new(engine): add selective overrides

Signed-off-by: Luca Guerra <luca@guerra.sh>

unit_tests/engine/test_rule_loader.cpp

@@ -0,0 +1,233 @@
+#include <gtest/gtest.h>
+
+#include "falco_engine.h"
+#include "rule_loader_reader.h"
+#include "rule_loader_compiler.h"
+
+class engine_loader_test : public ::testing::Test {
+protected:
+	void SetUp() override
+	{
+		m_sample_ruleset = "sample-ruleset";
+		m_sample_source = falco_common::syscall_source;
+
+		// create a falco engine ready to load the ruleset
+		m_engine.reset(new falco_engine());
+		m_filter_factory = std::shared_ptr<gen_event_filter_factory>(
+			new sinsp_filter_factory(nullptr, m_filterlist));
+		m_formatter_factory = std::shared_ptr<gen_event_formatter_factory>(
+			new sinsp_evt_formatter_factory(nullptr, m_filterlist));
+		m_engine->add_source(m_sample_source, m_filter_factory, m_formatter_factory);
+	}
+
+	void TearDown() override
+	{
+
+	}
+
+	bool load_rules(std::string rules_content, std::string rules_filename)
+	{
+		bool ret = false;
+		falco::load_result::rules_contents_t rc = {{rules_filename, rules_content}};
+		m_load_result = m_engine->load_rules(rules_content, rules_filename);
+		m_load_result_string = m_load_result->as_string(true, rc);
+		ret = m_load_result->successful();
+
+		if (ret)
+		{
+			m_engine->enable_rule("", true, m_sample_ruleset);
+		}
+
+		return ret;
+	}
+
+	std::string m_sample_ruleset;
+	std::string m_sample_source;
+	sinsp_filter_check_list m_filterlist;
+	std::shared_ptr<gen_event_filter_factory> m_filter_factory;
+	std::shared_ptr<gen_event_formatter_factory> m_formatter_factory;
+	std::unique_ptr<falco_engine> m_engine;
+	std::unique_ptr<falco::load_result> m_load_result;
+	std::string m_load_result_string;
+};
+
+std::string s_sample_ruleset = "sample-ruleset";
+std::string s_sample_source = falco_common::syscall_source;
+
+TEST_F(engine_loader_test, list_append)
+{
+    std::string rules_content = R"END(
+- list: shell_binaries
+  items: [ash, bash, csh, ksh, sh, tcsh, zsh, dash]
+
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type=open and proc.name in (shell_binaries)
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- list: shell_binaries
+  items: [pwsh]
+  override:
+    items: append
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["details"]["condition_compiled"].template get<std::string>(),
+		"(evt.type = open and proc.name in (ash, bash, csh, ksh, sh, tcsh, zsh, dash, pwsh))");
+}
+
+TEST_F(engine_loader_test, condition_append)
+{
+    std::string rules_content = R"END(
+- macro: interactive
+  condition: >
+    ((proc.aname=sshd and proc.name != sshd) or
+    proc.name=systemd-logind or proc.name=login)
+
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type=open and interactive
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- macro: interactive
+  condition: or proc.name = ssh
+  override:
+    condition: append
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["details"]["condition_compiled"].template get<std::string>(),
+		"(evt.type = open and (((proc.aname = sshd and proc.name != sshd) or proc.name = systemd-logind or proc.name = login) or proc.name = ssh))");
+}
+
+TEST_F(engine_loader_test, rule_override_append)
+{
+    std::string rules_content = R"END(
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type=open
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- rule: legit_rule
+  desc: with append
+  condition: and proc.name = cat
+  output: proc=%proc.name
+  override:
+    desc: append
+    condition: append
+    output: append
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["info"]["condition"].template get<std::string>(),
+	 	"evt.type=open and proc.name = cat");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["output"].template get<std::string>(),
+	 	"user=%user.name command=%proc.cmdline file=%fd.name proc=%proc.name");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["description"].template get<std::string>(),
+	 	"legit rule description with append");
+}
+
+
+TEST_F(engine_loader_test, rule_append)
+{
+    std::string rules_content = R"END(
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type=open
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- rule: legit_rule
+  condition: and proc.name = cat
+  append: true
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["details"]["condition_compiled"].template get<std::string>(),
+	 	"(evt.type = open and proc.name = cat)");
+}
+
+
+TEST_F(engine_loader_test, rule_override_replace)
+{
+    std::string rules_content = R"END(
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type=open
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- rule: legit_rule
+  desc: a replaced legit description
+  condition: evt.type = close
+  override:
+    desc: replace
+    condition: replace
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["info"]["condition"].template get<std::string>(),
+	 	"evt.type = close");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["output"].template get<std::string>(),
+	 	"user=%user.name command=%proc.cmdline file=%fd.name");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["description"].template get<std::string>(),
+	 	"a replaced legit description");
+}
+
+TEST_F(engine_loader_test, rule_override_append_replace)
+{
+    std::string rules_content = R"END(
+- rule: legit_rule
+  desc: legit rule description
+  condition: evt.type = close
+  output: user=%user.name command=%proc.cmdline file=%fd.name
+  priority: INFO
+
+- rule: legit_rule
+  desc: a replaced legit description
+  condition: and proc.name = cat
+  priority: WARNING
+  override:
+    desc: replace
+    condition: append
+    priority: replace
+)END";
+
+	std::string rule_name = "legit_rule";
+	ASSERT_TRUE(load_rules(rules_content, "legit_rules.yaml")) << m_load_result_string;
+
+	auto rule_description = m_engine->describe_rule(&rule_name, {});
+	ASSERT_EQ(rule_description["rules"][0]["info"]["condition"].template get<std::string>(),
+	 	"evt.type = close and proc.name = cat");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["output"].template get<std::string>(),
+	 	"user=%user.name command=%proc.cmdline file=%fd.name");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["description"].template get<std::string>(),
+	 	"a replaced legit description");
+
+	ASSERT_EQ(rule_description["rules"][0]["info"]["priority"].template get<std::string>(),
+	 	"Warning");
+}

