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

   1 //
   2 // AuthenticodeSignature.cs: Authenticode signature validator and generator
   3 //
   4 // Author:
   5 //      Sebastien Pouliot (spouliot@motus.com)
   6 //
   7 // (C) 2003 Motus Technologies Inc. (http://www.motus.com)
   8 //
   9
  10 using System;
  11 using System.IO;
  12 using System.Security.Cryptography;
  13
  14 using Mono.Security;
  15 using Mono.Security.X509;
  16
  17 namespace Mono.Security.Authenticode {
  18
  19         // References:
  20         // a.   http://www.cs.auckland.ac.nz/~pgut001/pubs/authenticode.txt
  21
  22         public class AuthenticodeDeformatter : AuthenticodeBase {
  23
  24                 private string filename;
  25                 private byte[] hash;
  26                 private X509CertificateCollection coll;
  27                 private ASN1 signedHash;
  28                 private DateTime timestamp;
  29                 private X509Certificate signingCertificate;
  30                 private int reason;
  31
  32                 private X509Chain signerChain;
  33                 private X509Chain timestampChain;
  34
  35                 public AuthenticodeDeformatter () : base ()
  36                 {
  37                         reason = -1;
  38                         signerChain = new X509Chain ();
  39                         timestampChain = new X509Chain ();
  40                 }
  41
  42                 public AuthenticodeDeformatter (string fileName) : this ()
  43                 {
  44                         CheckSignature (fileName);
  45                 }
  46
  47                 public string FileName {
  48                         get { return filename; }
  49                         set { CheckSignature (value); }
  50                 }
  51
  52                 public byte[] Hash {
  53                         get {
  54                                 if (signedHash == null)
  55                                         return null;
  56                                 return signedHash.Value;
  57                         }
  58                 }
  59
  60                 public int Reason {
  61                         get {
  62                                 if (reason == -1)
  63                                         IsTrusted ();
  64                                 return reason;
  65                         }
  66                 }
  67
  68                 public bool IsTrusted ()
  69                 {
  70                         if (rawData == null) {
  71                                 reason = 1;
  72                                 return false;
  73                         }
  74
  75                         if (signingCertificate == null) {
  76                                 reason = 7;
  77                                 return false;
  78                         }
  79
  80                         if (signerChain.Root == null) {
  81                                 reason = 6;
  82                                 return false;
  83                         }
  84
  85                         if (timestamp != DateTime.MinValue) {
  86                                 if (timestampChain.Root == null) {
  87                                         reason = 6;
  88                                         return false;
  89                                 }
  90
  91                                 // check that file was timestamped when certificates were valid
  92                                 if (!signingCertificate.WasCurrent (Timestamp)) {
  93                                         reason = 4;
  94                                         return false;
  95                                 }
  96                         }
  97                         else if (!signingCertificate.IsCurrent) {
  98                                 // signature only valid if the certificate is valid
  99                                 reason = 8;
 100                                 return false;
 101                         }
 102
 103                         reason = 0;
 104                         return true;
 105                 }
 106
 107                 public byte[] Signature {
 108                         get { return rawData; }
 109                 }
 110
 111                 public DateTime Timestamp {
 112                         get { return timestamp; }
 113                 }
 114
 115                 public X509CertificateCollection Certificates {
 116                         get { return coll; }
 117                 }
 118
 119                 private bool CheckSignature (string fileName)
 120                 {
 121                         filename = fileName;
 122
 123                         // by default we try with MD5
 124                         string hashName = "MD5";
 125                         // compare the signature's hash with the hash of the file
 126                         hash = HashFile (filename, hashName);
 127
 128                         // is a signature present ?
