mirror of
https://github.com/OpenVPN/openvpn3.git
synced 2024-09-20 12:12:15 +02:00
130 lines
3.8 KiB
C++
130 lines
3.8 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2013-2014 OpenVPN Technologies, Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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// General-purpose OpenVPN protocol encrypt method that is independent of the underlying CRYPTO_API
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#ifndef OPENVPN_CRYPTO_ENCRYPT_H
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#define OPENVPN_CRYPTO_ENCRYPT_H
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#include <cstring>
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#include <openvpn/common/types.hpp>
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#include <openvpn/common/exception.hpp>
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#include <openvpn/buffer/buffer.hpp>
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#include <openvpn/random/prng.hpp>
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#include <openvpn/frame/frame.hpp>
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#include <openvpn/crypto/cipher.hpp>
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#include <openvpn/crypto/hmac.hpp>
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#include <openvpn/crypto/static_key.hpp>
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#include <openvpn/crypto/packet_id.hpp>
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namespace openvpn {
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template <typename RAND_API, typename CRYPTO_API>
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class Encrypt {
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public:
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OPENVPN_SIMPLE_EXCEPTION(unsupported_cipher_mode);
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void encrypt(BufferAllocated& buf, const PacketID::time_t now)
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{
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// skip null packets
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if (!buf.size())
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return;
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if (cipher.defined())
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{
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// workspace for generating IV
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unsigned char iv_buf[CRYPTO_API::CipherContext::MAX_IV_LENGTH];
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const size_t iv_length = cipher.iv_length();
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// IV and packet ID are generated differently depending on cipher mode
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const int cipher_mode = cipher.cipher_mode();
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if (cipher_mode == CRYPTO_API::CipherContext::CIPH_CBC_MODE)
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{
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// in CBC mode, use an explicit, random IV
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prng->rand_bytes(iv_buf, iv_length);
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// generate fresh outgoing packet ID and prepend to cleartext buffer
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pid_send.write_next(buf, true, now);
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}
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else
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{
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throw unsupported_cipher_mode();
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}
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// initialize work buffer
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frame->prepare(Frame::ENCRYPT_WORK, work);
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// encrypt from buf -> work
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const size_t encrypt_bytes = cipher.encrypt(iv_buf, work.data(), work.max_size(), buf.c_data(), buf.size());
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if (!encrypt_bytes)
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{
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buf.reset_size();
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return;
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}
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work.set_size(encrypt_bytes);
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// prepend the IV to the ciphertext
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work.prepend(iv_buf, iv_length);
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// HMAC the ciphertext
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prepend_hmac(work);
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// return ciphertext result in buf
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buf.swap(work);
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}
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else // no encryption
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{
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// generate fresh outgoing packet ID and prepend to cleartext buffer
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pid_send.write_next(buf, true, now);
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// HMAC the cleartext
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prepend_hmac(buf);
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}
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}
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Frame::Ptr frame;
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CipherContext<CRYPTO_API> cipher;
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HMACContext<CRYPTO_API> hmac;
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PacketIDSend pid_send;
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typename PRNG<RAND_API, CRYPTO_API>::Ptr prng;
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private:
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// compute HMAC signature of data buffer,
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// then prepend the signature to the buffer.
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void prepend_hmac(BufferAllocated& buf)
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{
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if (hmac.defined())
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{
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const unsigned char *content = buf.data();
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const size_t content_size = buf.size();
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const size_t hmac_size = hmac.output_size();
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unsigned char *hmac_buf = buf.prepend_alloc(hmac_size);
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hmac.hmac(hmac_buf, hmac_size, content, content_size);
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}
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}
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BufferAllocated work;
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};
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} // namespace openvpn
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#endif // OPENVPN_CRYPTO_ENCRYPT_H
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