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.AppendChild (doc.ImportNode (xel, true));
 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, bool check_hmac)
 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.AppendChild (doc.ImportNode (found, true));
 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                                                 found = GetIdElement (envdoc, objectName);
 332                                                 if (found != null) {
 333                                                         doc.AppendChild (doc.ImportNode (found, true));
 334                                                         FixupNamespaceNodes (found, doc.DocumentElement, false);
 335                                                 }
 336                                         }
 337                                         if (found == null)
 338                                                 throw new CryptographicException (String.Format ("Malformed reference object: {0}", objectName));
 339                                 }
 340                         }
 341
 342                         if (r.TransformChain.Count > 0) {
 343                                 foreach (Transform t in r.TransformChain) {
 344                                         if (s == null) {
 345                                                 s = ApplyTransform (t, doc);
 346                                         }
 347                                         else {
 348                                                 t.LoadInput (s);
 349                                                 object o = t.GetOutput ();
 350                                                 if (o is Stream)
 351                                                         s = (Stream) o;
 352                                                 else
 353                                                         s = CanonicalizeOutput (o);
 354                                         }
 355                                 }
 356                         }
 357                         else if (s == null) {
 358                                 // we must not C14N references from outside the document
 359                                 // e.g. non-xml documents
 360                                 if (r.Uri [0] != '#') {
 361                                         s = new MemoryStream ();
 362                                         doc.Save (s);
 363                                 }
 364                                 else {
 365                                         // apply default C14N transformation
 366                                         s = ApplyTransform (new XmlDsigC14NTransform (), doc);
 367                                 }
 368                         }
 369                         HashAlgorithm digest = GetHash (r.DigestMethod, check_hmac);
 370                         return (digest == null) ? null : digest.ComputeHash (s);
 371                 }
 372
 373                 private void DigestReferences ()
 374                 {
 375                         // we must tell each reference which hash algorithm to use
 376                         // before asking for the SignedInfo XML !
 377                         foreach (Reference r in m_signature.SignedInfo.References) {
 378                                 // assume SHA-1 if nothing is specified
 379                                 if (r.DigestMethod == null)
 380                                         r.DigestMethod = XmlDsigSHA1Url;
 381                                 r.DigestValue = GetReferenceHash (r, false);
 382                         }
 383                 }
 384
 385                 private Transform GetC14NMethod ()
 386                 {
 387                         Transform t = (Transform) CryptoConfig.CreateFromName (m_signature.SignedInfo.CanonicalizationMethod);
 388                         if (t == null)
 389                                 throw new CryptographicException ("Unknown Canonicalization Method {0}", m_signature.SignedInfo.CanonicalizationMethod);
 390                         return t;
 391                 }
 392
 393                 private Stream SignedInfoTransformed ()
 394                 {
 395                         Transform t = GetC14NMethod ();
 396
 397                         if (signatureElement == null) {
 398                                 // when creating signatures
 399                                 XmlDocument doc = new XmlDocument ();
 400                                 doc.PreserveWhitespace = true;
 401                                 doc.LoadXml (m_signature.SignedInfo.GetXml ().OuterXml);
 402                                 if (envdoc != null)
 403                                 foreach (XmlAttribute attr in envdoc.DocumentElement.SelectNodes ("namespace::*")) {
 404                                         if (attr.LocalName == "xml")
 405                                                 continue;
 406                                         if (attr.Prefix == doc.DocumentElement.Prefix)
 407                                                 continue;
 408                                         doc.DocumentElement.SetAttributeNode (doc.ImportNode (attr, true) as XmlAttribute);
 409                                 }
 410                                 t.LoadInput (doc);
 411                         }
 412                         else {
 413                                 // when verifying signatures
 414                                 // TODO - check m_signature.SignedInfo.Id
 415                                 XmlElement el = signatureElement.GetElementsByTagName (XmlSignature.ElementNames.SignedInfo, XmlSignature.NamespaceURI) [0] as XmlElement;
 416                                 StringWriter sw = new StringWriter ();
 417                                 XmlTextWriter xtw = new XmlTextWriter (sw);
 418                                 xtw.WriteStartElement (el.Prefix, el.LocalName, el.NamespaceURI);
 419
 420                                 // context namespace nodes (except for "xmlns:xml")
 421                                 XmlNodeList nl = el.SelectNodes ("namespace::*");
 422                                 foreach (XmlAttribute attr in nl) {
 423                                         if (attr.ParentNode == el)
