Fix #2822: Incorrect usage of fwrite()

We only used to check (and not always) if the return value of fwrite() is boolean FALSE,
while it is possible that the otherwise returned bytecount is less than the length of
data that we're trying to write. This allowed incomplete writes over network streams
and possibly a few other edge cases.

6 files changed, 80 insertions, 21 deletions

diff --git a/system/core/Log.php b/system/core/Log.php
index ff3c63568..63fef2088 100644
--- a/system/core/Log.php
+++ b/system/core/Log.php
@@ -178,7 +178,15 @@ class CI_Log {
 		$message .= $level.' - '.date($this->_date_fmt).' --> '.$msg."\n";
 
 		flock($fp, LOCK_EX);
-		fwrite($fp, $message);
+
+		for ($written = 0, $length = strlen($message); $written < $length; $written += $result)
+		{
+			if (($result = fwrite($fp, substr($message, $written))) === FALSE)
+			{
+				break;
+			}
+		}
+
 		flock($fp, LOCK_UN);
 		fclose($fp);
 
@@ -187,7 +195,7 @@ class CI_Log {
 			@chmod($filepath, FILE_WRITE_MODE);
 		}
 
-		return TRUE;
+		return is_int($result);
 	}
 
 }
diff --git a/system/core/Output.php b/system/core/Output.php
index 10332f0d8..a7680b3d0 100644
--- a/system/core/Output.php
+++ b/system/core/Output.php
@@ -542,17 +542,26 @@ class CI_Output {
 			return;
 		}
 
-		$expire = time() + ($this->cache_expiration * 60);
-
-		// Put together our serialized info.
-		$cache_info = serialize(array(
-			'expire'	=> $expire,
-			'headers'	=> $this->headers
-		));
-
 		if (flock($fp, LOCK_EX))
 		{
-			fwrite($fp, $cache_info.'ENDCI--->'.$output);
+			$expire = time() + ($this->cache_expiration * 60);
+
+			// Put together our serialized info.
+			$cache_info = serialize(array(
+				'expire'	=> $expire,
+				'headers'	=> $this->headers
+			));
+
+			$output = $cache_info.'ENDCI--->'.$output;
+
+			for ($written = 0, $length = strlen($output); $written < $length; $written += $result)
+			{
+				if (($result = fwrite($fp, substr($output, $written))) === FALSE)
+				{
+					break;
+				}
+			}
+
 			flock($fp, LOCK_UN);
 		}
 		else
@@ -560,13 +569,22 @@ class CI_Output {
 			log_message('error', 'Unable to secure a file lock for file at: '.$cache_path);
 			return;
 		}
+
 		fclose($fp);
-		@chmod($cache_path, FILE_WRITE_MODE);
 
-		log_message('debug', 'Cache file written: '.$cache_path);
+		if (is_int($result))
+		{
+			@chmod($cache_path, FILE_WRITE_MODE);
+			log_message('debug', 'Cache file written: '.$cache_path);
 
-		// Send HTTP cache-control headers to browser to match file cache settings.
-		$this->set_cache_header($_SERVER['REQUEST_TIME'], $expire);
+			// Send HTTP cache-control headers to browser to match file cache settings.
+			$this->set_cache_header($_SERVER['REQUEST_TIME'], $expire);
+		}
+		else
+		{
+			@unlink($cache_path);
+			log_message('error', 'Unable to write the complete cache content at: '.$cache_path);
+		}
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/helpers/file_helper.php b/system/helpers/file_helper.php
index 4b45a62d0..0587740b1 100644
--- a/system/helpers/file_helper.php
+++ b/system/helpers/file_helper.php
@@ -79,11 +79,19 @@ if ( ! function_exists('write_file'))
 		}
 
 		flock($fp, LOCK_EX);
-		fwrite($fp, $data);
+
+		for ($written = 0, $length = strlen($data); $written < $length; $written += $result)
+		{
+			if (($result = fwrite($fp, substr($data, $written))) === FALSE)
+			{
+				break;
+			}
+		}
+
 		flock($fp, LOCK_UN);
 		fclose($fp);
 
-		return TRUE;
+		return is_int($result);
 	}
 }
 
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 9487ad486..f4efff882 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -2097,7 +2097,16 @@ class CI_Email {
 	 */
 	protected function _send_data($data)
 	{
-		if (fwrite($this->_smtp_connect, $data.$this->newline) === FALSE)
+		$data .= $this->newline;
+		for ($written = 0, $length = strlen($data); $written < $length; $written += $result)
+		{
+			if (($result = fwrite($this->_smtp_connect, substr($data, $written))) === FALSE)
+			{
+				break;
+			}
+		}
+
+		if ($result === FALSE)
 		{
 			$this->_set_error_message('lang:email_smtp_data_failure', $data);
 			return FALSE;
diff --git a/system/libraries/Xmlrpc.php b/system/libraries/Xmlrpc.php
index 1f93e6981..ab907e706 100644
--- a/system/libraries/Xmlrpc.php
+++ b/system/libraries/Xmlrpc.php
@@ -724,7 +724,15 @@ class XML_RPC_Client extends CI_Xmlrpc
 			.'Content-Length: '.strlen($msg->payload).$r.$r
 			.$msg->payload;
 
-		if (fwrite($fp, $op, strlen($op)) === FALSE)
+		for ($written = 0, $length = strlen($op); $written < $length; $written += $result)
+		{
+			if (($result = fwrite($fp, substr($op, $written))) === FALSE)
+			{
+				break;
+			}
+		}
+
+		if ($result === FALSE)
 		{
 			error_log($this->xmlrpcstr['http_error']);
 			return new XML_RPC_Response(0, $this->xmlrpcerr['http_error'], $this->xmlrpcstr['http_error']);
diff --git a/system/libraries/Zip.php b/system/libraries/Zip.php
index 250ee02cd..b10b0bb0f 100644
--- a/system/libraries/Zip.php
+++ b/system/libraries/Zip.php
@@ -403,11 +403,19 @@ class CI_Zip {
 		}
 
 		flock($fp, LOCK_EX);
-		fwrite($fp, $this->get_zip());
+
+		for ($written = 0, $data = $this->get_zip(), $length = strlen($data); $written < $length; $written += $result)
+		{
+			if (($result = fwrite($fp, substr($data, $written))) === FALSE)
+			{
+				break;
+			}
+		}
+
 		flock($fp, LOCK_UN);
 		fclose($fp);
 
-		return TRUE;
+		return is_int($result);
 	}
 
 	// --------------------------------------------------------------------