tor with PF (Packet Filter, found in OpenBSD, NetBSD, DragonFlyBSD and FreeBSD)?'''
     113
     114
     115
     116'''How does Tor work with tabbed browsing, say with Firefox?  Do these requests all follow the same circuit through the Tor network? Can an eavesdropper link a user across all sites opened simultaneously in tabs?'''
     117
     118ver 1.5 Works fine for me, I use No-Script Plugin to help be even safer. Anyone else have a problem with Firefox. Weither the request follow the same curcuit is out of my realm. My surfing experience is good to just fine. ProBastion
     119
     120They will most likely all use the same circuit.  https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#ChangePaths
     121
     122'''When using the Tor/Privoxy configuration, is there an easy way to switch Privoxy between using Tor and using the standard connection (to allow for secure browsing, but also allowing a more direct connection when needed to keep large file transfers from bogging down in Tor)?'''
     123
     124It is possible to do this - however, it involves manually editing the config files for Privoxy, as well as possessing administrative/sudo access for your machine.  Also, once Privoxy is toggled to use a direct connection instead of Tor, your IP will be visible, and Privoxy does n ot provide as much security alone as it does with Tor.
     125
     126If you wish to do this, you will need to make a copy of your Privoxy config file, and comment out the line that causes Privoxy to use the Tor service.  Once you have done this, to switch over, just stop Privoxy, swap the config files, and restart it. You can also automate the process with a very simple shell script - an OSX version including sample config files and a shell script can be found [http://idlecircuits.com/privoxyswitcher.zip here], and the script can be used as an example for other *nix systems.
     127
     128-- In fact, there is no need to stop/restart privoxy. On my system, I have the privoxy config file owned by me, so I can edit it directly. Changing between tor and no-tor is as simple as editing one line.
     129
     130Here's the relevant lines from my privoxy config file:
     131{{{
     132# Tor:
     133#
     134## forward-socks4a / localhost:9050 . 
     135forward-socks4a .onion localhost:9050 .
     136
     137# Do not torrify these (high volume/speed concerns, as well as PhP BBS
     138# systems that consider a changed IP to be a new login.):
     139forward .blood-bowl.net .
     140forward .qemu-forum.ipi.fi .
     141}}}
     142The line with "##" on it is the line to toggle. Remove those to enable tor, add them to disable tor.
     143
     144NB: Every PHP BBS site I've seen will consider you to have logged out and relogged in if your IP address -- as seen by the PHP site -- changes. This means that if tor ever switches circuits and changes exit node, those sites will reset your "unread messages". I have not been able to find a decent way to solve this with TrackHostExits, given that vidalia will overwrite my tor config occasionally (and has no support for adding these internally, so I have two editors trying to change the tor config), the length of time needed to track varies from 30 minutes at some (forced logout after thirty minutes of idle time) to 24 hours at others, dealing with the occasional dead exit node (and then you need to use a new exit node earlier), etc. And, my list of exception sites is currently 26 lines long.
     145
     146'''Tor works fine for POP3 email. But, Whistle-blowers and others who need anonymous
     147political free speech must have reliable SSL smtp email services. How can Tor be used
     148by them when *all* smtp ports, eg, ports 25, 465, 587, etc are now blocked by Tor exit
     149servers? Blocking port 25 helps to defeat spammers, but the smtp SSL/TLS ports are not
     150generally not used by them. Is there any solution with Tor to help the free speech folk
     151and others who need to use secure, reliable smtp services? (votes: 6)'''
     152
     153
     154'''How would one route his email through Tor? My email client (Microsoft Entourage for Mac OS X) has support for SOCKS and TUNNEL proxies, but setting my mail proxy for SOCKS 127.0.0.1 port 9050 or 8118 both produces errors when trying to proxy to SSL SMTP servers via port 25. What am I missing here? Also, setting this proxy doesn't seem to affect incoming POP3 SSL mail, but only affects outgoing mail, albeit without success. A little guidance on how to configure POP3 email clients to use Tor would be much appreciated!'''
