[Freeipa-users] Ghost ipaSshPubKey in sss_ssh_authorizedkeys or 'Error looking up public keys'

Tue Jun 21 11:23:11 UTC 2016

On 6/21/2016 1:16 PM, Sumit Bose wrote:
> On Tue, Jun 21, 2016 at 12:43:23PM +0200, Martin Štefany wrote:
>> Hello Sumit,
>>
>> putting SELinux to permissive mode and/or enabling nis_enabled seboolean
>> seemed not help at all. And you are right, my user has userCertificate
>> (needed for secure libvirtd connection).
>>
>>
>> [martin at desk2 ~]$ sss_ssh_authorizedkeys  martin
>> Error looking up public keys
>> [martin at desk2 ~]$ sudo setenforce 0
>> [sudo] password for martin:
>> [martin at desk2 ~]$ sss_ssh_authorizedkeys  martin
>> Error looking up public keys
>> [martin at desk2 ~]$ sudo setsebool nis_enabled on
>> [martin at desk2 ~]$ sss_ssh_authorizedkeys  martin
>> Error looking up public keys
>> [martin at desk2 ~]$ sudo sss_cache -E
>> [martin at desk2 ~]$ sss_ssh_authorizedkeys martin
>> Error looking up public keys
>>
>> [have a coffee... really]
>>
>> [martin at desk2 ~]$ sss_ssh_authorizedkeys martin
>> ssh-rsa AAA...
>> ssh-rsa AAA...
>> ssh-ed25519 AAA...
>> ssh-rsa AAA...
>> ssh-rsa AAA...
>
> If I understand it correctly you get the same result as on CentOS,
> including the unexpected key derived from the certificate, after waiting
> for some time? Can you send the sssd_ssh.log with the sequence from
> above (if you prefer directly to me) so that I can check why it failed
> in the first attempt and later succeeds.
>
> bye,
> Sumit
>

Hi,

yes, now the results are the same, including the originally unexpected 
key from certificate, and actual SSH pubkey auth finally works.

I would send you sssd_ssh.log, but it's empty - I have turned off 
debug_level sooner, sorry. :(

Isn't it the case that sss_cache -E takes few seconds to actually expire 
the cache entries?

