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
12namespace 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.
17class 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_
81