Merge pull request #108 in ZP/z-push from feature/ZP-794-safe_put_contents to develop

* commit '50dc9a5c':
  ZP-794 filestatemachine: use Utils::SafePutContents().
  ZP-794 add Utils::SafePutContents().

src/lib/default/filestatemachine.php

@@ -154,7 +154,7 @@ class FileStateMachine implements IStateMachine {
         $state = serialize($state);
 
         $filename = $this->getFullFilePath($devid, $type, $key, $counter);
-        if (($bytes = file_put_contents($filename, $state)) === false)
+        if (($bytes = Utils::SafePutContents($filename, $state)) === false)
             throw new FatalMisconfigurationException(sprintf("FileStateMachine->SetState(): Could not write state '%s'",$filename));
 
         ZLog::Write(LOGLEVEL_DEBUG, sprintf("FileStateMachine->SetState() written %d bytes on file: '%s'", $bytes, $filename));
@@ -233,7 +233,7 @@ class FileStateMachine implements IStateMachine {
             }
 
             if ($changed) {
-                $bytes = file_put_contents($this->userfilename, serialize($users));
+                $bytes = Utils::SafePutContents($this->userfilename, serialize($users));
                 ZLog::Write(LOGLEVEL_DEBUG, sprintf("FileStateMachine->LinkUserDevice(): wrote %d bytes to users file", $bytes));
             }
             else
@@ -282,7 +282,7 @@ class FileStateMachine implements IStateMachine {
             }
 
             if ($changed) {
-                $bytes = file_put_contents($this->userfilename, serialize($users));
+                $bytes = Utils::SafePutContents($this->userfilename, serialize($users));
                 ZLog::Write(LOGLEVEL_DEBUG, sprintf("FileStateMachine->UnLinkUserDevice(): wrote %d bytes to users file", $bytes));
             }
             else
@@ -370,7 +370,7 @@ class FileStateMachine implements IStateMachine {
 
         $settings[self::VERSION] = $version;
         ZLog::Write(LOGLEVEL_INFO, sprintf("FileStateMachine->SetStateVersion() saving supported state version, value '%d'", $version));
-        $status = file_put_contents($this->settingsfilename, serialize($settings));
+        $status = Utils::SafePutContents($this->settingsfilename, serialize($settings));
         Utils::FixFileOwner($this->settingsfilename);
         return $status;
     }

src/lib/utils/utils.php

@@ -929,6 +929,27 @@ class Utils {
         }
         return substr($email, 0, $pos);
     }
+
+    /**
+     * Safely write data to disk, using an unique tmp file (concurrent write),
+     * and using rename for atomicity
+     *
+     * If you use SafePutContents, you can safely use file_get_contents
+     * (you will always read a fully written file)
+     *
+     * @param string $filename
+     * @param string $data
+     * @return boolean|int
+     */
+    public static function SafePutContents($filename, $data) {
+        //put the 'tmp' as a prefix (and not suffix) so all glob call will not see temp files
+        $tmp = dirname($filename).DIRECTORY_SEPARATOR.'tmp-'.getmypid().'-'.basename($filename);
+        if (($res = file_put_contents($tmp, $data)) !== false)
+            if (rename($tmp, $filename) !== true)
+                $res = false;
+
+        return $res;
+    }
 }