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) 2004-2005 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.X509;
  37
  38 namespace Mono.Security.Authenticode {
  39
  40         // References:
  41         // a.   http://www.cs.auckland.ac.nz/~pgut001/pubs/authenticode.txt
  42
  43 #if INSIDE_CORLIB
  44         internal
  45 #else
  46         public
  47 #endif
  48         class AuthenticodeDeformatter : AuthenticodeBase {
  49
  50                 private string filename;
  51                 private byte[] hash;
  52                 private X509CertificateCollection coll;
  53                 private ASN1 signedHash;
  54                 private DateTime timestamp;
  55                 private X509Certificate signingCertificate;
  56                 private int reason;
  57                 private bool trustedRoot;
  58                 private bool trustedTimestampRoot;
  59                 private byte[] entry;
  60
  61                 private X509Chain signerChain;
  62                 private X509Chain timestampChain;
  63
  64                 public AuthenticodeDeformatter () : base ()
  65                 {
  66                         reason = -1;
  67                         signerChain = new X509Chain ();
  68                         timestampChain = new X509Chain ();
  69                 }
  70
  71                 public AuthenticodeDeformatter (string fileName) : this ()
  72                 {
  73                         FileName = fileName;
  74                 }
  75
  76                 public string FileName {
  77                         get { return filename; }
  78                         set {
  79                                 Reset ();
  80                                 try {
  81                                         CheckSignature (value);
  82                                 }
  83                                 catch (SecurityException) {
  84                                         throw;
  85                                 }
  86                                 catch (Exception) {
  87                                         reason = 1;
  88                                 }
  89                         }
  90                 }
  91
  92                 public byte[] Hash {
  93                         get {
  94                                 if (signedHash == null)
  95                                         return null;
  96                                 return (byte[]) signedHash.Value.Clone ();
  97                         }
  98                 }
  99
 100                 public int Reason {
 101                         get {
 102                                 if (reason == -1)
 103                                         IsTrusted ();
 104                                 return reason;
 105                         }
 106                 }
 107
 108                 public bool IsTrusted ()
 109                 {
 110                         if (entry == null) {
 111                                 reason = 1;
 112                                 return false;
 113                         }
 114
 115                         if (signingCertificate == null) {
 116                                 reason = 7;
 117                                 return false;
 118                         }
 119
 120                         if ((signerChain.Root == null) || !trustedRoot) {
 121                                 reason = 6;
 122                                 return false;
 123                         }
 124
 125                         if (timestamp != DateTime.MinValue) {
 126                                 if ((timestampChain.Root == null) || !trustedTimestampRoot) {
 127                                         reason = 6;
 128                                         return false;
 129                                 }
 130
 131                                 // check that file was timestamped when certificates were valid
 132                                 if (!signingCertificate.WasCurrent (Timestamp)) {
 133                                         reason = 4;
 134                                         return false;
 135                                 }
 136                         }
 137                         else if (!signingCertificate.IsCurrent) {
 138                                 // signature only valid if the certificate is valid
 139                                 reason = 8;
 140                                 return false;
 141                         }
 142
 143                         reason = 0;
 144                         return true;
 145                 }
 146
 147                 public byte[] Signature {
 148                         get {
 149                                 if (entry == null)
 150                                         return null;
 151                                 return (byte[]) entry.Clone ();
 152                         }
 153                 }
 154
 155                 public DateTime Timestamp {
 156                         get { return timestamp; }
 157                 }
 158
 159                 public X509CertificateCollection Certificates {
 160                         get { return coll; }
 161                 }
 162
 163                 public X509Certificate SigningCertificate {
 164                         get { return signingCertificate; }
 165                 }
 166
 167                 private bool CheckSignature (string fileName)
 168                 {
 169                         filename = fileName;
 170                         base.Open (filename);
 171                         entry = base.GetSecurityEntry ();
 172                         if (entry == null) {
 173                                 // no signature is present
 174                                 reason = 1;
 175                                 base.Close ();
 176                                 return false;
 177                         }
 178
 179                         PKCS7.ContentInfo ci = new PKCS7.ContentInfo (entry);
 180                         if (ci.ContentType != PKCS7.Oid.signedData) {
 181                                 base.Close ();
 182                                 return false;
 183                         }
 184
 185                         PKCS7.SignedData sd = new PKCS7.SignedData (ci.Content);
 186                         if (sd.ContentInfo.ContentType != spcIndirectDataContext) {
 187                                 base.Close ();
 188                                 return false;
 189                         }
 190
 191                         coll = sd.Certificates;
 192
 193                         ASN1 spc = sd.ContentInfo.Content;
 194                         signedHash = spc [0][1][1];
 195
 196                         HashAlgorithm ha = null;
 197                         switch (signedHash.Length) {
 198                                 case 16:
 199                                         ha = HashAlgorithm.Create ("MD5");
 200                                         hash = GetHash (ha);
 201                                         break;
 202                                 case 20:
 203                                         ha = HashAlgorithm.Create ("SHA1");
 204                                         hash = GetHash (ha);
