samba update

A security issue affects these releases of Ubuntu and its
derivatives:

* Ubuntu 20.04 LTS
* Ubuntu 18.04 LTS
* Ubuntu 16.04 LTS

Summary

Several security improvements were added to Samba.

Software Description

* samba - SMB/CIFS file, print, and login server for Unix

Details

Tom Tervoort discovered that the Netlogon protocol implemented by
Samba incorrectly handled the authentication scheme. A remote
attacker could use this issue to forge an authentication token and
steal the credentials of the domain admin.

While a previous security update fixed the issue by changing the
"server schannel" setting to default to "yes", instead of "auto",
which forced a secure netlogon channel, this update provides
additional improvements.

For compatibility reasons with older devices, Samba now allows
specifying an insecure netlogon configuration per machine. See the
following link for examples:
https://www.samba.org/samba/security/CVE-2020-1472.html

In addition, this update adds additional server checks for the
protocol attack in the client-specified challenge to provide some
protection when `server schannel = no/auto' and avoid the
false-positive results when running the proof-of-concept exploit.

Update instructions

The problem can be corrected by updating your system to the
following package versions:

Ubuntu 20.04 LTS
samba - 2:4.11.6+dfsg-0ubuntu1.5

Ubuntu 18.04 LTS
samba - 2:4.7.6+dfsg~ubuntu-0ubuntu2.20

Ubuntu 16.04 LTS
samba - 2:4.3.11+dfsg-0ubuntu0.16.04.31

To update your system, please follow these instructions:
https://wiki.ubuntu.com/Security/Upgrades.

In general, a standard system update will make all the necessary
changes.

References

* CVE-2020-1472

--- Mystic BBS v1.12 A46 (Linux/64)
* Origin: BZ&BZ BBS (21:4/110)