[Mondrian] Re: xmla security header processing

Michele Rossi michele.rossi at gmail.com
Wed May 18 11:35:52 EDT 2011

did you have a chance to look at my xmla changes?

The general ideas behind them are simple:

1. Pass the credentials provided in Excel down to the method that creates an
2. Leverage the concept of Session ID (already present in XMLA) to store and
retrieve the right authenticated connection for subsequent requests.

What's currently missing is a connection clean up mechanism.
I didn't want to invest time on it before my other changes were accepted.


On 9 May 2011 16:37, Julian Hyde <jhyde at pentaho.com> wrote:

>  Sorry, I missed this. I got your email of April 21st, and will review in
> the next couple of days.
> Julian
>  ------------------------------
> *From:* Michele Rossi [mailto:michele.rossi at gmail.com]
> *Sent:* Monday, May 09, 2011 8:27 AM
> *To:* jhyde at pentaho.com; Mondrian developer mailing list; Luc Boudreau
> *Subject:* Re: [Mondrian] Re: xmla security header processing
> hi Julian and Luc,
> have you had a chance to take a look at the changes that I'd like to
> submit?
> Is there anything unclear about my code that you would like to discuss?
> If you don't think we should have these things in Mondrian I will try a
> different approach, for example using the "xmla callback" mechanism.
> It's a long shot at this stage though, I am not sure it can work yet.
> thanks,
> Michele
> On 21 April 2011 18:44, Michele Rossi <michele.rossi at gmail.com> wrote:
>> hi,
>> I've made several changes to DefaultXmlaServlet / XmlaRequest etc making
>> them capable of using the SOAP credentials to create new OLAP connections.
>> I've tested the code with the following configuration: Excel 2007 with
>> SimbaO2X --> A standalone tomcat server running Olap4jXmlaServlet --> olap4j
>> XMLA driver pointing to a standard mondrian installation running FoodMart.
>> You will find a few bits which are to do with the way Excel 2007 and Simba
>> O2X behave.
>> Let me know if you think they are too specific and we don't want to have
>> them in the code.
>> XMLA  has a concept of session ID which I leverage to store new
>> OlapConnection objects and retrieve them when new requests arrive with a
>> session ID for which a connection is already available.
>> This might sound unnecessarily complicated but I think it is essential, at
>> least for SimbaO2X.
>> Without this mechanism Simba would trigger the creation of lots of
>> connections and that would be slow and memory expensive.
>> I've further refined this mechanism by creating a session id based on the
>> hashcode of the username  and (when I finish it) the IP of the remote client
>> host.
>> This will mean that even fewer unnecessary connections are created and
>> things are a lot faster.
>> My changes are mostly in XmlaHandler and DefaultXmlaServlet.
>> I didn't touch any of the MondrianServer classes.
>> I wanted this mechanism to be applicable to any OLAP4J provider.
>> I am aware that I've made a high number of changes.
>> It wouldn't have been possible to do what I wanted with anything less
>> though.
>> Hope you don't find the changes too hard to review.
>> As with my previous code changes, searching for [MROSSI] should help you
>> find my new code.
>> Many thanks!
>> Michele
>> On 21 April 2011 00:41, Julian Hyde <jhyde at pentaho.com> wrote:
>>>  Don't change mondrian.server.Repository.getConnection; by that time,
>>> the user should be authenticated and a role should be known.
>>> Instead, create a method
>>> void MondrianServer.getConnectionUnauthenticated(
>>>  String userName,
>>>  String password,
>>>  String catalogName,
>>>  String schemaName,
>>>  Properties properties)
>>> Note that it is like
>>> void MondrianServer.getConnection(
>>>     String catalogName,
>>>     String schemaName,
>>>     String roleName,
>>>     Properties props);
>>> except that 'role' is removed and 'userName' and 'password' have been
>>> added. MondrianServer should then authenticate, and call
>>> Repository.getConnection.
>>> If MondrianServer needs a database of usernames and passwords, and how
>>> they map to roles, please use JAAS for that. I believe it is the standard
>>> for such things.
>>> Julian
>>>  ------------------------------
>>> *From:* mondrian-bounces at pentaho.org [mailto:
>>> mondrian-bounces at pentaho.org] *On Behalf Of *Luc Boudreau
>>> *Sent:* Wednesday, April 20, 2011 2:22 PM
>>> *To:* Mondrian developer mailing list
>>> *Subject:* Re: [Mondrian] Re: xmla security header processing
>>> Michele,
>>> I understand your requirement. You want to passthrough the credentials
>>> through the servlet down to the OlapConnection. The architecture of the
>>> Mondrian Server was not designed with that in mind, so my concern is that
>>> such a feature is integrated 'the right way'. The proper way to do this
>>> would be to modify the mondrian.server.Repository#getConnection method to
>>> take a user and password as arguments. One downside is that we will depend
>>> on Java Services Discovery to register the olap4j driver with the
>>> DriverManager. One thing I don't like about that approach is the fact that
>>> the server becomes 'aware' of the requests contents. I guess this was
>>> unavoidable as soon as we attempted to factor out the Mondrian Server in
>>> it's own project.
>>> Write up some code and send it to this list. As you said, better discuss
>>> over code than concepts :)
>>> Luc
>>> On Wed, Apr 20, 2011 at 4:15 PM, Michele Rossi <michele.rossi at gmail.com>wrote:
>>>> hi,
>>>> at the moment DefaultXmlaServlet simply ignores the XMLA SOAP security
>>>> information.
>>>> If there was ever anything like that in the code before it's certainly
>>>> been removed now.
