class/Mono.Security/Mono.Security.Authenticode/AuthenticodeBase.cs

   1 //
   2 // AuthenticodeBase.cs: Authenticode signature base class
   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.Security.Cryptography;
  33
  34 namespace Mono.Security.Authenticode {
  35
  36         // References:
  37         // a.   http://www.cs.auckland.ac.nz/~pgut001/pubs/authenticode.txt
  38
  39 #if INSIDE_CORLIB
  40         internal
  41 #else
  42         public
  43 #endif
  44         enum Authority {
  45                 Individual,
  46                 Commercial,
  47                 Maximum
  48         }
  49
  50 #if INSIDE_CORLIB
  51         internal
  52 #else
  53         public
  54 #endif
  55         class AuthenticodeBase {
  56
  57                 public const string spcIndirectDataContext = "1.3.6.1.4.1.311.2.1.4";
  58
  59                 private byte[] fileblock;
  60                 private FileStream fs;
  61                 private int blockNo;
  62                 private int blockLength;
  63                 private int peOffset;
  64                 private int dirSecurityOffset;
  65                 private int dirSecuritySize;
  66                 private int coffSymbolTableOffset;
  67
  68                 public AuthenticodeBase ()
  69                 {
  70                         fileblock = new byte [4096];
  71                 }
  72
  73                 internal int PEOffset {
  74                         get {
  75                                 if (blockNo < 1)
  76                                         ReadFirstBlock ();
  77                                 return peOffset;
  78                         }
  79                 }
  80
  81                 internal int CoffSymbolTableOffset {
  82                         get {
  83                                 if (blockNo < 1)
  84                                         ReadFirstBlock ();
  85                                 return coffSymbolTableOffset;
  86                         }
  87                 }
  88
  89                 internal int SecurityOffset {
  90                         get {
  91                                 if (blockNo < 1)
  92                                         ReadFirstBlock ();
  93                                 return dirSecurityOffset;
  94                         }
  95                 }
  96
  97                 internal void Open (string filename)
  98                 {
  99                         if (fs != null)
 100                                 Close ();
 101                         fs = new FileStream (filename, FileMode.Open, FileAccess.Read, FileShare.Read);
 102                 }
 103
 104                 internal void Close ()
 105                 {
 106                         if (fs != null) {
 107                                 fs.Close ();
 108                                 fs = null;
 109                                 blockNo = 0;
 110                         }
 111                 }
 112
 113                 internal bool ReadFirstBlock ()
 114                 {
 115                         if (fs == null)
 116                                 return false;
 117
 118                         fs.Position = 0;
 119                         // read first block - it will include (100% sure)
 120                         // the MZ header and (99.9% sure) the PE header
 121                         blockLength = fs.Read (fileblock, 0, fileblock.Length);
 122                         blockNo = 1;
 123                         if (blockLength < 64)
 124                                 return false;   // invalid PE file
 125
 126                         // 1. Validate the MZ header informations
 127                         // 1.1. Check for magic MZ at start of header
 128                         if (BitConverterLE.ToUInt16 (fileblock, 0) != 0x5A4D)
 129                                 return false;
 130
 131                         // 1.2. Find the offset of the PE header
 132                         peOffset = BitConverterLE.ToInt32 (fileblock, 60);
 133                         if (peOffset > fileblock.Length) {
 134                                 // just in case (0.1%) this can actually happen
 135                                 string msg = String.Format (Locale.GetText (
 136                                         "Header size too big (> {0} bytes)."),
 137                                         fileblock.Length);
 138                                 throw new NotSupportedException (msg);
 139                         }
 140                         if (peOffset > fs.Length)
 141                                 return false;
 142
 143                         // 2. Read between DOS header and first part of PE header
 144                         // 2.1. Check for magic PE at start of header
 145                         //      PE - NT header ('P' 'E' 0x00 0x00)
 146                         if (BitConverterLE.ToUInt32 (fileblock, peOffset) != 0x4550)
 147                                 return false;
 148
 149                         // 2.2. Locate IMAGE_DIRECTORY_ENTRY_SECURITY (offset and size)
 150                         dirSecurityOffset = BitConverterLE.ToInt32 (fileblock, peOffset + 152);
 151                         dirSecuritySize = BitConverterLE.ToInt32 (fileblock, peOffset + 156);
 152
 153                         // COFF symbol tables are deprecated - we'll strip them if we see them!
