Don't rely on StrongNameKeyPair (#548)

Author: atykhyy

Mono.Cecil/AssemblyWriter.cs

@@ -102,8 +102,8 @@ static void Write (ModuleDefinition module, Disposable<Stream> stream, WriterPar
 			if (symbol_writer_provider == null && parameters.WriteSymbols)
 				symbol_writer_provider = new DefaultSymbolWriterProvider ();
 
-			if (parameters.StrongNameKeyPair != null && name != null) {
-				name.PublicKey = parameters.StrongNameKeyPair.PublicKey;
+			if (parameters.HasStrongNameKey && name != null) {
+				name.PublicKey = CryptoService.GetPublicKey (parameters);
 				module.Attributes |= ModuleAttributes.StrongNameSigned;
 			}
 
@@ -125,8 +125,8 @@ static void Write (ModuleDefinition module, Disposable<Stream> stream, WriterPar
 					stream.value.SetLength (0);
 					writer.WriteImage ();
 
-					if (parameters.StrongNameKeyPair != null)
-						CryptoService.StrongName (stream.value, writer, parameters.StrongNameKeyPair);
+					if (parameters.HasStrongNameKey)
+						CryptoService.StrongName (stream.value, writer, parameters);
 				}
 			} finally {
 				module.metadata_builder = null;

Mono.Cecil/ModuleDefinition.cs

@@ -183,6 +183,8 @@ public sealed class WriterParameters {
 		Stream symbol_stream;
 		ISymbolWriterProvider symbol_writer_provider;
 		bool write_symbols;
+		byte [] key_blob;
+		string key_container;
 		SR.StrongNameKeyPair key_pair;
 
 		public uint? Timestamp {
@@ -205,6 +207,20 @@ public bool WriteSymbols {
 			set { write_symbols = value; }
 		}
 
+		public bool HasStrongNameKey {
+			get { return key_pair != null || key_blob != null || key_container != null; }
+		}
+
+		public byte [] StrongNameKeyBlob {
+			get { return key_blob; }
+			set { key_blob = value; }
+		}
+
+		public string StrongNameKeyContainer {
+			get { return key_container; }
+			set { key_container = value; }
+		}
+
 		public SR.StrongNameKeyPair StrongNameKeyPair {
 			get { return key_pair; }
 			set { key_pair = value; }

Mono.Security.Cryptography/CryptoConvert.cs

@@ -44,6 +44,16 @@ static private uint ToUInt32LE (byte [] bytes, int offset)
 			return (uint)((bytes [offset+3] << 24) | (bytes [offset+2] << 16) | (bytes [offset+1] << 8) | bytes [offset]);
 		}
 
+		static private byte [] GetBytesLE (int val)
+		{
+			return new byte [] { 
+				(byte) (val & 0xff), 
+				(byte) ((val >> 8) & 0xff), 
+				(byte) ((val >> 16) & 0xff), 
+				(byte) ((val >> 24) & 0xff)
+			};
+                }
+
 		static private byte[] Trim (byte[] array)
 		{
 			for (int i=0; i < array.Length; i++) {
@@ -240,5 +250,41 @@ static public RSA FromCapiKeyBlob (byte[] blob, int offset)
 			}
 			throw new CryptographicException ("Unknown blob format.");
 		}
+
+		static public byte[] ToCapiPublicKeyBlob (RSA rsa) 
+		{
+			RSAParameters p = rsa.ExportParameters (false);
+			int keyLength = p.Modulus.Length; // in bytes
+			byte[] blob = new byte [20 + keyLength];
+
+			blob [0] = 0x06;	// Type - PUBLICKEYBLOB (0x06)
+			blob [1] = 0x02;	// Version - Always CUR_BLOB_VERSION (0x02)
+			// [2], [3]		// RESERVED - Always 0
+			blob [5] = 0x24;	// ALGID - Always 00 24 00 00 (for CALG_RSA_SIGN)
+			blob [8] = 0x52;	// Magic - RSA1 (ASCII in hex)
+			blob [9] = 0x53;
+			blob [10] = 0x41;
+			blob [11] = 0x31;
+
+			byte[] bitlen = GetBytesLE (keyLength << 3);
+			blob [12] = bitlen [0];	// bitlen
+			blob [13] = bitlen [1];	
+			blob [14] = bitlen [2];	
+			blob [15] = bitlen [3];
+
+			// public exponent (DWORD)
+			int pos = 16;
+			int n = p.Exponent.Length;
+			while (n > 0)
+				blob [pos++] = p.Exponent [--n];
+			// modulus
+			pos = 20;
+			byte[] part = p.Modulus;
+			int len = part.Length;
+			Array.Reverse (part, 0, len);
+			Buffer.BlockCopy (part, 0, blob, pos, len);
+			pos += len;
+			return blob;
+		}
 	}
 }

