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Fix: prevent goroutine leak in avatar fetch (CVE-2026-21720) #113

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Fix: prevent goroutine leak in avatar fetch (CVE-2026-21720) #113

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32 changes: 21 additions & 11 deletions pkg/api/avatar/avatar.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,11 +4,14 @@

// Code from https://github.com/gogits/gogs/blob/v0.7.0/modules/avatar/avatar.go

// patch CVE-2026-21720, credativ GmbH

package avatar

import (
"bufio"
"bytes"
"context"
"fmt"
"io"
"io/ioutil"
Expand Down Expand Up @@ -59,11 +62,13 @@ func (a *Avatar) Encode(wr io.Writer) error {
return err
}

func (a *Avatar) Update() (err error) {
func (a *Avatar) Update(ctx context.Context) (err error) {
select {
case <-time.After(time.Second * 3):
err = fmt.Errorf("get gravatar image %s timeout", a.hash)
case err = <-thunder.GoFetch(gravatarSource+a.hash+"?"+a.reqParams, a):
case <-ctx.Done():
err = fmt.Errorf("request cancelled for %s", a.hash)
case err = <-thunder.GoFetch(ctx, gravatarSource+a.hash+"?"+a.reqParams, a):
}
return err
}
Expand Down Expand Up @@ -93,7 +98,7 @@ func (a *CacheServer) Handler(ctx *models.ReqContext) {

if avatar.Expired() {
// The cache item is either expired or newly created, update it from the server
if err := avatar.Update(); err != nil {
if err := avatar.Update(ctx.Req.Context()); err != nil {
log.Tracef("avatar update error: %v", err)
avatar = a.notFound
}
Expand Down Expand Up @@ -172,28 +177,33 @@ func (t *Thunder) init() {
}
}

func (t *Thunder) Fetch(url string, avatar *Avatar) error {
func (t *Thunder) Fetch(ctx context.Context, url string, avatar *Avatar) error {
t.once.Do(t.init)
task := &thunderTask{
Url: url,
Avatar: avatar,
}
task.Add(1)
t.q <- task
task.Wait()
return task.err
select {
case t.q <- task:
task.Wait()
return task.err
case <-ctx.Done():
return ctx.Err()
}
}

func (t *Thunder) GoFetch(url string, avatar *Avatar) chan error {
c := make(chan error)
func (t *Thunder) GoFetch(ctx context.Context, url string, avatar *Avatar) chan error {
c := make(chan error, 1) // Buffered channel prevents goroutine leak
go func() {
c <- t.Fetch(url, avatar)
c <- t.Fetch(ctx, url, avatar)
}()
return c
}

// thunder download
type thunderTask struct {
Ctx context.Context
Url string
Avatar *Avatar
sync.WaitGroup
Expand All @@ -214,7 +224,7 @@ func (a *thunderTask) fetch() error {
a.Avatar.timestamp = time.Now()

log.Debugf("avatar.fetch(fetch new avatar): %s", a.Url)
req, err := http.NewRequest("GET", a.Url, nil)
req, err := http.NewRequestWithContext(a.Ctx, "GET", a.Url, nil)
if err != nil {
return err
}
Expand Down
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