[openssh.git] / jpake.c

/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */
/*
 * Copyright (c) 2008 Damien Miller.  All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Shared components of zero-knowledge password auth using J-PAKE protocol
 * as described in:
 *
 * F. Hao, P. Ryan, "Password Authenticated Key Exchange by Juggling",
 * 16th Workshop on Security Protocols, Cambridge, April 2008
 *
 * http://grouper.ieee.org/groups/1363/Research/contributions/hao-ryan-2008.pdf
 */

#include "includes.h"

#include <sys/types.h>

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

#include <openssl/bn.h>
#include <openssl/evp.h>

#include "xmalloc.h"
#include "ssh2.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "buffer.h"
#include "packet.h"
#include "dispatch.h"
#include "log.h"

#include "jpake.h"
#include "schnorr.h"

#ifdef JPAKE

/* RFC3526 group 5, 1536 bits */
#define JPAKE_GROUP_G "2"
#define JPAKE_GROUP_P \
	"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74" \
	"020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F1437" \
	"4FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
	"EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF05" \
	"98DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB" \
	"9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF"

struct modp_group *
jpake_default_group(void)
{
	return modp_group_from_g_and_safe_p(JPAKE_GROUP_G, JPAKE_GROUP_P);
}

struct jpake_ctx *
jpake_new(void)
{
	struct jpake_ctx *ret;

	ret = xcalloc(1, sizeof(*ret));

	ret->grp = jpake_default_group();

	ret->s = ret->k = NULL;
	ret->x1 = ret->x2 = ret->x3 = ret->x4 = NULL;
	ret->g_x1 = ret->g_x2 = ret->g_x3 = ret->g_x4 = NULL;
	ret->a = ret->b = NULL;

	ret->client_id = ret->server_id = NULL;
	ret->h_k_cid_sessid = ret->h_k_sid_sessid = NULL;

	debug3("%s: alloc %p", __func__, ret);

	return ret;
}

void
jpake_free(struct jpake_ctx *pctx)
{
	debug3("%s: free %p", __func__, pctx);

#define JPAKE_BN_CLEAR_FREE(v)			\
	do {					\
		if ((v) != NULL) {		\
			BN_clear_free(v);	\
			(v) = NULL;		\
		}				\
	} while (0)
#define JPAKE_BUF_CLEAR_FREE(v, l)		\
	do {					\
		if ((v) != NULL) {		\
			bzero((v), (l));	\
			xfree(v);		\
			(v) = NULL;		\
			(l) = 0;		\
		}				\
	} while (0)

	JPAKE_BN_CLEAR_FREE(pctx->s);
	JPAKE_BN_CLEAR_FREE(pctx->k);
	JPAKE_BN_CLEAR_FREE(pctx->x1);
	JPAKE_BN_CLEAR_FREE(pctx->x2);
	JPAKE_BN_CLEAR_FREE(pctx->x3);
	JPAKE_BN_CLEAR_FREE(pctx->x4);
	JPAKE_BN_CLEAR_FREE(pctx->g_x1);
	JPAKE_BN_CLEAR_FREE(pctx->g_x2);
	JPAKE_BN_CLEAR_FREE(pctx->g_x3);
	JPAKE_BN_CLEAR_FREE(pctx->g_x4);
	JPAKE_BN_CLEAR_FREE(pctx->a);
	JPAKE_BN_CLEAR_FREE(pctx->b);

	JPAKE_BUF_CLEAR_FREE(pctx->client_id, pctx->client_id_len);
	JPAKE_BUF_CLEAR_FREE(pctx->server_id, pctx->server_id_len);
	JPAKE_BUF_CLEAR_FREE(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
	JPAKE_BUF_CLEAR_FREE(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);

#undef JPAKE_BN_CLEAR_FREE
#undef JPAKE_BUF_CLEAR_FREE

	bzero(pctx, sizeof(pctx));
	xfree(pctx);
}

/* dump entire jpake_ctx. NB. includes private values! */
void
jpake_dump(struct jpake_ctx *pctx, const char *fmt, ...)
{
	char *out;
	va_list args;

	out = NULL;
	va_start(args, fmt);
	vasprintf(&out, fmt, args);
	va_end(args);
	if (out == NULL)
		fatal("%s: vasprintf failed", __func__);

	debug3("%s: %s (ctx at %p)", __func__, out, pctx);
	if (pctx == NULL) {
		free(out);
		return;
	}

#define JPAKE_DUMP_BN(a)	do { \
		if ((a) != NULL) \
			JPAKE_DEBUG_BN(((a), "%s = ", #a)); \
	} while (0)
#define JPAKE_DUMP_BUF(a, b)	do { \
		if ((a) != NULL) \
			JPAKE_DEBUG_BUF((a, b, "%s", #a)); \
	} while (0)

