On (28/07/16 12:44), thierry bordaz wrote:
>
>
>On 07/28/2016 11:17 AM, Lukas Slebodnik wrote:
>> On (28/07/16 10:24), thierry bordaz wrote:
>> >
>> > On 07/28/2016 09:39 AM, Jakub Hrozek wrote:
>> > > On Wed, Jul 27, 2016 at 04:09:07PM +0200, thierry bordaz wrote:
>> > > > On 07/27/2016 03:36 PM, Jakub Hrozek wrote:
>> > > > > On Wed, Jul 27, 2016 at 02:55:37PM +0200, thierry bordaz wrote:
>> > > > > > On 07/27/2016 01:56 PM, Jakub Hrozek wrote:
>> > > > > > > On Wed, Jul 27, 2016 at 01:03:59PM +0200, Jakub Hrozek wrote:
>> > > > > > > > On Wed, Jul 27, 2016 at 12:22:46PM +0200, Lukas Slebodnik
>> > > > > > > > wrote:
>> > > > > > > > > On (27/07/16 12:08), Jakub Hrozek wrote:
>> > > > > > > > > > On Wed, Jul 27, 2016 at 12:02:24PM +0200, Jakub Hrozek
>> > > > > > > > > > wrote:
>> > > > > > > > > > > On Wed, Jul 27, 2016 at 11:54:16AM +0200, Lukas
>> > > > > > > > > > > Slebodnik wrote:
>> > > > > > > > > > > > ehlo,
>> > > > > > > > > > > >
>> > > > > > > > > > > > attached patch fixes acces denied after activating
>> > > > > > > > > > > > user in 389ds.
>> > > > > > > > > > > > Jakub had some comments/ideas in ticket but I think
>> > > > > > > > > > > > it's better to discuss
>> > > > > > > > > > > > about virtual attributes and timestamp cache on
>> > > > > > > > > > > > mailing list.
>> > > > > > > > > > > Yes, so the comment I have is that while this works, it
>> > > > > > > > > > > might break some
>> > > > > > > > > > > strange LDAP servers.
>> > > > > > > > > > >
>> > > > > > > > > > > We use modifyTimestamp as a 'positive' indicator that
>> > > > > > > > > > > the entry has not
>> > > > > > > > > > > changed -- if the modifyTimestamp didn't change, we
>> > > > > > > > > > > consider the cached
>> > > > > > > > > > > entry the same as what is on the server and only bump
>> > > > > > > > > > > the timestamp
>> > > > > > > > > > > cache. If the timestamp is different, we do a
>> > > > > > > > > > > deep-comparison of cached
>> > > > > > > > > > > attribute values with what is on the LDAP server and
>> > > > > > > > > > > write the sysdb
>> > > > > > > > > > > cache entry only if the attributes differ.
>> > > > > > > > > > >
>> > > > > > > > > > > I was wondering if we can use the modifyTimestamp at
>> > > > > > > > > > > all, then, because
>> > > > > > > > > > > even if it's the same, we might want to check the
>> > > > > > > > > > > attributes to see if
>> > > > > > > > > > > some of the values are different because some of the
>> > > > > > > > > > > attributes might be
>> > > > > > > > > > > this operational/virtual attribute..
>> > > > > > > > > > Sorry, sent too soon.
>> > > > > > > > > >
>> > > > > > > > > > I think the questions are -- 1) can we enumerate the
>> > > > > > > > > > virtual attributes?
>> > > > > > > > > That might be a question for 389-ds developers.
>> > > > > > > > > But it's very likely it will be different on other LDAP
>> > > > > > > > > servers.
>> > > > > > > > >
>> > > > > > > > > > 2) Would different LDAP servers have different virtual
>> > > > > > > > > > attributes.
>> > > > > > > > > >
>> > > > > > > > > > For 2) maybe a possible solution might be to set a
>> > > > > > > > > > non-existing
>> > > > > > > > > > modifyTimestamp attribute value, but I would consider that
>> > > > > > > > > > only a
>> > > > > > > > > > kludge, we shouldn't break existing setups..
>> > > > > > > > > I am not satisfied with this POC solution either.
>> > > > > > > > >
>> > > > > > > > > So should we remove usage of modifyTimestamp for detecting
>> > > > > > > > > changes?
>> > > > > > > > I would prefer to ask the DS developers before removing it
>> > > > > > > > completely.
>> > > > > > > >
>> > > > > > > > At least for large groups it might take a long time to compare
>> > > > > > > > all attribute
>> > > > > > > > values and IIRC we don't depend on any virtual attributes for
>> > > > > > > > groups. Maybe
>> > > > > > > > we could parametrize that part of the code and enable the fast
>> > > > > > > > way with
>> > > > > > > > modifyTimestamps for 'known' server types, that is for setups
>> > > > > > > > with AD and
>> > > > > > > > IPA providers.