 129                         if (rawData == null)
 130                                 return false;
 131
 132                         PKCS7.ContentInfo ci = new PKCS7.ContentInfo (rawData);
 133                         if (ci.ContentType != PKCS7.signedData)
 134                                 return false;
 135
 136                         PKCS7.SignedData sd = new PKCS7.SignedData (ci.Content);
 137                         if (sd.ContentInfo.ContentType != spcIndirectDataContext)
 138                                 return false;
 139
 140                         coll = sd.Certificates;
 141
 142                         ASN1 spc = sd.ContentInfo.Content;
 143                         signedHash = spc [0][1][1];
 144                         if (signedHash.Length == 20) {
 145                                 // seems to be SHA-1, restart hashing
 146                                 hashName = "SHA1";
 147                                 hash = HashFile (filename, hashName);
 148                         }
 149
 150                         if (!signedHash.CompareValue (hash))
 151                                 return false;
 152
 153                         // messageDigest is a hash of spcIndirectDataContext (which includes the file hash)
 154                         byte[] spcIDC = spc [0].Value;
 155                         HashAlgorithm ha = HashAlgorithm.Create (hashName);
 156                         byte[] messageDigest = ha.ComputeHash (spcIDC);
 157
 158                         return VerifySignature (sd, messageDigest, hashName);
 159                 }
 160
 161                 private bool CompareIssuerSerial (string issuer, byte[] serial, X509Certificate x509)
 162                 {
 163                         if (issuer != x509.IssuerName)
 164                                 return false;
 165                         if (serial.Length != x509.SerialNumber.Length)
 166                                 return false;
 167                         // MS shows the serial number inversed (so is Mono.Security.X509.X509Certificate)
 168                         int n = serial.Length;
 169                         for (int i=0; i < serial.Length; i++) {
 170                                 if (serial [i] != x509.SerialNumber [--n])
 171                                         return false;
 172                         }
 173                         // must be true
 174                         return true;
 175                 }
 176
 177                 //private bool VerifySignature (ASN1 cs, byte[] calculatedMessageDigest, string hashName)
 178                 private bool VerifySignature (PKCS7.SignedData sd, byte[] calculatedMessageDigest, string hashName)
 179                 {
 180                         string contentType = null;
 181                         ASN1 messageDigest = null;
 182                         string spcStatementType = null;
 183                         string spcSpOpusInfo = null;
 184
 185                         for (int i=0; i < sd.SignerInfo.AuthenticatedAttributes.Count; i++) {
 186                                 ASN1 attr = (ASN1) sd.SignerInfo.AuthenticatedAttributes [i];
 187                                 string oid = ASN1Convert.ToOID (attr[0]);
 188                                 switch (oid) {
 189                                         case "1.2.840.113549.1.9.3":
 190                                                 // contentType
 191                                                 contentType = ASN1Convert.ToOID (attr[1][0]);
 192                                                 break;
 193                                         case "1.2.840.113549.1.9.4":
 194                                                 // messageDigest
 195                                                 messageDigest = attr[1][0];
 196                                                 break;
 197                                         case "1.3.6.1.4.1.311.2.1.11":
 198                                                 // spcStatementType (Microsoft code signing)
 199                                                 // possible values
 200                                                 // - individualCodeSigning (1 3 6 1 4 1 311 2 1 21)
 201                                                 // - commercialCodeSigning (1 3 6 1 4 1 311 2 1 22)
 202                                                 spcStatementType = ASN1Convert.ToOID (attr[1][0][0]);
 203                                                 break;
 204                                         case "1.3.6.1.4.1.311.2.1.12":
 205                                                 // spcSpOpusInfo (Microsoft code signing)
 206                                                 try {
 207                                                         spcSpOpusInfo = System.Text.Encoding.UTF8.GetString (attr[1][0][1][0].Value);
 208                                                 }
 209                                                 catch {
 210                                                         spcSpOpusInfo = null;
 211                                                 }
 212                                                 break;
 213                                         default:
 214                                                 break;
 215                                 }
 216                         }
 217                         if (contentType != spcIndirectDataContext)
 218                                 return false;
 219
 220                         // verify message digest
 221                         if (messageDigest == null)
 222                                 return false;
 223                         if (!messageDigest.CompareValue (calculatedMessageDigest))
 224                                 return false;
 225
 226                         // verify signature
 227                         string hashOID = CryptoConfig.MapNameToOID (hashName);
 228
 229                         // change to SET OF (not [0]) as per PKCS #7 1.5
 230                         ASN1 aa = new ASN1 (0x31);
 231                         foreach (ASN1 a in sd.SignerInfo.AuthenticatedAttributes)
 232                                 aa.Add (a);
 233                         HashAlgorithm ha = HashAlgorithm.Create (hashName);
 234                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 235
 236                         byte[] signature = sd.SignerInfo.Signature;
 237                         // we need to find the specified certificate
 238                         string issuer = sd.SignerInfo.IssuerName;
 239                         byte[] serial = sd.SignerInfo.SerialNumber;
 240                         foreach (X509Certificate x509 in coll) {
 241                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 242                                         // don't verify is key size don't match
 243                                         if (x509.PublicKey.Length > (signature.Length >> 3)) {
 244                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 245                                                 if (rsa.VerifyHash (p7hash, hashOID, signature)) {
 246                                                         signerChain.LoadCertificates (coll);
