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 using System.Security.Cryptography.X509Certificates;
  42
  43 namespace System.Security.Cryptography.Xml {
  44
  45         public class SignedXml {
  46
  47                 public const string XmlDsigCanonicalizationUrl                  = "http://www.w3.org/TR/2001/REC-xml-c14n-20010315";
  48                 public const string XmlDsigCanonicalizationWithCommentsUrl      = XmlDsigCanonicalizationUrl + "#WithComments";
  49                 public const string XmlDsigDSAUrl                               = XmlDsigNamespaceUrl + "dsa-sha1";
  50                 public const string XmlDsigHMACSHA1Url                          = XmlDsigNamespaceUrl + "hmac-sha1";
  51                 public const string XmlDsigMinimalCanonicalizationUrl           = XmlDsigNamespaceUrl + "minimal";
  52                 public const string XmlDsigNamespaceUrl                         = "http://www.w3.org/2000/09/xmldsig#";
  53                 public const string XmlDsigRSASHA1Url                           = XmlDsigNamespaceUrl + "rsa-sha1";
  54                 public const string XmlDsigSHA1Url                              = XmlDsigNamespaceUrl + "sha1";
  55
  56                 public const string XmlDecryptionTransformUrl                   = "http://www.w3.org/2002/07/decrypt#XML";
  57                 public const string XmlDsigBase64TransformUrl                   = XmlDsigNamespaceUrl + "base64";
  58                 public const string XmlDsigC14NTransformUrl                     = XmlDsigCanonicalizationUrl;
  59                 public const string XmlDsigC14NWithCommentsTransformUrl         = XmlDsigCanonicalizationWithCommentsUrl;
  60                 public const string XmlDsigEnvelopedSignatureTransformUrl       = XmlDsigNamespaceUrl + "enveloped-signature";
  61                 public const string XmlDsigExcC14NTransformUrl                  = "http://www.w3.org/2001/10/xml-exc-c14n#";
  62                 public const string XmlDsigExcC14NWithCommentsTransformUrl      = XmlDsigExcC14NTransformUrl + "WithComments";
  63                 public const string XmlDsigXPathTransformUrl                    = "http://www.w3.org/TR/1999/REC-xpath-19991116";
  64                 public const string XmlDsigXsltTransformUrl                     = "http://www.w3.org/TR/1999/REC-xslt-19991116";
  65                 public const string XmlLicenseTransformUrl                      = "urn:mpeg:mpeg21:2003:01-REL-R-NS:licenseTransform";
  66
  67                 private EncryptedXml encryptedXml;
  68
  69                 protected Signature m_signature;
  70                 private AsymmetricAlgorithm key;
  71                 protected string m_strSigningKeyName;
  72                 private XmlDocument envdoc;
  73                 private IEnumerator pkEnumerator;
  74                 private XmlElement signatureElement;
  75                 private Hashtable hashes;
  76                 // FIXME: enable it after CAS implementation
  77                 private XmlResolver xmlResolver = new XmlUrlResolver ();
  78                 private ArrayList manifests;
  79                 private IEnumerator _x509Enumerator;
  80
  81                 private static readonly char [] whitespaceChars = new char [] {' ', '\r', '\n', '\t'};
  82
  83                 public SignedXml ()
  84                 {
  85                         m_signature = new Signature ();
  86                         m_signature.SignedInfo = new SignedInfo ();
  87                         hashes = new Hashtable (2); // 98% SHA1 for now
  88                 }
  89
  90                 public SignedXml (XmlDocument document) : this ()
  91                 {
  92                         if (document == null)
  93                                 throw new ArgumentNullException ("document");
  94                         envdoc = document;
  95                 }
  96
  97                 public SignedXml (XmlElement elem) : this ()
  98                 {
  99                         if (elem == null)
 100                                 throw new ArgumentNullException ("elem");
 101                         envdoc = new XmlDocument ();
 102                         envdoc.LoadXml (elem.OuterXml);
 103                 }
 104
 105                 [ComVisible (false)]
 106                 public EncryptedXml EncryptedXml {
 107                         get { return encryptedXml; }
 108                         set { encryptedXml = value; }
 109                 }
 110
 111                 public KeyInfo KeyInfo {
 112                         get {
 113                                 if (m_signature.KeyInfo == null)
 114                                         m_signature.KeyInfo = new KeyInfo ();
 115                                 return m_signature.KeyInfo;
 116                         }
 117                         set { m_signature.KeyInfo = value; }
 118                 }
 119
 120                 public Signature Signature {
 121                         get { return m_signature; }
 122                 }
 123
 124                 public string SignatureLength {