>> > > > > > > >
>> > > > > > > > For users, there is typically not as many attributes so we
>> > > > > > > > should be
>> > > > > > > > fine deep-comparing all attributes.
>> > > > > > > I'm adding Thierry (so please reply-to-all to keep him in the
>> > > > > > > thread).
>> > > > > > >
>> > > > > > > Thierry, in the latest sssd version we tried to add a performance
>> > > > > > > improvement related to how we store SSSD entries in the cache.
>> > > > > > > The short
>> > > > > > > version is that we store the modifyTimestamp attribute in the
>> > > > > > > cache and
>> > > > > > > when we fetch an entry, we compare the entry modifyTimestamp
>> > > > > > > with what
>> > > > > > > is on the server. When the two are the same, we say that the
>> > > > > > > entry did
>> > > > > > > not change and don't update the cache.
>> > > > > > >
>> > > > > > > This works fine for most attributes, but not for attributes like
>> > > > > > > nsAccountLock which do not change modifyTimestamp when they are
>> > > > > > > modified. So when an entry was already cached but then
>> > > > > > > nsAccountLock
>> > > > > > > changed, we treated the entry as the same and never read the new
>> > > > > > > nsAccountLock value.
>> > > > > > >
>> > > > > > > To fix this, I think we have several options:
>> > > > > > > 1) special-case the nsAccountLock. This seems a bit
>> > > > > > > dangerous,
>> > > > > > > because I'm not sure we can say that some other
>> > > > > > > attribute we are
>> > > > > > > interested in behaves the same as nsAccountLock.
>> > > > > > > 2) drop the modifyTimestamp optimization completely.
>> > > > > > > Then we fall
>> > > > > > > back to comparing the attribute values, which might
>> > > > > > > work, but for
>> > > > > > > huge objects like groups with thousands of members, this
>> > > > > > > might be
>> > > > > > > too expensive.
>> > > > > > > 3) only use the modifyTimestamp optimization for cases
>> > > > > > > where we know
>> > > > > > > we don't read any virtual attributes.
>> > > > > > >
>> > > > > > > And my question is -- can we, in general, know if the
>> > > > > > > modifyTimestamp
>> > > > > > > way of detecting changes is realiable for all LDAP servers? Or
>> > > > > > > do you
>> > > > > > > think it should only be used for cases where we know we are not
>> > > > > > > interested in any virtual attributes (that would mostly be
>> > > > > > > storing
>> > > > > > > groups from servers where we know exactly what is on the server
>> > > > > > > side,
>> > > > > > > like IPA or AD).
>> > > > > > Hello,
>> > > > > >
>> > > > > > Relying on modifytimestamp looks a good idea. Any MOD/MODRDN will
>> > > > > > update it,
>> > > > > > except I think it is unchanged when updating some password policy
>> > > > > > attributes.
>> > > > > >
>> > > > > > Regarding virtual attribute, the only one I know in IPA is
>> > > > > > nsaccountlock.
>> > > > > > nsaccountlock is an operational attribute (you need to request it
>> > > > > > to see it)
>> > > > > > and is also a virtual attribute BUT only for 'staged' and
>> > > > > > 'deleted' users.
>> > > > > > It is a stored attribute for regular users and we should update
>> > > > > > modifytimestamp when it is set.
>> > > > > >
>> > > > > > thanks
>> > > > > > thierry
>> > > > > OK, in that case it seems like we can special-case it. But do you
>> > > > > know
>> > > > > about any other attributes in any other LDAP servers?
>> > > > Any LDAP server following standard should provide modifytimestamp that
>> > > > reflect the last update of the entry. Now virtual attribute values may
>> > > > be
>> > > > "attached" to the entry and its value change without modification of
>> > > > modifytimestamp.
>> > > > For 389-ds and IPA it is fine as virtual value of nsaccountlock is
>> > > > changed
>> > > > only when the DN change.
>> > > > For others LDAP servers I suppose it exists the same ability to define
>> > > > service providers that return virtual attribute values. The difficulty
>> > > > is
>> > > > that the schema may not give any hint if the retrieved attributes
>> > > > values
>> > > > were stored or computed and consequently trust modifytimestamp to know
>> > > > if
>> > > > the values changed or not.
>> > > > For example in ODSEE, memberof is a virtual attribute.
>> > > Thank you, for the explanation Thierry.
