CRV2 SQLInjPHP

Introduction
An SQL injection Attack consists of injecting sql query portions in the back-end database system via the client interface in the web application. The consequence of a successful exploitation of an SQL injection varies from just reading data to modifying data or executing system commands. SQL Injection in PHP remains the number one attack vector, and also the number on reason for DATA COMPROMISES

Data Validation
All external input to the system should undergo input validation. The validation rules are defined by the business requirements for the application. If possible, an exact match validator should be implemented. Exact match only permits data that conforms to an expected value. A "Known good" approach (white-list), which is a little weaker, but more flexible, is common. Known good only permits characters/ASCII ranges defined within a white-list. Such a range is defined by the business requirements of the input field. The other approaches to data validation are "known bad," which is a black list of "bad characters". This approach is not future proof and would need maintenance. "Encode bad" would be very weak, as it would simply encode characters considered "bad" to a format which should not affect the functionality of the application.

Business Validation
Business validation is concerned with business logic. An understanding of the business logic is required prior to reviewing the code which performs such logic. Business validation could be used to limit the value range or a transaction inputted by a user or reject input which does not make too much business sense. Reviewing code for business validation can also include rounding errors or floating point issues which may give rise to issues such as integer overflows which can dramatically damage the bottom line.

Canonicalization
Canonicalization is the process by which various equivalent forms of a name can be resolved to a single standard name, or the "canonical" name.

The most popular encodings are UTF-8, UTF-16, and so on (which are described in detail in RFC 2279). A single character, such as a period/full-stop (.), may be represented in many different ways: ASCII 2E, Unicode C0 AE, and many others.

With the myriad ways of encoding user input, a web application's filters can be easily circumvented if they're not carefully built.

Bad Example
public static void main(String[] args) { File x = new File("/cmd/" + args[1]); String absPath = x.getAbsolutePath; }

Good Example
public static void main(String[] args) throws IOException { File x = new File("/cmd/" + args[1]); String canonicalPath = x.getCanonicalPath; }