SQL Injection Attacks and Defense - 2009

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END; Execute immediate 'SELECT count(*) FROM users where username=:1 and password=:2' into result using username,password; Validating Input Code-Level Defenses • Chapter 8 349 In the previous section, we discussed avoiding the use of dynamic SQL to prevent SQL injection. However, this should not be the only control you put in place to address SQL injection. One of the most powerful controls you can use, if done well, is validation of the input that an application receives. Input validation is the process of testing input received by the application for compliance against a standard defined within the application. It can be as simple as strictly typing a parameter and as complex as using regular expressions or business logic to validate input. There are two different types of input validation approaches: whitelist validation (sometimes referred to as inclusion or positive validation) and blacklist validation (sometimes known as exclusion or negative validation). These two approaches, and examples of validating input in Java, C#, and PHP to prevent SQL injection, are detailed in the following subsections. Tip When performing input validation you should always ensure that the input is in its canonical (simplest) form before making any input validation decisions. This may involve decoding the input into a simpler format, or just rejecting input that isn’t already in canonical format where non-canonical input isn’t expected. We’ll cover canonicalization in a separate solution later in this chapter. Whitelisting Whitelist validation is the practice of only accepting input that is known to be good. This can involve validating compliance with the expected type, length or size, numeric range, or other format standards before accepting the input for further processing. For example, validating that an input value is a credit card number may involve validating that the input value contains only numbers, is between 13 and 16 digits long, and passes the business logic check of correctly passing the Luhn formula (the formula for calculating the validity of a number based on the last “check” digit of the card).
350 Chapter 8 • Code-Level Defenses When using whitelist validation you should consider the following points: ■■ ■■ ■■ ■■ Data type Is the data type correct? If the value is supposed to be numeric, is it numeric? If it is supposed to be a positive number, is it a negative number instead? Data size If the data is a string, is it of the correct length? Is it less than the expected maximum length? If it is a binary blob, is it less than the maximum expected size? If it is numeric, is it of the correct size or accuracy? (For example, if an integer is expected, is the number that is passed too large to be an integer value?) Data range If the data is numeric, is it in the expected numeric range for this type of data? Data content Does the data look like the expected type of data? For example, does it satisfy the expected properties of a ZIP Code if it is supposed to be a ZIP Code? Does it contain only the expected character set for the data type expected? If a name value is submitted, only some punctuation (single quotes and character accents) would normally be expected, and other characters, such as the less than sign (
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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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Platform-Level Defenses • Chapter
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Additional Deployment Consideration
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Chapter 10 References Solutions in
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References • Chapter 10 417 For t
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References • Chapter 10 419 It is
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GROUP BY Statement References • C
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References • Chapter 10 423 you a
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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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