 125                         get { return m_signature.SignedInfo.SignatureLength; }
 126                 }
 127
 128                 public string SignatureMethod {
 129                         get { return m_signature.SignedInfo.SignatureMethod; }
 130                 }
 131
 132                 public byte[] SignatureValue {
 133                         get { return m_signature.SignatureValue; }
 134                 }
 135
 136                 public SignedInfo SignedInfo {
 137                         get { return m_signature.SignedInfo; }
 138                 }
 139
 140                 public AsymmetricAlgorithm SigningKey {
 141                         get { return key; }
 142                         set { key = value; }
 143                 }
 144
 145                 // NOTE: CryptoAPI related ? documented as fx internal
 146                 public string SigningKeyName {
 147                         get { return m_strSigningKeyName; }
 148                         set { m_strSigningKeyName = value; }
 149                 }
 150
 151                 public void AddObject (DataObject dataObject)
 152                 {
 153                         m_signature.AddObject (dataObject);
 154                 }
 155
 156                 public void AddReference (Reference reference)
 157                 {
 158                         if (reference == null)
 159                                 throw new ArgumentNullException ("reference");
 160                         m_signature.SignedInfo.AddReference (reference);
 161                 }
 162
 163                 private Stream ApplyTransform (Transform t, XmlDocument input)
 164                 {
 165                         // These transformer modify input document, which should
 166                         // not affect to the input itself.
 167                         if (t is XmlDsigXPathTransform
 168                                 || t is XmlDsigEnvelopedSignatureTransform
 169                                 || t is XmlDecryptionTransform
 170                         )
 171                                 input = (XmlDocument) input.Clone ();
 172
 173                         t.LoadInput (input);
 174
 175                         if (t is XmlDsigEnvelopedSignatureTransform)
 176                                 // It returns XmlDocument for XmlDocument input.
 177                                 return CanonicalizeOutput (t.GetOutput ());
 178
 179                         object obj = t.GetOutput ();
 180                         if (obj is Stream)
 181                                 return (Stream) obj;
 182                         else if (obj is XmlDocument) {
 183                                 MemoryStream ms = new MemoryStream ();
 184                                 XmlTextWriter xtw = new XmlTextWriter (ms, Encoding.UTF8);
 185                                 ((XmlDocument) obj).WriteTo (xtw);
 186
 187                                 xtw.Flush ();
 188
 189                                 // Rewind to the start of the stream
 190                                 ms.Position = 0;
 191                                 return ms;
 192                         }
 193                         else if (obj == null) {
 194                                 throw new NotImplementedException ("This should not occur. Transform is " + t + ".");
 195                         }
 196                         else {
 197                                 // e.g. XmlDsigXPathTransform returns XmlNodeList
 198                                 return CanonicalizeOutput (obj);
 199                         }
 200                 }
 201
 202                 private Stream CanonicalizeOutput (object obj)
 203                 {
 204                         Transform c14n = GetC14NMethod ();
 205                         c14n.LoadInput (obj);
 206                         return (Stream) c14n.GetOutput ();
 207                 }
 208
 209                 private XmlDocument GetManifest (Reference r)
 210                 {
 211                         XmlDocument doc = new XmlDocument ();
 212                         doc.PreserveWhitespace = true;
 213
 214                         if (r.Uri [0] == '#') {
 215                                 // local manifest
 216                                 if (signatureElement != null) {
 217                                         XmlElement xel = GetIdElement (signatureElement.OwnerDocument, r.Uri.Substring (1));
 218                                         if (xel == null)
 219                                                 throw new CryptographicException ("Manifest targeted by Reference was not found: " + r.Uri.Substring (1));
 220                                         doc.AppendChild (doc.ImportNode (xel, true));
 221                                         FixupNamespaceNodes (xel, doc.DocumentElement, false);
 222                                 }
 223                         }
 224                         else if (xmlResolver != null) {
 225                                 // TODO: need testing
