Jason:
I think you misunderstand the role of Kerberos here. Kerberos is being
using to authenticate the user by name. If the SSH service is in realm
"A.EXAMPLE.COM" and the user is in realm "B.EXAMPLE.COM", the after
successful authentication the SSH service knows the name as something
like "[EMAIL PROTECTED]". The question that then must be answered is this:
Is [EMAIL PROTECTED] authorized to access this account on this
machine?
The answer to that question is an authorization decision and it is made
independently of the KDCs for A.EXAMPLE.COM. The default method
provided in the Kerberos libraries is to perform a lookup in a file
~/.k5login to see if the authenticated name is listed. You can replace
this mechanism with one of your own choosing but it requires that the
Kerberos function krb5_kuserok() not be used to make the authorization
decision by the application.
Jeffrey Altman
Jason Mogavero wrote:
> Ok, I should note that adding a .k5login file to the home directory of the
> user I want to log in as did work. However, this setup won't work for us in
> the long run.
>
> The ultimate goal is to have tech support reps be able to ssh into our
> multitude of hosted web servers to perform basic troubleshooting, but we
> have hundreds of servers and cannot reasonable manage that many local
> databases. The idea is to use sudo for priveleges (via sudo's LDAP
> support) and kerberos for authentication. Control over the user database
> needs to lie entirely within the AD, hence the need for authentication
> without the .k5login files. The non-Windows KDC needs to trust any user
> with Windows kerberos tickets, regardless of presence of a local account.
> Any suggestions as to how I might approach this?
>
>
>
> On 8/21/06, Jason Mogavero <[EMAIL PROTECTED]> wrote:
>> There is no .k5login file in the home directory...though the user account
>> does exist on the machine, eventually the user database is going be stored
>> on LDAP and there will not be individual user accounts on the ssh servers.
>>
>>
>> Shouldn't the ACL take precedence anyway? I don't have a .k5login in the
>> kdcadmin user's home directory and that one can authenticate just fine.
>> (albeit from a ticket granted by the non-windows kdc and not the AD and the
>> kdcadmin user principal is in the non-windows kerberos database)
>>
>> Is there some blanket way of telling the non-Windows kerberos service to
>> authenticate any principle @KDCTEST.COM? (the Windows KDC) I thought
>> the kadm5.acl would allow me to do that.
>>
>>
>>
>>
>> On 8/21/06, Douglas E. Engert <[EMAIL PROTECTED]> wrote:
>>> Do you have a .k5login file in the home directory on the
>>> machine with the sshd? It should list the principals that
>>> are allowed to access this unix account.
>>>
>>> Note the return codes from the mm_answer_gss_userok is 1 when it
>>> worked, 0 when it did not. So it looks like the gss authenticated you
>>> but the principal was not allowed to use the unix account.
>>>
>>>
>>>
>>> Jason Mogavero wrote:
>>>
>>>> Ok, I found part one of my problem, in that on the non-windows KDC I
>>> had
>>>> not
>>>> specified an encryption type and whatever is the default was not
>>> working
>>>> with the windows DC. I've fixed that and I can now get issued tickets
>>> by
>>>> the non-windows KDC. Here is the kdc.log entry for my ticket
>>> generation:
>>>> Aug 21 13:59:47 kdcdmz.kdctest.com krb5kdc[29511](info): TGS_REQ (5
>>> etypes
>>>> {23 3 1 24 -135}) 172.16.102.28: ISSUE: authtime 1156189823, etypes
>>> {rep=3
>>>> tkt=16 ses=1}, [EMAIL PROTECTED] for
>>>> host/[EMAIL PROTECTED]
>>>> Aug 21 13:59:47 kdcdmz.kdctest.com krb5kdc[29511](info): TGS_REQ (5
>>> etypes
>>>> {23 3 1 24 -135}) 172.16.102.28: ISSUE: authtime 1156189823, etypes
>>> {rep=3
>>>> tkt=16 ses=1}, [EMAIL PROTECTED] for
>>>> host/[EMAIL PROTECTED]
>>>>
>>>> However, GSSAPI is still failing. The logging in PuTTY shows a
>>> general
>>>> SSPI
>>>> failure, but nothing specific other than the ssh server is kicking
>>> back a
>>>> reject. (note that GSSAPI works on a Linux system that connects via
>>>> openssh
>>>> and is authenticated the the non-windows KDC)
>>>>
>>>> I ran sshd in debug mode, and compared the output from a rejected
>>> GSSAPI
>>>> session and an accepted one. Here is the accepted:
>>>>
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug1: Received some client
>>>> credentials
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_send entering:
>>> type
>>>> 41
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_receive
>>> entering
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: monitor_read: checking
>>> request
>>>> 44
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_send entering:
>>> type
>>>> 45
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_receive
>>> entering
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: monitor_read: checking
>>> request
>>>> 42
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: Authorized to kdcadmin, krb5
