#region License

// The MIT License
//
// Copyright (c) 2006-2008 DevDefined Limited.
// 
// 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.

#endregion

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace DevDefined.OAuth.KeyInterop
{
	public class AsnKeyParser
	{
		readonly AsnParser parser;

		public AsnKeyParser(String pathname)
		{
			using (var reader = new BinaryReader(
				new FileStream(pathname, FileMode.Open, FileAccess.Read)))
			{
				var info = new FileInfo(pathname);

				parser = new AsnParser(reader.ReadBytes((int) info.Length));
			}
		}

		public AsnKeyParser(byte[] contents)
		{
			parser = new AsnParser(contents);
		}

		public static byte[] TrimLeadingZero(byte[] values)
		{
			byte[] r = null;
			if ((0x00 == values[0]) && (values.Length > 1))
			{
				r = new byte[values.Length - 1];
				Array.Copy(values, 1, r, 0, values.Length - 1);
			}
			else
			{
				r = new byte[values.Length];
				Array.Copy(values, r, values.Length);
			}

			return r;
		}

		public static bool EqualOid(byte[] first, byte[] second)
		{
			if (first.Length != second.Length)
			{
				return false;
			}

			for (int i = 0; i < first.Length; i++)
			{
				if (first[i] != second[i])
				{
					return false;
				}
			}

			return true;
		}

		public RSAParameters ParseRSAPublicKey()
		{
			var parameters = new RSAParameters();

			// Current value
			byte[] value = null;

			// Sanity Check
			int length = 0;

			// Checkpoint
			int position = parser.CurrentPosition();

			// Ignore Sequence - PublicKeyInfo
			length = parser.NextSequence();
			if (length != parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Sequence Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - AlgorithmIdentifier
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect AlgorithmIdentifier Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();
			// Grab the OID
			value = parser.NextOID();
			byte[] oid = {0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01};
			if (!EqualOid(value, oid))
			{
				throw new BerDecodeException("Expected OID 1.2.840.113549.1.1.1", position);
			}

			// Optional Parameters
			if (parser.IsNextNull())
			{
				parser.NextNull();
				// Also OK: value = parser.Next();
			}
			else
			{
				// Gracefully skip the optional data
				value = parser.Next();
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore BitString - PublicKey
			length = parser.NextBitString();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect PublicKey Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                (parser.RemainingBytes()).ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - RSAPublicKey
			length = parser.NextSequence();
			if (length < parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect RSAPublicKey Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			parameters.Modulus = TrimLeadingZero(parser.NextInteger());
			parameters.Exponent = TrimLeadingZero(parser.NextInteger());

			Debug.Assert(0 == parser.RemainingBytes());

			return parameters;
		}

		public RSAParameters ParseRSAPrivateKey()
		{
			var parameters = new RSAParameters();

			// Current value
			byte[] value = null;

			// Checkpoint
			int position = parser.CurrentPosition();

			// Sanity Check
			int length = 0;

			// Ignore Sequence - PrivateKeyInfo
			length = parser.NextSequence();
			if (length != parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Sequence Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();
			// Version
			value = parser.NextInteger();
			if (0x00 != value[0])
			{
				var sb = new StringBuilder("Incorrect PrivateKeyInfo Version. ");
				var v = new BigInteger(value);
				sb.AppendFormat("Expected: 0, Specified: {0}", v.ToString(10));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - AlgorithmIdentifier
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect AlgorithmIdentifier Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Grab the OID
			value = parser.NextOID();
			byte[] oid = {0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01};
			if (!EqualOid(value, oid))
			{
				throw new BerDecodeException("Expected OID 1.2.840.113549.1.1.1", position);
			}

			// Optional Parameters
			if (parser.IsNextNull())
			{
				parser.NextNull();
				// Also OK: value = parser.Next();
			}
			else
			{
				// Gracefully skip the optional data
				value = parser.Next();
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore OctetString - PrivateKey
			length = parser.NextOctetString();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect PrivateKey Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - RSAPrivateKey
			length = parser.NextSequence();
			if (length < parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect RSAPrivateKey Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();
			// Version
			value = parser.NextInteger();
			if (0x00 != value[0])
			{
				var sb = new StringBuilder("Incorrect RSAPrivateKey Version. ");
				var v = new BigInteger(value);
				sb.AppendFormat("Expected: 0, Specified: {0}", v.ToString(10));
				throw new BerDecodeException(sb.ToString(), position);
			}

			parameters.Modulus = TrimLeadingZero(parser.NextInteger());
			parameters.Exponent = TrimLeadingZero(parser.NextInteger());
			parameters.D = TrimLeadingZero(parser.NextInteger());
			parameters.P = TrimLeadingZero(parser.NextInteger());
			parameters.Q = TrimLeadingZero(parser.NextInteger());
			parameters.DP = TrimLeadingZero(parser.NextInteger());
			parameters.DQ = TrimLeadingZero(parser.NextInteger());
			parameters.InverseQ = TrimLeadingZero(parser.NextInteger());