 226                                 Stream s = (Stream) xmlResolver.GetEntity (new Uri (r.Uri), null, typeof (Stream));
 227                                 doc.Load (s);
 228                         }
 229
 230                         if (doc.FirstChild != null) {
 231                                 // keep a copy of the manifests to check their references later
 232                                 if (manifests == null)
 233                                         manifests = new ArrayList ();
 234                                 manifests.Add (doc);
 235
 236                                 return doc;
 237                         }
 238                         return null;
 239                 }
 240
 241                 private void FixupNamespaceNodes (XmlElement src, XmlElement dst, bool ignoreDefault)
 242                 {
 243                         // add namespace nodes
 244                         foreach (XmlAttribute attr in src.SelectNodes ("namespace::*")) {
 245                                 if (attr.LocalName == "xml")
 246                                         continue;
 247                                 if (ignoreDefault && attr.LocalName == "xmlns")
 248                                         continue;
 249                                 dst.SetAttributeNode (dst.OwnerDocument.ImportNode (attr, true) as XmlAttribute);
 250                         }
 251                 }
 252
 253                 private byte[] GetReferenceHash (Reference r, bool check_hmac)
 254                 {
 255                         Stream s = null;
 256                         XmlDocument doc = null;
 257                         if (r.Uri == String.Empty) {
 258                                 doc = envdoc;
 259                         }
 260                         else if (r.Type == XmlSignature.Uri.Manifest) {
 261                                 doc = GetManifest (r);
 262                         }
 263                         else {
 264                                 doc = new XmlDocument ();
 265                                 doc.PreserveWhitespace = true;
 266                                 string objectName = null;
 267
 268                                 if (r.Uri.StartsWith ("#xpointer")) {
 269                                         string uri = string.Join ("", r.Uri.Substring (9).Split (whitespaceChars));
 270                                         if (uri.Length < 2 || uri [0] != '(' || uri [uri.Length - 1] != ')')
 271                                                 // FIXME: how to handle invalid xpointer?
 272                                                 uri = String.Empty;
 273                                         else
 274                                                 uri = uri.Substring (1, uri.Length - 2);
 275                                         if (uri == "/")
 276                                                 doc = envdoc;
 277                                         else if (uri.Length > 6 && uri.StartsWith ("id(") && uri [uri.Length - 1] == ')')
 278                                                 // id('foo'), id("foo")
 279                                                 objectName = uri.Substring (4, uri.Length - 6);
 280                                 }
 281                                 else if (r.Uri [0] == '#') {
 282                                         objectName = r.Uri.Substring (1);
 283                                 }
 284                                 else if (xmlResolver != null) {
 285                                         // TODO: test but doc says that Resolver = null -> no access
 286                                         try {
 287                                                 // no way to know if valid without throwing an exception
 288                                                 Uri uri = new Uri (r.Uri);
 289                                                 s = (Stream) xmlResolver.GetEntity (uri, null, typeof (Stream));
 290                                         }
 291                                         catch {
 292                                                 // may still be a local file (and maybe not xml)
 293                                                 s = File.OpenRead (r.Uri);
 294                                         }
 295                                 }
 296                                 if (objectName != null) {
 297                                         XmlElement found = null;
 298                                         foreach (DataObject obj in m_signature.ObjectList) {
 299                                                 if (obj.Id == objectName) {
 300                                                         found = obj.GetXml ();
 301                                                         found.SetAttribute ("xmlns", SignedXml.XmlDsigNamespaceUrl);
 302                                                         doc.AppendChild (doc.ImportNode (found, true));
 303                                                         // FIXME: there should be theoretical justification of copying namespace declaration nodes this way.
