![]() Why MySQL requires a whitespace character after the double dash? #īy reading the MySQL documentation we can read: ![]() MySQL, that's why it is safer to use - such as -īecause if URL-encoded into -%20- it will be still decoded as. %2B and so when it will be decoded -+ won't be recognized as valid by instead of + and _ instead of / ( RFC 4648).īut if the -+ is encoded (eg. URL-safe and filename-safe base64) is using Means a URL decoded will decode the plus sign as a space and will transform back for UTF-8 U+0020 SPACE will be encoded as U+002B (+). So why -+ exists? Because in the URL standard the space character is encodedĪs a plus sign, eg. That's why you often see -, adding any character ofter the whitespace so ![]() Whitespaces and so a - may be transformed into - and soīut MySQL is one of the most popular DBMS so we need to have a generic payload This means that web browsers, web frameworks, application backends, proxies, underlying languages, may all trim trailing But most of the time, SQL injection are exploited Yes, MySQL needs that the two dash are followed by a whitespace character This syntax differs slightly from standard SQL comment syntax, as discussed in Section 1.8.2.4, "'-' as the Start of a Comment". In MySQL, the - (double-dash) comment style requires the second dash to be followed by at least one whitespace or control character (such as a space, tab, newline, and so on). When I said all DBMS supports the double dash syntax, it's not exactly true.įrom a - sequence to the end of the line. So if - is supported by all DBMS why do we see most of the payloads ending This is also the only one supported by all DBMS. The only inline comment in standard SQL in the double dash - , use manyĭifferent custom implementation of SQL (Structured Query Language). Microsoft SQL Server, SQLite, Apache Ignite, Firebird, IBM DB2, etc. MySQL (Oracle MySQL, MariaDB, Percona Server), Oracle Database, PostgreSQL, We'll not use an unclosed multi-line comment as it may comment too much or even That detecting which one it is can be difficult, a pentester would prefer to use There are many DBMS and the comment support is different for each one of them.Īs with a black box approach one may not be aware of which DBMS is used and and there are also some weirder uncommon syntax. Some less common %00 comparable to a null byte injection, some supports Some DBMS (Database Management System) supports inline comments like # or -, So to avoid any uncontrolled and unexpected side effects, a pentester wants toĮnd his payload with a comment to neutralize and end the query so theīehavior becomes more predictable. Of the query or multiple times in the query, you don't really know. Your input may be injected at the beginning Injection (SLQi) by fuzzing with common payloads.Įxcept if there is a verbose error disclosing the original SQL query, you are But it is a good approach to have a white space after # to increase readability.When doing penetration testing using a black box approach, you may find a SQL It is not required to put a white space after #. If you do not use a line break after the comment, everything that comes on the same line will be commented until it encounters a line break. This comment is used at the end of the SQL query and must have a line break after it. We use # to write a single-line comment in the MySQL query given below. Let’s create a table named tb_teachers to practice MySQL comments. We can use MySQL single-line comments in two ways, either by using # or. We can use #, -, or /* and */ symbols to comment. There are three different ways to write MySQL comments. We will also have a look at the executable comments and their uses. We will see how we can use single-line and multi-line comments in MySQL. It also helps the other programmers to understand what is happening in code. We also use comments to ignore a certain part of the code while parsing SQL queries (don’t let that piece of code be executed). Comments are written to describe the code, make it easy to understand.
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