 424                                                 continue;
 425                                         if (attr.LocalName == "xml")
 426                                                 continue;
 427                                         if (attr.Prefix == el.Prefix)
 428                                                 continue;
 429                                         attr.WriteTo (xtw);
 430                                 }
 431                                 foreach (XmlNode attr in el.Attributes)
 432                                         attr.WriteTo (xtw);
 433                                 foreach (XmlNode n in el.ChildNodes)
 434                                         n.WriteTo (xtw);
 435
 436                                 xtw.WriteEndElement ();
 437                                 byte [] si = Encoding.UTF8.GetBytes (sw.ToString ());
 438
 439                                 MemoryStream ms = new MemoryStream ();
 440                                 ms.Write (si, 0, si.Length);
 441                                 ms.Position = 0;
 442
 443                                 t.LoadInput (ms);
 444                         }
 445                         // C14N and C14NWithComments always return a Stream in GetOutput
 446                         return (Stream) t.GetOutput ();
 447                 }
 448
 449                 // reuse hash - most document will always use the same hash
 450                 private HashAlgorithm GetHash (string algorithm, bool check_hmac)
 451                 {
 452                         HashAlgorithm hash = (HashAlgorithm) hashes [algorithm];
 453                         if (hash == null) {
 454                                 hash = HashAlgorithm.Create (algorithm);
 455                                 if (hash == null)
 456                                         throw new CryptographicException ("Unknown hash algorithm: {0}", algorithm);
 457                                 hashes.Add (algorithm, hash);
 458                                 // now ready to be used
 459                         }
 460                         else {
 461                                 // important before reusing an hash object
 462                                 hash.Initialize ();
 463                         }
 464                         // we can sign using any hash algorith, including HMAC, but we can only verify hash (MS compatibility)
 465                         if (check_hmac && (hash is KeyedHashAlgorithm))
 466                                 return null;
 467                         return hash;
 468                 }
 469
 470                 public bool CheckSignature ()
 471                 {
 472                         return (CheckSignatureInternal (null) != null);
 473                 }
 474
 475                 private bool CheckReferenceIntegrity (ArrayList referenceList)
 476                 {
 477                         if (referenceList == null)
 478                                 return false;
 479
 480                         // check digest (hash) for every reference
 481                         foreach (Reference r in referenceList) {
 482                                 // stop at first broken reference
 483                                 byte[] hash = GetReferenceHash (r, true);
 484                                 if (! Compare (r.DigestValue, hash))
 485                                         return false;
 486                         }
 487                         return true;
 488                 }
 489
 490                 public bool CheckSignature (AsymmetricAlgorithm key)
 491                 {
 492                         if (key == null)
 493                                 throw new ArgumentNullException ("key");
 494                         return (CheckSignatureInternal (key) != null);
 495                 }
 496
 497                 private AsymmetricAlgorithm CheckSignatureInternal (AsymmetricAlgorithm key)
 498                 {
 499                         pkEnumerator = null;
 500
 501                         if (key != null) {
 502                                 // check with supplied key
 503                                 if (!CheckSignatureWithKey (key))
 504                                         return null;
 505                         } else {
 506 #if NET_2_0
 507                                 if (Signature.KeyInfo == null)
 508                                         return null;
 509 #else
 510                                 if (Signature.KeyInfo == null)
 511                                         throw new CryptographicException ("At least one KeyInfo is required.");
 512 #endif
 513                                 // no supplied key, iterates all KeyInfo
 514                                 while ((key = GetPublicKey ()) != null) {
 515                                         if (CheckSignatureWithKey (key)) {
 516                                                 break;
 517                                         }
 518                                 }
 519                                 pkEnumerator = null;
 520                                 if (key == null)
 521                                         return null;
 522                         }
 523
 524                         // some parts may need to be downloaded
 525                         // so where doing it last
 526                         if (!CheckReferenceIntegrity (m_signature.SignedInfo.References))
 527                                 return null;
 528
 529                         if (manifests != null) {
 530                                 // do not use foreach as a manifest could contain manifests...
 531                                 for (int i=0; i < manifests.Count; i++) {
 532                                         Manifest manifest = new Manifest ((manifests [i] as XmlDocument).DocumentElement);
 533                                         if (! CheckReferenceIntegrity (manifest.References))
 534                                                 return null;
 535                                 }
 536                         }
 537                         return key;
 538                 }
 539
 540                 // Is the signature (over SignedInfo) valid ?
