1 /* $OpenBSD: kex.h,v 1.129 2026/03/05 05:40:36 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 #define KEX_HAS_NEWAGENT 0x0080 /* only set in client */ 118 119 /* kex->pq */ 120 #define KEX_NOT_PQ 0 121 #define KEX_IS_PQ 1 122 123 struct sshenc { 124 char *name; 125 const struct sshcipher *cipher; 126 int enabled; 127 u_int key_len; 128 u_int iv_len; 129 u_int block_size; 130 u_char *key; 131 u_char *iv; 132 }; 133 struct sshcomp { 134 u_int type; 135 int enabled; 136 char *name; 137 }; 138 struct newkeys { 139 struct sshenc enc; 140 struct sshmac mac; 141 struct sshcomp comp; 142 }; 143 144 struct ssh; 145 struct sshbuf; 146 147 struct kex { 148 struct newkeys *newkeys[MODE_MAX]; 149 u_int we_need; 150 u_int dh_need; 151 int server; 152 char *name; 153 char *hostkey_alg; 154 int hostkey_type; 155 int hostkey_nid; 156 u_int kex_type; 157 char *server_sig_algs; 158 int ext_info_c; 159 int ext_info_s; 160 int kex_strict; 161 int ext_info_received; 162 struct sshbuf *my; 163 struct sshbuf *peer; 164 struct sshbuf *client_version; 165 struct sshbuf *server_version; 166 struct sshbuf *session_id; 167 struct sshbuf *initial_sig; 168 struct sshkey *initial_hostkey; 169 sig_atomic_t done; 170 u_int flags; 171 int hash_alg; 172 int ec_nid; 173 char *failed_choice; 174 int (*verify_host_key)(struct sshkey *, struct ssh *); 175 struct sshkey *(*load_host_public_key)(int, int, struct ssh *); 176 struct sshkey *(*load_host_private_key)(int, int, struct ssh *); 177 int (*host_key_index)(struct sshkey *, int, struct ssh *); 178 int (*sign)(struct ssh *, struct sshkey *, struct sshkey *, 179 u_char **, size_t *, const u_char *, size_t, const char *); 180 int (*kex[KEX_MAX])(struct ssh *); 181 /* kex specific state */ 182 DH *dh; /* DH */ 183 u_int min, max, nbits; /* GEX */ 184 EC_KEY *ec_client_key; /* ECDH */ 185 const EC_GROUP *ec_group; /* ECDH */ 186 u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 + KEM */ 187 u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */ 188 u_char sntrup761_client_key[crypto_kem_sntrup761_SECRETKEYBYTES]; /* KEM */ 189 u_char mlkem768_client_key[crypto_kem_mlkem768_SECRETKEYBYTES]; /* KEM */ 190 struct sshbuf *client_pub; 191 }; 192 193 int kex_name_valid(const char *); 194 u_int kex_type_from_name(const char *); 195 int kex_hash_from_name(const char *); 196 int kex_nid_from_name(const char *); 197 int kex_is_pq_from_name(const char *); 198 int kex_names_valid(const char *); 199 char *kex_alg_list(char); 200 char *kex_names_cat(const char *, const char *); 201 int kex_has_any_alg(const char *, const char *); 202 int kex_assemble_names(char **, const char *, const char *); 203 void kex_proposal_populate_entries(struct ssh *, char *prop[PROPOSAL_MAX], 204 const char *, const char *, const char *, const char *, const char *); 205 void kex_proposal_free_entries(char *prop[PROPOSAL_MAX]); 206 207 int kex_exchange_identification(struct ssh *, int, const char *); 208 209 struct kex *kex_new(void); 210 int kex_ready(struct ssh *, char *[PROPOSAL_MAX]); 211 int kex_setup(struct ssh *, char *[PROPOSAL_MAX]); 212 void kex_free_newkeys(struct newkeys *); 213 void kex_free(struct kex *); 214 215 int kex_buf2prop(struct sshbuf *, int *, char ***); 216 int kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]); 217 void kex_prop_free(char **); 218 int kex_load_hostkey(struct ssh *, struct sshkey **, struct sshkey **); 219 int kex_verify_host_key(struct ssh *, struct sshkey *); 220 221 int kex_send_kexinit(struct ssh *); 222 int kex_input_kexinit(int, uint32_t, struct ssh *); 223 int kex_input_ext_info(int, uint32_t, struct ssh *); 224 int kex_protocol_error(int, uint32_t, struct ssh *); 225 int kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *); 226 int kex_send_newkeys(struct ssh *); 227 int kex_start_rekex(struct ssh *); 228 int kex_server_update_ext_info(struct ssh *); 229 void kex_set_server_sig_algs(struct ssh *, const char *); 230 231 int kexgex_client(struct ssh *); 232 int kexgex_server(struct ssh *); 233 int kex_gen_client(struct ssh *); 234 int kex_gen_server(struct ssh *); 235 236 int kex_dh_keypair(struct kex *); 237 int kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **, 238 struct sshbuf **); 239 int kex_dh_dec(struct kex *, const struct sshbuf *, struct sshbuf **); 240 241 int kex_ecdh_keypair(struct kex *); 242 int kex_ecdh_enc(struct kex *, const struct sshbuf *, struct sshbuf **, 243 struct sshbuf **); 244 int kex_ecdh_dec(struct kex *, const struct sshbuf *, struct sshbuf **); 245 246 int kex_c25519_keypair(struct kex *); 247 int kex_c25519_enc(struct kex *, const struct sshbuf *, struct sshbuf **, 248 struct sshbuf **); 249 int kex_c25519_dec(struct kex *, const struct sshbuf *, struct sshbuf **); 250 251 int kex_kem_sntrup761x25519_keypair(struct kex *); 252 int kex_kem_sntrup761x25519_enc(struct kex *, const struct sshbuf *, 253 struct sshbuf **, struct sshbuf **); 254 int kex_kem_sntrup761x25519_dec(struct kex *, const struct sshbuf *, 255 struct sshbuf **); 256 257 int kex_kem_mlkem768x25519_keypair(struct kex *); 258 int kex_kem_mlkem768x25519_enc(struct kex *, const struct sshbuf *, 259 struct sshbuf **, struct sshbuf **); 260 int kex_kem_mlkem768x25519_dec(struct kex *, const struct sshbuf *, 261 struct sshbuf **); 262 263 int kex_dh_keygen(struct kex *); 264 int kex_dh_compute_key(struct kex *, BIGNUM *, struct sshbuf *); 265 266 int kexgex_hash(int, const struct sshbuf *, const struct sshbuf *, 267 const struct sshbuf *, const struct sshbuf *, const struct sshbuf *, 268 int, int, int, 269 const BIGNUM *, const BIGNUM *, const BIGNUM *, 270 const BIGNUM *, const u_char *, size_t, 271 u_char *, size_t *); 272 273 void kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE]) 274 __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 275 __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))); 276 int kexc25519_shared_key(const u_char key[CURVE25519_SIZE], 277 const u_char pub[CURVE25519_SIZE], struct sshbuf *out) 278 __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 279 __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))); 280 int kexc25519_shared_key_ext(const u_char key[CURVE25519_SIZE], 281 const u_char pub[CURVE25519_SIZE], struct sshbuf *out, int) 282 __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE))) 283 __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE))); 284 285 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH) 286 void dump_digest(const char *, const u_char *, int); 287 #endif 288 289 #if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC) 290 # undef EC_KEY 291 # undef EC_GROUP 292 # undef EC_POINT 293 #endif 294 295 #endif 296