[gssapi-openssh.git] / openssh / jpake.c

/* $OpenBSD: jpake.c,v 1.1 2008/11/04 08:22:12 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"

#ifdef JPAKE

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

struct jpake_group *
jpake_default_group(void)
{
	struct jpake_group *ret;

	ret = xmalloc(sizeof(*ret));
	ret->p = ret->q = ret->g = NULL;
	if (BN_hex2bn(&ret->p, JPAKE_GROUP_P) == 0 ||
	    BN_hex2bn(&ret->g, JPAKE_GROUP_G) == 0)
		fatal("%s: BN_hex2bn", __func__);
	/* Subgroup order is p/2 (p is a safe prime) */
	if ((ret->q = BN_new()) == NULL)
		fatal("%s: BN_new", __func__);
	if (BN_rshift1(ret->q, ret->p) != 1)
		fatal("%s: BN_rshift1", __func__);

	return ret;
}

/*
 * Generate uniformly distributed random number in range (1, high).
 * Return number on success, NULL on failure.
 */
BIGNUM *
bn_rand_range_gt_one(const BIGNUM *high)
{
	BIGNUM *r, *tmp;
	int success = -1;

	if ((tmp = BN_new()) == NULL) {
		error("%s: BN_new", __func__);
		return NULL;
	}
	if ((r = BN_new()) == NULL) {
		error("%s: BN_new failed", __func__);
		goto out;
	}
	if (BN_set_word(tmp, 2) != 1) {
		error("%s: BN_set_word(tmp, 2)", __func__);
		goto out;
	}
	if (BN_sub(tmp, high, tmp) == -1) {
		error("%s: BN_sub failed (tmp = high - 2)", __func__);
		goto out;
	}
	if (BN_rand_range(r, tmp) == -1) {
		error("%s: BN_rand_range failed", __func__);
		goto out;
	}
	if (BN_set_word(tmp, 2) != 1) {
		error("%s: BN_set_word(tmp, 2)", __func__);
		goto out;
	}
	if (BN_add(r, r, tmp) == -1) {
		error("%s: BN_add failed (r = r + 2)", __func__);
		goto out;
	}
	success = 0;
 out:
	BN_clear_free(tmp);
	if (success == 0)
		return r;
	BN_clear_free(r);
	return NULL;
}

/*
 * Hash contents of buffer 'b' with hash 'md'. Returns 0 on success,
 * with digest via 'digestp' (caller to free) and length via 'lenp'.
 * Returns -1 on failure.
 */
int
hash_buffer(const u_char *buf, u_int len, const EVP_MD *md,
    u_char **digestp, u_int *lenp)
{
	u_char digest[EVP_MAX_MD_SIZE];
	u_int digest_len;
	EVP_MD_CTX evp_md_ctx;
	int success = -1;

	EVP_MD_CTX_init(&evp_md_ctx);

	if (EVP_DigestInit_ex(&evp_md_ctx, md, NULL) != 1) {
		error("%s: EVP_DigestInit_ex", __func__);
		goto out;
	}
	if (EVP_DigestUpdate(&evp_md_ctx, buf, len) != 1) {
		error("%s: EVP_DigestUpdate", __func__);
		goto out;
	}
	if (EVP_DigestFinal_ex(&evp_md_ctx, digest, &digest_len) != 1) {
		error("%s: EVP_DigestFinal_ex", __func__);
		goto out;
	}
	*digestp = xmalloc(digest_len);
	*lenp = digest_len;
	memcpy(*digestp, digest, *lenp);
	success = 0;
 out:
	EVP_MD_CTX_cleanup(&evp_md_ctx);
	bzero(digest, sizeof(digest));
	digest_len = 0;
	return success;
}

/* print formatted string followed by bignum */
void
jpake_debug3_bn(const BIGNUM *n, const char *fmt, ...)
{
	char *out, *h;
	va_list args;

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

	if (n == NULL)
		debug3("%s(null)", out);
	else {
		h = BN_bn2hex(n);
		debug3("%s0x%s", out, h);
		free(h);
	}
	free(out);
}