 541                 private bool CheckSignatureWithKey (AsymmetricAlgorithm key)
 542                 {
 543                         if (key == null)
 544                                 return false;
 545
 546                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 547                         if (sd == null)
 548                                 return false;
 549
 550                         AsymmetricSignatureDeformatter verifier = (AsymmetricSignatureDeformatter) CryptoConfig.CreateFromName (sd.DeformatterAlgorithm);
 551                         if (verifier == null)
 552                                 return false;
 553
 554                         try {
 555                                 verifier.SetKey (key);
 556                                 verifier.SetHashAlgorithm (sd.DigestAlgorithm);
 557
 558                                 HashAlgorithm hash = GetHash (sd.DigestAlgorithm, true);
 559                                 // get the hash of the C14N SignedInfo element
 560                                 MemoryStream ms = (MemoryStream) SignedInfoTransformed ();
 561
 562                                 byte[] digest = hash.ComputeHash (ms);
 563                                 return verifier.VerifySignature (digest, m_signature.SignatureValue);
 564                         }
 565                         catch {
 566                                 // e.g. SignatureMethod != AsymmetricAlgorithm type
 567                                 return false;
 568                         }
 569                 }
 570
 571                 private bool Compare (byte[] expected, byte[] actual)
 572                 {
 573                         bool result = ((expected != null) && (actual != null));
 574                         if (result) {
 575                                 int l = expected.Length;
 576                                 result = (l == actual.Length);
 577                                 if (result) {
 578                                         for (int i=0; i < l; i++) {
 579                                                 if (expected[i] != actual[i])
 580                                                         return false;
 581                                         }
 582                                 }
 583                         }
 584                         return result;
 585                 }
 586
 587                 public bool CheckSignature (KeyedHashAlgorithm macAlg)
 588                 {
 589                         if (macAlg == null)
 590                                 throw new ArgumentNullException ("macAlg");
 591
 592                         pkEnumerator = null;
 593
 594                         // Is the signature (over SignedInfo) valid ?
 595                         Stream s = SignedInfoTransformed ();
 596                         if (s == null)
 597                                 return false;
 598
 599                         byte[] actual = macAlg.ComputeHash (s);
 600                         // HMAC signature may be partial and specified by <HMACOutputLength>
 601                         if (m_signature.SignedInfo.SignatureLength != null) {
 602                                 int length = Int32.Parse (m_signature.SignedInfo.SignatureLength);
 603                                 // we only support signatures with a multiple of 8 bits
 604                                 // and the value must match the signature length
 605                                 if ((length & 7) != 0)
 606                                         throw new CryptographicException ("Signature length must be a multiple of 8 bits.");
 607
 608                                 // SignatureLength is in bits (and we works on bytes, only in multiple of 8 bits)
 609                                 // and both values must match for a signature to be valid
 610                                 length >>= 3;
 611                                 if (length != m_signature.SignatureValue.Length)
 612                                         throw new CryptographicException ("Invalid signature length.");
 613
 614                                 // is the length "big" enough to make the signature meaningful ?
 615                                 // we use a minimum of 80 bits (10 bytes) or half the HMAC normal output length
 616                                 // e.g. HMACMD5 output 128 bits but our minimum is 80 bits (not 64 bits)
 617                                 int minimum = Math.Max (10, actual.Length / 2);
 618                                 if (length < minimum)
 619                                         throw new CryptographicException ("HMAC signature is too small");
 620
 621                                 if (length < actual.Length) {
 622                                         byte[] trunked = new byte [length];
 623                                         Buffer.BlockCopy (actual, 0, trunked, 0, length);
 624                                         actual = trunked;
 625                                 }
 626                         }
 627
 628                         if (Compare (m_signature.SignatureValue, actual)) {
 629                                 // some parts may need to be downloaded
 630                                 // so where doing it last
 631                                 return CheckReferenceIntegrity (m_signature.SignedInfo.References);
 632                         }
 633                         return false;
 634                 }
 635
 636 #if NET_2_0
 637                 [MonoTODO]
 638                 [ComVisible (false)]
 639                 public bool CheckSignature (X509Certificate2 certificate, bool verifySignatureOnly)
 640                 {
 641                         throw new NotImplementedException ();
 642                 }
 643 #endif
 644
 645                 public bool CheckSignatureReturningKey (out AsymmetricAlgorithm signingKey)
 646                 {
 647                         signingKey = CheckSignatureInternal (null);
 648                         return (signingKey != null);
 649                 }
 650
 651                 public void ComputeSignature ()
 652                 {
 653                         if (key != null) {
 654                                 if (m_signature.SignedInfo.SignatureMethod == null)
 655                                         // required before hashing
 656                                         m_signature.SignedInfo.SignatureMethod = key.SignatureAlgorithm;
 657                                 else if (m_signature.SignedInfo.SignatureMethod != key.SignatureAlgorithm)
 658                                         throw new CryptographicException ("Specified SignatureAlgorithm is not supported by the signing key.");
 659                                 DigestReferences ();
 660
 661                                 AsymmetricSignatureFormatter signer = null;
 662                                 // in need for a CryptoConfig factory
 663                                 if (key is DSA)
 664                                         signer = new DSASignatureFormatter (key);
 665                                 else if (key is RSA)
