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

Sumit Bose sbose at redhat.com
Wed Jun 22 15:01:24 UTC 2016 

On Tue, Jun 21, 2016 at 01:23:11PM +0200, Martin Štefany wrote:
> 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?

sss_cache -E itself should be fast, but the next requests like
sss_ssh_authorizedkeys would need a bit longer because SSSD must now
read fresh data from the server. Nevertheless it should take some
seconds, maybe 10-20 with lots of group-memberships, but note as much as
a coffee break.

bye,
Sumit

> 
> 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
> > > > > 
> > > > > 
> > > > > 
> > > > > 
> > > > > 
> > > > 
> > > > 
> > > > 
> > > > > --
> > > > > Manage your subscription for the Freeipa-users mailing list:
> > > > > https://www.redhat.com/mailman/listinfo/freeipa-users
> > > > > Go to http://freeipa.org for more info on the project
> > > > 
> > > 
> > > --
> > > --
> > > Martin
> 
> -- 
> --
> Martin

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