Commit Graph

11 Commits

Author SHA1 Message Date
David Goulet
78d6cb5870 dos: We can put less token than the current amount
Becasue the circuit creation burst and rate can change at runtime it is
possible that between two refill of a bucket, we end up setting the bucket
value to less than there currently is.

Fixes #25128

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-02-02 17:04:12 -05:00
teor
a09d5f5735 dos: Make sure cc_stats_refill_bucket can't overflow while calculating
Debug log the elapsed time in cc_stats_refill_bucket

Part of #25094.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-31 09:27:59 -05:00
David Goulet
e58a4fc6cf dos: Make circuit rate limit per second, not tenths anymore
Because this touches too many commits at once, it is made into one single
commit.

Remove the use of "tenths" for the circuit rate to simplify things. We can
only refill the buckets at best once every second because of the use of
approx_time() and our token system is set to be 1 token = 1 circuit so make
the rate a flat integer of circuit per second.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:16 -05:00
David Goulet
82de4ea900 dos: Clear connection tracked flag if geoip entry is removed
Imagine this scenario. We had 10 connections over the 24h lifetime of a geoip
cache entry. The lifetime of the entry has been reached so it is about to get
freed but 2 connections remain for it. After the free, a third connection
comes in thus making us create a new geoip entry for that address matching the
2 previous ones that are still alive. If they end up being closed, we'll have
a concurrent count desynch from what the reality is.

To mitigate this probably very rare scenario in practice, when we free a geoip
entry and it has a concurrent count above 0, we'll go over all connections
matching the address and clear out the tracked flag. So once they are closed,
we don't try to decrement the count.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:16 -05:00
David Goulet
14a8b87852 dos: Add a heartbeat log
Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:16 -05:00
David Goulet
36a0ae151f dos: Add the DoSRefuseSingleHopClientRendezvous option
This option refuses any ESTABLISH_RENDEZVOUS cell arriving from a client
connection. Its default value is "auto" for which we can turn it on or off
with a consensus parameter. Default value is 0.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:16 -05:00
David Goulet
acf7ea77d8 dos: Add the connection DoS mitigation subsystem
Defend against an address that has reached the concurrent connection count
threshold.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:15 -05:00
David Goulet
1bfc91a029 dos: Apply defense for circuit creation DoS
If the client address was detected as malicious, apply a defense which is at
this commit to return a DESTROY cell.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:15 -05:00
David Goulet
97abb3543b dos: Detect circuit creation denial of service
Add a function that notifies the DoS subsystem that a new CREATE cell has
arrived. The statistics are updated accordingly and the IP address can also be
marked as malicious if it is above threshold.

At this commit, no defense is applied, just detection with a circuit creation
token bucket system.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:15 -05:00
David Goulet
c05272783d dos: Track new and closed OR client connections
Implement a basic connection tracking that counts the number of concurrent
connections when they open and close.

This commit also adds the circuit creation mitigation data structure that will
be needed at later commit to keep track of the circuit rate.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:15 -05:00
David Goulet
64149353dd dos: Initial code of Denial of Service mitigation
This commit introduces the src/or/dos.{c|h} files that contains the code for
the Denial of Service mitigation subsystem. It currently contains basic
functions to initialize and free the subsystem. They are used at this commit.

The torrc options and consensus parameters are defined at this commit and
getters are implemented.

Signed-off-by: David Goulet <dgoulet@torproject.org>
2018-01-30 09:18:15 -05:00