utils.go

/*
   Velociraptor - Hunting Evil
   Copyright (C) 2019 Velocidex Innovations.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as published
   by the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.

   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
package main

import (
	"context"
	"fmt"
	"io"
	"os"
	"os/signal"
	"strings"
	"syscall"

	humanize "github.com/dustin/go-humanize"
	config_proto "www.velocidex.com/golang/velociraptor/config/proto"
	logging "www.velocidex.com/golang/velociraptor/logging"
	vfilter "www.velocidex.com/golang/vfilter"
)

func InstallSignalHandler(scope *vfilter.Scope) context.Context {

	// Wait for signal. When signal is received we shut down the
	// server.
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGHUP,
		syscall.SIGINT,
		syscall.SIGTERM,
		syscall.SIGQUIT)

	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		// Wait for the signal on this channel.
		<-quit
		scope.Log("Shutting down due to interrupt.")

		scope.Close()
		// Only cancel the context once the scope is fully
		// destroyed. This ensures all the destructors have
		// enougb time to finish when we exit the program
		cancel()
	}()

	return ctx
}

// Turns os.Stdout into into file_store.WriteSeekCloser
type StdoutWrapper struct {
	io.Writer
}

func (self *StdoutWrapper) Seek(offset int64, whence int) (int64, error) {
	return 0, nil
}

func (self *StdoutWrapper) Close() error {
	return nil
}

func (self *StdoutWrapper) Truncate(offset int64) error {
	return nil
}

// https://golangcode.com/download-a-file-with-progress/
// WriteCounter counts the number of bytes written to it. It implements to the io.Writer
// interface and we can pass this into io.TeeReader() which will report progress on each
// write cycle.
type WriteCounter struct {
	name  string
	Total uint64
}

func (wc *WriteCounter) Write(p []byte) (int, error) {
	n := len(p)
	wc.Total += uint64(n)
	wc.PrintProgress()
	return n, nil
}

func (wc WriteCounter) PrintProgress() {
	// Clear the line by using a character return to go back to the start and remove
	// the remaining characters by filling it with spaces
	fmt.Printf("\r%s", strings.Repeat(" ", 35))

	// Return again and print current status of download
	// We use the humanize package to print the bytes in a meaningful way (e.g. 10 MB)
	fmt.Printf("\rDownloading %s ... %s complete", wc.name, humanize.Bytes(wc.Total))
}

var (
	// Set to true when the client gracefully exits.
	exiting = false
)

// This is only called when there is something very wrong! If the
// executor loop somehow exits due to panic or a bug we will not be
// able to communicate with the endpoint. We have to hard exit here to
// ensure the process can be restarted. This is a last resort!
func on_error(config_obj *config_proto.Config) {
	// It's ok we are supposed to exit.
	if exiting {
		return
	}

	logger := logging.GetLogger(config_obj, &logging.ClientComponent)
	logger.Error("Exiting hard due to bug or KillKillKill! This should not happen!")

	os.Exit(-1)
}

func install_sig_handler() (context.Context, context.CancelFunc) {
	quit := make(chan os.Signal, 1)
	signal.Notify(quit, syscall.SIGHUP,
		syscall.SIGINT,
		syscall.SIGTERM,
		syscall.SIGQUIT)

	ctx, cancel := context.WithCancel(context.Background())

	go func() {
		select {
		case <-quit:
			// Ordered shutdown now.
			exiting = true
			cancel()

		case <-ctx.Done():
			return
		}
	}()

	return ctx, cancel

}