mcs/class/System.Security/System.Security.Cryptography.Xml/SignedXml.cs

   1 //
   2 // SignedXml.cs - SignedXml implementation for XML Signature
   3 //
   4 // Author:
   5 //      Sebastien Pouliot  <sebastien@ximian.com>
   6 //      Atsushi Enomoto <atsushi@ximian.com>
   7 //      Tim Coleman <tim@timcoleman.com>
   8 //
   9 // (C) 2002, 2003 Motus Technologies Inc. (http://www.motus.com)
  10 // Copyright (C) Tim Coleman, 2004
  11 // Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
  12 //
  13 // Permission is hereby granted, free of charge, to any person obtaining
  14 // a copy of this software and associated documentation files (the
  15 // "Software"), to deal in the Software without restriction, including
  16 // without limitation the rights to use, copy, modify, merge, publish,
  17 // distribute, sublicense, and/or sell copies of the Software, and to
  18 // permit persons to whom the Software is furnished to do so, subject to
  19 // the following conditions:
  20 //
  21 // The above copyright notice and this permission notice shall be
  22 // included in all copies or substantial portions of the Software.
  23 //
  24 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  28 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  29 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  30 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  31 //
  32
  33 using System.Collections;
  34 using System.IO;
  35 using System.Runtime.InteropServices;
  36 using System.Security.Cryptography;
  37 using System.Security.Policy;
  38 using System.Net;
  39 using System.Text;
  40 using System.Xml;
  41
  42 #if NET_2_0
  43 using System.Security.Cryptography.X509Certificates;
  44 #endif
  45
  46 namespace System.Security.Cryptography.Xml {
  47
  48         public class SignedXml {
  49
  50                 public const string XmlDsigCanonicalizationUrl                  = "http://www.w3.org/TR/2001/REC-xml-c14n-20010315";
  51                 public const string XmlDsigCanonicalizationWithCommentsUrl      = XmlDsigCanonicalizationUrl + "#WithComments";
  52                 public const string XmlDsigDSAUrl                               = XmlDsigNamespaceUrl + "dsa-sha1";
  53                 public const string XmlDsigHMACSHA1Url                          = XmlDsigNamespaceUrl + "hmac-sha1";
  54                 public const string XmlDsigMinimalCanonicalizationUrl           = XmlDsigNamespaceUrl + "minimal";
  55                 public const string XmlDsigNamespaceUrl                         = "http://www.w3.org/2000/09/xmldsig#";
  56                 public const string XmlDsigRSASHA1Url                           = XmlDsigNamespaceUrl + "rsa-sha1";
  57                 public const string XmlDsigSHA1Url                              = XmlDsigNamespaceUrl + "sha1";
  58
  59 #if NET_2_0
  60                 public const string XmlDecryptionTransformUrl                   = "http://www.w3.org/2002/07/decrypt#XML";
  61                 public const string XmlDsigBase64TransformUrl                   = XmlDsigNamespaceUrl + "base64";
  62                 public const string XmlDsigC14NTransformUrl                     = XmlDsigCanonicalizationUrl;
  63                 public const string XmlDsigC14NWithCommentsTransformUrl         = XmlDsigCanonicalizationWithCommentsUrl;
  64                 public const string XmlDsigEnvelopedSignatureTransformUrl       = XmlDsigNamespaceUrl + "enveloped-signature";
  65                 public const string XmlDsigExcC14NTransformUrl                  = "http://www.w3.org/2001/10/xml-exc-c14n#";
  66                 public const string XmlDsigExcC14NWithCommentsTransformUrl      = XmlDsigExcC14NTransformUrl + "WithComments";
  67                 public const string XmlDsigXPathTransformUrl                    = "http://www.w3.org/TR/1999/REC-xpath-19991116";
  68                 public const string XmlDsigXsltTransformUrl                     = "http://www.w3.org/TR/1999/REC-xslt-19991116";
  69                 public const string XmlLicenseTransformUrl                      = "urn:mpeg:mpeg21:2003:01-REL-R-NS:licenseTransform";
  70
  71                 private EncryptedXml encryptedXml;
  72 #endif
  73
  74                 protected Signature m_signature;
  75                 private AsymmetricAlgorithm key;
  76                 protected string m_strSigningKeyName;
  77                 private XmlDocument envdoc;
