[thirdparty/openssh-portable.git] / kexsntrup761x25519.c

/* $OpenBSD: kexsntrup761x25519.c,v 1.2 2021/12/05 12:28:27 jsg Exp $ */
/*
 * Copyright (c) 2019 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.
 */

#include "includes.h"

#ifdef USE_SNTRUP761X25519

#include <sys/types.h>

#include <stdio.h>
#include <string.h>
#include <signal.h>

#include "sshkey.h"
#include "kex.h"
#include "sshbuf.h"
#include "digest.h"
#include "ssherr.h"

int
kex_kem_sntrup761x25519_keypair(struct kex *kex)
{
	struct sshbuf *buf = NULL;
	u_char *cp = NULL;
	size_t need;
	int r;

	if ((buf = sshbuf_new()) == NULL)
		return SSH_ERR_ALLOC_FAIL;
	need = crypto_kem_sntrup761_PUBLICKEYBYTES + CURVE25519_SIZE;
	if ((r = sshbuf_reserve(buf, need, &cp)) != 0)
		goto out;
	crypto_kem_sntrup761_keypair(cp, kex->sntrup761_client_key);
#ifdef DEBUG_KEXECDH
	dump_digest("client public key sntrup761:", cp,
	    crypto_kem_sntrup761_PUBLICKEYBYTES);
#endif
	cp += crypto_kem_sntrup761_PUBLICKEYBYTES;
	kexc25519_keygen(kex->c25519_client_key, cp);
#ifdef DEBUG_KEXECDH
	dump_digest("client public key c25519:", cp, CURVE25519_SIZE);
#endif
	kex->client_pub = buf;
	buf = NULL;
 out:
	sshbuf_free(buf);
	return r;
}

int
kex_kem_sntrup761x25519_enc(struct kex *kex,
   const struct sshbuf *client_blob, struct sshbuf **server_blobp,
   struct sshbuf **shared_secretp)
{
	struct sshbuf *server_blob = NULL;
	struct sshbuf *buf = NULL;
	const u_char *client_pub;
	u_char *kem_key, *ciphertext, *server_pub;
	u_char server_key[CURVE25519_SIZE];
	u_char hash[SSH_DIGEST_MAX_LENGTH];
	size_t need;
	int r;

	*server_blobp = NULL;
	*shared_secretp = NULL;

	/* client_blob contains both KEM and ECDH client pubkeys */
	need = crypto_kem_sntrup761_PUBLICKEYBYTES + CURVE25519_SIZE;
	if (sshbuf_len(client_blob) != need) {
		r = SSH_ERR_SIGNATURE_INVALID;
		goto out;
	}
	client_pub = sshbuf_ptr(client_blob);
#ifdef DEBUG_KEXECDH
	dump_digest("client public key sntrup761:", client_pub,
	    crypto_kem_sntrup761_PUBLICKEYBYTES);
	dump_digest("client public key 25519:",
	    client_pub + crypto_kem_sntrup761_PUBLICKEYBYTES,
	    CURVE25519_SIZE);
#endif
	/* allocate buffer for concatenation of KEM key and ECDH shared key */
	/* the buffer will be hashed and the result is the shared secret */
	if ((buf = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshbuf_reserve(buf, crypto_kem_sntrup761_BYTES,
	    &kem_key)) != 0)
		goto out;
	/* allocate space for encrypted KEM key and ECDH pub key */
	if ((server_blob = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	need = crypto_kem_sntrup761_CIPHERTEXTBYTES + CURVE25519_SIZE;
	if ((r = sshbuf_reserve(server_blob, need, &ciphertext)) != 0)
		goto out;
	/* generate and encrypt KEM key with client key */
	crypto_kem_sntrup761_enc(ciphertext, kem_key, client_pub);
	/* generate ECDH key pair, store server pubkey after ciphertext */
	server_pub = ciphertext + crypto_kem_sntrup761_CIPHERTEXTBYTES;
	kexc25519_keygen(server_key, server_pub);
	/* append ECDH shared key */
	client_pub += crypto_kem_sntrup761_PUBLICKEYBYTES;
	if ((r = kexc25519_shared_key_ext(server_key, client_pub, buf, 1)) < 0)
		goto out;
	if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
		goto out;
#ifdef DEBUG_KEXECDH
	dump_digest("server public key 25519:", server_pub, CURVE25519_SIZE);
	dump_digest("server cipher text:", ciphertext,
	    crypto_kem_sntrup761_CIPHERTEXTBYTES);
	dump_digest("server kem key:", kem_key, crypto_kem_sntrup761_BYTES);
	dump_digest("concatenation of KEM key and ECDH shared key:",
	    sshbuf_ptr(buf), sshbuf_len(buf));
#endif
	/* string-encoded hash is resulting shared secret */
	sshbuf_reset(buf);
	if ((r = sshbuf_put_string(buf, hash,
	    ssh_digest_bytes(kex->hash_alg))) != 0)
		goto out;
#ifdef DEBUG_KEXECDH
	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
#endif
	*server_blobp = server_blob;
	*shared_secretp = buf;
	server_blob = NULL;
	buf = NULL;
 out:
	explicit_bzero(hash, sizeof(hash));
	explicit_bzero(server_key, sizeof(server_key));
	sshbuf_free(server_blob);
	sshbuf_free(buf);
	return r;
}

