The XML Path Language (or XPath) is an interpreted language used for navigating around XML documents, and for retrieving data from within them. In most cases, an XPath expression represents a sequence of steps that is required to navigate from one node of a document to another. Where web applications store data within XML documents, … Read more
The Simple Object Access Protocol (SOAP) is a message-based communications technology that uses the XML format to encapsulate data. It can be used to share information and transmit messages between systems, even if these run on different operating systems and architectures. Its primary use is in web services, and in the context of a browser-accessed … Read more
Many scripting languages support the use of include files. This facility enables developers to place reusable code components into individual files, and to include these within function-specific code files as and when they are needed. The code within the included file is interpreted just as if it had been inserted at the location of the … Read more
The core logic of most web applications is written in interpreted scripting languages like PHP, VBScript, and Perl. In addition to the possibilities for injecting into languages used by other back-end components, a key area of vulnerability concerns injection into the core application code itself. Exposure to this type of attack arises from two main … Read more
In some situations, an application that is vulnerable to SQL injection may implement various input filters that prevent you from exploiting the flaw without restrictions. For example, the application may remove or sanitize certain characters, or may block common SQL keywords. Filters of this kind are often vulnerable to bypasses, and there are numerous tricks … Read more
If you are attacking an MS-SQL database, then there are alternative ways available of discovering the names of database tables and columns, and of extracting useful data. MS-SQL generates extremely verbose error messages, which can be exploited in various ways. Enumerating Table and Column Names Recall the login function described earlier, which performs the following SQL … Read more
In order to extract useful data from the database, you normally need to know the names of the tables and columns containing the data you wish to access. The main enterprise DBMS’s contain a rich amount of database metadata that you can query to discover the names of every table and column within the database. … Read more
Most of the techniques described so far are effective against all of the common database platforms, and any divergences have been accommodated through minor adjustments to syntax. However, as we begin to look at more advanced exploitation techniques, the differences between platforms become more significant, and you will increasingly need to know which type of … Read more
The UNION operator is used in SQL to combine the results of two or more SELECT statements into a single result set. When a web application contains a SQL injection vulnerability that occurs in a SELECT statement, you can often employ the UNION operator to perform a second, entirely separate query, and combine its results with … Read more
In the most obvious cases, a SQL injection flaw may be discovered and conclusively verified by supplying a single item of unexpected input to the application. In other cases, bugs may be extremely subtle and may be difficult to distinguish from other categories of vulnerability or from benign anomalies that do not present any security … Read more