PHP用户通过电子邮件验证

I'm working on a php/laravel-4 project, and we need to auto authenticate users coming from the links in the emails we send them, we need to have time limit for links so a link in email would not authenticate after the expire time is passed, I've come to this approach but I have some doubts about it's security:

first I make a md5 hash using user's email, timestamp and a secret key like this:

$timestamp = time();
$hash = md5($email . $timestamp . $secret_key);

then I can generate a url like this:

$url = "http://www.example.com/url?email={$email}&hash={$hash}&timestamp={$timestamp}

so then I can check the timestamp (for time validation) and regenerate the hash and authenticate the user with the provided email, do you think it has any security flaw? if yes please suggest me the secure method.

I would not do that. What I would do:

Create a table for your links:

public function up()
{
    Schema::create('login', function($table) {
        $table->string('id')->primary();

        $table->string('user_id');

        $table->timestamps();
    });
}

Every time you generate a link you add a line to this table:

$user = User::find(1);

$login = Login::create(['id' => Login::generateID(), 'user_id' => $user->id]);

$url = "http://www.example.com/url?login_id={$login->id}"

Then when your user click the link you can automatically log him in, also, immediatelly invalidate that link:

$login = Login::findOrFail(Input::get('login_id'));

$user = User::find($login->user_id);

Auth::login($user);

$login->delete();

And create an Artisan Command to periodiacally delete old records on that table:

Login::where('created_at', '<=', Carbon\Carbon::now()->subDays(2))->delete();

This can be the code for generateID(), it's a basic UUID code generation:

public static function v4() 
{
    return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',

    // 32 bits for "time_low"
    mt_rand(0, 0xffff), mt_rand(0, 0xffff),

    // 16 bits for "time_mid"
    mt_rand(0, 0xffff),

    // 16 bits for "time_hi_and_version",
    // four most significant bits holds version number 4
    mt_rand(0, 0x0fff) | 0x4000,

    // 16 bits, 8 bits for "clk_seq_hi_res",
    // 8 bits for "clk_seq_low",
    // two most significant bits holds zero and one for variant DCE1.1
    mt_rand(0, 0x3fff) | 0x8000,

    // 48 bits for "node"
    mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
    );
}

No strings attached to anything on your system.

As long as the secret key isn't the users password, then this seems fine to me.

You won't find a completely secure way to do this. What if someone's email has been hacked? or a million other situations.

I think your best bet is to send an email containing a username(or email) hashed and possibly a timestamp again. Once they click the link they must enter their password then continue on their way.

You could also include a redirect link in the email link so the script can redirect them to the appropriate place after they enter a password.

md5 is not cryptographically safe, in the sense that it is easy to crack (in cryptographical terms).

The main concern is that md5 is fast, you don't want that, you want it to be as slow as possible, but not so slow that it takes you too long to generate and validate.

Look at the PHP password guide, critical here is the cost parameter. Higher cost means it's more secure. Essentially what cost does is: it increases the amount of times the hash function is applied, more applications means it takes longer to produce and thus brute-force.

Another thing you can do is obfuscate your input. If you can change your URLs to:

$string = $timestamp . "|" . $email . "|" . $hash;
// then encrypt this string
$encrypted = mcrypt_encrypt($cypher, $secret_password_2, $string); // or any other two-way encryption
$url = $base . "?hash=" . $encrypted;

When you receive the hash decrypt it, split it and check the hash. This makes it less obvious what is going on; all 3 values are packed in one encrypted blob.