Support for log filter policy hooks

This adds a "policy" hook into the logging framework's streams and
filters to replace the existing log filter predicates. The hook
signature is as follows:

    hook(rec: any, id: Log::ID, filter: Log::Filter);

The logging manager invokes hooks on each log record. Hooks can veto
log records via a break, and modify them if necessary. Log filters
inherit the stream-level hook, but can override or remove the hook as
needed.

The distribution's existing log streams now come with pre-defined
hooks that users can add handlers to. Their name is standardized as
"log_policy" by convention, with additional suffixes when a module
provides multiple streams. The following adds a handler to the Conn
module's default log policy hook:

    hook Conn::log_policy(rec: Conn::Info, id: Log::ID, filter: Log::Filter)
            {
            if ( some_veto_reason(rec) )
                break;
            }

By default, this handler will get invoked for any log filter
associated with the Conn::LOG stream.

The existing predicates are deprecated for removal in 4.1 but continue
to work.
This commit is contained in:
Christian Kreibich 2020-09-21 16:09:36 -07:00
parent c8545c85d8
commit 1bd658da8f
61 changed files with 289 additions and 85 deletions

View file

@ -9,6 +9,9 @@ export {
## The SSH protocol logging stream identifier.
redef enum Log::ID += { LOG };
## A default logging policy hook for the stream.
global log_policy: Log::PolicyHook;
## The record type which contains the fields of the SSH log.
type Info: record {
## Time when the SSH connection began.
@ -143,7 +146,7 @@ redef likely_server_ports += { ports };
event zeek_init() &priority=5
{
Analyzer::register_for_ports(Analyzer::ANALYZER_SSH, ports);
Log::create_stream(SSH::LOG, [$columns=Info, $ev=log_ssh, $path="ssh"]);
Log::create_stream(SSH::LOG, [$columns=Info, $ev=log_ssh, $path="ssh", $policy=log_policy]);
}
function set_session(c: connection)