int
kex_kem_sntrup761x25519_dec(struct kex *kex,
    const struct sshbuf *server_blob, struct sshbuf **shared_secretp)
{
	struct sshbuf *buf = NULL;
	u_char *kem_key = NULL;
	const u_char *ciphertext, *server_pub;
	u_char hash[SSH_DIGEST_MAX_LENGTH];
	size_t need;
	int r, decoded;

	*shared_secretp = NULL;

	need = crypto_kem_sntrup761_CIPHERTEXTBYTES + CURVE25519_SIZE;
	if (sshbuf_len(server_blob) != need) {
		r = SSH_ERR_SIGNATURE_INVALID;
		goto out;
	}
	ciphertext = sshbuf_ptr(server_blob);
	server_pub = ciphertext + crypto_kem_sntrup761_CIPHERTEXTBYTES;
#ifdef DEBUG_KEXECDH
	dump_digest("server cipher text:", ciphertext,
	    crypto_kem_sntrup761_CIPHERTEXTBYTES);
	dump_digest("server public key c25519:", server_pub, CURVE25519_SIZE);
#endif
	/* hash concatenation of KEM key and ECDH shared key */
	if ((buf = sshbuf_new()) == NULL) {
		r = SSH_ERR_ALLOC_FAIL;
		goto out;
	}
	if ((r = sshbuf_reserve(buf, crypto_kem_sntrup761_BYTES,
	    &kem_key)) != 0)
		goto out;
	decoded = crypto_kem_sntrup761_dec(kem_key, ciphertext,
	    kex->sntrup761_client_key);
	if ((r = kexc25519_shared_key_ext(kex->c25519_client_key, server_pub,
	    buf, 1)) < 0)
		goto out;
	if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
		goto out;
#ifdef DEBUG_KEXECDH
	dump_digest("client kem key:", kem_key, crypto_kem_sntrup761_BYTES);
	dump_digest("concatenation of KEM key and ECDH shared key:",
	    sshbuf_ptr(buf), sshbuf_len(buf));
#endif
	sshbuf_reset(buf);
	if ((r = sshbuf_put_string(buf, hash,
	    ssh_digest_bytes(kex->hash_alg))) != 0)
		goto out;
#ifdef DEBUG_KEXECDH
	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
#endif
	if (decoded != 0) {
		r = SSH_ERR_SIGNATURE_INVALID;
		goto out;
	}
	*shared_secretp = buf;
	buf = NULL;
 out:
	explicit_bzero(hash, sizeof(hash));
	sshbuf_free(buf);
	return r;
}

