From aa2fbc2d5324defee09981230468d5b685c4268f Mon Sep 17 00:00:00 2001
From: Josh Brower <Josh@Defensivedepth.com>
Date: Tue, 28 Jan 2020 21:44:42 -0500
Subject: [PATCH] Zeek - Initial BPF support

---
 salt/bro/files/local.bro                  |   3 +
 salt/bro/init.sls                         |  34 ++++++-
 salt/bro/policy/securityonion/bpfconf.bro | 106 ++++++++++++++++++++++
 3 files changed, 141 insertions(+), 2 deletions(-)
 create mode 100644 salt/bro/policy/securityonion/bpfconf.bro

diff --git a/salt/bro/files/local.bro b/salt/bro/files/local.bro
index 42112f7ee..afe4b94ca 100644
--- a/salt/bro/files/local.bro
+++ b/salt/bro/files/local.bro
@@ -102,6 +102,9 @@
 # is currently considered a preview and therefore not loaded by default.
 @load base/protocols/smb
 
+# BPF Configuration
+@load securityonion/bpfconf
+
 # Add the interface to the log event
 #@load securityonion/add-interface-to-logs.bro
 
diff --git a/salt/bro/init.sls b/salt/bro/init.sls
index 6a972cbe7..8f36be420 100644
--- a/salt/bro/init.sls
+++ b/salt/bro/init.sls
@@ -1,3 +1,7 @@
+{% set interface = salt['pillar.get']('sensor:interface', 'bond0') %}
+{% set BPF_ZEEK = salt['pillar.get']('zeek:bpf') %}
+{% set BPF_STATUS = 0  %}
+
 # Bro Salt State
 # Add Bro group
 brogroup:
@@ -103,6 +107,32 @@ zeekcleanscript:
     - month: '*'
     - dayweek: '*'
 
+# BPF compilation and configuration
+{% if BPF_ZEEK %}
+   {% set BPF_CALC = salt['cmd.script']('/usr/sbin/so-bpf-compile', interface + ' ' + BPF_ZEEK|join(" ")  ) %}
+   {% if BPF_CALC['stderr'] == "" %}
+       {% set BPF_STATUS = 1  %}
+  {% else  %}
+zeekbpfcompilationfailure:
+  test.configurable_test_state:
+   - changes: False
+   - result: False
+   - comment: "BPF Syntax Error - Discarding Specified BPF"
+   {% endif %}
+{% endif %}
+
+zeekbpf:
+  file.managed:
+    - name: /opt/so/conf/bro/bpf
+    - user: 940
+    - group: 940
+   {% if BPF_STATUS %}
+    - contents_pillar: zeek:bpf
+   {% else %}
+    - contents:
+      - "ip or not ip"
+   {% endif %}
+
 # Sync local.bro
 {% if salt['pillar.get']('static:broversion', '') == 'COMMUNITY' %}
 localbrosync:
@@ -163,6 +193,7 @@ so-bro:
       - /nsm/bro/extracted:/nsm/bro/extracted:rw
       - /opt/so/conf/bro/local.bro:/opt/bro/share/bro/site/local.bro:ro
       - /opt/so/conf/bro/node.cfg:/opt/bro/etc/node.cfg:ro
+      - /opt/so/conf/bro/bpf:/opt/bro/share/bro/site/bpf:ro
       - /opt/so/conf/bro/policy/securityonion:/opt/bro/share/bro/policy/securityonion:ro
       - /opt/so/conf/bro/policy/custom:/opt/bro/share/bro/policy/custom:ro
       - /opt/so/conf/bro/policy/intel:/opt/bro/share/bro/policy/intel:rw
@@ -171,6 +202,5 @@ so-bro:
       - file: /opt/so/conf/bro/local.bro
       - file: /opt/so/conf/bro/node.cfg
       - file: /opt/so/conf/bro/policy
-
-
+      - file: /opt/so/conf/bro/bpf
 {% endif %}
diff --git a/salt/bro/policy/securityonion/bpfconf.bro b/salt/bro/policy/securityonion/bpfconf.bro
new file mode 100644
index 000000000..595aef8f2
--- /dev/null
+++ b/salt/bro/policy/securityonion/bpfconf.bro
@@ -0,0 +1,106 @@
+##! This script is to support the bpf.conf file like other network monitoring tools use.
+##! Please don't try to learn from this script right now, there are a large number of
+##! hacks in it to work around bugs discovered in Bro.
+
+@load base/frameworks/notice
+
+module BPFConf;
+
+export {
+	## The file that is watched on disk for BPF filter changes.
+	## Two templated variables are available; "sensorname" and "interface".
+	## They can be used by surrounding the term by doubled curly braces.
+	const filename = "/opt/bro/share/bro/site/bpf" &redef;
+
+	redef enum Notice::Type += { 
+		## Invalid filter notice.
+		InvalidFilter
+	};
+}
+
+global filter_parts: vector of string = vector();
+global current_filter_filename = "";
+
+type FilterLine: record {
+	s: string;
+};
+
+redef enum PcapFilterID += {
+	BPFConfPcapFilter,
+};
+
+event BPFConf::line(description: Input::EventDescription, tpe: Input::Event, s: string)
+	{
+	local part = sub(s, /[[:blank:]]*#.*$/, "");
+
+	# We don't want any blank parts.
+	if ( part != "" )
+		filter_parts[|filter_parts|] = part;
+	}
+
+event Input::end_of_data(name: string, source:string)
+	{
+	if ( name == "bpfconf" )
+		{
+		local filter = join_string_vec(filter_parts, " ");
+		capture_filters["bpf.conf"] = filter;
+		if ( Pcap::precompile_pcap_filter(BPFConfPcapFilter, filter) )
+			{
+			PacketFilter::install();
+			}
+		else
+			{
+			NOTICE([$note=InvalidFilter,
+			        $msg=fmt("Compiling packet filter from %s failed", filename),
+			        $sub=filter]);
+			}
+
+		filter_parts=vector();
+		}
+	}
+
+
+function add_filter_file()
+	{
+	local real_filter_filename = BPFConf::filename;
+
+	# Support the interface template value.
+	#if ( SecurityOnion::sensorname != "" )
+	#	real_filter_filename = gsub(real_filter_filename, /\{\{sensorname\}\}/, SecurityOnion::sensorname);
+
+	# Support the interface template value.
+	#if ( SecurityOnion::interface != "" )
+	#	real_filter_filename = gsub(real_filter_filename, /\{\{interface\}\}/, SecurityOnion::interface);
+
+	#if ( /\{\{/ in real_filter_filename )
+	#	{
+	#	return;
+	#	}
+	#else
+	#	Reporter::info(fmt("BPFConf filename set: %s (%s)", real_filter_filename, Cluster::node));
+
+	if ( real_filter_filename != current_filter_filename )
+		{
+		current_filter_filename = real_filter_filename;
+		Input::add_event([$source=real_filter_filename,
+		                  $name="bpfconf",
+		                  $reader=Input::READER_RAW,
+		                  $mode=Input::REREAD,
+		                  $want_record=F,
+		                  $fields=FilterLine,
+		                  $ev=BPFConf::line]);
+		}
+	}
+
+#event SecurityOnion::found_sensorname(name: string)
+#	{
+#	add_filter_file();
+#	}
+
+event bro_init() &priority=5
+	{
+	if ( BPFConf::filename != "" )
+		add_filter_file();
+	}
+
+