SQL Injection Attacks and Defense - 2009

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Code-Level Defenses • Chapter 8 375 Frequently Asked Questions Q: Why can’t I use parameterized statements to supply table or column names? A: You can’t supply SQL identifiers in a parameterized statement, as these are compiled at the database and then filled in with the supplied data. This requires the SQL identifiers to be present at compile time, before the data is supplied. Q: Why can’t I have a parameterized ORDER BY clause? A: This is for the same reason as for the previous question, as an ORDER BY contains an SQL identifier, namely the column to order by. Q: How do I use parameterized statements in X technology with Y database? A: The majority of modern programming languages and databases support parameterized statements. Try looking at the documentation of the database access API you are using. Remember that these are sometimes referred to as prepared statements. Q: How do I parameterize a stored procedure call? A: In most programming languages, this is very similar to or the same as using a parameterized statement. Try looking at the documentation of the database access API you are using. These may be referred to as callable statements. Q: Where can I get a good blacklist for validating X? A: Unfortunately, what you would need to put in the blacklist will be specific to the context of your application. Also, you shouldn’t use blacklists, if possible, because you cannot blacklist every potential attack or malicious input. If you must use blacklists, make sure you use output encoding as well, or that you are using blacklist input validation as only one of your validation approaches. Q: So, if I use whitelist input validation, am I safe? A: No. It depends on what you’re allowing through. For example, you may allow single quotes to be input, which will create issues if that input is included in dynamic SQL. Q: Where are good places to use whitelist input validation? Blacklist input validation? A: You should use whitelist input validation in the application at the point the input is accepted, allowing you to apply context-sensitive validation at that point. A good place to have blacklist validation is as an additional control at a Web application firewall or similar to enable you to detect obvious SQL injection hacking attempts.
376 Chapter 8 • Code-Level Defenses Q: So, I need to encode input to the database and from it as well? Why? A: If you’re using dynamic SQL anywhere, you need to ensure that the content you are submitting to the database will not cause an SQL injection issue. This doesn’t mean that malicious content has been rendered safe, though. It could be dangerous when queried from the database and used in dynamic SQL elsewhere. Q: At what point should I encode? A: You should encode close to where you use the information. Therefore, you should encode when submitting information to the database before it goes to the database. You should encode information that comes from the database as close to where it is used as possible; for example, before being presented to the user (encode for cross-site scripting), or before it is used in dynamic SQL (encode for SQL injection). Q: How do I perform canonicalization/normalization on input I’ve received in technology X? A: Refer to your documentation of the framework in which you’re developing for canonicalization and normalization support. Alternatively, you could consider using an external framework such as icu for normalization or iconv to convert the input to ASCII if no other support is available. Q: Why is Unicode so complex with canonicalization? A: Unicode allows a character to be represented in a multiple-byte form. Because of the way Unicode is generated, it is possible for there to be multiple representations of the same character. It is also possible in cases where an out-of-date or badly implemented Unicode interpreter is used, that additional invalid presentations of a character may also work. Q: I can use dynamic SQL in a stored procedure, can’t I? A: Yes. But be aware that you can have SQL injection in stored procedures as well. If you have user-controllable information being included in a dynamic SQL query in a stored procedure, you will be vulnerable. Q: I use Hibernate, so I’m safe from SQL injection, right? A: Wrong. Hibernate does encourage secure database access behavior, but it is still possible to create SQL injectable code in Hibernate, especially where you’re using native queries. Avoid dynamic SQL, and make sure you’re using parameterized statements with bound variables.
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Justin Clarke Lead Author and Techn
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Lead Author and Technical Editor Ju
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exploiting, and correcting software
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Dafydd Stuttard is the author of th
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Contents Chapter 1 What Is SQL Inje
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Contents xi LAPSE. ................
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Contents xiii Generic MySQL Binary
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Contents xv Chapter 8 Code-Level De
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Contents xvii Increase the Verbosit
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Contents xix Ingres Cheat Sheet....
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Chapter 1 What Is SQL Injection? So
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What Is SQL Injection? • Chapter
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execute the query against the datab
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Incorrectly Handled Query Assembly
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} } reader = cmd.ExecuteReader(); r
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Chapter 2 Testing for SQL Injection
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Testing for SQL Injection • Chapt
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SELECT * FROM products WHERE idprod
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Figure 2.15 Exploitation Terminatin
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Time Delays Testing for SQL Injecti
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Summary Testing for SQL Injection
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Chapter 3 Reviewing Code for SQL In
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Reviewing Code for SQL Injection
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mssql_bind() − adds a parameter t
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OdbcCommand() − used to construct
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Reviewing PL/SQL and T-SQL Code Rev
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■■ ■■ ■■ ■■ URL: ht
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■■ ■■ Platform: Windows Pri
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Summary Reviewing Code for SQL Inje
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Frequently Asked Questions Reviewin
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Chapter 4 Exploiting SQL Injection
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Exploiting SQL Injection • Chapte
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Approach 3: Content-based Exploitin
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Error Messages in Oracle Exploiting
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MySQL Exploiting SQL Injection •
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Such a query will return output sim
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SELECT name,spare4 FROM sys.user$ w
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[+] Bruteforcing the sa password. T
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select user_name,web_password_raw f
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HTTP/DNS Exploiting SQL Injection
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Summary Exploiting SQL Injection
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Escalating Privileges Exploiting SQ
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Chapter 5 Blind SQL Injection Explo
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Blind SQL Injection Exploitation
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Common Blind SQL Injection Scenario
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1. Is the byte greater than 127? No
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Using Time-Based Techniques Blind S
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SELECT * FROM unknowntable UNION SE
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Figure 5.13 Extracting Database Log
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Summary Blind SQL Injection Exploit
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Chapter 6 Exploiting the Operating
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Exploiting the Operating System •
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[operating systems] multi(0)disk(0)
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Figure 6.13 Enabling CLR Integratio
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Oracle Exploiting the Operating Sys
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) c / ) ) ), bfilename('GETPWDIR',
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As expected, this creates sp.txt fi
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2 443 [+] Calling msfpayload3 to c
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DBMS_ADVISOR is probably the shorte
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EXECUTE IMMEDIATE q'!drop directory
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Microsoft SQL Server Exploiting the
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Figure 6.22 Creating an UNSAFE Bina
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Executing Operating System Commands
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Endnotes Exploiting the Operating S
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Chapter 7 Advanced Topics Solutions
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Using Case Variation Advanced Topic
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4. The application URL decodes the
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Advanced Topics • Chapter 7 323 D
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References • Chapter 10 425 Table
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Blind SQL Injection Functions: Micr
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References • Chapter 10 429 the S
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Microsoft SQL Server 2005 Hashes Re
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References • Chapter 10 435 If MA
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TYPE oracle_loader DEFAULT DIRECTOR
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References • Chapter 10 441 When
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Table 10.20 Continued. Troubleshoot
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Enumerating Database Configuration
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Local File Access References • Ch
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References • Chapter 10 451 Infor
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■■ ■■ ■■ ■■ Referen
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Troubleshooting SQL Injection Attac
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A abstract syntax tree (AST), 125 a
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Index 461 confirming and terminatin
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Index 463 errors application error,
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Index 465 intercepting filters appl
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Index 467 APEX, 196-197 Oracle inte
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Index 469 mysql_query( ) function,
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Index 471 blind SQL injection funct
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Index 473 transformation functions,
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SQL Injection Attacks and Defense - 2009

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