Overview from OWASP
What are injection-based vulnerabilities?
Almost any source of data can be an injection vector, environment variables, parameters, external and internal web services, and all types of users. Injection flaws occur when an attacker can send hostile data to an interpreter. Injection flaws are very prevalent, particularly in legacy code. Injection vulnerabilities are often found in SQL, LDAP, XPath, or NoSQL queries, OS commands, XML parsers, SMTP headers, expression languages, and ORM queries. Injection flaws are easy to discover when examining code. Scanners and fuzzers can help attackers find injection flaws. Injection can result in data loss, corruption, or disclosure to unauthorized parties, loss of accountability, or denial of access. Injection can sometimes lead to complete host takeover. The business impact depends on the needs of the application and data.
What makes an application vulnerable to injection?
- User-supplied data is not validated, filtered, or sanitized by the application.
- Dynamic queries or non-parameterized calls without context-aware escaping are used directly in the interpreter.
- Hostile data is used within object-relational mapping (ORM) search parameters to extract additional, sensitive records.
- Hostile data is directly used or concatenated, such that the SQL or command contains both structure and hostile data in dynamic queries, commands, or stored procedures.
- Some of the more common injections are SQL, NoSQL, OS command, Object Relational Mapping (ORM), LDAP, and Expression Language (EL) or Object Graph Navigation Library (OGNL) injection. The concept is identical among all interpreters. Source code review is the best method of detecting if applications are vulnerable to injections, closely followed by thorough automated testing of all parameters, headers, URL, cookies, JSON, SOAP, and XML data inputs. Organizations can include static source (SAST) and dynamic application test (DAST) tools into the CI/CD pipeline to identify newly introduced injection flaws prior to production deployment.
How do you prevent injection in web apps?
- The preferred option is to use a safe API, which avoids the use of the interpreter entirely or provides a parameterized interface, or migrate to use Object Relational Mapping Tools (ORMs). Note: Even when parameterized, stored procedures can still introduce SQL injection if PL/SQL or T-SQL concatenates queries and data, or executes hostile data with EXECUTE IMMEDIATE or exec().
- Use positive or “whitelist” server-side input validation. This is not a complete defense as many applications require special characters, such as text areas or APIs for mobile applications.
- For any residual dynamic queries, escape special characters using the specific escape syntax for that interpreter. Note: SQL structure such as table names, column names, and so on cannot be escaped, and thus user-supplied structure names are dangerous. This is a common issue in report-writing software.
- Use LIMIT and other SQL controls within queries to prevent mass disclosure of records in case of SQL injection.
In this section, we are going to be going over the Portswigger web academy course as well as do a few of the labs. This will help us understand SQL as well as form some methods for testing SQL. You can find the course here.
What is SQLi?
An SQL injection vulnerability allows an attacker to interfere with queries that an application makes to a database.
What is the impact of an SQLi?
A successful SQL injection attack can result in unauthorized access to sensitive data, such as passwords, credit card details, or personal user information.
Common types of SQLi:
- Retrieving hidden data
- Subverting application logic
- UNION attacks
- Examining the database
- Blind SQL injection
I will be doing an individual lab on each of these, with screenshots and separated submitted payloads at the bottom of this document.
How to detect SQL injection vulnerabilities
Submitting the single quote character ‘ and looking for errors or other anomalies.
- Submitting some SQL-specific syntax that evaluates to the base (original) value of the entry point, and to a different value, and looking for systematic differences in the resulting application responses.
- Submitting Boolean conditions such as OR 1=1 and OR 1=2, and looking for differences in the application’s responses.
- Submitting payloads designed to trigger time delays when executed within an SQL query, and looking for differences in the time taken to respond.
- Submitting OAST payloads designed to trigger an out-of-band network interaction when executed within an SQL query, and monitoring for any resulting interactions.
OS command injection
What is OS command injection?
web security vulnerability that allows an attacker to execute arbitrary operating system (OS) commands on the server that is running an application, and typically fully compromise the application and all its data.
What is the impact of OS command injection?
Very often, an attacker can leverage an OS command injection vulnerability to compromise other parts of the hosting infrastructure, exploiting trust relationships to pivot the attack to other systems within the organization.
Detecting OS command injection?
I was not able to find anything useful on detecting os command injection besides just trying commands within a url.
|Purpose of command||Linux||Windows|
|Name of current user||whoami||whoami|
|Operating system||uname -a||ver|
|Network configuration||ifconfig||ipconfig /all|
|Network connections||netstat -an||netstat -an|
|Running processes||ps -ef||tasklist|
Honestly the best example I can find is in the Executing arbitrary commands from the following reference.
How do you inject OS commands?
A number of characters function as command separators, allowing commands to be chained together. The following command separators work on both Windows and Unix-based systems:
The following command separators work only on Unix-based systems:
- Newline (0x0a or \n)
On Unix-based systems, you can also use backticks or the dollar character to perform inline execution of an injected command within the original command:
- ` injected command `
- $( injected command )