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openssh-portable/kex.h
djm@openbsd.org f68312eb59
upstream: Add experimental support for hybrid post-quantum key exchange 
ML-KEM768 with ECDH/X25519 from the Internet-draft:
https://datatracker.ietf.org/doc/html/draft-kampanakis-curdle-ssh-pq-ke-03

This is based on previous patches from markus@ but adapted to use the
final FIPS203 standard ML-KEM using a formally-verified implementation
from libcrux.

Note this key exchange method is still a draft and thus subject to
change. It is therefore disabled by default; set MLKEM=yes to build it.
We're making it available now to make it easy for other SSH
implementations to test against it.

ok markus@ deraadt@

OpenBSD-Commit-ID: 02a8730a570b63fa8acd9913ec66353735dea42c
2024-09-02 22:32:44 +10:00

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/* $OpenBSD: kex.h,v 1.126 2024/09/02 12:13:56 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 "mac.h"
#include "crypto_api.h"
#ifdef WITH_OPENSSL
# include <openssl/bn.h>
# include <openssl/dh.h>
# include <openssl/ecdsa.h>
# ifdef OPENSSL_HAS_ECC
# include <openssl/ec.h>
# else /* OPENSSL_HAS_ECC */
# define EC_KEY void
# define EC_GROUP void
# define EC_POINT void
# endif /* OPENSSL_HAS_ECC */
#else /* WITH_OPENSSL */
# define DH void
# define BIGNUM void
# define EC_KEY void
# define EC_GROUP void
# define EC_POINT void
#endif /* WITH_OPENSSL */
#define KEX_COOKIE_LEN 16
#define KEX_DH1 "diffie-hellman-group1-sha1"
#define KEX_DH14_SHA1 "diffie-hellman-group14-sha1"
#define KEX_DH14_SHA256 "diffie-hellman-group14-sha256"
#define KEX_DH16_SHA512 "diffie-hellman-group16-sha512"
#define KEX_DH18_SHA512 "diffie-hellman-group18-sha512"
#define KEX_DHGEX_SHA1 "diffie-hellman-group-exchange-sha1"
#define KEX_DHGEX_SHA256 "diffie-hellman-group-exchange-sha256"
#define KEX_ECDH_SHA2_NISTP256 "ecdh-sha2-nistp256"
#define KEX_ECDH_SHA2_NISTP384 "ecdh-sha2-nistp384"
#define KEX_ECDH_SHA2_NISTP521 "ecdh-sha2-nistp521"
#define KEX_CURVE25519_SHA256 "curve25519-sha256"
#define KEX_CURVE25519_SHA256_OLD "curve25519-sha256@libssh.org"
#define KEX_SNTRUP761X25519_SHA512 "sntrup761x25519-sha512"
#define KEX_SNTRUP761X25519_SHA512_OLD "sntrup761x25519-sha512@openssh.com"
#define KEX_MLKEM768X25519_SHA256 "mlkem768x25519-sha256"
#define COMP_NONE 0
#define COMP_DELAYED 2
#define CURVE25519_SIZE 32
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 = 1,
KEX_DH_GRP14_SHA1,
KEX_DH_GRP14_SHA256,
KEX_DH_GRP16_SHA512,
KEX_DH_GRP18_SHA512,
KEX_DH_GEX_SHA1,
KEX_DH_GEX_SHA256,
KEX_ECDH_SHA2,
KEX_C25519_SHA256,
KEX_KEM_SNTRUP761X25519_SHA512,
KEX_KEM_MLKEM768X25519_SHA256,
KEX_MAX
};
/* kex->flags */
#define KEX_INIT_SENT 0x0001
#define KEX_INITIAL 0x0002
#define KEX_HAS_PUBKEY_HOSTBOUND 0x0004
#define KEX_RSA_SHA2_256_SUPPORTED 0x0008 /* only set in server for now */
#define KEX_RSA_SHA2_512_SUPPORTED 0x0010 /* only set in server for now */
#define KEX_HAS_PING 0x0020
#define KEX_HAS_EXT_INFO_IN_AUTH 0x0040
struct sshenc {
char *name;
const struct sshcipher *cipher;
int enabled;
u_int key_len;
u_int iv_len;
u_int block_size;
u_char *key;
u_char *iv;
};
struct sshcomp {
u_int type;
int enabled;
char *name;
};
struct newkeys {
struct sshenc enc;
struct sshmac mac;
struct sshcomp comp;
};
struct ssh;
struct sshbuf;
struct kex {
struct newkeys *newkeys[MODE_MAX];
u_int we_need;
u_int dh_need;
int server;
char *name;
char *hostkey_alg;
int hostkey_type;
int hostkey_nid;
u_int kex_type;
char *server_sig_algs;
int ext_info_c;
int ext_info_s;
int kex_strict;
int ext_info_received;
struct sshbuf *my;
struct sshbuf *peer;
struct sshbuf *client_version;
struct sshbuf *server_version;
struct sshbuf *session_id;
struct sshbuf *initial_sig;
struct sshkey *initial_hostkey;
sig_atomic_t done;
u_int flags;
int hash_alg;
int ec_nid;
char *failed_choice;
int (*verify_host_key)(struct sshkey *, struct ssh *);
struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
struct sshkey *(*load_host_private_key)(int, int, struct ssh *);
int (*host_key_index)(struct sshkey *, int, struct ssh *);
int (*sign)(struct ssh *, struct sshkey *, struct sshkey *,