	JPAKE_DUMP_BN(pctx->s);
	JPAKE_DUMP_BN(pctx->k);
	JPAKE_DUMP_BN(pctx->x1);
	JPAKE_DUMP_BN(pctx->x2);
	JPAKE_DUMP_BN(pctx->x3);
	JPAKE_DUMP_BN(pctx->x4);
	JPAKE_DUMP_BN(pctx->g_x1);
	JPAKE_DUMP_BN(pctx->g_x2);
	JPAKE_DUMP_BN(pctx->g_x3);
	JPAKE_DUMP_BN(pctx->g_x4);
	JPAKE_DUMP_BN(pctx->a);
	JPAKE_DUMP_BN(pctx->b);

	JPAKE_DUMP_BUF(pctx->client_id, pctx->client_id_len);
	JPAKE_DUMP_BUF(pctx->server_id, pctx->server_id_len);
	JPAKE_DUMP_BUF(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
	JPAKE_DUMP_BUF(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);

	debug3("%s: %s done", __func__, out);
	free(out);
}

/* Shared parts of step 1 exchange calculation */
void
jpake_step1(struct modp_group *grp,
    u_char **id, u_int *id_len,
    BIGNUM **priv1, BIGNUM **priv2, BIGNUM **g_priv1, BIGNUM **g_priv2,
    u_char **priv1_proof, u_int *priv1_proof_len,
    u_char **priv2_proof, u_int *priv2_proof_len)
{
	BN_CTX *bn_ctx;

	if ((bn_ctx = BN_CTX_new()) == NULL)
		fatal("%s: BN_CTX_new", __func__);

	/* Random nonce to prevent replay */
	*id = xmalloc(KZP_ID_LEN);
	*id_len = KZP_ID_LEN;
	arc4random_buf(*id, *id_len);

	/*
	 * x1/x3 is a random element of Zq
	 * x2/x4 is a random element of Z*q
	 * We also exclude [1] from x1/x3 candidates and [0, 1] from
	 * x2/x4 candiates to avoid possible degeneracy (i.e. g^0, g^1).
	 */
	if ((*priv1 = bn_rand_range_gt_one(grp->q)) == NULL ||
	    (*priv2 = bn_rand_range_gt_one(grp->q)) == NULL)
		fatal("%s: bn_rand_range_gt_one", __func__);

	/*
	 * client: g_x1 = g^x1 mod p / server: g_x3 = g^x3 mod p
	 * client: g_x2 = g^x2 mod p / server: g_x4 = g^x4 mod p
	 */
	if ((*g_priv1 = BN_new()) == NULL ||
	    (*g_priv2 = BN_new()) == NULL)
		fatal("%s: BN_new", __func__);
	if (BN_mod_exp(*g_priv1, grp->g, *priv1, grp->p, bn_ctx) == -1)
		fatal("%s: BN_mod_exp", __func__);
	if (BN_mod_exp(*g_priv2, grp->g, *priv2, grp->p, bn_ctx) == -1)
		fatal("%s: BN_mod_exp", __func__);

	/* Generate proofs for holding x1/x3 and x2/x4 */
	if (schnorr_sign_buf(grp->p, grp->q, grp->g,
	    *priv1, *g_priv1, *id, *id_len,
	    priv1_proof, priv1_proof_len) != 0)
		fatal("%s: schnorr_sign", __func__);
	if (schnorr_sign_buf(grp->p, grp->q, grp->g,
	    *priv2, *g_priv2, *id, *id_len,
	    priv2_proof, priv2_proof_len) != 0)
		fatal("%s: schnorr_sign", __func__);

	BN_CTX_free(bn_ctx);
}

/* Shared parts of step 2 exchange calculation */
void
jpake_step2(struct modp_group *grp, BIGNUM *s,
    BIGNUM *mypub1, BIGNUM *theirpub1, BIGNUM *theirpub2, BIGNUM *mypriv2,
    const u_char *theirid, u_int theirid_len,
    const u_char *myid, u_int myid_len,
    const u_char *theirpub1_proof, u_int theirpub1_proof_len,
    const u_char *theirpub2_proof, u_int theirpub2_proof_len,
    BIGNUM **newpub,
    u_char **newpub_exponent_proof, u_int *newpub_exponent_proof_len)
{
	BN_CTX *bn_ctx;
	BIGNUM *tmp, *exponent;

	/* Validate peer's step 1 values */
	if (BN_cmp(theirpub1, BN_value_one()) <= 0)
		fatal("%s: theirpub1 <= 1", __func__);
	if (BN_cmp(theirpub2, BN_value_one()) <= 0)
		fatal("%s: theirpub2 <= 1", __func__);

	if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub1,
	    theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1)
		fatal("%s: schnorr_verify theirpub1 failed", __func__);
	if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub2,
	    theirid, theirid_len, theirpub2_proof, theirpub2_proof_len) != 1)
		fatal("%s: schnorr_verify theirpub2 failed", __func__);

	if ((bn_ctx = BN_CTX_new()) == NULL)
		fatal("%s: BN_CTX_new", __func__);

	if ((*newpub = BN_new()) == NULL ||
	    (tmp = BN_new()) == NULL ||
	    (exponent = BN_new()) == NULL)
		fatal("%s: BN_new", __func__);

