This bug was fixed in the package cyrus-sasl2 - 2.1.27+dfsg2-3ubuntu1.1
---------------
cyrus-sasl2 (2.1.27+dfsg2-3ubuntu1.1) jammy; urgency=medium
* Add SASL channel binding support for GSSAPI and GSS-SPNEGO
(LP: #1912256):
- d/p/0034-channel-binding-gssapi-gss-spnego.patch: add SASL channel
binding support for GSSAPI and GSS-SPNEGO
- d/p/0035-Add-support-for-setting-max-ssf-0-to-GSS-SPNEGO-1.patch:
allow setting maxssf to 0 when using GSS-SPNEGO inside SSL/TLS
- d/p/0035-Add-support-for-setting-max-ssf-0-to-GSS-SPNEGO-2.patch:
be more conformant to RFC4752
* Add some DEP8 tests (LP: #1677781):
- d/t/{control,saslauthd}: saslauthd tests with multiple mechanisms
- d/t/{control,gssapi}: test for SASL GSSAPI using OpenLDAP
- d/t/{control,pluginviewer}: test available mechanisms
- d/t/{control,shared-secret-mechs}: test shared secret mechanisms
-- Lena Voytek <[email protected]> Wed, 19 Oct 2022 14:06:40
-0700
** Changed in: cyrus-sasl2 (Ubuntu Jammy)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1912256
Title:
Missing channel binding prevents authentication to ActiveDirectory
Status in cyrus-sasl2 package in Ubuntu:
Fix Released
Status in openldap package in Ubuntu:
Fix Released
Status in cyrus-sasl2 source package in Jammy:
Fix Released
Status in openldap source package in Jammy:
Fix Released
Bug description:
[Impact]
When attempting to authenticate against a Windows Active Directory
server configured to require SASL channel binding over SSL/TLS ldap
connections (ldaps), authentication will fail stating invalid
credentials as the cause.
This is due to cyrus-sasl2 missing the sasl channel binding feature of
GSSAPI/GSS-SPNEGO.
Furthermore, for interoperability with Windows Active Directory
Server, it's necessary to be able to set the SASL SSF (security
strength factor) to 0 (zero) when it's used over an already encrypted
connection like ldaps.
To fix these issues, these items are added as patches from a set of
upstream commits.
[Test Plan]
To reproduce this issue, a machine running Windows with Active
Directory must be available over the network. As an example, for
Windows Server 2019 Evaluation:
The ISO can be downloaded from
https://www.microsoft.com/en-us/evalcenter/download-windows-server-2019
Install Windows Server, Active Directory, and Certificate Services, then add
the following registry changes from
https://support.microsoft.com/en-us/topic/2020-ldap-channel-binding-and-ldap-signing-requirements-for-windows-kb4520412-ef185fb8-00f7-167d-744c-f299a66fc00a
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters]
"ldapserverintegrity"=dword:00000002
"LdapEnforceChannelBinding"=dword:00000002
Also enable LDAP logging for Active Directory:
Reg Add
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Diagnostics
/v "16 LDAP Interface Events" /t REG_DWORD /d 2
With the Windows machine available, set up an Ubuntu system on a
network that can reach the Windows server. This works best and with
less configuration needed if the Windows server is acting as DNS and
DHCP server for that network.
Install packages with:
$ sudo apt install ldap-utils libsasl2-modules-gssapi-mit krb5-user
When the Configuring Kerberos Authentication prompt shows up, use the realm
of the Windows Server. If prompted, use the windows server IP for the Kerberos
KDC and admin servers.
Save the Windows Server AD CA certificate file as
/usr/local/share/ca-certificates/ad-ca.crt then run
$ sudo update-ca-certificates
In /etc/ldap/ldap.conf set
BASE dc={REALM NAME} # split the domain components like dc=example,dc=com
URI ldaps://{WINDOWS SERVER MACHINE NAME}.{REALM NAME}
With Ubuntu set up, the actual test can be run:
$ kinit
Enter Password
$ ldapwhoami -Y GSSAPI -O maxssf=0 -o SASL_CBINDING=tls-endpoint
Prior to the fix, this would display the following:
SASL/GSSAPI authentication started
ldap_sasl_interactive_bind_s: Invalid credentials (49)
additional info: 80090346: LdapErr: DSID-..., comment:
AcceptSecurityContext error, data 80090346, v4563
With the fix, the authentication will display the user information.
