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      1 // Copyright 2014 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 COMPONENTS_CRX_FILE_CRX_FILE_H_
      6 #define COMPONENTS_CRX_FILE_CRX_FILE_H_
      7 
      8 #include <sys/types.h>
      9 #include "base/basictypes.h"
     10 #include "base/memory/scoped_ptr.h"
     11 
     12 namespace crx_file {
     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 crx_file
     78 
     79 #endif  // COMPONENTS_CRX_FILE_CRX_FILE_H_
     80