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2d8f7a8391
https://trac.torproject.org/projects/tor/ticket/1859 There are two problems in this bug: 1. When an OP makes a .exit request specifying itself as the exit, and the exit is not yet listed, Tor gets all the routerinfos needed for the circuit but discovers in circuit_is_acceptable() that its own routerinfo is not in the routerdigest list and cannot be used. Tor then gets locked in a cycle of repeating these two steps. When gathering the routerinfos for a circuit, specifically when the exit has been chosen by .exit notation, Tor needs to apply the same rules it uses later on when deciding if it can build a circuit with those routerinfos. 2. A different bug arises in the above situation when the Tor instance's routerinfo *is* listed in the routerlist, it shares its nickname with a number of other Tor nodes, and it does not have 'Named' rights to its nickname. So for example, if (i) there are five nodes named Bob in the network, (ii) I am running one of them but am flagged as 'Unnamed' because someone else claimed the 'Bob' nickname first, and (iii) I run my Tor as both client and exit the following can happen to me: - I go to www.evil.com - I click on a link www.evil.com.bob.exit - My request will exit through my own Tor node rather than the 'Named' node Bob or any of the others. - www.evil.com now knows I am actually browsing from the same computer that is running my 'Bob' node So to solve both issues we need to ensure: - When fulfilling a .exit request we only choose a routerinfo if it exists in the routerlist, even when that routerinfo is ours. - When getting a router by nickname we only return our own router information if it is not going to be used for building a circuit. We ensure this by removing the special treatment afforded our own router in router_get_by_nickname(). This means the function will only return the routerinfo of our own router if it is in the routerlist built from authority info and has a unique nickname or is bound to a non-unique nickname. There are some uses of router_get_by_nickname() where we are looking for the router by name because of a configuration directive, specifically local declaration of NodeFamilies and EntryNodes and other routers' declaration of MyFamily. In these cases it is not at first clear if we need to continue returning our own routerinfo even if our router is not listed and/or has a non-unique nickname with the Unnamed flag. The patch treats each of these cases as follows: Other Routers' Declaration of MyFamily This happens in routerlist_add_family(). If another router declares our router in its family and our router has the Unnamed flag or is not in the routerlist yet, should we take advantage of the fact that we know our own routerinfo to add us in anyway? This patch says 'no, treat our own router just like any other'. This is a safe choice because it ensures our client has the same view of the network as other clients. We also have no good way of knowing if our router is Named or not independently of the authorities, so we have to rely on them in this. Local declaration of NodeFamilies Again, we have no way of knowing if the declaration 'NodeFamilies Bob,Alice,Ringo' refers to our router Bob or the Named router Bob, so we have to defer to the authorities and treat our own router like any other. Local declaration of NodeFamilies Again, same as above. There's also no good reason we would want our client to choose it's own router as an entry guard if it does not meet the requirements expected of any other router on the network. In order to reduce the possibility of error, the patch also replaces two instances where we were using router_get_by_nickname() with calls to router_get_by_hexdigest() where the identity digest of the router is available. |
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| tor.spec.in | ||
Tor protects your privacy on the internet by hiding the connection
between your Internet address and the services you use. We believe Tor
is reasonably secure, but please ensure you read the instructions and
configure it properly.
To build Tor from source:
./configure && make && make install
Home page:
https://www.torproject.org/
Download new versions:
https://www.torproject.org/download.html
Documentation, including links to installation and setup instructions:
https://www.torproject.org/documentation.html
Making applications work with Tor:
https://wiki.torproject.org/noreply/TheOnionRouter/TorifyHOWTO
Frequently Asked Questions:
https://www.torproject.org/faq.html
https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