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SQL Injection Jason Dunn

Learn about SQL injection, its causes, dangers, and how to detect and prevent it. Find out real-life examples, implementation differences, and application hardening techniques.

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SQL Injection Jason Dunn

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  1. SQL InjectionJason Dunn

  2. SQL Overview • Structured Query Language • For use with Databases • Purpose is to retrieve information • Main Statements • Select • Insert • Update • Drop

  3. SQL Statement Format • Select * From [Table] where [ conditions ] • Eg. Select grade From Students where pid=‘1234’ • Selects the grade field value from the Students table from every entry where the corresponding pid = 1234 • Update [Table] where [column name 1 = value 1] set [column name 2 = value 2] • Updates the specified table – all records where a value 1 is found in column 1, it will replace column 2’s value with value 2 • Drop Table [Table] • Deletes the given table

  4. Database Basics • Definitions • Table – Collection of records • Column – Specifies a value which will be present in all records • Value – The contents of a specific column in a specific record • Record – One row in the table • Used for storing/organizing data • Used by most businesses in some degree • Typical applications • customer data, banking data, health data, orders, inventory

  5. Example Table Column Record Field Value

  6. SQL Injection Overview • Causes • Basics • Dangers • Detection • Hardening Applications • Implementation Differences • Demo

  7. Causes • Failure to Sanitize Input • Don’t Trust user input • User can put special characters or statements into fields • SQL supports multiple statements per query • Though some connection drivers don’t

  8. Basics • Add in logic to passed parameter • If you have the statement: • Select * from Students where password=‘$pass’ • And your user submits $pass = 1’ or 1=1 • Your statement becomes • Select * from Students where password=‘1’ or 1=1 • Your statement now always resolves to true and every record is displayed • Disclosure of extra data

  9. Dangers • Authentication Bypass • Someone could see data they aren’t authorized to see • Disclosures • Again, you could see all the information in a database • Modification • Students could modify their grade in the computer system • Deletion • Someone could delete a company’s customer records • Execution • A hacker could force your computer to run any program they want it to

  10. Authentication Bypass • Can bypass authentication by changing the statement to always return true • Use the same or similar options as disclosure • 1’ or 1=1 etc.

  11. Modification • Uses the ability to chain multiple statements in a single request • If you have the statement: • Select * from Students where password=‘$pass’ • And your user submits $pass=1’; Update Students where name=you set grade=100 • If the input is not sanitized you have remotely changed your grade ( or any random value on the server, account balance, passwords, etc)

  12. Deletion • If you have the statement: • Select * from Students where password=‘$pass’ • And your user submits $pass=1’; Delete Table Students • If the input is not sanitized you have remotely deleted all records in the Students table

  13. Execution (Specific to certain implementations) • If you have the statement: • Select * from Students where password=‘$pass’ • And your user submits $pass=1’ ;exec master.dbo.xp_cmdshell [some command] • If the input is not sanitized and the exec command is enabled you can run commands at whatever level the servers permission is • Server often runs at admin privilige level • Use exec to download backdoor • Use exec to execute backdoor

  14. Detection • Automated Tools • Manual Testing • Code Review • Hand testing statements

  15. Automated Tools • HP WebInspect • Rational AppScan • SQL Power Injector • Absinthe • Sqlninja

  16. Hardening Applications • Update software • If you are using PHP5 it automatically tries to escape single quotes • Escape the strings manually • mysql_real_escape_string() or other similar methods • Manually check for compound statements • Do not generate statements from the user input, use prepared statements • Check input against result of prepared statements

  17. Implementation Differences

  18. Real Life Example (Her daughters name is help I am trapped in a drivers license factory)

  19. Demo

  20. Sources • www.w3schools.com • www.freewebmasterhelp.com/tutorials/phpmysql • Carey, Mark. Nessus Network Auditing. Burlington, MA. 2008 • McClure, Stuart. Hacking Exposed: 6. McGraw Hill. Chicago, IL. 2009 • Skoudis, Ed. Counter Hack Reloaded. Prentice Hall. Indianapolis, IN. 2002

  21. Questions ?

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