	/*
	 * client: exponent = x2 * s mod p
	 * server: exponent = x4 * s mod p
	 */
	if (BN_mod_mul(exponent, mypriv2, s, grp->q, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (exponent = mypriv2 * s mod p)",
		    __func__);

	/*
	 * client: tmp = g^(x1 + x3 + x4) mod p
	 * server: tmp = g^(x1 + x2 + x3) mod p
	 */
	if (BN_mod_mul(tmp, mypub1, theirpub1, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (tmp = mypub1 * theirpub1 mod p)",
		    __func__);
	if (BN_mod_mul(tmp, tmp, theirpub2, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (tmp = tmp * theirpub2 mod p)", __func__);

	/*
	 * client: a = tmp^exponent = g^((x1+x3+x4) * x2 * s) mod p
	 * server: b = tmp^exponent = g^((x1+x2+x3) * x4 * s) mod p
	 */
	if (BN_mod_exp(*newpub, tmp, exponent, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (newpub = tmp^exponent mod p)", __func__);

	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
	JPAKE_DEBUG_BN((exponent, "%s: exponent = ", __func__));

	/* Note the generator here is 'tmp', not g */
	if (schnorr_sign_buf(grp->p, grp->q, tmp, exponent, *newpub,
	    myid, myid_len,
	    newpub_exponent_proof, newpub_exponent_proof_len) != 0)
		fatal("%s: schnorr_sign newpub", __func__);

	BN_clear_free(tmp); /* XXX stash for later use? */
	BN_clear_free(exponent); /* XXX stash for later use? (yes, in conf) */

	BN_CTX_free(bn_ctx);
}

/* Confirmation hash calculation */
void
jpake_confirm_hash(const BIGNUM *k,
    const u_char *endpoint_id, u_int endpoint_id_len,
    const u_char *sess_id, u_int sess_id_len,
    u_char **confirm_hash, u_int *confirm_hash_len)
{
	Buffer b;

	/*
	 * Calculate confirmation proof:
	 *     client: H(k || client_id || session_id)
	 *     server: H(k || server_id || session_id)
	 */
	buffer_init(&b);
	buffer_put_bignum2(&b, k);
	buffer_put_string(&b, endpoint_id, endpoint_id_len);
	buffer_put_string(&b, sess_id, sess_id_len);
	if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
	    confirm_hash, confirm_hash_len) != 0)
		fatal("%s: hash_buffer", __func__);
	buffer_free(&b);
}

/* Shared parts of key derivation and confirmation calculation */
void
jpake_key_confirm(struct modp_group *grp, BIGNUM *s, BIGNUM *step2_val,
    BIGNUM *mypriv2, BIGNUM *mypub1, BIGNUM *mypub2,
    BIGNUM *theirpub1, BIGNUM *theirpub2,
    const u_char *my_id, u_int my_id_len,
    const u_char *their_id, u_int their_id_len,
    const u_char *sess_id, u_int sess_id_len,
    const u_char *theirpriv2_s_proof, u_int theirpriv2_s_proof_len,
    BIGNUM **k,
    u_char **confirm_hash, u_int *confirm_hash_len)
{
	BN_CTX *bn_ctx;
	BIGNUM *tmp;

	if ((bn_ctx = BN_CTX_new()) == NULL)
		fatal("%s: BN_CTX_new", __func__);
	if ((tmp = BN_new()) == NULL ||
	    (*k = BN_new()) == NULL)
		fatal("%s: BN_new", __func__);

	/* Validate step 2 values */
	if (BN_cmp(step2_val, BN_value_one()) <= 0)
		fatal("%s: step2_val <= 1", __func__);

	/*
	 * theirpriv2_s_proof is calculated with a different generator:
	 * tmp = g^(mypriv1+mypriv2+theirpub1) = g^mypub1*g^mypub2*g^theirpub1
	 * Calculate it here so we can check the signature.
	 */
	if (BN_mod_mul(tmp, mypub1, mypub2, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (tmp = mypub1 * mypub2 mod p)", __func__);
	if (BN_mod_mul(tmp, tmp, theirpub1, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (tmp = tmp * theirpub1 mod p)", __func__);

	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));

	if (schnorr_verify_buf(grp->p, grp->q, tmp, step2_val, 
	    their_id, their_id_len,
	    theirpriv2_s_proof, theirpriv2_s_proof_len) != 1)
		fatal("%s: schnorr_verify theirpriv2_s_proof failed", __func__);

