Abstract:
A soft-denial system for client-server networks is disclosed for translating server authorization denials into responses that are known to be innocuous to the client application. The soft-denial system includes a client-application which originates a service request across a network to a server-application which rejects the request due to lack of authorization and subsequently provides a denial response. A soft-denial application intercepts the denial response, translates the response into a response known to be innocuous to the client-application, and forwards the innocuous response to the client-application. The soft-denial system is particularly useful for overcoming client-application failures due to authorization expectation mismatches.

Description:
FIELD OF THE INVENTION  
       [0001]    The invention relates to communication protocols and is particularly concerned with a soft-denial mode of inter-application communications. 
       BACKGROUND OF THE INVENTION  
       [0002]    As described in U.S. Pat. No. 5,689,708; in historical mainframe computer systems, a single central processor complex running under an operating system would execute application programs, stores databases, enforce security, and allocates all resources such as processor time, memory usage, and subsystem processing. Users would interact with the system via “dumb” terminals, which essentially only display data and receive keystrokes. 
         [0003]    Evolution of networking connectivity and processor availability led to peer-to-peer networks of systems such as personal computers which are essentially standalone computers each running similar operating system programs, which can share application programs and data among each other according to a defined protocol. 
         [0004]    Yet another form of computing deployment is that of client/server networks which have a central server computer coupled via a communications medium to a number of client computers, usually smaller personal computers running under a conventional operating system. In the earliest client/server network model, the server was only a “file server” which could download data to the clients and upload data from them; application programs were executed entirely in the client computers. 
         [0005]    Most present client/server networks implement a more sophisticated “application server” model in which some or all application programs are split into two portions. A server portion executes within the server computer, while a separate client portion executes within each client computer from which a user can invoke the application. The two portions employ cooperative processing to pass data between the server and client computers; typically, most of the data is stored in the server. The first major application of this model was the processing of client queries against a central database, so that this model is also sometimes known as a “database server” network. 
         [0006]    A key operational aspect which must be handed in such networks involves establishing authorization for access to data and services on the server by a given client. Authorization/permission control frameworks and relationships may be complex. Actions assigned to or requested by different components of such framework can be configured independently and separately by different entities: end user, application, AAA (Authentication, authorization and accounting) server, database, application server, firewall, network administrator, and other like network resource equipment. 
         [0007]    At the time of actual performing of its actions, a given user&#39;s application (client-application) may communicate with another “application-aware” network entity which controls the permissions assigned to this application or user. This network entity could be some kind of Configuration server, Kerberos-like server, SBC (Session Border Controller), firewall, database, IPS (Intrusion Prevention System), Proxy server, or similar resource providing entity. This inter-application communication will operate using some form of communication protocol, API or other means. 
         [0008]    The client-application, however, will also have its own independently defined settings which describe the actions this application is assumed (or expected by the user) to perform, i.e. things it is configured to do. At the time of execution these “local” settings may conflict with those permissions set by server-application. As a result of this, the client-application&#39;s request/action will not have permissions or authorization to be executed on (or approved by) the external entity. This results in the request/action denial by that external entity. 
         [0009]    Denial of action may take various forms: 
         [0010]    1. Rejection at application level and by the server application means 
         [0011]    1.1 A “not authorized” application response—once extra credentials have been explicitly asked and (re)submitted 
         [0012]    1.2 A “cancellation” of the transaction 
         [0013]    1.3 A “bad/unrecognized request” type of application response 
         [0014]    1.4 A redirection/forwarding to another external entity by means of the server application 
         [0015]    1.5 An inducement of an error state or other security condition on the server side (external entity) 
         [0016]    2. A client-to-server connection tear-down at the network Transport layer 
         [0017]    3. A total lack of response 
         [0018]    4. A partial provisioning—i.e. providing some minimal authorization/resources/access—yet not such as requested/expected/needed by the client application. 
         [0019]    In general the settings&#39; conflict may not be detected until the action is actually executed by application and the request for which insufficient authorization exists is communicated to the server. Moreover, and importantly, sometimes denial of action/request is unexpected by the client application in terms of software implementation (such as exceptions handling) or application logic. Given the variety of ways to deny the requested action (listed above), an unexpected denial may lead the application at the “client” side to enter into an unexpected state, for example that of termination, reboot, an infinite loop, crash, or freeze while waiting for further response. While application designers endeavor to anticipate and minimize such responses, the nature of software design does not render it inevitable that all such interactions are anticipated. 
         [0020]    This is particularly evident in the live deployments of multi-user client applications, for example call centers, with the client application configurations periodically undergoing change by users/consumers, wherein there is no realistic way to make a “dry run” on all possible mismatch situations during configuration, deployment, or development/testing phases. Further, even if the client application is properly configured for a given server configuration, the permission settings on the server (network entity) are also subject to change due independent of the client application, which could potentially leads to a critical (for the client application) mismatch again. 
