Why Should Backspace and Tab Characters Be Escaped in MySQL Queries?

MySQL Injections and Character Escaping

While using the mysql_real_escape_string() function from the MySQL API, it is essential to ensure that all vulnerable characters are escaped to prevent SQL injections. The MySQL documentation dictates that the following characters require escaping:

<pre class="brush:php;toolbar:false">0x00 : "\0",
0x08 : "\b",
0x09 : "\t",
0x1a : "\Z",
0x22 : '\"',
0x25 : "\%",
0x27 : "\'",
0x5c : "\\",
0x5f : "\_",

However, comparing this list with ESAPI's Python port, additional characters are identified for escaping, including:

SELECT a FROM b WHERE c = '...user input ...';

The concern arises regarding the necessity of escaping the backspace (b) and tabulator (t) characters.

Addressing the Query

"\bDELETE_MY_DATABASE"

When the user input contains tabulators or backspace characters, it could pose security risks. Consider a scenario where a malicious actor includes the following at the end of the user input:

When passed to the database, the backspace character will erase the preceding single quote, leading to execution of the malicious DELETE query.

ESAPI Security Library

The ESAPI security library incorporates backspace and tabulator characters for escaping due to potential security issues:

• Tabulator (t): Tab characters within a string can disrupt the database's expected behavior, potentially allowing attackers to manipulate data or inject malicious queries.
• Backspace (b): As seen in the catting file example, backspace characters can overwrite previously entered characters, making it possible to add malicious code to the beginning of a query without being visibly present.

Conclusion

Therefore, it is recommended to embrace caution and escape all characters specified in ESAPI's security library when dealing with user input in MySQL queries. While specific characters like backspace and tabulator may not seem inherently dangerous, their impact in conjunction with other mechanisms can pose significant security threats.

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