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Add support for an experimental zero-knowledge password authentication
method using the J-PAKE protocol described in F. Hao, P. Ryan,
"Password Authenticated Key Exchange by Juggling", 16th Workshop on
Security Protocols, Cambridge, April 2008.

This method allows password-based authentication without exposing
the password to the server. Instead, the client and server exchange
cryptographic proofs to demonstrate of knowledge of the password while
revealing nothing useful to an attacker or compromised endpoint.

This is experimental, work-in-progress code and is presently
compiled-time disabled (turn on -DJPAKE in Makefile.inc).

"just commit it.  It isn't too intrusive." deraadt@

/* $OpenBSD: jpake.h,v 1.1 2008/11/04 08:22:13 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.
 */

#ifndef JPAKE_H
#define JPAKE_H

#include <sys/types.h>

#include <openssl/bn.h>

/* Set JPAKE_DEBUG in CFLAGS for privacy-violating debugging */
#ifndef JPAKE_DEBUG
# define JPAKE_DEBUG_BN(a)
# define JPAKE_DEBUG_BUF(a)
# define JPAKE_DEBUG_CTX(a)
#else
# define JPAKE_DEBUG_BN(a)	jpake_debug3_bn a
# define JPAKE_DEBUG_BUF(a)	jpake_debug3_buf a
# define JPAKE_DEBUG_CTX(a)	jpake_dump a
#endif /* SCHNORR_DEBUG */

struct jpake_group {
	BIGNUM *p, *q, *g;
};

#define KZP_ID_LEN	16	/* Length of client and server IDs */

struct jpake_ctx {
	/* Parameters */
	struct jpake_group *grp;

	/* Private values shared by client and server */
	BIGNUM *s;			/* Secret (salted, crypted password) */
	BIGNUM *k;			/* Derived key */

	/* Client private values (NULL for server) */
	BIGNUM *x1;			/* random in Zq */
	BIGNUM *x2;			/* random in Z*q */

	/* Server private values (NULL for server) */
	BIGNUM *x3;			/* random in Zq */
	BIGNUM *x4;			/* random in Z*q */

	/* Step 1: C->S */
	u_char *client_id;		/* Anti-replay nonce */
	u_int client_id_len;
	BIGNUM *g_x1;			/* g^x1 */
	BIGNUM *g_x2;			/* g^x2 */

	/* Step 1: S->C */
	u_char *server_id;		/* Anti-replay nonce */
	u_int server_id_len;
	BIGNUM *g_x3;			/* g^x3 */
	BIGNUM *g_x4;			/* g^x4 */

	/* Step 2: C->S */
	BIGNUM *a;			/* g^((x1+x3+x4)*x2*s) */

	/* Step 2: S->C */
	BIGNUM *b;			/* g^((x1+x2+x3)*x4*s) */

	/* Confirmation: C->S */
	u_char *h_k_cid_sessid;		/* H(k || client_id || session_id) */
	u_int h_k_cid_sessid_len;

	/* Confirmation: S->C */
	u_char *h_k_sid_sessid;		/* H(k || server_id || session_id) */
	u_int h_k_sid_sessid_len;
};

/* jpake.c */
struct jpake_group *jpake_default_group(void);
BIGNUM *bn_rand_range_gt_one(const BIGNUM *high);
int hash_buffer(const u_char *, u_int, const EVP_MD *, u_char **, u_int *);
void jpake_debug3_bn(const BIGNUM *, const char *, ...)
    __attribute__((__nonnull__ (2)))
    __attribute__((format(printf, 2, 3)));
void jpake_debug3_buf(const u_char *, u_int, const char *, ...)
    __attribute__((__nonnull__ (3)))
    __attribute__((format(printf, 3, 4)));
void jpake_dump(struct jpake_ctx *, const char *, ...)
    __attribute__((__nonnull__ (2)))
    __attribute__((format(printf, 2, 3)));
struct jpake_ctx *jpake_new(void);
void jpake_free(struct jpake_ctx *);

void jpake_step1(struct jpake_group *, u_char **, u_int *,
    BIGNUM **, BIGNUM **, BIGNUM **, BIGNUM **,
    u_char **, u_int *, u_char **, u_int *);

void jpake_step2(struct jpake_group *, BIGNUM *,
    BIGNUM *, BIGNUM *, BIGNUM *, BIGNUM *,
    const u_char *, u_int, const u_char *, u_int,
    const u_char *, u_int, const u_char *, u_int,
    BIGNUM **, u_char **, u_int *);

void jpake_confirm_hash(const BIGNUM *,
    const u_char *, u_int,
    const u_char *, u_int,
    u_char **, u_int *);

void jpake_key_confirm(struct jpake_group *, BIGNUM *, BIGNUM *,
    BIGNUM *, BIGNUM *, BIGNUM *, BIGNUM *, BIGNUM *,
    const u_char *, u_int, const u_char *, u_int,
    const u_char *, u_int, const u_char *, u_int,
    BIGNUM **, u_char **, u_int *);

int jpake_check_confirm(const BIGNUM *, const u_char *, u_int,
    const u_char *, u_int, const u_char *, u_int);

/* schnorr.c */
int schnorr_sign(const BIGNUM *, const BIGNUM *, const BIGNUM *,
    const BIGNUM *, const BIGNUM *, const u_char *, u_int ,
    u_char **, u_int *);
int schnorr_verify(const BIGNUM *, const BIGNUM *, const BIGNUM *, 
    const BIGNUM *, const u_char *, u_int,
    const u_char *, u_int);

#endif /* JPAKE_H */