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/**
* \file ecjpake.h
*
* \brief Elliptic curve J-PAKE
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef MBEDTLS_ECJPAKE_H
#define MBEDTLS_ECJPAKE_H
/*
* J-PAKE is a password-authenticated key exchange that allows deriving a
* strong shared secret from a (potentially low entropy) pre-shared
* passphrase, with forward secrecy and mutual authentication.
* https://en.wikipedia.org/wiki/Password_Authenticated_Key_Exchange_by_Juggling
*
* This file implements the Elliptic Curve variant of J-PAKE,
* as defined in Chapter 7.4 of the Thread v1.0 Specification,
* available to members of the Thread Group http://threadgroup.org/
*
* As the J-PAKE algorithm is inherently symmetric, so is our API.
* Each party needs to send its first round message, in any order, to the
* other party, then each sends its second round message, in any order.
* The payloads are serialized in a way suitable for use in TLS, but could
* also be use outside TLS.
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include "mbedtls/ecp.h"
#include "mbedtls/md.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* Roles in the EC J-PAKE exchange
*/
typedef enum {
MBEDTLS_ECJPAKE_CLIENT = 0, /**< Client */
MBEDTLS_ECJPAKE_SERVER, /**< Server */
} mbedtls_ecjpake_role;
#if !defined(MBEDTLS_ECJPAKE_ALT)
/**
* EC J-PAKE context structure.
*
* J-PAKE is a symmetric protocol, except for the identifiers used in
* Zero-Knowledge Proofs, and the serialization of the second message
* (KeyExchange) as defined by the Thread spec.
*
* In order to benefit from this symmetry, we choose a different naming
* convetion from the Thread v1.0 spec. Correspondance is indicated in the
* description as a pair C: client name, S: server name
*/
typedef struct mbedtls_ecjpake_context
{
const mbedtls_md_info_t *md_info; /**< Hash to use */
mbedtls_ecp_group grp; /**< Elliptic curve */
mbedtls_ecjpake_role role; /**< Are we client or server? */
int point_format; /**< Format for point export */
mbedtls_ecp_point Xm1; /**< My public key 1 C: X1, S: X3 */
mbedtls_ecp_point Xm2; /**< My public key 2 C: X2, S: X4 */
mbedtls_ecp_point Xp1; /**< Peer public key 1 C: X3, S: X1 */
mbedtls_ecp_point Xp2; /**< Peer public key 2 C: X4, S: X2 */
mbedtls_ecp_point Xp; /**< Peer public key C: Xs, S: Xc */
mbedtls_mpi xm1; /**< My private key 1 C: x1, S: x3 */
mbedtls_mpi xm2; /**< My private key 2 C: x2, S: x4 */
mbedtls_mpi s; /**< Pre-shared secret (passphrase) */
} mbedtls_ecjpake_context;
#else /* MBEDTLS_ECJPAKE_ALT */
#include "ecjpake_alt.h"
#endif /* MBEDTLS_ECJPAKE_ALT */
/**
* \brief Initialize an ECJPAKE context.
*
* \param ctx The ECJPAKE context to initialize.
* This must not be \c NULL.
*/
void mbedtls_ecjpake_init( mbedtls_ecjpake_context *ctx );
/**
* \brief Set up an ECJPAKE context for use.
*
* \note Currently the only values for hash/curve allowed by the
* standard are #MBEDTLS_MD_SHA256/#MBEDTLS_ECP_DP_SECP256R1.
*
* \param ctx The ECJPAKE context to set up. This must be initialized.
* \param role The role of the caller. This must be either
* #MBEDTLS_ECJPAKE_CLIENT or #MBEDTLS_ECJPAKE_SERVER.
* \param hash The identifier of the hash function to use,
* for example #MBEDTLS_MD_SHA256.
* \param curve The identifier of the elliptic curve to use,
* for example #MBEDTLS_ECP_DP_SECP256R1.
* \param secret The pre-shared secret (passphrase). This must be
* a readable buffer of length \p len Bytes. It need
* only be valid for the duration of this call.
* \param len The length of the pre-shared secret \p secret.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_setup( mbedtls_ecjpake_context *ctx,
mbedtls_ecjpake_role role,
mbedtls_md_type_t hash,
mbedtls_ecp_group_id curve,
const unsigned char *secret,
size_t len );
/**
* \brief Check if an ECJPAKE context is ready for use.
