Interoperable identity and trust management infrastructure plays an important role in enabling integrations in cloud computing environments. In the past decade or so, several web-based workflows have emerged as de-facto standards for user identity and resource access across enterprises. Establishing correctness of such web protocols is of immense importance to a large number of common business transactions on the web. In this paper, we propose a framework for analyzing security in web protocols. A novel aspect of our proposal is bringing together two contrasting styles used for security protocol analysis. We use the inference construction style, in which the well-known BAN logic has been extended to reason about web protocols, in conjunction with, an attack construction style that performs SAT based modelchecking to rule out certain active attacks. The result is an analysis method that shares simplicity and intuitive appeal of belief logics, at the same time covers a wider range of protocols, along with an ability to automatically find attacks. To illustrate effectiveness, case study of a leading web identity and access management protocol is presented, where application of our analysis method results in a previously unreported attack being identified. Copyright 2012 ACM.