Random string generated characters not in original string

Question

I use the following script to generate a temporary password.

before I get a lecture, I AM aware that this isn't crypto secure, and that I should use something like openssl_random_pseudo_bytes. But my question is not regarding 'being secure'.

function generateRandomString($length = 10) {
    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!£$%^&*()?';
    $charactersLength = strlen($characters);
    $randomString = '';
    for ($i = 0; $i < $length; $i++) {
         $randomString .= $characters[rand(0, $charactersLength - 1)];
    }
    return $randomString;
}

I used PHPMailer connected to gmail SMTP to email the password to the user. The problem I have is that when my boss did a demonstration of this whilst in another country, the following characters were sent as the temp pw:

New Password: Il%KÂUyÂ?F

notice the accented A's are not in my string of selectable chars. This has only happened once, however shouldn't happen at all. As a result of this - the relevant hashes didn't match either, and so the temporary password didn't work. I'm using password_hash($string, PASSWORD_DEFAULT) with field length of 255.

Surely the fact that he was in a different country when he tested the function shouldn't have any bearing on the chars sent seeing as they are generated from the server, which obviously has a static location.

$key = generateRandomString();
$msg.="New Password: ".$key."<br><br>";
$mail->Body = $msg;

No, but a charset might depending on how the data was being displayed — Mark Baker
– Mark Baker, Commented Feb 5, 2016 at 11:56
Can you shed more light on this? The data was displayed in an email (ms exchange outlook). I have looked in the actual gmail sentbox, and the chars exist in there, so it must be something between php and the email that did it. — Adam Copley
– Adam Copley, Commented Feb 5, 2016 at 12:07

Asur · Accepted Answer · 2016-02-05 14:06:30Z

2

I have tried it myself and the function works perfectly, so I think your problem is about encoding.

First of all make sure your string is UTF-8 encoded, using

utf8_encode($key);

You can use mb_detect_encoding on $msg and $key to check it just to be sure.
If you still have problems try:

$mail->CharSet = 'UTF-8';

PHPmailer can be a pain with encoding sometimes.
Hope this helps :)

edited Feb 5, 2016 at 14:06

answered Feb 5, 2016 at 12:19

Asur

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1 Comment

Adam Copley Over a year ago

Nice one, thanks very much! I still don't understand why it actually happened, though!

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