[Fedora-directory-users] posixgroup name lookups

Rich Megginson rmeggins at redhat.com
Fri Nov 21 16:10:16 UTC 2008


John A. Sullivan III wrote:
> On Thu, 2008-11-20 at 09:01 -0800, George Holbert wrote:
>   
>> Jonathan Barber wrote:
>>     
>>> On Wed, Nov 19, 2008 at 03:32:28PM -0500, John A. Sullivan III wrote:
>>>   
>>>       
>>>> On Wed, 2008-11-19 at 12:21 -0800, George Holbert wrote:
>>>>     
>>>>         
>>>>> John A. Sullivan III wrote:
>>>>>       
>>>>>           
>>>>>>> John A. Sullivan III wrote:
>>>>>>>           
>>>>>>>               
>>> [snip]
>>>
>>>   
>>>       
>>>> <snip>
>>>> Thanks for the very thoughtful answer.  I'm not only new to LDAP but
>>>> also to Linux based file servers.  I've been in a management role for
>>>> the last decade and before then was doing NDS and NetWare for
>>>> directory/file.
>>>>
>>>> We were planning to use a umask of 007 for standard users and set the
>>>> sgid bit for shared folders.  That's where we thought it would be
>>>> helpful to have a group associated with each user.  In fact, it finally
>>>> made the default setup of creating a group for each user make sense as I
>>>> always wondered why that was done.  I suppose we'll also need to
>>>> activate file system acls for more complex setups as when multiple
>>>> groups need varying access to a shared file system directory.
>>>>     
>>>>         
>>> This arrangement is known (at least by Redhat) as User Private Groups
>>> (UPG):
>>> http://www.redhat.com/docs/manuals/linux/RHL-7.3-Manual/ref-guide/s1-users-groups-private-groups.html
>>>
>>> The primary reason for doing it is that group access to files is managed
>>> via secondary group membership, not primary group membership
>>>
>>> If each of your users has their own group, then adding a posixGroup
>>> objectclass to each user makes perfect sense. You may also want to place
>>> an uniqueness constraint on the gidNumber attribute as well:
>>> http://www.centos.org/docs/5/html/CDS/ag/8.0/Administering_DSPPR-Server_Plug_in_Functionality_Reference.html#Server_Plug_in_Functionality_Reference-UID_Uniqueness_Plug_in
>>>
>>> WRT to linux, the only gotcha I can think of is that you'll have to set
>>> the nss_ldap nss_base_group option in /etc/ldap.conf to an entry that's
>>> the common parent to both your users and groups - otherwise it'll never
>>> find the UPG's.
>>>
>>>   
>>>       
>> Another way would be to omit the addition of the posixGroup on your 
>> account objects, and just modify the filter on nss_base_group to include 
>> posixAccounts.
>> e.g.:
>> nss_base_group  
>> dc=example,dc=com?sub?(|(objectClass=posixGroup)(objectClass=posixAccount))
>>
>> posixAccount already includes the gidNumber and cn attributes, which is 
>> all you're really after here... unless you want to start adding 
>> memberUid attributes to your account objects (which doesn't make any 
>> obvious sense).
>>
>> You will almost certainly have to modify your nss_base_group setting in 
>> either case, as Jonathan suggested.
>>
>>     
> <snip>
> Alas, I'm not sure this is going to work as expected but it could be my
> ignorance.  I've read the man page and whatever documentation I could
> find.  It appears it does an & operation with the additional filter
> whereas I need an |.
>
> I gather the default is:
> &(objectClass=posixgroup)(cn=group_name)
>
> I think I need it to be:
> |((&(objectClass=posixgroup)(cn=group_name))(&(objectClass=posixaccount)(uid=group_name)))
>
> If it does an &, I think I get:
> &((&(objectClass=posixgroup)(cn=group_name))(&(objectClass=posixaccount)(uid=group_name)))
>
> Nevertheless, I tried all of the following without success:
>
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?|(objectClass=posixAccount)
>   
Invalid filter - the "|" character does not belong there.
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?|(&(objectClass=posixAccount)(uid=group_name))
> this broke the posixgroup filter, too!
>   
Also invalid - "|" character
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?&(objectClass=posixAccount)(uid=group_name)
> this broke the posixgroup filter, too!
>   
Invalid filter - a filter must begin with ( and end with ) - so 
(&(objectClass=posixAccount)(uid=group_name))
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?(objectClass=posixAccount)(uid=group_name)
> this broke the posixgroup filter, too!
>   
Invalid filter - (&(objectClass=posixAccount)(uid=group_name))
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?(objectClass=posixAccount)
> this broke the posixgroup filter, too!
>   
Not sure what's wrong with this one - looks ok
> nss_base_group          dc=X,dc=com,dc=ssiservices,dc=biz?sub?&(objectClass=posixAccount)
>   
Invalid filter - should just be (objectClass=posixAccount)
> I did flush the nscd group database between each try.  What am I doing
> wrong? Thanks - John
>   
It looks as though nss_base_group uses LDAP URL syntax - see 
http://www.ietf.org/rfc/rfc2255.txt for more information about LDAP 
URLs, and http://www.ietf.org/rfc/rfc2254.txt for information about LDAP 
filters
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