Web Services - OWASPDevelopment Guide Table of Contents. This section of the Development Guide details the common issues facing Web services developers, and methods to address common issues. Due to the space limitations, it cannot look at all of the surrounding issues in great detail, since each of them deserves a separate book of its own. Instead, an attempt is made to steer the reader to the appropriate usage patterns, and warn about potential roadblocks on the way. Web Services have received a lot of press, and with that comes a great deal of confusion over what they really are.
Some are heralding Web Services as the biggest technology breakthrough since the web itself; others are more skeptical that they are nothing more than evolved web applications. In either case, the issues of web application security apply to web services just as they do to web applications.
For example, your Java application has stock information updated every 5 minutes and you would like other applications, ones that may not even exist yet, to be able to use the data. The problem with this approach is that a C# application would not be able to use these objects because it serializes and deserializes objects differently than Java. This is better because a C# application could read the data. But this has another flaw: Lets assume your stock application is not the only one the C# application needs to interact with.
Maybe it needs weather data, local restaurant data, movie data, etc. If every one of these applications uses its own unique file format, it would take considerable research to get the C# application to a working state. A format that any application can use, regardless of the data being transported.
Web Services are this solution. They let any application communicate with any other application without having to consider the language it was developed in or the format of the data. While web applications typically are HTML- based, web services are XML- based. Interactive users for B2. C (business to consumer) transactions normally access web applications, while web services are employed as building blocks by other web applications for forming B2.
The Java space contains technical articles, blogs and discussion forums with questions and answers about Java technologies. Welcome to the Java Community space. Join the forums and engage by asking or answering questions or helping other Java. Security has always been a top issue for all kinds of applications, especially Web applications. Web apps are accessible to almost the entire universe and are open to attack. Web Services is a current hot topic because of its interoperability, ease of consumption, use of standard Web protocols. Hi, I am looking for an good example which shows how to send an soap attachment . Explore the concepts, syntax, commands, and tools that allow you to communicate and share data between applications with Java EE web services. In this course, we'll.
B (business to business) chains using the so- called SOA model. Web services typically present a public functional interface, callable in a programmatic fashion, while web applications tend to deal with a richer set of features and are content- driven in most cases. However, for a number of reasons discussed later in this chapter, WS developers usually have to be at least aware of all these risks, and oftentimes they still have to resort to manually coding or tweaking the protection components. At the same time, there have been so many articles published on the topic of . Therefore, listed below is just a brief rundown of most common pitfalls when using channel security alone. It provides only . There is also a subtle issue of trust transitivity, as trusts between node pairs .
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Storing the transmitted information at the intermediate aggravates the problem or destination servers in log files (where it can be browsed by anybody) and local caches. Using a different server, which is semantically equivalent, but accepts a different format of the same credentials, would require altering the client and prevent forming automatic B2.
B service chains. However, one should clearly realize the limitations of such approach, and make conscious trade- offs at the design time, whether channel, token, or combined protection would work better for each specific case. This is not a problem for username/password types of credentials, but binary ones (like X. Kerberos tokens) require converting them into text prior to sending and unambiguously restoring them upon receiving, which is usually done via a procedure called Base. Therefore, things like passwords and private keys need to be either encrypted, or just never sent . Usual ways to avoid sending sensitive credentials are using cryptographic hashing and/or signatures.
This may be achieved by capturing an entire message, even if it is sufficiently protected against tampering, since it is the message itself that is used for attack now (see the XML Injection section of the Interpreter Injection chapter). In the Web Services world, information about the message creation time is usually communicated by inserting timestamps, which may just tell the instant the message was created, or have additional information, like its expiration time, or certain conditions. A greater issue lies with message queuing at the servers, where messages may be expiring while waiting to be processed in the queue of an especially busy or non- responsive server.
Assuming that the caller trust has been established one way or another, the server has to be assured that the message it is looking at was indeed issued by the caller, and not altered along the way (intentionally or not). This may affect technical qualities of a SOAP message, such as the message's timestamp, or business content, such as the amount to be withdrawn from the bank account. Obviously, neither change should go undetected by the server. This would not be sufficient, however, in the realm of publicly exposed Web Services, since checksums (or digests, their cryptographic equivalents) are easily replaceable and cannot be reliably tracked back to the issuer. The required association may be established by utilizing HMAC, or by combining message digests with either cryptographic signatures or with secret key- encryption (assuming the keys are only known to the two communicating parties) to ensure that any change will immediately result in a cryptographic error.
It may apply to the entire message being processed, or only to certain parts of it; In either case, some type of encryption is required to conceal the content. Normally, symmetric encryption algorithms are used to encrypt bulk data, since it is significantly faster than the asymmetric ones. Asymmetric encryption is then applied to protect the symmetric session keys, which, in many implementations, are valid for one communication only and are subsequently discarded. Normally, signing keys are different from the encrypting ones, primarily because of their different lifecycles, signing keys are permanently associated with their owners, while encryption keys may be invalidated after the message exchange. Another reason may be separation of business responsibilities - the signing authority (and the corresponding key) may belong to one department or person, while encryption keys are generated by the server controlled by members of IT department. Most often, authorization (or entitlement) tasks occur completely outside of the Web Service implementation, at the Policy Server that protects the whole domain.
An organization would need an XML/SOAP firewall, which is capable of conducting application- level analysis of the web server's traffic and make intelligent decision about passing SOAP messages to their destination. The reader would need to refer to other books and publications on this very important topic, as it is impossible to cover it within just one chapter. Normally, this would be achieved by saving server logs in a secure location, available only to the IT administrators and system auditors, in order to create what is commonly referred to as . Web Services are no exception to this practice, and follow the general approach of other types of Web Applications. Following the standard legal practice, electronic documents now require some form of an .
The standard practice is to require cryptographic digital signatures over any content that has to be legally binding, if a document with such a signature is saved in the audit log, it can be reliably traced to the owner of the signing key. Web Services Security Hierarchy. Technically speaking, Web Services themselves are very simple and versatile, XML- based communication, described by an XML- based grammar, called Web Services Description Language (WSDL, see http: //www.
TR/2. 00. 5/WD- wsdl. XML Schema, and operations, to the underlying wire format. Although it is by no means a requirement, the format of choice is currently SOAP over HTTP. This means that Web Service interfaces are described in terms of the incoming and outgoing SOAP messages, transmitted over HTTP protocol. There are quite a few industry- wide groups and consortiums working in this area, most important of which are listed below. Of particular interest to this chapter are XML Schema, SOAP, XML- dsig, XML- enc, and WSDL standards (called recommendations in the W3.
C's jargon). It also operates on a committee basis, forming so- called Technical Committees (TC) for the standards that it is going to be developing. Of interest for this discussion, OASIS owns WS- Security and SAML standards. Mostly its work consists of taking other broadly accepted standards, and developing so- called profiles, or sets of requirements for conforming Web Service implementations. In particular, its Basic Security Profile (BSP) relies on the OASIS' WS- Security standard and specifies sets of optional and required security features in Web Services that claim interoperability. Although this framework is not strictly Web Service- specific, but rather general, it is important for this topic because of its close relation with the SAML standard developed by OASIS. They are usually made up of software industry's leading companies, such as Microsoft, IBM, Verisign, BEA, Sun, and others, that join them to work on a particular issue or proposal.
Results of these joint activities, once they reach certain maturity, are often submitted to standardizations committees as a basis for new industry standards. This information, formatted into Header and Body, can theoretically be transmitted over a number of transport protocols, but only HTTP binding has been formally defined and is in active use today.