#else

#include "ssherr.h"

struct kex;
struct sshbuf;
struct sshkey;

int
kex_kem_sntrup761x25519_keypair(struct kex *kex)
{
	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
}

int
kex_kem_sntrup761x25519_enc(struct kex *kex,
   const struct sshbuf *client_blob, struct sshbuf **server_blobp,
   struct sshbuf **shared_secretp)
{
	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
}

int
kex_kem_sntrup761x25519_dec(struct kex *kex,
    const struct sshbuf *server_blob, struct sshbuf **shared_secretp)
{
	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
}
#endif /* USE_SNTRUP761X25519 */
Commit	Line	Data
a2188579	1	/* $OpenBSD: kexsntrup761x25519.c,v 1.2 2021/12/05 12:28:27 jsg Exp $ */
dfd59161	2	/*
	3	* Copyright (c) 2019 Markus Friedl. All rights reserved.
	4	*
	5	* Redistribution and use in source and binary forms, with or without
	6	* modification, are permitted provided that the following conditions
	7	* are met:
	8	* 1. Redistributions of source code must retain the above copyright
	9	* notice, this list of conditions and the following disclaimer.
	10	* 2. Redistributions in binary form must reproduce the above copyright
	11	* notice, this list of conditions and the following disclaimer in the
	12	* documentation and/or other materials provided with the distribution.
	13	*
	14	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	17	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	24	*/
	25
d50ab3cd DM	26	#include "includes.h"
d50ab3cd DM	27
48d0d7a4 DT	28	#ifdef USE_SNTRUP761X25519
48d0d7a4 DT	29
dfd59161	30	#include <sys/types.h>
	31
	32	#include <stdio.h>
	33	#include <string.h>
	34	#include <signal.h>
	35
	36	#include "sshkey.h"
	37	#include "kex.h"
	38	#include "sshbuf.h"
	39	#include "digest.h"
	40	#include "ssherr.h"
	41
	42	int
659864fe	43	kex_kem_sntrup761x25519_keypair(struct kex *kex)
dfd59161	44	{
	45	struct sshbuf *buf = NULL;
	46	u_char *cp = NULL;
	47	size_t need;
	48	int r;
	49
	50	if ((buf = sshbuf_new()) == NULL)
	51	return SSH_ERR_ALLOC_FAIL;
659864fe	52	need = crypto_kem_sntrup761_PUBLICKEYBYTES + CURVE25519_SIZE;
dfd59161	53	if ((r = sshbuf_reserve(buf, need, &cp)) != 0)
dfd59161	54	goto out;
659864fe	55	crypto_kem_sntrup761_keypair(cp, kex->sntrup761_client_key);
dfd59161	56	#ifdef DEBUG_KEXECDH
659864fe	57	dump_digest("client public key sntrup761:", cp,
659864fe	58	crypto_kem_sntrup761_PUBLICKEYBYTES);
dfd59161	59	#endif
659864fe	60	cp += crypto_kem_sntrup761_PUBLICKEYBYTES;
dfd59161	61	kexc25519_keygen(kex->c25519_client_key, cp);
	62	#ifdef DEBUG_KEXECDH
	63	dump_digest("client public key c25519:", cp, CURVE25519_SIZE);
	64	#endif
aaca72d6	65	kex->client_pub = buf;
dfd59161	66	buf = NULL;
	67	out:
	68	sshbuf_free(buf);
	69	return r;
	70	}
	71
	72	int
659864fe	73	kex_kem_sntrup761x25519_enc(struct kex *kex,
71e67fff	74	const struct sshbuf client_blob, struct sshbuf *server_blobp,
71e67fff	75	struct sshbuf **shared_secretp)
dfd59161	76	{
	77	struct sshbuf *server_blob = NULL;
	78	struct sshbuf *buf = NULL;
71e67fff	79	const u_char *client_pub;
