mcs/class/corlib/Mono.Security.Authenticode/AuthenticodeDeformatter.cs

   1 //
   2 // AuthenticodeDeformatter.cs: Authenticode signature validator
   3 //
   4 // Author:
   5 //      Sebastien Pouliot <sebastien@ximian.com>
   6 //
   7 // (C) 2003 Motus Technologies Inc. (http://www.motus.com)
   8 // Copyright (C) 2004-2006 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System;
  31 using System.IO;
  32 using System.Runtime.InteropServices;
  33 using System.Security;
  34 using System.Security.Cryptography;
  35
  36 using Mono.Security.Cryptography;
  37 using Mono.Security.X509;
  38
  39 namespace Mono.Security.Authenticode {
  40
  41         // References:
  42         // a.   http://www.cs.auckland.ac.nz/~pgut001/pubs/authenticode.txt
  43
  44 #if INSIDE_CORLIB
  45         internal
  46 #else
  47         public
  48 #endif
  49         class AuthenticodeDeformatter : AuthenticodeBase {
  50
  51                 private string filename;
  52                 private byte[] hash;
  53                 private X509CertificateCollection coll;
  54                 private ASN1 signedHash;
  55                 private DateTime timestamp;
  56                 private X509Certificate signingCertificate;
  57                 private int reason;
  58                 private bool trustedRoot;
  59                 private bool trustedTimestampRoot;
  60                 private byte[] entry;
  61
  62                 private X509Chain signerChain;
  63                 private X509Chain timestampChain;
  64
  65                 public AuthenticodeDeformatter () : base ()
  66                 {
  67                         reason = -1;
  68                         signerChain = new X509Chain ();
  69                         timestampChain = new X509Chain ();
  70                 }
  71
  72                 public AuthenticodeDeformatter (string fileName) : this ()
  73                 {
  74                         FileName = fileName;
  75                 }
  76
  77                 public string FileName {
  78                         get { return filename; }
  79                         set {
  80                                 Reset ();
  81                                 try {
  82                                         CheckSignature (value);
  83                                 }
  84                                 catch (SecurityException) {
  85                                         throw;
  86                                 }
  87                                 catch (Exception) {
  88                                         reason = 1;
  89                                 }
  90                         }
  91                 }
  92
  93                 public byte[] Hash {
  94                         get {
  95                                 if (signedHash == null)
  96                                         return null;
  97                                 return (byte[]) signedHash.Value.Clone ();
  98                         }
  99                 }
 100
 101                 public int Reason {
 102                         get {
 103                                 if (reason == -1)
 104                                         IsTrusted ();
 105                                 return reason;
 106                         }
 107                 }
 108
 109                 public bool IsTrusted ()
 110                 {
 111                         if (entry == null) {
 112                                 reason = 1;
 113                                 return false;
 114                         }
 115
 116                         if (signingCertificate == null) {
 117                                 reason = 7;
 118                                 return false;
 119                         }
 120
 121                         if ((signerChain.Root == null) || !trustedRoot) {
 122                                 reason = 6;
 123                                 return false;
 124                         }
 125
 126                         if (timestamp != DateTime.MinValue) {
 127                                 if ((timestampChain.Root == null) || !trustedTimestampRoot) {
 128                                         reason = 6;
 129                                         return false;
 130                                 }
 131
 132                                 // check that file was timestamped when certificates were valid
 133                                 if (!signingCertificate.WasCurrent (Timestamp)) {
 134                                         reason = 4;
 135                                         return false;
 136                                 }
 137                         }
 138                         else if (!signingCertificate.IsCurrent) {
 139                                 // signature only valid if the certificate is valid
 140                                 reason = 8;
 141                                 return false;
 142                         }
 143
 144                         if (reason == -1)
 145                                 reason = 0;
 146                         return true;
 147                 }
 148
 149                 public byte[] Signature {
 150                         get {
 151                                 if (entry == null)
 152                                         return null;
 153                                 return (byte[]) entry.Clone ();
 154                         }
 155                 }
 156
 157                 public DateTime Timestamp {
 158                         get { return timestamp; }
 159                 }
 160
 161                 public X509CertificateCollection Certificates {
 162                         get { return coll; }
 163                 }
 164