Mono.Security.Cryptography/CryptoService.cs

@@ -26,11 +26,33 @@ namespace Mono.Cecil {
 
 	static class CryptoService {
 
-		public static void StrongName (Stream stream, ImageWriter writer, StrongNameKeyPair key_pair)
+		public static byte [] GetPublicKey (WriterParameters parameters)
+		{
+			using (var rsa = parameters.CreateRSA ()) {
+				var cspBlob = CryptoConvert.ToCapiPublicKeyBlob (rsa);
+				var publicKey = new byte [12 + cspBlob.Length];
+				Buffer.BlockCopy (cspBlob, 0, publicKey, 12, cspBlob.Length);
+				// The first 12 bytes are documented at:
+				// http://msdn.microsoft.com/library/en-us/cprefadd/html/grfungethashfromfile.asp
+				// ALG_ID - Signature
+				publicKey [1] = 36;
+				// ALG_ID - Hash
+				publicKey [4] = 4;
+				publicKey [5] = 128;
+				// Length of Public Key (in bytes)
+				publicKey [8] = (byte) (cspBlob.Length >> 0);
+				publicKey [9] = (byte) (cspBlob.Length >> 8);
+				publicKey [10] = (byte) (cspBlob.Length >> 16);
+				publicKey [11] = (byte) (cspBlob.Length >> 24);
+				return publicKey;
+			}
+		}
+
+		public static void StrongName (Stream stream, ImageWriter writer, WriterParameters parameters)
 		{
 			int strong_name_pointer;
 
-			var strong_name = CreateStrongName (key_pair, HashStream (stream, writer, out strong_name_pointer));
+			var strong_name = CreateStrongName (parameters, HashStream (stream, writer, out strong_name_pointer));
 			PatchStrongName (stream, strong_name_pointer, strong_name);
 		}
 
@@ -40,11 +62,11 @@ static void PatchStrongName (Stream stream, int strong_name_pointer, byte [] str
 			stream.Write (strong_name, 0, strong_name.Length);
 		}
 
-		static byte [] CreateStrongName (StrongNameKeyPair key_pair, byte [] hash)
+		static byte [] CreateStrongName (WriterParameters parameters, byte [] hash)
 		{
 			const string hash_algo = "SHA1";
 
-			using (var rsa = key_pair.CreateRSA ()) {
+			using (var rsa = parameters.CreateRSA ()) {
 				var formatter = new RSAPKCS1SignatureFormatter (rsa);
 				formatter.SetHashAlgorithm (hash_algo);
 
@@ -74,7 +96,6 @@ static byte [] HashStream (Stream stream, ImageWriter writer, out int strong_nam
 			var sha1 = new SHA1Managed ();
 			var buffer = new byte [buffer_size];
 			using (var crypto_stream = new CryptoStream (Stream.Null, sha1, CryptoStreamMode.Write)) {
-
 				stream.Seek (0, SeekOrigin.Begin);
 				CopyStreamChunk (stream, crypto_stream, buffer, header_size);
 
@@ -148,12 +169,17 @@ public static Guid ComputeGuid (byte [] hash)
 
 	static partial class Mixin {
 
-		public static RSA CreateRSA (this StrongNameKeyPair key_pair)
+		public static RSA CreateRSA (this WriterParameters writer_parameters)
 		{
 			byte [] key;
 			string key_container;
 
-			if (!TryGetKeyContainer (key_pair, out key, out key_container))
+			if (writer_parameters.StrongNameKeyBlob != null)
+				return CryptoConvert.FromCapiKeyBlob (writer_parameters.StrongNameKeyBlob);
+
+			if (writer_parameters.StrongNameKeyContainer != null)
+				key_container = writer_parameters.StrongNameKeyContainer;
+			else if (!TryGetKeyContainer (writer_parameters.StrongNameKeyPair, out key, out key_container))
 				return CryptoConvert.FromCapiKeyBlob (key);
 
 			var parameters = new CspParameters {