 205                                         break;
 206                                 default:
 207                                         reason = 5;
 208                                         base.Close ();
 209                                         return false;
 210                         }
 211                         base.Close ();
 212
 213                         if (!signedHash.CompareValue (hash)) {
 214                                 reason = 2;
 215                         }
 216
 217                         // messageDigest is a hash of spcIndirectDataContext (which includes the file hash)
 218                         byte[] spcIDC = spc [0].Value;
 219                         ha.Initialize (); // re-using hash instance
 220                         byte[] messageDigest = ha.ComputeHash (spcIDC);
 221
 222                         bool sign = VerifySignature (sd, messageDigest, ha);
 223                         return (sign && (reason == 0));
 224                 }
 225
 226                 private bool CompareIssuerSerial (string issuer, byte[] serial, X509Certificate x509)
 227                 {
 228                         if (issuer != x509.IssuerName)
 229                                 return false;
 230                         if (serial.Length != x509.SerialNumber.Length)
 231                                 return false;
 232                         // MS shows the serial number inversed (so is Mono.Security.X509.X509Certificate)
 233                         int n = serial.Length;
 234                         for (int i=0; i < serial.Length; i++) {
 235                                 if (serial [i] != x509.SerialNumber [--n])
 236                                         return false;
 237                         }
 238                         // must be true
 239                         return true;
 240                 }
 241
 242                 //private bool VerifySignature (ASN1 cs, byte[] calculatedMessageDigest, string hashName)
 243                 private bool VerifySignature (PKCS7.SignedData sd, byte[] calculatedMessageDigest, HashAlgorithm ha)
 244                 {
 245                         string contentType = null;
 246                         ASN1 messageDigest = null;
 247 //                      string spcStatementType = null;
 248 //                      string spcSpOpusInfo = null;
 249
 250                         for (int i=0; i < sd.SignerInfo.AuthenticatedAttributes.Count; i++) {
 251                                 ASN1 attr = (ASN1) sd.SignerInfo.AuthenticatedAttributes [i];
 252                                 string oid = ASN1Convert.ToOid (attr[0]);
 253                                 switch (oid) {
 254                                         case "1.2.840.113549.1.9.3":
 255                                                 // contentType
 256                                                 contentType = ASN1Convert.ToOid (attr[1][0]);
 257                                                 break;
 258                                         case "1.2.840.113549.1.9.4":
 259                                                 // messageDigest
 260                                                 messageDigest = attr[1][0];
 261                                                 break;
 262                                         case "1.3.6.1.4.1.311.2.1.11":
 263                                                 // spcStatementType (Microsoft code signing)
 264                                                 // possible values
 265                                                 // - individualCodeSigning (1 3 6 1 4 1 311 2 1 21)
 266                                                 // - commercialCodeSigning (1 3 6 1 4 1 311 2 1 22)
 267 //                                              spcStatementType = ASN1Convert.ToOid (attr[1][0][0]);
 268                                                 break;
 269                                         case "1.3.6.1.4.1.311.2.1.12":
 270                                                 // spcSpOpusInfo (Microsoft code signing)
 271 /*                                              try {
 272                                                         spcSpOpusInfo = System.Text.Encoding.UTF8.GetString (attr[1][0][0][0].Value);
 273                                                 }
 274                                                 catch (NullReferenceException) {
 275                                                         spcSpOpusInfo = null;
 276                                                 }*/
 277                                                 break;
 278                                         default:
 279                                                 break;
 280                                 }
 281                         }
 282                         if (contentType != spcIndirectDataContext)
 283                                 return false;
 284
 285                         // verify message digest
 286                         if (messageDigest == null)
 287                                 return false;
 288                         if (!messageDigest.CompareValue (calculatedMessageDigest))
 289                                 return false;
 290
 291                         // verify signature
 292                         string hashOID = CryptoConfig.MapNameToOID (ha.ToString ());
 293
 294                         // change to SET OF (not [0]) as per PKCS #7 1.5
 295                         ASN1 aa = new ASN1 (0x31);
 296                         foreach (ASN1 a in sd.SignerInfo.AuthenticatedAttributes)
 297                                 aa.Add (a);
 298                         ha.Initialize ();
 299                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 300
 301                         byte[] signature = sd.SignerInfo.Signature;
 302                         // we need to find the specified certificate
 303                         string issuer = sd.SignerInfo.IssuerName;
 304                         byte[] serial = sd.SignerInfo.SerialNumber;
 305                         foreach (X509Certificate x509 in coll) {
 306                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 307                                         // don't verify is key size don't match
 308                                         if (x509.PublicKey.Length > (signature.Length >> 3)) {
 309                                                 // return the signing certificate even if the signature isn't correct
 310                                                 // (required behaviour for 2.0 support)
 311                                                 signingCertificate = x509;
 312                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 313                                                 if (rsa.VerifyHash (p7hash, hashOID, signature)) {
 314                                                         signerChain.LoadCertificates (coll);
 315                                                         trustedRoot = signerChain.Build (x509);
 316                                                         break;
 317                                                 }
 318                                         }
 319                                 }
 320                         }
 321
