net/base/data_url.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_BASE_DATA_URL_H_
   6 #define NET_BASE_DATA_URL_H_
   7
   8 #include <string>
   9
  10 #include "net/base/net_export.h"
  11
  12 class GURL;
  13
  14 namespace net {
  15
  16 // See RFC 2397 for a complete description of the 'data' URL scheme.
  17 //
  18 // Briefly, a 'data' URL has the form:
  19 //
  20 //   data:[<mediatype>][;base64],<data>
  21 //
  22 // The <mediatype> is an Internet media type specification (with optional
  23 // parameters.)  The appearance of ";base64" means that the data is encoded as
  24 // base64.  Without ";base64", the data (as a sequence of octets) is represented
  25 // using ASCII encoding for octets inside the range of safe URL characters and
  26 // using the standard %xx hex encoding of URLs for octets outside that range.
  27 // If <mediatype> is omitted, it defaults to text/plain;charset=US-ASCII.  As a
  28 // shorthand, "text/plain" can be omitted but the charset parameter supplied.
  29 //
  30 class NET_EXPORT DataURL {
  31  public:
  32   // This method can be used to parse a 'data' URL into its component pieces.
  33   //
  34   // The resulting mime_type is normalized to lowercase.  The data is the
  35   // decoded data (e.g.., if the data URL specifies base64 encoding, then the
  36   // returned data is base64 decoded, and any %-escaped bytes are unescaped).
  37   //
  38   // If the media type value doesn't match the media-type production defined in
  39   // RFC 7231, mime_type will be set to the default value "text/plain". We
  40   // don't simply fail for this grammar violation since Chromium had been
  41   // accepting such invalid values. For example, <img> element with the src
  42   // attribute set to a data URL with an invalid media type "image" (without a
  43   // slash and subtype) had been displayed. However, the value this method will
  44   // store in mime_type argument can be used for generating other headers, etc.
  45   // This could lead to security vulnerability. We don't want to accept
  46   // arbitrary value and ask each caller to validate the return value.
  47   //
  48   // If the charset parameter is specified but its value doesn't match the
  49   // token production defined in RFC 7230, this method simply fails and returns
  50   // false.
  51   //
  52   // If there's any other grammar violation in the URL, then this method will
  53   // return false. Output variables may be changed and contain invalid data. On
  54   // success, true is returned.
  55   //
  56   // OPTIONAL: If |data| is NULL, then the <data> section will not be parsed
  57   //           or validated.
  58   //
  59   static bool Parse(const GURL& url,
  60                     std::string* mime_type,
  61                     std::string* charset,
  62                     std::string* data);
  63 };
  64
  65 }  // namespace net
  66
  67 #endif  // NET_BASE_DATA_URL_H_