SQL Injection Attacks and Defense - 2009

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Exploiting SQL Injection • Chapter 4 139 On the other hand, if the only vulnerable parameters at your disposal are used to modify some data, most of the techniques outlined in this chapter will be useful for exploiting the vulnerability. However, be extra careful in what you inject and how this might affect the database. If the application you are testing is in production, before performing the actual attack make sure all the data is backed up and that it is possible to perform a full rollback after the security testing of the application has been completed. This is especially true when using an automated tool such as the ones I will introduce at the end of the chapter. Such tools can easily execute hundreds or thousands of queries in a very short time to do their job, all with minimal user interaction. Using such a tool to inject on an UPDATE or a DELETE statement can wreak havoc on a DBMS, so be careful! Understanding Common Exploit Techniques Arriving at this point, you have probably found one or more vulnerable parameters on the Web application you are testing, by either using the techniques for testing the application outlined in Chapter 2, or reviewing the code outlined in Chapter 3. Perhaps a single quote inserted in the first GET parameter that you tried was sufficient to make the application return a database error, or maybe you literally spent days stubbornly going through each parameter trying entire arrays of different and exotic attack vectors. In any case, now is the time to have some real fun with the actual exploitation. It is very useful at this stage to have a local installation of the same database system that sits behind the application you are attacking. Unless you have the Web application source code, SQL injection requires a black-box attack approach, and you will have to craft the queries to inject by observing how your target responds to your requests. Being able to locally test the queries you are going to inject in order to see how the database responds to such queries makes this phase a lot easier. Exploiting an SQL injection vulnerability can mean different things in different situations depending on the conditions in place, such as the privileges of the user performing the queries, the exact DBMS server that sits on the back end, and whether you are more interested in extracting data, modifying data, or running commands on the remote host. However, at this stage what really makes a difference is whether the application presents in the HTML code the output of your SQL queries (even if the DBMS returns only the error message). If you don’t have any kind of SQL output displayed within the application, you will need to perform a blind SQL injection attack, which is more intricate (but a lot more fun). We’ll cover blind SQL injection in Chapter 5. For now, and unless specified otherwise, we will assume that the remote database returns SQL output to some extent, and we will go through a plethora of attack techniques that leverage this fact.
140 Chapter 4 • Exploiting SQL Injection For our examples, we’ll introduce the companion that will be with us throughout most of the examples in this chapter: a vulnerable e-commerce application belonging to our usual victim.com friends. This application has a page that allows a user to browse the different products. The URL is as follows: ■■ http://www.victim.com/products.asp?id=12 When this URL is requested, the application returns a page with the details of the product with an id value of 12 (say, a nice Syngress book on SQL injection), as shown in Figure 4.1. Figure 4.1 The Product Description Page of a Sample E-Commerce Site Let’s say the id parameter is vulnerable to SQL injection. It’s a numeric parameter, and therefore in our examples we will not need to use single quotes to terminate any strings. But the same concepts that we will explore along the way are obviously valid for other types of data. We will also assume that victim.com uses Microsoft SQL Server as its backend database (even though the chapter will also contain several examples for other
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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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Page 110 and 111: Testing for SQL Injection • Chapt
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Exploiting SQL Injection • Chapte
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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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Advanced Topics • Chapter 7 325 I
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Advanced Topics • Chapter 7 329 N
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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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