	/*
	 * Derive shared key:
	 *     client: k = (b / g^(x2*x4*s))^x2 = g^((x1+x3)*x2*x4*s)
	 *     server: k = (a / g^(x2*x4*s))^x4 = g^((x1+x3)*x2*x4*s)
	 *
	 * Computed as:
	 *     client: k = (g_x4^(q - (x2 * s)) * b)^x2 mod p
	 *     server: k = (g_x2^(q - (x4 * s)) * b)^x4 mod p
	 */
	if (BN_mul(tmp, mypriv2, s, bn_ctx) != 1)
		fatal("%s: BN_mul (tmp = mypriv2 * s)", __func__);
	if (BN_mod_sub(tmp, grp->q, tmp, grp->q, bn_ctx) != 1)
		fatal("%s: BN_mod_sub (tmp = q - tmp mod q)", __func__);
	if (BN_mod_exp(tmp, theirpub2, tmp, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_exp (tmp = theirpub2^tmp) mod p", __func__);
	if (BN_mod_mul(tmp, tmp, step2_val, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_mul (tmp = tmp * step2_val) mod p", __func__);
	if (BN_mod_exp(*k, tmp, mypriv2, grp->p, bn_ctx) != 1)
		fatal("%s: BN_mod_exp (k = tmp^mypriv2) mod p", __func__);
	
	BN_CTX_free(bn_ctx);
	BN_clear_free(tmp);

	jpake_confirm_hash(*k, my_id, my_id_len, sess_id, sess_id_len,
	    confirm_hash, confirm_hash_len);
}

/*
 * Calculate and check confirmation hash from peer. Returns 1 on success
 * 0 on failure/mismatch.
 */
int
jpake_check_confirm(const BIGNUM *k,
    const u_char *peer_id, u_int peer_id_len,
    const u_char *sess_id, u_int sess_id_len,
    const u_char *peer_confirm_hash, u_int peer_confirm_hash_len)
{
	u_char *expected_confirm_hash;
	u_int expected_confirm_hash_len;
	int success = 0;

	/* Calculate and verify expected confirmation hash */
	jpake_confirm_hash(k, peer_id, peer_id_len, sess_id, sess_id_len,
	    &expected_confirm_hash, &expected_confirm_hash_len);

	JPAKE_DEBUG_BUF((expected_confirm_hash, expected_confirm_hash_len,
	    "%s: expected confirm hash", __func__));
	JPAKE_DEBUG_BUF((peer_confirm_hash, peer_confirm_hash_len,
	    "%s: received confirm hash", __func__));

	if (peer_confirm_hash_len != expected_confirm_hash_len)
		error("%s: confirmation length mismatch (my %u them %u)",
		    __func__, expected_confirm_hash_len, peer_confirm_hash_len);
	else if (memcmp(peer_confirm_hash, expected_confirm_hash,
	    expected_confirm_hash_len) == 0)
		success = 1;
	bzero(expected_confirm_hash, expected_confirm_hash_len);
	xfree(expected_confirm_hash);
	debug3("%s: success = %d", __func__, success);
	return success;
}