/* print formatted string followed by buffer contents in hex */
void
jpake_debug3_buf(const u_char *buf, u_int len, const char *fmt, ...)
{
	char *out, h[65];
	u_int i, j;
	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 length %u%s", out, len, buf == NULL ? " (null)" : "");
	free(out);
	if (buf == NULL)
		return;

	*h = '\0';
	for (i = j = 0; i < len; i++) {
		snprintf(h + j, sizeof(h) - j, "%02x", buf[i]);
		j += 2;
		if (j >= sizeof(h) - 1 || i == len - 1) {
			debug3("    %s", h);
			*h = '\0';
			j = 0;
		}
	}
}

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 jpake_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(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(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 jpake_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(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(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(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 jpake_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(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
ac450140	1	/* $OpenBSD: jpake.c,v 1.1 2008/11/04 08:22:12 djm Exp $ */
	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"
	50
	51	#ifdef JPAKE
	52
	53	/* RFC3526 group 5, 1536 bits */
	54	#define JPAKE_GROUP_G "2"
	55	#define JPAKE_GROUP_P \
	56	"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74" \
	57	"020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F1437" \
	58	"4FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
	59	"EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF05" \
	60	"98DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB" \
	61	"9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF"
	62
	63	struct jpake_group *
	64	jpake_default_group(void)
65	{
66	struct jpake_group *ret;
67
68	ret = xmalloc(sizeof(*ret));
69	ret->p = ret->q = ret->g = NULL;
70	if (BN_hex2bn(&ret->p, JPAKE_GROUP_P) == 0 \|\|
71	BN_hex2bn(&ret->g, JPAKE_GROUP_G) == 0)
72	fatal("%s: BN_hex2bn", __func__);
73	/* Subgroup order is p/2 (p is a safe prime) */
74	if ((ret->q = BN_new()) == NULL)
75	fatal("%s: BN_new", __func__);
76	if (BN_rshift1(ret->q, ret->p) != 1)
77	fatal("%s: BN_rshift1", __func__);
78
79	return ret;
80	}
81
82	/*
83	* Generate uniformly distributed random number in range (1, high).
84	* Return number on success, NULL on failure.
85	*/
86	BIGNUM *
87	bn_rand_range_gt_one(const BIGNUM *high)
88	{
89	BIGNUM r, tmp;
90	int success = -1;
91
92	if ((tmp = BN_new()) == NULL) {
93	error("%s: BN_new", __func__);
94	return NULL;
95	}
96	if ((r = BN_new()) == NULL) {
97	error("%s: BN_new failed", __func__);
98	goto out;
99	}
100	if (BN_set_word(tmp, 2) != 1) {
101	error("%s: BN_set_word(tmp, 2)", __func__);
102	goto out;
103	}
104	if (BN_sub(tmp, high, tmp) == -1) {
105	error("%s: BN_sub failed (tmp = high - 2)", __func__);
106	goto out;
107	}
108	if (BN_rand_range(r, tmp) == -1) {
109	error("%s: BN_rand_range failed", __func__);
110	goto out;
111	}
112	if (BN_set_word(tmp, 2) != 1) {
