What Is An SQL Injection? [MakeUseOf Explains]
Today, we continue our journey into the world of SQL and relational database One to One Relationships; One to Many and Many to One. But for anyone running a database, the SQL injection is one of the most storing data as memory and showing the various relationships between points of data. SQL injection is an attack technique that exploits a security vulnerability Example 1: By inputing malicious code into user input fields.
For example, an attacker may give request for the following URL: For example, consider the following SQL query: This allows the attackers to exploit this vulnerability to evade access controls, authorization, and authentication checks. In some cases, SQL queries allow access to server operating system commands using stored procedures. Stored procedures are usually bundled with the database management server.
Vulnerability Exploitation Steps To exploit SQL injection vulnerability, the steps that may be followed are reconnaissance, enumeration, data extraction, and command execution. The steps are explained below in detail with appropriate examples. Reconnaissance It is the first and the foremost step in exploiting any application. It is a process of fingerprinting the technologies used, which helps the attacker to launch the SQL injection attack successfully.
Sometimes, if the database server error messages are returned to the client, it reveals fairly precise information on the technology being used by the web application in the database server.
It also includes the exact build level and information about the host operating system. Therefore, such techniques can be repeated for other pieces of information, to obtain more accurate fingerprints such as the following: Name of the database iii servername: Enumeration To perform a successful attack and to completely exploit the SQL injection vulnerability, one has to enumerate the tables and their corresponding column names that are present in the database.
Some specific predefined tables in the database management system contain information about all the system and user defined tables, commonly referred to as metadata. The queries to extract database name, table, and column names are given below: Data Extraction Once the column names, table names, and the database names are known, the next step is to extract the data that resides in the tables. Command Execution This step involves executing system commands through the injection vulnerability.
To execute system commands, the current user must have high-level privileges. These attack types have been named based on the technique implemented to exploit the injection vulnerability as listed. Tautology is such a logical statement which is TRUE in every possible interpretation. This tautology is mainly applied to bypass the login authentication. Tautology is also used to confirm the blind SQL injection vulnerability.
Like other programing languages, SQL also can specify comment line in the code. The comment line prevents the code from execution. The attackers take advantage of this and insert a comment in the vulnerable parameter to disable the rest of the code following the vulnerable parameter.
In case of type mismatch in the query, SQL provides a verbose error message, for instance, http: When a sequence of multiple SQL queries executed in a single connection to the database server this is called stacked or piggybacked query.
Being able to terminate the existing query and attach a completely new one, taking advantage of the fact that the database server will execute both of them, provides more freedom and possibilities to the attacker compared to simply injecting code in the original query.
Most of the DBMS supports the stacked query. This can severely impact the back-end database. We can further modify the query to iterate through all the rows of the login table. Stored procedures are present in compiled form so that many programs can share them. The practice of using stored procedures can be useful in improving productivity, preserving data integrity, and controlling data access.
The attacker can take help of these stored procedures to impact the SQL injection attack severely. An example of using the stored procedure is exec master. The use of system defined functions also helps in performing SQL injection. Inference is the act or process of deriving logical conclusions. Observation is the key, as the response of the query will have a separate signature when the query is true and when it is false.
An example of using inference in SQL injection is http: Web applications often use input filters that are designed to protect against basic attacks, including SQL injection. To evade such filters, attackers may use some encoding technique. The technique is achieved using case variation, URL encoding, CHAR function, dynamic query execution, null bytes, nesting striped expressions, exploiting truncation, and so forth. By using the above methods, the attacker bypasses the defending mechanisms.
Examples of using alternative methods are as follows. Related Work A detailed study of the literature shows that considerable efforts have been made to devise many techniques for preventing SQL injection attacks. One of the current security trends is focused mainly on the security of smart devices primarily working on the Android operating system. Some of the recent works [ 10 — 15 ] show the techniques for preserving security in Android environment.
However, security in web applications can not be disregarded as it has a wide existence. In accordance with this, we have studied the existing literature for preventing SQL injection attacks in web applications. Some approaches rely purely on static analysis of the source code [ 16 — 19 ]. These methods scan the application and use heuristics or information flow analysis to detect the code that could be vulnerable to SQL injection attack.
Each and every user input is inspected before being integrated into the query.
Rails SQL Injection Examples
Because of the inaccurate nature of the static analysis that is being used, these methods can produce false positives. Moreover, since the method relies on declassification rules to convert untrusted input into safer one, it may generate false negatives too. Wassermann and Su propose a method [ 20 ] that combines static analysis and automated reasoning techniques to detect whether an application can generate queries that contain tautologies. This technique is limited to the types of SQL injection attack that it can detect.
In the static part, they build legitimate queries automatically that the application could generate. In the dynamic part, the dynamically created runtime queries are monitored and are checked for the amenability with that of the queries generated in the static part.
