On 2016-10-12 12:02, Aki Tuomi wrote:
On 12.10.2016 10:27, Juha Koho wrote:
On 2016-10-11 12:10, Juha Koho wrote:
On 2016-10-11 11:03, Aki Tuomi wrote:
On 11.10.2016 11:56, Juha Koho wrote:
On 2016-10-11 10:00, Aki Tuomi wrote:
On 11.10.2016 10:43, Juha Koho wrote: > > On 2016-10-11 09:18, Aki Tuomi wrote: >> On 11.10.2016 10:13, Juha Koho wrote: >>> Hello, >>> >>> I have a Dovecot 2.2.25 set up with OpenLDAP back end. I was >>> trying to >>> set up a GSSAPI Kerberos authentication with the LDAP server >>> but with >>> little success. Seems no matter what I try I end up with the >>> following >>> error message: >>> >>> dovecot: auth: Error: LDAP: binding failed (dn >>> (imap/host.example.com@EXAMPLE.COM)): Local error, SASL(-1): >>> generic >>> failure: GSSAPI Error: Unspecified GSS failure. Minor code may >>> provide more information (No Kerberos credentials available >>> (default >>> cache: FILE:/tmp/dovecot.krb5.ccache)) >>> >>> I have set the import_environment in dovecot.conf: >>> >>> import_environment = TZ CORE_OUTOFMEM CORE_ERROR LISTEN_PID >>> LISTEN_FDS >>> KRB5CCNAME=FILE:/tmp/dovecot.krb5.ccache >>> >>> And these in LDAP configuration: >>> >>> dn = imap/host.example.com@EXAMPLE.COM >>> sasl_bind = yes >>> sasl_mech = gssapi >>> sasl_realm = EXAMPLE.COM >>> sasl_authz_id = imap/host.example.com@EXAMPLE.COM >>> >>> I have tried with different values in dn and sasl_authz_id and >>> also >>> leaving them out completely but I always end up with the error >>> message >>> above. Using simple bind without GSSAPI works just fine. >>> >>> The credentials cache file exists and is valid for the >>> principal >>> imap/host.example.com@EXAMPLE.COM. The file is owned by dovecot >>> user >>> so it shouldn't be a permission problem either. >>> >>> GSSAPI in OpenLDAP works but I suppose it is irrelevant here >>> since >>> the >>> connection attempt never reaches the LDAP server due to the >>> error. I >>> also have similar setup for Postfix and it works fine. >>> >>> Any ideas what to try next? >>> >>> Best regards, >>> Juha >> >> Can you provide klist output for the cache file? Also, it should >> be >> readable by dovenull user, or whatever is configured as >> default_login_user. > > > Here's the klist output of the cache file: > -- > Ticket cache: FILE:/tmp/dovecot.krb5.ccache > Default principal: imap/host.example.com@EXAMPLE.COM > > Valid starting Expires Service principal > 10/11/2016 09:26:25 10/11/2016 21:26:25 > krbtgt/EXAMPLE.COM@EXAMPLE.COM > renew until 10/12/2016 09:26:25 > --- > > That I didn't know that also dovenull must have access to the > cache > but I tried also setting 0644 permissions to the cache file with > no > luck. So permissions shouldn't be the issue... > > Juha
Your ccache has no ticket for imap/host.example.com@EXAMPLE.COM
please use kinit to acquire one.
Now I'm confused. The cache file is created by kinit using the command:
sudo -u dovenull kinit -c FILE:/tmp/dovecot.krb5.ccache -k -t /path/to/keytab imap/host.example.com
After that:
$ sudo -u dovenull klist /tmp/dovecot.krb5.ccache Ticket cache: FILE:/tmp/dovecot.krb5.ccache Default principal: imap/host.example.com@EXAMPLE.COM
Valid starting Expires Service principal 10/11/2016 10:47:47 10/11/2016 22:47:47 krbtgt/EXAMPLE.COM@EXAMPLE.COM renew until 10/12/2016 10:47:47
Also, I can use the cache file with ldapsearch just fine by running the following:
sudo -u dovenull KRB5CCNAME=FILE:/tmp/dovecot.krb5.ccache ldapsearch -Y GSSAPI -ZZ -H ldap://ldap.example.com/ -b dc=example,dc=com
After the ldapsearch has succeeded the klist output is the following:
$ sudo -u dovenull klist /tmp/dovecot.krb5.ccache Ticket cache: FILE:/tmp/dovecot.krb5.ccache Default principal: imap/host.example.com@EXAMPLE.COM
Valid starting Expires Service principal 10/11/2016 10:47:47 10/11/2016 22:47:47 krbtgt/EXAMPLE.COM@EXAMPLE.COM renew until 10/12/2016 10:47:47 10/11/2016 10:49:32 10/11/2016 22:47:47 ldap/ldap.example.com@EXAMPLE.COM renew until 10/12/2016 10:47:47
Which is what I expected. Isn't this basically what dovecot does (or should do) or did I miss something?
Juha
Dovecot won't acquire service tickets for you. It requires that you have ticket for imap/imap.example.com@EXAMPLE.COM in the cache or keytab.
The default principal is used when *CONNECTING* to a service, but you are *ACCEPTING* a service, so you need a service principal.
Aki
Sorry, all this Kerberos stuff is quite new to me and I'm still a bit confused... :) What I still fail to understand is why would I need the service principal in the cache since I'm trying to set dovecot to use GSSAPI when connecting to the LDAP back end for passdb and userdb lookups.
My imap users can connect to Dovecot using GSSAPI without problems. This isn't the issue. Dovecot being the client to the LDAP service is the issue.
But anyway, after adding the ticket for imap/host.example.com@EXAMPLE.COM in the cache the error still remains:
dovecot: auth: Error: LDAP: binding failed (dn imap/host.example.com@EXAMPLE.COM): Local error, SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (No Kerberos credentials available (default cache: FILE:/tmp/dovecot.krb5.ccache))
$ sudo -u dovenull klist /tmp/dovecot.krb5.ccache Ticket cache: FILE:/tmp/dovecot.krb5.ccache Default principal: imap/host.example.com@EXAMPLE.COM
Valid starting Expires Service principal 10/11/2016 11:00:50 10/11/2016 23:00:50
krbtgt/EXAMPLE.COM@EXAMPLE.COM renew until 10/12/2016 11:00:50 10/11/2016 11:19:09 10/11/2016 23:00:50 imap/host.example.com@ renew until 10/12/2016 11:00:50 10/11/2016 11:19:09 10/11/2016 23:00:50 imap/host.example.com@EXAMPLE.COM renew until 10/12/2016 11:00:50Juha
Just to let anyone interested know the configuration was correct but this turned out to be some sort of library incompatibility or whatever.
I cloned the configuration to a new virtual server and compiled a fresh copy of Dovecot from source (tried git master and release-2.2.25) and it worked without problems.
I also noticed that with the freshly compiled version the error message changed to
dovecot: auth: Error: LDAP: binding failed (dn (none)): Local error, SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (No Kerberos credentials available: Credentials cache permissions incorrect (filename: /tmp/dovecot.krb5.ccache))
if the permissions of the cache file were incorrect instead of this general error message above. So seems like the issue - whatever it was
- caused that Dovecot (or the underlying libraries) were unable to locate or open the cache file in the first place.
Juha
I think it requires that the file is readable only by the user, so setting if 0644 was probably a mistake.
Aki
No, this isn't the case. In the new test environment where things work it doesn't care about the cache file permissions as long as it can read the file.
I just noticed the error when I mistakenly had created the cache file as root and therefore it wasn't readable by Dovecot.
Juha