I have the following code, which is vulnerable to SQL injection(I think?):
$IDquery = mysqli_query($connection, "SELECT `ID` FROM users WHERE username=$usernamelogin");
I don't escape the $usernamelogin, and that is not a parameterized query. This obviously needs to be fixed, you don't need to point that out, that isn't what this question is about. Before I fix it, I want to make sure I understand how an SQL injection works as well as possible. So, I tried creating a table named "droptable" and inputting the following into the username input:
x; DROP TABLE droptable;
Which I believe should input this SQL query:
SELECT `ID` FROM users WHERE username=x; DROP TABLE droptable;
However, droptable still exists, and the rows in it are untouched. Could anybody tell me why?
mysqli_query() doesn't support multiple query execution.
You don't have quotes around $usernamelogin so when you supply a string that would produce an error. Either add quotes or supply a number
Related
I am trying to inject into a dummy website I have made, its a simple form which uses the text input to send data to my php file and then outputs the data gathered. The following is my code for the SQL.
$id = $_GET['id'];
$id = $_GET['id'];
$data = $conn->query('SELECT * FROM users WHERE username = ' . $conn->quote($id));
foreach($data as $row) {
echo $row['id'].' '.$row['username'];
}
When I try to use things such as unions I get no data back and if I put an apostrophe at the end of the URL I don't get a MySQL error. Could someone please explain why the site is secure from SQL injections?
As there are some confusions as to what I asked my final goal is to be able to get into the information schema so I have been trying to use statements like to get into the schema but without success:
' and 1=1 union select table_name,table_schema from information_schema.tables where table_schema='users' #
Other apparently may have missed what you were asking...
You are INTENTIONALLY trying to sql-inject your own site, such as for personal learning on how NOT to, but also see what impacts sql-injection CAN do. If so, take a look at your statement and see "what would I need to add to fake it out".
"SELECT * from users WHERE username = '$id'"
If the user puts a value such as "Bill" for the $id, it would become
"SELECT * from users WHERE username = 'Bill'"
and run no problem. Now, you want to inject and see ALL users, a common way is to close the quote and then add something else that will always return true... such as a user puts a value of
' OR 1=1 ;--
The above would result in
"SELECT * from users WHERE username = '' OR 1=1;-- '"
The semi-colon and dashes are important to "finish" the original query, and then indicate that anything after the dashes are comments so it won't try to execute anything AFTER the otherwise dangling close quote from your original query build construct.
Hopefully that helps answer why you may be failing while TRYING to inject into your own site.
COMMENT FEEDBACK
I don't know why my version would not work, I am not trying to union anything, just force an all records returned.
With respect to your UNION clause, that looks ok, but if your users table has 3 columns and your UNION is only 2 columns, that should fail as the union should be the same number of columns as in the original query. THAT would cause a failure on execution, but not enough specific information to confirm.
Most likely, you have magic quotes enabled, which is saving your otherwise-vulnerable code.
Don't rely on it.
As it can be clearly seen from either question and answers, most people don't understand what injection is. For some strange reason everyone takes injection consequences for injection itself. While injection is just a query creation. No more, no less.
So, the result of injection is not whatever data returned, but mere SQL query string. Thus, what the OP have to check is the resulting SQL query. It is extremely simple a task, as primitive as just echoing the query string out. This will reveal injection possibility immediately, without toilsome guesswork and sophisticated query building.
Simple output like this
SELECT * from users WHERE username = 'Bill\''
will tell you that magic quotes are on and whole question is a thousand-times-duplicate and not-a-real-one at once.
UPDATE
For some strange reason the code in the question mysteriously has been changed to invulnerable PDO based code. Which leads me to believe that whole performance were just a mere trolling.
Your injected SQL String should look like this
-1'/**/UNION/**/SELECT/**/1,##VERSION/**/FROM/**/users/**/WHERE/**/1='1
as you need to close the last ' in the final sql query
Update:
like Your Common Sense pointed out
For some strange reason the code in the question mysteriously has been changed to invulnerable PDO based code. Which leads me to believe that whole performance were just a mere trolling.
If I only run a SELECT query, should I worry about sql injection? My site has only a few input fields, and all they do is look up information. I never delete, update, etc...
