falco/userspace/engine/formats.cpp

/*
Copyright (C) 2020 The Falco Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#include <json/json.h>

#include "formats.h"
#include "falco_engine.h"
#include "banned.h" // This raises a compilation error when certain functions are used

sinsp *falco_formats::s_inspector = NULL;
falco_engine *falco_formats::s_engine = NULL;
bool falco_formats::s_json_output = false;
bool falco_formats::s_json_include_output_property = true;
std::unique_ptr<sinsp_evt_formatter_cache> falco_formats::s_formatters = NULL;

const static struct luaL_Reg ll_falco[] =
	{
		{"formatter", &falco_formats::lua_formatter},
		{"free_formatter", &falco_formats::lua_free_formatter},
		{NULL, NULL}};

void falco_formats::init(sinsp *inspector,
			 falco_engine *engine,
			 lua_State *ls,
			 bool json_output,
			 bool json_include_output_property)
{
	s_inspector = inspector;
	s_engine = engine;
	s_json_output = json_output;
	s_json_include_output_property = json_include_output_property;

	// todo(leogr): we should have used std::make_unique, but we cannot since it's not C++14
	s_formatters = std::unique_ptr<sinsp_evt_formatter_cache>(new sinsp_evt_formatter_cache(s_inspector));

	luaL_openlib(ls, "formats", ll_falco, 0);
}

void falco_formats::create_sinsp_formatter(lua_State *ls, const std::string &format)
{
	sinsp_evt_formatter *formatter;
	formatter = new sinsp_evt_formatter(s_inspector, format);
	lua_pushnil(ls);
	lua_pushlightuserdata(ls, formatter);
}

int falco_formats::lua_formatter(lua_State *ls)
{
	string source = luaL_checkstring(ls, -2);
	string format = luaL_checkstring(ls, -1);

	try
	{
		if(source == "syscall")
		{
			create_sinsp_formatter(ls, format);
		}
		else if (source == "k8s_audit")
		{
			json_event_formatter *formatter;
			formatter = new json_event_formatter(s_engine->json_factory(), format);
			lua_pushnil(ls);
			lua_pushlightuserdata(ls, formatter);
		} else {
			// Not one of the built-in sources, so assume it's a plugin.
			// Plugins behave identically to syscall events for now.
			create_sinsp_formatter(ls, format);
		}
	}
	catch(exception &e)
	{
		std::ostringstream os;

		os << "Invalid output format '"
		   << format
		   << "': '"
		   << e.what()
		   << "'";

		lua_pushstring(ls, os.str().c_str());
		lua_pushnil(ls);
	}

	return 2;
}

void falco_formats::delete_sinsp_formatter(lua_State *ls)
{
	sinsp_evt_formatter *formatter = (sinsp_evt_formatter *)lua_topointer(ls, -1);
	delete(formatter);
}

int falco_formats::lua_free_formatter(lua_State *ls)
{
	if(!lua_islightuserdata(ls, -1) ||
	   !lua_isstring(ls, -2))

	{
		luaL_error(ls, "Invalid argument passed to free_formatter");
	}

	string source = luaL_checkstring(ls, -2);

	if(source == "syscall")
	{
		delete_sinsp_formatter(ls);
	}
	else if (source == "k8s_audit")
	{
		json_event_formatter *formatter = (json_event_formatter *)lua_topointer(ls, -1);
		delete(formatter);
	}
	else
	{
		// Not one of the built-in sources, so assume it's a plugin.
		// Plugins behave identically to syscall events for now.
		delete_sinsp_formatter(ls);
	}
	return 0;
}

void falco_formats::format_sinsp_event(const gen_event *evt, const std::string &format,
				       std::string &line, std::string &json_line, std::string &sformat)
{
	// This is "output"
	s_formatters->tostring((sinsp_evt *)evt, sformat, &line);

