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package main
import (
"bufio"
"encoding/json"
"flag"
"fmt"
"io"
"log"
"os"
"time"
"gopkg.in/yaml.v3"
"github.com/elastic/go-libaudit/v2"
"github.com/elastic/go-libaudit/v2/aucoalesce"
"github.com/elastic/go-libaudit/v2/auparse"
)
var (
fs = flag.NewFlagSet("auparse", flag.ExitOnError)
in = fs.String("in", "-", "input file (defaults to stdin)")
out = fs.String("out", "-", "output file (defaults to stdout)")
interpret = fs.Bool("i", false, "interpret and normalize messages")
idLookup = fs.Bool("id", true, "lookup uid and gid values in messages (requires -i)")
format = fs.String("format", "", "output format, possible values - json, yaml, text (default)")
)
func main() {
if err := fs.Parse(os.Args[1:]); err != nil {
log.Fatal(err)
}
if err := processLogs(); err != nil {
log.Fatalf("error: %v", err)
}
}
func input() (io.ReadCloser, error) {
if *in == "-" {
return os.Stdin, nil
}
return os.Open(*in)
}
func output() (io.WriteCloser, error) {
if *out == "-" {
return os.Stdout, nil
}
return os.OpenFile(*out, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0o600)
}
func processLogs() error {
input, err := input()
if err != nil {
return err
}
defer input.Close()
output, err := output()
if err != nil {
return err
}
defer output.Close()
reassembler, err := libaudit.NewReassembler(5, 2*time.Second, &streamHandler{output})
if err != nil {
return fmt.Errorf("failed to create reassmbler: %w", err)
}
defer reassembler.Close()
// Start goroutine to periodically purge timed-out events.
go func() {
t := time.NewTicker(500 * time.Millisecond)
defer t.Stop()
for range t.C {
if reassembler.Maintain() != nil {
return
}
}
}()
// Process lines from the input.
s := bufio.NewScanner(input)
for s.Scan() {
line := s.Text()
auditMsg, err := auparse.ParseLogLine(line)
if err != nil {
log.Printf("failed to parse message header: %v", err)
}
reassembler.PushMessage(auditMsg)
}
return nil
}
type streamHandler struct {
output io.Writer
}
func (s *streamHandler) ReassemblyComplete(msgs []*auparse.AuditMessage) {
if err := s.outputMultipleMessages(msgs); err != nil {
log.Printf("[WARN] failed writing message to output: %v", err)
}
}
func (*streamHandler) EventsLost(count int) {
log.Printf("detected the loss of %v sequences.", count)
}
func (s *streamHandler) outputMultipleMessages(msgs []*auparse.AuditMessage) error {
var err error
if !*interpret {
if _, err = s.output.Write([]byte("---\n")); err != nil {
return err
}
for _, m := range msgs {
if err = s.outputSingleMessage(m); err != nil {
return err
}
}
return nil
}
event, err := aucoalesce.CoalesceMessages(msgs)
if err != nil {
log.Printf("failed to coalesce messages: %v", err)
return nil
}
if *idLookup {
aucoalesce.ResolveIDs(event)
}
switch *format {
case "json":
if err := s.printJSON(event); err != nil {
log.Printf("failed to marshal event to JSON: %v", err)
}
case "yaml":
if _, err := s.output.Write([]byte("---\n")); err != nil {
return err
}
if err := s.printYAML(event); err != nil {
log.Printf("failed to marshal message to YAML: %v", err)
}
default:
sm := event.Summary
if _, err := s.output.Write([]byte("---\n")); err != nil {
return err
}
_, err := fmt.Fprintf(
s.output,
`time="%v" sequence=%v category=%v type=%v actor=%v/%v action=%v thing=%v/%v how=%v tags=%v`+"\n",
event.Timestamp, event.Sequence, event.Category, event.Type, sm.Actor.Primary, sm.Actor.Secondary,
sm.Action, sm.Object.Primary, sm.Object.Secondary, sm.How, event.Tags,
)
if err != nil {
return err
}
}
return nil
}
func (s *streamHandler) outputSingleMessage(m *auparse.AuditMessage) error {
switch *format {
case "json":
if err := s.printJSON(m.ToMapStr()); err != nil {
log.Printf("failed to marshal message to JSON: %v", err)
}
case "yaml":
if err := s.printYAML(m.ToMapStr()); err != nil {
log.Printf("failed to marshal message to YAML: %v", err)
}
default:
if _, err := fmt.Fprintf(
s.output,
"type=%v msg=%v\n",
m.RecordType, m.RawData,
); err != nil {
return err
}
}
return nil
}
func (s *streamHandler) printJSON(v interface{}) error {
jsonBytes, err := json.Marshal(v)
if err != nil {
return err
}
if _, err = s.output.Write(jsonBytes); err != nil {
return err
}
if _, err = s.output.Write([]byte("\n")); err != nil {
return err
}
return nil
}
func (s *streamHandler) printYAML(v interface{}) error {
yamlBytes, err := yaml.Marshal(v)
if err != nil {
return err
}
if _, err = s.output.Write(yamlBytes); err != nil {
return err
}
if _, err = s.output.Write([]byte("\n")); err != nil {
return err
}
return nil
}
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