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