mcs/class/corlib/System.Security.Policy/HashMembershipCondition.cs

   1 //
   2 // System.Security.Policy.HashMembershipCondition
   3 //
   4 // Author(s):
   5 //  Jackson Harper (Jackson@LatitudeGeo.com)
   6 //
   7 // (C) 2002 Jackson Harper, All rights reserved
   8 //
   9
  10 using System.Text;
  11 using System.Reflection;
  12 using System.Security.Cryptography;
  13
  14 namespace System.Security.Policy {
  15
  16         [Serializable]
  17         public sealed class HashMembershipCondition : IMembershipCondition,
  18                 ISecurityEncodable, ISecurityPolicyEncodable {
  19
  20                 private static readonly string XmlTag = "IMembershipCondition";
  21
  22                 private HashAlgorithm hash_algorithm;
  23                 private byte[] hash_value;
  24
  25                 public HashMembershipCondition (HashAlgorithm hash_algorithm,
  26                         byte[] hash_value)
  27                 {
  28                         if (hash_algorithm == null || hash_value == null)
  29                                 throw new ArgumentNullException ();
  30
  31                         this.hash_algorithm = hash_algorithm;
  32                         this.hash_value = hash_value;
  33                 }
  34
  35                 //
  36                 // Public Properties
  37                 //
  38
  39                 public HashAlgorithm HashAlgorithm {
  40                         get { return hash_algorithm; }
  41                         set {
  42                                 if (value == null)
  43                                         throw new ArgumentNullException ();
  44                                 hash_algorithm = value;
  45                         }
  46                 }
  47
  48                 public byte[] HashValue {
  49                         get { return hash_value; }
  50                         set {
  51                                 if (value == null)
  52                                         throw new ArgumentNullException ();
  53                                 hash_value = value;
  54                         }
  55                 }
  56
  57                 //
  58                 // Public Methods
  59                 //
  60
  61                 public bool Check (Evidence evidence)
  62                 {
  63                         if (evidence == null)
  64                                 throw new ArgumentNullException ();
  65
  66                         // Loop through evidence finding the first Hash object
  67                         foreach (object obj in evidence) {
  68                                 Hash hash = obj as Hash;
  69                                 if (hash == null)
  70                                         continue;
  71                                 if (EqualsHashValue (hash.GenerateHash (hash_algorithm)))
  72                                         return true;
  73                                 break;
  74                         }
  75                         return false;
  76                 }
  77
  78                 public IMembershipCondition Copy ()
  79                 {
  80                         return new HashMembershipCondition (hash_algorithm, hash_value);
  81                 }
  82
  83                 public override bool Equals (object o)
  84                 {
  85                         HashMembershipCondition other;
  86                         if (!(o is HashMembershipCondition))
  87                                 return false;
  88
  89                         other = (HashMembershipCondition)o;
  90
  91                         return (other.HashAlgorithm == hash_algorithm &&
  92                                 other.HashValue == hash_value);
  93                 }
  94
  95                 public SecurityElement ToXml()
  96                 {
  97                         return ToXml (null);
  98                 }
  99
 100                 public SecurityElement ToXml (PolicyLevel level)
 101                 {
 102                         SecurityElement se = new SecurityElement (XmlTag);
 103                         Type type = this.GetType ();
 104                         string classString = type.FullName + ", " + type.Assembly;
 105                         se.AddAttribute ("class", classString);
 106                         se.AddAttribute ("version", "1");
 107                         se.AddAttribute ("HashValue", Encoding.Default.GetString (hash_value));
 108                         se.AddAttribute ("HashAlgorithm", hash_algorithm.GetType ().FullName);
 109                         return se;
 110                 }
 111
 112                 public void FromXml (SecurityElement element)
 113                 {
 114                         FromXml (element, null);
 115                 }
 116
 117                 public void FromXml (SecurityElement e,
 118                         PolicyLevel level)
 119                 {
 120                         if (e == null)
 121                                 throw new ArgumentNullException ();
 122                         if (e.Tag != XmlTag)
 123                                 throw new ArgumentException(
 124                                         "e","The Tag of SecurityElement must be " + XmlTag);
 125
 126                         string value = (string)e.Attributes["HashValue"];
 127                         string algorithm = (string)e.Attributes["HashAlgorithm"];
 128
 129                         if (value == null || algorithm == null )
 130                                 throw new ArgumentException ();
 131
 132                         hash_value = Encoding.Default.GetBytes (value);
 133                         hash_algorithm = (HashAlgorithm)Assembly.GetExecutingAssembly ().CreateInstance (algorithm);
 134
 135                 }
 136
 137                 [MonoTODO("This is not right")]
 138                 public override int GetHashCode ()
 139                 {
 140                         return hash_value.GetHashCode ();
 141                 }
 142
 143                 public override string ToString ()
 144                 {
 145                         StringBuilder builder = new StringBuilder ();
 146                         Type alg_type = hash_algorithm.GetType ();
 147
 148                         builder.Append ("Hash -");
 149                         builder.AppendFormat ("{0} {1}", alg_type.FullName,
 150                                 alg_type.Assembly);
 151                         builder.AppendFormat (" = ",  Encoding.Default.GetString (hash_value));
 152
 153                         return builder.ToString ();
 154                 }
 155
 156                 //
 157                 // Private Methods
 158                 //
 159
 160                 private bool EqualsHashValue (byte[] value)
 161                 {
 162                         int len;
 163
 164                         if (value.Length != hash_value.Length)
 165                                 return false;
 166
 167                         len = value.Length;
 168                         for (int i=0; i<len; i++ ) {
 169                                 if (value[i] != hash_value[i])
 170                                         return false;
 171                         }
 172
 173                         return true;
 174                 }
 175         }
 176 }
 177