kex.h

   1 /* $OpenBSD: kex.h,v 1.126 2024/09/02 12:13:56 djm Exp $ */
   2
   3 /*
   4  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26 #ifndef KEX_H
  27 #define KEX_H
  28
  29 #include "mac.h"
  30 #include "crypto_api.h"
  31
  32 #ifdef WITH_OPENSSL
  33 # include <openssl/bn.h>
  34 # include <openssl/dh.h>
  35 # include <openssl/ecdsa.h>
  36 # ifdef OPENSSL_HAS_ECC
  37 #  include <openssl/ec.h>
  38 # else /* OPENSSL_HAS_ECC */
  39 #  define EC_KEY        void
  40 #  define EC_GROUP      void
  41 #  define EC_POINT      void
  42 # endif /* OPENSSL_HAS_ECC */
  43 #else /* WITH_OPENSSL */
  44 # define DH             void
  45 # define BIGNUM         void
  46 # define EC_KEY         void
  47 # define EC_GROUP       void
  48 # define EC_POINT       void
  49 #endif /* WITH_OPENSSL */
  50
  51 #define KEX_COOKIE_LEN  16
  52
  53 #define KEX_DH1                         "diffie-hellman-group1-sha1"
  54 #define KEX_DH14_SHA1                   "diffie-hellman-group14-sha1"
  55 #define KEX_DH14_SHA256                 "diffie-hellman-group14-sha256"
  56 #define KEX_DH16_SHA512                 "diffie-hellman-group16-sha512"
  57 #define KEX_DH18_SHA512                 "diffie-hellman-group18-sha512"
  58 #define KEX_DHGEX_SHA1                  "diffie-hellman-group-exchange-sha1"
  59 #define KEX_DHGEX_SHA256                "diffie-hellman-group-exchange-sha256"
  60 #define KEX_ECDH_SHA2_NISTP256          "ecdh-sha2-nistp256"
  61 #define KEX_ECDH_SHA2_NISTP384          "ecdh-sha2-nistp384"
  62 #define KEX_ECDH_SHA2_NISTP521          "ecdh-sha2-nistp521"
  63 #define KEX_CURVE25519_SHA256           "curve25519-sha256"
  64 #define KEX_CURVE25519_SHA256_OLD       "curve25519-sha256@libssh.org"
  65 #define KEX_SNTRUP761X25519_SHA512      "sntrup761x25519-sha512"
  66 #define KEX_SNTRUP761X25519_SHA512_OLD  "sntrup761x25519-sha512@openssh.com"
  67 #define KEX_MLKEM768X25519_SHA256       "mlkem768x25519-sha256"
  68
  69 #define COMP_NONE       0
  70 #define COMP_DELAYED    2
  71
  72 #define CURVE25519_SIZE 32
  73
  74 enum kex_init_proposals {
  75         PROPOSAL_KEX_ALGS,
  76         PROPOSAL_SERVER_HOST_KEY_ALGS,
  77         PROPOSAL_ENC_ALGS_CTOS,
  78         PROPOSAL_ENC_ALGS_STOC,
  79         PROPOSAL_MAC_ALGS_CTOS,
  80         PROPOSAL_MAC_ALGS_STOC,
  81         PROPOSAL_COMP_ALGS_CTOS,
  82         PROPOSAL_COMP_ALGS_STOC,
  83         PROPOSAL_LANG_CTOS,
  84         PROPOSAL_LANG_STOC,
  85         PROPOSAL_MAX
  86 };
  87
  88 enum kex_modes {
  89         MODE_IN,
  90         MODE_OUT,
  91         MODE_MAX
  92 };
  93
  94 enum kex_exchange {
  95         KEX_DH_GRP1_SHA1 = 1,
  96         KEX_DH_GRP14_SHA1,
  97         KEX_DH_GRP14_SHA256,
  98         KEX_DH_GRP16_SHA512,
  99         KEX_DH_GRP18_SHA512,
 100         KEX_DH_GEX_SHA1,
 101         KEX_DH_GEX_SHA256,
 102         KEX_ECDH_SHA2,
 103         KEX_C25519_SHA256,
 104         KEX_KEM_SNTRUP761X25519_SHA512,
 105         KEX_KEM_MLKEM768X25519_SHA256,
 106         KEX_MAX
 107 };
 108
 109 /* kex->flags */
 110 #define KEX_INIT_SENT                   0x0001
 111 #define KEX_INITIAL                     0x0002
 112 #define KEX_HAS_PUBKEY_HOSTBOUND        0x0004
 113 #define KEX_RSA_SHA2_256_SUPPORTED      0x0008 /* only set in server for now */
 114 #define KEX_RSA_SHA2_512_SUPPORTED      0x0010 /* only set in server for now */
 115 #define KEX_HAS_PING                    0x0020
 116 #define KEX_HAS_EXT_INFO_IN_AUTH        0x0040
 117
 118 struct sshenc {
 119         char    *name;
 120         const struct sshcipher *cipher;
 121         int     enabled;
 122         u_int   key_len;
