Fix incorrect IMAP message purging bug.

Thanks to Ivan Middleton @imiddle for the awesome bug report and
suggested fix.

The bug is most easily generated using Gmail with the $trash variable
set.

Deleted messages are first copied to the $trash folder.  If this is
set to "[Gmail]/Trash", then Gmail inteprets the copy as a "delete"
and sends EXPUNGE messages back for the messages.

cmd_parse_expunge() and cmd_parse_vanished() set the hdr->index to
INT_MAX, which subsequently an imap_expunge_mailbox() will use to
remove the messages from the local mailbox.

If we close the mailbox instead of sync it, Mutt will end up executing
the 'Deleted' flag setting before processing the expunge (because
"imap_check_mailbox() -> imap_cmd_finish()' doesn't set check_status
when we are closing).  The expunged messages will then be included in
the set of 'Deleted' flags.

Unfortunately, because the messages are sorted by *index* before
msgset generation, an incorrect range of UIDs will be sent, which
could easily include messages that should not be deleted.

This fix is a minimal fix for a stable bug fix  excluding
messages with the index set to INT_MAX from all msg sets.  Other
things that should be investigated in master are:

- sorting by UID instead of index before msgset generation
- unsetting the 'active' flag in cmd_parse_expunge() and
  cmd_parse_vanished() instead of waiting until imap_expunge_mailbox()
  to do so.

diff --git a/imap/imap.c b/imap/imap.c
index 696689ba512189e82d9fab3d0dae3a59cfa3ff9f..ef7ce8c43a8b686cbda4f7813c700050e1816ad4 100644 (file)
--- a/imap/imap.c
+++ b/imap/imap.c
@@ -973,8 +973,11 @@ static int imap_make_msg_set (IMAP_DATA* idata, BUFFER* buf, int flag,
        n++)
   {
     match = 0;
-    /* don't include pending expunged messages */
-    if (hdrs[n]->active)
+    /* don't include pending expunged messages.
+     *
+     * TODO: can we unset active in cmd_parse_expunge() and
+     * cmd_parse_vanished() instead of checking for index != INT_MAX. */
+    if (hdrs[n]->active && (hdrs[n]->index != INT_MAX))
       switch (flag)
       {
         case MUTT_DELETED: