SQL Injection - Basics : HOw To
websites. This article is also beneficial for hackers too as it will refresh their concepts that what really we have to do and look into website URL if we want to hack website or its database using SQL injection. So Guys read on very basic SQL injection tutorial..
What is SQL Injection?
Basically SQL Injections or simply called Structured Query Language Injection is a technique that exploits the loop hole in the database layer of the application. This happens when user mistakenly or purposely(hackers) enters the special escape characters into the username password authentication form or in URL of the website. Its basically the coding standard loop hole. Most website owners doesn't have proper knowledge of secure coding standards and that results into the vulnerable websites. For better understanding, suppose you opened a website and went to his Sign in or log in page. Now in username field you have entered something say LOKESH and in the password box you pass some escape characters like ',",1=1, etc... Now if the website owner hasn't handled null character strings or escape characters then user will surely get something else that owner never want their users to view.. This is basically called Blind SQL.
Requirements for SQL Injection:
1. You need a web browser to open URL and viewing source codes.
2. Need a good editor like Notepad ++ to view the source codes in colored format so that you can easily distinguish between the things.
3. And very basic knowledge of some SQL queries like SELECT, INSERT, UPDATE, DELETE etc..
What you should look into website to detect is it vulnerable to SQL injection attack or not?
First of all you can hack those websites using SQL injection hacks that allows some input fields from which can provide input to website like log in page, search page, feedback page etc. Nowadays, HTML pages use POST command to send parameters to another ASP/ASPX page. Therefore, you may not see the parameters in the URL. However, you can check the source code of the HTML, and look for "FORM" tag in the HTML code. You may find something like this in some HTML codes:
< F O R M action=login. aspx method=post>
< i n p u t type=hidden name=user v a l u e=xyz>
< / F O R M>
< i n p u t type=hidden name=user v a l u e=xyz>
< / F O R M>
Everything between the < f o r m > and < / f o r m > parameters (remove spaces in words) contains the crucial information and can help us to determine things in more detailed way.
There is alternate method for finding vulnerable website, the websites which have extension ASP, ASPX, JSP, CGI or PHP try to look for the URL's in which parameters are passed. Example is shown below:
Now how to detect that this URL is vulnerable or not:
Start with single quote trick, take sample parameter as hi'or1=1--. Now in the above URL id is the parameter and 10 is its value. So when we pass hi'or1=1-- as parameter the URL will look like this:
You can also do this with hidden field, for that you need to save thewebpage and had to made changes to URL and parameters field and modify it accordingly. For example:
< F O R M action=http://example.com/login. asp method=p o s t >
< i n p u t type=hidden name=abc value="hi' or 1=1--">
< / F O R M >
< i n p u t type=hidden name=abc value="hi' or 1=1--">
< / F O R M >
If your luck is favoring you, you will get the login into the website without any username or password.
But why ' or 1=1-- ?
Take an asp page that will link you to another page with the following URL:
Take an asp page that will link you to another page with the following URL:
In this URL 'category' is the variable name and 'sports' is it's value.
Here this request fires following query on the database in background.
Where 'TABLE-NAME' is the name of table which is already present in some database.
So, this query returns all the possible entries from table 'search' which comes under the category 'sports'.
Now, assume that we change the URL into something like this:
So, this query returns all the possible entries from table 'search' which comes under the category 'sports'.
Now, assume that we change the URL into something like this:
Now, our variable 'category' equals to "sports' or 1=1-- ", which fires SQL query on database something like:
SELECT * FROM search WHERE category='sports' or 1=1--'
SELECT * FROM search WHERE category='sports' or 1=1--'
The query should now select everything from the 'search' table regardless if category is equal to 'sports' or not.
A double dash "--" tell MS SQL server to ignore the rest of the query, which will get rid of the last hanging single quote (').
Sometimes, it may be possible to replace double dash with single hash "#".
However, if it is not an SQL server, or you simply cannot ignore the rest of the query, you also may try
A double dash "--" tell MS SQL server to ignore the rest of the query, which will get rid of the last hanging single quote (').
Sometimes, it may be possible to replace double dash with single hash "#".
However, if it is not an SQL server, or you simply cannot ignore the rest of the query, you also may try
' or 'a'='a
It should return the same result.
Depending on the actual SQL query, you may have to try some of these possibilities:
' or 1=1--
" or 1=1--
or 1=1--
' or 'a'='a
" or "a"="a
') or ('a'='a
'or''='
How to protect you own websites from SQL injection?
Filter out character like ' " - / \ ; NULL, etc. in all strings from:
* Input from users
* Parameters from URL
* Values from cookie
That's all
Enjoy..!!
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