142 lines
5.1 KiB
Markdown
142 lines
5.1 KiB
Markdown
# Leakybuckets
|
|
|
|
## Bucket concepts
|
|
|
|
Leakybucket is used for decision making. Under certain conditions
|
|
enriched events are poured in these buckets. When these buckets are
|
|
full, we raise a new event. After this event is raised the bucket is
|
|
destroyed. There are many types of buckets, and we welcome any new
|
|
useful design of buckets.
|
|
|
|
Usually the bucket configuration generates the creation of many
|
|
buckets. They are differenciated by a field called stackkey. When two
|
|
events arrives with the same stackkey they go in the same matching
|
|
bucket.
|
|
|
|
The very purpose of these buckets is to detect clients that exceed a
|
|
certain rate of attemps to do something (ssh connection, http
|
|
authentication failure, etc...). Thus, the most use stackkey field is
|
|
often the source_ip.
|
|
|
|
## Standard leaky buckets
|
|
|
|
Default buckets have two main configuration options:
|
|
* capacity: number of events the bucket can hold. When the capacity
|
|
is reached and a new event is poured, a new event is raised. We
|
|
call this type of event overflow. This is an int.
|
|
* leakspeed: duration needed for an event to leak. When an event
|
|
leaks, it disappear from the bucket.
|
|
|
|
## Trigger
|
|
|
|
It's a special type of bucket with a zero capacity. Thus, when an
|
|
event is poured in a trigger, it always raises an overflow.
|
|
|
|
## Uniq
|
|
|
|
It's a bucket working as the standard leaky bucket except for one
|
|
thing: a filter returns a property for each event and only one
|
|
occurrence of this property is allowed in the bucket, thus the bucket
|
|
is called uniq.
|
|
|
|
## Counter
|
|
|
|
It's a special type of bucket with an infinite capacity and an
|
|
infinite leakspeed (it never overflows, neither leaks). Nevertheless,
|
|
the event is raised after a fixed duration. The option is called
|
|
duration.
|
|
|
|
## Available configuration options for buckets
|
|
|
|
### Fields for standard buckets
|
|
|
|
* type: mandatory field. Must be one of "leaky", "trigger", "uniq" or
|
|
"counter"
|
|
* name: mandatory field, but the value is totally open. Nevertheless
|
|
this value will tag the events raised by the bucket.
|
|
* filter: mandatory field. It's a filter that is run when the decision
|
|
to make an event match the bucket or not. The filter have to return
|
|
a boolean. As a filter implementation we use
|
|
https://github.com/antonmedv/expr
|
|
* capacity: [mandatory for now, shouldn't be mandatory in the final
|
|
version] it's the size of the bucket. When pouring in a bucket
|
|
already with size events, it overflows.
|
|
* leakspeed: leakspeed is a time duration (has to be parseable by
|
|
https://golang.org/pkg/time/#ParseDuration). After each interval an
|
|
event is leaked from the bucket.
|
|
* stackkey: mandatory field. This field is used to differentiate on
|
|
which bucket ongoing events will be poured. When an unknown stackkey
|
|
is seen in an event a new bucket is created.
|
|
* on_overflow: optional field, that tells the what to do when the
|
|
bucket is returning the overflow event. As of today, the possibility
|
|
are these: "ban,1h", "Reprocess", "Delete".
|
|
Reprocess is used to send the raised event back in the event pool to
|
|
be matched agains buckets
|
|
|
|
### Fields for special buckets
|
|
|
|
#### Uniq
|
|
|
|
Uniq has an extra field uniq_filter which is too use the filter
|
|
implementation from https://github.com/antonmedv/expr. The filter must
|
|
return a string. All strins returned by this filter in the same
|
|
buckets have to be different. Thus, if a string is seen twice it is
|
|
dismissed.
|
|
|
|
#### Trigger
|
|
|
|
Capacity and leakspeed are not relevant for this kind of bucket.
|
|
|
|
#### Counter
|
|
|
|
It's a special kind of bucket that raise an event and is destroyed
|
|
after a fixed duration. The configuration field used is duration and
|
|
must be parseable by https://golang.org/pkg/time/#ParseDuration.
|
|
Nevertheless, this kind of bucket is often used with an infinite
|
|
leakspeed and an infinite capacity [capacity set to -1 for now].
|
|
|
|
|
|
## Add examples here
|
|
|
|
```
|
|
# ssh bruteforce
|
|
- type: leaky
|
|
name: ssh_bruteforce
|
|
filter: "Meta.log_type == 'ssh_failed-auth'"
|
|
leakspeed: "10s"
|
|
capacity: 5
|
|
stackkey: "source_ip"
|
|
on_overflow: ban,1h
|
|
|
|
# reporting of src_ip,dest_port seen
|
|
- type: counter
|
|
name: counter
|
|
filter: "Meta.service == 'tcp' && Event.new_connection == 'true'"
|
|
distinct: "Meta.source_ip + ':' + Meta.dest_port"
|
|
duration: 5m
|
|
capacity: -1
|
|
|
|
- type: trigger
|
|
name: "New connection"
|
|
filter: "Meta.service == 'tcp' && Event.new_connection == 'true'"
|
|
on_overflow: Reprocess
|
|
```
|
|
|
|
# Note on leakybuckets implementation
|
|
|
|
[This is not dry enough to have many details here, but:]
|
|
|
|
The bucket code is triggered by `InfiniBucketify` in main.go.
|
|
There's one struct called buckets which is for now a
|
|
`map[string]interface{}` that holds all buckets. The key of this map
|
|
is derivated from the filter configured for the bucket and its
|
|
stackkey. This looks like complicated, but in fact it allows us to use
|
|
only one structs. This is done in buckets.go.
|
|
|
|
On top of that the implementation define only the standard leaky
|
|
bucket. A goroutine is launched for every buckets (bucket.go). This
|
|
goroutine manages the life of the bucket.
|
|
|
|
For special buckets, hooks are defined at initialization time in
|
|
manager.go. Hooks are called when relevant by the bucket gorourine
|
|
when events are poured and/or when bucket overflows. |