 304                                                         foreach (XmlNode n in found.ChildNodes)
 305                                                                 // Do not copy default namespace as it must be xmldsig namespace for "Object" element.
 306                                                                 if (n.NodeType == XmlNodeType.Element)
 307                                                                         FixupNamespaceNodes (n as XmlElement, doc.DocumentElement, true);
 308                                                         break;
 309                                                 }
 310                                         }
 311                                         if (found == null && envdoc != null) {
 312                                                 found = GetIdElement (envdoc, objectName);
 313                                                 if (found != null) {
 314                                                         doc.AppendChild (doc.ImportNode (found, true));
 315                                                         FixupNamespaceNodes (found, doc.DocumentElement, false);
 316                                                 }
 317                                         }
 318                                         if (found == null)
 319                                                 throw new CryptographicException (String.Format ("Malformed reference object: {0}", objectName));
 320                                 }
 321                         }
 322
 323                         if (r.TransformChain.Count > 0) {
 324                                 foreach (Transform t in r.TransformChain) {
 325                                         if (s == null) {
 326                                                 s = ApplyTransform (t, doc);
 327                                         }
 328                                         else {
 329                                                 t.LoadInput (s);
 330                                                 object o = t.GetOutput ();
 331                                                 if (o is Stream)
 332                                                         s = (Stream) o;
 333                                                 else
 334                                                         s = CanonicalizeOutput (o);
 335                                         }
 336                                 }
 337                         }
 338                         else if (s == null) {
 339                                 // we must not C14N references from outside the document
 340                                 // e.g. non-xml documents
 341                                 if (r.Uri [0] != '#') {
 342                                         s = new MemoryStream ();
 343                                         doc.Save (s);
 344                                 }
 345                                 else {
 346                                         // apply default C14N transformation
 347                                         s = ApplyTransform (new XmlDsigC14NTransform (), doc);
 348                                 }
 349                         }
 350                         HashAlgorithm digest = GetHash (r.DigestMethod, check_hmac);
 351                         return (digest == null) ? null : digest.ComputeHash (s);
 352                 }
 353
 354                 private void DigestReferences ()
 355                 {
 356                         // we must tell each reference which hash algorithm to use
 357                         // before asking for the SignedInfo XML !
 358                         foreach (Reference r in m_signature.SignedInfo.References) {
 359                                 // assume SHA-1 if nothing is specified
 360                                 if (r.DigestMethod == null)
 361                                         r.DigestMethod = XmlDsigSHA1Url;
 362                                 r.DigestValue = GetReferenceHash (r, false);
 363                         }
 364                 }
 365
 366                 private Transform GetC14NMethod ()
 367                 {
 368                         Transform t = (Transform) CryptoConfig.CreateFromName (m_signature.SignedInfo.CanonicalizationMethod);
 369                         if (t == null)
 370                                 throw new CryptographicException ("Unknown Canonicalization Method {0}", m_signature.SignedInfo.CanonicalizationMethod);
 371                         return t;
 372                 }
 373
 374                 private Stream SignedInfoTransformed ()
 375                 {
 376                         Transform t = GetC14NMethod ();
 377
 378                         if (signatureElement == null) {
 379                                 // when creating signatures
 380                                 XmlDocument doc = new XmlDocument ();
 381                                 doc.PreserveWhitespace = true;
 382                                 doc.LoadXml (m_signature.SignedInfo.GetXml ().OuterXml);
 383                                 if (envdoc != null)
 384                                 foreach (XmlAttribute attr in envdoc.DocumentElement.SelectNodes ("namespace::*")) {
 385                                         if (attr.LocalName == "xml")
 386                                                 continue;
 387                                         if (attr.Prefix == doc.DocumentElement.Prefix)
 388                                                 continue;
 389                                         doc.DocumentElement.SetAttributeNode (doc.ImportNode (attr, true) as XmlAttribute);
 390                                 }
 391                                 t.LoadInput (doc);
 392                         }
 393                         else {
 394                                 // when verifying signatures
 395                                 // TODO - check m_signature.SignedInfo.Id
 396                                 XmlElement el = signatureElement.GetElementsByTagName (XmlSignature.ElementNames.SignedInfo, XmlSignature.NamespaceURI) [0] as XmlElement;