113	error("%s: BN_set_word(tmp, 2)", __func__);
114	goto out;
115	}
116	if (BN_add(r, r, tmp) == -1) {
117	error("%s: BN_add failed (r = r + 2)", __func__);
118	goto out;
119	}
120	success = 0;
121	out:
122	BN_clear_free(tmp);
123	if (success == 0)
124	return r;
125	BN_clear_free(r);
126	return NULL;
127	}
128
129	/*
130	* Hash contents of buffer 'b' with hash 'md'. Returns 0 on success,
131	* with digest via 'digestp' (caller to free) and length via 'lenp'.
132	* Returns -1 on failure.
133	*/
134	int
135	hash_buffer(const u_char buf, u_int len, const EVP_MD md,
136	u_char *digestp, u_int lenp)
137	{
138	u_char digest[EVP_MAX_MD_SIZE];
139	u_int digest_len;
140	EVP_MD_CTX evp_md_ctx;
141	int success = -1;
142
143	EVP_MD_CTX_init(&evp_md_ctx);
144
145	if (EVP_DigestInit_ex(&evp_md_ctx, md, NULL) != 1) {
146	error("%s: EVP_DigestInit_ex", __func__);
147	goto out;
148	}
149	if (EVP_DigestUpdate(&evp_md_ctx, buf, len) != 1) {
150	error("%s: EVP_DigestUpdate", __func__);
151	goto out;
152	}
153	if (EVP_DigestFinal_ex(&evp_md_ctx, digest, &digest_len) != 1) {
154	error("%s: EVP_DigestFinal_ex", __func__);
155	goto out;
156	}
157	*digestp = xmalloc(digest_len);
158	*lenp = digest_len;
159	memcpy(digestp, digest, lenp);
160	success = 0;
161	out:
162	EVP_MD_CTX_cleanup(&evp_md_ctx);
163	bzero(digest, sizeof(digest));
164	digest_len = 0;
165	return success;
166	}
167
168	/* print formatted string followed by bignum */
169	void
170	jpake_debug3_bn(const BIGNUM n, const char fmt, ...)
171	{
172	char out, h;
173	va_list args;
174
175	out = NULL;
176	va_start(args, fmt);
177	vasprintf(&out, fmt, args);
178	va_end(args);
179	if (out == NULL)
180	fatal("%s: vasprintf failed", __func__);
181
182	if (n == NULL)
183	debug3("%s(null)", out);
184	else {
185	h = BN_bn2hex(n);
186	debug3("%s0x%s", out, h);
187	free(h);
188	}
189	free(out);
190	}
191
192	/* print formatted string followed by buffer contents in hex */
193	void
194	jpake_debug3_buf(const u_char buf, u_int len, const char fmt, ...)
195	{
196	char *out, h[65];
197	u_int i, j;
198	va_list args;
199
200	out = NULL;
201	va_start(args, fmt);
202	vasprintf(&out, fmt, args);
203	va_end(args);
204	if (out == NULL)
205	fatal("%s: vasprintf failed", __func__);
206
207	debug3("%s length %u%s", out, len, buf == NULL ? " (null)" : "");
208	free(out);
209	if (buf == NULL)
210	return;
211
212	*h = '\0';
213	for (i = j = 0; i < len; i++) {
214	snprintf(h + j, sizeof(h) - j, "%02x", buf[i]);
215	j += 2;
216	if (j >= sizeof(h) - 1 \|\| i == len - 1) {
217	debug3(" %s", h);
218	*h = '\0';
219	j = 0;
220	}
221	}
222	}
223
224	struct jpake_ctx *
225	jpake_new(void)
226	{
227	struct jpake_ctx *ret;
228
229	ret = xcalloc(1, sizeof(*ret));
230
231	ret->grp = jpake_default_group();
232
233	ret->s = ret->k = NULL;
234	ret->x1 = ret->x2 = ret->x3 = ret->x4 = NULL;
235	ret->g_x1 = ret->g_x2 = ret->g_x3 = ret->g_x4 = NULL;
236	ret->a = ret->b = NULL;
237
238	ret->client_id = ret->server_id = NULL;
239	ret->h_k_cid_sessid = ret->h_k_sid_sessid = NULL;
240