/* XXX main() function with tests */

#endif /* JPAKE */
Commit	Line	Data
5b01421b	1	/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */
5adf6b9a	2	/*
	3	* Copyright (c) 2008 Damien Miller. All rights reserved.
	4	*
	5	* Permission to use, copy, modify, and distribute this software for any
	6	* purpose with or without fee is hereby granted, provided that the above
	7	* copyright notice and this permission notice appear in all copies.
	8	*
	9	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	15	* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	16	*/
	17
	18	/*
	19	* Shared components of zero-knowledge password auth using J-PAKE protocol
	20	* as described in:
	21	*
	22	* F. Hao, P. Ryan, "Password Authenticated Key Exchange by Juggling",
	23	* 16th Workshop on Security Protocols, Cambridge, April 2008
	24	*
	25	* http://grouper.ieee.org/groups/1363/Research/contributions/hao-ryan-2008.pdf
	26	*/
	27
	28	#include "includes.h"
	29
	30	#include <sys/types.h>
	31
	32	#include <stdio.h>
	33	#include <string.h>
	34	#include <stdarg.h>
	35
	36	#include <openssl/bn.h>
	37	#include <openssl/evp.h>
	38
	39	#include "xmalloc.h"
	40	#include "ssh2.h"
	41	#include "key.h"
	42	#include "hostfile.h"
	43	#include "auth.h"
	44	#include "buffer.h"
	45	#include "packet.h"
	46	#include "dispatch.h"
	47	#include "log.h"
	48
	49	#include "jpake.h"
5b01421b	50	#include "schnorr.h"
5adf6b9a	51
	52	#ifdef JPAKE
	53
	54	/* RFC3526 group 5, 1536 bits */
	55	#define JPAKE_GROUP_G "2"
	56	#define JPAKE_GROUP_P \
	57	"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74" \
	58	"020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F1437" \
	59	"4FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
	60	"EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF05" \
	61	"98DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB" \
	62	"9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF"
	63
5b01421b	64	struct modp_group *
5adf6b9a	65	jpake_default_group(void)
5adf6b9a	66	{
5b01421b	67	return modp_group_from_g_and_safe_p(JPAKE_GROUP_G, JPAKE_GROUP_P);
5adf6b9a	68	}
	69
	70	struct jpake_ctx *
	71	jpake_new(void)
	72	{
	73	struct jpake_ctx *ret;
	74
	75	ret = xcalloc(1, sizeof(*ret));
	76
	77	ret->grp = jpake_default_group();
	78
	79	ret->s = ret->k = NULL;
	80	ret->x1 = ret->x2 = ret->x3 = ret->x4 = NULL;
	81	ret->g_x1 = ret->g_x2 = ret->g_x3 = ret->g_x4 = NULL;
	82	ret->a = ret->b = NULL;
	83
	84	ret->client_id = ret->server_id = NULL;
	85	ret->h_k_cid_sessid = ret->h_k_sid_sessid = NULL;
	86
	87	debug3("%s: alloc %p", __func__, ret);
	88
	89	return ret;
	90	}
	91
5adf6b9a	92	void
	93	jpake_free(struct jpake_ctx *pctx)
	94	{
	95	debug3("%s: free %p", __func__, pctx);
	96
	97	#define JPAKE_BN_CLEAR_FREE(v) \
	98	do { \
	99	if ((v) != NULL) { \
	100	BN_clear_free(v); \
	101	(v) = NULL; \
	102	} \
	103	} while (0)
	104	#define JPAKE_BUF_CLEAR_FREE(v, l) \
	105	do { \
	106	if ((v) != NULL) { \
	107	bzero((v), (l)); \
	108	xfree(v); \
	109	(v) = NULL; \
	110	(l) = 0; \
	111	} \
	112	} while (0)
	113
	114	JPAKE_BN_CLEAR_FREE(pctx->s);
	115	JPAKE_BN_CLEAR_FREE(pctx->k);
	116	JPAKE_BN_CLEAR_FREE(pctx->x1);
	117	JPAKE_BN_CLEAR_FREE(pctx->x2);
	118	JPAKE_BN_CLEAR_FREE(pctx->x3);
	119	JPAKE_BN_CLEAR_FREE(pctx->x4);
	120	JPAKE_BN_CLEAR_FREE(pctx->g_x1);
	121	JPAKE_BN_CLEAR_FREE(pctx->g_x2);
	122	JPAKE_BN_CLEAR_FREE(pctx->g_x3);
	123	JPAKE_BN_CLEAR_FREE(pctx->g_x4);
	124	JPAKE_BN_CLEAR_FREE(pctx->a);
	125	JPAKE_BN_CLEAR_FREE(pctx->b);
	126
	127	JPAKE_BUF_CLEAR_FREE(pctx->client_id, pctx->client_id_len);
	128	JPAKE_BUF_CLEAR_FREE(pctx->server_id, pctx->server_id_len);
	129	JPAKE_BUF_CLEAR_FREE(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
	130	JPAKE_BUF_CLEAR_FREE(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
	131
