xref: /openssh-portable/kex.h (revision bb956eaa)
1 /* $OpenBSD: kex.h,v 1.107 2019/01/23 00:30:41 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_LEAKMALLOC
33 #include "leakmalloc.h"
34 #endif
35 
36 #ifdef WITH_OPENSSL
37 # ifdef OPENSSL_HAS_ECC
38 #  include <openssl/ec.h>
39 # else /* OPENSSL_HAS_ECC */
40 #  define EC_KEY	void
41 #  define EC_GROUP	void
42 #  define EC_POINT	void
43 # endif /* OPENSSL_HAS_ECC */
44 #else /* WITH_OPENSSL */
45 # define DH		void
46 # define BIGNUM		void
47 # define EC_KEY		void
48 # define EC_GROUP	void
49 # define EC_POINT	void
50 #endif /* WITH_OPENSSL */
51 
52 #define KEX_COOKIE_LEN	16
53 
54 #define	KEX_DH1				"diffie-hellman-group1-sha1"
55 #define	KEX_DH14_SHA1			"diffie-hellman-group14-sha1"
56 #define	KEX_DH14_SHA256			"diffie-hellman-group14-sha256"
57 #define	KEX_DH16_SHA512			"diffie-hellman-group16-sha512"
58 #define	KEX_DH18_SHA512			"diffie-hellman-group18-sha512"
59 #define	KEX_DHGEX_SHA1			"diffie-hellman-group-exchange-sha1"
60 #define	KEX_DHGEX_SHA256		"diffie-hellman-group-exchange-sha256"
61 #define	KEX_ECDH_SHA2_NISTP256		"ecdh-sha2-nistp256"
62 #define	KEX_ECDH_SHA2_NISTP384		"ecdh-sha2-nistp384"
63 #define	KEX_ECDH_SHA2_NISTP521		"ecdh-sha2-nistp521"
64 #define	KEX_CURVE25519_SHA256		"curve25519-sha256"
65 #define	KEX_CURVE25519_SHA256_OLD	"curve25519-sha256@libssh.org"
66 #define	KEX_SNTRUP4591761X25519_SHA512	"sntrup4591761x25519-sha512@tinyssh.org"
67 
68 #define COMP_NONE	0
69 /* pre-auth compression (COMP_ZLIB) is only supported in the client */
70 #define COMP_ZLIB	1
71 #define COMP_DELAYED	2
72 
73 #define CURVE25519_SIZE 32
74 
75 enum kex_init_proposals {
76 	PROPOSAL_KEX_ALGS,
77 	PROPOSAL_SERVER_HOST_KEY_ALGS,
78 	PROPOSAL_ENC_ALGS_CTOS,
79 	PROPOSAL_ENC_ALGS_STOC,
80 	PROPOSAL_MAC_ALGS_CTOS,
81 	PROPOSAL_MAC_ALGS_STOC,
82 	PROPOSAL_COMP_ALGS_CTOS,
83 	PROPOSAL_COMP_ALGS_STOC,
84 	PROPOSAL_LANG_CTOS,
85 	PROPOSAL_LANG_STOC,
86 	PROPOSAL_MAX
87 };
88 
89 enum kex_modes {
90 	MODE_IN,
91 	MODE_OUT,
92 	MODE_MAX
93 };
94 
95 enum kex_exchange {
96 	KEX_DH_GRP1_SHA1,
97 	KEX_DH_GRP14_SHA1,
98 	KEX_DH_GRP14_SHA256,
99 	KEX_DH_GRP16_SHA512,
100 	KEX_DH_GRP18_SHA512,
101 	KEX_DH_GEX_SHA1,
102 	KEX_DH_GEX_SHA256,
103 	KEX_ECDH_SHA2,
104 	KEX_C25519_SHA256,
105 	KEX_KEM_SNTRUP4591761X25519_SHA512,
106 	KEX_MAX
107 };
108 
109 #define KEX_INIT_SENT	0x0001
110 #define KEX_INITIAL	0x0002
111 
112 struct sshenc {
113 	char	*name;
114 	const struct sshcipher *cipher;
115 	int	enabled;
116 	u_int	key_len;
117 	u_int	iv_len;
118 	u_int	block_size;
119 	u_char	*key;
120 	u_char	*iv;
121 };
122 struct sshcomp {
123 	u_int	type;
124 	int	enabled;
125 	char	*name;
126 };
127 struct newkeys {
128 	struct sshenc	enc;
129 	struct sshmac	mac;
130 	struct sshcomp  comp;
131 };
132 
133 struct ssh;
134 
135 struct kex {
136 	u_char	*session_id;
137 	size_t	session_id_len;
138 	struct newkeys	*newkeys[MODE_MAX];
139 	u_int	we_need;
140 	u_int	dh_need;
141 	int	server;
142 	char	*name;
143 	char	*hostkey_alg;
144 	int	hostkey_type;
145 	int	hostkey_nid;
146 	u_int	kex_type;
147 	char	*server_sig_algs;
148 	int	ext_info_c;
149 	struct sshbuf *my;
150 	struct sshbuf *peer;
151 	struct sshbuf *client_version;
152 	struct sshbuf *server_version;
153 	sig_atomic_t done;
154 	u_int	flags;
155 	int	hash_alg;
156 	int	ec_nid;
157 	char	*failed_choice;
158 	int	(*verify_host_key)(struct sshkey *, struct ssh *);
159 	struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
160 	struct sshkey *(*load_host_private_key)(int, int, struct ssh *);
161 	int	(*host_key_index)(struct sshkey *, int, struct ssh *);
162 	int	(*sign)(struct ssh *, struct sshkey *, struct sshkey *,
163 	    u_char **, size_t *, const u_char *, size_t, const char *);
164 	int	(*kex[KEX_MAX])(struct ssh *);
165 	/* kex specific state */
166 	DH	*dh;			/* DH */
167 	u_int	min, max, nbits;	/* GEX */
168 	EC_KEY	*ec_client_key;		/* ECDH */
