The reason the "streams problem" occurs is due to the complicated
interaction between Tor's congestion control and libevent. At some point
during the experiment, the circuit window is exhausted, which blocks all
edge streams. When a circuit level sendme is received at Exit, it
resumes edge reading by looping over linked list of edge streams, and
calling connection_start_reading() to inform libevent to resume reading.
When the streams are activated again, Tor gets the chance to service the
first three streams activated before the circuit window is exhausted
again, which causes all streams to be blocked again. As an experiment,
we reversed the order in which the streams are activated, and indeed the
first three streams, rather than the last three, got service, while the
others starved.
Our solution is to change the order in which streams are activated. We
choose a random edge connection from the linked list, and then we
activate streams starting from that chosen stream. When we reach the end
of the list, then we continue from the head of the list until our chosen
stream (treating the linked list as a circular linked list). It would
probably be better to actually remember which streams have received
service recently, but this way is simple and effective.
Sebastian notes (and I think correctly) that one of our ||s should
have been an &&, which simplifies a boolean expression to decide
whether to replace bridges. I'm also refactoring out the negation at
the start of the expression, to make it more readable.
Pick 5 seconds as the limit. 5 seconds is a compromise here between
making sure the user notices that the bad behaviour is (still) happening
and not spamming their log too much needlessly (the log message is
pretty long). We also keep warning every time if safesocks is
specified, because then the user presumably wants to hear about every
blocked instance.
(This is based on the original patch by Sebastian, then backported to
0.2.2 and with warnings split into their own function.)
Our checks that we don't exceed the 50 KB size limit of extra-info
descriptors apparently failed. This patch fixes these checks and reserves
another 250 bytes for appending the signature. Fixes bug 2183.
Sending a log message to a control port can cause Tor to allocate a buffer,
thereby changing the length of the freelist behind buf_shrink_freelists's back,
thereby causing an assertion to fail.
Fixes bug #1125.
Sending a log message to a control port can cause Tor to allocate a buffer,
thereby changing the length of the freelist behind buf_shrink_freelists's back,
thereby causing an assertion to fail.
Fixes bug #1125.
We would never actually enforce multiplicity rules when parsing
annotations, since the counts array never got entries added to it for
annotations in the token list that got added by earlier calls to
tokenize_string.
Found by piebeer.
We had a spelling discrepancy between the manpage and the source code
for some option. Resolve these in favor of the manpage, because it
makes more sense (for example, HTTP should be capitalized).
The code that makes use of the RunTesting option is #if 0, so setting
this option has no effect. Mark the option as obsolete for now, so that
Tor doesn't list it as an available option erroneously.
In the case where old_router == NULL but sdmap has an entry for the
router, we can currently safely infer that the old_router was not a
bridge. Add an assert to ensure that this remains true, and fix the
logic not to die with the tor_assert(old_router) call.
In a2bb0bf we started using a separate client identity key. When we are
in "public server mode" (that means not a bridge) we will use the same
key. Reusing the key without doing the proper refcounting leads to a
segfault on cleanup during shutdown. Fix that.
Also introduce an assert that triggers if our refcount falls below 0.
That should never happen.
We now require that:
- Only actual servers should ever call get_server_identity_key
- If you're being a client or bridge, the client and server keys should
differ.
- If you're being a public relay, the client and server keys
should be the same.
When intro->extend_info is created for an introduction point, it
only starts out with a nickname, not necessarily an identity digest.
Thus, doing router_get_by_digest isn't necessarily safe.
https://trac.torproject.org/projects/tor/ticket/1859
Use router_get_by_digest() instead of router_get_by_hexdigest()
in circuit_discard_optional_exit_enclaves() and
rend_client_get_random_intro(), per Nick's comments.
Using router_get_by_digest() in rend_client_get_random_intro() will
break hidden services published by Tor versions pre 0.1.2.18 and
0.2.07-alpha as they only publish by nickname. This is acceptable
however as these versions only publish to authority tor26 and
don't work for versions in the 0.2.2.x series anyway.
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.
* Make tor_tls_context_new internal to tortls.c, and return the new
tor_tls_context_t from it.
* Add a public tor_tls_context_init wrapper function to replace it.
When picking bridges (or other nodes without a consensus entry (and
thus no bandwidth weights)) we shouldn't just trust the node's
descriptor. So far we believed anything between 0 and 10MB/s, where 0
would mean that a node doesn't get any use from use unless it is our
only one, and 10MB/s would be a quite siginficant weight. To make this
situation better, we now believe weights in the range from 20kB/s to
100kB/s. This should allow new bridges to get use more quickly, and
means that it will be harder for bridges to see almost all our traffic.
In the first 100 circuits, our timeout_ms and close_ms
are the same. So we shouldn't transition circuits to purpose
CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT, since they will just timeout again
next time we check.
We really should ignore any timeouts that have *no* network activity for their
entire measured lifetime, now that we have the 95th percentile measurement
changes. Usually this is up to a minute, even on fast connections.
If we really want all this complexity for these stages here, we need to handle
it better for people with large timeouts. It should probably go away, though.
Rechecking the timeout condition was foolish, because it is checked on the
same codepath. It was also wrong, because we didn't round.
Also, the liveness check itself should be <, and not <=, because we only have
1 second resolution.
Specifically, a circ attempt that we'd launched while the network was
down could timeout after we've marked our entrynodes up, marking them
back down again. The fix is to annotate as bad the OR conns that were
around before we did the retry, so if a circuit that's attached to them
times out we don't do anything about it.
