Secure Querying of Recursive XML Views: A Standard XPath-based Technique

Most state-of-the art approaches for securing XML documents allow users to access data only through authorized views defined by annotating an XML grammar (e.g. DTD) with a collection of XPath expressions. To prevent improper disclosure of confidential information, user queries posed on these views need to be rewritten into equivalent queries on the underlying documents. This rewriting enables us to avoid the overhead of view materialization and maintenance. A major concern here is that query rewriting for recursive XML views is still an open problem. To overcome this problem, some works have been proposed to translate XPath queries into non-standard ones, called Regular XPath queries. However, query rewriting under Regular XPath can be of exponential size as it relies on automaton model. Most importantly, Regular XPath remains a theoretical achievement. Indeed, it is not commonly used in practice as translation and evaluation tools are not available. In this paper, we show that query rewriting is always possible for recursive XML views using only the expressive power of the standard XPath. We investigate the extension of the downward class of XPath, composed only by child and descendant axes, with some axes and operators and we propose a general approach to rewrite queries under recursive XML views. Unlike Regular XPath-based works, we provide a rewriting algorithm which processes the query only over the annotated DTD grammar and which can run in linear time in the size of the query. An experimental evaluation demonstrates that our algorithm is efficient and scales well.Comment: (2011

A General Approach for Securely Querying and Updating XML Data

Over the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A few amount of works have studied the access rights for updates. In this paper, we present a general model for specifying access control on XML data in the presence of update operations of W3C XQuery Update Facility. Our approach for enforcing such updates specifications is based on the notion of query rewriting where each update operation defined over arbitrary DTD (recursive or not) is rewritten to a safe one in order to be evaluated only over XML data which can be updated by the user. We investigate in the second part of this report the secure of XML updating in the presence of read-access rights specified by a security views. For an XML document, a security view represents for each class of users all and only the parts of the document these users are able to see. We show that an update operation defined over a security view can cause disclosure of sensitive data hidden by this view if it is not thoroughly rewritten with respect to both read and update access rights. Finally, we propose a security view based approach for securely updating XML in order to preserve the confidentiality and integrity of XML data.Comment: No. RR-7870 (2012

Efficient Access Control to XML Data : Querying and Updating Problems

Le langage XML est devenu un standard de représentation et d'échange de données à travers le web. Le but de la réplication de données au sein de différents sites est de minimiser le temps d'accès à ces données partagées. Cependant, différents problèmes sont liés à la sécurisation de ces données. Le but de cette thèse est de proposer des modèles de contrôles d'accès XML qui prennent en compte les droits de lecture et de mise-à-jour et qui permettent de surmonter les limites des modèles qui existent. Nous considérons les langages XPath et XQuery Update Facility pour la formalisation des requêtes d'accès et des requêtes de mise-à-jour respectivement. Nous donnons des descriptions formelles de nos modèles de contrôles d'accès et nous présentons des algorithmes efficaces pour le renforcement des politiques de sécurité spécifiées à la base de ces modèles. L'autre partie de cette thèse est consacrée à l'étude pratique de nos propositions. Nous présentons notre système appelé SVMAX qui met en oeuvre nos solutions, et nous conduisons une étude expérimentale basée sur une DTD réelle pour montrer son efficacité. Plusieurs systèmes de bases de données natives (systèmes de BDNs) ont été proposés récemment qui permettent une manipulation efficace des données XML en utilisant la plupart des standards du W3C. Nous montrons que notre système SVMAX peut être intégré facilement et efficacement au sein d'un large ensemble de systèmes de BDNs. A nos connaissances, SVMAX est le premier système qui permet la sécurisation des données XML conformes à des DTDs arbitraires (récursives ou non) et ceci en moyennant un fragment significatif de XPath et une classe riche d'opérations de mise-à-jour XMLXML has become a standard for representation and exchange of data across the web. Replication of data within different sites is used to increase the availability of data by minimizing the access's time to the shared data. However, the safety of the shared data remains an important issue. The aim of the thesis is to propose some models of XML access control that take into account both read and update rights and that overcome limitations of existing models. We consider the XPath language and the XQuery Update Facility to formalize respectively user access queries and user update operations. We give formal descriptions of our read and update access control models and we present efficient algorithms to enforce policies that can be specified using these models. Detailed proofs are given that show the correctness of our proposals. The last part of this thesis studies the practicality of our proposals. Firstly, we present our system, called SVMAX, that implements our solutions and we conduct an extensive experimental study, based on real-life DTD, to show that it scales well. Many native XML databases systems (NXD systems) have been proposed recently that are aware of the XML data structure and provide efficient manipulation of XML data by the use of most of W3C standards. Finally, we show that our system can be integrated easily and efficiently within a large set of NXD systems, namely BaseX, Sedna and eXist-db. To the best of our knowledge, SVMAX is the first system for securing XML data in the presence of arbitrary DTDs (recursive or not), a significant fragment of XPath and a rich class of XML update operation