 165                 public X509Certificate SigningCertificate {
 166                         get { return signingCertificate; }
 167                 }
 168
 169                 private bool CheckSignature (string fileName)
 170                 {
 171                         filename = fileName;
 172                         Open (filename);
 173                         entry = GetSecurityEntry ();
 174                         if (entry == null) {
 175                                 // no signature is present
 176                                 reason = 1;
 177                                 Close ();
 178                                 return false;
 179                         }
 180
 181                         PKCS7.ContentInfo ci = new PKCS7.ContentInfo (entry);
 182                         if (ci.ContentType != PKCS7.Oid.signedData) {
 183                                 Close ();
 184                                 return false;
 185                         }
 186
 187                         PKCS7.SignedData sd = new PKCS7.SignedData (ci.Content);
 188                         if (sd.ContentInfo.ContentType != spcIndirectDataContext) {
 189                                 Close ();
 190                                 return false;
 191                         }
 192
 193                         coll = sd.Certificates;
 194
 195                         ASN1 spc = sd.ContentInfo.Content;
 196                         signedHash = spc [0][1][1];
 197
 198                         HashAlgorithm ha = null;
 199                         switch (signedHash.Length) {
 200                                 case 16:
 201                                         ha = HashAlgorithm.Create ("MD5");
 202                                         hash = GetHash (ha);
 203                                         break;
 204                                 case 20:
 205                                         ha = HashAlgorithm.Create ("SHA1");
 206                                         hash = GetHash (ha);
 207                                         break;
 208                                 default:
 209                                         reason = 5;
 210                                         Close ();
 211                                         return false;
 212                         }
 213                         Close ();
 214
 215                         if (!signedHash.CompareValue (hash)) {
 216                                 reason = 2;
 217                         }
 218
 219                         // messageDigest is a hash of spcIndirectDataContext (which includes the file hash)
 220                         byte[] spcIDC = spc [0].Value;
 221                         ha.Initialize (); // re-using hash instance
 222                         byte[] messageDigest = ha.ComputeHash (spcIDC);
 223
 224                         bool sign = VerifySignature (sd, messageDigest, ha);
 225                         return (sign && (reason == 0));
 226                 }
 227
 228                 private bool CompareIssuerSerial (string issuer, byte[] serial, X509Certificate x509)
 229                 {
 230                         if (issuer != x509.IssuerName)
 231                                 return false;
 232                         if (serial.Length != x509.SerialNumber.Length)
 233                                 return false;
 234                         // MS shows the serial number inversed (so is Mono.Security.X509.X509Certificate)
 235                         int n = serial.Length;
 236                         for (int i=0; i < serial.Length; i++) {
 237                                 if (serial [i] != x509.SerialNumber [--n])
 238                                         return false;
 239                         }
 240                         // must be true
 241                         return true;
 242                 }
 243
 244                 //private bool VerifySignature (ASN1 cs, byte[] calculatedMessageDigest, string hashName)
 245                 private bool VerifySignature (PKCS7.SignedData sd, byte[] calculatedMessageDigest, HashAlgorithm ha)
 246                 {
 247                         string contentType = null;
 248                         ASN1 messageDigest = null;
 249 //                      string spcStatementType = null;
 250 //                      string spcSpOpusInfo = null;
 251
 252                         for (int i=0; i < sd.SignerInfo.AuthenticatedAttributes.Count; i++) {
 253                                 ASN1 attr = (ASN1) sd.SignerInfo.AuthenticatedAttributes [i];
 254                                 string oid = ASN1Convert.ToOid (attr[0]);
 255                                 switch (oid) {
 256                                         case "1.2.840.113549.1.9.3":
 257                                                 // contentType
 258                                                 contentType = ASN1Convert.ToOid (attr[1][0]);
 259                                                 break;
 260                                         case "1.2.840.113549.1.9.4":
 261                                                 // messageDigest
 262                                                 messageDigest = attr[1][0];
 263                                                 break;
 264                                         case "1.3.6.1.4.1.311.2.1.11":
 265                                                 // spcStatementType (Microsoft code signing)
 266                                                 // possible values
 267                                                 // - individualCodeSigning (1 3 6 1 4 1 311 2 1 21)
 268                                                 // - commercialCodeSigning (1 3 6 1 4 1 311 2 1 22)