 154                         // (otherwise the signature won't work on MS and we don't want to support COFF for that)
 155                         coffSymbolTableOffset = BitConverterLE.ToInt32 (fileblock, peOffset + 12);
 156
 157                         return true;
 158                 }
 159
 160                 internal byte[] GetSecurityEntry ()
 161                 {
 162                         if (blockNo < 1)
 163                                 ReadFirstBlock ();
 164
 165                         if (dirSecuritySize > 8) {
 166                                 // remove header from size (not ASN.1 based)
 167                                 byte[] secEntry = new byte [dirSecuritySize - 8];
 168                                 // position after header and read entry
 169                                 fs.Position = dirSecurityOffset + 8;
 170                                 fs.Read (secEntry, 0, secEntry.Length);
 171                                 return secEntry;
 172                         }
 173                         return null;
 174                 }
 175
 176                 internal byte[] GetHash (HashAlgorithm hash)
 177                 {
 178                         if (blockNo < 1)
 179                                 ReadFirstBlock ();
 180                         fs.Position = blockLength;
 181
 182                         // hash the rest of the file
 183                         long n;
 184                         int addsize = 0;
 185                         // minus any authenticode signature (with 8 bytes header)
 186                         if (dirSecurityOffset > 0) {
 187                                 // it is also possible that the signature block
 188                                 // starts within the block in memory (small EXE)
 189                                 if (dirSecurityOffset < blockLength) {
 190                                         blockLength = dirSecurityOffset;
 191                                         n = 0;
 192                                 } else {
 193                                         n = dirSecurityOffset - blockLength;
 194                                 }
 195                         } else if (coffSymbolTableOffset > 0) {
 196                                 fileblock[PEOffset + 12] = 0;
 197                                 fileblock[PEOffset + 13] = 0;
 198                                 fileblock[PEOffset + 14] = 0;
 199                                 fileblock[PEOffset + 15] = 0;
 200                                 fileblock[PEOffset + 16] = 0;
 201                                 fileblock[PEOffset + 17] = 0;
 202                                 fileblock[PEOffset + 18] = 0;
 203                                 fileblock[PEOffset + 19] = 0;
 204                                 // it is also possible that the signature block
 205                                 // starts within the block in memory (small EXE)
 206                                 if (coffSymbolTableOffset < blockLength) {
 207                                         blockLength = coffSymbolTableOffset;
 208                                         n = 0;
 209                                 } else {
 210                                         n = coffSymbolTableOffset - blockLength;
 211                                 }
 212                         } else {
 213                                 addsize = (int) (fs.Length & 7);
 214                                 if (addsize > 0)
 215                                         addsize = 8 - addsize;
 216
 217                                 n = fs.Length - blockLength;
 218                         }
 219
 220                         // Authenticode(r) gymnastics
 221                         // Hash from (generally) 0 to 215 (216 bytes)
 222                         int pe = peOffset + 88;
 223                         hash.TransformBlock (fileblock, 0, pe, fileblock, 0);
 224                         // then skip 4 for checksum
 225                         pe += 4;
 226                         // Continue hashing from (generally) 220 to 279 (60 bytes)
 227                         hash.TransformBlock (fileblock, pe, 60, fileblock, pe);
 228                         // then skip 8 bytes for IMAGE_DIRECTORY_ENTRY_SECURITY
 229                         pe += 68;
 230
 231                         // everything is present so start the hashing
 232                         if (n == 0) {
 233                                 // hash the (only) block
 234                                 hash.TransformFinalBlock (fileblock, pe, blockLength - pe);
 235                         }
 236                         else {
 237                                 // hash the last part of the first (already in memory) block
 238                                 hash.TransformBlock (fileblock, pe, blockLength - pe, fileblock, pe);
 239
 240                                 // hash by blocks of 4096 bytes
 241                                 long blocks = (n >> 12);
 242                                 int remainder = (int)(n - (blocks << 12));
 243                                 if (remainder == 0) {
 244                                         blocks--;
 245                                         remainder = 4096;
 246                                 }
 247                                 // blocks
 248                                 while (blocks-- > 0) {
 249                                         fs.Read (fileblock, 0, fileblock.Length);
 250                                         hash.TransformBlock (fileblock, 0, fileblock.Length, fileblock, 0);
 251                                 }
 252                                 // remainder
 253                                 if (fs.Read (fileblock, 0, remainder) != remainder)
 254                                         return null;
 255
 256                                 if (addsize > 0) {
 257                                         hash.TransformBlock (fileblock, 0, remainder, fileblock, 0);
 258                                         hash.TransformFinalBlock (new byte [addsize], 0, addsize);
 259                                 } else {
 260                                         hash.TransformFinalBlock (fileblock, 0, remainder);
 261                                 }
 262                         }
 263                         return hash.Hash;
 264                 }
 265
 266                 // for compatibility only
 267                 protected byte[] HashFile (string fileName, string hashName)
 268                 {
 269                         try {
 270                                 Open (fileName);
 271                                 HashAlgorithm hash = HashAlgorithm.Create (hashName);
 272                                 byte[] result = GetHash (hash);
 273                                 Close ();
 274                                 return result;
 275                         }
 276                         catch {
 277                                 return null;
 278                         }
 279                 }
 280         }
 281 }