SQL Injection Attacks and Defense - 2009

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Chapter 5 Blind SQL Injection Exploitation Solutions in this chapter: ■■ ■■ ■■ ■■ ■■ Finding and Confirming Blind SQL Injection Using Time-Based Techniques Using Response-Based Techniques Using Alternative Channels Automating Blind SQL Injection Exploitation ˛ Summary ˛ Solutions Fast Track ˛ Frequently Asked Questions 219
220 Chapter 5 • Blind SQL Injection Exploitation Introduction So, you’ve found an SQL injection point, but the application gives you only a generic error page. Or perhaps it gives you the page as normal, but there is a small difference in what you get back, visible or not. These are examples of blind SQL injection, where you exploit without any of the useful error messages or feedback that you may be used to, as you saw in Chapter 4. Don’t worry; you can still reliably exploit SQL injection even in these scenarios. You saw a number of classic SQL injection examples in Chapter 4 that relied on verbose error messages to extract data, and this was the first widely used attack technique for data extraction in these vulnerabilities. Before SQL injection was well understood, developers were advised to disable all verbose error messages in the mistaken belief that without error messages the attacker’s data retrieval goal was next to impossible to achieve. In some cases developers would trap errors within the application and display generic error messages, whereas in other cases no errors would be shown to the user. However, attackers soon realized that even though the error-based channel was no longer available, the root cause still remained: Attacker-supplied SQL was executing within a database query. Figuring out new channels was left to the ingenuity of the attackers and a number of channels were discovered and published. Along the way, the term blind SQL injection entered into common usage with slight differences in the definition used by each author. Chris Anley first introduced a blind SQL injection technique in a 2002 paper that demonstrated how disabling verbose error messages could still lead to injection attacks, and he provided several examples. Ofer Maor and Amichai Shulman’s definition required that verbose errors be disabled but that broken SQL syntax would yield a generic error page, and implicitly assumed that the vulnerable statement was a SELECT query whose result set was ultimately displayed to the user. The query’s result (either success or failure) was then used to first derive the vulnerable statement and then to extract data through a UNION SELECT. Kevin Spett’s definition was similar in that verbose error messages were disabled and injection occurred in a SELECT statement; however, instead of relying on generic error pages, his technique altered content within the page through SQL logic manipulations to infer data on a byte-by-byte basis, which was identical to Cameron Hotchkies’ usage. It is clear that blind SQL injection has received significant attention from attackers, and its techniques are a key component in any SQL injection arsenal; however, before delving into the specifics, we need to define blind SQL injection and explore the scenarios in which it commonly occurs. Toward that end, in this chapter we will cover techniques for extracting information from the back-end database through the use inference and alternative channels, including time delays, errors, domain name system (DNS) queries, and HTML responses. This will give you flexible ways to communicate with the database, even in situations where the application is catching exceptions properly and you do not have any feedback from the Web interface that your exploits are working.
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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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Page 208 and 209: [+] Bruteforcing the sa password. T
Page 218 and 219: select user_name,web_password_raw f
Page 224 and 225: HTTP/DNS Exploiting SQL Injection
Page 236 and 237: Summary Exploiting SQL Injection
Page 238 and 239: Escalating Privileges Exploiting SQ
Page 242 and 243: Blind SQL Injection Exploitation
Page 246 and 247: Common Blind SQL Injection Scenario
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Page 256 and 257: Using Time-Based Techniques Blind S
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Page 284 and 285: Figure 5.13 Extracting Database Log
Page 288 and 289: Summary Blind SQL Injection Exploit
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Blind SQL Injection Exploitation
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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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Advanced Topics • Chapter 7 325 I
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Advanced Topics • Chapter 7 327 w
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Advanced Topics • Chapter 7 329 N
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Advanced Topics • Chapter 7 331 m
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Advanced Topics • Chapter 7 333 1
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Using Hybrid Attacks Advanced Topic
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Exploiting Authenticated Vulnerabil
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Advanced Topics • Chapter 7 339
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Chapter 8 Code-Level Defenses Solut
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Code-Level Defenses • Chapter 8 3
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END; Execute immediate 'SELECT coun
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Validating Input in Java Code-Level
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UTL_SMTP.HELO(v_connection,'mailhos
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Summary Code-Level Defenses • Cha
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Chapter 9 Platform-Level Defenses S
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Platform-Level Defenses • Chapter
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Figure 9.3 Whitelist Rule to Patch
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Application Filters Platform-Level
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Use Strong Cryptography to Protect
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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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