This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 7 years ago.
If user input is inserting without modification from SQL query, then the application becomes vulnerable to SQL injection, like in the following example:
$unsafe_variable = $_POST['user_input'];
mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");
That's because the user can input something like value '); DROP TABLE table;--, and the query becomes:
INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')
What can be done to prevent this from happening?
There is extensive information through simple Google searches that can guide you in the right direction. To start though:
DON'T USE MYSQL_* FUNCTIONS These are deprecated and will generate warnings. They are not even remotely good practice for modern web development.
USE A DATABASE LIBRARY INSTEAD like PDO or MySQLi. There's plenty of tutorials to get you started and most importantly these libraries take care of SQL injection for you. So use them!
Related
This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 6 years ago.
If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:
$unsafe_variable = $_POST['user_input'];
mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");
That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:
INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')
What can be done to prevent this from happening?
The absolute minimum you need to do here is escape that variable:
$unsafe_variable = mysql_real_escape_string($_POST['user_input']);
Nothing in your query has to change at that point. This is not necessarily the end of the story, though, as mysql_real_escape_string is not invulnerable and you remain exposed to injection attacks by those using more sophisticated techniques.
The entire mysql_query API has been trashed, it's obsolete and the latest version of PHP no longer supports it. You need to move on to something better, and I'd recommend PDO as a baseline.
The best way to be sure you're doing it right is to use prepared statements with placeholder values. That is your query looks like this:
INSERT INTO table name (column1) VALUES (:column1)
With PDO you can name your placeholders. This makes executing your statement later very easy, you just match up the values:
$stmt->execute(array('column1' => $_POST['user_input'));
So the best way to avoid injection bugs is to avoid injection in the first place. Placeholder values will be substituted correctly, safely, and most important, consistently. All it takes is one mistake where you thought you escaped something but you didn't and people can bust your site wide open.
Hi I want to show sql injection vulnerability through form input using PHP and MYSQL. Any suggestion how to go about.
Thanks
mysql_query("INSERT INTO `table` (`column`) VALUES ('$inject_variable')");
If you have query like this you can insert something like value'); DROP TABLE table;-- to the $inject_variable to test the injection.
Hence, your SQL query will became this:
INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')
This will allow other users to drop the table.
You can use Kali Linux to hack into the php website. Here is a tutorial on how to do that.
This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 7 years ago.
I read so much about types to prevent sql injections. I probably don't want to use prepared statements if there is another way to prevent them by 100% of the cases.
Currently I'm sticking to this:
$safe_var = mysql_real_escape_string ( $unsafe_var);
mysql_set_charset("utf8");
$sql = "REPLACE `news` (`id`, `author`, `title`, `text`, `time`)" . "VALUES ('".$id."', '$author', '$title', '$text', UNIX_TIMESTAMP());";
mysql_query ( $sql );
For this example all the variables in the sql statement are constructed as the safe_var at the start. I see many opinions on what is save in sql and what not so I don't know what is right.
My question is, is this 100% save and is it save to use this way in every possible sql statement, by using mysql_real_escape_string and putting the variables in single quotes as I did in the statement?
Thanks in advance for help!
PS: I know there are many question likes this but everyone keeps saying diffrent stuff and I still not found anyone that says that my way is safe from sql injections in every possible statement.
At the least you would want to convert to mysqli rather than mysql. You would want to also further test the user input as much as possible to ensure it is legitimate.
Highly recommend pdo and prepared statements
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
MySQL Injection - Use SELECT query to UPDATE/DELETE
So I have found in my site bug that allows to perform sql injection
http://mysite.com/script.php?id=1 union select 1,2,3 will output all fields that has Id property equal to one plus one additional row with 1,2,3. I know that I have to validate user input to close my bug.
However my question is quite another. Is it possible to perform update query or insert query? I am able to comment query using --, however I cannot use multiple statements that are delimited by ;. So is it possible to perform update query in my case. I can show PHP code and SQL query if needed.
$sql = "SELECT id, title, text from table where cId=$val";
$result = mysql_query($sql);
$array = mysql_fetch_array($result);
//echo rows in table
Judging from MySQL Injection - Use SELECT query to UPDATE/DELETE
all that is protecting you is a limitation of mysql_query. I would not rely on this, and in particular not that it remains this way over time. You should never rely on a feature to be disabled by default. Maybe the next version already allows statements such as.
SELECT id, title, text from table where cId=1; DROP table table
Nope it is not possible. Most probably you ar running mysql_query, that would not allow multiple queries to be run in one pass. And hence if your query starts with SELECT (as it does), it would not allow any UPDATE injection
Edit: Use mysql_real_escape_string on your input even then
By default this should not be possible. Although there are options for mysql_query to run multiple statements in one string since MySQL 5.0 which you have to set with mysql_set_server_option.
Please consider changing your statement command like this to use mysql_real_escape_string:
$q = mysql_fetch_array(mysql_query("SELECT id, title, text from table where cId = " . mysql_real_escape_string($val)));
At the very best you change your code to use PDO since all mysql_* functions are officially deprecated.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Best way to prevent SQL injection in PHP?
I am building my first online shop and i'm writing the PHP code myself and using a MySQL database. I have been advised that its really important to have data validation on inputs so that my database cannot be compromised. Can someone tell me what validation to include or maybe a trusted tutorial that is recommended.
Thanks in advance
Search this site for "Sql Injection". A common source of sql injection attacks is user-input which is not validated and is then trustingly concatenated before being sent to the database.
For example, if your statement is this:
select col1, col2 from mytable where id =' + <some variable> + ' and xyz = abc
(where 'some variable' is user input just passed on to the SQL)
then the user can input 'xxx''; delete from mytable; --'
and what the database gets is:
select col1, col2 from mytable
where id ='xxx'; delete from mytable; --' and xyz = abc
causing havoc.
So the key issue here is: don't pass unvalidated, concatenated text to your database for it to execute.
You can achieve this in several ways:
check the input for unwanted characters (difficult to cover
everthing)
build your SQL as parameterized SQL i.e. binding user input to
parameters
invoke stored procedures (I like them but they are not everyone's cup
of tea)
I'd go for parameterized SQL as the database driver will take care of binding everything the user inputs as a single value, whilst at the same time keeping your business logic out of the database.
Mysql Validation means you have to prevent your queries from MySql injection. Please read the following to avoid mysql Injection.
http://rosstanner.co.uk/2012/01/php-mysql-preventing-mysql-injection/