u_char **, size_t *, const u_char *, size_t, const char *);
int (*kex[KEX_MAX])(struct ssh *);
/* kex specific state */
DH *dh; /* DH */
u_int min, max, nbits; /* GEX */
EC_KEY *ec_client_key; /* ECDH */
const EC_GROUP *ec_group; /* ECDH */
u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 + KEM */
u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
u_char sntrup761_client_key[crypto_kem_sntrup761_SECRETKEYBYTES]; /* KEM */
u_char mlkem768_client_key[crypto_kem_mlkem768_SECRETKEYBYTES]; /* KEM */
struct sshbuf *client_pub;
};
int kex_name_valid(const char *);
u_int kex_type_from_name(const char *);
int kex_hash_from_name(const char *);
int kex_nid_from_name(const char *);
int kex_names_valid(const char *);
char *kex_alg_list(char);
char *kex_names_cat(const char *, const char *);
int kex_has_any_alg(const char *, const char *);
int kex_assemble_names(char **, const char *, const char *);
void kex_proposal_populate_entries(struct ssh *, char *prop[PROPOSAL_MAX],
const char *, const char *, const char *, const char *, const char *);
void kex_proposal_free_entries(char *prop[PROPOSAL_MAX]);
int kex_exchange_identification(struct ssh *, int, const char *);
struct kex *kex_new(void);
int kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
int kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
void kex_free_newkeys(struct newkeys *);
void kex_free(struct kex *);
int kex_buf2prop(struct sshbuf *, int *, char ***);
int kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
void kex_prop_free(char **);
int kex_load_hostkey(struct ssh *, struct sshkey **, struct sshkey **);
int kex_verify_host_key(struct ssh *, struct sshkey *);
int kex_send_kexinit(struct ssh *);
int kex_input_kexinit(int, u_int32_t, struct ssh *);
int kex_input_ext_info(int, u_int32_t, struct ssh *);
int kex_protocol_error(int, u_int32_t, struct ssh *);
int kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
int kex_send_newkeys(struct ssh *);
int kex_start_rekex(struct ssh *);
int kex_server_update_ext_info(struct ssh *);
void kex_set_server_sig_algs(struct ssh *, const char *);
int kexgex_client(struct ssh *);
int kexgex_server(struct ssh *);
int kex_gen_client(struct ssh *);
int kex_gen_server(struct ssh *);
int kex_dh_keypair(struct kex *);
int kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
struct sshbuf **);
int kex_dh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
int kex_ecdh_keypair(struct kex *);
int kex_ecdh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
struct sshbuf **);
int kex_ecdh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
int kex_c25519_keypair(struct kex *);
int kex_c25519_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
struct sshbuf **);
int kex_c25519_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
int kex_kem_sntrup761x25519_keypair(struct kex *);
int kex_kem_sntrup761x25519_enc(struct kex *, const struct sshbuf *,
struct sshbuf **, struct sshbuf **);
int kex_kem_sntrup761x25519_dec(struct kex *, const struct sshbuf *,
struct sshbuf **);
int kex_kem_mlkem768x25519_keypair(struct kex *);
int kex_kem_mlkem768x25519_enc(struct kex *, const struct sshbuf *,
struct sshbuf **, struct sshbuf **);
int kex_kem_mlkem768x25519_dec(struct kex *, const struct sshbuf *,
struct sshbuf **);
int kex_dh_keygen(struct kex *);
int kex_dh_compute_key(struct kex *, BIGNUM *, struct sshbuf *);
int kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
const struct sshbuf *, const struct sshbuf *, const struct sshbuf *,
int, int, int,
const BIGNUM *, const BIGNUM *, const BIGNUM *,
const BIGNUM *, const u_char *, size_t,
u_char *, size_t *);
void kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
int kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
int kexc25519_shared_key_ext(const u_char key[CURVE25519_SIZE],
const u_char pub[CURVE25519_SIZE], struct sshbuf *out, int)
__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
void dump_digest(const char *, const u_char *, int);
#endif
#if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC)
# undef EC_KEY
# undef EC_GROUP
# undef EC_POINT
#endif
#endif
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