  78                 private IEnumerator pkEnumerator;
  79                 private XmlElement signatureElement;
  80                 private Hashtable hashes;
  81                 // FIXME: enable it after CAS implementation
  82 #if false //NET_1_1
  83                 private XmlResolver xmlResolver = new XmlSecureResolver (new XmlUrlResolver (), new Evidence ());
  84 #else
  85                 private XmlResolver xmlResolver = new XmlUrlResolver ();
  86 #endif
  87                 private ArrayList manifests;
  88 #if NET_2_0
  89                 private IEnumerator _x509Enumerator;
  90 #endif
  91
  92                 private static readonly char [] whitespaceChars = new char [] {' ', '\r', '\n', '\t'};
  93
  94                 public SignedXml ()
  95                 {
  96                         m_signature = new Signature ();
  97                         m_signature.SignedInfo = new SignedInfo ();
  98                         hashes = new Hashtable (2); // 98% SHA1 for now
  99                 }
 100
 101                 public SignedXml (XmlDocument document) : this ()
 102                 {
 103                         if (document == null)
 104                                 throw new ArgumentNullException ("document");
 105                         envdoc = document;
 106                 }
 107
 108                 public SignedXml (XmlElement elem) : this ()
 109                 {
 110                         if (elem == null)
 111                                 throw new ArgumentNullException ("elem");
 112                         envdoc = new XmlDocument ();
 113                         envdoc.LoadXml (elem.OuterXml);
 114                 }
 115
 116 #if NET_2_0
 117                 [ComVisible (false)]
 118                 public EncryptedXml EncryptedXml {
 119                         get { return encryptedXml; }
 120                         set { encryptedXml = value; }
 121                 }
 122 #endif
 123
 124                 public KeyInfo KeyInfo {
 125                         get {
 126 #if NET_2_0
 127                                 if (m_signature.KeyInfo == null)
 128                                         m_signature.KeyInfo = new KeyInfo ();
 129 #endif
 130                                 return m_signature.KeyInfo;
 131                         }
 132                         set { m_signature.KeyInfo = value; }
 133                 }
 134
 135                 public Signature Signature {
 136                         get { return m_signature; }
 137                 }
 138
 139                 public string SignatureLength {
 140                         get { return m_signature.SignedInfo.SignatureLength; }
 141                 }
 142
 143                 public string SignatureMethod {
 144                         get { return m_signature.SignedInfo.SignatureMethod; }
 145                 }
 146
 147                 public byte[] SignatureValue {
 148                         get { return m_signature.SignatureValue; }
 149                 }
 150
 151                 public SignedInfo SignedInfo {
 152                         get { return m_signature.SignedInfo; }
 153                 }
 154
 155                 public AsymmetricAlgorithm SigningKey {
 156                         get { return key; }
 157                         set { key = value; }
 158                 }
 159
 160                 // NOTE: CryptoAPI related ? documented as fx internal
 161                 public string SigningKeyName {
 162                         get { return m_strSigningKeyName; }
 163                         set { m_strSigningKeyName = value; }
 164                 }
 165
 166                 public void AddObject (DataObject dataObject)
 167                 {
 168                         m_signature.AddObject (dataObject);
 169                 }
 170
 171                 public void AddReference (Reference reference)
 172                 {
 173 #if NET_2_0
 174                         if (reference == null)
 175                                 throw new ArgumentNullException ("reference");
 176 #endif
 177                         m_signature.SignedInfo.AddReference (reference);
 178                 }
 179
 180                 private Stream ApplyTransform (Transform t, XmlDocument input)
 181                 {
 182                         // These transformer modify input document, which should
 183                         // not affect to the input itself.
