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mongodb_parser.go
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mongodb_parser.go
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package mongodb
import (
"encoding/json"
"errors"
"strings"
"github.com/elastic/beats/libbeat/common"
"github.com/elastic/beats/libbeat/logp"
"gopkg.in/mgo.v2/bson"
)
func mongodbMessageParser(s *stream) (bool, bool) {
d := newDecoder(s.data)
length, err := d.readInt32()
if err != nil {
// Not even enough data to parse length of message
return true, false
}
if length > len(s.data) {
// Not yet reached the end of message
return true, false
}
// Tell decoder to only consider current message
d.truncate(length)
// fill up the header common to all messages
// see http://docs.mongodb.org/meta-driver/latest/legacy/mongodb-wire-protocol/#standard-message-header
s.message.messageLength = length
s.message.requestID, _ = d.readInt32()
s.message.responseTo, _ = d.readInt32()
code, _ := d.readInt32()
opCode := opCode(code)
if !validOpcode(opCode) {
logp.Err("Unknown operation code: %v", opCode)
return false, false
}
s.message.opCode = opCode
s.message.isResponse = false // default is that the message is a request. If not opReplyParse will set this to false
s.message.expectsResponse = false
debugf("opCode = %v", s.message.opCode)
// then split depending on operation type
s.message.event = common.MapStr{}
switch s.message.opCode {
case opReply:
s.message.isResponse = true
return opReplyParse(d, s.message)
case opMsg:
s.message.method = "msg"
return opMsgParse(d, s.message)
case opUpdate:
s.message.method = "update"
return opUpdateParse(d, s.message)
case opInsert:
s.message.method = "insert"
return opInsertParse(d, s.message)
case opQuery:
s.message.expectsResponse = true
return opQueryParse(d, s.message)
case opGetMore:
s.message.method = "getMore"
s.message.expectsResponse = true
return opGetMoreParse(d, s.message)
case opDelete:
s.message.method = "delete"
return opDeleteParse(d, s.message)
case opKillCursor:
s.message.method = "killCursors"
return opKillCursorsParse(d, s.message)
}
return false, false
}
// see http://docs.mongodb.org/meta-driver/latest/legacy/mongodb-wire-protocol/#op-reply
func opReplyParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // ignore flags for now
m.event["cursorId"], err = d.readInt64()
m.event["startingFrom"], err = d.readInt32()
numberReturned, err := d.readInt32()
m.event["numberReturned"] = numberReturned
debugf("Prepare to read %d document from reply", m.event["numberReturned"])
documents := make([]interface{}, numberReturned)
for i := 0; i < numberReturned; i++ {
var document bson.M
document, err = d.readDocument()
// Check if the result is actually an error
if i == 0 {
if mongoError, present := document["$err"]; present {
m.error, err = doc2str(mongoError)
}
if writeErrors, present := document["writeErrors"]; present {
m.error, err = doc2str(writeErrors)
}
}
documents[i] = document
}
m.documents = documents
if err != nil {
logp.Err("An error occurred while parsing OP_REPLY message: %s", err)
return false, false
}
return true, true
}
func opMsgParse(d *decoder, m *mongodbMessage) (bool, bool) {
var err error
m.event["message"], err = d.readCStr()
if err != nil {
logp.Err("An error occurred while parsing OP_MSG message: %s", err)
return false, false
}
return true, true
}
func opUpdateParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // always ZERO, a slot reserved in the protocol for future use
m.event["fullCollectionName"], err = d.readCStr()
_, err = d.readInt32() // ignore flags for now
m.event["selector"], err = d.readDocumentStr()
m.event["update"], err = d.readDocumentStr()
if err != nil {
logp.Err("An error occurred while parsing OP_UPDATE message: %s", err)
return false, false
}
return true, true
}
func opInsertParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // ignore flags for now
m.event["fullCollectionName"], err = d.readCStr()
// TODO parse bson documents
// Not too bad if it is not done, as all recent mongodb clients send insert as a command over a query instead of this
// Find an old client to generate a pcap with legacy protocol ?
if err != nil {
logp.Err("An error occurred while parsing OP_INSERT message: %s", err)
return false, false
}
return true, true
}
func extractDocuments(query map[string]interface{}) []interface{} {
docsVi, present := query["documents"]
if !present {
return []interface{}{}
}
docs, ok := docsVi.([]interface{})
if !ok {
return []interface{}{}
}
return docs
}
// Try to guess whether this key:value pair found in
// the query represents a command.
