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      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_
     68