Merge branch '3.1-stable' into develop

Resolved conflicts:
	system/core/CodeIgniter.php
	user_guide_src/source/changelog.rst
	user_guide_src/source/conf.py
	user_guide_src/source/installation/downloads.rst
	user_guide_src/source/installation/upgrading.rst
	user_guide_src/source/libraries/form_validation.rst

2 files changed, 119 insertions, 8 deletions

diff --git a/system/libraries/Session/Session.php b/system/libraries/Session/Session.php
index 3b391a8ef..01989d2d7 100644
--- a/system/libraries/Session/Session.php
+++ b/system/libraries/Session/Session.php
@@ -57,6 +57,7 @@ class CI_Session {
 
 	protected $_driver = 'files';
 	protected $_config;
+	protected $_sid_regexp;
 
 	// ------------------------------------------------------------------------
 
@@ -99,6 +100,7 @@ class CI_Session {
 
 		// Configuration ...
 		$this->_configure($params);
+		$this->_config['_sid_regexp'] = $this->_sid_regexp;
 
 		$class = new $class($this->_config);
 		if ($class instanceof SessionHandlerInterface)
@@ -131,7 +133,7 @@ class CI_Session {
 		if (isset($_COOKIE[$this->_config['cookie_name']])
 			&& (
 				! is_string($_COOKIE[$this->_config['cookie_name']])
-				OR ! preg_match('/^[0-9a-f]{40}$/', $_COOKIE[$this->_config['cookie_name']])
+				OR ! preg_match('#\A'.$this->_sid_regexp.'\z#', $_COOKIE[$this->_config['cookie_name']])
 			)
 		)
 		{
@@ -315,8 +317,82 @@ class CI_Session {
 		ini_set('session.use_strict_mode', 1);
 		ini_set('session.use_cookies', 1);
 		ini_set('session.use_only_cookies', 1);
-		ini_set('session.hash_function', 1);
-		ini_set('session.hash_bits_per_character', 4);
+
+		$this->_configure_sid_length();
+	}
+
+	// ------------------------------------------------------------------------
+
+	/**
+	 * Configure session ID length
+	 *
+	 * To make life easier, we used to force SHA-1 and 4 bits per
+	 * character on everyone. And of course, someone was unhappy.
+	 *
+	 * Then PHP 7.1 broke backwards-compatibility because ext/session
+	 * is such a mess that nobody wants to touch it with a pole stick,
+	 * and the one guy who does, nobody has the energy to argue with.
+	 *
+	 * So we were forced to make changes, and OF COURSE something was
+	 * going to break and now we have this pile of shit. -- Narf
+	 *
+	 * @return	void
+	 */
+	protected function _configure_sid_length()
+	{
+		if (PHP_VERSION_ID < 70100)
+		{
+			$hash_function = ini_get('session.hash_function');
+			if (ctype_digit($hash_function))
+			{
+				if ($hash_function !== '1')
+				{
+					ini_set('session.hash_function', 1);
+				}
+
+				$bits = 160;
+			}
+			elseif ( ! in_array($hash_function, hash_algos(), TRUE))
+			{
+				ini_set('session.hash_function', 1);
+				$bits = 160;
+			}
+			elseif (($bits = strlen(hash($hash_function, 'dummy', false)) * 4) < 160)
+			{
+				ini_set('session.hash_function', 1);
+				$bits = 160;
+			}
+
+			$bits_per_character = (int) ini_get('session.hash_bits_per_character');
+			$sid_length         = (int) ceil($bits / $bits_per_character);
+		}
+		else
+		{
+			$bits_per_character = (int) ini_get('session.sid_bits_per_character');
+			$sid_length         = (int) ini_get('session.sid_length');
+			if (($bits = $sid_length * $bits_per_character) < 160)
+			{
+				// Add as many more characters as necessary to reach at least 160 bits
+				$sid_length += (int) ceil((160 % $bits) / $bits_per_character);
+				ini_set('session.sid_length', $sid_length);
+			}
+		}
+
+		// Yes, 4,5,6 are the only known possible values as of 2016-10-27
+		switch ($bits_per_character)
+		{
+			case 4:
+				$this->_sid_regexp = '[0-9a-f]';
+				break;
+			case 5:
+				$this->_sid_regexp = '[0-9a-v]';
+				break;
+			case 6:
+				$this->_sid_regexp = '[0-9a-zA-Z,-]';
+				break;
+		}
+
+		$this->_sid_regexp .= '{'.$sid_length.'}';
 	}
 
 	// ------------------------------------------------------------------------
diff --git a/system/libraries/Session/drivers/Session_files_driver.php b/system/libraries/Session/drivers/Session_files_driver.php
index bf4df8b20..37315d3cd 100644
--- a/system/libraries/Session/drivers/Session_files_driver.php
+++ b/system/libraries/Session/drivers/Session_files_driver.php
@@ -76,6 +76,20 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 */
 	protected $_file_new;
 
+	/**
+	 * Validate SID regular expression
+	 *
+	 * @var	string
+	 */
+	protected $_sid_regexp;
+
+	/**
+	 * mbstring.func_override flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_override;
+
 	// ------------------------------------------------------------------------
 
 	/**
@@ -98,6 +112,10 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 			log_message('debug', 'Session: "sess_save_path" is empty; using "session.save_path" value from php.ini.');
 			$this->_config['save_path'] = rtrim(ini_get('session.save_path'), '/\\');
 		}
+
+		$this->_sid_regexp = $this->_config['_sid_regexp'];
+
+		isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));
 	}
 
 	// ------------------------------------------------------------------------
@@ -187,7 +205,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 		}
 
 		$session_data = '';
-		for ($read = 0, $length = filesize($this->_file_path.$session_id); $read < $length; $read += strlen($buffer))
+		for ($read = 0, $length = filesize($this->_file_path.$session_id); $read < $length; $read += self::strlen($buffer))
 		{
 			if (($buffer = fread($this->_file_handle, $length - $read)) === FALSE)
 			{
@@ -343,10 +361,13 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 
 		$ts = time() - $maxlifetime;
 
+		$pattern = ($this->_config['match_ip'] === TRUE)
+			? '[0-9a-f]{32}'
+			: '';
+
 		$pattern = sprintf(
-			'/^%s[0-9a-f]{%d}$/',
-			preg_quote($this->_config['cookie_name'], '/'),
-			($this->_config['match_ip'] === TRUE ? 72 : 40)
+			'#\A%s'.$pattern.$this->_sid_regexp.'\z#',
+			preg_quote($this->_config['cookie_name'])
 		);
 
 		while (($file = readdir($directory)) !== FALSE)
@@ -368,4 +389,18 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 		return $this->_success;
 	}
 
-}
\ No newline at end of file
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_override)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+}