	132	#undef JPAKE_BN_CLEAR_FREE
	133	#undef JPAKE_BUF_CLEAR_FREE
	134
	135	bzero(pctx, sizeof(pctx));
	136	xfree(pctx);
	137	}
	138
	139	/* dump entire jpake_ctx. NB. includes private values! */
	140	void
	141	jpake_dump(struct jpake_ctx pctx, const char fmt, ...)
	142	{
	143	char *out;
	144	va_list args;
	145
	146	out = NULL;
	147	va_start(args, fmt);
	148	vasprintf(&out, fmt, args);
	149	va_end(args);
	150	if (out == NULL)
	151	fatal("%s: vasprintf failed", __func__);
	152
	153	debug3("%s: %s (ctx at %p)", __func__, out, pctx);
	154	if (pctx == NULL) {
	155	free(out);
156	return;
157	}
158
159	#define JPAKE_DUMP_BN(a) do { \
160	if ((a) != NULL) \
161	JPAKE_DEBUG_BN(((a), "%s = ", #a)); \
162	} while (0)
163	#define JPAKE_DUMP_BUF(a, b) do { \
164	if ((a) != NULL) \
165	JPAKE_DEBUG_BUF((a, b, "%s", #a)); \
166	} while (0)
167
168	JPAKE_DUMP_BN(pctx->s);
169	JPAKE_DUMP_BN(pctx->k);
170	JPAKE_DUMP_BN(pctx->x1);
171	JPAKE_DUMP_BN(pctx->x2);
172	JPAKE_DUMP_BN(pctx->x3);
173	JPAKE_DUMP_BN(pctx->x4);
174	JPAKE_DUMP_BN(pctx->g_x1);
175	JPAKE_DUMP_BN(pctx->g_x2);
176	JPAKE_DUMP_BN(pctx->g_x3);
177	JPAKE_DUMP_BN(pctx->g_x4);
178	JPAKE_DUMP_BN(pctx->a);
179	JPAKE_DUMP_BN(pctx->b);
180
181	JPAKE_DUMP_BUF(pctx->client_id, pctx->client_id_len);
182	JPAKE_DUMP_BUF(pctx->server_id, pctx->server_id_len);
183	JPAKE_DUMP_BUF(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
184	JPAKE_DUMP_BUF(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
185
186	debug3("%s: %s done", __func__, out);
187	free(out);
188	}
189
190	/* Shared parts of step 1 exchange calculation */
191	void
5b01421b	192	jpake_step1(struct modp_group *grp,
5adf6b9a	193	u_char *id, u_int id_len,
	194	BIGNUM priv1, BIGNUM priv2, BIGNUM g_priv1, BIGNUM g_priv2,
	195	u_char *priv1_proof, u_int priv1_proof_len,
	196	u_char *priv2_proof, u_int priv2_proof_len)
	197	{
	198	BN_CTX *bn_ctx;
	199
	200	if ((bn_ctx = BN_CTX_new()) == NULL)
	201	fatal("%s: BN_CTX_new", __func__);
	202
	203	/* Random nonce to prevent replay */
	204	*id = xmalloc(KZP_ID_LEN);
	205	*id_len = KZP_ID_LEN;
	206	arc4random_buf(id, id_len);
	207
	208	/*
	209	* x1/x3 is a random element of Zq
	210	* x2/x4 is a random element of Z*q
	211	* We also exclude [1] from x1/x3 candidates and [0, 1] from
	212	* x2/x4 candiates to avoid possible degeneracy (i.e. g^0, g^1).
	213	*/
	214	if ((*priv1 = bn_rand_range_gt_one(grp->q)) == NULL \|\|
	215	(*priv2 = bn_rand_range_gt_one(grp->q)) == NULL)
	216	fatal("%s: bn_rand_range_gt_one", __func__);
	217
	218	/*
	219	* client: g_x1 = g^x1 mod p / server: g_x3 = g^x3 mod p
	220	* client: g_x2 = g^x2 mod p / server: g_x4 = g^x4 mod p
	221	*/
	222	if ((*g_priv1 = BN_new()) == NULL \|\|
	223	(*g_priv2 = BN_new()) == NULL)
	224	fatal("%s: BN_new", __func__);
	225	if (BN_mod_exp(g_priv1, grp->g, priv1, grp->p, bn_ctx) == -1)
	226	fatal("%s: BN_mod_exp", __func__);
	227	if (BN_mod_exp(g_priv2, grp->g, priv2, grp->p, bn_ctx) == -1)
	228	fatal("%s: BN_mod_exp", __func__);
	229
	230	/* Generate proofs for holding x1/x3 and x2/x4 */
5b01421b	231	if (schnorr_sign_buf(grp->p, grp->q, grp->g,
5adf6b9a	232	priv1, g_priv1, id, id_len,
	233	priv1_proof, priv1_proof_len) != 0)
	234	fatal("%s: schnorr_sign", __func__);
5b01421b	235	if (schnorr_sign_buf(grp->p, grp->q, grp->g,
5adf6b9a	236	priv2, g_priv2, id, id_len,
	237	priv2_proof, priv2_proof_len) != 0)
	238	fatal("%s: schnorr_sign", __func__);
	239
	240	BN_CTX_free(bn_ctx);
	241	}
	242
	243	/* Shared parts of step 2 exchange calculation */
	244	void
5b01421b	245	jpake_step2(struct modp_group grp, BIGNUM s,
5adf6b9a	246	BIGNUM mypub1, BIGNUM theirpub1, BIGNUM theirpub2, BIGNUM mypriv2,
	247	const u_char *theirid, u_int theirid_len,
	248	const u_char *myid, u_int myid_len,
	249	const u_char *theirpub1_proof, u_int theirpub1_proof_len,