 397                                 StringWriter sw = new StringWriter ();
 398                                 XmlTextWriter xtw = new XmlTextWriter (sw);
 399                                 xtw.WriteStartElement (el.Prefix, el.LocalName, el.NamespaceURI);
 400
 401                                 // context namespace nodes (except for "xmlns:xml")
 402                                 XmlNodeList nl = el.SelectNodes ("namespace::*");
 403                                 foreach (XmlAttribute attr in nl) {
 404                                         if (attr.ParentNode == el)
 405                                                 continue;
 406                                         if (attr.LocalName == "xml")
 407                                                 continue;
 408                                         if (attr.Prefix == el.Prefix)
 409                                                 continue;
 410                                         attr.WriteTo (xtw);
 411                                 }
 412                                 foreach (XmlNode attr in el.Attributes)
 413                                         attr.WriteTo (xtw);
 414                                 foreach (XmlNode n in el.ChildNodes)
 415                                         n.WriteTo (xtw);
 416
 417                                 xtw.WriteEndElement ();
 418                                 byte [] si = Encoding.UTF8.GetBytes (sw.ToString ());
 419
 420                                 MemoryStream ms = new MemoryStream ();
 421                                 ms.Write (si, 0, si.Length);
 422                                 ms.Position = 0;
 423
 424                                 t.LoadInput (ms);
 425                         }
 426                         // C14N and C14NWithComments always return a Stream in GetOutput
 427                         return (Stream) t.GetOutput ();
 428                 }
 429
 430                 // reuse hash - most document will always use the same hash
 431                 private HashAlgorithm GetHash (string algorithm, bool check_hmac)
 432                 {
 433                         HashAlgorithm hash = (HashAlgorithm) hashes [algorithm];
 434                         if (hash == null) {
 435                                 hash = HashAlgorithm.Create (algorithm);
 436                                 if (hash == null)
 437                                         throw new CryptographicException ("Unknown hash algorithm: {0}", algorithm);
 438                                 hashes.Add (algorithm, hash);
 439                                 // now ready to be used
 440                         }
 441                         else {
 442                                 // important before reusing an hash object
 443                                 hash.Initialize ();
 444                         }
 445                         // we can sign using any hash algorith, including HMAC, but we can only verify hash (MS compatibility)
 446                         if (check_hmac && (hash is KeyedHashAlgorithm))
 447                                 return null;
 448                         return hash;
 449                 }
 450
 451                 public bool CheckSignature ()
 452                 {
 453                         return (CheckSignatureInternal (null) != null);
 454                 }
 455
 456                 private bool CheckReferenceIntegrity (ArrayList referenceList)
 457                 {
 458                         if (referenceList == null)
 459                                 return false;
 460
 461                         // check digest (hash) for every reference
 462                         foreach (Reference r in referenceList) {
 463                                 // stop at first broken reference
 464                                 byte[] hash = GetReferenceHash (r, true);
 465                                 if (! Compare (r.DigestValue, hash))
 466                                         return false;
 467                         }
 468                         return true;
 469                 }
 470
 471                 public bool CheckSignature (AsymmetricAlgorithm key)
 472                 {
 473                         if (key == null)
 474                                 throw new ArgumentNullException ("key");
 475                         return (CheckSignatureInternal (key) != null);
 476                 }
 477
 478                 private AsymmetricAlgorithm CheckSignatureInternal (AsymmetricAlgorithm key)
 479                 {
 480                         pkEnumerator = null;
 481
 482                         if (key != null) {
 483                                 // check with supplied key
 484                                 if (!CheckSignatureWithKey (key))
 485                                         return null;
 486                         } else {
 487                                 if (Signature.KeyInfo == null)
 488                                         return null;
 489                                 // no supplied key, iterates all KeyInfo
 490                                 while ((key = GetPublicKey ()) != null) {
 491                                         if (CheckSignatureWithKey (key)) {
 492                                                 break;
 493                                         }
 494                                 }
 495                                 pkEnumerator = null;
 496                                 if (key == null)
 497                                         return null;
 498                         }
 499
 500                         // some parts may need to be downloaded
 501                         // so where doing it last
 502                         if (!CheckReferenceIntegrity (m_signature.SignedInfo.References))
 503                                 return null;
 504
 505                         if (manifests != null) {
 506                                 // do not use foreach as a manifest could contain manifests...
