XML Security Elisa Bertino CERIAS and CS ECE Departments Purdue University Elisa Bertino Pag 1 Purdue University Outline Security requirements for web data Basic concepts of XML Security policies for XML data protection and release Access control mechanisms for XML data XML based specification of security information XML security future trends Elisa Bertino Pag 2 Purdue University Web Data Protection Requirements The web is becoming the main information dissemination means for many organizations Strong need for models and mechanisms enabling the specification and enforcement of security policies for web data protection and release Elisa Bertino Pag 3 Purdue University Web Docs Protection Requirements Web documents may have a nested or hierarchical inter linked structure Different portions of the same document may have different protection requirements We need a wide spectrum of protection granularity levels Elisa Bertino Pag 5 Purdue University Web Docs Protection Requirements Web documents may have an associated intensional description of their structure DTDs and XMLSchemas for XML documents Data models for describing the logical organization of data into web pages Policies specified both at the schema and at the instance level Elisa Bertino Pag 6 Purdue University Web Docs Protection Requirements Documents with the same type and structure may have contents of different sensitivity degree Policies that take the document content into account content based policies Elisa Bertino Pag 7 Purdue University Web Docs Protection Requirements Supporting fine grained policies could lead to the specification of a possibly high number of access control policies Need of mechanisms for exception management and authorization propagation Elisa Bertino Pag 8 Purdue University Web Docs Protection Requirements Heterogeneity of subjects Subjects accessing a web source may be characterized by different skills and needs and may dynamically change Conventional identity based access control schemes are not enough Credentials based on subject characteristics and qualifications Elisa Bertino Pag 9 Purdue University Web Docs Protection Requirements In a web environment the traditional on user demand mode of performing access control is not enough Security policies enforcing both the pull and push dissemination modes Elisa Bertino Pag 10 Purdue University Dissemination Policies PULL Request View PUSH Elisa Bertino Web Data Source Web Data Source Pag 11 Purdue University Outline Security requirements for web data Basic concepts of XML Security policies for XML data protection and release Access control mechanisms for XML data XML based specification of security information XML security future trends Elisa Bertino Pag 12 Purdue University Why XML Because XML is becoming a standard for data representation over the web XML compatibility is thus an important requirement for security policies models and mechanisms for Web data sources Elisa Bertino Pag 13 Purdue University XML Building blocks of XML are tagged elements that can be nested at any depth in the document structure Each tagged element has zero or more subelements and zero or more attributes Elements can be linked by means of IDREF S attributes Optional presence of a DTD XMLSchema for describing the structure of documents wellformed vs valid documents Elisa Bertino Pag 14 Purdue University An XML Document WorldLawBulletin Date 8 8 1999 Law Country USA RelatedLaws LK75 Topic Taxation Topic Summary Summary Law Law Id LK75 Country Italy Topic Import Export Topic Summary Summary Law BluePageReport Section GeoArea Europe Law Country Germany Topic Guns Topic Summary Summary Law Section Section GeoArea NorthAmerica Law Country USA Topic Transportation Topic Summary Summary Law Section BluePageReport WorldLawBulletin Graph Representation WordLawBulletin Date 08 08 1999 1 Law Country USA 2 Topic 3 Taxation BluePageReport Law Country Italy LK75 7 Summary Section Section Topic GeoArea E RelatedLaws Summary 4 5 6 8 Law Import Export 9 GeoArea NorthA Law Country Germany 10 13 Country USA Summary Topic Summary Topic 11 Guns Elisa Bertino Pag 16 12 14 15 Transportation Purdue University An XML DTD DOCTYPE ELEMENT ELEMENT ELEMENT ELEMENT ELEMENT ELEMENT WorldLawBulletin WorldLawBulletin Law BluePageReport Law Topic Summary Topic PCDATA Summary ANY BluePageReport Section Section Law ATTLIST WorldLawBulletin Date CDATA REQUIRED ATTLIST Law Id ID REQUIRED Country CDATA REQUIRED RelatedLaws IDREFS IMPLIED ATTLIST Section GeoArea CDATA REQUIRED XML Security Two main issues 1 Development of access control models techniques mechanisms and systems for protecting XML documents 2 Use of XML to specify security relevant information organizational policies subject credentials authentication information encrypted contents Elisa Bertino Pag 18 Purdue University The Author X Project Joint work with Elisa Bertino Silvana Castano and Marco Mesiti Elisa Bertino Pag 19 Purdue University Author X Java based system for XML data sources protection Security policy design and administration Credential based access control to XML document sources Secure document dissemination and update Elisa Bertino Pag 20 Purdue University Author X ACPs Set oriented and document oriented policies Positive and negative policies at different granularity levels to enforce differentiated protection of XML documents and DTDs Controlled propagation of access rights ACPs reflect user profiles through credentialbased qualifications Elisa Bertino Pag 21 Purdue University Enforcing access control Subject specification Protection object specification Privilege Propagation option Elisa Bertino Pag 22 Purdue University Subject Specification User Identifiers OR Subject credential credential expression Ex X age 21 Programmer X and X country Italy Elisa Bertino Pag 23 Purdue University Protection Object Specification Identify the portions of a document s to which the authorization applies We want to allow users to specify authorizations ranging from from sets of documents to single elements attributes within documents specification on DTD or documents doc DTD pathOfElem ElemIds Attrs links Elisa Bertino Pag 24 Purdue University Privileges browsing authoring Elisa Bertino read navigate write append delete Pag 25 Purdue University Propagation option NO PROPAGATION Elisa Bertino Pag 26 Purdue University Propagation option FIRST LEVEL Elisa Bertino Pag 27 Purdue University Propagation option CASCADE Elisa Bertino Pag 28