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

@ -18,6 +18,9 @@ export {
## The FTP protocol logging stream identifier.
redef enum Log::ID += { LOG };
## A default logging policy hook for the stream.
global log_policy: Log::PolicyHook;
## List of commands that should have their command/response pairs logged.
option logged_commands = {
"APPE", "DELE", "RETR", "STOR", "STOU", "ACCT", "PORT", "PASV", "EPRT",
@ -61,7 +64,7 @@ redef likely_server_ports += { ports };
event zeek_init() &priority=5
{
Log::create_stream(FTP::LOG, [$columns=Info, $ev=log_ftp, $path="ftp"]);
Log::create_stream(FTP::LOG, [$columns=Info, $ev=log_ftp, $path="ftp", $policy=log_policy]);
Analyzer::register_for_ports(Analyzer::ANALYZER_FTP, ports);
}