xref: /openssh-portable/kex.h (revision 3dd0c64e)
1 /* $OpenBSD: kex.h,v 1.114 2021/01/31 22:55:29 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@openssh.com"
66 
67 #define COMP_NONE	0
68 /* pre-auth compression (COMP_ZLIB) is only supported in the client */
69 #define COMP_ZLIB	1
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,
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_MAX
106 };
107 
108 #define KEX_INIT_SENT	0x0001
109 #define KEX_INITIAL	0x0002
110 
111 struct sshenc {
112 	char	*name;
113 	const struct sshcipher *cipher;
114 	int	enabled;
115 	u_int	key_len;
116 	u_int	iv_len;
117 	u_int	block_size;
118 	u_char	*key;
119 	u_char	*iv;
120 };
121 struct sshcomp {
122 	u_int	type;
123 	int	enabled;
124 	char	*name;
125 };
126 struct newkeys {
127 	struct sshenc	enc;
128 	struct sshmac	mac;
129 	struct sshcomp  comp;
130 };
131 
132 struct ssh;
133 
134 struct kex {
135 	struct newkeys	*newkeys[MODE_MAX];
136 	u_int	we_need;
137 	u_int	dh_need;
138 	int	server;
139 	char	*name;
140 	char	*hostkey_alg;
141 	int	hostkey_type;
142 	int	hostkey_nid;
143 	u_int	kex_type;
144 	char	*server_sig_algs;
145 	int	ext_info_c;
146 	struct sshbuf *my;
147 	struct sshbuf *peer;
148 	struct sshbuf *client_version;
149 	struct sshbuf *server_version;
150 	struct sshbuf *session_id;
151 	sig_atomic_t done;
152 	u_int	flags;
153 	int	hash_alg;
154 	int	ec_nid;
155 	char	*failed_choice;
156 	int	(*verify_host_key)(struct sshkey *, struct ssh *);
157 	struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
158 	struct sshkey *(*load_host_private_key)(int, int, struct ssh *);
159 	int	(*host_key_index)(struct sshkey *, int, struct ssh *);
160 	int	(*sign)(struct ssh *, struct sshkey *, struct sshkey *,
161 	    u_char **, size_t *, const u_char *, size_t, const char *);
162 	int	(*kex[KEX_MAX])(struct ssh *);
163 	/* kex specific state */
164 	DH	*dh;			/* DH */
165 	u_int	min, max, nbits;	/* GEX */
166 	EC_KEY	*ec_client_key;		/* ECDH */
167 	const EC_GROUP *ec_group;	/* ECDH */
168 	u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 + KEM */
169 	u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
170 	u_char sntrup761_client_key[crypto_kem_sntrup761_SECRETKEYBYTES]; /* KEM */
171 	struct sshbuf *client_pub;
172 };
173 
174 int	 kex_names_valid(const char *);
175 char	*kex_alg_list(char);
176 char	*kex_names_cat(const char *, const char *);
177 int	 kex_assemble_names(char **, const char *, const char *);
178 
179 int	 kex_exchange_identification(struct ssh *, int, const char *);
180 
181 struct kex *kex_new(void);
182 int	 kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
183 int	 kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
184 void	 kex_free_newkeys(struct newkeys *);
185 void	 kex_free(struct kex *);
186 
187 int	 kex_buf2prop(struct sshbuf *, int *, char ***);
188 int	 kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
189 void	 kex_prop_free(char **);
190 int	 kex_load_hostkey(struct ssh *, struct sshkey **, struct sshkey **);
191 int	 kex_verify_host_key(struct ssh *, struct sshkey *);
192 
193 int	 kex_send_kexinit(struct ssh *);
194 int	 kex_input_kexinit(int, u_int32_t, struct ssh *);
195 int	 kex_input_ext_info(int, u_int32_t, struct ssh *);
196 int	 kex_protocol_error(int, u_int32_t, struct ssh *);
197 int	 kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
198 int	 kex_send_newkeys(struct ssh *);
199 int	 kex_start_rekex(struct ssh *);
200 
201 int	 kexgex_client(struct ssh *);
202 int	 kexgex_server(struct ssh *);
203 int	 kex_gen_client(struct ssh *);
204 int	 kex_gen_server(struct ssh *);
205 
206 int	 kex_dh_keypair(struct kex *);
207 int	 kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
208     struct sshbuf **);
209 int	 kex_dh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
210 
211 int	 kex_ecdh_keypair(struct kex *);
212 int	 kex_ecdh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
213     struct sshbuf **);
214 int	 kex_ecdh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
215 
216 int	 kex_c25519_keypair(struct kex *);
217 int	 kex_c25519_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
218     struct sshbuf **);
219 int	 kex_c25519_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
220 
221 int	 kex_kem_sntrup761x25519_keypair(struct kex *);
222 int	 kex_kem_sntrup761x25519_enc(struct kex *, const struct sshbuf *,
223     struct sshbuf **, struct sshbuf **);
224 int	 kex_kem_sntrup761x25519_dec(struct kex *, const struct sshbuf *,
225     struct sshbuf **);
226 
227 int	 kex_dh_keygen(struct kex *);
228 int	 kex_dh_compute_key(struct kex *, BIGNUM *, struct sshbuf *);
229 
230 int	 kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
231     const struct sshbuf *, const struct sshbuf *, const struct sshbuf *,
232     int, int, int,
233     const BIGNUM *, const BIGNUM *, const BIGNUM *,
234     const BIGNUM *, const u_char *, size_t,
235     u_char *, size_t *);
236 
237 void	kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
238 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
239 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
240 int	kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
241     const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
242 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
243 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
244 int	kexc25519_shared_key_ext(const u_char key[CURVE25519_SIZE],
245     const u_char pub[CURVE25519_SIZE], struct sshbuf *out, int)
246 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
247 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
248 
249 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
250 void	dump_digest(const char *, const u_char *, int);
251 #endif
252 
253 #if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC)
254 # undef EC_KEY
255 # undef EC_GROUP
256 # undef EC_POINT
257 #endif
258 
259 #endif
260