/// <summary>
/// Creates a counter signature, just like
/// <c>sn -a IdentityPubKey.snk IdentityKey.snk SignaturePubKey.snk</c> can do.
/// The public key <c>sn</c> prints is <paramref name="signaturePubKey"/>'s value.
/// </summary>
/// <param name="identityPubKey">Identity public key</param>
/// <param name="identityKey">Identity strong name key pair</param>
/// <param name="signaturePubKey">Signature public key</param>
/// <returns>The counter signature</returns>
public static byte[] CreateCounterSignature(StrongNamePublicKey identityPubKey, StrongNameKey identityKey, StrongNamePublicKey signaturePubKey)
{
var hash = AssemblyHash.Hash(signaturePubKey.CreatePublicKey(), identityPubKey.HashAlgorithm);
using (var rsa = identityKey.CreateRSA()) {
var rsaFmt = new RSAPKCS1SignatureFormatter(rsa);
string hashName = identityPubKey.HashAlgorithm.GetName();
rsaFmt.SetHashAlgorithm(hashName);
var snSig = rsaFmt.CreateSignature(hash);
Array.Reverse(snSig);
return(snSig);
}
}
/// <summary>
/// Strong name hashes the .NET file
/// </summary>
/// <param name="hashAlg">Hash algorithm</param>
/// <param name="snSigOffset">Strong name sig offset (relative to start of .NET PE file)</param>
/// <param name="snSigSize">Size of strong name signature</param>
/// <returns>The strong name hash of the .NET file</returns>
byte[] StrongNameHashData(AssemblyHashAlgorithm hashAlg, long snSigOffset, uint snSigSize)
{
var reader = new BinaryReader(stream);
snSigOffset += baseOffset;
long snSigOffsetEnd = snSigOffset + snSigSize;
using (var hasher = new AssemblyHash(hashAlg)) {
var buffer = new byte[0x8000];
// Hash the DOS header. It's defined to be all data from the start of
// the file up to the NT headers.
stream.Position = baseOffset + 0x3C;
uint ntHeadersOffs = reader.ReadUInt32();
stream.Position = baseOffset;
hasher.Hash(stream, ntHeadersOffs, buffer);
// Hash NT headers, but hash authenticode + checksum as 0s
stream.Position += 6;
int numSections = reader.ReadUInt16();
stream.Position -= 8;
hasher.Hash(stream, 0x18, buffer); // magic + FileHeader
bool is32bit = reader.ReadUInt16() == 0x010B;
stream.Position -= 2;
int optHeaderSize = is32bit ? 0x60 : 0x70;
if (stream.Read(buffer, 0, optHeaderSize) != optHeaderSize)
{
throw new IOException("Could not read data");
}
// Clear checksum
for (int i = 0; i < 4; i++)
{
buffer[0x40 + i] = 0;
}
hasher.Hash(buffer, 0, optHeaderSize);
const int imageDirsSize = 16 * 8;
if (stream.Read(buffer, 0, imageDirsSize) != imageDirsSize)
{
throw new IOException("Could not read data");
}
// Clear authenticode data dir
for (int i = 0; i < 8; i++)
{
buffer[4 * 8 + i] = 0;
}
hasher.Hash(buffer, 0, imageDirsSize);
// Hash section headers
long sectHeadersOffs = stream.Position;
hasher.Hash(stream, (uint)numSections * 0x28, buffer);
// Hash all raw section data but make sure we don't hash the location
// where the strong name signature will be stored.
for (int i = 0; i < numSections; i++)
{
stream.Position = sectHeadersOffs + i * 0x28 + 0x10;
uint sizeOfRawData = reader.ReadUInt32();
uint pointerToRawData = reader.ReadUInt32();
stream.Position = baseOffset + pointerToRawData;
while (sizeOfRawData > 0)
{
var pos = stream.Position;
if (snSigOffset <= pos && pos < snSigOffsetEnd)
{
uint skipSize = (uint)(snSigOffsetEnd - pos);
if (skipSize >= sizeOfRawData)
{
break;
}
sizeOfRawData -= skipSize;
stream.Position += skipSize;
continue;
}
if (pos >= snSigOffsetEnd)
{
hasher.Hash(stream, sizeOfRawData, buffer);
break;
}
uint maxLen = (uint)Math.Min(snSigOffset - pos, sizeOfRawData);
hasher.Hash(stream, maxLen, buffer);
sizeOfRawData -= maxLen;
}
}
return(hasher.ComputeHash());
}
}
