How Safe is Your Web Service

You are probably using several software applications that talk to each other.  Whether you have a custom web application or prepackaged financial solution, getting applications and services to communicate requires a skill, technique, and knowledge to protect your information.  So, what happens when your web service is not secure? What information could you be leaking and how could you be vulnerable?

Security Concerns

The four concerns of web service security are privacy, message integrity, authentication, and authorization.

  • Privacy refers to ensuring that messages are not visible to anyone except the web service and the web service consumer. Traffic should be encrypted so that machines in the middle cannot read the messages.
  • Message integrity provides a guarantee that the message received has not been tampered with during transmission.
  • Authentication provides assurances that the message originates from where it claims it did. Both a legal term as well as a technical term, non-repudiation refers to the concern of not only authenticating a message, but proving the origin of that message to other parties.
  • Authorization refers to ensuring that only consumers who should have access to a resource of your web service actually have access to that resource. Authorization requires authentication because without authentication an attacker could pretend to be a highly privileged user.

Building a web service or API (application programming interface) requires a methodology for exchanging secure information, and there are two popular solutions: SOAP and REST.

Technology Choices

Simple Object Access Protocol (SOAP) is a popular protocol specification. It is a complicated specification and some developers, though well-meaning, leave security vulnerabilities.  An example of a vulnerability is SOAP injection. What is SOAP injection? It occurs when the server attempts to parse the XML message from a client. If the XML message is malformed, meaning that it does not follow the rules that the server expects it to follow, the server may return an error message that actually shows code and gives insight into the underlying system. Developers may turn off this behavior. However, this is often forgotten before a deployment.

REST (Representational State Transfer) is an architectural style for distributed systems. The World Wide Web is one such distributed system. REST has become a popular architectural choice for designing web services. Such web services are referred to as RESTful web services. An advantage of using REST is that the security vulnerabilities are well known as they are the same vulnerabilities that impact web sites. This means that developers who are familiar with website security will be able to leverage their knowledge to secure RESTful web services.

Final Thoughts

Developers working with either of these technologies must be concerned with the four security points. No methodology or architectural choice ensures that your information is well-protected. It is important that your consultants explain the architecture they plan to use and how their implementation plan accounts for security concerns. If your developer does not have a detailed answer, it is a red flag.