			Debug.Assert(0 == parser.RemainingBytes());

			return parameters;
		}

		public DSAParameters ParseDSAPublicKey()
		{
			var parameters = new DSAParameters();

			// Current value
			byte[] value = null;

			// Current Position
			int position = parser.CurrentPosition();
			// Sanity Checks
			int length = 0;

			// Ignore Sequence - PublicKeyInfo
			length = parser.NextSequence();
			if (length != parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Sequence Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - AlgorithmIdentifier
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect AlgorithmIdentifier Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Grab the OID
			value = parser.NextOID();
			byte[] oid = {0x2a, 0x86, 0x48, 0xce, 0x38, 0x04, 0x01};
			if (!EqualOid(value, oid))
			{
				throw new BerDecodeException("Expected OID 1.2.840.10040.4.1", position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - DSS-Params
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect DSS-Params Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Next three are curve parameters
			parameters.P = TrimLeadingZero(parser.NextInteger());
			parameters.Q = TrimLeadingZero(parser.NextInteger());
			parameters.G = TrimLeadingZero(parser.NextInteger());

			// Ignore BitString - PrivateKey
			parser.NextBitString();

			// Public Key
			parameters.Y = TrimLeadingZero(parser.NextInteger());

			Debug.Assert(0 == parser.RemainingBytes());

			return parameters;
		}

		public DSAParameters ParseDSAPrivateKey()
		{
			var parameters = new DSAParameters();

			// Current value
			byte[] value = null;

			// Current Position
			int position = parser.CurrentPosition();
			// Sanity Checks
			int length = 0;

			// Ignore Sequence - PrivateKeyInfo
			length = parser.NextSequence();
			if (length != parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Sequence Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();
			// Version
			value = parser.NextInteger();
			if (0x00 != value[0])
			{
				throw new BerDecodeException("Incorrect PrivateKeyInfo Version", position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - AlgorithmIdentifier
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect AlgorithmIdentifier Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Checkpoint
			position = parser.CurrentPosition();
			// Grab the OID
			value = parser.NextOID();
			byte[] oid = {0x2a, 0x86, 0x48, 0xce, 0x38, 0x04, 0x01};
			if (!EqualOid(value, oid))
			{
				throw new BerDecodeException("Expected OID 1.2.840.10040.4.1", position);
			}

			// Checkpoint
			position = parser.CurrentPosition();

			// Ignore Sequence - DSS-Params
			length = parser.NextSequence();
			if (length > parser.RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect DSS-Params Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                length.ToString(CultureInfo.InvariantCulture),
				                parser.RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			// Next three are curve parameters
			parameters.P = TrimLeadingZero(parser.NextInteger());
			parameters.Q = TrimLeadingZero(parser.NextInteger());
			parameters.G = TrimLeadingZero(parser.NextInteger());

			// Ignore OctetString - PrivateKey
			parser.NextOctetString();

			// Private Key
			parameters.X = TrimLeadingZero(parser.NextInteger());

			Debug.Assert(0 == parser.RemainingBytes());

			return parameters;
		}
	}

	internal class AsnParser
	{
		readonly int initialCount;
		readonly List<byte> octets;

		public AsnParser(byte[] values)
		{
			octets = new List<byte>(values.Length);
			octets.AddRange(values);

			initialCount = octets.Count;
		}

		public int CurrentPosition()
		{
			return initialCount - octets.Count;
		}

		public int RemainingBytes()
		{
			return octets.Count;
		}

		int GetLength()
		{
			int length = 0;

			// Checkpoint
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();

				if (b == (b & 0x7f))
				{
					return b;
				}
				int i = b & 0x7f;

				if (i > 4)
				{
					var sb = new StringBuilder("Invalid Length Encoding. ");
					sb.AppendFormat("Length uses {0} octets",
					                i.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				while (0 != i--)
				{
					// shift left
					length <<= 8;

					length |= GetNextOctet();
				}
			}
			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}

			return length;
		}

		public byte[] Next()
		{
			int position = CurrentPosition();

			try
			{
#pragma warning disable 0219
				byte b = GetNextOctet();
#pragma warning restore 0219

				int length = GetLength();
				if (length > RemainingBytes())
				{
					var sb = new StringBuilder("Incorrect Size. ");
					sb.AppendFormat("Specified: {0}, Remaining: {1}",
					                length.ToString(CultureInfo.InvariantCulture),
					                RemainingBytes().ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				return GetOctets(length);
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public byte GetNextOctet()
		{
			int position = CurrentPosition();