241	debug3("%s: alloc %p", __func__, ret);
242
243	return ret;
244	}
245
246
247	void
248	jpake_free(struct jpake_ctx *pctx)
249	{
250	debug3("%s: free %p", __func__, pctx);
251
252	#define JPAKE_BN_CLEAR_FREE(v) \
253	do { \
254	if ((v) != NULL) { \
255	BN_clear_free(v); \
256	(v) = NULL; \
257	} \
258	} while (0)
259	#define JPAKE_BUF_CLEAR_FREE(v, l) \
260	do { \
261	if ((v) != NULL) { \
262	bzero((v), (l)); \
263	xfree(v); \
264	(v) = NULL; \
265	(l) = 0; \
266	} \
267	} while (0)
268
269	JPAKE_BN_CLEAR_FREE(pctx->s);
270	JPAKE_BN_CLEAR_FREE(pctx->k);
271	JPAKE_BN_CLEAR_FREE(pctx->x1);
272	JPAKE_BN_CLEAR_FREE(pctx->x2);
273	JPAKE_BN_CLEAR_FREE(pctx->x3);
274	JPAKE_BN_CLEAR_FREE(pctx->x4);
275	JPAKE_BN_CLEAR_FREE(pctx->g_x1);
276	JPAKE_BN_CLEAR_FREE(pctx->g_x2);
277	JPAKE_BN_CLEAR_FREE(pctx->g_x3);
278	JPAKE_BN_CLEAR_FREE(pctx->g_x4);
279	JPAKE_BN_CLEAR_FREE(pctx->a);
280	JPAKE_BN_CLEAR_FREE(pctx->b);
281
282	JPAKE_BUF_CLEAR_FREE(pctx->client_id, pctx->client_id_len);
283	JPAKE_BUF_CLEAR_FREE(pctx->server_id, pctx->server_id_len);
284	JPAKE_BUF_CLEAR_FREE(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
285	JPAKE_BUF_CLEAR_FREE(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
286
287	#undef JPAKE_BN_CLEAR_FREE
288	#undef JPAKE_BUF_CLEAR_FREE
289
290	bzero(pctx, sizeof(pctx));
291	xfree(pctx);
292	}
293
294	/* dump entire jpake_ctx. NB. includes private values! */
295	void
296	jpake_dump(struct jpake_ctx pctx, const char fmt, ...)
297	{
298	char *out;
299	va_list args;
300
301	out = NULL;
302	va_start(args, fmt);
303	vasprintf(&out, fmt, args);
304	va_end(args);
305	if (out == NULL)
306	fatal("%s: vasprintf failed", __func__);
307
308	debug3("%s: %s (ctx at %p)", __func__, out, pctx);
309	if (pctx == NULL) {
310	free(out);
311	return;
312	}
313
314	#define JPAKE_DUMP_BN(a) do { \
315	if ((a) != NULL) \
316	JPAKE_DEBUG_BN(((a), "%s = ", #a)); \
317	} while (0)
318	#define JPAKE_DUMP_BUF(a, b) do { \
319	if ((a) != NULL) \
320	JPAKE_DEBUG_BUF((a, b, "%s", #a)); \
321	} while (0)
322
323	JPAKE_DUMP_BN(pctx->s);
324	JPAKE_DUMP_BN(pctx->k);
325	JPAKE_DUMP_BN(pctx->x1);
326	JPAKE_DUMP_BN(pctx->x2);
327	JPAKE_DUMP_BN(pctx->x3);
328	JPAKE_DUMP_BN(pctx->x4);
329	JPAKE_DUMP_BN(pctx->g_x1);
330	JPAKE_DUMP_BN(pctx->g_x2);
331	JPAKE_DUMP_BN(pctx->g_x3);
332	JPAKE_DUMP_BN(pctx->g_x4);
333	JPAKE_DUMP_BN(pctx->a);
334	JPAKE_DUMP_BN(pctx->b);
335
336	JPAKE_DUMP_BUF(pctx->client_id, pctx->client_id_len);
337	JPAKE_DUMP_BUF(pctx->server_id, pctx->server_id_len);
338	JPAKE_DUMP_BUF(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
339	JPAKE_DUMP_BUF(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
340
341	debug3("%s: %s done", __func__, out);
342	free(out);
343	}
344
345	/* Shared parts of step 1 exchange calculation */
346	void
347	jpake_step1(struct jpake_group *grp,
348	u_char *id, u_int id_len,
349	BIGNUM priv1, BIGNUM priv2, BIGNUM g_priv1, BIGNUM g_priv2,
350	u_char *priv1_proof, u_int priv1_proof_len,
351	u_char *priv2_proof, u_int priv2_proof_len)
352	{
353	BN_CTX *bn_ctx;
354