>>>>  In Excel (with Simba) you can type a username and a password in the
>>>> dialog used to create a connection to an xmla server.
>>>> Simba puts those two strings in a SOAP "Security" header that looks like
>>>> my example below.
>>>> I already have a working "mod" of DefaultXmlaServlet that I have been
>>>> using for a while capable of reading and using that security header.
>>>> Going back to your question about containers: it's certainly possible to
>>>> protect access to "/xmla" using a standard http authentication mechanisms
>>>> but Simba doesn't support any of that.
>>>> Also even if Simba supported it the container would certainly not pass
>>>> the authentication information to the XMLA servlet.
>>>> And the biggest deal for me is using the credentials provided in Excel
>>>> to open an authenticated Olap4j connection.
>>>> I will put together a prototype in the next few days, I think it will be
>>>> easier to discuss this with a piece of code to look at.
>>>> thanks,
>>>> Michele
>>>> On 20 April 2011 21:19, Julian Hyde <jhyde at pentaho.com> wrote:
>>>>>  I'd rather not spend hours researching this. But authentication
>>>>> problems have been solved countless times before in the XMLA server code
>>>>> base. Including authentication from Simba O2X. Can you look over the code
>>>>> and the checkin history and find out how the previous solutions did it.
>>>>> If there is someone on the developers list who has worked on these
>>>>> issues, please speak up now.
>>>>> Julian
>>>>>  ------------------------------
>>>>>  *From:* Michele Rossi [mailto:michele.rossi at gmail.com]
>>>>> *Sent:* Wednesday, April 20, 2011 10:52 AM
>>>>> *To:* <jhyde at pentaho.com>
>>>>> *Cc:* Mondrian developer mailinglist
>>>>> *Subject:* Re: xmla security header processing
>>>>>   hi,
>>>>> as far as I know Axis is not a container but a library to create SOAP
>>>>> web services.
>>>>> There is nothing a container can do with that security information as
>>>>> it's not transferred in a standard http way.
>>>>> The username and password that you type in Excel when you create a new
>>>>> SimbaO2x connection are sent to the server in the request header xml element
>>>>> that I copied below.
>>>>> So we either modify the xmla servlet or create an xmla callback with
>>>>> the same features.
>>>>> Do you agree on the general principle that the client (excel)
>>>>> credentials should be used to open the olap4j connection?
>>>>> And that the session id should be used to retrieve existing
>>>>> connections?
>>>>> You certainly can't delegate any of these two features to the
>>>>> container.
>>>>> thanks!
>>>>> Michele
>>>>> Sent from my iPhone
>>>>> On 20 Apr 2011, at 18:19, "Julian Hyde" <jhyde at pentaho.com> wrote:
>>>>>   I'm not an expert on the HTTP/SOAP stuff. But the general goal
>>>>> should be to let the container (e.g. tomcat or apache axis) manage as much
>>>>> of this stuff as possible. Maybe you can see how people have made
>>>>> authentication work elsewhere in the XMLA servlet.
>>>>> Julian
>>>>>  ------------------------------
>>>>> *From:* Michele Rossi [mailto:michele.rossi at gmail.com]
>>>>> *Sent:* Wednesday, April 20, 2011 8:00 AM
>>>>> *To:* Mondrian developer mailing list
>>>>> *Cc:* <jhyde at pentaho.com>jhyde at pentaho.com
>>>>> *Subject:* xmla security header processing
>>>>> Hi,
>>>>> I am writing some code to handle the xmla security header:
>>>>>  <Header>
>>>>>                        <Security xmlns="<http://schemas.xmlsoap.org/ws/2002/04/secext>
>>>>> http://schemas.xmlsoap.org/ws/2002/04/secext">
>>>>>                            <UsernameToken>
>>>>>                                <Username>MICHELE</Username>
>>>>>                                <Password
>>>>> Type="PasswordText">ROSSI</Password>
>>>>>                            </UsernameToken>
>>>>>                        </Security>
>>>>>                        <BeginSession mustUnderstand="1"
>>>>> xmlns="urn:schemas-microsoft-com:xml-analysis" />
>>>>>                     </Header>
>>>>> Such header is sent out by XMLA clients such as SimbaO2X (Excel
>>>>> plugin).
>>>>> My idea is to pass user credentials down to the connection manager and
>>>>> use them to create new connections.
>>>>> I also think that connections should be associated with sessions.
>>>>> I am thinking of a Map that associates session IDs with OlapConnection
>>>>> objects.
>>>>> I can put all this logic directly in DefaultXmlaServlet or (probably)
>>>>> in a "XmlaRequestCallback" class.
>>>>> Which option do we want to go for?
>>>>> I also have in mind another more specific bit of functionality: hiding
>>>>> username / password in the session ID returned to the xmla client.
>>>>> This can be useful especially in the case of a server going down and
>>>>> forgetting a particular session id.
>>>>> (Your user leaves Excel open for a couple of days and when he tries to
>>>>> use the Pivot again he gets an error if the server has been bounced in the
>>>>> meantime).
>>>>> The other use case could be http load balancers.
>>>>> As Excel does not send any cookies most load balancers would fail to
>>>>> apply the "sticky session" policy and could redirect different xmla requests
>>>>> to different cluster members.
>>>>> Only one of those members would know about the specified session ID (in
>>>>> other words only one of those servers would have an OlapConnection object
>>>>> stored under the given session id) but the others could re-obtain the
>>>>> credentials by de-crypting the session id.
>>>>> I can make the encrypted session ID very secure - even to "clear text"
>>>>> attacks.
>>>>> I will discuss the details only if we think it's a feature worth
>>>>> having.
>>>>> Michele
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