(ITS#6768) NULL OldDN in modrdn operation kill slapd server

[sergeyfd@gmail.com]

Full_Name: Serge Dubrouski
Version: 2.4.23
OS: RedHat ES 5.5
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (208.30.65.103)


I ound that ldp.exe tool that comes with Windows is able to successfully kill
OpenLDAP 2.4.23 slapd server when one tries to modify DN and submits an empty
old DN. No binding is necessary so even anonymous user can easily run a DOS
attach against OpenLDAP. Log files in openldap show this:

Dec 29 15:19:32 ottawa slapd[11818]: conn=1000 op=2 do_modrdn
Dec 29 15:19:32 ottawa slapd[11818]: do_modrdn: dn () newrdn (C=US)
newsuperior ()
Dec 29 15:19:32 ottawa slapd[11818]: >>> dnPrettyNormal: <>
Dec 29 15:19:32 ottawa slapd[11818]: <<< dnPrettyNormal: <>, <>
Dec 29 15:19:32 ottawa slapd[11818]: >>> dnPrettyNormal: <C=US>
Dec 29 15:19:32 ottawa slapd[11818]: <<< dnPrettyNormal: <c=US>, <c=us>
Dec 29 15:19:32 ottawa slapd[11818]: conn=1000 op=2 MODRDN dn=""