Contrôle d’Accès Efficace pour des Données XML: problèmes d’interrogation et de mise-à-jour

Over the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A small number of works have studied the access rights for updates.In this chapter, we present a general and expressive model for specifying access control on XML data in the presence of the update operations of W3C XQuery Update Facility. Our approach for enforcing such update specification is based on the notion of query rewriting. A major issue is that, in practice, query rewriting for recursive DTDs is still an open problem. We show that this limitation can be avoided using only the expressive power of the standard XPath, and we propose a linear algorithm to rewrite each update operation defined over an arbitrary DTD (recursive or not) into a safe one in order to be evaluated only over the XML data which can be updated by the user.To our knowledge, this work is the first effort for securely XML updating in the presence of arbitrary DTDs, a rich class of update operations, and a significant fragment of XPath. Finally, we thoroughly study the interaction between read and update access rights to preserve the confidentiality and integrity of XML data.Durant ces dernières années, plusieurs travaux ont proposé des modèles de contrôle d'accès pour sécuriser l'accès en lecture aux données XML, basés seulement sur des DTDs non-récursives. Le contrôle d'accès XML considérant les opérations de mise à jour n'a pas reçu suffisamment d'attention. Dans ce travail, nous présentons un modèle général pour spécifier le contrôle d'accès aux données XML moyennant des primitives de mise à jour du W3C XQuery Update Facility. Notre approche pour renforcer ces spécifications de mise à jour est basée sur la notion de réécriture des requêtes (query rewriting en anglais). Cependant, la réécriture des requêtes dans le cas des DTDs récursives reste un problème ouvert. Pour pallier à ce problème, nous proposons un algorithme linéaire, basé seulement sur le standard XPath, et qui permet de réécrire chaque opération de mise à jour, définie par rapport à une DTD arbitraire (récursive ou non), en une autre opération sûre afin qu'elle soit évaluée seulement sur des données XML modifiables par l'utilisateur qui a soumis l'opération. Ce travail représente le premier effort autour de la sécurisation des opérations de mise à jour XML dans la présence des DTDs arbitraires, une classe importante d'opérations de mise à jour, et un fragment riche de XPath. Nous étudions dans le reste de ce travail l'interaction entre les droits de lecture et de mise à jour, et nous décrivons une solution qui permet de préserver la confidentialité et l'intégrité des données XML

Efficient Querying of XML Data Through Arbitrary Security Views

International audienceWe study the problem of querying virtual security views of XML data that has received a great attention during the past years. A major concern here is that user XPath queries posed on recursive views cannot be rewritten to be evaluated on the underlying XML data. Existing rewriting solutions are based on the non-standard language, “Regular XPath”, which makes rewriting possible under recursion. However, query rewriting under Regular XPath can be of exponential size. We show that query rewriting is always possible for arbitrary security views (recursive or not) by using only the expressive power of the standard XPath. We propose a more expressive language to specify XML access control policies as well as an efficient algorithm to enforce such policies. Finally, we present our system, called SVMAX, that implements our solutions and we show that it scales well through an extensive experimental study based on real-life DTD

A General Approach for Securely Updating XML Data ∗

Over the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A small number of works have studied the access rights for updates. In this paper, we present a general model for specifying access control on XML data in the presence of the update operations of W3C XQuery Update Facility. Our approach for enforcing such update specification is based on the notion of query rewriting. A major issue is that query rewriting for recursive DTDs is still an open problem. We show that this limitation can be avoided using only the expressive power of the standard XPath, and we propose a linear algorithm to rewrite each update operation defined over an arbitrary DTD (recursive or not) into a safe one in order to be evaluated only over the XML data which can be updated by the user. This paper represents the first effort for securely XML updating in the presence of arbitrary DTDs (recursive or not) and a rich fragment of XPath

