refactor(userspace/engine): polish evttype resolver and use it in rule loader

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/engine/falco_engine.cpp

@@ -412,6 +412,7 @@ void falco_engine::print_stats()
 void falco_engine::add_filter(std::shared_ptr<gen_event_filter> filter,
 			      std::string &rule,
 			      std::string &source,
+			      std::set<uint16_t> &evttypes,
 			      std::set<std::string> &tags)
 {
 	auto it = find_ruleset(source);
@@ -421,7 +422,7 @@ void falco_engine::add_filter(std::shared_ptr<gen_event_filter> filter,
 		throw falco_exception(err);
 	}
 
-	it->ruleset->add(source, rule, tags, filter);
+	it->ruleset->add(source, rule, tags, evttypes, filter);
 }
 
 bool falco_engine::is_source_valid(const std::string &source)

userspace/engine/falco_engine.h

@@ -203,6 +203,7 @@ public:
 	void add_filter(std::shared_ptr<gen_event_filter> filter,
 			std::string &rule,
 			std::string &source,
+			std::set<uint16_t> &evttypes,
 			std::set<std::string> &tags);
 
 	//

userspace/engine/filter_evttype_resolver.cpp

@@ -27,15 +27,29 @@ static bool is_evttype_operator(const string& op)
 	return op == "==" || op == "=" || op == "!=" || op == "in";
 }
 
+void filter_evttype_resolver::inversion(set<uint16_t>& types)
+{
+	set<uint16_t> all_types;
+	evttypes("", all_types);
+	if (types != all_types) // we don't invert the "all types" set
+	{
+		set<uint16_t> diff = types;
+		types.clear();
+		set_difference(
+			all_types.begin(), all_types.end(), diff.begin(), diff.end(),
+			inserter(types, types.begin()));
+	}
+}
+
 void filter_evttype_resolver::evttypes(string evtname, set<uint16_t>& out)
 {
 	// Fill in from 2 to PPM_EVENT_MAX-1. 0 and 1 are excluded as
-	// those are PPM_GENERIC_E/PPME_GENERIC_X.
+	// those are PPM_GENERIC_E/PPME_GENERIC_X
 	const struct ppm_event_info* etable = g_infotables.m_event_info;
 	for(uint16_t i = 2; i < PPM_EVENT_MAX; i++)
 	{
-		// Skip "old" event versions that have been replaced
+		// Skip "old" event versions, unused events, or events not matching
-		// by newer event versions, or events that are unused.
+		// the requested evtname
 		if(!(etable[i].flags & (EF_OLD_VERSION | EF_UNUSED))
 			&& (evtname.empty() || string(etable[i].name) == evtname))
 		{
@@ -49,9 +63,7 @@ void filter_evttype_resolver::evttypes(ast::expr* filter, set<uint16_t>& out)
 	m_expect_value = false;
 	m_last_node_evttypes.clear();
 	filter->accept(this);
-	copy(m_last_node_evttypes.begin(),
+	out.insert(m_last_node_evttypes.begin(), m_last_node_evttypes.end());
-		m_last_node_evttypes.end(),
-		inserter(out, out.begin()));
 }
 
 void filter_evttype_resolver::evttypes(
@@ -60,57 +72,47 @@ void filter_evttype_resolver::evttypes(
 	m_expect_value = false;
 	m_last_node_evttypes.clear();
 	filter.get()->accept(this);
-	copy(m_last_node_evttypes.begin(),
+	out.insert(m_last_node_evttypes.begin(), m_last_node_evttypes.end());
-		m_last_node_evttypes.end(),
-		inserter(out, out.begin()));
 }
 
+// "and" nodes evttypes are the intersection of the evttypes of their children.
+// we initialize the set with "all event types"
 void filter_evttype_resolver::visit(ast::and_expr* e)
 {
-	set<uint16_t> nodetypes;
+	set<uint16_t> types, inters;
-	evttypes("", nodetypes);
+	evttypes("", types);
 	m_last_node_evttypes.clear();
 	for (auto &c : e->children)
 	{
-		set<uint16_t> inters;
+		inters.clear();
 		c->accept(this);
 		set_intersection(
-			nodetypes.begin(), nodetypes.end(),
+			types.begin(), types.end(),
 			m_last_node_evttypes.begin(), m_last_node_evttypes.end(),
-			std::inserter(inters, inters.begin()));
+			inserter(inters, inters.begin()));
-		nodetypes = inters;
+		types = inters;
 	}
-	m_last_node_evttypes = nodetypes;
+	m_last_node_evttypes = types;
 }
 
