SQL Injection in Classic ASP and Possible Solutions
page 1 of 8
Published: 12 Aug 2008
Abstract
Nowadays, SQL injection is a big threat for websites. It is a technique by which hackers can execute dangerous SQL commands by taking advantage of un-sanitized input opportunities in web application. While there is a good amount of best practices to prevent SQL injection in ASP.NET, ASP has very little information. In this article, Ehsanul examines a quicker and easier way to sanitize input parameters as well as the design plan for a new website to protect from SQL Injection. After a brief introduction, he demonstrates the technique with the help of relevant source code and screenshots. Towards the end of the article, he provides some tips to avoid database related errors and a list of useful reference articles.
by Ehsanul Haque
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Introduction

Several communities have already started a few workarounds on this issue. HP Web Security Research Group published a tool named HP Scrawlr, to find out SQL Injection vulnerabilities in websites. Also, Microsoft recently released source code analyzer for SQL Injection. But sanitizing all the input fields is not an easy task for a large website.

SQL (structured query language) is a very powerful gun for hackers. We know there are several built-in processes in ASP.NET to protect it from SQL Injection and cross site scripting like ValidateRequest, "EnableEventValidation," etc. in page element. They inspect in every request variable for script to prevent attack in application. These features can be set from web.config which will work for every page centrally or can be set in individual pages from page element tag. We have to build similar functionality in classic ASP, so we will do it similarly to the ways ASP.NET protects the application from SQL Injection. Normally, hackers target the "information collection form" like the registration form, subscription form, login form, etc. Searching this type of form is not a hard task since hackers used a very smart crawler program. In the rest of the article, we will build a ValidateRequest system which can inspect all request variables centrally application-wise as well as page-wise like the built-in system in ASP.NET.


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User Comments

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Date: 2012-11-13 6:20:17 AM
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Title: this is good!   
Name: joven
Date: 2012-05-19 11:14:33 AM
Comment:
this is good post of article.. thanks for this upload :)
Title: RE:sample code missing   
Name: Ehsanul Haque
Date: 2012-01-23 12:04:29 PM
Comment:
Hey Bob,
Thanks for notifying me about the missing URL for the sample code. I am in rush right now, but I will try to fix it as soon as possible.
Title: sample code missing   
Name: Bob
Date: 2012-01-23 9:14:23 AM
Comment:
Sadly, the sample code ZIP file is 404 not found. :( I believe I can follow along with the article, and extract the appropriate code to implement, but sample code is almost always more straight forward for fully understanding a concept, since it is usually a full solution vs a tutorial. Thanks for a great article, though!
Title: Possible solution for SQL Injection   
Name: Rey Calanta-ol
Date: 2011-04-01 10:06:12 AM
Comment:
1. Optimize your inputs, you may use replace function to replace all suspicious symbols in the inputs.
2. Use parameterized query.
Title: Great article :)   
Name: Benedict Basa
Date: 2010-11-07 11:51:15 PM
Comment:
Exactly what i needed :)
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Name: pickatutorial
Date: 2010-10-05 11:27:44 AM
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Title: nice :)   
Name: MJ
Date: 2010-06-29 5:37:37 PM
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Title: Replace wrong words   
Name: Eric Coumans
Date: 2009-12-21 10:37:23 AM
Comment:
Hi there,

small question: is it also possible instead of going to the error page, replace the value in the scanned form input?

so when somebody fills in "copenhagen" the function (mentioned above) will change ("open") this into: "c*hagen"...

thanks for the help!
Title: RE: Function always return true   
Name: Ehsanul Haque
Date: 2009-12-09 5:01:13 AM
Comment:
Hello Mr. Javed,
I don't think the function is always returning true. After configuring the sample, open the test.asp and type username "cursor p1" and it will be blocked as the "cursor" is the blacklisted keyword. Similarly, if you write "abc" it will not block as it is not in the blacklist. Also see the relavant code below:

For Each s in BlackList
If(IsExceptionList(s,varType)=False) then
If ( InStr (lstr, s) <> 0 ) Then
CheckStringForSQL = true
Exit Function
End If
End If
Next

Where "lstr" is the string to check and "s" is the blacklisted keyword.

However, please check that the sample is configured correctly. Please let me know if I can help you anyway.

Thanks,
Ehsan
Title: Function always return true   
Name: Javed Iqbal
Date: 2009-12-09 2:01:23 AM
Comment:
\
Title: RE: 谢谢。   
Name: Ehsanul Haque
Date: 2009-12-05 6:40:15 AM
Comment:
Hi,
I don't know Chinese but I think you are looking for code sample. If it is true then please see the entire article here http://aspalliance.com/1703_SQL_Injection_in_Classic_ASP_and_Possible_Solutions.all

Also you can get the sample project by clicking on the Downloads link at the top or browse here http://aspalliance.com/1703_SQL_Injection_in_Classic_ASP_and_Possible_Solutions.all#Page6

Thanks,
Ehsan
Title: Thank you   
Name: Stefan
Date: 2009-11-24 11:22:30 AM
Comment:
Thank you very much. I had some SQL injection problems and I implemented this, tested and it seems to hold up thus far.

Now I have to teach myself stored procedures along with some .net stuff. Thanks again.
Title: :)   
Name: RJ
Date: 2009-01-13 2:04:18 AM
Comment:
good article. it really helps






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