 184                         if (t is XmlDsigXPathTransform
 185                                 || t is XmlDsigEnvelopedSignatureTransform
 186 #if NET_2_0
 187                                 || t is XmlDecryptionTransform
 188 #endif
 189                         )
 190                                 input = (XmlDocument) input.Clone ();
 191
 192                         t.LoadInput (input);
 193
 194                         if (t is XmlDsigEnvelopedSignatureTransform)
 195                                 // It returns XmlDocument for XmlDocument input.
 196                                 return CanonicalizeOutput (t.GetOutput ());
 197
 198                         object obj = t.GetOutput ();
 199                         if (obj is Stream)
 200                                 return (Stream) obj;
 201                         else if (obj is XmlDocument) {
 202                                 MemoryStream ms = new MemoryStream ();
 203                                 XmlTextWriter xtw = new XmlTextWriter (ms, Encoding.UTF8);
 204                                 ((XmlDocument) obj).WriteTo (xtw);
 205
 206                                 xtw.Flush ();
 207
 208                                 // Rewind to the start of the stream
 209                                 ms.Position = 0;
 210                                 return ms;
 211                         }
 212                         else if (obj == null) {
 213                                 throw new NotImplementedException ("This should not occur. Transform is " + t + ".");
 214                         }
 215                         else {
 216                                 // e.g. XmlDsigXPathTransform returns XmlNodeList
 217                                 return CanonicalizeOutput (obj);
 218                         }
 219                 }
 220
 221                 private Stream CanonicalizeOutput (object obj)
 222                 {
 223                         Transform c14n = GetC14NMethod ();
 224                         c14n.LoadInput (obj);
 225                         return (Stream) c14n.GetOutput ();
 226                 }
 227
 228                 private XmlDocument GetManifest (Reference r)
 229                 {
 230                         XmlDocument doc = new XmlDocument ();
 231                         doc.PreserveWhitespace = true;
 232
 233                         if (r.Uri [0] == '#') {
 234                                 // local manifest
 235                                 if (signatureElement != null) {
 236                                         XmlElement xel = GetIdElement (signatureElement.OwnerDocument, r.Uri.Substring (1));
 237                                         if (xel == null)
 238                                                 throw new CryptographicException ("Manifest targeted by Reference was not found: " + r.Uri.Substring (1));
 239                                         doc.LoadXml (xel.OuterXml);
 240                                         FixupNamespaceNodes (xel, doc.DocumentElement, false);
 241                                 }
 242                         }
 243                         else if (xmlResolver != null) {
 244                                 // TODO: need testing
 245                                 Stream s = (Stream) xmlResolver.GetEntity (new Uri (r.Uri), null, typeof (Stream));
 246                                 doc.Load (s);
 247                         }
 248
 249                         if (doc.FirstChild != null) {
 250                                 // keep a copy of the manifests to check their references later
 251                                 if (manifests == null)
 252                                         manifests = new ArrayList ();
 253                                 manifests.Add (doc);
 254
 255                                 return doc;
 256                         }
 257                         return null;
 258                 }
 259
 260                 private void FixupNamespaceNodes (XmlElement src, XmlElement dst, bool ignoreDefault)
 261                 {
 262                         // add namespace nodes
 263                         foreach (XmlAttribute attr in src.SelectNodes ("namespace::*")) {
 264                                 if (attr.LocalName == "xml")
 265                                         continue;
 266                                 if (ignoreDefault && attr.LocalName == "xmlns")
 267                                         continue;
 268                                 dst.SetAttributeNode (dst.OwnerDocument.ImportNode (attr, true) as XmlAttribute);
 269                         }
 270                 }
 271
 272                 private byte[] GetReferenceHash (Reference r)
 273                 {
 274                         Stream s = null;
 275                         XmlDocument doc = null;
 276                         if (r.Uri == String.Empty) {
 277                                 doc = envdoc;
 278                         }
 279                         else if (r.Type == XmlSignature.Uri.Manifest) {
 280                                 doc = GetManifest (r);
 281                         }
 282                         else {
 283                                 doc = new XmlDocument ();
 284                                 doc.PreserveWhitespace = true;
 285                                 string objectName = null;
 286
 287                                 if (r.Uri.StartsWith ("#xpointer")) {
 288                                         string uri = string.Join ("", r.Uri.Substring (9).Split (whitespaceChars));
 289                                         if (uri.Length < 2 || uri [0] != '(' || uri [uri.Length - 1] != ')')
 290                                                 // FIXME: how to handle invalid xpointer?
