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

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