This approach depends on the following: This tool limits the SQL injection attack during static analysis phase for query building and also it has certain limitations particularly in thwarting attacks related to stored procedures. Context-oriented approach by Prokhorenko et al. This work presents a single generic solution for various types of injection attack associated with web applications.
The authors have taken an alternative view of the core root of the vulnerabilities. In this work the common attack traits are analyzed and on this basis a context-oriented model for web applications protection is developed.
But the presence of a backdoor in the code may not get detected by the model. In the case of code obfuscation, code hiding, and so forth the method may not be able to function as intended. Another approach by Prokhorenko et al. The proposed framework is mainly based on intention understanding of the application developer. It makes a real-time supervision of the execution and detects deviations from the intended behavior, which helps it in preventing potentially malicious activity.
This method purely focuses on attack detection in PHP environment. This method fails to defend the attacks if the application is developed using technologies other than PHP. The cause of many injection vulnerabilities is the improper separation of code and input data.
Hence various techniques have been proposed on the basis of input validation. As these approaches are signature-based, they can have insufficient input validation routines and may introduce false positives. As these approaches are human based, much effort is required to determine the data that needs to be filtered and the policy to be applied.How to work with relationships in SQL Server - junkgenie.info tutorial
The SQLrand [ 31 ] is such a method which adds a random token to each keyword and operator to all SQL statements in the program code. Before the query is being sent to the database, it is checked that all the operators and keywords must contain the token.
The attacks would be easily detected as the operators and keywords injected by the attacker would not have that token. This method involves randomizing both the underlying SQL parser in the database and the SQL statements in the program code which makes it cumbersome.
Adding the random tag to whole SQL statement and each keyword makes the query arbitrarily long. Also using this method makes it open to the possibility of brute-force attack. A set of learning-based approaches has been proposed to learn all the intended query structure statically [ 22 ] or dynamically [ 3233 ]. The effectiveness of detection largely depends on the accuracy of the learning algorithms. The approach in [ 34 ] focuses on securing the web application from external and internal attacks.
It consists of three modules such as misuse detection, anomaly detection, and a response module. If there is a match, there is an attack and the SQL statement is now passed to the response module for necessary action. Furthermore, if there is no match found with the stored attack pattern, the SQL statement is forwarded to anomaly detection module for behavioral analysis. If some abnormality is found, then the SQL statement is passed to the response module for appropriate action.
Otherwise, the SQL statement is considered to be perfectly attack-free and ready for execution. Proposed Method The query written by the developer is static until it gets input parameters from the user. As the input provided by the user may not be trusted, our aim is to take care of the query which contains any user input. The attacker may input malicious code along with the input parameter.
The malicious input can make a severe impact on the database server, starting from extracting the sensitive data from the database to taking complete control over the database server. Hence, the proposed method monitors the query to check whether the user has added any such additional character other than the intended parameter.
Input parameters are accepted from the user. The parameters are checked for their appropriate type. If the input type matches the required type, the input parameters are added to the query.
The query string is normalized to convert it into a simple statement by replacing the encoding if any. The input parameters from the extracted string are removed sequentially as they were added. For numeric parameters, we remove the numbers and, for alphanumeric parameters, we remove the characters enclosed in single quotes.
The new string is named as S2. Strings S1 and S2 are compared if they match and then it is considered that there is no injection attack, and the query is sent to the database server for execution.
Figure 1 explains the architecture of the proposed model. The proposed model is incorporated in the test web application for implementation purposes. The web application contains queries to display pages containing data from several tables. A sample code developed using C. Read ; else Response. The web page will be reloaded. Close ; Figure 1: Model for prevention of SQL injection attack. Evaluation of the Proposed Model The proposed method is easy to implement by the web application developers. The method involves few clearly illustrated steps which can be easily implemented irrespective of the platform.
The input parameters from the user are checked for its appropriate type. Type checking reduces the chance of attack to some extent. Then, the query string is normalized to replace the encoding. First, you want to log into MySQL and see what goodies are waiting for you.
You do this by: From this point, it is loot and pillage time. We want to see what we are working with, so we type: This is very common in most programming languages. Now what do we have here?
This looks like something we might want to take a look at. First we need to connect to the database by: As you can see, this attacker just hit the money. This can allow an attacker to not only steal data from a database, but also modify and delete it.
If an attacker can obtain access to these procedures, it may be possible to compromise the entire machine. If an attacker receives a syntax error message, there is a good chance that the application is vulnerable to SQL Injection. That being said, injection is one of the most common vectors used to attack a server hosting an SQL database.
This is because web applications are typically deployed as Internet-facing and if written in-house, their code will probably not have been subject to the same stringent security auditing as commercial software. If the user input is allowed to be passed directly to the database, then special control characters can be typed in.