dfd59161	80	u_char kem_key, ciphertext, *server_pub;
	81	u_char server_key[CURVE25519_SIZE];
	82	u_char hash[SSH_DIGEST_MAX_LENGTH];
	83	size_t need;
	84	int r;
	85
	86	*server_blobp = NULL;
	87	*shared_secretp = NULL;
	88
71e67fff	89	/* client_blob contains both KEM and ECDH client pubkeys */
659864fe	90	need = crypto_kem_sntrup761_PUBLICKEYBYTES + CURVE25519_SIZE;
71e67fff	91	if (sshbuf_len(client_blob) != need) {
dfd59161	92	r = SSH_ERR_SIGNATURE_INVALID;
	93	goto out;
	94	}
71e67fff	95	client_pub = sshbuf_ptr(client_blob);
dfd59161	96	#ifdef DEBUG_KEXECDH
659864fe	97	dump_digest("client public key sntrup761:", client_pub,
659864fe	98	crypto_kem_sntrup761_PUBLICKEYBYTES);
dfd59161	99	dump_digest("client public key 25519:",
659864fe	100	client_pub + crypto_kem_sntrup761_PUBLICKEYBYTES,
71e67fff	101	CURVE25519_SIZE);
dfd59161	102	#endif
	103	/* allocate buffer for concatenation of KEM key and ECDH shared key */
	104	/* the buffer will be hashed and the result is the shared secret */
	105	if ((buf = sshbuf_new()) == NULL) {
	106	r = SSH_ERR_ALLOC_FAIL;
	107	goto out;
	108	}
659864fe	109	if ((r = sshbuf_reserve(buf, crypto_kem_sntrup761_BYTES,
dfd59161	110	&kem_key)) != 0)
	111	goto out;
	112	/* allocate space for encrypted KEM key and ECDH pub key */
	113	if ((server_blob = sshbuf_new()) == NULL) {
	114	r = SSH_ERR_ALLOC_FAIL;
	115	goto out;
	116	}
659864fe	117	need = crypto_kem_sntrup761_CIPHERTEXTBYTES + CURVE25519_SIZE;
dfd59161	118	if ((r = sshbuf_reserve(server_blob, need, &ciphertext)) != 0)
	119	goto out;
	120	/* generate and encrypt KEM key with client key */
659864fe	121	crypto_kem_sntrup761_enc(ciphertext, kem_key, client_pub);
dfd59161	122	/* generate ECDH key pair, store server pubkey after ciphertext */
659864fe	123	server_pub = ciphertext + crypto_kem_sntrup761_CIPHERTEXTBYTES;
dfd59161	124	kexc25519_keygen(server_key, server_pub);
dfd59161	125	/* append ECDH shared key */
659864fe	126	client_pub += crypto_kem_sntrup761_PUBLICKEYBYTES;
71e67fff	127	if ((r = kexc25519_shared_key_ext(server_key, client_pub, buf, 1)) < 0)
dfd59161	128	goto out;
	129	if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
	130	goto out;
	131	#ifdef DEBUG_KEXECDH
	132	dump_digest("server public key 25519:", server_pub, CURVE25519_SIZE);
	133	dump_digest("server cipher text:", ciphertext,
659864fe	134	crypto_kem_sntrup761_CIPHERTEXTBYTES);
a2188579	135	dump_digest("server kem key:", kem_key, crypto_kem_sntrup761_BYTES);
dfd59161	136	dump_digest("concatenation of KEM key and ECDH shared key:",
	137	sshbuf_ptr(buf), sshbuf_len(buf));
	138	#endif
	139	/* string-encoded hash is resulting shared secret */
	140	sshbuf_reset(buf);
	141	if ((r = sshbuf_put_string(buf, hash,
	142	ssh_digest_bytes(kex->hash_alg))) != 0)
	143	goto out;
	144	#ifdef DEBUG_KEXECDH
	145	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
	146	#endif
	147	*server_blobp = server_blob;
	148	*shared_secretp = buf;
	149	server_blob = NULL;
	150	buf = NULL;
	151	out:
	152	explicit_bzero(hash, sizeof(hash));
	153	explicit_bzero(server_key, sizeof(server_key));
