Okay, so say I have some user input that selects something from a mysql database.
I want to be safe from mysql injection so in order to do so I'd use the mysql_real_escape_string() function. But after that, I want the quote or whatever is bad from my string out of the variable completely.
EXAMPLE- :
my title variable = Herp'
escape with mysql_real_escape_string()....
then my variable = Herp\'
Now, I want the bad quote out of there. So, I want to remove the backslash & character after the backslash.. so it looks like 'Herp'.
How would I do that?
sorry if that's confusing.
If you just want to filter out quotes instead of escaping them, simply try
$myTitleVar = str_replace(array("'", '"'), '', $myTitleVar);
Before inserting it into the DB, I'd still recommend running it through mysql_real_escape_string() or even better, use PDO and parameter binding.
use stripslashes
but I would dig why that is happening. Check your magic quotes settings. For safety reasons is it good to have then set to off
Related
When I post a variable to the database, of course, I use mysql_real_escape_string. This way special characters go in the database as it should.
When I read this variable out of the database, I use mysql_real_escape_string again together with stripslashes:
$var = stripslashes(mysql_real_escape_string($record['rowname']));
else it will give me slashes before quotes.
When I use this $var I mentioned above and want to echo it, I simple can echo "$var" because it has already been stripped and escaped, right?
And beside, if I use stripslashes + mysql_real_escape_string on a variable, then POST this same variable again in the database, is mysql_real_escape_string enough? Or do I need to stripslashes this variable again?
Summarized:
As I know how this works:
use mysql_real_escape EVERY time when using data with mysql: when reading query through variables just as posting variables to database.
Use stripslashes when echoing out escaped variables.
If you want to post stripslashes and escaped variables again to the database, you dont need to stripslash it again.
Do I miss htmlspecialchars?
EDIT
So this is all wrong?
while( $record=mysql_fetch_array($result) )
{
$custid=mysql_real_escape_string($record['custid']);
$custsurname=mysql_real_escape_string($record['custsurname']);
$custmidname=mysql_real_escape_string($record['custmidname']);
$custforename=mysql_real_escape_string($record['custforename']);
$custcountry=stripslashes(mysql_real_escape_string($record['custcountry'])); }
I'm afraid you're doing it wrong. The key point is that escaping is context sensitive and you completely disregard that fact.
On every data format, there're words or characters that are assigned special meanings in the format spec. For instance, a ' symbol in SQL means "string delimiter", a ? symbol in a URL means "start query string" and a < symbol in HTML means "start tag". You need escaping when you want to insert a literal word or character, i.e., you want to insert it as-is and remove its special meaning.
Once aware of that, it's clear that the syntax varies depending on the format and context. < means "start tag" in HTML but not in SQL or URLs. Thus you need to use a escaping method that's built for the target format and follows the format rules.
If you do mysql_real_escape_string() on data read from a database you're saying "escape my data so it can be injected as inside a SQL string". Your data gets ready to be used inside as a SQL string but get's corrupted for any other usage.
In this example, it happens that stripslashes() undoes most of what mysql_real_escape_string() did so you end up with an output that's basically unchanged. But that's pure chance.
Last but not least, having to escape database input parameters one by one is very annoying. All other DB extensions but the one you are using1 offer prepared statements. Don't get stuck with a deprecated extension that doesn't offer modern stuff.
1 Note: the legacy mysql extension has been deprecated for several years, when better alternatives became available, and it's no longer part of the language.
Update: a little clarification—escaping is just a syntax trick. You don't alter the input to the eyes of the target engine, which just sees the original data as-is. So there's no need to unescape the input when you retrieve it.
