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Francois Lascelles

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Top Stories by Francois Lascelles

So twitter’s oauth keys have leaked. What does that mean? Don’t panic. The consequences of a client application’s key being compromised is as serious as user credentials being compromised. The risk associated with this breach is that a malicious application tricking you in participating in an OAuth handshake (fishing) could access the twitter API on your behalf. Attackers might come up with clever ways to exploit this leak. In the meantime, avoid using twitter through any application other than the twitter application itself. OAuth distinguishes between confidential and public clients. Applications that you can publicly download on your own device (mobile or not) fall in the public category because they are subject to their embedded secret being reverse engineered as probably happened in this case. This incident is a good illustration of the fact that client secret... (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)

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)

Flexible Identity Federation XML Gateways to The Rescue

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 cou... (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)