355	if ((bn_ctx = BN_CTX_new()) == NULL)
356	fatal("%s: BN_CTX_new", __func__);
357
358	/* Random nonce to prevent replay */
359	*id = xmalloc(KZP_ID_LEN);
360	*id_len = KZP_ID_LEN;
361	arc4random_buf(id, id_len);
362
363	/*
364	* x1/x3 is a random element of Zq
365	* x2/x4 is a random element of Z*q
366	* We also exclude [1] from x1/x3 candidates and [0, 1] from
367	* x2/x4 candiates to avoid possible degeneracy (i.e. g^0, g^1).
368	*/
369	if ((*priv1 = bn_rand_range_gt_one(grp->q)) == NULL \|\|
370	(*priv2 = bn_rand_range_gt_one(grp->q)) == NULL)
371	fatal("%s: bn_rand_range_gt_one", __func__);
372
373	/*
374	* client: g_x1 = g^x1 mod p / server: g_x3 = g^x3 mod p
375	* client: g_x2 = g^x2 mod p / server: g_x4 = g^x4 mod p
376	*/
377	if ((*g_priv1 = BN_new()) == NULL \|\|
378	(*g_priv2 = BN_new()) == NULL)
379	fatal("%s: BN_new", __func__);
380	if (BN_mod_exp(g_priv1, grp->g, priv1, grp->p, bn_ctx) == -1)
381	fatal("%s: BN_mod_exp", __func__);
382	if (BN_mod_exp(g_priv2, grp->g, priv2, grp->p, bn_ctx) == -1)
383	fatal("%s: BN_mod_exp", __func__);
384
385	/* Generate proofs for holding x1/x3 and x2/x4 */
386	if (schnorr_sign(grp->p, grp->q, grp->g,
387	priv1, g_priv1, id, id_len,
388	priv1_proof, priv1_proof_len) != 0)
389	fatal("%s: schnorr_sign", __func__);
390	if (schnorr_sign(grp->p, grp->q, grp->g,
391	priv2, g_priv2, id, id_len,
392	priv2_proof, priv2_proof_len) != 0)
393	fatal("%s: schnorr_sign", __func__);
394
395	BN_CTX_free(bn_ctx);
396	}
397
398	/* Shared parts of step 2 exchange calculation */
399	void
400	jpake_step2(struct jpake_group grp, BIGNUM s,
401	BIGNUM mypub1, BIGNUM theirpub1, BIGNUM theirpub2, BIGNUM mypriv2,
402	const u_char *theirid, u_int theirid_len,
403	const u_char *myid, u_int myid_len,
404	const u_char *theirpub1_proof, u_int theirpub1_proof_len,
405	const u_char *theirpub2_proof, u_int theirpub2_proof_len,
406	BIGNUM **newpub,
407	u_char *newpub_exponent_proof, u_int newpub_exponent_proof_len)
408	{
409	BN_CTX *bn_ctx;
410	BIGNUM tmp, exponent;
411
412	/* Validate peer's step 1 values */
413	if (BN_cmp(theirpub1, BN_value_one()) <= 0)
414	fatal("%s: theirpub1 <= 1", __func__);
415	if (BN_cmp(theirpub2, BN_value_one()) <= 0)
416	fatal("%s: theirpub2 <= 1", __func__);
417
418	if (schnorr_verify(grp->p, grp->q, grp->g, theirpub1,
419	theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1)
420	fatal("%s: schnorr_verify theirpub1 failed", __func__);
421	if (schnorr_verify(grp->p, grp->q, grp->g, theirpub2,
422	theirid, theirid_len, theirpub2_proof, theirpub2_proof_len) != 1)
423	fatal("%s: schnorr_verify theirpub2 failed", __func__);
424
425	if ((bn_ctx = BN_CTX_new()) == NULL)
426	fatal("%s: BN_CTX_new", __func__);
427
428	if ((*newpub = BN_new()) == NULL \|\|
429	(tmp = BN_new()) == NULL \|\|
430	(exponent = BN_new()) == NULL)
431	fatal("%s: BN_new", __func__);
432
433	/*
434	* client: exponent = x2 * s mod p
435	* server: exponent = x4 * s mod p
436	*/
437	if (BN_mod_mul(exponent, mypriv2, s, grp->q, bn_ctx) != 1)
