On 07/10/2013 04:48 PM, Alan Evans wrote:
> So I have been kicking around an idea for a while now and thought I
> would develop it but its out of my league. The FreeIPA community is
> very very active in pam/sssd/ldap/so on and so on so I thought I would
> float the idea here before I made a Trac [RFE] ticket.
>
> Would anyone else find it useful to store environment variables in
> LDAP?  In the environment (no pun intended) I work in we have a few
> thousand servers all authenticating to LDAP and a home grown
> LDAP+sshPublicKey implementation which is great.  But we have a bunch
> of different distros which all have different default editors.  Unless
> I feel like touching a lot of servers or using cfengine3 to distribute
> my preferred environment variables I am at the mercy of the editor on
> the system.
>
> How wonderful would it be to set EDITOR=vim, LESS='-S',
> TZ='America/Hawaii', LANG='Klingon' in LDAP and have pam/sss
> pull/store that information for me.  Sort of like pam_env but backed
> by LDAP.
>
> So this got me thinking the other thing that would be wonderful to
> store in LDAP would be shell profiles...  Consider having your
> ~/.profile or ~/.bashrc  or ~/.my.cnf or what-have-you in LDAP?
>
> Maybe this modified pam_ldap could do things like append, remove,
> replace or unset environment variables.  Consider:
>
> dn: uid=me,dc=example,dc=com
> objectClass: posixAccountEnv
> ...
> # replace EDITOR
> posixEnv: EDITOR=vim
> # unset TZ
> posixEnv: TZ-=
> # append PATH
> posixEnv: PATH=+:~/bin
> # prepend PATH
> posixEnv: PATH+=/opt/foo/bin:
>
> Further perhaps the PAM module could be configured to only allow
> certain environment variables to be manipulated this way admins can
> control which variables users can set.
>
> /etc/ldap/pam_ldap.conf:
> ...
> # allow
> pam_allow_env_vars PATH,EDITOR
> # deny
> pam_deny_env_vars PATH,TZ
> # wildcards? regex?
> pam_allow_env_vars LC_*,PATH,EDITOR
> pam_deny_env_vars TZ
>
> So if we're storing environment variables in LDAP why not profiles or
> small files?  ~/.bashrc, ~/.my.cnf, ~/.ssh/config?  Sure there's some
> overlap with env vars because you could set them in your profile but
> with both options an admin is free to choose. 
>
> I can think of a couple of ways to implement this.
> 1. create subortinate objects to the user object
> dn: cn=~/.bashrc,uid=me,dc=example,dc=com
> ...
> objectClass: posixAccountProfile
> posixProfile: <octet string>
>
> Advantages: The advantage of this setup is that the profileScript
> class could contain any number of attributes, perhaps a modified time
> so that the script isn't rewritten if the subordinate object hasn't
> been modified since the script was last modified.
>
> Disadvantages: Kinda kludgy.  Extra objects (more lookups).
>
> 2. Use LDAP attribute options (See http://www.ietf.org/rfc/rfc2251.txt
> RFC 2251 "4.1.5. Attribute Description" if not familiar)
> dn: uid=me,dc=example,dc=com
> ...
> posixProfile;~/.bashrc: <octet string>
> posixProfile;~/.my.cnf: <octet string>
>
> Advantages: No extra objects, makes use of oft unused LDAP attribute
> options :), can have ACI's applied to them.
> Disadvantages: Only modified time to track is modified time of the
> LDAP object not individual profileScript attrs
>
> In both cases it might be wise to consider how file names are
> specified.  Perhaps leave off the ~/ and make everything relative to ~
> no matter what.  Or make everything relative to ~/ even if it starts
> w/ a '/'.  Maybe simply reject anything that begins with '/'.
>
> dn: uid=me,dc=example,dc=com
> ...
> posixProfile;.bashrc: <octetString>
> posixProfile;.foo/foorc: <octetstring>
>
> Plus I don't know if / and . are legitimate characters in attribute
> options.
>
> So thanks for sticking with me if you got this far.  What do you think?
>
> Regards,
> -Alan
>
>
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> Freeipa-users@redhat.com
> https://www.redhat.com/mailman/listinfo/freeipa-users

I see couple problems but in a different plane.
1) You are talking about the server storing this data, it is not
standard but extension can be made. The bigger problem is the client.
Creating the client and porting it to multiple distros is a challenge.
SSSD is in Linux but not in classical UNIXes. As you start looking at
the client side effort solutions like Puppet, Chef and friends become
much more attractive.
2) Which ENV vars need to be served to which groups of hosts. You need
the infrastructure to define and manage it. Puppet, Chef and others are
already good at it.

So I am not really sure that adding the suggested data to LDAP is the
right place. LDAP is just a storage format and client protocol. This is
the smallest part of the effort. This would effectively lead to
duplicating some of existing management systems.

We discussed things like that several years ago when we were starting
IPA project. We needed to draw the line about what to store and what not
to store in LDAP. We came up with a following definition:
Store things that are either traditionally stored in LDAP and already
have LDAP schema of some sort, store things that are dynamic and must be
looked up on the fly because security decision or configuration relies
on it.
That leaves LDAP to be storage of identities (user, groups, hosts, host
groups) and remappings of those identities to the externally managed
objects, i.e. user(s) to command(s) = sudo, user(s) to host access =
HBAC, user(s) to SELinux policies = SELinux user mappings, users and
hosts to SSH keys = SSH integration.

So realistically you might want to have something similar to what we
have for SELinux user mapping that would deliver a "tag" to a host and
then pass it to some pam module that would configure system using that
tag or use this tag to fetch something from a central policy server. But
that would again require a client and server change and if you want it
to be available on multiple platforms you face the same challenge as in 1).


-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager for IdM portfolio
Red Hat Inc.


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