[Dovecot] maildir compressed message fix patch

[Richard Platel]

When a compressed maildir message has a bad S= size in its filename it puts the user in an unrecoverable state, since maildir's do_fix_size function just does a stat() on the maildir file and saves the compressed size in the filename.

This (quick, rough, barely tested) patch addresses this issue, it's inefficient, but we're already in a hopefully rare emergency situation.

--- maildir-mail.c      2014-02-11 22:23:37.000000000 +0000
+++ maildir-mail.c.new  2014-04-24 20:41:25.000000000 +0000
@@ -8,6 +8,7 @@
 #include "maildir-filename.h"
 #include "maildir-uidlist.h"
 #include "maildir-sync.h"
+#include "compression.h"

 #include <stdio.h>
 #include <stdlib.h>
@@ -640,6 +641,10 @@
 {
        const char *fname, *newpath, *extra, *info, *dir;
        struct stat st;
+  const struct stat * stp;
+  const struct compression_handler * handler;
+  struct istream * fstream;
+  struct istream * cstream;

        fname = strrchr(path, '/');
        i_assert(fname != NULL);
@@ -650,13 +655,29 @@
        info = strchr(fname, MAILDIR_INFO_SEP);
        if (info == NULL) info = "";

+  fstream = i_stream_create_file(path, 1024);
+  handler = compression_detect_handler(fstream);
+  if (handler != NULL && handler->create_istream != NULL)
+  {
+    cstream = handler->create_istream(fstream, TRUE);
+    if (i_stream_stat(cstream, TRUE, &stp) < 0)
+    {
+      return -1;
+    }
+    st = *stp; /* dumb copy */
+    i_stream_unref(&cstream);
+  }
+  else
+  {
        if (stat(path, &st) < 0) {
                if (errno == ENOENT)
                        return 0;
                mail_storage_set_critical(&mbox->storage->storage,
                                          "stat(%s) failed: %m", path);
                return -1;
-       }
+         }
+  }
+  i_stream_unref(&fstream);

        newpath = t_strdup_printf("%s/%s,S=%"PRIuUOFF_T"%s", dir,
                                  t_strdup_until(fname, extra),