>> > >
>> > > Then to be on the safe side I propose:
>> > > 1) We add an (probably undocumented?) flag that says whether to use
>> > > modifyTimestamp to detect entry changes or not
>> > > 2) for the generic LDAP provider we always really compare the
>> > > attribute values, in other words the option would be set to
>> > > false. If there is anyone with performance issues with a generic
>> > > setup, we tell them to flip the option.
>> > > 3) For the IPA and AD providers, we set this option to true and use
>> > > the modifyTimestamp value to detect changes
>> > > 4) We special case nsAccountLock
>> > I am not sure I understand why nsAccountLock is a special case ?
>> > In IPA/389:
>> >
>> > * Stage user, it is always 'nsaccountlock: True'
>> > When stage entry is created or updated, 'modifytimestamp' is also
>> > updated. So you can rely on modifytimestamp to detect a change in a
>> > stage user.
>> > There is no way to update nsaccountlock for a stage entry
>> > * Deleted user. Idem Stage user
>> We haven't tested stage users yet. I ran just sssd related regression tests.
>>
>> > * Regular user. 'nsaccountlock' is *not* a virtual attribute, so if it
>> > is enable/disable you can rely on modifytimestamp to detect a change
>> > of 'nsaccountlock' for a regular user.
>> > Also any change on regular user will update 'modifytimestamp' so you
>> > can rely on it to detect a change.
>> >
>> My experience with ns-inactivate.pl and ns-activate.pl is different.
>> modifytimestamp is not changed even though nsaccountlock was changed.
>>
>> It was a plain 389-ds with id_provider ldap in sssd
>>
>> LS
>Hi Lukas,
>
>
>It may have change recently because I can not reproduce. What versions are
>you running ?
>
> #
> #initial entry
> #
> ldapsearch -LLL -o ldif-wrap=no -D "cn=directory manager" -w xxx -b
> "cn=accounts, <suffix>" 'uid=user0' nsaccountlock modifytimestamp
> createtimestamp
> dn: uid=user0,cn=users,cn=accounts,<suffix>
> modifytimestamp: *20160728103441Z*
> createtimestamp: 20160726160436Z
>
> #
> # Inactivate: modifytimestamp changed
> #
> /usr/sbin/ns-inactivate.pl -Z <instance> -D "cn=directory manager"
> -w xxx -I uid=user0,cn=users,cn=accounts,<suffix>
> uid=user0,cn=users,cn=accounts,<suffix> inactivated.
>
> ldapsearch -LLL -o ldif-wrap=no -D "cn=directory manager" -w xxx -b
> "cn=accounts, <suffix>" 'uid=user0' nsaccountlock modifytimestamp
> createtimestamp
> dn: uid=user0,cn=users,cn=accounts,<suffix>
> nsaccountlock: true
> modifytimestamp: *20160728103642Z*
> createtimestamp: 20160726160436Z
>
> #
> # activate: modifytimestamp changed
> #
> /usr/sbin/ns-activate.pl -Z <instance> -D "cn=directory manager" -w
> xxx -I uid=user0,cn=users,cn=accounts,<suffix>
> uid=user0,cn=users,cn=accounts,<suffix> activated.
>
> ldapsearch -LLL -o ldif-wrap=no -D "cn=directory manager" -w xxx -b
> "cn=accounts, <suffix>" 'uid=user0' nsaccountlock modifytimestamp
> createtimestamp
> dn: uid=user0,cn=users,cn=accounts,<suffix>
> modifytimestamp: *20160728103711Z*
> createtimestamp: 20160726160436Z
>
rhel7.3
389-ds-base-1.3.5.10-5.el7.x86_64
But I didn't test directly with user but indirectly
*Add Managed role
dn: cn=managed,ou=people,dc=example,dc=com
objectclass: top
objectclass: LdapSubEntry
objectclass: nsRoleDefinition
objectclass: nsSimpleRoleDefinition
objectclass: nsManagedRoleDefinition
cn: Managed
*Authenticate with lockuser
*Add user to managed role
dn: uid=lockuser,ou=people,dc=example,dc=com
changetype: modify
add: nsRoleDN
nsRoleDN: cn=managed,ou=people,dc=example,dc=com
ns-inactivate.pl -D cn=Manager,dc=example,dc=com" -E -p 389 \
-h $SERVER -I cn=managed,ou=people,dc=example,dc=com
*Authenticate with lockuser
ns-activate.pl -D cn=Manager,dc=example,dc=com" -E -p 389 \
-h $SERVER -I cn=managed,ou=people,dc=example,dc=com
*Authenticate with lockuser
Should I test with rhel7.2 or is it an expected behaviour ?
LS
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