 291                                                 uri = String.Empty;
 292                                         else
 293                                                 uri = uri.Substring (1, uri.Length - 2);
 294                                         if (uri == "/")
 295                                                 doc = envdoc;
 296                                         else if (uri.Length > 6 && uri.StartsWith ("id(") && uri [uri.Length - 1] == ')')
 297                                                 // id('foo'), id("foo")
 298                                                 objectName = uri.Substring (4, uri.Length - 6);
 299                                 }
 300                                 else if (r.Uri [0] == '#') {
 301                                         objectName = r.Uri.Substring (1);
 302                                 }
 303                                 else if (xmlResolver != null) {
 304                                         // TODO: test but doc says that Resolver = null -> no access
 305                                         try {
 306                                                 // no way to know if valid without throwing an exception
 307                                                 Uri uri = new Uri (r.Uri);
 308                                                 s = (Stream) xmlResolver.GetEntity (uri, null, typeof (Stream));
 309                                         }
 310                                         catch {
 311                                                 // may still be a local file (and maybe not xml)
 312                                                 s = File.OpenRead (r.Uri);
 313                                         }
 314                                 }
 315                                 if (objectName != null) {
 316                                         XmlElement found = null;
 317                                         foreach (DataObject obj in m_signature.ObjectList) {
 318                                                 if (obj.Id == objectName) {
 319                                                         found = obj.GetXml ();
 320                                                         found.SetAttribute ("xmlns", SignedXml.XmlDsigNamespaceUrl);
 321                                                         doc.LoadXml (found.OuterXml);
 322                                                         // FIXME: there should be theoretical justification of copying namespace declaration nodes this way.
 323                                                         foreach (XmlNode n in found.ChildNodes)
 324                                                                 // Do not copy default namespace as it must be xmldsig namespace for "Object" element.
 325                                                                 if (n.NodeType == XmlNodeType.Element)
 326                                                                         FixupNamespaceNodes (n as XmlElement, doc.DocumentElement, true);
 327                                                         break;
 328                                                 }
 329                                         }
 330                                         if (found == null && envdoc != null) {
 331                                                 foreach (XmlElement el in envdoc.SelectNodes ("//*[@Id]"))
 332                                                         if (el.GetAttribute ("Id") == objectName) {
 333                                                                 found = el;
 334                                                                 doc.LoadXml (found.OuterXml);
 335                                                                 break;
 336                                                         }
 337                                         }
 338                                         if (found == null)
 339                                                 throw new CryptographicException (String.Format ("Malformed reference object: {0}", objectName));
 340                                 }
 341                         }
 342
 343                         if (r.TransformChain.Count > 0) {
 344                                 foreach (Transform t in r.TransformChain) {
 345                                         if (s == null) {
 346                                                 s = ApplyTransform (t, doc);
 347                                         }
 348                                         else {
 349                                                 t.LoadInput (s);
 350                                                 object o = t.GetOutput ();
 351                                                 if (o is Stream)
 352                                                         s = (Stream) o;
 353                                                 else
 354                                                         s = CanonicalizeOutput (o);
 355                                         }
 356                                 }
 357                         }
 358                         else if (s == null) {
 359                                 // we must not C14N references from outside the document
 360                                 // e.g. non-xml documents
 361                                 if (r.Uri [0] != '#') {
 362                                         s = new MemoryStream ();
 363                                         doc.Save (s);
 364                                 }
 365                                 else {
 366                                         // apply default C14N transformation
 367                                         s = ApplyTransform (new XmlDsigC14NTransform (), doc);
 368                                 }
 369                         }
 370                         HashAlgorithm digest = GetHash (r.DigestMethod);
 371                         return digest.ComputeHash (s);
 372                 }
 373
 374                 private void DigestReferences ()
 375                 {
 376                         // we must tell each reference which hash algorithm to use
 377                         // before asking for the SignedInfo XML !