On Securely Manipulating XML Data

National audienceOver the past years several works have proposed access control models for XML data where only read-access rights over non-recursive DTDs are considered. A small number of works have studied the access rights for updates. In this paper, we present a general model for specifying access control on XML data in the presence of the update operations of W3C XQuery Update Facility. Our approach for enforcing such update spec- ification is based on the notion of query rewriting. A major issue is that query rewriting for recursive DTDs is still an open problem. We show that this limitation can be avoided using only the expressive power of the standard XPath, and we propose a linear algorithm to rewrite each update operation defined over an arbitrary DTD (recursive or not) into a safe one in order to be evaluated only over the XML data which can be updated by the user. This paper represents the first effort for securely XML updating in the presence of arbitrary DTDs (recursive or not) and a rich fragment of XPath. Finally, we study the interaction between read and update access rights to preserve the confidentiality and integrity of XML data

Efficient Access Control to XML Data (Querying and Updating Problems)

Le langage XML est devenu un standard de représentation et d'échange de données à travers le web. Le but de la réplication de données au sein de différents sites est de minimiser le temps d'accès à ces données partagées. Cependant, différents problèmes sont liés à la sécurisation de ces données. Le but de cette thèse est de proposer des modèles de contrôles d'accès XML qui prennent en compte les droits de lecture et de mise-à-jour et qui permettent de surmonter les limites des modèles qui existent. Nous considérons les langages XPath et XQuery Update Facility pour la formalisation des requêtes d'accès et des requêtes de mise-à-jour respectivement. Nous donnons des descriptions formelles de nos modèles de contrôles d'accès et nous présentons des algorithmes efficaces pour le renforcement des politiques de sécurité spécifiées à la base de ces modèles. L'autre partie de cette thèse est consacrée à l'étude pratique de nos propositions. Nous présentons notre système appelé SVMAX qui met en oeuvre nos solutions, et nous conduisons une étude expérimentale basée sur une DTD réelle pour montrer son efficacité. Plusieurs systèmes de bases de données natives (systèmes de BDNs) ont été proposés récemment qui permettent une manipulation efficace des données XML en utilisant la plupart des standards du W3C. Nous montrons que notre système SVMAX peut être intégré facilement et efficacement au sein d'un large ensemble de systèmes de BDNs. A nos connaissances, SVMAX est le premier système qui permet la sécurisation des données XML conformes à des DTDs arbitraires (récursives ou non) et ceci en moyennant un fragment significatif de XPath et une classe riche d'opérations de mise-à-jour XMLXML has become a standard for representation and exchange of data across the web. Replication of data within different sites is used to increase the availability of data by minimizing the access's time to the shared data. However, the safety of the shared data remains an important issue. The aim of the thesis is to propose some models of XML access control that take into account both read and update rights and that overcome limitations of existing models. We consider the XPath language and the XQuery Update Facility to formalize respectively user access queries and user update operations. We give formal descriptions of our read and update access control models and we present efficient algorithms to enforce policies that can be specified using these models. Detailed proofs are given that show the correctness of our proposals. The last part of this thesis studies the practicality of our proposals. Firstly, we present our system, called SVMAX, that implements our solutions and we conduct an extensive experimental study, based on real-life DTD, to show that it scales well. Many native XML databases systems (NXD systems) have been proposed recently that are aware of the XML data structure and provide efficient manipulation of XML data by the use of most of W3C standards. Finally, we show that our system can be integrated easily and efficiently within a large set of NXD systems, namely BaseX, Sedna and eXist-db. To the best of our knowledge, SVMAX is the first system for securing XML data in the presence of arbitrary DTDs (recursive or not), a significant fragment of XPath and a rich class of XML update operationsNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

SVMAX: a system for secure and valid manipulation of XML data

International audienceIt is increasingly common to find XML views used to enforce access control as found in many applications and commercial database systems. To overcome the overhead of view materialization and maintenance, XML views are necessarily virtual. With this comes the need for answering XML queries posed over virtual views, by rewriting them into equivalent queries on the underlying documents. A major concern here is that query rewriting for recursive XML views is still an open problem, and proposed approaches deal only with non-recursive XML views. Moreover, a small number of works have studied the access rights for updates. In this paper, we present SVMAX (Secure and Valid MAnipulation of XML), the first system that supports specification and enforcement of both read and update access policies over arbitrary XML views (recursive or non). SVMAX defines general and expressive models for controlling access to XML data using significant class of XPath queries and in the presence of the update primitives of W3C XQuery Update Facility. Furthermore, SVMAX features an additional module enabling efficient validation of XML documents after primitive updates of XQuery. The wide use of W3C standards makes of SVMAX a useful system that can be easily integrated within commercial database systems as we will show. We give extensive experimental results, based on real-life DTDs, that show the efficiency and scalability of our system.Nous présentons un système de contrôle d'accès pour documents XML par récriture de requête qui fonctionne aussi sur les vues récursives