1. Advertising
    y u no do it?

    Advertising (learn more)

    Advertise virtually anything here, with CPM banner ads, CPM email ads and CPC contextual links. You can target relevant areas of the site and show ads based on geographical location of the user if you wish.

    Starts at just $1 per CPM or $0.10 per CPC.

Need PHP Function to avoid XSS and SQL injection attack

Discussion in 'PHP' started by techbongo, May 9, 2010.

  1. #1
    Hi folks,
    SEMrush
    This time I'm in some trouble. Please help me in this issue.

    My site will have forms with number of text fields, I'll store the form data in MySQL database and later those data will be fetched and populated on web pages. Now, the forms are filled up by users, so I need to escape all unwanted characters while keeping the necessary ones intact.

    Suppose I get a field data in the form of $_POST['field_name']. So far I was using combination of mysql_real_escape_string, htmlentities, striptags and htmlencode functions. But I guess, I'm not using them properly one after another.

    Can you please give me the exact function set for:
    1. Inserting data into database
    2. Fetching data and populating into database

    Like:
    function1(function2(function3($_POST['field_name']))) while inserting and
    functionX(functionY(functionZ($row['column_name']))) while showing them on webpage.

    Please describe, what specifically the functions are doing, so that I can keep the required special characters (like some html tags for a rich text input field) intact.
     
    techbongo, May 9, 2010 IP
    SEMrush
  2. danx10

    danx10 Peon

    Messages:
    1,179
    Likes Received:
    44
    Best Answers:
    2
    Trophy Points:
    0
    #2
    heres my little function:
    
    function clean($input) {
    //remove whitespace...
    $input = trim($input);
    //disable magic quotes...
    $input = get_magic_quotes_gpc() ? stripslashes($input) : $input;
    //prevent sql injection...
    $input = is_numeric($input) ? intval($input) : mysql_real_escape_string($input);
    //prevent xss...
    $input = htmlspecialchars($input);
    return $input;
    }
    PHP:
    Example usage:

    //apply the function to an array of user submitted data...
    $_POST = array_map('clean', $_POST);
    
    //or individually like...
    $message = clean($_POST['message']);
    
    PHP:
     
    danx10, May 9, 2010 IP
    belgin fish likes this.
  3. techbongo

    techbongo Active Member

    Messages:
    309
    Likes Received:
    3
    Best Answers:
    0
    Trophy Points:
    80
    #3
    Wow!
    This one charmed me. Can you tell me, if it'll strip html tags also? If no, then how can I strip them?
    Again,
    If the input to the text field is

    <b>Hello world</b>

    How can I store it in database and while displaying them on page, how can I show it intact (ie. <b>Hello world</b>) instead of like this Hello wolrd
     
    techbongo, May 9, 2010 IP
  4. ceaseer

    ceaseer Peon

    Messages:
    473
    Likes Received:
    10
    Best Answers:
    0
    Trophy Points:
    0
    #4
    Here is a simple str_replace function. You can add to the array anything you do not want to be inputed.

    $banned=array("<", ">", "-", "'", "/", "[", "^", "]", "+", "{", "}", "$", "%", "(", ")", "&", "#", ";", "bad words");
    FunctionXYZ(str_replace($banned,"",$_POST["field_name"]));
     
    ceaseer, May 9, 2010 IP
  5. danx10

    danx10 Peon

    Messages:
    1,179
    Likes Received:
    44
    Best Answers:
    2
    Trophy Points:
    0
    #5
    Thats one of the functionalities of the function :), it doesnt strip html it just doesn't execute it, it will print it instead - this will prevent xss.
     
    danx10, May 9, 2010 IP
  6. zac439

    zac439 Notable Member

    Messages:
    3,074
    Likes Received:
    214
    Best Answers:
    0
    Trophy Points:
    260
    #6
    It's better to escape the characters, rather than delete them.
    If you needed to store the value "Jean-Luc Piccard" in a name field, the name would be "JeanLuc Piccard" -- this isn't acceptable.


    1. How do you know it was an SQL injection?
    2. How are you using mysql_real_escape_string?

    Post code and we can solve the real problem. mysql_real_escape_string will block all SQL injection attacks if properly used.
     
    zac439, May 9, 2010 IP
  7. sojic

    sojic Active Member

    Messages:
    133
    Likes Received:
    3
    Best Answers:
    0
    Trophy Points:
    90
    #7
    PHP Framworks (cakephp, CodeIgniter, Zend) have implemented such filters, so, if you are using php frameworks, you can relax add do not think about it
     
    sojic, May 23, 2011 IP
  8. Gray Fox

    Gray Fox Peon

    Messages:
    196
    Likes Received:
    8
    Best Answers:
    0
    Trophy Points:
    0
    #8
    The trick isn't to filter input, but to escape output.
     
    Gray Fox, May 23, 2011 IP