Json::encode(): auto-sanitize bad UTF-8 strings

refs #2635

library/Icinga/Util/Json.php

@@ -28,10 +28,17 @@ class Json
         } else {
             $encoded = json_encode($value, $options, $depth);
         }
-        if (json_last_error() !== JSON_ERROR_NONE) {
-            throw new JsonEncodeException('%s: %s', static::lastErrorMsg(), var_export($value, true));
+
+        switch (json_last_error()) {
+            case JSON_ERROR_NONE:
+                return $encoded;
+
+            case JSON_ERROR_UTF8:
+                return static::encode(static::sanitizeUtf8Recursive($value), $options, $depth);
+
+            default:
+                throw new JsonEncodeException('%s: %s', static::lastErrorMsg(), var_export($value, true));
         }
-        return $encoded;
     }
 
     /**
@@ -82,4 +89,60 @@ class Json
                 return 'Unknown error';
         }
     }
+
+    /**
+     * Replace bad byte sequences in UTF-8 strings inside the given JSON-encodable structure with question marks
+     *
+     * @param   mixed   $value
+     *
+     * @return  mixed
+     */
+    protected static function sanitizeUtf8Recursive($value)
+    {
+        switch (gettype($value)) {
+            case 'string':
+                return static::sanitizeUtf8String($value);
+
+            case 'array':
+                $sanitized = array();
+
+                foreach ($value as $key => $val) {
+                    if (is_string($key)) {
+                        $key = static::sanitizeUtf8String($key);
+                    }
+
+                    $sanitized[$key] = static::sanitizeUtf8Recursive($val);
+                }
+
+                return $sanitized;
+
+            case 'object':
+                $sanitized = array();
+
+                foreach ($value as $key => $val) {
+                    if (is_string($key)) {
+                        $key = static::sanitizeUtf8String($key);
+                    }
+
+                    $sanitized[$key] = static::sanitizeUtf8Recursive($val);
+                }
+
+                return (object) $sanitized;
+
+            default:
+                return $value;
+        }
+    }
+
+    /**
+     * Replace bad byte sequences in the given UTF-8 string with question marks
+     *
+     * @param   string  $string
+     *
+     * @return  string
+     */
+    protected static function sanitizeUtf8String($string)
+    {
+        return mb_convert_encoding($string, 'UTF-8', 'UTF-8');
+    }
 }