 378                         foreach (Reference r in m_signature.SignedInfo.References) {
 379                                 // assume SHA-1 if nothing is specified
 380                                 if (r.DigestMethod == null)
 381                                         r.DigestMethod = XmlDsigSHA1Url;
 382                                 r.DigestValue = GetReferenceHash (r);
 383                         }
 384                 }
 385
 386                 private Transform GetC14NMethod ()
 387                 {
 388                         Transform t = (Transform) CryptoConfig.CreateFromName (m_signature.SignedInfo.CanonicalizationMethod);
 389                         if (t == null)
 390                                 throw new CryptographicException ("Unknown Canonicalization Method {0}", m_signature.SignedInfo.CanonicalizationMethod);
 391                         return t;
 392                 }
 393
 394                 private Stream SignedInfoTransformed ()
 395                 {
 396                         Transform t = GetC14NMethod ();
 397
 398                         if (signatureElement == null) {
 399                                 // when creating signatures
 400                                 XmlDocument doc = new XmlDocument ();
 401                                 doc.PreserveWhitespace = true;
 402                                 doc.LoadXml (m_signature.SignedInfo.GetXml ().OuterXml);
 403                                 if (envdoc != null)
 404                                 foreach (XmlAttribute attr in envdoc.DocumentElement.SelectNodes ("namespace::*")) {
 405                                         if (attr.LocalName == "xml")
 406                                                 continue;
 407                                         if (attr.Prefix == doc.DocumentElement.Prefix)
 408                                                 continue;
 409                                         doc.DocumentElement.SetAttributeNode (doc.ImportNode (attr, true) as XmlAttribute);
 410                                 }
 411                                 t.LoadInput (doc);
 412                         }
 413                         else {
 414                                 // when verifying signatures
 415                                 // TODO - check m_signature.SignedInfo.Id
 416                                 XmlElement el = signatureElement.GetElementsByTagName (XmlSignature.ElementNames.SignedInfo, XmlSignature.NamespaceURI) [0] as XmlElement;
 417                                 StringWriter sw = new StringWriter ();
 418                                 XmlTextWriter xtw = new XmlTextWriter (sw);
 419                                 xtw.WriteStartElement (el.Prefix, el.LocalName, el.NamespaceURI);
 420
 421                                 // context namespace nodes (except for "xmlns:xml")
 422                                 XmlNodeList nl = el.SelectNodes ("namespace::*");
 423                                 foreach (XmlAttribute attr in nl) {
 424                                         if (attr.ParentNode == el)
 425                                                 continue;
 426                                         if (attr.LocalName == "xml")
 427                                                 continue;
 428                                         if (attr.Prefix == el.Prefix)
 429                                                 continue;
 430                                         attr.WriteTo (xtw);
 431                                 }
 432                                 foreach (XmlNode attr in el.Attributes)
 433                                         attr.WriteTo (xtw);
 434                                 foreach (XmlNode n in el.ChildNodes)
 435                                         n.WriteTo (xtw);
 436
 437                                 xtw.WriteEndElement ();
 438                                 byte [] si = Encoding.UTF8.GetBytes (sw.ToString ());
 439
 440                                 MemoryStream ms = new MemoryStream ();
 441                                 ms.Write (si, 0, si.Length);
 442                                 ms.Position = 0;
 443
 444                                 t.LoadInput (ms);
 445                         }
 446                         // C14N and C14NWithComments always return a Stream in GetOutput
 447                         return (Stream) t.GetOutput ();
 448                 }
 449
 450                 // reuse hash - most document will always use the same hash