func isDatabaseCommand(key string, val interface{}) bool {
nameExists := false
for _, cmd := range databaseCommands {
if strings.EqualFold(cmd, key) {
nameExists = true
break
}
}
if !nameExists {
return false
}
// value should be either a string or the value 1
_, ok := val.(string)
num, _ := val.(float64)
if ok || num == 1 {
return true
}
return false
}
func opQueryParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // ignore flags for now
fullCollectionName, err := d.readCStr()
m.event["fullCollectionName"] = fullCollectionName
m.event["numberToSkip"], err = d.readInt32()
m.event["numberToReturn"], err = d.readInt32()
query, err := d.readDocument()
if d.i < len(d.in) {
m.event["returnFieldsSelector"], err = d.readDocumentStr()
}
// Actual method is either a 'find' or a command passing through a query
if strings.HasSuffix(fullCollectionName, ".$cmd") {
m.method = "otherCommand"
m.resource = fullCollectionName
for key, val := range query {
debugf("key=%v val=%s", key, val)
if isDatabaseCommand(key, val) {
debugf("is db command")
col, ok := val.(string)
if ok {
// replace $cmd with the actual collection name
m.resource = fullCollectionName[:len(fullCollectionName)-4] + col
}
delete(query, key)
m.method = key
}
}
} else {
m.method = "find"
m.resource = fullCollectionName
}
m.params = query
if err != nil {
logp.Err("An error occurred while parsing OP_QUERY message: %s", err)
return false, false
}
return true, true
}
func opGetMoreParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // always ZERO, a slot reserved in the protocol for future use
m.event["fullCollectionName"], err = d.readCStr()
m.event["numberToReturn"], err = d.readInt32()
m.event["cursorId"], err = d.readInt64()
if err != nil {
logp.Err("An error occurred while parsing OP_GET_MORE message: %s", err)
return false, false
}
return true, true
}
func opDeleteParse(d *decoder, m *mongodbMessage) (bool, bool) {
_, err := d.readInt32() // always ZERO, a slot reserved in the protocol for future use
m.event["fullCollectionName"], err = d.readCStr()
_, err = d.readInt32() // ignore flags for now
m.event["selector"], err = d.readDocumentStr()
if err != nil {
logp.Err("An error occurred while parsing OP_DELETE message: %s", err)
return false, false
}
return true, true
}
func opKillCursorsParse(d *decoder, m *mongodbMessage) (bool, bool) {
// TODO ? Or not, content is not very interesting.
return true, true
}
// NOTE: The following functions are inspired by the source of the go-mgo/mgo project
// https://github.com/go-mgo/mgo/blob/v2/bson/decode.go
type decoder struct {
in []byte
i int
}
func newDecoder(in []byte) *decoder {
return &decoder{in, 0}
}
func (d *decoder) truncate(length int) {
d.in = d.in[:length]
}
func (d *decoder) readCStr() (string, error) {
start := d.i
end := start
l := len(d.in)
for ; end != l; end++ {
if d.in[end] == '\x00' {
break
}
}
d.i = end + 1
if d.i > l {
return "", errors.New("cstring not finished")
}
return string(d.in[start:end]), nil
}
func (d *decoder) readInt32() (int, error) {
b, err := d.readBytes(4)
if err != nil {
return 0, err
}
return int((uint32(b[0]) << 0) |
(uint32(b[1]) << 8) |
(uint32(b[2]) << 16) |
(uint32(b[3]) << 24)), nil
}
func (d *decoder) readInt64() (int, error) {
b, err := d.readBytes(8)
if err != nil {
return 0, err
}
return int((uint64(b[0]) << 0) |
(uint64(b[1]) << 8) |
(uint64(b[2]) << 16) |
(uint64(b[3]) << 24) |
(uint64(b[4]) << 32) |
(uint64(b[5]) << 40) |
(uint64(b[6]) << 48) |
(uint64(b[7]) << 56)), nil
}
func (d *decoder) readDocument() (bson.M, error) {
start := d.i
documentLength, err := d.readInt32()
d.i = start + documentLength
if len(d.in) < d.i {
return nil, errors.New("document out of bounds")
}
documentMap := bson.M{}
debugf("Parse %d bytes document from remaining %d bytes", documentLength, len(d.in)-start)
err = bson.Unmarshal(d.in[start:d.i], documentMap)
if err != nil {
debugf("Unmarshall error %v", err)
return nil, err
}
return documentMap, err
}
func doc2str(documentMap interface{}) (string, error) {
document, err := json.Marshal(documentMap)
return string(document), err
}
func (d *decoder) readDocumentStr() (string, error) {
documentMap, err := d.readDocument()
document, err := doc2str(documentMap)
return document, err
}
func (d *decoder) readBytes(length int32) ([]byte, error) {
start := d.i
d.i += int(length)
if d.i > len(d.in) {
return *new([]byte), errors.New("No byte to read")
}
return d.in[start : start+int(length)], nil
}