     155
     156An attempt to answer the smtp email questions above: The Tor exit servers are likely blocking smtp port 25 in an attempt to stop spammers. Some Tor exit servers *sporadically* allow TLS/SSL smtp over ports 587, 995, etc., but at the present time there is no consistent, reliable policy or service.  (Also your remote email provider must support the use of alternate smtp ports such as those above.) You could use the remailer network but there can be reliability problems with them. Of greater importance is the fact that the remailer network does NOT accept large messages, e.g., scanned documents which can easily be many MB each. If you are a whistleblower or other person who needs to send large documents quickly and anonymously, you have a real problem. At this moment, Tor is not the answer.
     157
     158
     159'''Can Tor be used in a network that has NO DEFAULT ROUTE?  The only access method from this network is to use a traditional proxy.  Is there a way to chain proxies so that TOR requests are sent outbound via the standard proxy? (votes: 1)'''
     160
     161Maybe. If you can get some routes for the Tor servers, then that of course is great.... assuming it must go through the proxy, however, it will need to support sending Tor requests.
     162
     163Assuming it does.. AFAIK, Tor doesn't have built-in support directly for this. So, you'll have to make it look to Tor like it really can connect .. err.. normally.
     164
     165I can see several ways of doing this.
     166
     167You could overload the network commands and have them actually connect to the proxy.. that's easy but a hack.
     168
     169You could try doing something with OpenVPN; personally, I don't have any experience with it... but I'm guessing you could do something neat with it (I remember someone setting up an OpenVPN with Tor being used to route things.. so it supports socks, I think, in some way. In that case, assuming the proxy is socks... all done :) Oterwise, you could write an interface to make it socks).
     170
     171
     172'''Can I help? (votes: 2)'''
     173
     174https://www.torproject.org/volunteer.html
     175
     176'''I've got a bug, now what? (votes: 2)'''
     177
     178The following is a quick summary of the information already in the [:../TorFAQ#ReportBug: FAQ entry].
     179
     1801) Make sure that it is an actual bug with Tor, and not with Privoxy, Vidalia, your OS, etc.
     181
     1822) Check to see if it's an unreported bug (at the [https://bugs.torproject.org/flyspray/index.php?tasks=all&project=4 bug tracker]).
     183
     1842a) If it's already reported, then see if you can add anymore information (in the comments of that bug) that will help the developers duplicate it and/or track it down. (This step requires you to login to your account at flyspray, or to create a new account.)
     185
     1862b) If it's not already reported, then start a new report with as much relevant information as possible. Relevant information includes tor version number, OS used, any relevant lines from the log, and what you were trying to do that caused the bug. (This step requires you to login to your account at flyspray, or to create a new account.) You may want to read [http://www.chiark.greenend.org.uk/~sgtatham/bugs.html How to Report Bugs Effectively].
     187
     188'''How does Tor relate to the Freedom Project? (votes: 1)'''
     189
     190This question is answered in this [:../TorFAQ#ComparisonFreedom: FAQ entry].
     191
     192'''Is there any way to forward an ident response via TOR so that the ident doesn't come back as whatever the end server wants, but your normal response? (votes: 1)'''
     193
     194no.
     195
     196'''How can I uninstall tor? (votes: 1)'''
     197
     198
     199
     200
     201'''I have legal questions about running Tor. Is there anybody I can contact? ( votes: 1)'''
     202
     203Added 2.1.06- The Developers do not provide Legal advice. period! Over at the Tor Legal FAQ there is a written section by EFF lawyers. It aims to give you an overview of some of the legal issues that arise from the Tor project. Read the Disclaimer. The FAQ does provide a dialougue on the legalality & posssible scenarios of operating a Tor Server. They also provide you with contact information to a EFF Lawyer. The Tor FAQ also provides a links to an Abuse FAQ, & Tor Technical FAQ Wiki.  See this address for more information along these lines. https://www.torproject.org/documentation#Support
     204
     205
     206'''If I set up Tor to only act as a router node (reject *:* in torrc) can I still be a contact point for hidden services?'''
     207
     208yes.
     209
     210'''Can anonymity be broken if all Tor servers in the chain are compromised/malicious and so are keeping logs to trace the chain?'''
     211
     212Yes. Indeed, if all the servers in a circuit are compromised then they need not even be communicated with.. the entry node can decipher for all the (possibly even non-existent) nodes. In order to maintain a superficial view of anonymity, it would probably be good to forward it to the exit server however.