+// "or" nodes evttypes are the union of the evttypes their children
 void filter_evttype_resolver::visit(ast::or_expr* e)
 {
-	set<uint16_t> nodetypes;
+	set<uint16_t> types;
 	m_last_node_evttypes.clear();
 	for (auto &c : e->children)
 	{
 		c->accept(this);
-		copy(m_last_node_evttypes.begin(),
+		types.insert(m_last_node_evttypes.begin(), m_last_node_evttypes.end());
-			m_last_node_evttypes.end(),
-			inserter(nodetypes, nodetypes.begin()));
 	}
-	m_last_node_evttypes = nodetypes;
+	m_last_node_evttypes = types;
 }
 
 void filter_evttype_resolver::visit(ast::not_expr* e)
 {
-	set<uint16_t> diff, all_types;
 	m_last_node_evttypes.clear();
 	e->child->accept(this);
-	evttypes("", all_types);
+	inversion(m_last_node_evttypes);
-	if (all_types != m_last_node_evttypes)
-	{
-		diff = m_last_node_evttypes;
-		m_last_node_evttypes.clear();
-		set_difference(
-			all_types.begin(), all_types.end(), diff.begin(), diff.end(),
-			inserter(m_last_node_evttypes, m_last_node_evttypes.begin()));
-	}
 }
 
 void filter_evttype_resolver::visit(ast::binary_check_expr* e)
@@ -123,13 +125,7 @@ void filter_evttype_resolver::visit(ast::binary_check_expr* e)
 		m_expect_value = false;
 		if (e->op == "!=")
 		{
-			set<uint16_t> all_types;
+			inversion(m_last_node_evttypes);
-			set<uint16_t> diff = m_last_node_evttypes;
-			m_last_node_evttypes.clear();
-			evttypes("", all_types);
-			set_difference(
-				all_types.begin(), all_types.end(), diff.begin(), diff.end(),
-				inserter(m_last_node_evttypes, m_last_node_evttypes.begin()));
 		}
 		return;
 	}

userspace/engine/filter_evttype_resolver.h

@@ -62,6 +62,7 @@ private:
 	void visit(libsinsp::filter::ast::list_expr* e) override;
 	void visit(libsinsp::filter::ast::unary_check_expr* e) override;
 	void visit(libsinsp::filter::ast::binary_check_expr* e) override;
+	void inversion(std::set<uint16_t>& types);
 
 	bool m_expect_value;
 	std::set<uint16_t> m_last_node_evttypes;

userspace/engine/rule_loader.cpp

@@ -17,6 +17,7 @@ limitations under the License.
 #include "falco_engine.h"
 #include "rule_loader.h"
 #include "filter_macro_resolver.h"
+#include "filter_evttype_resolver.h"
 
 #define MAX_VISIBILITY		((uint32_t) -1)
 #define THROW(cond, err)    { if (cond) { throw falco_exception(err); } }
@@ -701,11 +702,14 @@ void rule_loader::compile_rule_infos(
 					throw falco_exception("Rule " + rule.name + ": error " + err);
 				}
 			}
-			cfg.engine->add_filter(filter, rule.name, rule.source, rule.tags);
+
-			if (rule.source == falco_common::syscall_source && r.warn_evttypes)
+			set<uint16_t> evttypes;
+			if(rule.source == falco_common::syscall_source)
 			{
-				auto evttypes = filter->evttypes();
+				filter_evttype_resolver resolver;
-				if (evttypes.size() == 0 || evttypes.size() > 100)
+				resolver.evttypes(ast, evttypes);
+				if ((evttypes.empty() || evttypes.size() > 100)
+					&& r.warn_evttypes)
 				{
 					cfg.warnings.push_back(
 						"Rule " + rule.name + ": warning (no-evttype):\n" +
@@ -713,6 +717,18 @@ void rule_loader::compile_rule_infos(
 						+ "		 This has a significant performance penalty.");
 				}
 			}
+			else if (rule.source == "k8s_audit")
+			{
+				// todo(jasondellaluce): remove this case once k8saudit
+				// gets ported to a plugin
+				evttypes = { ppm_event_type::PPME_GENERIC_X };
+			}
+			else
+			{
+				evttypes = { ppm_event_type::PPME_PLUGINEVENT_E };
+			}
+
+			cfg.engine->add_filter(filter, rule.name, rule.source, evttypes, rule.tags);
 			cfg.engine->enable_rule(rule.name, r.enabled);
 		}
 		catch (exception& e)