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//
// AuthenticodeBase.cs: Authenticode signature base class
//
// Author:
// Sebastien Pouliot <sebastien@ximian.com>
//
// (C) 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System;
using System.IO;
using System.Security.Cryptography;
namespace Mono.Security.Authenticode {
// References:
// a. http://www.cs.auckland.ac.nz/~pgut001/pubs/authenticode.txt
#if INSIDE_CORLIB
internal
#else
public
#endif
enum Authority {
Individual,
Commercial,
Maximum
}
#if INSIDE_CORLIB
internal
#else
public
#endif
class AuthenticodeBase {
public const string spcIndirectDataContext = "1.3.6.1.4.1.311.2.1.4";
private byte[] fileblock;
private FileStream fs;
private int blockNo;
private int blockLength;
private int peOffset;
private int dirSecurityOffset;
private int dirSecuritySize;
public AuthenticodeBase ()
{
fileblock = new byte [4096];
}
internal void Open (string filename)
{
if (fs != null)
Close ();
fs = new FileStream (filename, FileMode.Open, FileAccess.Read, FileShare.Read);
}
internal void Close ()
{
if (fs != null) {
fs.Close ();
fs = null;
blockNo = 0;
}
}
internal bool ReadFirstBlock ()
{
if (fs == null)
return false;
fs.Position = 0;
// read first block - it will include (100% sure)
// the MZ header and (99.9% sure) the PE header
blockLength = fs.Read (fileblock, 0, fileblock.Length);
blockNo = 1;
if (blockLength < 64)
return false; // invalid PE file
// 1. Validate the MZ header informations
// 1.1. Check for magic MZ at start of header
if (BitConverterLE.ToUInt16 (fileblock, 0) != 0x5A4D)
return false;
// 1.2. Find the offset of the PE header
peOffset = BitConverterLE.ToInt32 (fileblock, 60);
if (peOffset > fileblock.Length) {
// just in case (0.1%) this can actually happen
string msg = String.Format (Locale.GetText (
"Header size too big (> {0} bytes)."),
fileblock.Length);
throw new NotSupportedException (msg);
}
if (peOffset > fs.Length)
return false;
// 2. Read between DOS header and first part of PE header
// 2.1. Check for magic PE at start of header
if (BitConverterLE.ToUInt16 (fileblock, peOffset) != 0x4550)
return false;
// 2.2. Locate IMAGE_DIRECTORY_ENTRY_SECURITY (offset and size)
dirSecurityOffset = BitConverterLE.ToInt32 (fileblock, peOffset + 152);
dirSecuritySize = BitConverterLE.ToInt32 (fileblock, peOffset + 156);
return true;
}
internal byte[] GetSecurityEntry ()
{
if (blockNo < 1)
ReadFirstBlock ();
if (dirSecuritySize > 8) {
// remove header from size (not ASN.1 based)
byte[] secEntry = new byte [dirSecuritySize - 8];
// position after header and read entry
fs.Position = dirSecurityOffset + 8;
fs.Read (secEntry, 0, secEntry.Length);
return secEntry;
}
return null;
}
// returns null if the file isn't signed
internal byte[] GetHash (HashAlgorithm hash)
{
if (blockNo < 1)
ReadFirstBlock ();
fs.Position = blockLength;
// hash the rest of the file
long n = fs.Length - blockLength;
// minus any authenticode signature (with 8 bytes header)
if (dirSecurityOffset > 0) {
// it is also possible that the signature block
// starts within the block in memory (small EXE)
if (dirSecurityOffset < blockLength) {
blockLength = dirSecurityOffset;
n = 0;
}
else
n -= (dirSecuritySize);
}
// Authenticode(r) gymnastics
// Hash from (generally) 0 to 215 (216 bytes)
int pe = peOffset + 88;
hash.TransformBlock (fileblock, 0, pe, fileblock, 0);
// then skip 4 for checksum
pe += 4;
// Continue hashing from (generally) 220 to 279 (60 bytes)
hash.TransformBlock (fileblock, pe, 60, fileblock, pe);
// then skip 8 bytes for IMAGE_DIRECTORY_ENTRY_SECURITY
pe += 68;
// everything is present so start the hashing
if (n == 0) {
// hash the (only) block
hash.TransformFinalBlock (fileblock, pe, blockLength - pe);
}
else {
// hash the last part of the first (already in memory) block
hash.TransformBlock (fileblock, pe, blockLength - pe, fileblock, 0);
// hash by blocks of 4096 bytes
long blocks = (n >> 12);
int remainder = (int)(n - (blocks << 12));
if (remainder == 0) {
blocks--;
remainder = 4096;
}
// blocks
while (blocks-- > 0) {
fs.Read (fileblock, 0, fileblock.Length);
hash.TransformBlock (fileblock, 0, fileblock.Length, fileblock, 0);
}
// remainder
if (fs.Read (fileblock, 0, remainder) != remainder)
return null;
hash.TransformFinalBlock (fileblock, 0, remainder);
}
return hash.Hash;
}
// for compatibility only
protected byte[] HashFile (string fileName, string hashName)
{
try {
Open (fileName);
HashAlgorithm hash = HashAlgorithm.Create (hashName);
byte[] result = GetHash (hash);
Close ();
return result;
}
catch {
return null;
}
}
}
}
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