Learning Web Pentesting With DVWA Part 3: Blind SQL Injection

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:

' or 1=1-- - 

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:

' or 1=1 order by 1-- - 

Again we get a valid response lets increase the number to 2.

' or 1=1 order by 2-- - 

We get a valid response again lets go for 3.

' or 1=1 order by 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-- - 

Since we don't see any output we have to extract data character by character. Here we are trying to guess the first character of the string returned by version() function which in my case is 1. You'll notice the output returns a valid response when we enter the query above in the input field.
Lets examine the query a bit to further understand what we are trying to accomplish. We know 1 is the valid user id and it returns a valid response, we append it to the query. Following 1, we use a single quote to end the check string. After the single quote we start to build our own query with the and conditional statement which states that the answer is true if and only if both conditions are true. Since the user id 1 exists we know the first condition of the statement is true. In the second condition, we extract first character from the version() function using the substring() function and compare it with the value of 1 and then comment out the rest of server query. Since first condition is true, if the second condition is true as well we will get a valid response back otherwise we will get an invalid response. Since my the version of mariadb installed by the docker container starts with a 1 we will get a valid response. Lets see if we will get an invalid response if we compare the first character of the string returned by the version() function to 2 like this:

1' and substring(version(),1,1) = 2-- - 

And we get the invalid response. To determine the second character of the string returned by the version() function, we will write our query like this:
1' and substring(version(),2,2) = 1-- -
We get invalid response. Changing 1 to 2 then 3 and so on we get invalid response back, then we try 0 and we get a valid response back indicating the second character in the string returned by the version() function is 0. Thus we have got so for 10 as the first two characters of the database version. We can try to get the third and fourth characters of the string but as you can guess it will be time consuming. So its time to automate the boring stuff. We can automate this process in two ways. One is to use our awesome programming skills to write a program that will automate this whole thing. Another way is not to reinvent the wheel and try sqlmap. I am going to show you how to use sqlmap but you can try the first method as well, as an exercise.
Lets use sqlmap to get data from the database. Enter 1 in the User ID field and click submit.
Then copy the URL from the URL bar which should look something like this
http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit
Now open a terminal and type this command:

sqlmap --version 

this will print the version of your sqlmap installation otherwise it will give an error indicating the package is not installed on your computer. If its not installed then go ahead and install it.
Now type the following command to get the names of the databases:

sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id 

Here replace the PHPSESSID with your session id which you can get by right clicking on the page and then clicking inspect in your browser (Firefox here). Then click on storage tab and expand cookie to get your PHPSESSID. Also your port for dvwa web app can be different so replace the URL with yours.
The command above uses -u to specify the url to be attacked, --cookie flag specifies the user authentication cookies, and -p is used to specify the parameter of the URL that we are going to attack.
We will now dump the tables of dvwa database using sqlmap like this:

sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id -D dvwa --tables 

After getting the list of tables its time to dump the columns of users table like this:

sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id -D dvwa -T users --columns 

And at last we will dump the passwords column of the users table like this:

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 

Now you can see the password hashes.
As you can see automating this blind sqli using sqlmap made it simple. It would have taken us a lot of time to do this stuff manually. That's why in pentests both manual and automated testing is necessary. But its not a good idea to rely on just one of the two rather we should leverage power of both testing types to both understand and exploit the vulnerability.
By the way we could have used something like this to dump all databases and tables using this sqlmap command:

sqlmap -u "http://localhost:9000/vulnerabilities/sqli_blind/?id=1&Submit=Submit" --cookie="security=low; PHPSESSID=aks68qncbmtnd59q3ue7bmam30" -p id --dump-all 

But obviously it is time and resource consuming so we only extracted what was interested to us rather than dumping all the stuff.
Also we could have used sqlmap in the simple sql injection that we did in the previous article. As an exercise redo the SQL Injection challenge using sqlmap.

References:

1. Blind SQL Injection: https://owasp.org/www-community/attacks/Blind_SQL_Injection
2. sqlmap: http://sqlmap.org/
3. MySQL SUBSTRING() Function: https://www.w3schools.com/sql/func_mysql_substring.asp

Related posts

1. Hack And Tools
2. Hack Tools For Games
3. Hacking Tools Hardware
4. Hackers Toolbox
5. Top Pentest Tools
6. How To Make Hacking Tools
7. Pentest Tools Tcp Port Scanner
8. Hack Tools Download
9. Hacker Tools Free Download
10. Hacker Tool Kit
11. Android Hack Tools Github
12. Hacking Tools And Software
13. Hacker Tools Github
14. Android Hack Tools Github
15. Hacker Tools Mac
16. Hacking Tools For Pc
17. New Hacker Tools
18. Hacker Search Tools
19. Hack Tools Online
20. Hack App
21. Hacking Tools Kit
22. Hacker Hardware Tools
23. How To Install Pentest Tools In Ubuntu
24. Pentest Tools Open Source
25. Hacker Tools Apk Download
26. Hack Website Online Tool
27. Pentest Tools List
28. Hack Tools For Pc
29. Hacking Tools Free Download
30. Hacker Tools
31. Hacker Tools Windows
32. Pentest Tools Kali Linux
33. Hacking Tools Download
34. Pentest Tools Url Fuzzer
35. Install Pentest Tools Ubuntu
36. Hacker Tools 2019
37. Computer Hacker
38. Pentest Tools Windows
39. Free Pentest Tools For Windows
40. Hacker Tools For Mac
41. Pentest Tools Url Fuzzer
42. Pentest Tools Free
43. New Hack Tools
44. Pentest Tools Open Source
45. Best Hacking Tools 2019
46. Hack Tools Mac
47. Install Pentest Tools Ubuntu
48. Pentest Automation Tools
49. Best Hacking Tools 2019
50. Hack Tools Mac
51. Hacker Tool Kit
52. What Are Hacking Tools
53. New Hacker Tools
54. Tools For Hacker
55. Pentest Tools
56. Hacking Tools Kit
57. Hacking Tools Mac
58. Hacking Tools 2019
59. Computer Hacker
60. Hack Tools For Pc
61. Pentest Tools Review
62. Hacking Tools Kit
63. Hack Tools For Games
64. Hacking Tools For Games
65. Hacker Tools Free
66. Hacker
67. Hacker Tools For Ios
68. Pentest Tools Tcp Port Scanner
69. Pentest Tools Port Scanner
70. Pentest Box Tools Download
71. Pentest Tools Linux
72. Pentest Tools Free
73. Nsa Hack Tools Download
74. Pentest Tools Open Source
75. Hack Website Online Tool
76. Beginner Hacker Tools
77. Hacking Tools For Beginners
78. Hack Tools Github
79. Hack Rom Tools
80. Pentest Tools
81. Hacker Tools Windows
82. Pentest Tools Kali Linux
83. New Hack Tools
84. Blackhat Hacker Tools
85. Hacker Tools Apk
86. Ethical Hacker Tools
87. Android Hack Tools Github
88. Hack Tools Download
89. Hacking Tools Pc
90. Hacker Security Tools
91. World No 1 Hacker Software
92. Beginner Hacker Tools
93. Hacking Tools 2019
94. World No 1 Hacker Software
95. Hacking Tools Usb
96. Hacking Tools