438	fatal("%s: BN_mod_mul (exponent = mypriv2 * s mod p)",
439	__func__);
440
441	/*
442	* client: tmp = g^(x1 + x3 + x4) mod p
443	* server: tmp = g^(x1 + x2 + x3) mod p
444	*/
445	if (BN_mod_mul(tmp, mypub1, theirpub1, grp->p, bn_ctx) != 1)
446	fatal("%s: BN_mod_mul (tmp = mypub1 * theirpub1 mod p)",
447	__func__);
448	if (BN_mod_mul(tmp, tmp, theirpub2, grp->p, bn_ctx) != 1)
449	fatal("%s: BN_mod_mul (tmp = tmp * theirpub2 mod p)", __func__);
450
451	/*
452	* client: a = tmp^exponent = g^((x1+x3+x4) * x2 * s) mod p
453	* server: b = tmp^exponent = g^((x1+x2+x3) * x4 * s) mod p
454	*/
455	if (BN_mod_exp(*newpub, tmp, exponent, grp->p, bn_ctx) != 1)
456	fatal("%s: BN_mod_mul (newpub = tmp^exponent mod p)", __func__);
457
458	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
459	JPAKE_DEBUG_BN((exponent, "%s: exponent = ", __func__));
460
461	/* Note the generator here is 'tmp', not g */
462	if (schnorr_sign(grp->p, grp->q, tmp, exponent, *newpub,
463	myid, myid_len,
464	newpub_exponent_proof, newpub_exponent_proof_len) != 0)
465	fatal("%s: schnorr_sign newpub", __func__);
466
467	BN_clear_free(tmp); /* XXX stash for later use? */
468	BN_clear_free(exponent); /* XXX stash for later use? (yes, in conf) */
469
470	BN_CTX_free(bn_ctx);
471	}
472
473	/* Confirmation hash calculation */
474	void
475	jpake_confirm_hash(const BIGNUM *k,
476	const u_char *endpoint_id, u_int endpoint_id_len,
477	const u_char *sess_id, u_int sess_id_len,
478	u_char *confirm_hash, u_int confirm_hash_len)
479	{
480	Buffer b;
481
482	/*
483	* Calculate confirmation proof:
484	* client: H(k \|\| client_id \|\| session_id)
485	* server: H(k \|\| server_id \|\| session_id)
486	*/
487	buffer_init(&b);
488	buffer_put_bignum2(&b, k);
489	buffer_put_string(&b, endpoint_id, endpoint_id_len);
490	buffer_put_string(&b, sess_id, sess_id_len);
491	if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
492	confirm_hash, confirm_hash_len) != 0)
493	fatal("%s: hash_buffer", __func__);
494	buffer_free(&b);
495	}
496
497	/* Shared parts of key derivation and confirmation calculation */
498	void
499	jpake_key_confirm(struct jpake_group grp, BIGNUM s, BIGNUM *step2_val,
500	BIGNUM mypriv2, BIGNUM mypub1, BIGNUM *mypub2,
501	BIGNUM theirpub1, BIGNUM theirpub2,
502	const u_char *my_id, u_int my_id_len,
503	const u_char *their_id, u_int their_id_len,
504	const u_char *sess_id, u_int sess_id_len,
505	const u_char *theirpriv2_s_proof, u_int theirpriv2_s_proof_len,
506	BIGNUM **k,
507	u_char *confirm_hash, u_int confirm_hash_len)
508	{
509	BN_CTX *bn_ctx;
510	BIGNUM *tmp;
511
512	if ((bn_ctx = BN_CTX_new()) == NULL)
513	fatal("%s: BN_CTX_new", __func__);
514	if ((tmp = BN_new()) == NULL \|\|
515	(*k = BN_new()) == NULL)
516	fatal("%s: BN_new", __func__);
517
518	/* Validate step 2 values */
519	if (BN_cmp(step2_val, BN_value_one()) <= 0)
520	fatal("%s: step2_val <= 1", __func__);
521
522	/*
523	* theirpriv2_s_proof is calculated with a different generator:
524	* tmp = g^(mypriv1+mypriv2+theirpub1) = g^mypub1g^mypub2g^theirpub1
