library/authentication/password_hashing.php

   1 <?php
   2 /**
   3  * Hashing and salt generation algorithms for use in password management.
   4  *
   5  * <pre>
   6  * These are the algorithms used for password hashing, including generation of salt and selection
   7  * of a hashing algorithm.  crypt() with blowfish will be used on systems that support it.
   8  * If blowfish is not available, then SHA1 with a prepended salt will be used.
   9  *
  10  * When a system without blowfish (e.g. PHP 5.2) is upgraded to one with support (e.g. php 5.3),
  11  * the passwords will continue to be stored and useable in SHA1 format until a user either changes
  12  * his own password, or an administrator issues a new password.
  13  * </pre>
  14  * Copyright (C) 2013 Kevin Yeh <kevin.y@integralemr.com> and OEMR <www.oemr.org>
  15  *
  16  * LICENSE: This program is free software; you can redistribute it and/or
  17  * modify it under the terms of the GNU General Public License
  18  * as published by the Free Software Foundation; either version 3
  19  * of the License, or (at your option) any later version.
  20  * This program is distributed in the hope that it will be useful,
  21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  23  * GNU General Public License for more details.
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program. If not, see <http://opensource.org/licenses/gpl-license.php>;.
  26  *
  27  * @package OpenEMR
  28  * @author  Kevin Yeh <kevin.y@integralemr.com>
  29  * @link    http://www.open-emr.org
  30  */
  31
  32 define("SALT_PREFIX_SHA1", '$SHA1$');
  33
  34 /**
  35  *
  36  * Generate a salt to be used with the password_hash() function.
  37  *
  38  * <pre>
  39  * This function checks for the availability of the preferred hashing algorithm (BLOWFISH)
  40  * on the system.  If it is available the salt returned is prefixed to indicate it is for BLOWFISH.
  41  * If it is not available, then SHA1 will be used instead.
  42  *
  43  * See php documentation on crypt() for more details.
  44  * </pre>
  45  *
  46  *
  47  * @return type     The algorithm prefix + random data for salt.
  48  */
  49 function oemr_password_salt()
  50 {
  51     $Allowed_Chars ='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./';
  52     $Chars_Len = 63;
  53
  54     $Salt_Length = 22;
  55
  56     $salt = "";
  57
  58     for ($i=0; $i<$Salt_Length; $i++) {
  59         $salt .= $Allowed_Chars[mt_rand(0, $Chars_Len)];
  60     }
  61
  62     // This is the preferred hashing mechanism
  63     if (CRYPT_BLOWFISH===1) {
  64         $rounds='05';
  65         //This string tells crypt to apply blowfish $rounds times.
  66         $Blowfish_Pre = '$2a$'.$rounds.'$';
  67         $Blowfish_End = '$';
  68
  69         return $Blowfish_Pre.$salt.$Blowfish_End;
  70     }
  71
  72     error_log("Blowfish hashing algorithm not available.  Upgrading to PHP 5.3.x or newer is strongly recommended");
  73
  74     return SALT_PREFIX_SHA1.$salt;
  75 }
  76
  77 /**
  78  * Hash a plaintext password for comparison or initial storage.
  79  *
  80  * <pre>
  81  * This function either uses the built in PHP crypt() function, or sha1() depending
  82  * on a prefix in the salt.  This on systems without a strong enough built in algorithm
  83  * for crypt(), sha1() can be used as a fallback.
  84  * If the crypt function returns an error or illegal hash, then will die.
  85  * </pre>
  86  *
  87  * @param type $plaintext
  88  * @param type $salt
  89  * @return type
  90  */
  91 function oemr_password_hash($plaintext, $salt)
  92 {
  93     // if this is a SHA1 salt, the use prepended salt
  94     if (strpos($salt, SALT_PREFIX_SHA1)===0) {
  95         return SALT_PREFIX_SHA1 . sha1($salt.$plaintext);
  96     } else { // Otherwise use PHP crypt()
  97         $crypt_return = crypt($plaintext, $salt);
  98         if (($crypt_return == '*0') || ($crypt_return == '*1') || (strlen($crypt_return) < 6)) {
  99             // Error code returned by crypt or not hash, so die
 100             error_log("FATAL ERROR: crypt() function is not working correctly in OpenEMR");
 101             die("FATAL ERROR: crypt() function is not working correctly in OpenEMR");
 102         } else {
 103             // Hash confirmed, so return the hash.
 104             return $crypt_return;
 105         }
 106     }
 107 }