CVE-2021-20277 ldb/attrib_handlers casefold: stay in bounds

For a string that had N spaces at the beginning, we would
try to move N bytes beyond the end of the string.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14655

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
(cherry-picked from commit for master)

diff --git a/lib/ldb/common/attrib_handlers.c b/lib/ldb/common/attrib_handlers.c
index b5212b7315964f1a60a3c74aeb10b621a329b141..c6ef5ad477b018a6c3c4cdab187c98e8c2389f24 100644 (file)
--- a/lib/ldb/common/attrib_handlers.c
+++ b/lib/ldb/common/attrib_handlers.c
@@ -76,7 +76,7 @@ int ldb_handler_fold(struct ldb_context *ldb, void *mem_ctx,
        
        /* remove leading spaces if any */
        if (*s == ' ') {
-               for (t = s; *s == ' '; s++) ;
+               for (t = s; *s == ' '; s++, l--) ;
 
                /* remove leading spaces by moving down the string */
                memmove(t, s, l);