详谈PHP中的密码安全性Password Hashing

<?php

//require 'password.php';
/**
 * 正确的密码是secret-password
 * $passwordhash 是hash 后存储的密码
 * password_verify()用于将用户输入的密码和数据库存储的密码比对。成功返回true，否则false
 */
$passwordhash = password_hash('secret-password', password_default);
echo $passwordhash;
if (password_verify('bad-password', $passwordhash)) {
  // correct password
  echo 'correct password';
} else {
  echo 'wrong password';
  // wrong password
}

<?php
class user
{
  // store password options so that rehash & hash can share them:
  const hash = password_default;
  const cost = 14;//可以确定该算法应多复杂，进而确定生成哈希值将花费多长时间。（将此值视为更改算法本身重新运行的次数，以减缓计算。）

  // internal data storage about the user:
  public $data;

  // mock constructor:
  public function __construct() {
    // read data from the database, storing it into $data such as:
    // $data->passwordhash and $data->username
    $this->data = new stdclass();
    $this->data->passwordhash = 'dbd014125a4bad51db85f27279f1040a';
  }

  // mock save functionality
  public function save() {
    // store the data from $data back into the database
  }

  // allow for changing a new password:
  public function setpassword($password) {
    $this->data->passwordhash = password_hash($password, self::hash, ['cost' => self::cost]);
  }

  // logic for logging a user in:
  public function login($password) {
    // first see if they gave the right password:
    echo "login: ", $this->data->passwordhash, "\n";
    if (password_verify($password, $this->data->passwordhash)) {
      // success - now see if their password needs rehashed
      if (password_needs_rehash($this->data->passwordhash, self::hash, ['cost' => self::cost])) {
        // we need to rehash the password, and save it. just call setpassword
        $this->setpassword($password);
        $this->save();
      }
      return true; // or do what you need to mark the user as logged in.
    }
    return false;
  }
}