	154	sshbuf_free(server_blob);
	155	sshbuf_free(buf);
	156	return r;
	157	}
	158
	159	int
659864fe	160	kex_kem_sntrup761x25519_dec(struct kex *kex,
71e67fff	161	const struct sshbuf server_blob, struct sshbuf *shared_secretp)
dfd59161	162	{
	163	struct sshbuf *buf = NULL;
	164	u_char *kem_key = NULL;
	165	const u_char ciphertext, server_pub;
	166	u_char hash[SSH_DIGEST_MAX_LENGTH];
	167	size_t need;
	168	int r, decoded;
	169
	170	*shared_secretp = NULL;
	171
659864fe	172	need = crypto_kem_sntrup761_CIPHERTEXTBYTES + CURVE25519_SIZE;
71e67fff	173	if (sshbuf_len(server_blob) != need) {
dfd59161	174	r = SSH_ERR_SIGNATURE_INVALID;
	175	goto out;
	176	}
71e67fff	177	ciphertext = sshbuf_ptr(server_blob);
659864fe	178	server_pub = ciphertext + crypto_kem_sntrup761_CIPHERTEXTBYTES;
dfd59161	179	#ifdef DEBUG_KEXECDH
dfd59161	180	dump_digest("server cipher text:", ciphertext,
659864fe	181	crypto_kem_sntrup761_CIPHERTEXTBYTES);
dfd59161	182	dump_digest("server public key c25519:", server_pub, CURVE25519_SIZE);
	183	#endif
	184	/* hash concatenation of KEM key and ECDH shared key */
	185	if ((buf = sshbuf_new()) == NULL) {
	186	r = SSH_ERR_ALLOC_FAIL;
	187	goto out;
	188	}
659864fe	189	if ((r = sshbuf_reserve(buf, crypto_kem_sntrup761_BYTES,
dfd59161	190	&kem_key)) != 0)
dfd59161	191	goto out;
659864fe	192	decoded = crypto_kem_sntrup761_dec(kem_key, ciphertext,
659864fe	193	kex->sntrup761_client_key);
dfd59161	194	if ((r = kexc25519_shared_key_ext(kex->c25519_client_key, server_pub,
	195	buf, 1)) < 0)
	196	goto out;
	197	if ((r = ssh_digest_buffer(kex->hash_alg, buf, hash, sizeof(hash))) != 0)
	198	goto out;
	199	#ifdef DEBUG_KEXECDH
659864fe	200	dump_digest("client kem key:", kem_key, crypto_kem_sntrup761_BYTES);
dfd59161	201	dump_digest("concatenation of KEM key and ECDH shared key:",
	202	sshbuf_ptr(buf), sshbuf_len(buf));
	203	#endif
	204	sshbuf_reset(buf);
	205	if ((r = sshbuf_put_string(buf, hash,
	206	ssh_digest_bytes(kex->hash_alg))) != 0)
	207	goto out;
	208	#ifdef DEBUG_KEXECDH
	209	dump_digest("encoded shared secret:", sshbuf_ptr(buf), sshbuf_len(buf));
	210	#endif
	211	if (decoded != 0) {
	212	r = SSH_ERR_SIGNATURE_INVALID;
	213	goto out;
	214	}
	215	*shared_secretp = buf;
	216	buf = NULL;
	217	out:
	218	explicit_bzero(hash, sizeof(hash));
	219	sshbuf_free(buf);
	220	return r;
	221	}
48d0d7a4 DT	222
	223	#else
	224
	225	#include "ssherr.h"
	226
	227	struct kex;
	228	struct sshbuf;
	229	struct sshkey;
	230
	231	int
	232	kex_kem_sntrup761x25519_keypair(struct kex *kex)
	233	{
	234	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
	235	}
	236
	237	int
	238	kex_kem_sntrup761x25519_enc(struct kex *kex,
	239	const struct sshbuf client_blob, struct sshbuf *server_blobp,
	240	struct sshbuf **shared_secretp)
	241	{
	242	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
	243	}
	244
	245	int
	246	kex_kem_sntrup761x25519_dec(struct kex *kex,
	247	const struct sshbuf server_blob, struct sshbuf *shared_secretp)
	248	{
	249	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
	250	}
	251	#endif /* USE_SNTRUP761X25519 */