     213
     214'''What system resources does a Tor server use?  The FAQ already discusses memory a bit.  What about CPU?  Encryption is CPU-intensive.  Specific question I'd like answered: I'll be setting up a TOR node bandwidth-limited to about 256kbps (half my upstream bandwidth).  Will an old 300MHz G3 Mac easily handle this, or will a faster processor be needed? How 'bout a P90?  Presumably, TOR's disk usage and I/O is minimal.''' (Votes: 1)
     215
     216On older machines, probably reliability (antiques belong in museums) and memory are bigger concerns than processor speed.  You'll want to avoid swap (Tor's disk usage is rather low, but not if you're swapping...), so make sure your memory's adequate (my server runs with a load about half what you mention and, according to ps, is claiming 65MB of RAM).  Based on system loads from newer machines, simple multiplication, and a large margin of error, if you're running an otherwise light load under Linux or BSD, the 300MHz machine should work just fine.
     217
     218== Cannot resolve Foo.onion/Resolve requests to hidden services not allowed ==
     219
     220tor-resolve doesn't seem to work, i get this:
     221{{{connection_ap_handshake_process_socks():  Resolve requests to hidden services not allowed. Failing.}}}
     222from the copy of tor running locally. Please help!
     223
     224(from original questioner: thank you.  I got the mistaken idea that this would work because it is suggested in the 'how to torrify an application' article on this wiki.  It makes more sense now.  Someone who understands better might want to update that document)
     225
     226This question is answered; see [:../TorFAQ#AccessHiddenService: How Do I Access Tor Hidden Servers.]  You get this message when you try to use tor-resolve to resolve the address of a hidden service.  But hidden services are ''hidden'' - they don't *have* an IP address you can use.  Instead, you need to pass the hostnames to Tor directly.
     227
     228== Clock Skew ==
     229My system clock is behind 3 days and I don't have permission to change it.
     230Therefore all the certificates are invalid.
     231Is there a runtime option to skew the time?
     232
     233This should not a problem as of 0.0.9pre6.
     234
     235== Does not connect to port xyz ==
     236All of a sudden, Tor will no longer let me connect to my distant smtp server.
     237The smtp port used is 587 and the connection is SSL. Why is this now happening?
     238
     239587 isn't in the default exit policy. The tor node known as bollox had an
     240accept everything policy so your port 587 requests would have always gone through that.
     241As bollox is no longer around there are no exit nodes that allow port 587. If you
     242control this smtp server, try changing it's port number to something over 1024.
     243
     244== Debian and how to use the package management system ==
     245
     246Also would recomend posting default config files for debian online since apt will not reinstall them if they are removed (/etc/init.d/tor and /etc/torrc for example)
     247
     248'''Answer''': RTFM.  dpkg differentiatea between two states of package removal.
     249There's ''remove'', which will just remove the normal files a package comes with,
     250and there's ''purge'', which will remove configuration files also.  Changes to your
     251configuration (like you removing them) are kept over a remove/install cycle.  If
     252you want them to installed anyway, you should install with
     253{{dpkg --force-confmiss --install tor...deb}}
     254or just purge tor (which will delete /var/lib/tor with its keys if you are a server!), and then install it again.
     255
     256== . ==
    6257After uninstalling everything then reinstalling on debian (using apt-get of course) nothing loads in a browser or anything, eventually a 503 will come up.  Tor is running and privoxy is running, both correctly configured(I think).  If this is a configuration problem, where can I find more information about configuration in debian?
    7258
     259'''Answer''': Duh.  Have you checked out {{{/etc/tor}}}?  What about {{{/var/log/tor}}} and {{{/usr/share/doc/tor}}}?  Why do you think it would be any different than on other OSs?
     260
     261== Privoxy config ==
     262
    8263Similar to above, on brand new install of sarge with tor and privoxy browser, gaim, etc will spend a long time trying to connect eventually failing with 503, if tor is not running a 503 is instant.
    9264
    10 '''Is there a list of default exit ports? Can requests be made to add new default exit ports? If so, to whom? Example: Port 587 [with SSL/TLS] is used by some email providers to allow smtp use by those whose ISPs are blocking smtp port 25.'''
