sql injection vulnerability to codeigniter or php

Question

Hello i want to know why this kind of example question never been asked before. i got this code from my college that they say this kind of code is able to prevent sql injection

we use codeigniter to build a website and here is the code to prevent sql injection

Controller

$usr = $this->input->post('userid');
$pwd = $this->input->post('passwd');

if($usr && $pwd) {
                $ack = $this->mAuth->get_user($usr);
$pwx = $ack['passwd'];
                    if($ack && $pwd == $pwx) {
                        //redirect code
}

model

public function get_user($user_id='', $status=1) {
        $user_id = $this->db->escape(trim($user_id));
        $status  = $status ? 'and user_status_uid = 1' : '';

        $sql = "select * from users where user_id = lower($user_id)"

        return rst2Array($sql, 'row');
    }

i tried to login with 1' or 1 = 1 and etc i found and it did prevent sql injection even though it's only a plain text and password.

is there any vulnerability to this code? thanks

If you want to prevent sql-injection never build sql-queries including data via string-concatenation. — Yoshi
– Yoshi, Commented Aug 20, 2014 at 8:12
Check this question: stackoverflow.com/questions/1615792/… — Gerifield
– Gerifield, Commented Aug 20, 2014 at 8:12
this code if($ack && $pwd == $pwx) { //redirect code } it actually prevent injection to login as anyone right? can someone actually have any example? — Gamma
– Gamma, Commented Aug 20, 2014 at 9:44

deceze · Accepted Answer · 2014-08-20 08:43:39Z

1

To put it simply: the "magic" is in the $this->db->escape function. It adds quotes around string values and escapes them properly for SQL syntax. See https://ellislab.com/codeigniter/user-guide/database/queries.html.

Barring any bugs in that function, it indeed prevents SQL injection in this case.

answered Aug 20, 2014 at 8:43

deceze♦

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