 269 //                                              spcStatementType = ASN1Convert.ToOid (attr[1][0][0]);
 270                                                 break;
 271                                         case "1.3.6.1.4.1.311.2.1.12":
 272                                                 // spcSpOpusInfo (Microsoft code signing)
 273 /*                                              try {
 274                                                         spcSpOpusInfo = System.Text.Encoding.UTF8.GetString (attr[1][0][0][0].Value);
 275                                                 }
 276                                                 catch (NullReferenceException) {
 277                                                         spcSpOpusInfo = null;
 278                                                 }*/
 279                                                 break;
 280                                         default:
 281                                                 break;
 282                                 }
 283                         }
 284                         if (contentType != spcIndirectDataContext)
 285                                 return false;
 286
 287                         // verify message digest
 288                         if (messageDigest == null)
 289                                 return false;
 290                         if (!messageDigest.CompareValue (calculatedMessageDigest))
 291                                 return false;
 292
 293                         // verify signature
 294                         string hashOID = CryptoConfig.MapNameToOID (ha.ToString ());
 295
 296                         // change to SET OF (not [0]) as per PKCS #7 1.5
 297                         ASN1 aa = new ASN1 (0x31);
 298                         foreach (ASN1 a in sd.SignerInfo.AuthenticatedAttributes)
 299                                 aa.Add (a);
 300                         ha.Initialize ();
 301                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 302
 303                         byte[] signature = sd.SignerInfo.Signature;
 304                         // we need to find the specified certificate
 305                         string issuer = sd.SignerInfo.IssuerName;
 306                         byte[] serial = sd.SignerInfo.SerialNumber;
 307                         foreach (X509Certificate x509 in coll) {
 308                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 309                                         // don't verify is key size don't match
 310                                         if (x509.PublicKey.Length > (signature.Length >> 3)) {
 311                                                 // return the signing certificate even if the signature isn't correct
 312                                                 // (required behaviour for 2.0 support)
 313                                                 signingCertificate = x509;
 314                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 315                                                 if (rsa.VerifyHash (p7hash, hashOID, signature)) {
 316                                                         signerChain.LoadCertificates (coll);
 317                                                         trustedRoot = signerChain.Build (x509);
 318                                                         break;
 319                                                 }
 320                                         }
 321                                 }
 322                         }
 323
 324                         // timestamp signature is optional
 325                         if (sd.SignerInfo.UnauthenticatedAttributes.Count == 0) {
 326                                 trustedTimestampRoot = true;
 327                         }  else {
 328                                 for (int i = 0; i < sd.SignerInfo.UnauthenticatedAttributes.Count; i++) {
 329                                         ASN1 attr = (ASN1) sd.SignerInfo.UnauthenticatedAttributes[i];
 330                                         string oid = ASN1Convert.ToOid (attr[0]);
 331                                         switch (oid) {
 332                                         case PKCS7.Oid.countersignature:
 333                                                 // SEQUENCE {
 334                                                 //   OBJECT IDENTIFIER
 335                                                 //     countersignature (1 2 840 113549 1 9 6)
 336                                                 //   SET {
 337                                                 PKCS7.SignerInfo cs = new PKCS7.SignerInfo (attr[1]);
 338                                                 trustedTimestampRoot = VerifyCounterSignature (cs, signature);
 339                                                 break;
 340                                         default:
 341                                                 // we don't support other unauthenticated attributes
 342                                                 break;
 343                                         }
 344                                 }
 345                         }
 346
 347                         return (trustedRoot && trustedTimestampRoot);
 348                 }
 349
 350                 private bool VerifyCounterSignature (PKCS7.SignerInfo cs, byte[] signature)
 351                 {
 352                         // SEQUENCE {
 353                         //   INTEGER 1
 354                         if (cs.Version != 1)
 355                                 return false;
 356                         //   SEQUENCE {
 357                         //      SEQUENCE {
 358
 359                         string contentType = null;