You don't need to stripslashes or mysql_real_escape_string the data coming from database, you just need to escape it before you query so the query parser knows what are special characters and what are literal characters.
stripslashes should be never used (as a hack to fix some symptoms), if you are going to need a variable after escaping it, use the original one:
$data_safe = mysql_real_escape_string( $data );
//$data can still be used normally
Escaping is only for a certain context, if the context is a mysql query then you will mysql real escape just for the query and nothing else. If the context is html output, then you will htmlescape just before outputting a string as html. At no point you want to actually modify the data itself. If you misunderstand this, you will see O\'Brian and O'Brian etc.
to sanitize user input we usually use mysql_real_escape_string, but for example if i want to escape: O'Brian it will return O\'Brian and I don't really like this because if i want to print this name, I have to strip slasheseverytime.
So I thought to use this function:
$search = array("'", '"');
$replace = array("´", "“");
$str_clean = str_replace($search, $replace, "O'Brian");
Is this simple function protecting me from MySQL-Injection?
Thank very much and sorry for my bad English.
No - no more escaping!
Use mysqli or PDO and prepared statements
http://php.net/manual/en/mysqli.prepare.php
http://php.net/manual/en/pdo.prepared-statements.php
mysql_real_escape_string does add the \ for string escaping only and does not add them to the database, so you don't have to use stripslashes while displaying the content.
If you are really getting the \ stored in the database, do off the magic_quote
You should always use mysql_real_escape_string to escape input. This is for when you're writing values into your database, not when you're reading values from your database. When you write "O\'Brian" to your database, it's stored as "O'Brian", and when you read it back out, you should also get "O'Brian" (and won't need to strip the slashes, since they don't exist).
Yes, obviously it's protecting from SQL Injection attacks
It Escapes special characters in the unescaped_string, taking into account the current character set of the connection so that it is safe to place it in a mysql_query().
I'm doing this to all strings before inserting them:
mysql_real_escape_string($_POST['position']);
How do I remove the: \ after retriving them?
So I don't end up with: \"Piza\"
Also is this enough security or should I do something else?
Thanks
I would suggest you call $_POST['position'] directly (don't call mysql_real_escape_string on it) to get the non-escaped version.
Incidentally your comment about security suggests a bit of trouble understanding things.
One way of handling strings is to handle the escaped versions, which leads to one kind of difficulty, while another is to handle another and escape strings just before embedding, which leads to another kind of difficulty. I much prefer the latter.
use stripslashes() to get rid of the escape character.
Escaping is great. In case the value is going to be integer , I would suggest you do it like:
$value = (int) $_POST['some_int_field'];
This would make sure you always end up with an integer value.
It could be because magic quotes are enabled, so to make it versatile, use this:
if (get_magic_quotes_gpc()) { // Check if magic quotes are enabled
$position = stripslashes($_POST['position']);
} else {
$position = mysql_real_escape_string($_POST['position']);
}
mysql_real_escape_string() does add \s in your SQL strings but they should not be making it into the database as they are only there for the purpose of string parsing.
If you are seeing \s in you database then something else is escaping your stings before you call mysql_real_escape_string(). Check to make sure that magic_quotes_gpc isn't turned on.
When I add a comment using the variable below, apostrophes are printed with a backslash in front of them. How can I get rid of the backslashes?
Thanks in advance,
John
Example of printed result:
My roommate\'s brother\'s ex-girlfriend\'s aunt drive a Toyota.
$comment = mysql_real_escape_string($_POST['comment']);
mysql_real_escape_string() is adding backslashes, so you can inject your string safely into an SQL query -- this is acting as a protection against SQL Injections.
But this function should only be used when you want to build an SQL query -- not when you want to output something.
When you want to output a string to an HTML page, you'll generally use htmlspecialchars or htmlentities, to prevent XSS.
If you already have some backslashes before calling mysql_real_escape_string(), it might be because of Magic Quotes -- if so, you might want to first call stripslashes() on the input you get from the user, to not duplicate the backslashes.
from http://php.net/manual/en/function.mysql-real-escape-string.php
Note: If magic_quotes_gpc is enabled, first apply stripslashes() to the data. Using this function on data which has already been escaped will escape the data twice.