 666                                         signer = new RSAPKCS1SignatureFormatter (key);
 667
 668                                 if (signer != null) {
 669                                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 670
 671                                         HashAlgorithm hash = GetHash (sd.DigestAlgorithm, false);
 672                                         // get the hash of the C14N SignedInfo element
 673                                         byte[] digest = hash.ComputeHash (SignedInfoTransformed ());
 674
 675                                         signer.SetHashAlgorithm ("SHA1");
 676                                         m_signature.SignatureValue = signer.CreateSignature (digest);
 677                                 }
 678                         }
 679                         else
 680                                 throw new CryptographicException ("signing key is not specified");
 681                 }
 682
 683                 public void ComputeSignature (KeyedHashAlgorithm macAlg)
 684                 {
 685                         if (macAlg == null)
 686                                 throw new ArgumentNullException ("macAlg");
 687
 688                         string method = null;
 689
 690                         if (macAlg is HMACSHA1) {
 691                                 method = XmlDsigHMACSHA1Url;
 692 #if NET_2_0
 693                         } else if (macAlg is HMACSHA256) {
 694                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha256";
 695                         } else if (macAlg is HMACSHA384) {
 696                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha384";
 697                         } else if (macAlg is HMACSHA512) {
 698                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha512";
 699                         } else if (macAlg is HMACRIPEMD160) {
 700                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-ripemd160";
 701 #endif
 702                         }
 703
 704                         if (method == null)
 705                                 throw new CryptographicException ("unsupported algorithm");
 706
 707                         DigestReferences ();
 708                         m_signature.SignedInfo.SignatureMethod = method;
 709                         m_signature.SignatureValue = macAlg.ComputeHash (SignedInfoTransformed ());
 710                 }
 711
 712                 public virtual XmlElement GetIdElement (XmlDocument document, string idValue)
 713                 {
 714                         if ((document == null) || (idValue == null))
 715                                 return null;
 716
 717                         // this works only if there's a DTD or XSD available to define the ID
 718                         XmlElement xel = document.GetElementById (idValue);
 719                         if (xel == null) {
 720                                 // search an "undefined" ID
 721                                 xel = (XmlElement) document.SelectSingleNode ("//*[@Id='" + idValue + "']");
 722                         }
 723                         return xel;
 724                 }
 725
 726                 // According to book ".NET Framework Security" this method
 727                 // iterates all possible keys then return null
 728                 protected virtual AsymmetricAlgorithm GetPublicKey ()
 729                 {
 730                         if (m_signature.KeyInfo == null)
 731                                 return null;
 732
 733                         if (pkEnumerator == null) {
 734                                 pkEnumerator = m_signature.KeyInfo.GetEnumerator ();
 735                         }
 736
 737 #if NET_2_0 && SECURITY_DEP
 738                         if (_x509Enumerator != null) {
 739                                 if (_x509Enumerator.MoveNext ()) {
 740                                         X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 741                                         return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 742                                 } else {
 743                                         _x509Enumerator = null;
 744                                 }
 745                         }
 746 #endif
 747                         while (pkEnumerator.MoveNext ()) {
 748                                 AsymmetricAlgorithm key = null;
 749                                 KeyInfoClause kic = (KeyInfoClause) pkEnumerator.Current;
 750
 751                                 if (kic is DSAKeyValue)
 752                                         key = DSA.Create ();
 753                                 else if (kic is RSAKeyValue)
 754                                         key = RSA.Create ();
 755
 756                                 if (key != null) {
 757                                         key.FromXmlString (kic.GetXml ().InnerXml);
 758                                         return key;
 759                                 }
 760
 761 #if NET_2_0 && SECURITY_DEP
 762                                 if (kic is KeyInfoX509Data) {
 763                                         _x509Enumerator = ((KeyInfoX509Data) kic).Certificates.GetEnumerator ();
 764                                         if (_x509Enumerator.MoveNext ()) {
 765                                                 X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 766                                                 return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 767                                         }
 768                                 }
 769 #endif
 770                         }
 771                         return null;
 772                 }
 773
 774                 public XmlElement GetXml ()
 775                 {
 776                         return m_signature.GetXml (envdoc);
 777                 }
 778
 779                 public void LoadXml (XmlElement value)
 780                 {
 781                         if (value == null)
 782                                 throw new ArgumentNullException ("value");
 783
 784                         signatureElement = value;
 785                         m_signature.LoadXml (value);
 786 #if NET_2_0
 787                         // Need to give the EncryptedXml object to the
 788                         // XmlDecryptionTransform to give it a fighting
 789                         // chance at decrypting the document.
 790                         foreach (Reference r in m_signature.SignedInfo.References) {
 791                                 foreach (Transform t in r.TransformChain) {
 792                                         if (t is XmlDecryptionTransform)
 793                                                 ((XmlDecryptionTransform) t).EncryptedXml = EncryptedXml;
 794                                 }
 795                         }
 796 #endif
 797                 }
 798
 799 #if NET_1_1
 800                 [ComVisible (false)]
 801                 public XmlResolver Resolver {
 802                         set { xmlResolver = value; }
 803                 }
 804 #endif
 805         }
 806 }