	250	const u_char *theirpub2_proof, u_int theirpub2_proof_len,
	251	BIGNUM **newpub,
	252	u_char *newpub_exponent_proof, u_int newpub_exponent_proof_len)
	253	{
	254	BN_CTX *bn_ctx;
	255	BIGNUM tmp, exponent;
	256
	257	/* Validate peer's step 1 values */
	258	if (BN_cmp(theirpub1, BN_value_one()) <= 0)
	259	fatal("%s: theirpub1 <= 1", __func__);
	260	if (BN_cmp(theirpub2, BN_value_one()) <= 0)
	261	fatal("%s: theirpub2 <= 1", __func__);
	262
5b01421b	263	if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub1,
5adf6b9a	264	theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1)
5adf6b9a	265	fatal("%s: schnorr_verify theirpub1 failed", __func__);
5b01421b	266	if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub2,
5adf6b9a	267	theirid, theirid_len, theirpub2_proof, theirpub2_proof_len) != 1)
	268	fatal("%s: schnorr_verify theirpub2 failed", __func__);
	269
	270	if ((bn_ctx = BN_CTX_new()) == NULL)
	271	fatal("%s: BN_CTX_new", __func__);
	272
	273	if ((*newpub = BN_new()) == NULL \|\|
	274	(tmp = BN_new()) == NULL \|\|
	275	(exponent = BN_new()) == NULL)
	276	fatal("%s: BN_new", __func__);
	277
	278	/*
	279	* client: exponent = x2 * s mod p
	280	* server: exponent = x4 * s mod p
	281	*/
	282	if (BN_mod_mul(exponent, mypriv2, s, grp->q, bn_ctx) != 1)
	283	fatal("%s: BN_mod_mul (exponent = mypriv2 * s mod p)",
	284	__func__);
	285
	286	/*
	287	* client: tmp = g^(x1 + x3 + x4) mod p
	288	* server: tmp = g^(x1 + x2 + x3) mod p
	289	*/
	290	if (BN_mod_mul(tmp, mypub1, theirpub1, grp->p, bn_ctx) != 1)
	291	fatal("%s: BN_mod_mul (tmp = mypub1 * theirpub1 mod p)",
	292	__func__);
	293	if (BN_mod_mul(tmp, tmp, theirpub2, grp->p, bn_ctx) != 1)
	294	fatal("%s: BN_mod_mul (tmp = tmp * theirpub2 mod p)", __func__);
	295
	296	/*
	297	* client: a = tmp^exponent = g^((x1+x3+x4) * x2 * s) mod p
	298	* server: b = tmp^exponent = g^((x1+x2+x3) * x4 * s) mod p
	299	*/
	300	if (BN_mod_exp(*newpub, tmp, exponent, grp->p, bn_ctx) != 1)
	301	fatal("%s: BN_mod_mul (newpub = tmp^exponent mod p)", __func__);
	302
	303	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
	304	JPAKE_DEBUG_BN((exponent, "%s: exponent = ", __func__));
	305
	306	/* Note the generator here is 'tmp', not g */
5b01421b	307	if (schnorr_sign_buf(grp->p, grp->q, tmp, exponent, *newpub,
5adf6b9a	308	myid, myid_len,
	309	newpub_exponent_proof, newpub_exponent_proof_len) != 0)
	310	fatal("%s: schnorr_sign newpub", __func__);
	311
	312	BN_clear_free(tmp); /* XXX stash for later use? */
	313	BN_clear_free(exponent); /* XXX stash for later use? (yes, in conf) */
	314
	315	BN_CTX_free(bn_ctx);
	316	}
	317
	318	/* Confirmation hash calculation */
	319	void
	320	jpake_confirm_hash(const BIGNUM *k,
	321	const u_char *endpoint_id, u_int endpoint_id_len,
	322	const u_char *sess_id, u_int sess_id_len,
	323	u_char *confirm_hash, u_int confirm_hash_len)
	324	{
	325	Buffer b;
	326
	327	/*
	328	* Calculate confirmation proof:
	329	* client: H(k \|\| client_id \|\| session_id)
	330	* server: H(k \|\| server_id \|\| session_id)
	331	*/
	332	buffer_init(&b);
	333	buffer_put_bignum2(&b, k);
	334	buffer_put_string(&b, endpoint_id, endpoint_id_len);
	335	buffer_put_string(&b, sess_id, sess_id_len);
	336	if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
	337	confirm_hash, confirm_hash_len) != 0)
	338	fatal("%s: hash_buffer", __func__);
	339	buffer_free(&b);
	340	}
	341
	342	/* Shared parts of key derivation and confirmation calculation */
	343	void
5b01421b	344	jpake_key_confirm(struct modp_group grp, BIGNUM s, BIGNUM *step2_val,
5adf6b9a	345	BIGNUM mypriv2, BIGNUM mypub1, BIGNUM *mypub2,
	346	BIGNUM theirpub1, BIGNUM theirpub2,
	347	const u_char *my_id, u_int my_id_len,
	348	const u_char *their_id, u_int their_id_len,
	349	const u_char *sess_id, u_int sess_id_len,