Isn't that exactly what mysql_real_escape_string is supposed to do? If you're still seeing the slashes after inserting the data into the database and fetching it back, make sure the magic_quotes_gpc server option is turned off.
I got this from for a login form tutorial:
function sanitize($securitystring) {
$securitystring = #trim($str);
if(get_magic_quotes_gpc()) {
$securitystring = stripslashes($str);
}
return mysql_real_escape_string($securitystring);
}
Could some one explain exactly what this does? I know that the 'clean' var is called up afterwards to sanitize the fields; I.e. $email = sanitize($_POST['email']);
Basically, if you have magic quotes switched on, special characters in POST/SESSION data will automatically be escaped (same as applying addslashes() to the string). The MySQL escape functions are better than PHP's addslashes() (although I can't remember the exact reasons why).
What your code does is check if the php.ini file has magic quotes turned on, if so the slashes are stripped from the data and then it is re-sanitised using the MySQL function. If magic quotes is not on, there is no need to strip slashes so the data is just sanitised with the MySQL function and returned.
First of all, this code is wrong.
It has wrong meaning and wrong name.
No SQL data preparation code does any cleaning or sanitization.
It does merely escaping. And this escaping must be unconditional.
and escaping shouldn't be mixed with anything else.
So, it must be three separated functions, not one.
Getting rid of magic quotes. Must be done separately at the data input.
trim if you wish. It's just text beautifier, no critical function it does.
mysql_real_escape_string() to prepare data for the SQL query.
So, the only mysql related function here is mysql_real_escape_string(). Though it makes no data "clean", but merely escape delimiters. Therefore, this function must be used only with data what considered as a string and enclosed in quotes. So, this is a good example:
$num=6;
$string='name';
$num=mysql_real_escape_string($num);
$string=mysql_real_escape_string($string);
$query="SELECT * FROM table WHERE name='$name' AND num='$num'";
while this example is wrong:
$num=6;
$string='name';
$num=mysql_real_escape_string($num);
$string=mysql_real_escape_string($string);
$query2="SELECT * FROM table WHERE name='$name' AND num=$num";
Even though $query2 would not throw a syntax error, this is wrong data preparation and mysql_real_escape_string would help nothing here. So, this function can be used only to escape data that treated as a string. though it can be done to any data type, there is some exceptions, such as LIMIT parameters, which cannot be treat as a strings.
trim() gets rid of all whitespace, and if magic quotes is on, the backslash is removed from any escaped quotes with stripslashes(). mysql_real_escape_string() readies a string to be used in a mysql query safely.
here are the docs for the functions used: http://php.net/manual/en/function.trim.php, http://php.net/manual/en/function.get-magic-quotes-gpc.php, http://php.net/manual/en/function.stripslashes.php, http://php.net/manual/en/function.mysql-real-escape-string.php
mysql_real_escape_string is used to escape characters in the string to add backslashes to characters such as ', which prevents an attacker from embedding additional SQL statements into the string. If the string is not escaped, additional SQL can be appended. For example, something along the lines of this might be executed:
SELECT * FROM tbl WHERE col = 'test' ; DELETE * FROM tbl ; SELECT 'owned'
magic_quotes does escaping of its own, although if I remember correctly its use is now discouraged. Besides, the MySQL function will do all the escaping you need to prevent SQL injection attacks.
Some (old) servers have magic_quotes enabled. That means that all external input is altered to (supposedly) escape it in order to be injected in a MySQL query. So O'Brian becomes O\'Brian. This was an early design decision by the PHP team that proved wrong:
You don't always need to inject input into database queries
Not all DB engines use back slashes as escape char
Escaping single quotes with backs slashes is not enough, even for MySQL
Your server security relies on a PHP setting that can be disabled
So it's way better to code without magic_quotes. The problem comes with redistributable code: you cannot know if the server will have magic_quotes enabled or disabled. So you can use get_magic_quotes_gpc() to detect it they're on and, if so, use stripslashes() to (try to) recover the original input.