forgejo/modules/eventsource/manager.go
Mathieu Fenniak f93d2cb261 ci: detect and prevent empty case statements in Go code (#11593)
One of the security patches released 2026-03-09 [fixed a vulnerability](d1c7b04d09) caused by a misapplication of Go `case` statements, where the implementation would have been correct if Go `case` statements automatically fall through to the next case block, but they do not.  This PR adds a semgrep rule which detects any empty `case` statement and raises an error, in order to prevent this coding mistake in the future.

For example, code like this will now trigger a build error:
```go
	switch setting.Protocol {
	case setting.HTTPUnix:
	case setting.FCGI:
	case setting.FCGIUnix:
	default:
		defaultLocalURL := string(setting.Protocol) + "://"
	}
```

Example error:
```
    cmd/web.go
   ❯❯❱ semgrep.config.forgejo-switch-empty-case
          switch has a case block with no content. This is treated as "break" by Go, but developers may
          confuse it for "fallthrough".  To fix this error, disambiguate by using "break" or
          "fallthrough".

          279┆ switch setting.Protocol {
          280┆ case setting.HTTPUnix:
          281┆ case setting.FCGI:
          282┆ case setting.FCGIUnix:
          283┆ default:
          284┆   defaultLocalURL := string(setting.Protocol) + "://"
          285┆   if setting.HTTPAddr == "0.0.0.0" {
          286┆           defaultLocalURL += "localhost"
          287┆   } else {
          288┆           defaultLocalURL += setting.HTTPAddr
```

As described in the error output, this error can be fixed by explicitly listing `break` (the real Go behaviour, to do nothing in the block), or by listing `fallthrough` (if the intent was to fall through).

All existing code triggering this detection has been changed to `break` (or, rarely, irrelevant cases have been removed), which should maintain the same code functionality.  While performing this fixup, a light analysis was performed on each case and they *appeared* correct, but with ~65 cases I haven't gone into extreme depth.

Tests are present for the semgrep rule in `.semgrep/tests/go.go`.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [ ] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [x] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11593
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>
2026-03-10 02:50:28 +01:00

81 lines
1.6 KiB
Go

// Copyright 2020 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package eventsource
import (
"sync"
)
// Manager manages the eventsource Messengers
type Manager struct {
mutex sync.Mutex
messengers map[int64]*Messenger
connection chan struct{}
}
var manager *Manager
func init() {
manager = &Manager{
messengers: make(map[int64]*Messenger),
connection: make(chan struct{}, 1),
}
}
// GetManager returns a Manager and initializes one as singleton if there's none yet
func GetManager() *Manager {
return manager
}
// Register message channel
func (m *Manager) Register(uid int64) <-chan *Event {
m.mutex.Lock()
messenger, ok := m.messengers[uid]
if !ok {
messenger = NewMessenger(uid)
m.messengers[uid] = messenger
}
select {
case m.connection <- struct{}{}:
break
default:
break
}
m.mutex.Unlock()
return messenger.Register()
}
// Unregister message channel
func (m *Manager) Unregister(uid int64, channel <-chan *Event) {
m.mutex.Lock()
defer m.mutex.Unlock()
messenger, ok := m.messengers[uid]
if !ok {
return
}
if messenger.Unregister(channel) {
delete(m.messengers, uid)
}
}
// UnregisterAll message channels
func (m *Manager) UnregisterAll() {
m.mutex.Lock()
defer m.mutex.Unlock()
for _, messenger := range m.messengers {
messenger.UnregisterAll()
}
m.messengers = map[int64]*Messenger{}
}
// SendMessage sends a message to a particular user
func (m *Manager) SendMessage(uid int64, message *Event) {
m.mutex.Lock()
messenger, ok := m.messengers[uid]
m.mutex.Unlock()
if ok {
messenger.SendMessage(message)
}
}