 123         u_int   iv_len;
 124         u_int   block_size;
 125         u_char  *key;
 126         u_char  *iv;
 127 };
 128 struct sshcomp {
 129         u_int   type;
 130         int     enabled;
 131         char    *name;
 132 };
 133 struct newkeys {
 134         struct sshenc   enc;
 135         struct sshmac   mac;
 136         struct sshcomp  comp;
 137 };
 138
 139 struct ssh;
 140 struct sshbuf;
 141
 142 struct kex {
 143         struct newkeys  *newkeys[MODE_MAX];
 144         u_int   we_need;
 145         u_int   dh_need;
 146         int     server;
 147         char    *name;
 148         char    *hostkey_alg;
 149         int     hostkey_type;
 150         int     hostkey_nid;
 151         u_int   kex_type;
 152         char    *server_sig_algs;
 153         int     ext_info_c;
 154         int     ext_info_s;
 155         int     kex_strict;
 156         int     ext_info_received;
 157         struct sshbuf *my;
 158         struct sshbuf *peer;
 159         struct sshbuf *client_version;
 160         struct sshbuf *server_version;
 161         struct sshbuf *session_id;
 162         struct sshbuf *initial_sig;
 163         struct sshkey *initial_hostkey;
 164         sig_atomic_t done;
 165         u_int   flags;
 166         int     hash_alg;
 167         int     ec_nid;
 168         char    *failed_choice;
 169         int     (*verify_host_key)(struct sshkey *, struct ssh *);
 170         struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
 171         struct sshkey *(*load_host_private_key)(int, int, struct ssh *);
 172         int     (*host_key_index)(struct sshkey *, int, struct ssh *);
 173         int     (*sign)(struct ssh *, struct sshkey *, struct sshkey *,
 174             u_char **, size_t *, const u_char *, size_t, const char *);
 175         int     (*kex[KEX_MAX])(struct ssh *);
 176         /* kex specific state */
 177         DH      *dh;                    /* DH */
 178         u_int   min, max, nbits;        /* GEX */
 179         EC_KEY  *ec_client_key;         /* ECDH */
 180         const EC_GROUP *ec_group;       /* ECDH */
 181         u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 + KEM */
 182         u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
 183         u_char sntrup761_client_key[crypto_kem_sntrup761_SECRETKEYBYTES]; /* KEM */
 184         u_char mlkem768_client_key[crypto_kem_mlkem768_SECRETKEYBYTES]; /* KEM */
 185         struct sshbuf *client_pub;
 186 };
 187
 188 int      kex_name_valid(const char *);
 189 u_int    kex_type_from_name(const char *);
 190 int      kex_hash_from_name(const char *);
 191 int      kex_nid_from_name(const char *);
 192 int      kex_names_valid(const char *);
 193 char    *kex_alg_list(char);
 194 char    *kex_names_cat(const char *, const char *);
 195 int      kex_has_any_alg(const char *, const char *);
 196 int      kex_assemble_names(char **, const char *, const char *);
 197 void     kex_proposal_populate_entries(struct ssh *, char *prop[PROPOSAL_MAX],
 198     const char *, const char *, const char *, const char *, const char *);
 199 void     kex_proposal_free_entries(char *prop[PROPOSAL_MAX]);
 200
 201 int      kex_exchange_identification(struct ssh *, int, const char *);
 202
 203 struct kex *kex_new(void);
 204 int      kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
 205 int      kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
 206 void     kex_free_newkeys(struct newkeys *);
 207 void     kex_free(struct kex *);
 208
 209 int      kex_buf2prop(struct sshbuf *, int *, char ***);
 210 int      kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