 322                         for (int i=0; i < sd.SignerInfo.UnauthenticatedAttributes.Count; i++) {
 323                                 ASN1 attr = (ASN1) sd.SignerInfo.UnauthenticatedAttributes [i];
 324                                 string oid = ASN1Convert.ToOid (attr [0]);
 325                                 switch (oid) {
 326                                         case PKCS7.Oid.countersignature:
 327                                                 // SEQUENCE {
 328                                                 //   OBJECT IDENTIFIER
 329                                                 //     countersignature (1 2 840 113549 1 9 6)
 330                                                 //   SET {
 331                                                 PKCS7.SignerInfo cs = new PKCS7.SignerInfo (attr [1]);
 332                                                 trustedTimestampRoot = VerifyCounterSignature (cs, signature);
 333                                                 break;
 334                                         default:
 335                                                 // we don't support other unauthenticated attributes
 336                                                 break;
 337                                 }
 338                         }
 339
 340                         return (trustedRoot && trustedTimestampRoot);
 341                 }
 342
 343                 private bool VerifyCounterSignature (PKCS7.SignerInfo cs, byte[] signature)
 344                 {
 345                         // SEQUENCE {
 346                         //   INTEGER 1
 347                         if (cs.Version != 1)
 348                                 return false;
 349                         //   SEQUENCE {
 350                         //      SEQUENCE {
 351
 352                         string contentType = null;
 353                         ASN1 messageDigest = null;
 354                         for (int i=0; i < cs.AuthenticatedAttributes.Count; i++) {
 355                                 // SEQUENCE {
 356                                 //   OBJECT IDENTIFIER
 357                                 ASN1 attr = (ASN1) cs.AuthenticatedAttributes [i];
 358                                 string oid = ASN1Convert.ToOid (attr[0]);
 359                                 switch (oid) {
 360                                         case "1.2.840.113549.1.9.3":
 361                                                 // contentType
 362                                                 contentType = ASN1Convert.ToOid (attr[1][0]);
 363                                                 break;
 364                                         case "1.2.840.113549.1.9.4":
 365                                                 // messageDigest
 366                                                 messageDigest = attr[1][0];
 367                                                 break;
 368                                         case "1.2.840.113549.1.9.5":
 369                                                 // SEQUENCE {
 370                                                 //   OBJECT IDENTIFIER
 371                                                 //     signingTime (1 2 840 113549 1 9 5)
 372                                                 //   SET {
 373                                                 //     UTCTime '030124013651Z'
 374                                                 //   }
 375                                                 // }
 376                                                 timestamp = ASN1Convert.ToDateTime (attr[1][0]);
 377                                                 break;
 378                                         default:
 379                                                 break;
 380                                 }
 381                         }
 382
 383                         if (contentType != PKCS7.Oid.data)
 384                                 return false;
 385
 386                         // verify message digest
 387                         if (messageDigest == null)
 388                                 return false;
 389                         // TODO: must be read from the ASN.1 structure
 390                         string hashName = null;
 391                         switch (messageDigest.Length) {
 392                                 case 16:
 393                                         hashName = "MD5";
 394                                         break;
 395                                 case 20:
 396                                         hashName = "SHA1";
 397                                         break;
 398                         }
 399                         HashAlgorithm ha = HashAlgorithm.Create (hashName);
 400                         if (!messageDigest.CompareValue (ha.ComputeHash (signature)))
 401                                 return false;
 402
 403                         // verify signature
 404                         byte[] counterSignature = cs.Signature;
 405                         string hashOID = CryptoConfig.MapNameToOID (hashName);
 406
 407                         // change to SET OF (not [0]) as per PKCS #7 1.5
 408                         ASN1 aa = new ASN1 (0x31);
 409                         foreach (ASN1 a in cs.AuthenticatedAttributes)
 410                                 aa.Add (a);
 411                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 412
 413                         // we need to try all certificates
 414                         string issuer = cs.IssuerName;
 415                         byte[] serial = cs.SerialNumber;
 416                         foreach (X509Certificate x509 in coll) {
 417                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 418                                         // don't verify if key size don't match
 419                                         if (x509.PublicKey.Length > (counterSignature.Length >> 3)) {
 420                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 421                                                 if (rsa.VerifyHash (p7hash, hashOID, counterSignature)) {
 422                                                         timestampChain.LoadCertificates (coll);
 423                                                         return (timestampChain.Build (x509));
 424                                                 }
 425                                         }
 426                                 }
 427                         }
 428                         // no certificate can verify this signature!
 429                         return false;
 430                 }
 431
 432                 private void Reset ()
 433                 {
 434                         filename = null;
 435                         entry = null;
 436                         hash = null;
 437                         signedHash = null;
 438                         signingCertificate = null;
 439                         reason = -1;
 440                         trustedRoot = false;
 441                         trustedTimestampRoot = false;
 442                         signerChain.Reset ();
 443                         timestampChain.Reset ();
 444                         timestamp = DateTime.MinValue;
 445                 }
 446         }
 447 }