 507                                 for (int i=0; i < manifests.Count; i++) {
 508                                         Manifest manifest = new Manifest ((manifests [i] as XmlDocument).DocumentElement);
 509                                         if (! CheckReferenceIntegrity (manifest.References))
 510                                                 return null;
 511                                 }
 512                         }
 513                         return key;
 514                 }
 515
 516                 // Is the signature (over SignedInfo) valid ?
 517                 private bool CheckSignatureWithKey (AsymmetricAlgorithm key)
 518                 {
 519                         if (key == null)
 520                                 return false;
 521
 522                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 523                         if (sd == null)
 524                                 return false;
 525
 526                         AsymmetricSignatureDeformatter verifier = (AsymmetricSignatureDeformatter) CryptoConfig.CreateFromName (sd.DeformatterAlgorithm);
 527                         if (verifier == null)
 528                                 return false;
 529
 530                         try {
 531                                 verifier.SetKey (key);
 532                                 verifier.SetHashAlgorithm (sd.DigestAlgorithm);
 533
 534                                 HashAlgorithm hash = GetHash (sd.DigestAlgorithm, true);
 535                                 // get the hash of the C14N SignedInfo element
 536                                 MemoryStream ms = (MemoryStream) SignedInfoTransformed ();
 537
 538                                 byte[] digest = hash.ComputeHash (ms);
 539                                 return verifier.VerifySignature (digest, m_signature.SignatureValue);
 540                         }
 541                         catch {
 542                                 // e.g. SignatureMethod != AsymmetricAlgorithm type
 543                                 return false;
 544                         }
 545                 }
 546
 547                 private bool Compare (byte[] expected, byte[] actual)
 548                 {
 549                         bool result = ((expected != null) && (actual != null));
 550                         if (result) {
 551                                 int l = expected.Length;
 552                                 result = (l == actual.Length);
 553                                 if (result) {
 554                                         for (int i=0; i < l; i++) {
 555                                                 if (expected[i] != actual[i])
 556                                                         return false;
 557                                         }
 558                                 }
 559                         }
 560                         return result;
 561                 }
 562
 563                 public bool CheckSignature (KeyedHashAlgorithm macAlg)
 564                 {
 565                         if (macAlg == null)
 566                                 throw new ArgumentNullException ("macAlg");
 567
 568                         pkEnumerator = null;
 569
 570                         // Is the signature (over SignedInfo) valid ?
 571                         Stream s = SignedInfoTransformed ();
 572                         if (s == null)
 573                                 return false;
 574
 575                         byte[] actual = macAlg.ComputeHash (s);
 576                         // HMAC signature may be partial and specified by <HMACOutputLength>
 577                         if (m_signature.SignedInfo.SignatureLength != null) {
 578                                 int length = Int32.Parse (m_signature.SignedInfo.SignatureLength);
 579                                 // we only support signatures with a multiple of 8 bits
 580                                 // and the value must match the signature length
 581                                 if ((length & 7) != 0)
 582                                         throw new CryptographicException ("Signature length must be a multiple of 8 bits.");
 583
 584                                 // SignatureLength is in bits (and we works on bytes, only in multiple of 8 bits)
 585                                 // and both values must match for a signature to be valid
 586                                 length >>= 3;
 587                                 if (length != m_signature.SignatureValue.Length)
 588                                         throw new CryptographicException ("Invalid signature length.");
 589
 590                                 // is the length "big" enough to make the signature meaningful ?
