Security Testing – Injection

Injection is a class of security vulnerabilities where untrusted data is sent to an interpreter as part of a command or query. This can allow attackers to manipulate the input data in such a way that they can execute unintended commands, access sensitive data, or even compromise the entire system.

The most common forms of injection attacks include SQL Injection, Command Injection, XML Injection, and LDAP Injection, among others.

---

Types of Injection Attacks:

1. SQL Injection (SQLi):
   • Occurs when an attacker inserts or manipulates malicious SQL queries via input fields (e.g., login forms or search boxes).
   • Effect: Allows attackers to view, modify, or delete data from the database.
   Example:
   • Vulnerable Query:SELECT * FROM users WHERE username = 'input' AND password = 'input';
   • Attack: If the user enters admin' OR 1=1-- as the username, the query becomes:SELECT * FROM users WHERE username = 'admin' OR 1=1--' AND password = 'password'; This causes the query to always return true, bypassing authentication.
2. Command Injection:
   • Happens when attackers inject malicious commands into the system, often via input fields that execute system-level commands (e.g., through shell commands).
   • Effect: Allows attackers to execute arbitrary commands on the server or system.
   Example:
   • Vulnerable Command Execution:bashCopy codesystem("ping " . $_GET['ip']);
   • Attack: An attacker can pass 127.0.0.1; rm -rf / as input, causing the system to execute a harmful command (e.g., deleting files).
3. XML Injection:
   • Occurs when untrusted input is injected into an XML document or request.
   • Effect: Can modify the structure or logic of the XML, allowing unauthorized access or data manipulation.
   Example:
   • Vulnerable XML Handling:xmlCopy code<user> <name>USER_INPUT</name> <password>USER_PASSWORD</password> </user>
   • Attack: An attacker may inject a malicious XML snippet:xmlCopy code<name>evil_user</name><password>evil_password</password><admin>true</admin> This could grant unauthorized access by exploiting the XML structure.
4. LDAP Injection:
   • Occurs when user input is improperly included in LDAP queries, potentially altering the logic of the query.
   • Effect: Allows attackers to bypass authentication or access restricted data.
   Example:
   • Vulnerable LDAP Query:bashCopy codefilter = "(&(username=" + user_input + ")(password=" + password_input + "))";
   • Attack: If the attacker provides the following input:
     • username = "admin"(&(password=*))
     • The query becomes:bashCopy code(&(username=admin)(password=*))
     This query could bypass authentication by matching any password.

---

How to Prevent Injection Attacks:

1. Use Prepared Statements (SQLi):
   • Prepared statements with parameterized queries prevent attackers from injecting malicious SQL commands, as the query structure is predefined.
   Example (in SQL):SELECT * FROM users WHERE username = ? AND password = ?;
2. Input Validation and Sanitization:
   • Always validate and sanitize user inputs to ensure that they conform to expected values and do not contain harmful content.
   • Reject characters like semicolons (;), quotes (' or ") in input fields where they are not expected.
3. Stored Procedures:
   • Use stored procedures for database interaction, as they allow better control over the queries and inputs.
4. Escape Special Characters:
   • In cases where dynamic SQL is necessary, escape special characters like ', ;, and -- to prevent unintended query modifications.
5. Limit System Command Execution (Command Injection):
   • Avoid constructing system-level commands using user input. Use safe APIs to interact with the system instead.
6. Use XML Schema Validation (XML Injection):
   • Validate and parse XML data against a defined schema to prevent attackers from altering the XML structure.
7. Least Privilege:
   • Restrict the privileges of web applications and users interacting with databases or systems to the bare minimum needed to function.

---

Conclusion:

Injection attacks are among the most dangerous and common web vulnerabilities, capable of leading to data breaches, unauthorized access, and full system compromise. Effective mitigation techniques, such as input validation, parameterized queries, and using stored procedures, are essential to defend against these threats. Security testing for injection vulnerabilities involves identifying weak spots where user input is incorporated into queries, commands, or other sensitive operations and ensuring robust defense mechanisms are in place.