imap: fix header cache key collisions

Sometimes, aerc lists completely random messages when opening a mailbox.
It only happens when cache-headers=true.

According to RFC 3501:
> The combination of mailbox name, UIDVALIDITY, and UID must refer to
> a single immutable message on that server forever.

It turns out that several mailboxes may have the same UIDVALIDITY value
and may contain messages that have the same UID. When that happens, aerc
assumes that the headers for these messages are already cached and
returns them whereas they are for messages from another mailbox.

Add the mailbox name into the header cache key to avoid these confusing
collisions.

Fixes: 7aa71d334b27 ("imap: add option to cache headers")
Link: https://datatracker.ietf.org/doc/html/rfc3501#section-2.3.1.1
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Inwit <inwit@sindominio.net>

1 files changed, 17 insertions, 13 deletions

diff --git a/worker/imap/cache.go b/worker/imap/cache.go
index 95f9353f..ec7cffd9 100644
--- a/worker/imap/cache.go
+++ b/worker/imap/cache.go
@@ -36,7 +36,7 @@ var (
 	// cacheTag should be updated when changing the cache
 	// structure; this will ensure that the user's cache is cleared and
 	// reloaded when the underlying cache structure changes
-	cacheTag    = []byte("0001")
+	cacheTag    = []byte("0002")
 	cacheTagKey = []byte("cache.tag")
 )
 
@@ -89,13 +89,12 @@ func (w *IMAPWorker) initCacheDb(acct string) {
 }
 
 func (w *IMAPWorker) cacheHeader(mi *models.MessageInfo) {
-	uv := fmt.Sprintf("%d", w.selected.UidValidity)
-	uid := fmt.Sprintf("%d", mi.Uid)
-	w.worker.Debugf("caching header for message %s.%s", uv, uid)
+	key := w.headerKey(mi.Uid)
+	w.worker.Debugf("caching header for message %s", key)
 	hdr := bytes.NewBuffer(nil)
 	err := textproto.WriteHeader(hdr, mi.RFC822Headers.Header.Header)
 	if err != nil {
-		w.worker.Errorf("cannot write header %s.%s: %v", uv, uid, err)
+		w.worker.Errorf("cannot write header %s: %v", key, err)
 		return
 	}
 	h := &CachedHeader{
@@ -111,12 +110,12 @@ func (w *IMAPWorker) cacheHeader(mi *models.MessageInfo) {
 	enc := gob.NewEncoder(data)
 	err = enc.Encode(h)
 	if err != nil {
-		w.worker.Errorf("cannot encode message %s.%s: %v", uv, uid, err)
+		w.worker.Errorf("cannot encode message %s: %v", key, err)
 		return
 	}
-	err = w.cache.Put([]byte("header."+uv+"."+uid), data.Bytes(), nil)
+	err = w.cache.Put(key, data.Bytes(), nil)
 	if err != nil {
-		w.worker.Errorf("cannot write header for message %s.%s: %v", uv, uid, err)
+		w.worker.Errorf("cannot write header for message %s: %v", key, err)
 		return
 	}
 }
@@ -124,10 +123,9 @@ func (w *IMAPWorker) cacheHeader(mi *models.MessageInfo) {
 func (w *IMAPWorker) getCachedHeaders(msg *types.FetchMessageHeaders) []uint32 {
 	w.worker.Tracef("Retrieving headers from cache: %v", msg.Uids)
 	var need []uint32
-	uv := fmt.Sprintf("%d", w.selected.UidValidity)
 	for _, uid := range msg.Uids {
-		u := fmt.Sprintf("%d", uid)
-		data, err := w.cache.Get([]byte("header."+uv+"."+u), nil)
+		key := w.headerKey(uid)
+		data, err := w.cache.Get(key, nil)
 		if err != nil {
 			need = append(need, uid)
 			continue
@@ -136,14 +134,14 @@ func (w *IMAPWorker) getCachedHeaders(msg *types.FetchMessageHeaders) []uint32 {
 		dec := gob.NewDecoder(bytes.NewReader(data))
 		err = dec.Decode(ch)
 		if err != nil {
-			w.worker.Errorf("cannot decode cached header %s.%s: %v", uv, u, err)
+			w.worker.Errorf("cannot decode cached header %s: %v", key, err)
 			need = append(need, uid)
 			continue
 		}
 		hr := bytes.NewReader(ch.Header)
 		textprotoHeader, err := textproto.ReadHeader(bufio.NewReader(hr))
 		if err != nil {
-			w.worker.Errorf("cannot read cached header %s.%s: %v", uv, u, err)
+			w.worker.Errorf("cannot read cached header %s: %v", key, err)
 			need = append(need, uid)
 			continue
 		}
@@ -167,6 +165,12 @@ func (w *IMAPWorker) getCachedHeaders(msg *types.FetchMessageHeaders) []uint32 {
 	return need
 }
 
+func (w *IMAPWorker) headerKey(uid uint32) []byte {
+	key := fmt.Sprintf("header.%s.%d.%d",
+		w.selected.Name, w.selected.UidValidity, uid)
+	return []byte(key)
+}
+
 func cacheDir() (string, error) {
 	dir, err := os.UserCacheDir()
 	if err != nil {