 451                 private HashAlgorithm GetHash (string algorithm)
 452                 {
 453                         HashAlgorithm hash = (HashAlgorithm) hashes [algorithm];
 454                         if (hash == null) {
 455                                 hash = HashAlgorithm.Create (algorithm);
 456                                 if (hash == null)
 457                                         throw new CryptographicException ("Unknown hash algorithm: {0}", algorithm);
 458                                 hashes.Add (algorithm, hash);
 459                                 // now ready to be used
 460                         }
 461                         else {
 462                                 // important before reusing an hash object
 463                                 hash.Initialize ();
 464                         }
 465                         return hash;
 466                 }
 467
 468                 public bool CheckSignature ()
 469                 {
 470                         return (CheckSignatureInternal (null) != null);
 471                 }
 472
 473                 private bool CheckReferenceIntegrity (ArrayList referenceList)
 474                 {
 475                         if (referenceList == null)
 476                                 return false;
 477
 478                         // check digest (hash) for every reference
 479                         foreach (Reference r in referenceList) {
 480                                 // stop at first broken reference
 481                                 byte[] hash = GetReferenceHash (r);
 482                                 if (! Compare (r.DigestValue, hash))
 483                                         return false;
 484                         }
 485                         return true;
 486                 }
 487
 488                 public bool CheckSignature (AsymmetricAlgorithm key)
 489                 {
 490                         if (key == null)
 491                                 throw new ArgumentNullException ("key");
 492                         return (CheckSignatureInternal (key) != null);
 493                 }
 494
 495                 private AsymmetricAlgorithm CheckSignatureInternal (AsymmetricAlgorithm key)
 496                 {
 497                         pkEnumerator = null;
 498
 499                         if (key != null) {
 500                                 // check with supplied key
 501                                 if (!CheckSignatureWithKey (key))
 502                                         return null;
 503                         } else {
 504 #if NET_2_0
 505                                 if (Signature.KeyInfo == null)
 506                                         return null;
 507 #else
 508                                 if (Signature.KeyInfo == null)
 509                                         throw new CryptographicException ("At least one KeyInfo is required.");
 510 #endif
 511                                 // no supplied key, iterates all KeyInfo
 512                                 while ((key = GetPublicKey ()) != null) {
 513                                         if (CheckSignatureWithKey (key)) {
 514                                                 break;
 515                                         }
 516                                 }
 517                                 pkEnumerator = null;
 518                                 if (key == null)
 519                                         return null;
 520                         }
 521
 522                         // some parts may need to be downloaded
 523                         // so where doing it last
 524                         if (!CheckReferenceIntegrity (m_signature.SignedInfo.References))
 525                                 return null;
 526
 527                         if (manifests != null) {
 528                                 // do not use foreach as a manifest could contain manifests...
 529                                 for (int i=0; i < manifests.Count; i++) {
 530                                         Manifest manifest = new Manifest ((manifests [i] as XmlDocument).DocumentElement);
 531                                         if (! CheckReferenceIntegrity (manifest.References))
 532                                                 return null;
 533                                 }
 534                         }
 535                         return key;
 536                 }
 537
 538                 // Is the signature (over SignedInfo) valid ?