 247                                                         if (signerChain.GetChain (x509) != null)
 248                                                                 signingCertificate = x509;
 249                                                         else
 250                                                                 return false;
 251                                                 }
 252                                         }
 253                                 }
 254                         }
 255
 256                         for (int i=0; i < sd.SignerInfo.UnauthenticatedAttributes.Count; i++) {
 257                                 ASN1 attr = (ASN1) sd.SignerInfo.UnauthenticatedAttributes [i];
 258                                 string oid = ASN1Convert.ToOID (attr [0]);
 259                                 switch (oid) {
 260                                         case PKCS7.countersignature:
 261                                                 // SEQUENCE {
 262                                                 //   OBJECT IDENTIFIER
 263                                                 //     countersignature (1 2 840 113549 1 9 6)
 264                                                 //   SET {
 265                                                 PKCS7.SignerInfo cs = new PKCS7.SignerInfo (attr [1]);
 266                                                 return VerifyCounterSignature (cs, signature, hashName);
 267                                         default:
 268                                                 // we don't support other unauthenticated attributes
 269                                                 break;
 270                                 }
 271                         }
 272
 273                         return true;
 274                 }
 275
 276                 //private bool VerifyCounterSignature (ASN1 cs, byte[] signature, string hashName)
 277                 private bool VerifyCounterSignature (PKCS7.SignerInfo cs, byte[] signature, string hashName)
 278                 {
 279                         // SEQUENCE {
 280                         //   INTEGER 1
 281                         if (cs.Version != 1)
 282                                 return false;
 283                         //   SEQUENCE {
 284                         //      SEQUENCE {
 285
 286                         string contentType = null;
 287                         ASN1 messageDigest = null;
 288                         for (int i=0; i < cs.AuthenticatedAttributes.Count; i++) {
 289                                 // SEQUENCE {
 290                                 //   OBJECT IDENTIFIER
 291                                 ASN1 attr = (ASN1) cs.AuthenticatedAttributes [i];
 292                                 string oid = ASN1Convert.ToOID (attr[0]);
 293                                 switch (oid) {
 294                                         case "1.2.840.113549.1.9.3":
 295                                                 // contentType
 296                                                 contentType = ASN1Convert.ToOID (attr[1][0]);
 297                                                 break;
 298                                         case "1.2.840.113549.1.9.4":
 299                                                 // messageDigest
 300                                                 messageDigest = attr[1][0];
 301                                                 break;
 302                                         case "1.2.840.113549.1.9.5":
 303                                                 // SEQUENCE {
 304                                                 //   OBJECT IDENTIFIER
 305                                                 //     signingTime (1 2 840 113549 1 9 5)
 306                                                 //   SET {
 307                                                 //     UTCTime '030124013651Z'
 308                                                 //   }
 309                                                 // }
 310                                                 timestamp = ASN1Convert.ToDateTime (attr[1][0]);
 311                                                 break;
 312                                         default:
 313                                                 break;
 314                                 }
 315                         }
 316
 317                         if (contentType != PKCS7.data)
 318                                 return false;
 319
 320                         // verify message digest
 321                         if (messageDigest == null)
 322                                 return false;
 323                         // TODO: must be read from the ASN.1 structure
 324                         switch (messageDigest.Length) {
 325                                 case 16:
 326                                         hashName = "MD5";
 327                                         break;
 328                                 case 20:
 329                                         hashName = "SHA1";
 330                                         break;
 331                         }
 332                         HashAlgorithm ha = HashAlgorithm.Create (hashName);
 333                         if (!messageDigest.CompareValue (ha.ComputeHash (signature)))
 334                                 return false;
 335
 336                         // verify signature
 337                         byte[] counterSignature = cs.Signature;
 338                         string hashOID = CryptoConfig.MapNameToOID (hashName);
 339
 340                         // change to SET OF (not [0]) as per PKCS #7 1.5
 341                         ASN1 aa = new ASN1 (0x31);
 342                         foreach (ASN1 a in cs.AuthenticatedAttributes)
 343                                 aa.Add (a);
 344                         byte[] p7hash = ha.ComputeHash (aa.GetBytes ());
 345
 346                         // we need to try all certificates
 347                         string issuer = cs.IssuerName;
 348                         byte[] serial = cs.SerialNumber;
 349                         foreach (X509Certificate x509 in coll) {
 350                                 if (CompareIssuerSerial (issuer, serial, x509)) {
 351                                         // don't verify is key size don't match
 352                                         if (x509.PublicKey.Length > (counterSignature.Length >> 3)) {
 353                                                 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) x509.RSA;
 354                                                 if (rsa.VerifyHash (p7hash, hashOID, counterSignature)) {
 355                                                         timestampChain.LoadCertificates (coll);
 356                                                         return (timestampChain.GetChain (x509) != null);
 357                                                 }
 358                                         }
 359                                 }
 360                         }
 361                         // no certificate can verify this signature!
 362                         return false;
 363                 }
 364         }
 365 }