extensions/common/crx_file.h

   1 // Copyright (c) 2012 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 EXTENSIONS_COMMON_CRX_FILE_H_
   6 #define EXTENSIONS_COMMON_CRX_FILE_H_
   7
   8 #include <sys/types.h>
   9 #include "base/basictypes.h"
  10 #include "base/memory/scoped_ptr.h"
  11
  12 namespace extensions {
  13
  14 // CRX files have a header that includes a magic key, version number, and
  15 // some signature sizing information. Use CrxFile object to validate whether
  16 // the header is valid or not.
  17 class CrxFile {
  18  public:
  19
  20   // The size of the magic character sequence at the beginning of each crx
  21   // file, in bytes. This should be a multiple of 4.
  22   static const size_t kCrxFileHeaderMagicSize = 4;
  23
  24   // This header is the first data at the beginning of an extension. Its
  25   // contents are purposely 32-bit aligned so that it can just be slurped into
  26   // a struct without manual parsing.
  27   struct Header {
  28     char magic[kCrxFileHeaderMagicSize];
  29     uint32 version;
  30     uint32 key_size;  // The size of the public key, in bytes.
  31     uint32 signature_size;  // The size of the signature, in bytes.
  32     // An ASN.1-encoded PublicKeyInfo structure follows.
  33     // The signature follows.
  34   };
  35
  36   enum Error {
  37     kWrongMagic,
  38     kInvalidVersion,
  39     kInvalidKeyTooLarge,
  40     kInvalidKeyTooSmall,
  41     kInvalidSignatureTooLarge,
  42     kInvalidSignatureTooSmall,
  43   };
  44
  45   // Construct a new CRX file header object with bytes of a header
  46   // read from a CRX file. If a null scoped_ptr is returned, |error|
  47   // contains an error code with additional information.
  48   static scoped_ptr<CrxFile> Parse(const Header& header, Error* error);
  49
  50   // Construct a new header for the given key and signature sizes.
  51   // Returns a null scoped_ptr if erroneous values of |key_size| and/or
  52   // |signature_size| are provided. |error| contains an error code with
  53   // additional information.
  54   // Use this constructor and then .header() to obtain the Header
  55   // for writing out to a CRX file.
  56   static scoped_ptr<CrxFile> Create(const uint32 key_size,
  57                                     const uint32 signature_size,
  58                                     Error* error);
  59
  60   // Returns the header structure for writing out to a CRX file.
  61   const Header& header() const { return header_; }
  62
  63   // Checks a valid |header| to determine whether or not the CRX represents a
  64   // differential CRX.
  65   static bool HeaderIsDelta(const Header& header);
  66
  67  private:
  68   Header header_;
  69
  70   // Constructor is private. Clients should use static factory methods above.
  71   explicit CrxFile(const Header& header);
  72
  73   // Checks the |header| for validity and returns true if the values are valid.
  74   // If false is returned, more detailed error code is returned in |error|.
  75   static bool HeaderIsValid(const Header& header, Error* error);
  76 };
  77
  78 }  // namespace extensions
  79
  80 #endif  // EXTENSIONS_COMMON_CRX_FILE_H_