    11 
    12 '''Tor works fine for POP3 email. But, Whistle-blowers and others who need anonymous political free speech must have reliable SSL smtp email services. How can Tor be used by them when *all* smtp ports, eg, ports 25, 465, 587, etc are now blocked by Tor exit servers? Blocking port 25 helps to defeat spammers, but the smtp SSL/TLS ports are not generally not used by them. Is there any solution with Tor to help the free speech folk and others who need to use secure, reliable smtp services?'''
    13 
    14 Can Tor be used in a network that has NO DEFAULT ROUTE?  The only access method from this network is to use a traditional proxy.  Is there a way to chain proxies so that TOR requests are sent outbound via the standard proxy? (votes: 1)
    15 
    16 Can I help? (votes: 2)
    17 
    18 I've got a bug, now what? (votes: 2)
    19 
    20 So I'm totally anonymous if I use Tor? (votes: 1)
    21 
    22 What attacks remain against onion routing? (votes: 1)
    23 
    24 What projects are comparable? (votes: 1)
    25 
    26 How does Tor relate to the Freedom Project? (votes: 1)
    27 
    28 Is there any way to forward an ident response via TOR so that the ident doesn't come back as whatever the end server wants, but your normal response? (votes: 1)
    29 
    30 How can I uninstall tor? (votes: 1)
    31 
    32 I have legal questions about running Tor. Is there anybody I can contact? (votes: 1)
    33 
    34 If I set up Tor to only act as a router node (reject *:* in torrc) can I still be a contact point for hidden services?
    35 
    36 = Answers that won't go on the FAQ =
    37 
    38 '''tor-resolve doesnt seem to work, i get this: 'connection_ap_handshake_process_socks(): Resolve requests to hidden services not allowed. Failing.' from the copy of tor running locally. Please help!'''
    39 
    40 (from original questioner: thank you.  I got the mistaken idea that this would work because it is suggested in the 'how to torrify an application' article on this wiki.  It makes more sense now.  Someone who understands better might want to upate that document)
    41 
    42 This question is answered; see 'How Do I Access Tor Hidden Servers.'  You get this message when you try to use tor-resolve to resolve the address of a hidden service.  But hidden services are '''hidden''' -- they don't *have* an IP address you can use.  Instead, you need to pass the hostnames to Tor directly.
    43 
    44 '''My system clock is behind 3 days and I don't have permission to change it.  Therefore all the certificates are invalid.  Is there a runtime option to skew the time?'''
    45 
    46 This question is not a problem as of 0.0.9pre6.
    47 
    48 '''All of a sudden, Tor will no longer let me connect to my distant smtp server. The smtp
    49 port used is 587 and the connection is SSL. Why is this now happening? '''
    50 
    51 587 isn't in the default exit policy. The tor node known as bollox had an accept everything policy so your port 587 requests would have always gone through that. As bollox is no longer around there are no exit nodes that allow port 587. If you control this smtp server, try changing it's port number to something over 1024.
     265'''Answer''': Privoxy by default does not allow CONNECT to ports other than 443.  Fix your privoxy config.
     266
     267{{{weasel@galaxy:/etc/privoxy$ grep limit.con default.action | grep -v '^#'
     268+limit-connect{1-} \
     269}}}
     270
     271(If someone writes a proper question, this might actually go into the FAQ)
     272
     273== How To Configure One's Web Browser So Tor Is Only Used For Some Sites But Not Others ==
     274'''Question''': Can I configure Tor so it will only use the onion routing network for some sites but not others?
     275
     276'''Answer''': No, Tor itself is all or nothing, a request either goes through it or it does not.
     277
     278For privoxy, however, you can use forward lines to make some hosts use tor, some use the normal system, and others use whatever other proxy you want.
     279{{{
     280forward-socks4a / localhost:9050 .
     281forward-socks4a .onion localhost:9050 .
     282
     283# Do not torrify these (high volume/speed concerns, as well as PhP BBS
     284# systems that consider a changed IP to be a new login.):
     285forward .blood-bowl.net .
     286forward .youtube.com .
     287forward .qemu-forum.ipi.fi .
     288forward .vidalia-project.net .
     289}}}
     290
     291Here is an example. This uses privoxy for all sites (ad filtering, etc), and then specifies that some sites go through tor, and some do not.
     292
     293Privoxy uses the LAST match. So, the first line says "Use Tor by default". It can be turned off. The second line says "Always use Tor for .onion". After that are lines for "Never use Tor for these".
