components/crx_file/crx_file.h

   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 <string>
   9 #include <vector>
  10
  11 #include <sys/types.h>
  12 #include "base/basictypes.h"
  13 #include "base/memory/scoped_ptr.h"
  14
  15 namespace base {
  16 class FilePath;
  17 }
  18
  19 namespace crx_file {
  20
  21 // CRX files have a header that includes a magic key, version number, and
  22 // some signature sizing information. Use CrxFile object to validate whether
  23 // the header is valid or not.
  24 class CrxFile {
  25  public:
  26   // The size of the magic character sequence at the beginning of each crx
  27   // file, in bytes. This should be a multiple of 4.
  28   static const size_t kCrxFileHeaderMagicSize = 4;
  29
  30   // This header is the first data at the beginning of an extension. Its
  31   // contents are purposely 32-bit aligned so that it can just be slurped into
  32   // a struct without manual parsing.
  33   struct Header {
  34     char magic[kCrxFileHeaderMagicSize];
  35     uint32 version;
  36     uint32 key_size;  // The size of the public key, in bytes.
  37     uint32 signature_size;  // The size of the signature, in bytes.
  38     // An ASN.1-encoded PublicKeyInfo structure follows.
  39     // The signature follows.
  40   };
  41
  42   enum Error {
  43     kWrongMagic,
  44     kInvalidVersion,
  45     kInvalidKeyTooLarge,
  46     kInvalidKeyTooSmall,
  47     kInvalidSignatureTooLarge,
  48     kInvalidSignatureTooSmall,
  49   };
  50
  51   // Construct a new CRX file header object with bytes of a header
  52   // read from a CRX file. If a null scoped_ptr is returned, |error|
  53   // contains an error code with additional information.
  54   static scoped_ptr<CrxFile> Parse(const Header& header, Error* error);
  55
  56   // Construct a new header for the given key and signature sizes.
  57   // Returns a null scoped_ptr if erroneous values of |key_size| and/or
  58   // |signature_size| are provided. |error| contains an error code with
  59   // additional information.
  60   // Use this constructor and then .header() to obtain the Header
  61   // for writing out to a CRX file.
  62   static scoped_ptr<CrxFile> Create(const uint32 key_size,
  63                                     const uint32 signature_size,
  64                                     Error* error);
  65
  66   // Returns the header structure for writing out to a CRX file.
  67   const Header& header() const { return header_; }
  68
  69   // Checks a valid |header| to determine whether or not the CRX represents a
  70   // differential CRX.
  71   static bool HeaderIsDelta(const Header& header);
  72
  73   enum class ValidateError {
  74     NONE,
  75     CRX_FILE_NOT_READABLE,
  76     CRX_HEADER_INVALID,
  77     CRX_MAGIC_NUMBER_INVALID,
  78     CRX_VERSION_NUMBER_INVALID,
  79     CRX_EXCESSIVELY_LARGE_KEY_OR_SIGNATURE,
  80     CRX_ZERO_KEY_LENGTH,
  81     CRX_ZERO_SIGNATURE_LENGTH,
  82     CRX_PUBLIC_KEY_INVALID,
  83     CRX_SIGNATURE_INVALID,
  84     CRX_SIGNATURE_VERIFICATION_INITIALIZATION_FAILED,
  85     CRX_SIGNATURE_VERIFICATION_FAILED,
  86     CRX_HASH_VERIFICATION_FAILED,
  87   };
  88
  89   // Validates that the .crx file at |crx_path| is properly signed.  If
  90   // |expected_hash| is non-empty, it should specify a hex-encoded SHA256 hash
  91   // for the entire .crx file which will be checked as we read it, and any
  92   // mismatch will cause a CRX_HASH_VERIFICATION_FAILED result.  The
  93   // |public_key| argument can be provided to receive a copy of the
  94   // base64-encoded public key pem bytes extracted from the .crx. The
  95   // |extension_id| argument can be provided to receive the extension id (which
  96   // is computed as a hash of the public key provided in the .crx). The
  97   // |header| argument can be provided to receive a copy of the crx header.
  98   static ValidateError ValidateSignature(const base::FilePath& crx_path,
  99                                          const std::string& expected_hash,
 100                                          std::string* public_key,
 101                                          std::string* extension_id,
 102                                          CrxFile::Header* header);
 103
 104  private:
 105   Header header_;
 106
 107   // Constructor is private. Clients should use static factory methods above.
 108   explicit CrxFile(const Header& header);
 109
 110   // Checks the |header| for validity and returns true if the values are valid.
 111   // If false is returned, more detailed error code is returned in |error|.
 112   static bool HeaderIsValid(const Header& header, Error* error);
 113 };
 114
 115 }  // namespace crx_file
 116
 117 #endif  // COMPONENTS_CRX_FILE_CRX_FILE_H_