A flood of DHCP traffic can result if very large log entries consisting
of many uids and/or msg_types. Such large log entries can disrupt a SIEM
ingestion pipeline. This change forcing a log entry to be written when
the number of uids or the number of msg_Types exceed a certain value.
The values are treated as options for easy configuration.
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.
The field is populated in this order of preference:
(1) Use a client-identifier option sent by client
(2) Use the server's CHADDR field
(3) Use the client's CHADDR field
Case (3) did not exist before this patch.
* "bro_is_terminating" is now "zeek_is_terminating"
* "bro_version" is now "zeek_version"
The old function names still exist for now, but are deprecated.
* All "Broxygen" usages have been replaced in
code, documentation, filenames, etc.
* Sphinx roles/directives like ":bro:see" are now ":zeek:see"
* The "--broxygen" command-line option is now "--zeexygen"
* origin/topic/seth/dhcp-update:
Rework to the DHCP analyzer.
First step of DHCP analyzer rearchitecture.
Add .btest scripts for dhck_ack and dhcp_discover messages verifying that new options are correctly reported in dhcp.log records.
Extend DHCP protocol analyzer with new options.
BIT-1924 #merged
Additional changes:
* Removed known-hosts.bro as the only thing populating its table was
the already-removed known-hosts-and-devices.bro. So a
known_devices.log will no longer be generated.
* In dhcp-options.pac, the process_relay_agent_inf_option had a memleak
and also process_auto_proxy_config_option looked like it accessed one
byte past the end of the available bytestring, so fixed those.
Highlights:
- Reduced all DHCP events into a single dhcp_message event. (removed legacy events since they weren't widely used anyway)
- Support many more DHCP options.
- DHCP log is completely reworked and now represents DHCP sessions
based on the transaction ID (and works on clusters).
- Removed the known-devices-and-hostnames script since it's generally
less relevant now with the updated log.
Old event prototypes have changed and the events are broken right
now and may be removed in favor of the new generic "dhcp_message"
event.
DHCP option parsing is abstracted from the main code base of the
protocol parser and are all now located in their own file.
Documentation, tests, and final code cleanup are still pending.
Add the folowing option types:
- 55 Parameters Request List;
- 58 Renewal time;
- 59 Rebinding time;
- 61 Client Identifier;
- 82 Relay Agent Information.
Extend the following events with new parameters, specifically:
- dhcp_discover exports client identifier and parameters request list;
- dhcp_request exports client_identifier and parameters request list;
- dhcp_ack exports rebinding time, renewal time and list of suboptions value of
dhcp relay agent information option;
- dhcp_inform exports parameters request list.
Add option type specific variables within the scope of DHCP module
(see src/analyzer/protocol/dhcp/types.bif).
Move protocol specific variables "dhcp_msg" and "dhcp_router_list" from scope Global to DHCP::
and adapt inet_net_var in src/NetVar.cc consequently.
Extend src/analyzer/protocols/dhcp/main.bro to handle the new events and to log
dhcp_ack, dhcp_request and dhcp_discover.
Modify scripts/policy/protocols/dhcp/known-devices-and-hostnames.bro to
include new events' variables.
This allows the path for the default filter to be specified explicitly
when creating a stream and reduces the need to rely on the default path
function to magically supply the path.
The default path function is now only used if, when a filter is added to
a stream, it has neither a path nor a path function already.
Adapted the existing Log::create_stream calls to explicitly specify a
path value.
Addresses BIT-1324
These functions are now deprecated in favor of alternative versions that
return a vector of strings rather than a table of strings.
Deprecated functions:
- split: use split_string instead.
- split1: use split_string1 instead.
- split_all: use split_string_all instead.
- split_n: use split_string_n instead.
- cat_string_array: see join_string_vec instead.
- cat_string_array_n: see join_string_vec instead.
- join_string_array: see join_string_vec instead.
- sort_string_array: use sort instead instead.
- find_ip_addresses: use extract_ip_addresses instead.
Changed functions:
- has_valid_octets: uses a string_vec parameter instead of string_array.
Addresses BIT-924, BIT-757.
Add a "broxygen" domain Sphinx extension w/ directives to allow
on-the-fly documentation to be generated w/ Bro and included in files.
This means all autogenerated reST docs are now done by Bro. The odd
CMake/Python glue scipts which used to generate some portions are now
gone. Bro and the Sphinx extension handle checking for outdated docs
themselves.
Parallel builds of `make doc` target should now work (mostly because
I don't think there's any tasks that can be done in parallel anymore).
Overall, this seems to simplify things and make the Broxygen-generated
portions of the documentation visible/traceable from the main Sphinx
source tree. The one odd thing still is that per-script documentation
is rsync'd in to a shadow copy of the Sphinx source tree within the
build dir. This is less elegant than using the new broxygen extension
to make per-script docs, but rsync is faster and simpler. Simpler as in
less code because it seems like, in the best case, I'd need to write a
custom Sphinx Builder to be able to get that to even work.
This cleans up most of the warnings from sphinx (broken :doc: links,
broxygen role misuses, etc.). The remaining ones should be harmless,
but not quick to silence.
I found that the README for each component was a copy from the actual
repo, so I turned those in to symlinks so they don't get out of date.
- Added the known-devices log, and the script to log DHCP hostname per MAC address,
- Added DPD sig,
- Removed some scripts following a discussion with Seth.