     294
     295Older, wrong information:
     296Privoxy is also all or nothing in the sense that if a request has made it to Privoxy then either Privoxy is set up to go through Tor or it's not, there does not appear to be a way to program Privoxy so it will use Tor for some requests but not others.
     297
     298There is a script for OS X, available [http://idlecircuits.com/privoxyswitcher.zip here], that will make it such that Privoxy never uses Tor but this is an 'all or nothing' mechanism. The script will either start Privoxy such that all requests go through Tor or no requests go through Tor.
     299
     300There is one mechanism that is at least useful for web browsers, it's called a pac file. It was invented by Netscape, the original documentation is available [http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html here], but it is now supported by all major browsers. One can use a pac file to program the browser to use the Privoxy proxy for certain requests but not others. For example, the following pac file will cause all requests to Google or to the special Privoxy configuration addresses to be sent to Privoxy (and hence Tor) but will allow other other requests to go out without Privoxy/Tor being used:
     301
     302{{{
     303function FindProxyForURL(url, host) {
     304        if (shExpMatch(host,"*google.*") ||
     305            shExpMatch(host,"config.privoxy.org") ||
     306            shExpMatch(host,"p.p"))
     307                return "PROXY 127.0.0.1:8118";
     308        return "DIRECT";
     309}
     310}}}
     311
     312To configure Firefox to use a pac file under OS X go to Firefox->preferences->General->Connection Settings...->Automatic proxy configuration URL:. Enter in a URL (you can use file:// to point to a local file) that points to your pac file and click reload.
     313
     314It's probably not a good idea to use pac files with Safari on OS X as its pac file support seems to be more than a little buggy.
     315
     316The pac file solution is far from ideal. It won't apply to non-web access and it runs into problems such as the bad pac file support in Safari. It also is not secure. A malicious website can trivially bypass this mechanism by placing pictures on its website from domains that it controls but are unlikely to be on a 'black list'. Therefore this mechanism is only useful with Websites that are not in and of themselves malicious but rather, due to their nature, can collect substantial amounts of personal information that one would rather not release. A search engine is a classic example. If and when privacy is a critical concern then the only proper course of action is to get rid of the pac file and instead configure all connections to go through privoxy/tor.
     317
     318
     319
     320'''I've been banned as an contributor at Slashdot! I run a Win 2003 server, with a decent pipe. They said that if I blocked them they would let me contribute again. I did an edit on my torrc file by adding a line:
     321
     322reject *:66.35.250.150 (which is Slashdot.com by using an online DNS 'dig' page
     323
     324I add the above right after my default exit. Which was just this:
     325#ExitPolicy accept *:6660-6667,reject *:* # allow irc ports but no more
     326ExitPolicy accept *:119 # accept nntp as well as default exit policy
     327#ExitPolicy reject *:* # middleman only -- no exits allowed
     328reject *:66.35.250.15
     329
     330Is this the way to do this, and just block Slashdot? Any help would be helpful, I've googled, did the torproject.org site, etc. But I'm not real UNIX centric (though thats changing) so just wanted to run it by some community persons. '''
     331
     332
     333Well, you don't appear to allow exits on HTTP ports so I don't know why they blocked you. Fascists? [Ed. Fascists put their belief into the state... I doubt Slashdot does. Really, it's authoritarian]
     334
     335Anyway, you should probably block their IP rather than ports that happen to be theirs ;) (which don't exist - surprised tor let you do that..)
     336
     337To clarify, the syntax is ''ip-address'':''port'', so reject *:66.35.250.15 is blocking all requests to exit port number 66.35.250.15 at all ip addresses. This obviously doesn't make sense. What you want to do is reject 66.35.250.15:* to block all slashdot traffic.
     338
     339Also, the fourth line of this page reads: ''this is '''not the place''' for random it doesn't work or how do I do foo questions.''
     340
     341'''What is the significance of the changes in the Bittorrent Torify HOWTO?'''
     342
     343I noticed I can't connect with btdownloadcurses through proxychains any more. Looking for answers, I went back to the Torify HOWTO and noticed that it had been altered. Where it used to explain about using proxychains to run bittorrent through TOR, which I used successfully for over a year, it now says that Bittorrent "uses a mechanism similar to TOR." That was certainly news to me. How is the generic Bittorrent client technically similar to TOR in any way? I have always heard that the generic Bittorrent client offers almost no anonymity at all. Now I'm reading that Bittorrent and TOR are practically the same thing and it would be redundant to use them together. Seems a bit curious.
