From 4d2628e8aab6d0673ac0a010acbfaa9d76b7d568 Mon Sep 17 00:00:00 2001
From: Andrey Andreev <narf@devilix.net>
Date: Tue, 22 Mar 2016 13:42:03 +0200
Subject: random_bytes()-related improvements

See #4260
---
 system/core/compat/password.php     | 26 ++++++++++++++++++++++----
 system/libraries/Encryption.php     | 26 ++++++++++++++++++++------
 user_guide_src/source/changelog.rst |  7 +++++++
 3 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/system/core/compat/password.php b/system/core/compat/password.php
index f0c22c780..76dd2cf0a 100644
--- a/system/core/compat/password.php
+++ b/system/core/compat/password.php
@@ -116,13 +116,21 @@ if ( ! function_exists('password_hash'))
 		}
 		elseif ( ! isset($options['salt']))
 		{
-			if (defined('MCRYPT_DEV_URANDOM'))
+			if (function_exists('random_bytes'))
 			{
-				$options['salt'] = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);
+				try
+				{
+					$options['salt'] = random_bytes(16);
+				}
+				catch (Exception $e)
+				{
+					log_message('error', 'compat/password: Error while trying to use random_bytes(): '.$e->getMessage());
+					return FALSE;
+				}
 			}
-			elseif (function_exists('openssl_random_pseudo_bytes'))
+			elseif (defined('MCRYPT_DEV_URANDOM'))
 			{
-				$options['salt'] = openssl_random_pseudo_bytes(16);
+				$options['salt'] = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);
 			}
 			elseif (DIRECTORY_SEPARATOR === '/' && (is_readable($dev = '/dev/arandom') OR is_readable($dev = '/dev/urandom')))
 			{
@@ -148,6 +156,16 @@ if ( ! function_exists('password_hash'))
 
 				fclose($fp);
 			}
+			elseif (function_exists('openssl_random_pseudo_bytes'))
+			{
+				$is_secure = NULL;
+				$options['salt'] = openssl_random_pseudo_bytes(16, $is_secure);
+				if ($is_secure !== TRUE)
+				{
+					log_message('error', 'compat/password: openssl_random_pseudo_bytes() set the $cryto_strong flag to FALSE');
+					return FALSE;
+				}
+			}
 			else
 			{
 				log_message('error', 'compat/password: No CSPRNG available.');
diff --git a/system/libraries/Encryption.php b/system/libraries/Encryption.php
index 92c38a0ed..a10a5c20c 100644
--- a/system/libraries/Encryption.php
+++ b/system/libraries/Encryption.php
@@ -339,12 +339,26 @@ class CI_Encryption {
 	{
 		if (function_exists('random_bytes'))
 		{
-			return random_bytes((int) $length);
+			try
+			{
+				return random_bytes((int) $length);
+			}
+			catch (Exception $e)
+			{
+				log_message('error', $e->getMessage());
+				return FALSE;
+			}
+		}
+		elseif (defined('MCRYPT_DEV_URANDOM'))
+		{
+			return mcrypt_create_iv($length, MCRYPT_DEV_URANDOM);
 		}
 
-		return ($this->_driver === 'mcrypt')
-			? mcrypt_create_iv($length, MCRYPT_DEV_URANDOM)
-			: openssl_random_pseudo_bytes($length);
+		$is_secure = NULL;
+		$key = openssl_random_pseudo_bytes($length, $is_secure);
+		return ($is_secure === TRUE)
+			? $key
+			: FALSE;
 	}
 
 	// --------------------------------------------------------------------
@@ -400,7 +414,7 @@ class CI_Encryption {
 		// The greater-than-1 comparison is mostly a work-around for a bug,
 		// where 1 is returned for ARCFour instead of 0.
 		$iv = (($iv_size = mcrypt_enc_get_iv_size($params['handle'])) > 1)
-			? mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM)
+			? $this->create_key($iv_size)
 			: NULL;
 
 		if (mcrypt_generic_init($params['handle'], $params['key'], $iv) < 0)
@@ -463,7 +477,7 @@ class CI_Encryption {
 		}
 
 		$iv = ($iv_size = openssl_cipher_iv_length($params['handle']))
-			? openssl_random_pseudo_bytes($iv_size)
+			? $this->create_key($iv_size)
 			: NULL;
 
 		$data = openssl_encrypt(
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 88b797b91..5732ed3c6 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -10,6 +10,13 @@ Release Date: Not Released
 -  General Changes
 
    -  Updated :doc:`Image Manipulation Library <libraries/image_lib>` to validate *width* and *height* configuration values.
+   -  Updated :doc:`Encryption Library <libraries/encryption>` to always prefer ``random_bytes()`` when it is available.
+
+   -  :php:func:`password_hash()` :doc:`compatibility function <general/compatibility_functions>` changes:
+
+      - Changed salt-generation logic to prefer ``random_bytes()`` when it is available.
+      - Changed salt-generation logic to prefer direct access to */dev/urandom* over ``openssl_random_pseudo_bytes()``.
+      - Changed salt-generation logic to error if ``openssl_random_pseudo_bytes()`` sets its ``$crypto_strong`` flag to FALSE.
 
 Bug fixes for 3.0.7
 -------------------
-- 
cgit v1.2.3-24-g4f1b