samba4: security bump to version 4.9.3

samba4: security bump to version 4.9.3

Fixes the following security vulnerabilities:

 - CVE-2018-14629:
   All versions of Samba from 4.0.0 onwards are vulnerable to infinite
   query recursion caused by CNAME loops. Any dns record can be added via
   ldap by an unprivileged user using the ldbadd tool, so this is a
   security issue.

 - CVE-2018-16841:
   When configured to accept smart-card authentication, Samba's KDC will call
   talloc_free() twice on the same memory if the principal in a validly signed
   certificate does not match the principal in the AS-REQ.

   This is only possible after authentication with a trusted certificate.

   talloc is robust against further corruption from a double-free with
   talloc_free() and directly calls abort(), terminating the KDC process.

   There is no further vulnerability associated with this issue, merely a
   denial of service.

 - CVE-2018-16851:
   During the processing of an LDAP search before Samba's AD DC returns
   the LDAP entries to the client, the entries are cached in a single
   memory object with a maximum size of 256MB.  When this size is
   reached, the Samba process providing the LDAP service will follow the
   NULL pointer, terminating the process.

   There is no further vulnerability associated with this issue, merely a
   denial of service.

 - CVE-2018-16852:
   During the processing of an DNS zone in the DNS management DCE/RPC server,
   the internal DNS server or the Samba DLZ plugin for BIND9, if the
   DSPROPERTY_ZONE_MASTER_SERVERS property or DSPROPERTY_ZONE_SCAVENGING_SERVERS
   property is set, the server will follow a NULL pointer and terminate.

   There is no further vulnerability associated with this issue, merely a
   denial of service.

 - CVE-2018-16853:
   A user in a Samba AD domain can crash the KDC when Samba is built in the
   non-default MIT Kerberos configuration.

   With this advisory we clarify that the MIT Kerberos build of the Samba
   AD DC is considered experimental.  Therefore the Samba Team will not
   issue security patches for this configuration.

 - CVE-2018-16857:
   AD DC Configurations watching for bad passwords (to restrict brute forcing
   of passwords) in a window of more than 3 minutes may not watch for bad
   passwords at all.

For more details, see the release notes:

https://www.samba.org/samba/history/samba-4.9.3.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>