net/der/tag.h

   1 // Copyright 2015 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 NET_DER_TAG_H_
   6 #define NET_DER_TAG_H_
   7
   8 #include <stdint.h>
   9
  10 #include "net/base/net_export.h"
  11
  12 namespace net {
  13
  14 namespace der {
  15
  16 // This Tag type represents the identifier for an ASN.1 tag as encoded with DER.
  17 // It follows the same bit-for-bit representation (including the class, tag
  18 // number, and primitive/constructed bit) as DER. Constants are provided for
  19 // universal class types, and functions are provided for building context
  20 // specific tags. Tags can also be built from the provided constants and
  21 // bitmasks.
  22 using Tag = uint8_t;
  23
  24 // Universal class primitive types
  25 const Tag kBool = 0x01;
  26 const Tag kInteger = 0x02;
  27 const Tag kBitString = 0x03;
  28 const Tag kOctetString = 0x04;
  29 const Tag kNull = 0x05;
  30 const Tag kOid = 0x06;
  31 const Tag kUtf8String = 0x0C;
  32 const Tag kPrintableString = 0x13;
  33 const Tag kUtcTime = 0x17;
  34 const Tag kGeneralizedTime = 0x18;
  35
  36 // Universal class constructed types
  37 const Tag kSequence = 0x30;
  38 const Tag kSet = 0x31;
  39
  40 // Primitive/constructed bits
  41 const uint8_t kTagPrimitive = 0x00;
  42 const uint8_t kTagConstructed = 0x20;
  43
  44 // Tag classes
  45 const uint8_t kTagUniversal = 0x00;
  46 const uint8_t kTagApplication = 0x40;
  47 const uint8_t kTagContextSpecific = 0x80;
  48 const uint8_t kTagPrivate = 0xC0;
  49
  50 // Masks for the 3 components of a tag (class, primitive/constructed, number)
  51 const uint8_t kTagNumberMask = 0x1F;
  52 const uint8_t kTagConstructionMask = 0x20;
  53 const uint8_t kTagClassMask = 0xC0;
  54
  55 // Creates the value for the outter tag of an explicitly tagged type.
  56 //
  57 // The ASN.1 keyword for this is:
  58 //     [class_number] EXPLICIT
  59 //
  60 // (Note, the EXPLICIT may be omitted if the entire schema is in
  61 // EXPLICIT mode, the default)
  62 NET_EXPORT Tag ContextSpecificConstructed(uint8_t class_number);
  63
  64 NET_EXPORT Tag ContextSpecificPrimitive(uint8_t base);
  65 NET_EXPORT bool IsConstructed(Tag tag);
  66
  67 }  // namespace der
  68
  69 }  // namespace net
  70
  71 #endif  // NET_DER_TAG_H_