>>> principal
>>>> [EMAIL PROTECTED] (krb5_kuserok)
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_answer_gss_userok:
>>> sending
>>>> result 1
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_send entering:
>>> type
>>>> 43
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_receive_expect
>>>> entering: type 47
>>>> Aug 21 14:21:30 kdcvps1 sshd[19893]: debug3: mm_request_receive
>>> entering
>>>> Aug 21 14:21:31 kdcvps1 sshd[19893]: debug3: PAM: do_pam_account
>>>> pam_acct_mgmt = 0
>>>> Aug 21 14:21:31 kdcvps1 sshd[19893]: debug3: mm_request_send entering:
>>> type
>>>> 48
>>>> Aug 21 14:21:31 kdcvps1 sshd[19893]: Accepted gssapi-with-mic for
>>> kdcadmin
>>>> from 172.16.102.112 port 32957 ssh2
>>>>
>>>> And here is the failed one:
>>>>
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug1: Received some client
>>>> credentials
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_request_send entering:
>>> type
>>>> 41
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_request_receive
>>> entering
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: monitor_read: checking
>>> request
>>>> 44
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_request_send entering:
>>> type
>>>> 45
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_request_receive
>>> entering
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: monitor_read: checking
>>> request
>>>> 42
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_answer_gss_userok:
>>> sending
>>>> result 0
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: debug3: mm_request_send entering:
>>> type
>>>> 43
>>>> Aug 21 14:01:35 kdcvps1 sshd[19853]: Failed gssapi-with-mic for
>>>> jason.mogavero from 172.16.102.28 port 4292 ssh2
>>>>
>>>> So it seems that even though I am getting a tgt from the non-Windows
>>> KDC, I
>>>> am not being authorized by this "checking request 42" which I imagine
>>>> checks
>>>> against the non-Win KDC. I don't need to have every user in the
>>> Windows AD
>>>> in the non-Windows KDC user database as well, do I? I thought the
>>> point of
>>>> the one-way trust was to allow users authenticated in one realm to
>>> have
>>>> access to resources in another. Is this an ACL issue? I have an
>>> entry in
>>>> the kadm5.acl file on the non-windows KDC that says:
>>>>
>>>> [EMAIL PROTECTED] *
>>>>
>>>> Is not not correct syntax?
>>>>
>>>> On 8/18/06, Douglas E. Engert <[EMAIL PROTECTED]> wrote:
>>>>
>>>>>
>>>>>
>>>>> Jason Mogavero wrote:
>>>>>
>>>>>> Hello all,
>>>>>>
>>>>>> I am implementing a Kerberos/GSSAPI solution in a test
>>> environment
>>>>> and I
>>>>>> am experiencing some issues with allowed windows ssh clients to be
>>>>> granted
>>>>>> acess to the ssh server.
>>>>>>
>>>>>> The background:
>>>>>>
>>>>>> Windows AD is primary kdc with realm name KDCTEST.COM and hostname
>>>>>> adauth.kdctest.com
>>>>>> MIT kdc (on CentOS 4.3, installed from rpms) is DMZ.KDCTEST.COM
>>>>>>
>>>>>> ssh server is hostname kdcvps1.kdctest.com
>>>>>> ssh client (linux) is kdcvps2.kdctest.com
>>>>>> windows ssh client is kdctest01.kdctest.com
>>>>>>
>>>>>> I am able to passwordlessly log into the ssh server from the Linux
>>> ssh
>>>>>> client via gssapi. When I connect from PuTTY or SecureCRT in
>>> GSSAPI
>>>>> mode,
>>>>>> it fails. PuTTY prompts me for a password and SecureCRT errors out
>>>>> with
>>>>>> "All available GSSAPI mechanisms failed" Here is the kdc.log entry
>>> I
>>>>> get:
>>>>>
>>>>> Sounds like the cross realm keys are not setup correctly, i.e. the
>>> kvno
>>>>> key or enc types are different in AD and krb KDC for the
>>>>> krbtgt/[EMAIL PROTECTED] principal on both sides. You can
>>> use
>>>>> mmc
>>>>> and ADSIEdit to look at AD at the acocunt you created for the trust
>>> to
>>>>> see
>>>>> the key version number on 2003.
>>>>>
>>>>> You could use ethereal (wireshark) on Windows to watch the client
>>> contact
>>>>> the
>>>>> AD to get a cross realm ticket, then try and use it with the krb KDC
>>> to
>>>>> get
>>>>> the service ticket. It would show the kvno and enctypes being used.
>>>>>
>>>>> It could also be the keys don't match, because of the way they where
>>>>> generated from passwords on each side. I assume you used the 2003
>>> ktpass
>>>>> Getting a keytab with the out option could help identify problems
>>> too.
>>>>> ---snip--
>>>>> --
>>>>>
>>>>> Douglas E. Engert <[EMAIL PROTECTED]>
>>>>> Argonne National Laboratory
>>>>> 9700 South Cass Avenue
>>>>> Argonne, Illinois 60439
>>>>> (630) 252-5444
>>>>>
>>> --
>>>
>>> Douglas E. Engert <[EMAIL PROTECTED]>
>>> Argonne National Laboratory
>>> 9700 South Cass Avenue
>>> Argonne, Illinois 60439
>>> (630) 252-5444
>>>
>>
> ________________________________________________
> Kerberos mailing list Kerberos@mit.edu
> https://mailman.mit.edu/mailman/listinfo/kerberos
>
________________________________________________
Kerberos mailing list Kerberos@mit.edu
https://mailman.mit.edu/mailman/listinfo/kerberos
