On 09/04/2018 11:10, Isuranga Perera wrote:
Since such condition can happen only if the same user tries to login from 2
mediums at the same, this is rarely happen. However that slight chance may
prevent that particular user from login to the system until all or all-1
access tokens are expired.
Using the UNIQUE constraint will definitely will provide a better security
and furthermore will make the model more meaningful. On the other hand this
will break the token replacing functionality since it first create a token
(at this time there are 2 tokens in the db) and delete the last one.

What I propose is writing a separate query to replace tokens instead of
using save & delete queries separately and furthermore we can use a new
query to save tokens without affecting the UNIQUE constraints so that no
need to mess with threading & @Transactional properties.

If you can come up with a proposal which works with all the supported DBMSes, then please go on.

As already asked as comment in your recent PR: did you submit an ICLA for your contributions? Thanks.

Regards.

On Mon, Apr 9, 2018 at 2:06 PM, Francesco Chicchiriccò <ilgro...@apache.org>
wrote:

On 09/04/2018 10:14, Isuranga Perera wrote:

The Read Committed isolation level ensures that data can only be read by a
transaction if it is in the committed state. It doesn't completely isolate
this transaction(create) hence some other transaction can still use this
method which results in the behavior I explained previously. Ideally If
we're gonna use @Transactional annotation the isolation level should be
serialized for create operation. Please correct me If I'm wrong.

I see your point - while I don't completely agree about the likelihood of
such race condition to actually happen.

At worse, you might end up in having two distinct JWT (Access Tokens)
values for a single user, which will anyway be subject to expiration due to

https://github.com/apache/syncope/blob/master/core/provision
ing-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/job/ExpiredAccessTokenCleanup.java

For additional security, we might want to impose a UNIQUE constraint on

https://github.com/apache/syncope/blob/master/core/persisten
ce-jpa/src/main/java/org/apache/syncope/core/persistenc
e/jpa/entity/JPAAccessToken.java#L48

(not sure to remember why the column is currently set as nullable, though).
With UNIQUE owner, the step (5) in your sequence below will fail anyway.

Again, given the chances that the race condition applies, and considering
what would be the harm (nearly none, to me), I would rather avoid any
modification rather than imposing the UNIQUE constraint.


Regards.

On Mon, Apr 9, 2018 at 1:12 PM, Francesco Chicchiriccò <
ilgro...@apache.org>
wrote:

On 09/04/2018 09:30, Isuranga Perera wrote:
Hi Francesco,
Yes there is @Transactional annotation. But it haven't set the isolation
property as well as the propagation property. Based on the default
values
set this thread safe problem will still occur. Please correct me if I'm
wrong.

The transaction isolation level is set in
https://github.com/apache/syncope/blob/master/core/persisten
ce-jpa/src/main/resources/domains/MasterDomain.xml#L57-L59

Regards.


On Mon, Apr 9, 2018 at 12:20 PM, Francesco Chicchiriccò <

ilgro...@apache.org> wrote:

On 09/04/2018 08:46, Isuranga Perera wrote:

Hi Francesco,

I will take a scenario. Suppose a scenario where thread A & thread B
try
to login user admin.

    1. thread A checks if a token exist for the user admin (suppose
       currently there is no token associated with the admin)
    2. Then thread A execute following logic[1] to create and save the
token.
    3. Before thread A save the token for user admin thread B checks
if a
       token exist for user admin (since the toked created by thread A
is
       not yet saved *exist == null*)
    4. Then thread A complete the creation of token (and saving)
    5. Thread B also complete the creation and saving of the token.

That way there can be 2 tokens for a particular user.


You analysis does not take into any account the fact of the
constraints

imposed by the @Service annotation in

https://github.com/apache/syncope/blob/master/core/rest-cxf/
src/main/java/org/apache/syncope/core/rest/cxf/service/Acces
sTokenServiceImpl.java#L35

(e.g. the place when external requests can come in) nor by the
@Transactional annotation injected into

https://github.com/apache/syncope/blob/master/core/logic/
src/main/java/org/apache/syncope/core/logic/AccessTokenLogic.java#L80

via

https://github.com/apache/syncope/blob/master/core/logic/
src/main/java/org/apache/syncope/core/logic/AbstractTra
nsactionalLogic.java#L29

Regards.

[1] https://github.com/apache/syncope/blob/master/core/provision

ing-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/data/AccessTokenDataBinderImpl.java#L119

Best Regards
Isuranga Perera

On Mon, Apr 9, 2018 at 11:42 AM, Francesco Chicchiriccò <
ilgro...@apache.org <mailto:ilgro...@apache.org>> wrote:

       On 09/04/2018 07:07, Isuranga Perera wrote:

           Hi All,

           Token create method in AccessTokenDataBinderImpl[1] is not
           thread safe.


       Could you please explain why you're affirming this?

           This could result in several problems including

             * Exist 2 different access token for a particular user at
a
           given
               time which may result in an exception thrown by method
call[2]
               since it expects a single token a given user.

           In addition to that token replace is implemented as a
           combination of 2 different functionalities. Since the method
           is not thread safe this may cause some unexpected behaviors
           (since there can be 2 tokens exist for a particular user.
same
           scenario as above).

           Appreciate your insight on the $subject.


           [1]
           https://github.com/apache/sync
ope/blob/master/core/provision
ing-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/data/AccessTokenDataBinderImpl.java#L104
           <https://github.com/apache/syn
cope/blob/master/core/provisio
ning-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/data/AccessTokenDataBinderImpl.java#L104>

           [2]
           https://github.com/apache/sync
ope/blob/master/core/provision
ing-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/data/AccessTokenDataBinderImpl.java#L113
           <https://github.com/apache/syn
cope/blob/master/core/provisio
ning-java/src/main/java/org/apache/syncope/core/provisioni
ng/java/data/AccessTokenDataBinderImpl.java#L113>

           Best Regards
           Isuranga Perera

--
Francesco Chicchiriccò

Tirasa - Open Source Excellence
http://www.tirasa.net/

Member at The Apache Software Foundation
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