 591                                 // we use a minimum of 80 bits (10 bytes) or half the HMAC normal output length
 592                                 // e.g. HMACMD5 output 128 bits but our minimum is 80 bits (not 64 bits)
 593                                 int minimum = Math.Max (10, actual.Length / 2);
 594                                 if (length < minimum)
 595                                         throw new CryptographicException ("HMAC signature is too small");
 596
 597                                 if (length < actual.Length) {
 598                                         byte[] trunked = new byte [length];
 599                                         Buffer.BlockCopy (actual, 0, trunked, 0, length);
 600                                         actual = trunked;
 601                                 }
 602                         }
 603
 604                         if (Compare (m_signature.SignatureValue, actual)) {
 605                                 // some parts may need to be downloaded
 606                                 // so where doing it last
 607                                 return CheckReferenceIntegrity (m_signature.SignedInfo.References);
 608                         }
 609                         return false;
 610                 }
 611
 612                 [MonoTODO]
 613                 [ComVisible (false)]
 614                 public bool CheckSignature (X509Certificate2 certificate, bool verifySignatureOnly)
 615                 {
 616                         throw new NotImplementedException ();
 617                 }
 618
 619                 public bool CheckSignatureReturningKey (out AsymmetricAlgorithm signingKey)
 620                 {
 621                         signingKey = CheckSignatureInternal (null);
 622                         return (signingKey != null);
 623                 }
 624
 625                 public void ComputeSignature ()
 626                 {
 627                         if (key != null) {
 628                                 if (m_signature.SignedInfo.SignatureMethod == null)
 629                                         // required before hashing
 630                                         m_signature.SignedInfo.SignatureMethod = key.SignatureAlgorithm;
 631                                 else if (m_signature.SignedInfo.SignatureMethod != key.SignatureAlgorithm)
 632                                         throw new CryptographicException ("Specified SignatureAlgorithm is not supported by the signing key.");
 633                                 DigestReferences ();
 634
 635                                 AsymmetricSignatureFormatter signer = null;
 636                                 // in need for a CryptoConfig factory
 637                                 if (key is DSA)
 638                                         signer = new DSASignatureFormatter (key);
 639                                 else if (key is RSA)
 640                                         signer = new RSAPKCS1SignatureFormatter (key);
 641
 642                                 if (signer != null) {
 643                                         SignatureDescription sd = (SignatureDescription) CryptoConfig.CreateFromName (m_signature.SignedInfo.SignatureMethod);
 644
 645                                         HashAlgorithm hash = GetHash (sd.DigestAlgorithm, false);
 646                                         // get the hash of the C14N SignedInfo element
 647                                         byte[] digest = hash.ComputeHash (SignedInfoTransformed ());
 648
 649                                         signer.SetHashAlgorithm ("SHA1");
 650                                         m_signature.SignatureValue = signer.CreateSignature (digest);
 651                                 }
 652                         }
 653                         else
 654                                 throw new CryptographicException ("signing key is not specified");
 655                 }
 656
 657                 public void ComputeSignature (KeyedHashAlgorithm macAlg)
 658                 {
 659                         if (macAlg == null)
 660                                 throw new ArgumentNullException ("macAlg");
 661
 662                         string method = null;
 663
 664                         if (macAlg is HMACSHA1) {
 665                                 method = XmlDsigHMACSHA1Url;
 666                         } else if (macAlg is HMACSHA256) {
 667                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha256";
 668                         } else if (macAlg is HMACSHA384) {
 669                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha384";
 670                         } else if (macAlg is HMACSHA512) {
 671                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-sha512";
 672                         } else if (macAlg is HMACRIPEMD160) {
 673                                 method = "http://www.w3.org/2001/04/xmldsig-more#hmac-ripemd160";
 674                         }
 675
 676                         if (method == null)
 677                                 throw new CryptographicException ("unsupported algorithm");
 678
 679                         DigestReferences ();
 680                         m_signature.SignedInfo.SignatureMethod = method;