         [0021]    Therefore, it would be desirable to obtain a networking implementation wherein authorization denials would be less likely to result in client-applications failing in an undesirable manner. 
       SUMMARY OF THE INVENTION  
       [0022]    It is an object of the invention to provide improved request denial system for client-server applications running across a network. 
         [0023]    According to an aspect of the invention there is provided a system for providing soft-denial of client-application requests over a network supporting client-server interactions between network entities. In the disclosed system there may be found a client-application; a server-application; and a network connecting the client-application to the server-application. A request originating from the client-application is communicated across the network to the server-application. In the case that the server-application determines that the client-application does not have sufficient authorization to allow the request to be satisfied; the server-application produces a denial message to be communicated across the network to the client-application. There may also be found within the system a soft-denial application which intercepts the denial message and replaces the message with an innocuous message which is communicated to said client-application in the place of the denial message. 
         [0024]    In some embodiments of the invention the network is a telecommunications network. 
         [0025]    Advantageously, in telecommunications networks, the client-server interactions support Voice-over-IP services. 
         [0026]    In a particular embodiment the innocuous message results in an aborting of the request processing by the initiative, under control and at the client-application while preserving a protocol stack connecting the client-application to the network. 
         [0027]    According to another aspect of the invention there is provided a method for providing soft-denial of client-application actions over a network supporting client-server interactions between network entities. The method includes the steps of receiving an original action request from a client-application directed to another network entity; determining that said request should be denied due to insufficient authorization; providing a denial response for the client-application; translating the denial response into an innocuous response; and forwarding the innocuous response to the client-application. 
         [0028]    Some embodiments of the invention include having the innocuous response comprising not forwarding the denial response, thereby resulting in a time-out condition by the client-application. 
         [0029]    Advantageously, in some embodiments of the invention the innocuous response results in an aborting of the request processing at the client-application side while preserving the protocol stack connecting the client-application to the network. 
         [0030]    A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0031]    The present invention will be further understood from the following detailed description of embodiments of the invention, with reference to the drawings in which: 
           [0032]      FIGS. 1   a  and  1   b  illustrate a client-server networking system in accordance with the prior art; and 
           [0033]      FIG. 2  illustrates a client-server networking system in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0034]    Referring to  FIG. 1   a , there may be seen a structural block diagram of a client-server network according to the prior art wherein the client-application  110  is in communication with a server-application  100  over network  120 . The client-application connects through appropriate protocols  114  to the network  120 , and likewise the server-application  100  connections through appropriate protocols  104  to the network  120 . 
         [0035]    Referring to  FIG. 1   b , there may be seen an exchange of messages between the client-application  110  and server-application  100  over the client-server network of  FIG. 1   a . A client-application request  150  is communicated across the network  120  to server-application  100 . In result of request  150 , server-application  100  provides a response  160  which is communicated across the network  120  to the client-application  110 . 
         [0036]    On the occasion that server-application  100  does not recognize client-application  110  as having the authority to obtain the requested action (resource, access, service, or other provision), response  160  will be some form of denial response. In the case that client-application  110  is not expecting a denial response, the subsequent actions of client-application  110  are not determined and may result in compromised operation. 
         [0037]    Referring now to  FIG. 2 , there may be seen a diagram of a client-server network according to an embodiment of the invention. Client-application  210  is connected via protocol  214  to network  220 , and likewise server-application  200  is connected to network  220  via protocol  204 . Client-application request  250  is communicated across network  220  to server-application  200 , and server-application  200  provides response  260  in answer to request  250 . A new element, soft-denial application  230 , monitors response  260 , and in the case where response  260  constitutes a denial, soft-denial application  230  translates the denial into a soft-denial  264 . 
         [0038]    In the network, soft-denial application  230  can be implemented within either the originator of the denial i.e. server-application  200 , or by a protocol-aware mediator in the network between the client-application  210  and server-application  200 , such as firewall, proxy, SBC, IPS, or similar entity or application. 
         [0039]    It is important to notice that resolving the denial via requesting or re-requesting authentication credentials is not a useful option here. This is because the original problem occurs due to an authorization (allowed action configuration) mismatch, even though the identity (authentication) was already successfully verified. The mismatch is not one of identity, but instead one of expectations between what client-application  210  considers as a normal operational request, and what the server-application  200  deems as an unauthorized request. 
         [0040]    According to one contemplated embodiment, the mode is implemented at the communication protocol level. Safety for the client is achieved by modifying the rejecting response so that:
       the response looks syntactically and semantically as a neutral or acknowledgement type of message, so that the protocol stack and application logic and processing at the client side is not affected;   the response may suspend the client application from further processing;   at the same time, processing of the request at the server side is aborted.       
 
         [0044]    Several alternative versions of soft-denial messages may be employed to meet and implement three requirements above. 
