[STS-SPONSOR]
* Was it intentional to add the patchset at the bottom of the quilt
stack in the SSSD src package ?
If not, could you please correct it and add them at the top of the stack
? At first glance, they should still apply cleanly after that chane.
* I came accross this change in adcli:
76ca1e6737742208d83e016d43a3379e378f8d90
76ca1e6 tools: add missing use-ldaps option to update and testjoin
When adding the use-ldaps option the update and testjoin sub-commands
were forgotten.
https://gitlab.freedesktop.org/realmd/adcli/-/commit/76ca1e6737742208d83e016d43a3379e378f8d90
Did/could you check the feasibility of a backport ?
Look like it's worth looking at this oversight from upstream that has been then
fixed later.
** Description changed:
[Impact]
Microsoft has released a new security advisory for Active Directory (AD)
which outlines that man-in-the-middle attacks can be performed on a LDAP
server, such as AD DS, that works by an attacker forwarding an
authentication request to a Windows LDAP server that does not enforce
LDAP channel binding or LDAP signing for incoming connections.
To address this, Microsoft has announced new Active Directory
requirements in ADV190023 [1][2].
[1] https://msrc.microsoft.com/update-guide/en-us/vulnerability/ADV190023
[2]
https://support.microsoft.com/en-us/help/4520412/2020-ldap-channel-binding-and-ldap-signing-requirements-for-windows
These new requirements strongly encourage system administrators to
require LDAP signing and authenticated channel binding in their AD
environments.
The effects of this is to stop unauthenticated and unencrypted traffic
from communicating over LDAP port 389, and to force authenticated and
encrypted traffic instead, over LDAPS port 636 and Global Catalog port
3629.
Microsoft will not be forcing this change via updates to their servers,
system administrators must opt in and change their own configuration.
To support these new requirements in Ubuntu, changes need to be made to
the sssd and adcli packages. Upstream have added a new flag
"ad_use_ldaps" to sssd, and "use-ldaps" has been added to adcli.
If "ad_use_ldaps = True", then sssd will send all communication over
port 636, authenticated and encrypted.
For adcli, if the server supports GSS-SPNEGO, it will be now be used by
default, with the normal LDAP port 389. If the LDAP port is blocked,
then "use-ldaps" can now be used, which will use the LDAPS port 636
instead.
+ This is currently reporting the following on Ubuntu 18.04/20.04LTS
+ machines with the following error:
+
+ "[sssd] [sss_ini_call_validators] (0x0020):
+ [rule/allowed_domain_options]: Attribute 'ad_use_ldaps' is not allowed
+ in section 'domain/cp.pacs'. Check for typos."
+
These patches are needed to stay in line with Microsoft security
advisories, since security conscious system administrators would like to
firewall off the LDAP port 389 in their environments, and use LDAPS port
636 only.
[Testcase]
To test these changes, you will need to set up a Windows Server 2019
box, install and configure Active Directory, import the AD certificate
to the Ubuntu clients, and create some users in Active Directory.
From there, you can try do a user search from the client to the AD
server, and check what ports are used for communication.
Currently, you should see port 389 in use:
$ sudo netstat -tanp |grep sssd
tcp 0 0 x.x.x.x:43954 x.x.x.x:389 ESTABLISHED 27614/sssd_be
- tcp 0 0 x.x.x.x:54381 x.x.x.x:3268 ESTABLISHED 27614/sssd_be
+ tcp 0 0 x.x.x.x:54381 x.x.x.x:3268 ESTABLISHED 27614/sssd_be
Test packages are available in the following ppa:
https://launchpad.net/~mruffell/+archive/ubuntu/sf294530-test
Instructions to install (on a bionic or focal system):
1) sudo add-apt-repository ppa:mruffell/sf294530-test
2) sudo apt update
3) sudo apt install adcli sssd
Then, modify /etc/sssd/sssd.conf and add "ad_use_ldaps = True", restart
sssd.
Add a firewall rule to block traffic to LDAP port 389 and Global Catalog
3268.
$ sudo ufw deny 389
$ sudo ufw deny 3268
Then do another user lookup, and check ports in use:
$ sudo netstat -tanp |grep sssd
tcp 0 0 x.x.x.x:44586 x.x.x.x:636 ESTABLISHED 28474/sssd_be
- tcp 0 0 x.x.x.x:56136 x.x.x.x:3269 ESTABLISHED 28474/sssd_be
+ tcp 0 0 x.x.x.x:56136 x.x.x.x:3269 ESTABLISHED 28474/sssd_be
We see LDAPS port 636, and Global Catalog port 3629 in use. The user
lookup will succeed even with ports 389 and 3268 blocked, since it uses
their authenticated and encrypted variants instead.
