//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#ifndef OPENVPN_PKI_PKCS1_H
#define OPENVPN_PKI_PKCS1_H

#include <cstring>

#include <openvpn/common/size.hpp>
#include <openvpn/buffer/buffer.hpp>

namespace openvpn {
  namespace PKCS1 {
    // from http://www.ietf.org/rfc/rfc3447.txt
    namespace DigestPrefix { // CONST GLOBAL
      namespace {
	const unsigned char MD2[] = { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08,
				      0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
				      0x02, 0x02, 0x05, 0x00, 0x04, 0x10 };
	const unsigned char MD5[] = { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08,
				      0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d,
				      0x02, 0x05, 0x05, 0x00, 0x04, 0x10 };
	const unsigned char SHA1[] = { 0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
				       0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05,
				       0x00, 0x04, 0x14 };
	const unsigned char SHA256[] = { 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
					 0x60, 0x86, 0x48, 0x01, 0x65, 0x03,
					 0x04, 0x02, 0x01, 0x05, 0x00, 0x04,
					 0x20 };
	const unsigned char SHA384[] = { 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
					 0x60, 0x86, 0x48, 0x01, 0x65, 0x03,
					 0x04, 0x02, 0x02, 0x05, 0x00, 0x04,
					 0x30 };
	const unsigned char SHA512[] = { 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
					 0x60, 0x86, 0x48, 0x01, 0x65, 0x03,
					 0x04, 0x02, 0x03, 0x05, 0x00, 0x04,
					 0x40 };
      }

      template <typename T>
      class Parse
      {
      public:
	Parse(const T none,
	      const T md2,
	      const T md5,
	      const T sha1,
	      const T sha256,
	      const T sha384,
	      const T sha512)
	  : none_(none),
	    md2_(md2),
	    md5_(md5),
	    sha1_(sha1),
	    sha256_(sha256),
	    sha384_(sha384),
	    sha512_(sha512)
	{
	}

	T alg_from_prefix(Buffer& buf) const
	{
	  if (match(buf, MD2, sizeof(MD2)))
	    return md2_;
	  else if (match(buf, MD5, sizeof(MD5)))
	    return md5_;
	  else if (match(buf, SHA1, sizeof(SHA1)))
	    return sha1_;
	  else if (match(buf, SHA256, sizeof(SHA256)))
	    return sha256_;
	  else if (match(buf, SHA384, sizeof(SHA384)))
	    return sha384_;
	  else if (match(buf, SHA512, sizeof(SHA512)))
	    return sha512_;
	  else
	    return none_;
	}

      private:
	bool match(Buffer& buf, const unsigned char *data, const size_t size) const
	{
	  if (buf.size() < size)
	    return false;
	  else if (std::memcmp(buf.c_data(), data, size) == 0)
	    {
	      buf.advance(size);
	      return true;
	    }
	  else
	    return false;
	}

	const T none_, md2_, md5_, sha1_, sha256_, sha384_, sha512_;
      };
    }
  }
}

#endif