	350	const u_char *theirpriv2_s_proof, u_int theirpriv2_s_proof_len,
	351	BIGNUM **k,
	352	u_char *confirm_hash, u_int confirm_hash_len)
	353	{
	354	BN_CTX *bn_ctx;
	355	BIGNUM *tmp;
	356
	357	if ((bn_ctx = BN_CTX_new()) == NULL)
	358	fatal("%s: BN_CTX_new", __func__);
	359	if ((tmp = BN_new()) == NULL \|\|
	360	(*k = BN_new()) == NULL)
	361	fatal("%s: BN_new", __func__);
	362
	363	/* Validate step 2 values */
	364	if (BN_cmp(step2_val, BN_value_one()) <= 0)
	365	fatal("%s: step2_val <= 1", __func__);
	366
	367	/*
	368	* theirpriv2_s_proof is calculated with a different generator:
	369	* tmp = g^(mypriv1+mypriv2+theirpub1) = g^mypub1g^mypub2g^theirpub1
	370	* Calculate it here so we can check the signature.
	371	*/
	372	if (BN_mod_mul(tmp, mypub1, mypub2, grp->p, bn_ctx) != 1)
	373	fatal("%s: BN_mod_mul (tmp = mypub1 * mypub2 mod p)", __func__);
	374	if (BN_mod_mul(tmp, tmp, theirpub1, grp->p, bn_ctx) != 1)
	375	fatal("%s: BN_mod_mul (tmp = tmp * theirpub1 mod p)", __func__);
	376
	377	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
	378
5b01421b	379	if (schnorr_verify_buf(grp->p, grp->q, tmp, step2_val,
5adf6b9a	380	their_id, their_id_len,
	381	theirpriv2_s_proof, theirpriv2_s_proof_len) != 1)
	382	fatal("%s: schnorr_verify theirpriv2_s_proof failed", __func__);
	383
	384	/*
	385	* Derive shared key:
	386	* client: k = (b / g^(x2x4s))^x2 = g^((x1+x3)x2x4*s)
	387	* server: k = (a / g^(x2x4s))^x4 = g^((x1+x3)x2x4*s)
	388	*
	389	* Computed as:
	390	* client: k = (g_x4^(q - (x2 * s)) * b)^x2 mod p
	391	* server: k = (g_x2^(q - (x4 * s)) * b)^x4 mod p
	392	*/
	393	if (BN_mul(tmp, mypriv2, s, bn_ctx) != 1)
	394	fatal("%s: BN_mul (tmp = mypriv2 * s)", __func__);
	395	if (BN_mod_sub(tmp, grp->q, tmp, grp->q, bn_ctx) != 1)
	396	fatal("%s: BN_mod_sub (tmp = q - tmp mod q)", __func__);
	397	if (BN_mod_exp(tmp, theirpub2, tmp, grp->p, bn_ctx) != 1)
	398	fatal("%s: BN_mod_exp (tmp = theirpub2^tmp) mod p", __func__);
	399	if (BN_mod_mul(tmp, tmp, step2_val, grp->p, bn_ctx) != 1)
	400	fatal("%s: BN_mod_mul (tmp = tmp * step2_val) mod p", __func__);
	401	if (BN_mod_exp(*k, tmp, mypriv2, grp->p, bn_ctx) != 1)
	402	fatal("%s: BN_mod_exp (k = tmp^mypriv2) mod p", __func__);
	403
	404	BN_CTX_free(bn_ctx);
	405	BN_clear_free(tmp);
	406
	407	jpake_confirm_hash(*k, my_id, my_id_len, sess_id, sess_id_len,
	408	confirm_hash, confirm_hash_len);
	409	}
	410
	411	/*
	412	* Calculate and check confirmation hash from peer. Returns 1 on success
	413	* 0 on failure/mismatch.
	414	*/
	415	int
	416	jpake_check_confirm(const BIGNUM *k,
	417	const u_char *peer_id, u_int peer_id_len,
	418	const u_char *sess_id, u_int sess_id_len,
	419	const u_char *peer_confirm_hash, u_int peer_confirm_hash_len)
	420	{
	421	u_char *expected_confirm_hash;
	422	u_int expected_confirm_hash_len;
	423	int success = 0;
	424
	425	/* Calculate and verify expected confirmation hash */
	426	jpake_confirm_hash(k, peer_id, peer_id_len, sess_id, sess_id_len,
	427	&expected_confirm_hash, &expected_confirm_hash_len);
	428
	429	JPAKE_DEBUG_BUF((expected_confirm_hash, expected_confirm_hash_len,
	430	"%s: expected confirm hash", __func__));
	431	JPAKE_DEBUG_BUF((peer_confirm_hash, peer_confirm_hash_len,
	432	"%s: received confirm hash", __func__));
	433
	434	if (peer_confirm_hash_len != expected_confirm_hash_len)
	435	error("%s: confirmation length mismatch (my %u them %u)",
	436	__func__, expected_confirm_hash_len, peer_confirm_hash_len);
	437	else if (memcmp(peer_confirm_hash, expected_confirm_hash,
	438	expected_confirm_hash_len) == 0)
	439	success = 1;
	440	bzero(expected_confirm_hash, expected_confirm_hash_len);
	441	xfree(expected_confirm_hash);
	442	debug3("%s: success = %d", __func__, success);
	443	return success;
444	}
445
446	/* XXX main() function with tests */
447
448	#endif /* JPAKE */
449