525	* Calculate it here so we can check the signature.
526	*/
527	if (BN_mod_mul(tmp, mypub1, mypub2, grp->p, bn_ctx) != 1)
528	fatal("%s: BN_mod_mul (tmp = mypub1 * mypub2 mod p)", __func__);
529	if (BN_mod_mul(tmp, tmp, theirpub1, grp->p, bn_ctx) != 1)
530	fatal("%s: BN_mod_mul (tmp = tmp * theirpub1 mod p)", __func__);
531
532	JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
533
534	if (schnorr_verify(grp->p, grp->q, tmp, step2_val,
535	their_id, their_id_len,
536	theirpriv2_s_proof, theirpriv2_s_proof_len) != 1)
537	fatal("%s: schnorr_verify theirpriv2_s_proof failed", __func__);
538
539	/*
540	* Derive shared key:
541	* client: k = (b / g^(x2x4s))^x2 = g^((x1+x3)x2x4*s)
542	* server: k = (a / g^(x2x4s))^x4 = g^((x1+x3)x2x4*s)
543	*
544	* Computed as:
545	* client: k = (g_x4^(q - (x2 * s)) * b)^x2 mod p
546	* server: k = (g_x2^(q - (x4 * s)) * b)^x4 mod p
547	*/
548	if (BN_mul(tmp, mypriv2, s, bn_ctx) != 1)
549	fatal("%s: BN_mul (tmp = mypriv2 * s)", __func__);
550	if (BN_mod_sub(tmp, grp->q, tmp, grp->q, bn_ctx) != 1)
551	fatal("%s: BN_mod_sub (tmp = q - tmp mod q)", __func__);
552	if (BN_mod_exp(tmp, theirpub2, tmp, grp->p, bn_ctx) != 1)
553	fatal("%s: BN_mod_exp (tmp = theirpub2^tmp) mod p", __func__);
554	if (BN_mod_mul(tmp, tmp, step2_val, grp->p, bn_ctx) != 1)
555	fatal("%s: BN_mod_mul (tmp = tmp * step2_val) mod p", __func__);
556	if (BN_mod_exp(*k, tmp, mypriv2, grp->p, bn_ctx) != 1)
557	fatal("%s: BN_mod_exp (k = tmp^mypriv2) mod p", __func__);
558
559	BN_CTX_free(bn_ctx);
560	BN_clear_free(tmp);
561
562	jpake_confirm_hash(*k, my_id, my_id_len, sess_id, sess_id_len,
563	confirm_hash, confirm_hash_len);
564	}
565
566	/*
567	* Calculate and check confirmation hash from peer. Returns 1 on success
568	* 0 on failure/mismatch.
569	*/
570	int
571	jpake_check_confirm(const BIGNUM *k,
572	const u_char *peer_id, u_int peer_id_len,
573	const u_char *sess_id, u_int sess_id_len,
574	const u_char *peer_confirm_hash, u_int peer_confirm_hash_len)
575	{
576	u_char *expected_confirm_hash;
577	u_int expected_confirm_hash_len;
578	int success = 0;
579
580	/* Calculate and verify expected confirmation hash */
581	jpake_confirm_hash(k, peer_id, peer_id_len, sess_id, sess_id_len,
582	&expected_confirm_hash, &expected_confirm_hash_len);
583
584	JPAKE_DEBUG_BUF((expected_confirm_hash, expected_confirm_hash_len,
585	"%s: expected confirm hash", __func__));
586	JPAKE_DEBUG_BUF((peer_confirm_hash, peer_confirm_hash_len,
587	"%s: received confirm hash", __func__));
588
589	if (peer_confirm_hash_len != expected_confirm_hash_len)
590	error("%s: confirmation length mismatch (my %u them %u)",
591	__func__, expected_confirm_hash_len, peer_confirm_hash_len);
592	else if (memcmp(peer_confirm_hash, expected_confirm_hash,
593	expected_confirm_hash_len) == 0)
594	success = 1;
595	bzero(expected_confirm_hash, expected_confirm_hash_len);
596	xfree(expected_confirm_hash);
597	debug3("%s: success = %d", __func__, success);
598	return success;
599	}
600
601	/* XXX main() function with tests */
602
603	#endif /* JPAKE */
604