169 	const EC_GROUP *ec_group;	/* ECDH */
170 	u_char c25519_client_key[CURVE25519_SIZE]; /* 25519 + KEM */
171 	u_char c25519_client_pubkey[CURVE25519_SIZE]; /* 25519 */
172 	u_char sntrup4591761_client_key[crypto_kem_sntrup4591761_SECRETKEYBYTES]; /* KEM */
173 	struct sshbuf *client_pub;
174 };
175 
176 int	 kex_names_valid(const char *);
177 char	*kex_alg_list(char);
178 char	*kex_names_cat(const char *, const char *);
179 int	 kex_assemble_names(char **, const char *, const char *);
180 
181 int	 kex_exchange_identification(struct ssh *, int, const char *);
182 
183 struct kex *kex_new(void);
184 int	 kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
185 int	 kex_setup(struct ssh *, char *[PROPOSAL_MAX]);
186 void	 kex_free_newkeys(struct newkeys *);
187 void	 kex_free(struct kex *);
188 
189 int	 kex_buf2prop(struct sshbuf *, int *, char ***);
190 int	 kex_prop2buf(struct sshbuf *, char *proposal[PROPOSAL_MAX]);
191 void	 kex_prop_free(char **);
192 int	 kex_load_hostkey(struct ssh *, struct sshkey **, struct sshkey **);
193 int	 kex_verify_host_key(struct ssh *, struct sshkey *);
194 
195 int	 kex_send_kexinit(struct ssh *);
196 int	 kex_input_kexinit(int, u_int32_t, struct ssh *);
197 int	 kex_input_ext_info(int, u_int32_t, struct ssh *);
198 int	 kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
199 int	 kex_send_newkeys(struct ssh *);
200 int	 kex_start_rekex(struct ssh *);
201 
202 int	 kexgex_client(struct ssh *);
203 int	 kexgex_server(struct ssh *);
204 int	 kex_gen_client(struct ssh *);
205 int	 kex_gen_server(struct ssh *);
206 
207 int	 kex_dh_keypair(struct kex *);
208 int	 kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
209     struct sshbuf **);
210 int	 kex_dh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
211 
212 int	 kex_ecdh_keypair(struct kex *);
213 int	 kex_ecdh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
214     struct sshbuf **);
215 int	 kex_ecdh_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
216 
217 int	 kex_c25519_keypair(struct kex *);
218 int	 kex_c25519_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
219     struct sshbuf **);
220 int	 kex_c25519_dec(struct kex *, const struct sshbuf *, struct sshbuf **);
221 
222 int	 kex_kem_sntrup4591761x25519_keypair(struct kex *);
223 int	 kex_kem_sntrup4591761x25519_enc(struct kex *, const struct sshbuf *,
224     struct sshbuf **, struct sshbuf **);
225 int	 kex_kem_sntrup4591761x25519_dec(struct kex *, const struct sshbuf *,
226     struct sshbuf **);
227 
228 int	 kex_dh_keygen(struct kex *);
229 int	 kex_dh_compute_key(struct kex *, BIGNUM *, struct sshbuf *);
230 
231 int	 kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
232     const struct sshbuf *, const struct sshbuf *, const struct sshbuf *,
233     int, int, int,
234     const BIGNUM *, const BIGNUM *, const BIGNUM *,
235     const BIGNUM *, const u_char *, size_t,
236     u_char *, size_t *);
237 
238 void	kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
239 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
240 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
241 int	kexc25519_shared_key(const u_char key[CURVE25519_SIZE],
242     const u_char pub[CURVE25519_SIZE], struct sshbuf *out)
243 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
244 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
245 int	kexc25519_shared_key_ext(const u_char key[CURVE25519_SIZE],
246     const u_char pub[CURVE25519_SIZE], struct sshbuf *out, int)
247 	__attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
248 	__attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));
249 
250 #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
251 void	dump_digest(const char *, const u_char *, int);
252 #endif
253 
254 #if !defined(WITH_OPENSSL) || !defined(OPENSSL_HAS_ECC)
255 # undef EC_KEY
256 # undef EC_GROUP
257 # undef EC_POINT
258 #endif
259 
260 #endif
261