mcs/class/corlib/Mono.Security/ASN1Convert.cs

   1 //
   2 // ASN1Convert.cs: Abstract Syntax Notation 1 convertion routines
   3 //
   4 // Authors:
   5 //      Sebastien Pouliot  <sebastien@ximian.com>
   6 //      Jesper Pedersen  <jep@itplus.dk>
   7 //
   8 // (C) 2003 Motus Technologies Inc. (http://www.motus.com)
   9 // (C) 2004 Novell (http://www.novell.com)
  10 // (C) 2004 IT+ A/S (http://www.itplus.dk)
  11 //
  12
  13 using System;
  14 using System.Collections;
  15 using System.Security.Cryptography;
  16 using System.Text;
  17
  18 namespace Mono.Security {
  19
  20         // References:
  21         // a.   ITU ASN.1 standards (free download)
  22         //      http://www.itu.int/ITU-T/studygroups/com17/languages/
  23
  24 #if INSIDE_CORLIB
  25         internal
  26 #else
  27         public
  28 #endif
  29         class ASN1Convert {
  30
  31                 // RFC3280, section 4.2.1.5
  32                 // CAs conforming to this profile MUST always encode certificate
  33                 // validity dates through the year 2049 as UTCTime; certificate validity
  34                 // dates in 2050 or later MUST be encoded as GeneralizedTime.
  35                 static public ASN1 FromDateTime (DateTime dt)
  36                 {
  37                         if (dt.Year < 2050) {
  38                                 // UTCTIME
  39                                 return new ASN1 (0x17, Encoding.ASCII.GetBytes (dt.ToString ("yyMMddHHmmss") + "Z"));
  40                         }
  41                         else {
  42                                 // GENERALIZEDTIME
  43                                 return new ASN1 (0x18, Encoding.ASCII.GetBytes (dt.ToString ("yyyyMMddHHmmss") + "Z"));
  44                         }
  45                 }
  46
  47                 static public ASN1 FromInt32 (Int32 value)
  48                 {
  49                         byte[] integer = BitConverterLE.GetBytes (value);
  50                         int x = 3;
  51                         while (integer [x] == 0x00)
  52                                 x--;
  53                         ASN1 asn1 = new ASN1 (0x02);
  54
  55                         byte[] smallerInt = new byte [x + 1];
  56                         int index = smallerInt.Length - 1;
  57                         for (int i = 0; i < smallerInt.Length; i++) {
  58                                 smallerInt [index] = integer [i];
  59                                 index--;
  60                         }
  61                         asn1.Value = smallerInt;
  62
  63                         return asn1;
  64                 }
  65
  66                 static public ASN1 FromOID (string oid)
  67                 {
  68                         return new ASN1 (CryptoConfig.EncodeOID (oid));
  69                 }
  70
  71                 static public ASN1 FromUnsignedBigInteger (byte[] integer)
  72                 {
  73                         if (integer [0] == 0x00) {
  74                                 // this first byte is added so we're sure it's an unsigned integer
  75                                 // however we can't feed it into RSAParameters or DSAParameters
  76                                 int length = integer.Length + 1;
  77                                 byte[] uinteger = new byte [length];
  78                                 Array.Copy (integer, 0, uinteger, 1, length);
  79                                 integer = uinteger;
  80                         }
  81                         return new ASN1 (0x02, integer);
  82                 }
  83
  84                 static public int ToInt32 (ASN1 asn1)
  85                 {
  86                         if (asn1.Tag != 0x02)
  87                                 throw new NotSupportedException ("Only integer can be converted");
  88                         int x = 0;
  89                         for (int i=0; i < asn1.Value.Length; i++)
  90                                 x = (x << 8) + asn1.Value [i];
  91                         return x;
  92                 }
  93
  94                 // Convert a binary encoded OID to human readable string representation of
  95                 // an OID (IETF style). Based on DUMPASN1.C from Peter Gutmann.
  96                 static public string ToOID (ASN1 asn1)
  97                 {
  98                         byte[] aOID = asn1.Value;
  99                         StringBuilder sb = new StringBuilder ();
 100                         // Pick apart the OID
 101                         byte x = (byte) (aOID[0] / 40);
 102                         byte y = (byte) (aOID[0] % 40);
 103                         if (x > 2) {
 104                                 // Handle special case for large y if x = 2
 105                                 y += (byte) ((x - 2) * 40);
 106                                 x = 2;
 107                         }
 108                         sb.Append (x.ToString ());
 109                         sb.Append (".");
 110                         sb.Append (y.ToString ());
 111                         ulong val = 0;
 112                         for (x = 1; x < aOID.Length; x++) {
 113                                 val = ((val << 7) | ((byte) (aOID [x] & 0x7F)));
 114                                 if ( !((aOID [x] & 0x80) == 0x80)) {
 115                                         sb.Append (".");
 116                                         sb.Append (val.ToString ());
 117                                         val = 0;
 118                                 }
 119                         }
 120                         return sb.ToString ();
 121                 }
 122
 123                 static public DateTime ToDateTime (ASN1 time)
 124                 {
 125                         string t = Encoding.ASCII.GetString (time.Value);
 126                         // to support both UTCTime and GeneralizedTime (and not so common format)
 127                         string mask = null;
 128                         switch (t.Length) {
 129                                 case 11:
 130                                         mask = "yyMMddHHmmZ"; // illegal I think ... must check
 131                                         break;
 132                                 case 13:
 133                                         // RFC3280: 4.1.2.5.1  UTCTime
 134                                         int year = Convert.ToInt16 (t.Substring (0, 2));
 135                                         // Where YY is greater than or equal to 50, the
 136                                         // year SHALL be interpreted as 19YY; and
 137                                         // Where YY is less than 50, the year SHALL be
 138                                         // interpreted as 20YY.
 139                                         if (year >= 50)
 140                                                 t = "19" + t;
 141                                         else
 142                                                 t = "20" + t;
 143                                         mask = "yyyyMMddHHmmssZ";
 144                                         break;
 145                                 case 15:
 146                                         mask = "yyyyMMddHHmmssZ"; // GeneralizedTime
 147                                         break;
 148                         }
 149                         return DateTime.ParseExact (t, mask, null);
 150                 }
 151         }
 152 }