	if(s_json_output)
	{
		sinsp_evt::param_fmt cur_fmt = s_inspector->get_buffer_format();
		switch(cur_fmt)
		{
		case sinsp_evt::PF_NORMAL:
			s_inspector->set_buffer_format(sinsp_evt::PF_JSON);
			break;
		case sinsp_evt::PF_EOLS:
			s_inspector->set_buffer_format(sinsp_evt::PF_JSONEOLS);
			break;
		case sinsp_evt::PF_HEX:
			s_inspector->set_buffer_format(sinsp_evt::PF_JSONHEX);
			break;
		case sinsp_evt::PF_HEXASCII:
			s_inspector->set_buffer_format(sinsp_evt::PF_JSONHEXASCII);
			break;
		case sinsp_evt::PF_BASE64:
			s_inspector->set_buffer_format(sinsp_evt::PF_JSONBASE64);
			break;
		default:
			// do nothing
			break;
		}
		// This is output fields
		s_formatters->tostring((sinsp_evt *)evt, sformat, &json_line);

		// The formatted string might have a leading newline. If it does, remove it.
		if(json_line[0] == '\n')
		{
			json_line.erase(0, 1);
		}
		s_inspector->set_buffer_format(cur_fmt);
	}
}

string falco_formats::format_event(const gen_event *evt, const std::string &rule, const std::string &source,
				   const std::string &level, const std::string &format)
{

	string line;
	string json_line;
	string sformat = format;

	if(source == "syscall")
	{
		format_sinsp_event(evt, format, line, json_line, sformat);
	}
	else if (source == "k8s_audit")
	{
		json_event_formatter formatter(s_engine->json_factory(), sformat);

		line = formatter.tostring((json_event *)evt);

		if(s_json_output)
		{
			json_line = formatter.tojson((json_event *)evt);
		}
	} else {
		// Not one of the built-in sources, so assume it's a plugin.
		// Plugins behave identically to syscall events for now.
		format_sinsp_event(evt, format, line, json_line, sformat);
	}

	// For JSON output, the formatter returned a json-as-text
	// object containing all the fields in the original format
	// message as well as the event time in ns. Use this to build
	// a more detailed object containing the event time, rule,
	// severity, full output, and fields.
	if(s_json_output)
	{
		Json::Value event;
		Json::FastWriter writer;
		string full_line;

		// Convert the time-as-nanoseconds to a more json-friendly ISO8601.
		time_t evttime = evt->get_ts() / 1000000000;
		char time_sec[20]; // sizeof "YYYY-MM-DDTHH:MM:SS"
		char time_ns[12];  // sizeof ".sssssssssZ"
		string iso8601evttime;

		strftime(time_sec, sizeof(time_sec), "%FT%T", gmtime(&evttime));
		snprintf(time_ns, sizeof(time_ns), ".%09luZ", evt->get_ts() % 1000000000);
		iso8601evttime = time_sec;
		iso8601evttime += time_ns;
		event["time"] = iso8601evttime;
		event["rule"] = rule;
		event["priority"] = level;

		if(s_json_include_output_property)
		{
			// This is the filled-in output line.
			event["output"] = line;
		}

		full_line = writer.write(event);

		// Json::FastWriter may add a trailing newline. If it
		// does, remove it.
		if(full_line[full_line.length() - 1] == '\n')
		{
			full_line.resize(full_line.length() - 1);
		}

		// Cheat-graft the output from the formatter into this
		// string. Avoids an unnecessary json parse just to
		// merge the formatted fields at the object level.
		full_line.pop_back();
		full_line.append(", \"output_fields\": ");
		full_line.append(json_line);
		full_line.append("}");
		line = full_line;
	}

	return line.c_str();
}

map<string, string> falco_formats::resolve_tokens(const gen_event *evt, const std::string &source, const std::string &format)
{
	string sformat = format;
	map<string, string> values;
	if(source == "syscall")
	{
		s_formatters->resolve_tokens((sinsp_evt *)evt, sformat, values);
	}
	else if (source == "k8s_audit")
	{
		json_event_formatter json_formatter(s_engine->json_factory(), sformat);
		values = json_formatter.tomap((json_event *)evt);
	}
	else
	{
		// Not one of the built-in sources, so assume it's a plugin.
		// Plugins behave identically to syscall events for now.
		s_formatters->resolve_tokens((sinsp_evt *)evt, sformat, values);
	}
	return values;
}