Download SQL Injection Attacks and Defense, 2nd Edition By Justin Clake

Sinopsis

People say they know what SQL injection is, but all they have heard about or experienced are trivial examples. SQL injection is one of the most devastating vulnerabilities that impact a business, as it can lead to exposure of all of the sensitive information stored in an application’s database, including handy information such as usernames, passwords, names, addresses, phone numbers, and credit card details.

So, what exactly is SQL injection? It is the vulnerability that results when you give an attacker the ability to influence the Structured Query Language (SQL) queries that an application passes to a back-end database. By being able to influence what is passed to the database, the attacker can leverage the syntax and capabilities of SQL itself, as well as the power and flexibility of supporting database functionality and operating system functionality available to the database. SQL injection is not a vulnerability that exclusively affects Web applications; any code that accepts input from an untrusted source and then uses that input to form dynamic SQL statements could be vulnerable (e.g. “fat client” applications in a client/server architecture). In the past, SQL injection was more typically leveraged against server side databases, however with the current HTML5 specification, an attacker could equally execute JavaScript or other codes in order to interact with a client-side database to steal data. Similarly with mobile applications (such as on the Android platform) malicious applications and/or client side script can be leveraged in similar ways (see labs.mwrinfosecurity.com/notices/webcontentresolver/ for more info).

SQL injection has probably existed since SQL databases were first connected to Web applications. However, Rain Forest Puppy is widely credited with its discovery or at least for bringing it to the public’s attention. On Christmas Day 1998, Rain Forest Puppy wrote an article titled “NT Web Technology Vulnerabilities” for Phrack (www.phrack.com/issues.html?issue=54&id=8#article), an e-zine written by and for hackers. Rain Forest Puppy also released an advisory on SQL injection (“How I hacked PacketStorm,” located at www.wiretrip.net/rfp/txt/rfp2k01.txt) in early 2000 that detailed how SQL injection was used to compromise a popular Web site. Since then, many researchers have developed and refined techniques for exploiting SQL injection. However, to this day many developers and security professionals still do not understand it well.

In this chapter, we will look at the causes of SQL injection. We will start with an overview

of how Web applications are commonly structured to provide some context for understanding

how SQL injection occurs. We will then look at what causes SQL injection in an application at

the code level, and what development practices and behaviors lead us to this.

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