New upstream version 2.4~beta1upstream/2.4_beta1

1 files changed, 144 insertions, 0 deletions

diff --git a/src/openvpn/tls_crypt.h b/src/openvpn/tls_crypt.h
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+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2016 Fox Crypto B.V. <openvpn@fox-it.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program (see the file COPYING included with this
+ *  distribution); if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/**
+ * @defgroup tls_crypt Control channel encryption (--tls-crypt)
+ * @ingroup control_tls
+ * @{
+ *
+ * @par
+ * Control channel encryption uses a pre-shared static key (like the --tls-auth
+ * key) to encrypt control channel packets.
+ *
+ * @par
+ * Encrypting control channel packets has three main advantages:
+ *  - It provides more privacy by hiding the certificate used for the TLS
+ *    connection.
+ *  - It is harder to identify OpenVPN traffic as such.
+ *  - It provides "poor-man's" post-quantum security, against attackers who
+ *    will never know the pre-shared key (i.e. no forward secrecy).
+ *
+ * @par Specification
+ * Control channel encryption is based on the SIV construction [0], to achieve
+ * nonce misuse-resistant authenticated encryption:
+ *
+ * @par
+ * \code{.unparsed}
+ * msg      = control channel plaintext
+ * header   = opcode (1 byte) || session_id (8 bytes) || packet_id (8 bytes)
+ * Ka       = authentication key (256 bits)
+ * Ke       = encryption key (256 bits)
+ * (Ka and Ke are pre-shared keys, like with --tls-auth)
+ *
+ * auth_tag = HMAC-SHA256(Ka, header || msg)
+ * IV       = 128 most-significant bits of auth_tag
+ * ciph     = AES256-CTR(Ke, IV, msg)
+ *
+ * output   = Header || Tag || Ciph
+ * \endcode
+ *
+ * @par
+ * This boils down to the following on-the-wire packet format:
+ *
+ * @par
+ * \code{.unparsed}
+ * - opcode - || - session_id - || - packet_id - || auth_tag || * payload *
+ * \endcode
+ *
+ * @par
+ * Where
+ * <tt>- XXX -</tt> means authenticated, and
+ * <tt>* XXX *</tt> means authenticated and encrypted.
+ */
+
+#ifndef TLSCRYPT_H
+#define TLSCRYPT_H
+
+#include "buffer.h"
+#include "crypto.h"
+#include "session_id.h"
+
+#define TLS_CRYPT_TAG_SIZE (256/8)
+#define TLS_CRYPT_PID_SIZE (sizeof (packet_id_type) + sizeof (net_time_t))
+#define TLS_CRYPT_BLOCK_SIZE (128/8)
+
+#define TLS_CRYPT_OFF_PID (1 + SID_SIZE)
+#define TLS_CRYPT_OFF_TAG (TLS_CRYPT_OFF_PID + TLS_CRYPT_PID_SIZE)
+#define TLS_CRYPT_OFF_CT (TLS_CRYPT_OFF_TAG + TLS_CRYPT_TAG_SIZE)
+
+/**
+ * Initialize a key_ctx_bi structure for use with --tls-crypt.
+ *
+ * @param key		The key context to initialize
+ * @param key_file	The file to read the key from (or the inline tag to
+ *			indicate and inline key).
+ * @param key_inline	Array containing (zero-terminated) inline key, or NULL
+ *			if not used.
+ * @param tls_server	Must be set to true is this is a TLS server instance.
+ */
+void tls_crypt_init_key (struct key_ctx_bi *key, const char *key_file,
+    const char *key_inline, bool tls_server);
+
+/**
+ * Returns the maximum overhead (in bytes) added to the destination buffer by
+ * tls_crypt_wrap().
+ */
+int tls_crypt_buf_overhead(void);
+
+/**
+ * Adjust frame parameters for --tls-crypt overhead.
+ */
+void tls_crypt_adjust_frame_parameters(struct frame *frame);
+
+/**
+ * Wrap a control channel packet (both authenticates and encrypts the data).
+ *
+ * @param src	Data to authenticate and encrypt.
+ * @param dst	Any data present in this buffer is first authenticated, then
+ *		the wrapped packet id and data from the src buffer are appended.
+ *		Must have at least tls_crypt_buf_overhead()+BLEN(src) headroom.
+ * @param opt	The crypto state for this --tls-crypt instance.
+ *
+ * @returns true iff wrapping succeeded.
+ */
+bool tls_crypt_wrap (const struct buffer *src, struct buffer *dst,
+	 struct crypto_options *opt);
+
+/**
+ * Unwrap a control channel packet (decrypts, authenticates and performs
+ * replay checks).
+ *
+ * @param src	Data to decrypt and authenticate.
+ * @param dst	Returns the decrypted data, if unwrapping was successful.
+ * @param opt	The crypto state for this --tls-crypt instance.
+ *
+ * @returns true iff unwrapping succeeded (data authenticated correctly and was
+ * no replay).
+ */
+bool tls_crypt_unwrap (const struct buffer *src, struct buffer *dst,
+    struct crypto_options *opt);
+
+/** @} */
+
+#endif /* TLSCRYPT_H */