[SSSD] sss_ssh_authorizedkeys: add a flag for ppolicy ?
Pavel Reichl
preichl at redhat.com
Wed Apr 15 11:53:43 UTC 2015
On 04/15/2015 01:46 PM, Olivier wrote:
> Sorry to have missed that : sounds interesting really.
>
> stay to see the articulation between these sssd options,
> sss_ssh_authorizedkeys
> and ssh the authentication process.
>
> I look at it.
>
> --
> Olivier
>
> 2015-04-15 13:20 GMT+02:00 Pavel Reichl <preichl at redhat.com
> <mailto:preichl at redhat.com>>:
>
>
>
> On 04/15/2015 12:10 PM, Olivier wrote:
>> Hi everyone,
>>
>> I saw couple of discussion around in this list as well as others
>> about how to exploit ppolicy with ssh : here are some thought.
>>
>> Currently, I am in a situation where I have inserted my users
>> public ssh keys in ldap (openssh-ldappubkey shema) and
>> instructed sshd to consult ldap for ssh public keys, adding in
>> ssh_config :
>>
>> AuthorizedKeysCommand /usr/bin/sss_ssh_authorizedkeys
>>
>> I also have authorized password authentication , in ssh_config:
>>
>> PasswordAuthentication yes
>>
>> My current policy is the following :
>>
>> - All my users must have a password in ldap (that is used by
>> applications other than ssh)
>>
>> - not all my users may have an ssh key (some never use ssh)
>>
>> Everything works as I want.
>>
>> I now want to introduce ppolicy overlay and would like to enforce
>> rules for password management even for users that mainly use
>> ssh keys.
>>
>> Practically and basically : when a user with valid ssh key ask for
>> an ssh connexion, I would like ssh to behave exactly as if this user
>> had typed a correct "loging/password" and therefore check for
>> ppolicy situation before granting access.
>>
>> aka :
>> - if the account is 'ppolicy desactivated', ssh would refuse to
>> provide the session
>>
>> - if the password is "ppolicy oudated", then ssh would warn to
>> change it (and decrease 'pwdGraceAuthnLimit/'/?)
>>
>> ... and so on.
>>
>> I thought about two options/alternatives to do that :
>>
>> * try to tune pam (may be there would be a way to tell pam to check
>> for user ppolicy fields once authentication has been done before
>> granting access ?)
>>
>> * add some sort of flag (aka: --ppolicy) to sss_ssh_authorizedkeys
>> to instruct sss_ssh_authorizedkeys to check for user ppolicy (use
>> 'ldap_default_bind_dn' as a binding user) and if there is an issue
>> return a "ppolicy error message" rather than the user ssh key ?
>>
>> These are just some thoughts.
>>
>> I'm currently exploring the first option (but I'm not a 'pam'
>> expert and
>> I'm even not sure that the ssh authentication process goes through
>> pam if a valid key is found, even with 'UsePAM yes').
>>
>> I would appreciate any guidance, advices or experiences from you
>> on that particular issue.
>>
>> Thank you,
>>
>> --
>> Olivier
>>
>>
>>
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> Hello Olivier,
>
> are you aware of 'ldap_access_order' option and its values (see
> man sssd-ldap) , could that help you?
>
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>
>
>
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Olivier,
could we stop posting in this thread and continue instead solely in the
thread you created on sssd-user list which is better suited for this
purpose?
Thanks!
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