Information Security: SQL Injection Attack (Definitions)

"This is a way that hackers can bring a database down. SQL injection attacks can be avoided by using stored procedures with the appropriate configured parameters." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"An attack on a database made by inserting escape characters or additional commands into a batch, allowing the attacker to run commands on the database server. This exploits poor validation or weak designs in application code that allow extra commands to be submitted to the server." (Marilyn Miller-White et al, "MCITP Administrator: Microsoft® SQL Server™ 2005 Optimization and Maintenance 70-444", 2007)

"An Internet attack against a database accessible via a web page. Automated programs are available to launch attacks, and successful SQL injection attacks can obtain the entire layout of a database and all the data." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"An attack against a database system launched through an application program containing embedded SQL." (Jan L Harrington, "Relational Database Design and Implementation: Clearly explained" 3rd Ed., 2009)

"A type of attack designed to break through database security and access the information. A SQL injection attack “injects” or manipulates SQL code." (Mike Harwood, "Internet Security: How to Defend Against Attackers on the Web 2nd Ed.", 2015)

Data Security: SQL Injection I - Introduction

Introduction

  If you are working in IT, most probably you’ve heard already about SQL Injection, if not then might be it’s a good idea to ask your colleagues and eventually your IT manager if your company has any policies related to it. If you are working for a software vendor or a consultancy company then SQL Injection countermeasure techniques might be quite well positioned in the list of best practices in what concerns the development of Web/Desktop Applications, Web Services or database-related logic adopted by your company. If you are working for a company, other than the two mentioned above, and have various software projects on the role or already in house, then most probably you’ll have to ask if the software vendors you are working with have took into consideration the SQL Injection threats and proved their solutions against them. On contrary, if you have nothing to do with IT at all, it might still be a good idea to ask your IT department if they have anything in place related to SQL Injection – Security Policy, security best practices, etc.

Definition

  Wikipedia defines SQL Injection as “a code injection technique that exploits a security vulnerability occurring in the database layer of an application” [3], the code injection being defined as “the exploitation of a computer bug that is caused by processing invalid data” [4]. For a programmer the definition is acceptable, though for other type of professionals it might not be so clear what’s about, especially when they are not familiar with IT terminology. I find more clear the definition provided by J. Clarke et. al, who in his book SQL Injection Attacks and Defense, defines SQL Injection as 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” [2]. I will slightly modify the last definition and say that the SQL injection is a security vulnerability residing in the possibility to alter the intended behavior of the SQL Queries passed to the database.

Some Background

    At the beginning of our century, with the increase importance of Web Applications whose availability over WAN/Internet (networks) brought new security issues, the SQL Injection became a really hot topic given the damages such techniques could do to an application, with just a few tricks the “hacker” having the possibility to enter in the application and even in the machine hosting the database used, entering thus in the possession of sensitive information, and above all having the possibility of damaging the database. J. Clarke et. al remarks that the first connection between web applications and SQL injection is widely accredited to Rain Forest Puppy, who in an article titled “NT Web Technology Vulnerabilities” (see “ODBC and MS SQL server 6.5” section) written in 1998 for Phrack, an e-zine written by and for hackers [2], was describing the behavior specific to SQL Injection in relation to MS SQL Server 6.5. 

 
    I remember when my boss break us the news that we have to protect urgently our applications against SQL Injection, having to redesign some of the database objects and components in order to protect our applications against such techniques. I was then in my first or second year of professional experience, so the topic was new and quite intriguing not only for myself but also for my colleagues, some of them having a few more years of professional programming experience that I did and, I hope I’m not mistaking, none (or few) of them actually have heard about it. It was interesting to check how simple techniques could do so much damage. At those times there were few articles on SQL Injection and specific countermeasure techniques, not to mention best practices, so we were kind of groping in the dark in finding a countermeasure to the problem.