         [0045]    According to one embodiment, the soft-denial may be effected by assigning a known to be non-existing message type (i.e. unknown, not valid in the protocol concerned) to the rejection/denial application response. The use of this message type is appropriate for applications where it is known that the client-application has a graceful response to unknown message types. The reception of this unknown message type forces the client-application to halt/suspend the process execution, and terminate later on under its own initiative and control. Such assignment/modification can be done either by the rejection originating server-application  200  or by the intermediate protocol-aware network entity, soft-denial application  230 . 
         [0046]    According to another embodiment, the soft denial may be implemented at the protocol headers/fields semantics level wherein the “soft-denial” response message presents formal acknowledgement of the action/request accepting, as if no authorization mismatch was found. However, in addition, the response will possess a new embedded informational metadata piece/string in the payload which is effectively a conventional sign for the client-application  210 . This string indicates “not authorized/settings mismatch”. This gives to the protocol stack and to other parts of the client-application  210  (those parts that are not authorization-aware, but just executing with the expectation that authorization is adequate) the impression that everything is operating as expected and nothing is suddenly broken. The client-application  210  may or may not be modified to understand this sign in order to stop action execution. In the latter case where the client-application  210  is not modified, the client-application  210  may ignore the sign or reject the whole message which would bring us to the first option above. 
         [0047]    According to a third embodiment, the soft-denial may be implemented by blocking the rejection response from arriving at the client-application  210 . For the client-application  210  it will appear as-if the server-application  200  is ignoring the request  250 . This may result in a repeat of the request but will ultimately enforce termination by time-out on the client-application  210  as soft-denial application  230  continues to block the denial messages from server-application  200 . 
         [0048]    A common characteristic of soft-denial responses is that to the client-application they are innocuous responses. 
         [0049]    A specific application of the soft-denial application is in a VoIP (Voice over IP) system providing call service across a network. In a VoIP system implemented over SIP (Session Initiation Protocol) via SBC (Server Based Computing) it is possible to actively intervene with the communication protocols; for instance, SIP B2BUA (Session Initiation Protocol Back-to-Back User Agent) terminates and originates SIP dialogs, and in doing so it can generate new messages or alternate the existing ones. 
         [0050]    Being SIP-aware, an SBC system can implement soft-denial application  230  via monitoring UAS (User Agent Server) “rejecting” denial response messages. By way of example, denial messages such as “488 Not Acceptable Here”, “503 Service Unavailable”, “603 Decline”, “606 Not Acceptable”, and also those denial messages within SIP NOTIFY message body. In this embodiment of the invention, the soft-denial application  230  can translate them to a SIP “ACK_Not_Configured_To” message. An example of an instance wherein a denial message might arise in a VoIP system is where the client-application  210  phone agent&#39;s attempt to forward the call or to get a third party to join the call is not authorized by the policy set on the other server-application  200  side. 
         [0051]    According to another application, protocol-aware firewalls are widely used within enterprise networks. They may have embedded ALG (application level gateways) and inspect/monitor packets of VoIP signaling, FTP, HTTP and others at Layer 7. Utilizing a soft-denial application  230 , a firewall can block “rejecting” response messages of the concerned protocol, thus eventually enforcing timeout on the client-application  210 . 
         [0052]    According to yet another application of the invention, in many client-server application environments operation system environment files are accessed by applications via Operating System function calls, and access permissions are controlled by Operating System and file properties. If an particular application requests a read-access to read from a file, and the Operating System does not consider the application as authorized to access that file, the Operating System provides an authorization error in return. Should the application may not be expecting an authorization error and should no correct exception handling be prepared, problematic results may ensue. With OS kernel patched with the soft-denial application  230 , the authorization error response could be translated instead to an “end_of_file” which the application would interpret as an empty file, a response which could be gracefully handled. The same response can apply to network communication over FTP. 
         [0053]    Large enterprise networks with interconnected sites, services and endpoints are contemplated as the most apparent place for implementation of the presented concept as SBCs (Server Based Computing systems), firewalls, SIP (Session Initiation Protocol) servers, proxies, databases, IPSs (Intrusion Prevention Systems) are commonly found to be deployed within or at the perimeter of enterprise networks. 
         [0054]    The presence of a soft-denial application is safer for end user applications, in particular for those configured independently of the server-application and especially those configured by end user&#39;s discretion. 
         [0055]    The soft-denial application can be fruitfully employed to enable a “network trial/debug” mode for starting up new network deployments, applications, or distributed configurations. Of particular use in this context would be an enabling/disabling mechanism for the soft-denial application, wherein during times of reconfiguration and change the soft-denial application could be engaged as a form of safety net, and once confidence was established, the soft-denial application could be disabled to reduce the network processing overhead. 
         [0056]    Numerous modifications, variations and adaptations may be made to the embodiments of the invention described above without departing from the scope of the invention, which is defined in the claims here below appended.