*
* \param ctx The ECJPAKE context to check. This must be
* initialized.
*
* \return \c 0 if the context is ready for use.
* \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA otherwise.
*/
int mbedtls_ecjpake_check( const mbedtls_ecjpake_context *ctx );
/**
* \brief Generate and write the first round message
* (TLS: contents of the Client/ServerHello extension,
* excluding extension type and length bytes).
*
* \param ctx The ECJPAKE context to use. This must be
* initialized and set up.
* \param buf The buffer to write the contents to. This must be a
* writable buffer of length \p len Bytes.
* \param len The length of \p buf in Bytes.
* \param olen The address at which to store the total number
* of Bytes written to \p buf. This must not be \c NULL.
* \param f_rng The RNG function to use. This must not be \c NULL.
* \param p_rng The RNG parameter to be passed to \p f_rng. This
* may be \c NULL if \p f_rng doesn't use a context.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_write_round_one( mbedtls_ecjpake_context *ctx,
unsigned char *buf, size_t len, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/**
* \brief Read and process the first round message
* (TLS: contents of the Client/ServerHello extension,
* excluding extension type and length bytes).
*
* \param ctx The ECJPAKE context to use. This must be initialized
* and set up.
* \param buf The buffer holding the first round message. This must
* be a readable buffer of length \p len Bytes.
* \param len The length in Bytes of \p buf.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_read_round_one( mbedtls_ecjpake_context *ctx,
const unsigned char *buf,
size_t len );
/**
* \brief Generate and write the second round message
* (TLS: contents of the Client/ServerKeyExchange).
*
* \param ctx The ECJPAKE context to use. This must be initialized,
* set up, and already have performed round one.
* \param buf The buffer to write the round two contents to.
* This must be a writable buffer of length \p len Bytes.
* \param len The size of \p buf in Bytes.
* \param olen The address at which to store the total number of Bytes
* written to \p buf. This must not be \c NULL.
* \param f_rng The RNG function to use. This must not be \c NULL.
* \param p_rng The RNG parameter to be passed to \p f_rng. This
* may be \c NULL if \p f_rng doesn't use a context.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_write_round_two( mbedtls_ecjpake_context *ctx,
unsigned char *buf, size_t len, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/**
* \brief Read and process the second round message
* (TLS: contents of the Client/ServerKeyExchange).
*
* \param ctx The ECJPAKE context to use. This must be initialized
* and set up and already have performed round one.
* \param buf The buffer holding the second round message. This must
* be a readable buffer of length \p len Bytes.
* \param len The length in Bytes of \p buf.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_read_round_two( mbedtls_ecjpake_context *ctx,
const unsigned char *buf,
size_t len );
/**
* \brief Derive the shared secret
* (TLS: Pre-Master Secret).
*
* \param ctx The ECJPAKE context to use. This must be initialized,
* set up and have performed both round one and two.
* \param buf The buffer to write the derived secret to. This must
* be a writable buffer of length \p len Bytes.
* \param len The length of \p buf in Bytes.
* \param olen The address at which to store the total number of Bytes
* written to \p buf. This must not be \c NULL.
* \param f_rng The RNG function to use. This must not be \c NULL.
* \param p_rng The RNG parameter to be passed to \p f_rng. This
* may be \c NULL if \p f_rng doesn't use a context.
*
* \return \c 0 if successful.
* \return A negative error code on failure.
*/
int mbedtls_ecjpake_derive_secret( mbedtls_ecjpake_context *ctx,
unsigned char *buf, size_t len, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
/**
* \brief This clears an ECJPAKE context and frees any
* embedded data structure.
*
* \param ctx The ECJPAKE context to free. This may be \c NULL,
* in which case this function does nothing. If it is not
* \c NULL, it must point to an initialized ECJPAKE context.
*/
void mbedtls_ecjpake_free( mbedtls_ecjpake_context *ctx );
#if defined(MBEDTLS_SELF_TEST)
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if a test failed
*/
int mbedtls_ecjpake_self_test( int verbose );
#endif /* MBEDTLS_SELF_TEST */
#ifdef __cplusplus
}
#endif
#endif /* ecjpake.h */
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