Prevent winbind idmap corruption

[Michael Steffens]

Ooops, bug in patch: Duplicate deletion of mapping on
rollback. Corrected version is attached. Sorry!

Michael
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Index: nsswitch/winbindd_idmap.c
===================================================================
RCS file: /cvsroot/samba/source/nsswitch/winbindd_idmap.c,v
retrieving revision 1.3.4.13
diff -u -r1.3.4.13 winbindd_idmap.c
--- nsswitch/winbindd_idmap.c	27 Apr 2002 03:04:08 -0000	1.3.4.13
+++ nsswitch/winbindd_idmap.c	19 Dec 2002 12:32:25 -0000
@@ -44,6 +44,8 @@
 
     if ((hwm = tdb_fetch_int32(idmap_tdb, 
                              isgroup ? HWM_GROUP : HWM_USER)) == -1) {
+        DEBUG(0, ("Failed to fetch %s : %s\n", isgroup ? HWM_GROUP : HWM_USER,
+            tdb_errorstr(idmap_tdb)));
         return False;
     }
 
@@ -63,7 +65,45 @@
 
     /* Store new high water mark */
 
-    tdb_store_int32(idmap_tdb, isgroup ? HWM_GROUP : HWM_USER, hwm);
+    if (tdb_store_int32(idmap_tdb, isgroup ? HWM_GROUP : HWM_USER, hwm)) {
+        DEBUG(0, ("Failed to store %s %d : %s\n", isgroup ? HWM_GROUP : HWM_USER,
+            hwm, tdb_errorstr(idmap_tdb)));
+        return False;
+    }
+
+    return True;
+}
+
+/* Deallocate either a user or group id, used for failure rollback */
+
+static BOOL deallocate_id(uid_t id, BOOL isgroup)
+{
+    int hwm;
+
+    /* Get current high water mark */
+
+    if ((hwm = tdb_fetch_int32(idmap_tdb, 
+                             isgroup ? HWM_GROUP : HWM_USER)) == -1) {
+        DEBUG(0, ("Failed to fetch %s : %s\n", isgroup ? HWM_GROUP : HWM_USER,
+            tdb_errorstr(idmap_tdb)));
+        return False;
+    }
+
+    if (hwm != id + 1) {
+        /* Should actually never happen, internal redundancy... */
+        DEBUG(0, ("winbind %s mismatch on deallocation!\n", isgroup ? HWM_GROUP : HWM_USER));
+        return False;
+    }
+
+    hwm--;
+
+    /* Store new high water mark */
+
+    if (tdb_store_int32(idmap_tdb, isgroup ? HWM_GROUP : HWM_USER, hwm)) {
+        DEBUG(0, ("Failed to store %s %d : %s\n", isgroup ? HWM_GROUP : HWM_USER,
+           hwm, tdb_errorstr(idmap_tdb)));
+        return False;
+    }
 
     return True;
 }
@@ -109,16 +149,36 @@
             fstring keystr2;
 
             /* Store new id */
-            
+
             slprintf(keystr2, sizeof(keystr2), "%s %d", isgroup ? "GID" : "UID", *id);
 
             data.dptr = keystr2;
             data.dsize = strlen(keystr2) + 1;
 
-            tdb_store(idmap_tdb, key, data, TDB_REPLACE);
-            tdb_store(idmap_tdb, data, key, TDB_REPLACE);
+            /* If any of the following actions fails try to
+               revert modifications successfully made so far. */
 
             result = True;
+
+            if (result && tdb_store(idmap_tdb, key, data, TDB_REPLACE)) {
+                DEBUG(0, ("Failed to store id mapping %s:%s : %s\n",
+                          key.dptr, data.dptr, tdb_errorstr(idmap_tdb)));
+
+                if (!deallocate_id(*id, isgroup))
+                    DEBUG(0, ("Failed to rollback id mapping\n"));
+
+                result = False;
+            }
+
+            if (result && tdb_store(idmap_tdb, data, key, TDB_REPLACE)) {
+                DEBUG(0, ("Failed to store reverse id mapping %s:%s : %s\n",
+                          data.dptr, key.dptr, tdb_errorstr(idmap_tdb)));
+
+                if (!deallocate_id(*id, isgroup) || tdb_delete(idmap_tdb, key))
+                    DEBUG(0, ("Failed to rollback id mapping\n"));
+
+                result = False;
+            }
         }
     }