It doesn't matter what kind of query you're trying to do. The SQL injection can end your query and start another one, which could be a DELETE, UPDATE, or INSERT. This is the lesson of Little Bobby Tables
Yes, you have to worry. It doesn't matter what queries do you execute inside PHP or whatever script you use. An evil user can submit something like "; DROP DATABASE and you'll be sorry for that.
Yes, you should. SQL injection doesn't have nothing to do on what is the original query about. It can inject any command of any clause on your query.
On PHP is really simple to make your site/system/project protected.
Take a look on this official documentation with examples of this tecnique and here, how to avoid it, using mysql_real_escape_string.
UPDATE: I have used it once using this ' or 1=1 or ''=' on both username and password fields of a login page. It results on a query like this select * from user where username = '' or 1=1 or ''='' and password = '' or 1=1 or ''='' and may return a record.
See this example of how it works.
If you are going to SELECT based on the user's input, then you do have to worry about it, since the user can put anything on the input field.
I have a weird problem.
I have a table which has a title field.
I am inserting values into this title field using mysql_real_escape_string. Inserting is working fine for values with single quotes.
Some other place I am doing a select using title filed in the where clause as below
SELECT * FROM table WHERE title=mysql_real_escape_string(Girish's Photo);
This query is returning empty result set even when I inserted Girish's Photo.
---- Editing to put some code
$photo_title=mysql_real_escape_string($_POST[photo_title]);<br/>
$sql = "INSERT INTO photos values($id,'$photo_title');<br/>
using this from a form I have inserted Girish's Photo into photo_title. It worked fine.
...
..
..
Then at some other place in PHP
$title="Girish's Photo";
$sql = "SELECT photo_id,photo_title FROM photos WHERE photo_title ='" . mysql_real_escape_string($title)."'" ;
But this query is returning empty result set.
Using phpMyAdmin, if I try to run the above query .. the result is empty. If I browse the table I see value Girish\'s Photo
Now if I run the query on phpMyAdmin replacing where clause with where photo_title='Girish\''s Photo' I am getting the record.
$data = "Girish's Photo";
$query = "SELECT * FROM table WHERE title='".mysql_real_escape_string($data)."'";
mysql_real_escape_string() is a PHP-function, which should be used as follow:
"SELECT * FROM table WHERE title='".mysql_real_escape_string("Girish's Photo")."'";
However, this is bad practice.
Okay so you're going to want to use PDO for all queries. Primarily for the following reasons:
mysql_* is being deprecated.
It's not safe from SQL Injection.
PDO is capable of accessing numerous database engines making it much more flexible without changing the API.
Please take a look at this post to get a look at how to issue a SELECT using PDO.
Parameterized SELECT queries via PDO?
I had a similar problem recently which I solved by using htmlentites() instead of mysql_real_escape_string() check it out in the manual or w3 schools
EDIT: this is a valid answer because he's using mysql_real_escape_string() in the wrong context in the first place. if you read the question, he's escaping a FILENAME and therefore he's not at risk of injection. If you're going to downvote at least say why..
The value in your database should not contain backslashes. That's why your query doesn't match. Girish's Photo does not match Girish\'s Photo. Sounds like you are a victim of magic quotes. Read the manual and get rid of them.
Why should we escape double quotes,single quotes creating queries in PHP? are there any particular benefits when doing that? or it is just a good practice?
It is required to make your queries work and secure. Consider the following code:
$name = "O'reilly";
$sql = "INSERT INTO users (name) VALUES ('$name')";
The result SQL would become like this:
INSERT INTO users (name) VALUES('O'reilly');
Which simply doesn't work. It needs to be properly escaped:
INSERT INTO users (name) VALUES('O\'reilly');
The same applies for other special chars.
Prevent SQL injection
Consider this query:
DELETE FROM users WHERE username='$username';
Where $username is obtained from $_POST. If an attacker managed to post string like ' OR 1; -- as the $username then the query becoming this:
DELETE FROM users WHERE username='' OR 1; -- ';
which is valid and the WHERE always evaluates to true and you will have to give good explanation to your angry users.
See also: Best way to prevent SQL Injection in PHP
If you do not escape quotes, The query ends at the place of single quotes. So your query will not be executed successfully!
E.g.
$qry = "SELECT * FROM user WHERE email='test#test.com'";
It works fine but if any one enters email='test'#test.com' then query ends at 'test' only and not find any rows with that one.
So it prevents also a sql injection!
s, to prevent from SQL injection attacks.