 681                         m_signature.SignatureValue = macAlg.ComputeHash (SignedInfoTransformed ());
 682                 }
 683
 684                 public virtual XmlElement GetIdElement (XmlDocument document, string idValue)
 685                 {
 686                         if ((document == null) || (idValue == null))
 687                                 return null;
 688
 689                         // this works only if there's a DTD or XSD available to define the ID
 690                         XmlElement xel = document.GetElementById (idValue);
 691                         if (xel == null) {
 692                                 // search an "undefined" ID
 693                                 xel = (XmlElement) document.SelectSingleNode ("//*[@Id='" + idValue + "']");
 694                                 if (xel == null) {
 695                                         xel = (XmlElement) document.SelectSingleNode ("//*[@ID='" + idValue + "']");
 696                                         if (xel == null) {
 697                                                 xel = (XmlElement) document.SelectSingleNode ("//*[@id='" + idValue + "']");
 698                                         }
 699                                 }
 700                         }
 701                         return xel;
 702                 }
 703
 704                 // According to book ".NET Framework Security" this method
 705                 // iterates all possible keys then return null
 706                 protected virtual AsymmetricAlgorithm GetPublicKey ()
 707                 {
 708                         if (m_signature.KeyInfo == null)
 709                                 return null;
 710
 711                         if (pkEnumerator == null) {
 712                                 pkEnumerator = m_signature.KeyInfo.GetEnumerator ();
 713                         }
 714
 715 #if SECURITY_DEP
 716                         if (_x509Enumerator != null) {
 717                                 if (_x509Enumerator.MoveNext ()) {
 718                                         X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 719                                         return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 720                                 } else {
 721                                         _x509Enumerator = null;
 722                                 }
 723                         }
 724 #endif
 725                         while (pkEnumerator.MoveNext ()) {
 726                                 AsymmetricAlgorithm key = null;
 727                                 KeyInfoClause kic = (KeyInfoClause) pkEnumerator.Current;
 728
 729                                 if (kic is DSAKeyValue)
 730                                         key = DSA.Create ();
 731                                 else if (kic is RSAKeyValue)
 732                                         key = RSA.Create ();
 733
 734                                 if (key != null) {
 735                                         key.FromXmlString (kic.GetXml ().InnerXml);
 736                                         return key;
 737                                 }
 738
 739 #if SECURITY_DEP
 740                                 if (kic is KeyInfoX509Data) {
 741                                         _x509Enumerator = ((KeyInfoX509Data) kic).Certificates.GetEnumerator ();
 742                                         if (_x509Enumerator.MoveNext ()) {
 743                                                 X509Certificate cert = (X509Certificate) _x509Enumerator.Current;
 744                                                 return new X509Certificate2 (cert.GetRawCertData ()).PublicKey.Key;
 745                                         }
 746                                 }
 747 #endif
 748                         }
 749                         return null;
 750                 }
 751
 752                 public XmlElement GetXml ()
 753                 {
 754                         return m_signature.GetXml (envdoc);
 755                 }
 756
 757                 public void LoadXml (XmlElement value)
 758                 {
 759                         if (value == null)
 760                                 throw new ArgumentNullException ("value");
 761
 762                         signatureElement = value;
 763                         m_signature.LoadXml (value);
 764                         // Need to give the EncryptedXml object to the
 765                         // XmlDecryptionTransform to give it a fighting
 766                         // chance at decrypting the document.
 767                         foreach (Reference r in m_signature.SignedInfo.References) {
 768                                 foreach (Transform t in r.TransformChain) {
 769                                         if (t is XmlDecryptionTransform)
 770                                                 ((XmlDecryptionTransform) t).EncryptedXml = EncryptedXml;
 771                                 }
 772                         }
 773                 }
 774
 775                 [ComVisible (false)]
 776                 public XmlResolver Resolver {
 777                         set { xmlResolver = value; }
 778                 }
 779         }
 780 }