What does sql injection vulnerability mean?

Today, I will talk to you about the meaning of sql injection vulnerabilities, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

The SQL injection vulnerability refers to inserting maliciously entered SQL commands into Web forms to submit domain names or enter query strings for page requests, resulting in deceiving the server into executing malicious SQL commands.

SQL injection vulnerability

As the name implies, the SQL injection vulnerability allows an attacker to inject malicious input into a SQL statement. To fully understand this problem, we must first understand how server-side scripting languages handle SQL queries.

For example, suppose a feature in a Web application generates a string using the following SQL statement:

$statement = "SELECT * FROM users WHERE username = 'bob' AND password =' mysecretpw'"

This SQL statement is passed to a function that sends a string to the connected database, parses it, executes it, and returns the result.

You may have noticed that the statement contains some new special characters:

*: is an instruction for the SQL database to return all columns of the selected database row

=: is an instruction for the SQL database to return only values that match the searched string

': used to tell the SQL database where the search string begins or ends

Now consider the following example, where a site user can change the values of "$user" and "$password", such as in a login form:

$statement = "SELECT * FROM users WHERE username ='$user' AND password='$password'"

If the application does not clean up the input, the attacker can easily insert any special SQL syntax into the statement:

$statement = "SELECT * FROM users WHERE username = 'admin'; -' AND password= 'anything'"; =' anything' "

Admin'; -: is the attacker's input and contains two new special characters:

;: used to indicate that the current statement of the SQL parser has ended (not needed in most cases)

Indicates the rest of the line for the SQL parser

This SQL injection effectively removes password authentication and returns the existing user's dataset, in which case "admin" attackers can now log in using the administrator account without specifying a password.

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