State of Art

    Since then, the number of search engines hits on the topic is quite impressive, many professionals approaching the problem in their way, Vendors started to design their solutions and make aware programmers on best practices in order to minimize this type of security threat, books were written on this topic, the awareness increased between developers and other type of IT professionals. Even if considerable effort has been made into this direction, and the topic appears often on the blogs, there are still many web sites not designed to address SQL Injection concerns. In 2007, The WhiteHat Security, placed SQL Injection on 5th position in top of vulnerabilities, estimating that 1 out of 5 web sites is vulnerable to SQL Injection [1]. In 8th Web Security Report based on 2009 data provided by WhiteHat Security[5], and as it seems also in 9th report [6], SQL Injection remains on the same position, what’s interesting to remark is the split per scripting technology provided in [6]: 

 

   In Web Hacking Incident Database maintained by Web Application Security Consortium, SQL Injection is considered as 17.97 % out of the total 512 reported top attack methods. Even if the number of reported attacks is insignificant in report to the number of sites available on the web, the percentage of cases seems to be in agreement with the number provided in WhiteHat Security reports.

Resources

   If the topic made you curious, you could find out more with just a simple search on the Web. There are many professionals who wrote on this topic, however it’s a good idea to start directly with the resources provided by the RDBMS vendors, for example Microsoft through its Security Research & Defense blog, in SQL Injection Attacks post has an interesting list of resources on this topic. A nice document on ‘How to write SQL injection proof PL/SQL’ comes from Oracle, an interesting presentation on ‘SQL Injection Myths and Fallacies’ was made at MySQL Conference & Expo, etc.

References:
[1] WhiteHat Security. [2007]. Website Security Statistics Report. [Online] Available from: http://www.whitehatsec.com/home/assets/WPStatsreport_100107.pdf (Accessed: 15 August 2010)
[2] J.Clarke et. al (2009). SQL Injection Attacks and Defense. Elsevier. ISBN: 978-1-59749-424-3
[3] Wikipedia. (2010). SQL Injection. [Online] Available from: http://en.wikipedia.org/wiki/Sql_injection (Accessed: 15 August 2010)
[4] Wikipedia. (2010). Code Injection. [Online] Available from: http://en.wikipedia.org/wiki/Code_injection (Accessed: 15 August 2010)
[5] WhiteHat Security. [2009]. Website Security Statistic Report, 8th Ed. [Online] Available from: http://www.whitehatsec.com/home/assets/WPstats_fall09_8th.pdf (Accessed: 15 August 2010)
[6] WhiteHat Security. [2010]. Website Security Statistic Report, 9th Ed. [Online] Available from: http://www.slideshare.net/jeremiahgrossman/whitehat-security-9th-website-security-statistics-report-3995771 (Accessed: 15 August 2010)

DBMS: SQL Injection (Definitions)

"SQL injection is a technique that exploits security vulnerabilities in the application layer and middle tier, allowing users to execute arbitrary SQL statements on a server." (Michael Coles, "Pro T-SQL 2008 Programmer's Guide", 2008)

"A security vulnerability that occurs in the persistence/database layer of a Web application. This vulnerability is derived from the incorrect escaping of variables embedded in SQL statements. It is in fact an instance of a more general class of vulnerabilities based on poor input validation and bad design that can occur whenever one programming or scripting language is embedded inside another." (Mark S Merkow & Lakshmikanth Raghavan, "Secure and Resilient Software Development", 2010)

"A form of Web hacking whereby SQL statements are specified in a Web form to expose data to the attacker." (Craig S Mullins, "Database Administration", 2012)

"SQL injection is a technique that exploits security vulnerabilities in the application layer and middle tier, allowing users to execute arbitrary SQL statements on a server." (Jay Natarajan et al, "Pro T-SQL 2012 Programmer's Guide 3rd Ed", 2012)

"The process of manipulating a web application to run SQL commands sent by an attacker." (Mark Rhodes-Ousley, "Information Security: The Complete Reference, Second Edition, 2nd Ed.", 2013)

"A technique that exploits security vulnerabilities in the application layer and middle tier, allowing users to execute arbitrary SQL statements on a server." (Miguel Cebollero et al, "Pro T-SQL Programmer’s Guide 4th Ed", 2015)