kbx: Improve keybox_set_flags

* kbx/keybox-defs.h (struct keybox_handle): Add update_mode flag.
* kbx/keybox-init.c (_keybox_close_file): Clear update_mode flag.
* kbx/keybox-update.c (keybox_set_flags): Avoid a second file handle
but make use of the update mode.
--

This is mostly useful for gpgsm because it updates some flags in the
keyring quite often.  Avoiding extra CreateFile calls may help to
speed up things in case malware^Dantivirus software is slowing down a
Windows system.

The locking pattern also change, thus there is some regression risk
due to this patch.

3 files changed, 21 insertions, 5 deletions

diff --git a/kbx/keybox-defs.h b/kbx/keybox-defs.h
index 51ba8cd0e..32622a632 100644
--- a/kbx/keybox-defs.h
+++ b/kbx/keybox-defs.h
@@ -77,6 +77,7 @@ struct keybox_handle {
   KB_NAME kb;
   int secret;             /* this is for a secret keybox */
   estream_t fp;
+  int update_mode;        /* FP is in update mode ("r+b").  */
   int eof;
   int error;
   int ephemeral;
diff --git a/kbx/keybox-init.c b/kbx/keybox-init.c
index 48af5c7a1..a5b7baec0 100644
--- a/kbx/keybox-init.c
+++ b/kbx/keybox-init.c
@@ -255,6 +255,7 @@ _keybox_close_file (KEYBOX_HANDLE hd)
           {
             es_fclose (roverhd->fp);
             roverhd->fp = NULL;
+            roverhd->update_mode = 0;
           }
       }
   log_assert (!hd->fp);
diff --git a/kbx/keybox-update.c b/kbx/keybox-update.c
index 273265635..fd37ee5b3 100644
--- a/kbx/keybox-update.c
+++ b/kbx/keybox-update.c
@@ -509,6 +509,7 @@ keybox_set_flags (KEYBOX_HANDLE hd, int what, int idx, unsigned int value)
   size_t flag_pos, flag_size;
   const unsigned char *buffer;
   size_t length;
+  gpgrt_off_t save_off;
 
   (void)idx;  /* Not yet used.  */
 
@@ -535,11 +536,18 @@ keybox_set_flags (KEYBOX_HANDLE hd, int what, int idx, unsigned int value)
 
   off += flag_pos;
 
-  _keybox_close_file (hd);
-  fp = es_fopen (hd->kb->fname, "r+b");
-  if (!fp)
-    return gpg_error_from_syserror ();
+  if (!hd->fp || !hd->update_mode)
+    {
+      _keybox_close_file (hd);
+      fp = es_fopen (hd->kb->fname, "r+b");
+      if (!fp)
+        return gpg_error_from_syserror ();
+      hd->update_mode = 1;
+    }
+  else
+    fp = hd->fp;
 
+  save_off = es_ftello (fp);
   ec = 0;
   if (es_fseeko (fp, off, SEEK_SET))
     ec = gpg_err_code_from_syserror ();
@@ -566,12 +574,18 @@ keybox_set_flags (KEYBOX_HANDLE hd, int what, int idx, unsigned int value)
         }
     }
 
-  if (es_fclose (fp))
+  if (es_fflush (fp))
     {
       if (!ec)
         ec = gpg_err_code_from_syserror ();
     }
 
+  /* Get back to the last offset or close the file on error.  */
+  if (save_off == (gpgrt_off_t)(-1) || es_fseeko (fp, save_off, SEEK_SET))
+    {
+      _keybox_close_file (hd);
+    }
+
   return gpg_error (ec);
 }