userspace/engine/rule_loader.cpp

@@ -41,7 +41,8 @@ static const std::string item_type_strings[] = {
 	"condition expression",
 	"rule output",
 	"rule output expression",
-	"rule priority"
+	"rule priority",
+	"overrides"
 };
 
 const std::string& rule_loader::context::item_type_as_string(enum item_type it)
@@ -553,6 +554,11 @@ rule_loader::rule_info::rule_info(context &ctx)
 {
 }
 
+rule_loader::rule_update_info::rule_update_info(context &ctx)
+	: ctx(ctx), cond_ctx(ctx)
+{
+}
+
 rule_loader::rule_load_exception::rule_load_exception(falco::load_result::error_code ec, const std::string& msg, const context& ctx)
 	: ec(ec), msg(msg), ctx(ctx)
 {

userspace/engine/rule_loader.h

@@ -19,6 +19,7 @@ limitations under the License.
 
 #include <string>
 #include <vector>
+#include <optional>
 #include <yaml-cpp/yaml.h>
 #include <nlohmann/json.hpp>
 #include "falco_source.h"
@@ -56,7 +57,8 @@ namespace rule_loader
 			CONDITION_EXPRESSION,
 			RULE_OUTPUT,
 			RULE_OUTPUT_EXPRESSION,
-			RULE_PRIORITY
+			RULE_PRIORITY,
+			OVERRIDE
 		};
 
 		static const std::string& item_type_as_string(enum item_type it);
@@ -451,4 +453,38 @@ namespace rule_loader
 		bool warn_evttypes;
 		bool skip_if_unknown_filter;
 	};
+
+	/*!
+		\brief Represents infos about a rule update (append or replace) request
+	*/
+
+	struct rule_update_info
+	{
+		rule_update_info(context &ctx);
+		~rule_update_info() = default;
+		rule_update_info(rule_update_info&&) = default;
+		rule_update_info& operator = (rule_update_info&&) = default;
+		rule_update_info(const rule_update_info&) = default;
+		rule_update_info& operator = (const rule_update_info&) = default;
+
+		bool has_any_value()
+		{
+			return cond.has_value() || output.has_value() || desc.has_value() || tags.has_value() ||
+				   exceptions.has_value() || priority.has_value() || enabled.has_value() ||
+				   warn_evttypes.has_value() || skip_if_unknown_filter.has_value();
+		}
+
+		context ctx;
+		context cond_ctx;
+		std::string name;
+		std::optional<std::string> cond;
+		std::optional<std::string> output;
+		std::optional<std::string> desc;
+		std::optional<std::set<std::string>> tags;
+		std::optional<std::vector<rule_exception_info>> exceptions;
+		std::optional<falco_common::priority_type> priority;
+		std::optional<bool> enabled;
+		std::optional<bool> warn_evttypes;
+		std::optional<bool> skip_if_unknown_filter;
+	};
 };