The same happens with
$ ldapwhoami -Y GSS-SPNEGO -O maxssf=0 -o SASL_CBINDING=tls-endpoint
SASL/GSS-SPNEGO authentication started
ldap_sasl_interactive_bind_s: Invalid credentials (49)
additional info: 80090346: LdapErr: DSID-..., comment:
AcceptSecurityContext error, data 80090346, v4563
[Where problems could occur]
Based on the patches added, any problems that show up would likely
occour either in the gssapi plugin or the SASL2 macros. The two files
changed are plugins/gssapi.c and m4/sasl2.m4, along with some tests.
There are various situations apart from this one in which GSS-API can
be used, and this change may affect the way some of these interactions
over the network are handled.
In parallel with this SRU, we tested, in jammy, cyrus-imapd server and
gssapi authentication over tls, with and without this updated sasl
package. Using as a client thunderbird, imtest (from cyrus-imapd-
clients), curl (it has imap support), mutt, evolution. All
authenticated without issues. Also postfix with gssapi authentication
was tested, and also worked.
[Other Info]
This issue was fixed in kinetic in version 2.1.28+dfsg-6ubuntu2
This SRU is also pulling in the new DEP8 tests in the kinetic package
for cyrus-sasl2. The only changes made to those tests are the list of
mechanisms to test, which is slightly smaller in jammy, and an extra
package to install for one of the tests due to packaging differences
in jammy wrt kinetic.
[Original Description]
> Are you uncertain if your issue is really a bug?
Effect is an authentication error. Root case is a "missing feature" (see
below) and requires updating dependencies, downporting.
> If you are certain this is a bug please include the source package the bug
is in.
It's in the interaction between three libraries: openldap, cyrus-sasl, krb5
> 1) The release of Ubuntu you are using, via 'lsb_release -rd' or System ->
About Ubuntu
Broken in 18.04 and also in 20.10 (I guess it's also broken in anything
inbetween)
> 2) The version of the package you are using, via 'apt-cache policy
pkgname' or by checking in Software Center
libsasl2-modules-gssapi-mit: 2.1.27+dfsg-2ubuntu1
ldap-utils: 2.4.53+dfsg-1ubuntu1.2
libgssapi-krb5-2: 1.17-10ubuntu0.1
> 3) What you expected to happen
# kinit
$ export LDAPSASL_CBINDING=tls-endpoint
$ ldapwhoami -O minssf=0,maxssf=0 -N -Y GSSAPI -H ldaps://<DC-fqdn>
SASL/GSSAPI authentication started
SASL username: <some-username>
SASL SSF: 0
u:<some-username>
> 4) What happened instead
SASL/GSSAPI authentication started
ldap_sasl_interactive_bind_s: Invalid credentials (49)
additional info: 80090346: LdapErr: DSID-0C090597, comment:
AcceptSecurityContext error, data 80090346, v4563
---------------
Microsoft ActiveDirectory has "LDAP Channel Binding" and recommends
activating this as a required feature. See
https://access.redhat.com/articles/4661861
Authentication to any AD DC which has mandatory channel binding fails.
Channel binding requires at least an update to cyrus-sasl, which is
not in any release as far as I can see:
https://github.com/cyrusimap/cyrus-
sasl/commit/975edbb69070eba6b035f08776de771a129cfb57
It also needs this commit in openldap:
https://git.openldap.org/openldap/openldap/-/commit/3cd50fa8b32a21040a9892e2a8a7a9dfc7541ce6
Which as far as I can tell is v2.5 (branch OPENLDAP_REL_ENG_2_5).
RH also mentions it needs up-to-date krb5 libraries, but I can't tell
what minimum version this needs.
I can build all libraries from source, current master (except for krb5
where I've used 1.18.3) and can confirm that channel binding works
when using those libraries.
I'm not sure if Samba is affected, but at least adcli, ldap-utils, and
I would guess by extension also SSSD and realmd.
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