 360                         ASN1 messageDigest = null;
 361                         for (int i=0; i < cs.AuthenticatedAttributes.Count; i++) {
 362                                 // SEQUENCE {
 363                                 //   OBJECT IDENTIFIER
 364                                 ASN1 attr = (ASN1) cs.AuthenticatedAttributes [i];
 365                                 string oid = ASN1Convert.ToOid (attr[0]);
 366                                 switch (oid) {
 367                                         case "1.2.840.113549.1.9.3":
 368                                                 // contentType
 369                                                 contentType = ASN1Convert.ToOid (attr[1][0]);
 370                                                 break;
 371                                         case "1.2.840.113549.1.9.4":
 372                                                 // messageDigest
 373                                                 messageDigest = attr[1][0];
 374                                                 break;
 375                                         case "1.2.840.113549.1.9.5":
 376                                                 // SEQUENCE {
 377                                                 //   OBJECT IDENTIFIER
 378                                                 //     signingTime (1 2 840 113549 1 9 5)
 379                                                 //   SET {
 380                                                 //     UTCTime '030124013651Z'
 381                                                 //   }
 382                                                 // }
 383                                                 timestamp = ASN1Convert.ToDateTime (attr[1][0]);
 384                                                 break;
 385                                         default:
 386                                                 break;
 387                                 }
 388                         }
 389
 390                         if (contentType != PKCS7.Oid.data)
 391                                 return false;
 392
 393                         // verify message digest
 394                         if (messageDigest == null)
 395                                 return false;
 396                         // TODO: must be read from the ASN.1 structure
 397                         string hashName = null;
 398                         switch (messageDigest.Length) {
 399                                 case 16:
 400                                         hashName = "MD5";
 401                                         break;
 402                                 case 20:
 403                                         hashName = "SHA1";
 404                                         break;
 405                         }
 406                         HashAlgorithm ha = HashAlgorithm.Create (hashName);
 407                         if (!messageDigest.CompareValue (ha.ComputeHash (signature)))
 408                                 return false;
 409
 410                         // verify signature
 411                         byte[] counterSignature = cs.Signature;
 412
 413                         // change to SET OF (not [0]) as per PKCS #7 1.5
 414                         ASN1 aa = new ASN1 (0x31);
 415                         foreach (ASN1 a in cs.AuthenticatedAttributes)
 416                                 aa.Add (a);
 417                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 418
 419                         // we need to try all certificates
 420                         string issuer = cs.IssuerName;
 421                         byte[] serial = cs.SerialNumber;
 422                         foreach (X509Certificate x509 in coll) {
 423                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 424                                         if (x509.PublicKey.Length > counterSignature.Length) {
 425                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 426                                                 // we need to HACK around bad (PKCS#1 1.5) signatures made by Verisign Timestamp Service
 427                                                 // and this means copying stuff into our own RSAManaged to get the required flexibility
 428                                                 RSAManaged rsam = new RSAManaged ();
 429                                                 rsam.ImportParameters (rsa.ExportParameters (false));
 430                                                 if (PKCS1.Verify_v15 (rsam, ha, p7hash, counterSignature, true)) {
 431                                                         timestampChain.LoadCertificates (coll);
 432                                                         return (timestampChain.Build (x509));
 433                                                 }
 434                                         }
 435                                 }
 436                         }
 437                         // no certificate can verify this signature!
 438                         return false;
 439                 }
 440
 441                 private void Reset ()
 442                 {
 443                         filename = null;
 444                         entry = null;
 445                         hash = null;
 446                         signedHash = null;
 447                         signingCertificate = null;
 448                         reason = -1;
 449                         trustedRoot = false;
 450                         trustedTimestampRoot = false;
 451                         signerChain.Reset ();
 452                         timestampChain.Reset ();
 453                         timestamp = DateTime.MinValue;
 454                 }
 455         }
 456 }