 539                 private bool CheckSignatureWithKey (AsymmetricAlgorithm key)
 540                 {
 541                         if (key == null)
 542                                 return false;
 543
 544                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 545                         if (sd == null)
 546                                 return false;
 547
 548                         AsymmetricSignatureDeformatter verifier = (AsymmetricSignatureDeformatter) CryptoConfig.CreateFromName (sd.DeformatterAlgorithm);
 549                         if (verifier == null)
 550                                 return false;
 551
 552                         try {
 553                                 verifier.SetKey (key);
 554                                 verifier.SetHashAlgorithm (sd.DigestAlgorithm);
 555
 556                                 HashAlgorithm hash = GetHash (sd.DigestAlgorithm);
 557                                 // get the hash of the C14N SignedInfo element
 558                                 MemoryStream ms = (MemoryStream) SignedInfoTransformed ();
 559
 560                                 byte[] digest = hash.ComputeHash (ms);
 561                                 return verifier.VerifySignature (digest, m_signature.SignatureValue);
 562                         }
 563                         catch {
 564                                 // e.g. SignatureMethod != AsymmetricAlgorithm type
 565                                 return false;
 566                         }
 567                 }
 568
 569                 private bool Compare (byte[] expected, byte[] actual)
 570                 {
 571                         bool result = ((expected != null) && (actual != null));
 572                         if (result) {
 573                                 int l = expected.Length;
 574                                 result = (l == actual.Length);
 575                                 if (result) {
 576                                         for (int i=0; i < l; i++) {
 577                                                 if (expected[i] != actual[i])
 578                                                         return false;
 579                                         }
 580                                 }
 581                         }
 582                         return result;
 583                 }
 584
 585                 public bool CheckSignature (KeyedHashAlgorithm macAlg)
 586                 {
 587                         if (macAlg == null)
 588                                 throw new ArgumentNullException ("macAlg");
 589
 590                         pkEnumerator = null;
 591
 592                         // Is the signature (over SignedInfo) valid ?
 593                         Stream s = SignedInfoTransformed ();
 594                         if (s == null)
 595                                 return false;
 596
 597                         byte[] actual = macAlg.ComputeHash (s);
 598                         // HMAC signature may be partial
 599                         if (m_signature.SignedInfo.SignatureLength != null) {
 600                                 int length = actual.Length;
 601                                 try {
 602                                         // SignatureLength is in bits
 603                                         length = (Int32.Parse (m_signature.SignedInfo.SignatureLength) >> 3);
 604                                 }
 605                                 catch {
 606                                 }
 607
 608                                 if (length != actual.Length) {
 609                                         byte[] trunked = new byte [length];
 610                                         Buffer.BlockCopy (actual, 0, trunked, 0, length);
 611                                         actual = trunked;
 612                                 }
 613                         }
 614
 615                         if (Compare (m_signature.SignatureValue, actual)) {
 616                                 // some parts may need to be downloaded
 617                                 // so where doing it last
 618                                 return CheckReferenceIntegrity (m_signature.SignedInfo.References);
 619                         }
 620                         return false;
 621                 }
 622
 623 #if NET_2_0
 624                 [MonoTODO]
 625                 [ComVisible (false)]
 626                 public bool CheckSignature (X509Certificate2 certificate, bool verifySignatureOnly)
 627                 {
 628                         throw new NotImplementedException ();
 629                 }
 630 #endif
 631
 632                 public bool CheckSignatureReturningKey (out AsymmetricAlgorithm signingKey)
 633                 {
 634                         signingKey = CheckSignatureInternal (null);
 635                         return (signingKey != null);
 636                 }
 637
 638                 public void ComputeSignature ()
 639                 {
 640                         if (key != null) {
 641                                 if (m_signature.SignedInfo.SignatureMethod == null)
 642                                         // required before hashing
 643                                         m_signature.SignedInfo.SignatureMethod = key.SignatureAlgorithm;
 644                                 else if (m_signature.SignedInfo.SignatureMethod != key.SignatureAlgorithm)
 645                                         throw new CryptographicException ("Specified SignatureAlgorithm is not supported by the signing key.");
 646                                 DigestReferences ();
 647
 648                                 AsymmetricSignatureFormatter signer = null;
 649                                 // in need for a CryptoConfig factory
 650                                 if (key is DSA)
 651                                         signer = new DSASignatureFormatter (key);
 652                                 else if (key is RSA)
 653                                         signer = new RSAPKCS1SignatureFormatter (key);
 654
 655                                 if (signer != null) {