     344
     345As a sub-question, let me just ask directly: Is it true that Bittorrent through TOR via proxychains no longer works?
     346
     347Also, the same page now mentions a technique of using Tor to connect to the tracker only, as opposed to the peers, by including the line --tracker-proxy 127.0.0.1:8118: on the command line. However, I see no documentation of this option in the btdownloadcurses client and I find it a bit suspicious that the format of this option uses a hyphen rather than an underscore as all the other command line options that are listed as being compatible with btdownloadcurses use underscores to separate options with two words such as --check_hashes <arg> or --report_hash_failures <arg>. Is that a typo or an undocumented option that just happens to deviate from the naming convention of all the other options?
     348
     349'''How do you start and stop Tor and Privoxy in OS X (Panther) if you did not install the startup script? (needs to be added to installation instructions)'''
     350
     351
     352On my system, the privoxy startup file ultimately runs
     353{{{sudo $INSTALLDIR/privoxy --pidfile $pidfile }}}
     354
     355with INSTALLDIR being where you installed it, and pidfile being a filename that will hold the process ID.
     356
     357Tor can be started as a normal user -- just run the tor program. On my system, it runs as
     358{{{/usr/bin/tor ControlPort 9051}}}
     359
     360Note that Vidalia is responsible for starting tor, normally.
     361
     362'''How do you configure the proxy if you are using Tor and Privoxy in OS X (Panther) with a router's firewall and the built-in OS X firewall, e.g. when using Wi-fi to connect to wireless router?  (needs to be added to installation instructions)'''
     363
     364I'm not sure that this is OS X specific. For any firewall, you need to add two incoming ports, 9001 and 9030 by default, to the list of approved ports.
     365
     366For Mac OS X, go to control panel, sharing, firewall, and then click "new" twice. The first one is port 9001, label "Tor Server", the second is port 9030, label "Tor Directory Mirror". Both of these are TCP ports, and the "port name" field should be "other".
     367
     368If you have BOTH the Os X firewall, and the router firewall, then you also need to open those ports on the router. Details are router specific.
     369
     370'''What to do (troubleshooting) if browsing slows to a crawl with Tor and Privoxy running in OS X?'''
     371
     372Somebody proposed the following solution, which ''should not be used'' as it will break Tor for everyone else.
     373
     374{{{CircuitBuildTimeout 6
     375NewCircuitPeriod 3
     376ExcludeNodes charlesbabbage,tutzing,TFTor,freetux4ever
     377LongLivedPorts 80,23,21,22,706,1863,5050,5190,5222,5223,6667,8300,8888}}}
     378
     379CircuitBuildTimeout causes the client to drop an uncompleted circuit after 6 seconds; it will cause your tor to build circuits more aggressively than other nodes.  The default value is 60.
     380
     381Finally, port 80 is added to the "long lived ports" list. This will overload long lived ports, making tor unusable for people who need to use ssh over tor.
     382
     383
     384'''I am running a Tor server on one computer on a network. Can I stop the other PCs on the same network from being k-lined on QuakeNet?'''
     385
     386
     387'''Would it make sense to support binding to multiple ports in Tor server (e.g. to bind to ports 443, 22, 5190 etc.) for clients behind _really_ restrictive firewalls? If this was implemented one day, maybe you could also support binding to multiple specific IP addresses on multihomed servers?'''
     388
     389The changelog indicates that this has been possible since "version 0.0.7pre1 - 2004-06-02":
     390''Allow multiple instances of each BindAddress config option, so you can bind to multiple interfaces if you want.''
     391
     392The [https://www.torproject.org/tor-manual.html.en manual] says this about the ''ORListenAddress'' configuration option:
     393''... This directive can be specified multiple times to bind to multiple addresses/ports.''
     394
     395It also says this about the ''DIRListenAddress'' configuration option:
     396''... This directive can be specified multiple times to bind to multiple addresses/ports.''
     397
     398'''What data does tor store on the hard disk when used as a relay?'''
     399
     400----
     401CategoryHomepage