To know SQL injection
http://www.tizag.com/mysqlTutorial/mysql-php-sql-injection.php
http://www.homeandlearn.co.uk/php/php13p5.html
To prevent PHP Sql injection
https://stackoverflow.com/a/60496/781181
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Closed 11 years ago.
Possible Duplicate:
What is SQL injection?
I see a lot of php code floating around on stackoverflow and (too) little escaping of strings.
Can anyone
Explain what SQL injection is;
Explain what it can do to your server, data and code;
Give an example how to perform an SQL-injection
Give php sample code how to protect against SQL-injection
An SQL injection is a maliciously formed SQL query used to "confuse" an SQL database into giving something it shouldn't. For instance, consider the following query
"SELECT * FROM `users` WHERE `username` = '$name'";
In a normal case, this will work. If we submit 'Jack' to this, it will return all users named Jack. However, if a user enters, say "' OR 1=1", the resulting query would be
"SELECT * FROM `users` WHERE `username` = '' OR 1=1";
Since 1 always equals 1, and the combinating clause is OR, this will return true on every row, which will in turn display EVERY row to the malicious user. Using this technique, someone can view your entire database. Also consider if someone submits something like "'; DROP TABLE users";--, which results in
"SELECT * FROM `users` WHERE `username` = ''; DROP TABLE `users`";--";
Which is two queries, one which will do nothing, the second which will delete the ENTIRE users database, resulting in the loss of your data.
The best method to prevent SQL injections is to use prepared statements. With these, you send a query to the SQL database that says something like
"SELECT * FROM `users` WHERE `username` = '?'";
This lets the database know the format of the query (WHERE username equals some value), so there is no confusion when given a plain text query. Then the database knows to expect one value, and where to put it. Then you pass that value to the database which it can use to search. This is also better as the database can optimize the query for faster searching.
Read up on prepared statements, which will explain this in more detail.
I cannot resist aswell.
SQL Injection is "a code injection technique that exploits a security vulnerability occurring in the database layer of an application". In other words it's SQL code injected in as user input inside a query.
SQL Injections can manipulate data (delete, update, add ecc...) and corrupt or delete tables of the database. I'm not aware of SQL Injections manipulating scripts though.
Let's say in your PHP script you are expecting (as user input) a username and a password from the login form that are later used inside a query such as:
SELECT Id FROM Users WHERE Name = $name AND Password = $password;
The user can insert inside $name and as $password whatever he likes (for example trough an <input>). Let's imagine he adds a name such as "1 OR 1 = 1; --", the query will now look like:
SELECT Id FROM Users WHERE Name = 1 OR 1 = 1; -- AND Password = $password;
and then, after the ; I could add another query or make the script think that the username and the password actually exists.
Notice that -- AND Password = $password; is a SQL comment and will therefore be ignored.
If you are using PHP < 5 then you should look for mysql_real_escape_string() and use it to escape user inputs before embedding it inside a query.
If you are using PHP5+ you should use PDO or the mysqli extension which can prevent this problem via prepared statements.
I cannot resist posting this.
1- Sql Injection is explained better in one cartoon, than most other documents.
2- Mostly it does not do much to the server, but only to the underlying data. Consequence include delete, insert , select records, drop, create tables. (based on permissions etc..)
3- Examples.
4- Sorry I do not know PHP. But as long as you can abstract your DB layer from your View, you should be fine.
There's a lot of information out there (and elsewhere in here) about this subject, so do not take this answer as a complete list by any means and continue to research on your own...
Explain what SQL injection is;
Explain what it can do to your server, data and code;
Give an example how to perform an SQL-injection
Give php sample code how to protect against SQL-injection
SQL injection is where an attacker discovers that an input value supplied to your application is being sent directly to a database and realizes that they can craft that input to be a custom SQL command. It could be something as simple as entering a special character (such as %) into a text field and receiving a strange response.
It can do anything your database allows that command to do. For example, if your web application has DB owner permissions for the application's database then an attack can potentially drop tables or even drop the whole database. Or, with even normal application permissions, the attack can over-write data or read sensitive data (such as plain text passwords if you have those).
For example, if an application has a text field where you enter a username. If that field is open to SQL injection, an attacker can enter something like: MyName';DROP TABLE Users;-- In this example, the attack manually finishes the query with the closing single quote and semi-colon, then adds another query, then comments out anything afterward. If not protected against this, the database may run both queries.
This one I don't know updated enough information, but there's lots out there :)