 211 void     kex_prop_free(char **);
 212 int      kex_load_hostkey(struct ssh *, struct sshkey **, struct sshkey **);
 213 int      kex_verify_host_key(struct ssh *, struct sshkey *);
 214
 215 int      kex_send_kexinit(struct ssh *);
 216 int      kex_input_kexinit(int, u_int32_t, struct ssh *);
 217 int      kex_input_ext_info(int, u_int32_t, struct ssh *);
 218 int      kex_protocol_error(int, u_int32_t, struct ssh *);
 219 int      kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
 220 int      kex_send_newkeys(struct ssh *);
 221 int      kex_start_rekex(struct ssh *);
 222 int      kex_server_update_ext_info(struct ssh *);
 223 void     kex_set_server_sig_algs(struct ssh *, const char *);
 224
 225 int      kexgex_client(struct ssh *);
 226 int      kexgex_server(struct ssh *);
 227 int      kex_gen_client(struct ssh *);
 228 int      kex_gen_server(struct ssh *);
 229
 230 int      kex_dh_keypair(struct kex *);
 231 int      kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
 232     struct sshbuf **);
 233 int      kex_dh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
 234
 235 int      kex_ecdh_keypair(struct kex *);
 236 int      kex_ecdh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
 237     struct sshbuf **);
 238 int      kex_ecdh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
 239
 240 int      kex_c25519_keypair(struct kex *);
 241 int      kex_c25519_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
 242     struct sshbuf **);
 243 int      kex_c25519_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
 244
 245 int      kex_kem_sntrup761x25519_keypair(struct kex *);
 246 int      kex_kem_sntrup761x25519_enc(struct kex *, const struct sshbuf *,
 247     struct sshbuf **, struct sshbuf **);
 248 int      kex_kem_sntrup761x25519_dec(struct kex *, const struct sshbuf *,
 249     struct sshbuf **);
 250
 251 int      kex_kem_mlkem768x25519_keypair(struct kex *);
 252 int      kex_kem_mlkem768x25519_enc(struct kex *, const struct sshbuf *,
 253     struct sshbuf **, struct sshbuf **);
 254 int      kex_kem_mlkem768x25519_dec(struct kex *, const struct sshbuf *,
 255     struct sshbuf **);
 256
 257 int      kex_dh_keygen(struct kex *);
 258 int      kex_dh_compute_key(struct kex *, BIGNUM *, struct sshbuf *);
 259
 260 int      kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
 261     const struct sshbuf *, const struct sshbuf *, const struct sshbuf *,
 262     int, int, int,
 263     const BIGNUM *, const BIGNUM *, const BIGNUM *,
 264     const BIGNUM *, const u_char *, size_t,
 265     u_char *, size_t *);
 266
 267 void    kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
 268         __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
 269         __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
 270 int     kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
 271     const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
 272         __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
 273         __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
 274 int     kexc25519_shared_key_ext(const u_char key[CURVE25519_SIZE],
 275     const u_char pub[CURVE25519_SIZE], struct sshbuf *out, int)
 276         __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
 277         __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
 278
 279 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
 280 void    dump_digest(const char *, const u_char *, int);
 281 #endif
 282
 283 #if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC)
 284 # undef EC_KEY
 285 # undef EC_GROUP
 286 # undef EC_POINT
 287 #endif
 288
 289 #endif