In the first case, the attacker falsifies log file entries by inserting an end of a line and an extra line. This can be used to hide other attacks or to confuse system administrators. It also uses it to signify where headers end and the website content begins.
If the attacker inserts a single CRLF, they can add a new header. If it is, for example, a Location header, the attacker can redirect the user to a different website.
Criminals may use this technique for phishing or defacing. This technique is often called HTTP header injection. The injected content can contain JavaScript code. It can also be formulated so that the actual website content coming from the web server is ignored by the web browser. The impact of CRLF injections may seem to be limited. However, attackers can effectively use CRLF injections to escalate to much more serious attacks that exploit other web application vulnerabilities.
This is called log injection. In the most benign case, an attacker may be able to insert false entries into the log file by providing the application with input that includes appropriate characters. If the log file is processed automatically, the attacker can render the file unusable by corrupting the format of the file or injecting unexpected characters. Going further, an attacker can cause the application to display all the products in any category, including categories that they don't know about:.
The modified query will return all items where either the category is Gifts, or 1 is equal to 1. Consider an application that lets users log in with a username and password. If a user submits the username wiener and the password bluecheese , the application checks the credentials by performing the following SQL query:.
If the query returns the details of a user, then the login is successful. Otherwise, it is rejected. Here, an attacker can log in as any user without a password simply by using the SQL comment sequence -- to remove the password check from the WHERE clause of the query. For example, submitting the username administrator'-- and a blank password results in the following query:.
This query returns the user whose username is administrator and successfully logs the attacker in as that user. In cases where the results of an SQL query are returned within the application's responses, an attacker can leverage an SQL injection vulnerability to retrieve data from other tables within the database. For example, if an application executes the following query containing the user input "Gifts":.
This will cause the application to return all usernames and passwords along with the names and descriptions of products. Following initial identification of an SQL injection vulnerability, it is generally useful to obtain some information about the database itself. This information can often pave the way for further exploitation. You can query the version details for the database. The way that this is done depends on the database type, so you can infer the database type from whichever technique works.
For example, on Oracle you can execute:. You can also determine what database tables exist, and which columns they contain. Determine Application's Log File Format: The first step is exploratory meaning the attacker observes the system. The attacker looks for action and data that are likely to be logged. The attacker may be familiar with the log format of the system.
Manipulate Log Files: The attacker alters the log contents either directly through manipulation or forging or indirectly through injection of specially crafted input that the target software will write to the logs. This type of attack typically follows another attack and is used to try to cover the traces of the previous attack.
For example:. Different applications may require different encodings of the carriage return and line feed characters. For example, a log file entry could contain. The script itself will be invisible to anybody viewing the logs in a web browser unless they view the source for the page. Attack Pattern ID: Presentation Filter:. This attack targets the log files of the target host. The attacker injects, manipulates or forges malicious log entries in the log file, allowing them to mislead a log audit, cover traces of attack, or perform other malicious actions.
The target host is not properly controlling log access. As a result tainted data is resulting in the log files leading to a failure in accountability, non-repudiation and incident forensics capability. Likelihood Of Attack.
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