			if (0 == RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                1.ToString(CultureInfo.InvariantCulture),
				                RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			byte b = GetOctets(1)[0];

			return b;
		}

		public byte[] GetOctets(int octetCount)
		{
			int position = CurrentPosition();

			if (octetCount > RemainingBytes())
			{
				var sb = new StringBuilder("Incorrect Size. ");
				sb.AppendFormat("Specified: {0}, Remaining: {1}",
				                octetCount.ToString(CultureInfo.InvariantCulture),
				                RemainingBytes().ToString(CultureInfo.InvariantCulture));
				throw new BerDecodeException(sb.ToString(), position);
			}

			var values = new byte[octetCount];

			try
			{
				octets.CopyTo(0, values, 0, octetCount);
				octets.RemoveRange(0, octetCount);
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}

			return values;
		}

		public bool IsNextNull()
		{
			return 0x05 == octets[0];
		}

		public int NextNull()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x05 != b)
				{
					var sb = new StringBuilder("Expected Null. ");
					sb.AppendFormat("Specified Identifier: {0}", b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				// Next octet must be 0
				b = GetNextOctet();
				if (0x00 != b)
				{
					var sb = new StringBuilder("Null has non-zero size. ");
					sb.AppendFormat("Size: {0}", b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				return 0;
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public bool IsNextSequence()
		{
			return 0x30 == octets[0];
		}

		public int NextSequence()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x30 != b)
				{
					var sb = new StringBuilder("Expected Sequence. ");
					sb.AppendFormat("Specified Identifier: {0}",
					                b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				int length = GetLength();
				if (length > RemainingBytes())
				{
					var sb = new StringBuilder("Incorrect Sequence Size. ");
					sb.AppendFormat("Specified: {0}, Remaining: {1}",
					                length.ToString(CultureInfo.InvariantCulture),
					                RemainingBytes().ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				return length;
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public bool IsNextOctetString()
		{
			return 0x04 == octets[0];
		}

		public int NextOctetString()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x04 != b)
				{
					var sb = new StringBuilder("Expected Octet String. ");
					sb.AppendFormat("Specified Identifier: {0}", b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				int length = GetLength();
				if (length > RemainingBytes())
				{
					var sb = new StringBuilder("Incorrect Octet String Size. ");
					sb.AppendFormat("Specified: {0}, Remaining: {1}",
					                length.ToString(CultureInfo.InvariantCulture),
					                RemainingBytes().ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				return length;
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public bool IsNextBitString()
		{
			return 0x03 == octets[0];
		}

		public int NextBitString()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x03 != b)
				{
					var sb = new StringBuilder("Expected Bit String. ");
					sb.AppendFormat("Specified Identifier: {0}", b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				int length = GetLength();

				// We need to consume unused bits, which is the first
				//   octet of the remaing values
				b = octets[0];
				octets.RemoveAt(0);
				length--;

				if (0x00 != b)
				{
					throw new BerDecodeException("The first octet of BitString must be 0", position);
				}

				return length;
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public bool IsNextInteger()
		{
			return 0x02 == octets[0];
		}

		public byte[] NextInteger()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x02 != b)
				{
					var sb = new StringBuilder("Expected Integer. ");
					sb.AppendFormat("Specified Identifier: {0}", b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				int length = GetLength();
				if (length > RemainingBytes())
				{
					var sb = new StringBuilder("Incorrect Integer Size. ");
					sb.AppendFormat("Specified: {0}, Remaining: {1}",
					                length.ToString(CultureInfo.InvariantCulture),
					                RemainingBytes().ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				return GetOctets(length);
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}

		public byte[] NextOID()
		{
			int position = CurrentPosition();

			try
			{
				byte b = GetNextOctet();
				if (0x06 != b)
				{
					var sb = new StringBuilder("Expected Object Identifier. ");
					sb.AppendFormat("Specified Identifier: {0}",
					                b.ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				int length = GetLength();
				if (length > RemainingBytes())
				{
					var sb = new StringBuilder("Incorrect Object Identifier Size. ");
					sb.AppendFormat("Specified: {0}, Remaining: {1}",
					                length.ToString(CultureInfo.InvariantCulture),
					                RemainingBytes().ToString(CultureInfo.InvariantCulture));
					throw new BerDecodeException(sb.ToString(), position);
				}

				var values = new byte[length];

				for (int i = 0; i < length; i++)
				{
					values[i] = octets[0];
					octets.RemoveAt(0);
				}

				return values;
			}

			catch (ArgumentOutOfRangeException ex)
			{
				throw new BerDecodeException("Error Parsing Key", position, ex);
			}
		}
	}
}