Thank you.
Martin

>>
>>
>> RH bug for selinux-policy:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1348447
>>
>> Thank you!
>> Martin
>>
>>
>> On 6/21/2016 9:43 AM, Sumit Bose wrote:
>>> On Mon, Jun 20, 2016 at 10:46:13PM +0200, Martin Štefany wrote:
>>>> Hello all,
>>>>
>>>> I've ran into strange issue with IPA/SSSD/SSH/SELinux which started when I
>>>> figured out that I cannot ssh with pubkey auth to Fedora 23 (ipa-client) systems
>>>> while I can to CentOS 7.2 (ipa-client and ipa-server) systems within same IPA
>>>> domain. I will appreciate any help whatsoever.
>>>> IPA servers (and most of the clients) are IPA 4.2.0 on CentOS 7.2 with latest
>>>> updates, affected clients are IPA clients 4.2.4 on Fedora 23 with latest
>>>> updates.
>>>>
>>>> I started by looking to the journal:
>>>> jún 20 13:02:50 desk2.stefany.eu sshd[25162]: Connection
>>>> from 144.xxx.xxx.xxx port 22543 on 172.17.100.191 port 22
>>>> ...
>>>> jún 20 13:02:56 desk2.stefany.eu audit[23328]: AVC avc:  denied  { name_connect
>>>> } for  pid=23328 comm="sssd_ssh" dest=80 scontext=system_u:system_r:sssd_t:s0
>>>> tcontext=system_u:object_r:http_port_t:s0 tclass=tcp_socket permissive=0
>>>> jún 20 13:02:56 desk2.stefany.eu audit[23328]: SYSCALL arch=c000003e syscall=42
>>>> success=no exit=-13 a0=15 a1=7fff145c35b0 a2=10 a3=5614dbbe2a50 items=0
>>>> ppid=23316 pid=23328 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0
>>>> sgid=0
>>>
>>> Does the user by chance have a certificate added to his entry including
>>> a link to an OCSP responder?
>>>
>>> Recent version of SSSD have the ability to generate public ssh-keys from
>>> valid certificates added to the user entry to support the ssh Smartcard
>>> feature (see e.g. the -I option in the ssh man page for details or
>>> https://fedorahosted.org/sssd/wiki/DesignDocs/SmartcardAuthenticationStep1#RunningsshclientwithSmartcardsupport)
>>>
>>> While trying to validate thecertificate via OCSP sssd_ssh must connect
>>> to a http server. To allow this setting the 'nis_enabled' SELinux
>>> boolean to true should help.
>>>
>>> Nevertheless, since this should work by default, it would be nice if you
>>> can open a bugzilla ticket for the SELinux policy on F23 to allow this
>>> by default.
>>>
>>> HTH
>>>
>>> bye,
>>> Sumit
>>>
>>>> ...
>>>> jún 20 13:02:56 desk2.stefany.eu audit[23328]: AVC avc:  denied  { name_connect
>>>> } for  pid=23328 comm="sssd_ssh" dest=80 scontext=system_u:system_r:sssd_t:s0
>>>> tcontext=system_u:object_r:http_port_t:s0 tclass=tcp_socket permissive=0
>>>> jún 20 13:02:56 desk2.stefany.eu audit[23328]: SYSCALL arch=c000003e syscall=42
>>>> success=no exit=-13 a0=15 a1=7fff145c35b0 a2=10 a3=5614dbbe42d0 items=0
>>>> ppid=23316 pid=23328 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0
>>>> sgid=0
>>>> ...
>>>> jún 20 13:02:56 desk2.stefany.eu sshd[25162]: error: AuthorizedKeysCommand
>>>> /usr/bin/sss_ssh_authorizedkeys martin failed, status 1
>>>> ...
>>>> jún 20 13:02:56 desk2.stefany.eu sshd[25162]: Failed publickey for martin
>>>> from 144.xxx.xxx.xxx port 22543 ssh2: RSA SHA256:uyzB4[stripped]
>>>> ...
>>>> jún 20 13:02:56 desk2.stefany.eu sshd[25162]: error: Received disconnect
>>>> from 144.xxx.xxx.xxx port 22543:14: No supported authentication methods
>>>> available [preauth]
>>>> jún 20 13:02:56 desk2.stefany.eu sshd[25162]: Disconnected from 144.xxx.xxx.xxx
>>>> port 22543 [preauth]
>>>>
>>>> which was weird, because the same key would nicely work elsewhere (on any other
>>>> CentOS 7.2 system, while no Fedora 23 system would work as I have figured out)
>>>>
>>>> I have tried putting SELinux into permissive mode, or generating custom module
>>>> with custom policy allowing this, but it doesn't help, and even tcpdump capture
>>>> doesn't capture anything when such connection to 'somewhere' port 80 is opened.
>>>>
>>>> I moved on to testing the '/usr/bin/sss_ssh_authorizedkeys martin' command.
>>>> Fedora 23:
>>>> # sss_ssh_authorizedkeys martin
>>>> Error looking up public keys
>>>>
>>>> CentOS 7.2:
>>>> # sss_ssh_authorizedkeys martin
>>>> ssh-rsa AAA...
>>>> ssh-rsa AAA...
>>>> ssh-ed25519 AAA...
>>>> ssh-rsa AAA...
>>>> ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCsox... (???) -->> this is one is not in
>>>> LDAP (checked with ldapsearch & ipa user-show martin --all --raw), not present
>>>> in dc=stefany,dc=eu tree or in compat tree
>>>>
>>>> So, I have turned on debug_level = 0x0250 in sssd.conf in both Fedora 23 and
>>>> CentOS 7.2 and checked the logs. CentOS 7.2 is just fine, Fedora 23 gives these
>>>> failures:
>>>> ==> /var/log/sssd/sssd_ssh.log <==
>>>> (Mon Jun 20 21:58:14 2016) [sssd[ssh]] [sss_cmd_get_version] (0x0200): Received
>>>> client version [0].
>>>> (Mon Jun 20 21:58:14 2016) [sssd[ssh]] [sss_cmd_get_version] (0x0200): Offered
>>>> version [0].
>>>> (Mon Jun 20 21:58:14 2016) [sssd[ssh]] [sss_parse_name_for_domains] (0x0200):
>>>> name 'martin' matched without domain, user is martin
>>>>
>>>> ==> /var/log/sssd/sssd_stefany.eu.log <==
>>>> (Mon Jun 20 21:58:14 2016) [sssd[be[stefany.eu]]] [be_get_account_info]
>>>> (0x0200): Got request for [0x1][BE_REQ_USER][1][name=martin]
>>>>
>>>> ==> /var/log/sssd/sssd_ssh.log <==
>>>> (Mon Jun 20 21:58:14 2016) [sssd[ssh]] [decode_and_add_base64_data] (0x0040):
>>>> cert_to_ssh_key failed.
>>>> (Mon Jun 20 21:58:14 2016) [sssd[ssh]] [ssh_cmd_build_reply] (0x0040):
>>>> decode_and_add_base64_data failed.
>>>>
>>>> And that's right, the last - ghost - "sshpubkey" is invalid base64 string. So
>>>> Fedora 23 fails because of some extra validation in SSSD...
>>>>
>>>> I can't tell where this invalid base64 stuff is coming from, and yes, I have
>>>> stopped both IPA servers, run sss_cache -E on both of them and on clients, and
>>>> started IPA servers serially one by one, the invalid key is still there.
>>>>
>>>> I have a plan B to delete the account, put it back and see if it cleans up, but
>>>> I would prefer to figure out what is actually wrong here and what's introducing
>>>> the wrong sshpubkey. And why is sssd_ssh connecting to some port 80 somewhere
>>>>
>>>> Thank you in advance!
>>>>
>>>> Kind regards,
>>>> Martin
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>> --
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>>>> https://www.redhat.com/mailman/listinfo/freeipa-users
>>>> Go to http://freeipa.org for more info on the project
>>>
>>
>> --
>> --
>> Martin

-- 
--
Martin