My Codeigniter method for safely deleting database entries - php

Question

I've been searching about deleting db entries in Codeigniter and I finally created a solution that I think is secure. I would really appreciate any feedback! I'm not sure if I'm doing this right..
Advantages:
Uses POST request
ID of entry to be deleted is
validated
Uses CSRF protection (automatically
generated by Codeigniter)
In my example I'm deleting user submitted links (a DB table row contains a link title, link URL, an link description).
HTML: Database entires are contained within a form. Each entry has a form button with the respective link id in the id attribute.
<?php echo form_open('profile/remove_link'); ?>
<?php echo form_hidden('link_id', ''); //value will be populated via jquery ?>
<ul id="user_links">
<?php foreach($query as $row): ?>
<li><?php echo $row->link_title; ?></li>
<li><?php echo auto_link($row->link_url, 'url', TRUE); ?></li>
<li><?php echo $row->link_description; ?></li>
<button type="submit" class="remove" id="<?php echo $row->link_id ?>" value="remove">Remove Link</button>
<?php endforeach; ?>
</ul>
</form>
JQUERY: When user clicks on the remove button, the respective link id is added to the the hidden text input named link_id.
$(document).ready(function(){
$('.remove').click(function() {
var link_to_remove = $(this).attr("id");
$("input[name=link_id]").val(link_to_remove);
});
});
Upon clicking a remove button, it sends the id of link to be removed to controller profile and function remove_link
function remove_link()
{
$this->load->model('Profile_model');
$links_data['query'] = $this->Profile_model->links_read(); //get links from db to add in view
//Validation
$this->form_validation->set_rules('link_id', 'Link ID', 'trim|required|xss_clean|max_length[11]|numeric'); //validate link id
if ($this->form_validation->run() == FALSE) //if validation rules fail
{
$this->load->view('profile/edit_links_view', $links_data);
}
else //success
{
$link_id = $this->input->post('link_id'); //get id of link to be deleted
$seg = 'user_links'; //used to redirect back to user links page
$this->Profile_model->links_delete($link_id, $seg); //send link id to model function
}
}
MODEL
function links_delete($link_id, $seg)
{
$this->db->where('user_id', $this->tank_auth->get_user_id());
$this->db->where('link_id', $link_id);
$this->db->delete('user_links');
redirect("/profile/$seg/");
}

Answer 1

If the ids are unique integers in your database, you could remove these rules:
trim|xss_clean|numeric
And add this one:
is_natural_no_zero
Returns FALSE if the form element contains anything other than a natural number, but not zero: 1, 2, 3, etc.
The numeric rule allows some characters you probably don't want, like decimals and negative. Here's the source (one line):
return (bool)preg_match( '/^[\-+]?[0-9]*\.?[0-9]+$/', $str);
If for some reason you are echo'ing the input back in your HTML output before validating, or are just paranoid, then by all means: xss_clean it up. Otherwise it's not really needed, as I don't think there's any possible method of XSS attacks that only use a number.
Reference:
https://www.owasp.org/index.php/Cross-site_Scripting_%28XSS%29
http://ha.ckers.org/xss.html
Also, you might want to add a LIMIT 1 clause to your query, and definitely make sure to return a value (probably TRUE/FALSE) from your model so you know whether or not the query was successful, so you can give feedback to the user instead of assuming everything went well.

Answer 2

The only thing that I see wrong is that you don't validate who can and can't delete records. That's the only issue you should focus on. Permissions to check if the person sending the request of deletion is allowed to perform such operations. Other than that it's just a matter of preference.

Answer 3

I would suggest rewriting controller and model a bit to make the flow more logical and provide better performance:
controller:
function remove_link()
{
if ($this->input->post('link_id'))
{
//Validation
$this->form_validation->set_rules('link_id', 'Link ID', 'is_natural_no_zero');
if ($this->form_validation->run())
{
$seg = 'user_links'; //do you really need to assign it to variable ??
$this->load->model('Profile_model');
if ($this->Profile_model->links_delete($this->input->post('link_id')) //send link id to model function
{
redirect('/profile/user_links'); // redirect user in controller and only when model returns true
}else{
// inform user about error somehow, eg. by setting session flashdata and redirecting back to /profile/user_links
}
}
} // else statement here was a mistake as in case of form_validation failure nothing happened
$this->load->model('Profile_model');
$links_data['query'] = $this->Profile_model->links_read(); //get links from db to add in view
$this->load->view('profile/edit_links_view', $links_data);
}
model:
function links_delete($link_id)
{
$this->db->where('user_id', $this->tank_auth->get_user_id())
->where('link_id', $link_id)
->delete('user_links'); // you can chain methods without writing always $this->db->
return $this->db->affected_rows(); // returns 1 ( == true) if successfuly deleted
}
And as a side note in your jQuery code I suggest using $('#some_id') instead of $('input[name=XXXX]') - it saves some javascript code execution thus is faster