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Francois Lascelles

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Top Stories by Francois Lascelles

Imagine a fresh business relationship between ACME Corporation and Partner. As a result of this relationship, ACME wants to grant Partner limited access to one of its core internal applications. They do this, naturally, by exposing a Web service. Why Identity Federation? Boris (an employee at Partner) sends a SOAP request to the ACME Web service along with some password or proof-of-possession type credentials. Because Boris's identity is managed outside of ACME, those credentials cannot be authenticated using ACME's authentication infrastructure. To circumvent this issue, one could imagine a setup where the ACME Web service authenticates Boris's credentials by connecting to Partner's authentication services. Another alternative might involve some sort of directory replication. These strategies were attempted in the '90s when distributed LDAP references appeared in t... (more)

Standardize HMAC, OAuth RESTful Authentication Schemes

As the enterprise is increasingly taking notice of WOA (Web Oriented Architecture) these days, the need for security guidelines and standards for RESTful Web services is becoming more pressing. Sure, RESTful Web services are meant to borrow existing security mechanisms from the web and HTTP Basic over SSL, when done right, is a great way to accomplish shared-secret based authentication. Yet, for better or for worse, it is common to find REST API providers defining their own authentication mechanisms. Take for example the Amazon S3 REST API’s custom HTTP authentication scheme. Us... (more)

REST JSON to SOAP Conversion Tutorial

I often get asked about ‘REST to SOAP’ transformation use cases these days. Using an SOA gateway like SecureSpan to perform this type of transformation at runtime is trivial to setup. With SecureSpan in front of any existing web service (in the DMZ for example), you can virtualize a REST version of this same service. Using an example, here is a description of the steps to perform this conversion. Imagine the geoloc web service for recording geographical locations. It has two methods, one for setting a location and one for getting a location. See below what this would look like i... (more)

WS Security Performance

The WS Secure Conversation specification describes a mechanism letting multiple parties establish a context (using the WS Trust Request Security Token standard) and secure subsequent SOAP exchanges. Each WS Secure Conversation session has an associated shared secret. Instead of using this shared secret directly to sign and encrypt the conversation's messages, symmetric keys are derived from the secret itself. Deriving new keys for each message and different keys for signature and encryption limits the amount of data that an attacker can analyze in attempting to compromise the con... (more)

JSON Schema Validation for RESTful Web Services

In the article "The importance of threat protection for restful web services", I presented a number of content-based threats for XML. When protecting an endpoint from XML based attacks, not only are payloads scanned for code injections, malicious entity declarations and parser attacks, XML documents are actually validated against strict schemas that clearly describe expected document structures. Enforcing this type of compliance at the edge, in a SOA gateway for example, minimizes the risk of attacks of the Web service endpoint. Structure definition languages such as XML Schema ... (more)