This question already has answers here:
Can I protect against SQL injection by escaping single-quote and surrounding user input with single-quotes?
(19 answers)
Closed 6 years ago.
Context: I'm trying to convince a friend to switch to using parameterized queries to prevent SQL injections and other malicious attempts as that is the standards these days but he has a mentality of "If it's not broken, don't fix it."
Here's the code he currently uses:
function sql_safe($text) {
return str_replace("'", "''", $text);
}
Is there a way for me to break this function to illustrate to him that this approach is not advisable any more?
Additional Info
It's being used as a general means to protect the system from SQL injections so that user inputs are escaped properly. But I feel like his approach could break at certain scenarios which I haven't figured out yet.
Here's your code:
<?php
function sql_safe($text) {
return str_replace("'", "''", $text);
}
echo "SELECT * FROM db WHERE field = '" . sql_safe($argv[1]) . "';\n";
And here's the most obvious way of breaking it:
$ php ./x.php "\' OR TRUE; -- MySQL"
SELECT * FROM db WHERE field = '\'' OR TRUE; -- MySQL';
Stack Overflow has covered the topic of SQL injection extensively over the years. See for example Can I protect against SQL Injection by escaping single-quote and surrounding user input with single-quotes? . There's a neat trick in there that exploits "maximum length of string" to truncate just one of the replacement ''s.
Related
This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 6 years ago.
As the title says. If a user tries u upload a file with ' in title it throws error(it won't connect to server). Should I replace that sign during upload or something else. It just simple connecting to database
$b = "select * from doc";
$rez1 = mysql_query($b) or die("<span>error</span>");
I'd recommend using escaping methods instead of manipulating the input.
This ist the safest way to prevent SQL Injections. (And never tell the user, the technical details why something doesn't work, except you want some of them to exploit these exceptions)
Also, don't ever use the old and deprecated mysql* functions; learn PDO or mysqli instead.
If you were using mysql, then switch to mysqli and use this: mysqli_real_escape_string()
Otherwise, you could use a regex that repaces ' with \' -
preg_quote()
$string = "Something with 'quotes' ";
$res = preg_quote($string, "'");
echo $res;
will return:
Something with \'quotes\'
Which will cause no problem during the insertion.
This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 9 years ago.
Can't use PDO.
I have read many questions here, this is my first time trying to do something for people outside my office, so I need to sanitize data input, researching about it found this function.
function clean_data($input){
$input = trim(htmlentities(strip_tags($input,",")));
if (get_magic_quotes_gpc())
$input = stripslashes($input);
$input = mysql_real_escape_string($input);
return $input;
}
example:
$vartodb = clean_data($_POST['yourformfieldhere']);
Its ok this function to sanitize data?
Not really.
If you are going to put the variable in a database, you would be better off using a prepared statement with bound variables. If you cannot use PDO, you can do that as well with mysqli. If you are really stuck with the mysql_* functions, you would only need mysql_real_escape_string.
If you output to the browser, you only need htmlspecialchars.
In short, there is no universal sanitizing function, you need to prepare / escape / encode your data for the medium you are outputting to.
This is a vast topic - this function is ok but there are much better ways to do it.
Check mysqli_real_escape_string: http://php.net/manual/en/mysqli.real-escape-string.php
Don't forget prepared statements: http://php.net/manual/en/pdo.prepared-statements.php
Also, what if your input is of type integer? You should be typecasting.
Also, what if someone adds extra fields to your web form?
While this function does do some sanitisation it is only the tip of the iceberg, like I said it is a vast topic.
In my opinion this is sloppy code that offers little protection.
This question already has answers here:
How can I prevent SQL injection in PHP?
(27 answers)
Closed 9 years ago.
i want to secure my sql queries without pdo or prepare statement
can this function do ?
function sql_escape($string)
{
$string = iconv(mb_detect_encoding($string),'UTF-8//IGNORE',$string);
$string = addslashes($string);
$string = preg_replace('/[\x00-\x1F\x80-\xFF\0xB4\0x60\0x96\0x97\0x95\0x94\0x93\0x92\0x91\0x84\0x82\0x3B\0x8A]/', '', $string);
$string = addslashes($string);
return $string;
}
No, use the supplied escape function. For mysqli this is mysqli_real_escape_string.
Don't reinvent the wheel, especially if it's a very complex wheel and you're not really sure it works in all conditions.
Like many PHP folks you are confusing escaping with protection from injection. So, someday your site will be hacked and you'll come here ready to learn something useful at last.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Best way to prevent SQL injection in PHP?
I have the following function I call when using variables passed from another page. My question is, can I add urlencode information to this and have a single function I use, or is it best to have separate functions for variables I pass information through the address bar vs. a hidden form field?
I am not using PDO, and I typecast when possible.
function checkInput($value) {
// Stripslashes
if (get_magic_quotes_gpc())
// Stripslashes
if (get_magic_quotes_gpc())
{
$value = stripslashes($value);
}
// Quote if not a number
{
$value = "'" . mysql_real_escape_string($value) . "'";
}
return $value;
}
Thank you for your assistance!
Mysqli also supports prepared statements. If mysqli isn't available, there's always systems like PEAR DB that offers prepared statements as well.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Best way to prevent SQL Injection in PHP
php get var clear is it good or not plz help me
function Clear($text)
$Var = str_replace("'", "", $text);
$Var = str_replace('"', '', $Var);
$Var = strip_tags($Var);
$Var = htmlentities($Var);
return $Var;
}
$_GET['Var'] = "1='1'";
$Var = Clear($_GET['Var']);
$Query = "SELECT * FROM TABLE_NAME WHERE COL ='{$Var}'";
echo 'Result : '.($Query);
it is for SQL injection, this is sample code i wrote iam using pdo. if i using mysql_real_escape_string it dose not working.
NO. NO. NO
That is not "safe" from attacks.
At a bare minimum use mysql_real_escape_string (which is designed for this). The first version, mysql_escape_string, was actually flawed which is why the "real" version exists.
However, I recommend placeholders as a more universal (and tidier) solution.
See How can I prevent SQL injection in PHP? (which I am voting to close as a dupe, as well). The answers cover PDO and prepared statements, among other things.
Use prepared statements: http://php.net/manual/ru/pdo.prepared-statements.php