Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[Winlogbeat] Prevent Winlogbeat from dropping events with invalid XML #11006

Merged
merged 6 commits into from
Mar 1, 2019
Merged
Show file tree
Hide file tree
Changes from 2 commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 2 additions & 8 deletions winlogbeat/eventlog/wineventlog.go
Original file line number Diff line number Diff line change
Expand Up @@ -174,12 +174,6 @@ func (l *winEventLog) Read() ([]Record, error) {
}

r, err := l.buildRecordFromXML(l.outputBuf.Bytes(), err)
if err != nil {
logp.Err("%s Dropping event. %v", l.logPrefix, err)
incrementMetric(dropReasons, err)
continue
}

r.Offset = checkpoint.EventLogState{
Name: l.channelName,
RecordNumber: r.RecordID,
Expand Down Expand Up @@ -231,8 +225,8 @@ func (l *winEventLog) eventHandles(maxRead int) ([]win.EvtHandle, int, error) {

func (l *winEventLog) buildRecordFromXML(x []byte, recoveredErr error) (Record, error) {
e, err := sys.UnmarshalEventXML(x)
if err != nil {
return Record{}, fmt.Errorf("Failed to unmarshal XML='%s'. %v", x, err)
if err != nil && recoveredErr == nil {
recoveredErr = err
}

err = sys.PopulateAccount(&e.User)
Expand Down
3 changes: 2 additions & 1 deletion winlogbeat/sys/event.go
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,8 @@ import (
// UnmarshalEventXML unmarshals the given XML into a new Event.
func UnmarshalEventXML(rawXML []byte) (Event, error) {
var event Event
err := xml.Unmarshal(rawXML, &event)
decoder := xml.NewDecoder(newXmlSafeReader(rawXML))
err := decoder.Decode(&event)
return event, err
}

Expand Down
78 changes: 78 additions & 0 deletions winlogbeat/sys/xmlreader.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,78 @@
// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you 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.

package sys

import (
"bytes"
"fmt"
"io"
"unicode"
"unicode/utf8"
)

// The type xmlSafeReader escapes UTF control characters in the io.Reader
// it wraps, so that it can be fed to Go's xml parser.
// Characters for which `unicode.IsControl` returns true will be output as
// an hexadecimal unicode escape sequence "\\uNNNN".
type xmlSafeReader struct {
inner io.Reader
backing [256]byte
buf []byte
code []byte
}

var _ io.Reader = (*xmlSafeReader)(nil)

func output(n int) (int, error) {
if n == 0 {
return 0, io.EOF
}
return n, nil
}

// Read implements the io.Reader interface.
func (r *xmlSafeReader) Read(d []byte) (n int, err error) {
if len(r.code) > 0 {
n = copy(d, r.code)
r.code = r.code[n:]
return output(n)
}
if len(r.buf) == 0 {
n, _ = r.inner.Read(r.backing[:])
r.buf = r.backing[:n]
}
for i := 0; i < len(r.buf); {
code, size := utf8.DecodeRune(r.buf[i:])
if unicode.IsControl(code) {
n = copy(d, r.buf[:i])
r.buf = r.buf[n+1:]
r.code = []byte(fmt.Sprintf("\\u%04x", code))
m := copy(d[n:], r.code)
r.code = r.code[m:]
return output(n + m)
}
i += size
}
n = copy(d, r.buf)
r.buf = r.buf[n:]
return output(n)
}

func newXmlSafeReader(rawXML []byte) io.Reader {

This comment was marked as resolved.

return &xmlSafeReader{inner: bytes.NewReader(rawXML)}
}