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Add support for certificate key types for users and hosts.

OpenSSH certificate key types are not X.509 certificates, but a much
simpler format that encodes a public key, identity information and
some validity constraints and signs it with a CA key. CA keys are
regular SSH keys. This certificate style avoids the attack surface
of X.509 certificates and is very easy to deploy.

Certified host keys allow automatic acceptance of new host keys
when a CA certificate is marked as trusted in ~/.ssh/known_hosts.
see VERIFYING HOST KEYS in ssh(1) for details.

Certified user keys allow authentication of users when the signing
CA key is marked as trusted in authorized_keys. See "AUTHORIZED_KEYS
FILE FORMAT" in sshd(8) for details.

Certificates are minted using ssh-keygen(1), documentation is in
the "CERTIFICATES" section of that manpage.

Documentation on the format of certificates is in the file
PROTOCOL.certkeys

feedback and ok markus@

/* $OpenBSD: kex.h,v 1.49 2010/02/26 20:29:54 djm Exp $ */

/*
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#ifndef KEX_H
#define KEX_H

#include <openssl/evp.h>
#include <openssl/hmac.h>

#define KEX_COOKIE_LEN	16

#define	KEX_DH1			"diffie-hellman-group1-sha1"
#define	KEX_DH14		"diffie-hellman-group14-sha1"
#define	KEX_DHGEX_SHA1		"diffie-hellman-group-exchange-sha1"
#define	KEX_DHGEX_SHA256	"diffie-hellman-group-exchange-sha256"
#define	KEX_RESUME		"resume@appgate.com"

#define COMP_NONE	0
#define COMP_ZLIB	1
#define COMP_DELAYED	2

enum kex_init_proposals {
	PROPOSAL_KEX_ALGS,
	PROPOSAL_SERVER_HOST_KEY_ALGS,
	PROPOSAL_ENC_ALGS_CTOS,
	PROPOSAL_ENC_ALGS_STOC,
	PROPOSAL_MAC_ALGS_CTOS,
	PROPOSAL_MAC_ALGS_STOC,
	PROPOSAL_COMP_ALGS_CTOS,
	PROPOSAL_COMP_ALGS_STOC,
	PROPOSAL_LANG_CTOS,
	PROPOSAL_LANG_STOC,
	PROPOSAL_MAX
};

enum kex_modes {
	MODE_IN,
	MODE_OUT,
	MODE_MAX
};

enum kex_exchange {
	KEX_DH_GRP1_SHA1,
	KEX_DH_GRP14_SHA1,
	KEX_DH_GEX_SHA1,
	KEX_DH_GEX_SHA256,
	KEX_MAX
};

#define KEX_INIT_SENT	0x0001

typedef struct Kex Kex;
typedef struct Mac Mac;
typedef struct Comp Comp;
typedef struct Enc Enc;
typedef struct Newkeys Newkeys;

struct Enc {
	char	*name;
	Cipher	*cipher;
	int	enabled;
	u_int	key_len;
	u_int	block_size;
	u_char	*key;
	u_char	*iv;
};
struct Mac {
	char	*name;
	int	enabled;
	u_int	mac_len;
	u_char	*key;
	u_int	key_len;
	int	type;
	const EVP_MD	*evp_md;
	HMAC_CTX	evp_ctx;
	struct umac_ctx *umac_ctx;
};
struct Comp {
	int	type;
	int	enabled;
	char	*name;
};
struct Newkeys {
	Enc	enc;
	Mac	mac;
	Comp	comp;
};
struct Kex {
	u_char	*session_id;
	u_int	session_id_len;
	Newkeys	*newkeys[MODE_MAX];
	u_int	we_need;
	int	server;
	char	*name;
	int	hostkey_type;
	int	kex_type;
	int	roaming;
	Buffer	my;
	Buffer	peer;
	sig_atomic_t done;
	int	flags;
	const EVP_MD *evp_md;
	char	*client_version_string;
	char	*server_version_string;
	int	(*verify_host_key)(Key *);
	Key	*(*load_host_public_key)(int);
	Key	*(*load_host_private_key)(int);
	int	(*host_key_index)(Key *);
	void	(*kex[KEX_MAX])(Kex *);
};

Kex	*kex_setup(char *[PROPOSAL_MAX]);
void	 kex_finish(Kex *);

void	 kex_send_kexinit(Kex *);
void	 kex_input_kexinit(int, u_int32_t, void *);
void	 kex_derive_keys(Kex *, u_char *, u_int, BIGNUM *);

Newkeys *kex_get_newkeys(int);

void	 kexdh_client(Kex *);
void	 kexdh_server(Kex *);
void	 kexgex_client(Kex *);
void	 kexgex_server(Kex *);

void
kex_dh_hash(char *, char *, char *, int, char *, int, u_char *, int,
    BIGNUM *, BIGNUM *, BIGNUM *, u_char **, u_int *);
void
kexgex_hash(const EVP_MD *, char *, char *, char *, int, char *,
    int, u_char *, int, int, int, int, BIGNUM *, BIGNUM *, BIGNUM *,
    BIGNUM *, BIGNUM *, u_char **, u_int *);

void
derive_ssh1_session_id(BIGNUM *, BIGNUM *, u_int8_t[8], u_int8_t[16]);

#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
void	dump_digest(char *, u_char *, int);
#endif

#endif