[Where problems could occur]
Firstly, the adcli and sssd packages will continue to work with AD
servers that haven't had LDAP signing or authenticated channel binding
enforced, due to the measures being optional.
For both sssd and adcli, the changes don't implement anything new, and
instead, the changes add configuration and logic to "select" what
protocol to use to talk to the AD server. LDAP and LDAPS are already
implemented in both sssd and adcli, the changes just add some logic to
select the use of LDAPS over LDAP.
For sssd, the changes are hidden behind configuration parameters, such
as "ldap_sasl_mech" and "ad_use_ldaps". If a regression were to occur,
it would be limited to systems where the system administrator had
enabled these configuration options to the /etc/sssd/sssd.conf file.
For adcli, the changes are more immediate. adcli will now use GSS-SPENGO
by default if the server supports it, which is a behaviour change. The
"use-ldaps" option is a flag on the command line, e.g. "--use-ldaps",
and if a regression were to occur, users can remove "--use-ldaps" from
their command to fall back to the new GSS-SPENGO defaults on port 389.
The risk of regression is low, due to these features being opt-in via
command line flags and configuration parameters, which would likely be
well tested by a system administrator in their own AD environment before
they roll changes out to their production systems. There is some risk
with adcli moving to GSS-SPENGO by default, but this happens only if the
server supports it, and the change should be safe.
[Other Info]
Previous description, including FFe for adcli in Groovy:
https://paste.ubuntu.com/p/jpQ3FprJDx/
List of commits backported are below:
adcli
=====
For both Bionic and Focal:
--------------------------
commit a6f795ba3d6048b32d7863468688bf7f42b2cafd
Author: Sumit Bose <sb...@redhat.com>
Date: Fri Oct 11 16:39:25 2019 +0200
Subject: Use GSS-SPNEGO if available
Link:
https://gitlab.freedesktop.org/realmd/adcli/-/commit/a6f795ba3d6048b32d7863468688bf7f42b2cafd
commit 85097245b57f190337225dbdbf6e33b58616c092
Author: Sumit Bose <sb...@redhat.com>
Date: Thu Dec 19 07:22:33 2019 +0100
Subject: add option use-ldaps
Link:
https://gitlab.freedesktop.org/realmd/adcli/-/commit/85097245b57f190337225dbdbf6e33b58616c092
sssd
====
Bionic only (dependency)
------------------------
commit 070f22f896b909c140ed7598aed2393d61a834ae
Author: Sumit Bose <sb...@redhat.com>
Date: Tue May 21 10:22:04 2019 +0200
Subject: sdap: inherit SDAP_SASL_MECH if not set explicitly
Link:
https://github.com/SSSD/sssd/commit/070f22f896b909c140ed7598aed2393d61a834ae
For Bionic and Focal:
---------------------
commit 090cf77a0fd5f300a753667658af3ed763a88e83
Author: Sumit Bose <sb...@redhat.com>
Date: Thu Sep 26 20:24:34 2019 +0200
Subject: ad: allow booleans for ad_inherit_opts_if_needed()
Link:
https://github.com/SSSD/sssd/commit/090cf77a0fd5f300a753667658af3ed763a88e83
commit 341ba49b0deb42e17d535744824786c2499656b7
Author: Sumit Bose <sb...@redhat.com>
Date: Thu Sep 26 20:27:09 2019 +0200
Subject: ad: add ad_use_ldaps
Link:
https://github.com/SSSD/sssd/commit/341ba49b0deb42e17d535744824786c2499656b7
commit 78649907b81b4bdaf8fc6a6e6ae55ed3cd5419f5
Author: Sumit Bose <sb...@redhat.com>
Date: Fri Sep 27 11:49:59 2019 +0200
Subject: ldap: add new option ldap_sasl_maxssf
Link:
https://github.com/SSSD/sssd/commit/78649907b81b4bdaf8fc6a6e6ae55ed3cd5419f5
commit 24387e19f065e6a585b1120d5568cb4df271d102
Author: Sumit Bose <sb...@redhat.com>
Date: Fri Sep 27 13:45:13 2019 +0200
Subject: ad: set min and max ssf for ldaps
Link:
https://github.com/SSSD/sssd/commit/24387e19f065e6a585b1120d5568cb4df271d102
--
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https://bugs.launchpad.net/bugs/1868703
Title:
Support "ad_use_ldaps" flag for new AD requirements (ADV190023)
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