 656                                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 657
 658                                         HashAlgorithm hash = GetHash (sd.DigestAlgorithm);
 659                                         // get the hash of the C14N SignedInfo element
 660                                         byte[] digest = hash.ComputeHash (SignedInfoTransformed ());
 661
 662                                         signer.SetHashAlgorithm ("SHA1");
 663                                         m_signature.SignatureValue = signer.CreateSignature (digest);
 664                                 }
 665                         }
 666                         else
 667                                 throw new CryptographicException ("signing key is not specified");
 668                 }
 669
 670                 public void ComputeSignature (KeyedHashAlgorithm macAlg)
 671                 {
 672                         if (macAlg == null)
 673                                 throw new ArgumentNullException ("macAlg");
 674
 675                         if (macAlg is HMACSHA1) {
 676                                 DigestReferences ();
 677
 678                                 m_signature.SignedInfo.SignatureMethod = XmlDsigHMACSHA1Url;
 679                                 m_signature.SignatureValue = macAlg.ComputeHash (SignedInfoTransformed ());
 680                         }
 681                         else
 682                                 throw new CryptographicException ("unsupported algorithm");
 683                 }
 684
 685                 public virtual XmlElement GetIdElement (XmlDocument document, string idValue)
 686                 {
 687                         // this works only if there's a DTD or XSD available to define the ID
 688                         XmlElement xel = document.GetElementById (idValue);
 689                         if (xel == null) {
 690                                 // search an "undefined" ID
 691                                 xel = (XmlElement) document.SelectSingleNode ("//*[@Id='" + idValue + "']");
 692                         }
 693                         return xel;
 694                 }
 695
 696                 // According to book ".NET Framework Security" this method
 697                 // iterates all possible keys then return null
 698                 protected virtual AsymmetricAlgorithm GetPublicKey ()
 699                 {
 700                         if (m_signature.KeyInfo == null)
 701                                 return null;
 702
 703                         if (pkEnumerator == null) {
 704                                 pkEnumerator = m_signature.KeyInfo.GetEnumerator ();
 705                         }
 706
 707 #if NET_2_0
 708                         if (_x509Enumerator != null) {
 709                                 if (_x509Enumerator.MoveNext ()) {
 710                                         X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 711                                         return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 712                                 } else {
 713                                         _x509Enumerator = null;
 714                                 }
 715                         }
 716 #endif
 717                         while (pkEnumerator.MoveNext ()) {
 718                                 AsymmetricAlgorithm key = null;
 719                                 KeyInfoClause kic = (KeyInfoClause) pkEnumerator.Current;
 720
 721                                 if (kic is DSAKeyValue)
 722                                         key = DSA.Create ();
 723                                 else if (kic is RSAKeyValue)
 724                                         key = RSA.Create ();
 725
 726                                 if (key != null) {
 727                                         key.FromXmlString (kic.GetXml ().InnerXml);
 728                                         return key;
 729                                 }
 730
 731 #if NET_2_0
 732                                 if (kic is KeyInfoX509Data) {
 733                                         _x509Enumerator = ((KeyInfoX509Data) kic).Certificates.GetEnumerator ();
 734                                         if (_x509Enumerator.MoveNext ()) {
 735                                                 X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 736                                                 return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 737                                         }
 738                                 }
 739 #endif
 740                         }
 741                         return null;
 742                 }
 743
 744                 public XmlElement GetXml ()
 745                 {
 746                         return m_signature.GetXml (envdoc);
 747                 }
 748
 749                 public void LoadXml (XmlElement value)
 750                 {
 751                         if (value == null)
 752                                 throw new ArgumentNullException ("value");
 753
 754                         signatureElement = value;
 755                         m_signature.LoadXml (value);
 756 #if NET_2_0
 757                         // Need to give the EncryptedXml object to the
 758                         // XmlDecryptionTransform to give it a fighting
 759                         // chance at decrypting the document.
 760                         foreach (Reference r in m_signature.SignedInfo.References) {
 761                                 foreach (Transform t in r.TransformChain) {
 762                                         if (t is XmlDecryptionTransform)
 763                                                 ((XmlDecryptionTransform) t).EncryptedXml = EncryptedXml;
 764                                 }
 765                         }
 766 #endif
 767                 }
 768
 769 #if NET_1_1
 770                 [ComVisible (false)]
 771                 public XmlResolver Resolver {
 772                         set { xmlResolver = value; }
 773                 }
 774 #endif
 775         }
 776 }