1 /** 2 * \file ecjpake.h 3 * 4 * \brief Elliptic curve J-PAKE 5 */ 6 /* 7 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 8 * SPDX-License-Identifier: Apache-2.0 9 * 10 * Licensed under the Apache License, Version 2.0 (the "License"); you may 11 * not use this file except in compliance with the License. 12 * You may obtain a copy of the License at 13 * 14 * http://www.apache.org/licenses/LICENSE-2.0 15 * 16 * Unless required by applicable law or agreed to in writing, software 17 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 18 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 19 * See the License for the specific language governing permissions and 20 * limitations under the License. 21 * 22 * This file is part of mbed TLS (https://tls.mbed.org) 23 */ 24 #ifndef MBEDTLS_ECJPAKE_H 25 #define MBEDTLS_ECJPAKE_H 26 27 /* 28 * J-PAKE is a password-authenticated key exchange that allows deriving a 29 * strong shared secret from a (potentially low entropy) pre-shared 30 * passphrase, with forward secrecy and mutual authentication. 31 * https://en.wikipedia.org/wiki/Password_Authenticated_Key_Exchange_by_Juggling 32 * 33 * This file implements the Elliptic Curve variant of J-PAKE, 34 * as defined in Chapter 7.4 of the Thread v1.0 Specification, 35 * available to members of the Thread Group http://threadgroup.org/ 36 * 37 * As the J-PAKE algorithm is inherently symmetric, so is our API. 38 * Each party needs to send its first round message, in any order, to the 39 * other party, then each sends its second round message, in any order. 40 * The payloads are serialized in a way suitable for use in TLS, but could 41 * also be use outside TLS. 42 */ 43 44 #include "ecp.h" 45 #include "md.h" 46 47 #ifdef __cplusplus 48 extern "C" { 49 #endif 50 51 /** 52 * Roles in the EC J-PAKE exchange 53 */ 54 typedef enum { 55 MBEDTLS_ECJPAKE_CLIENT = 0, /**< Client */ 56 MBEDTLS_ECJPAKE_SERVER, /**< Server */ 57 } mbedtls_ecjpake_role; 58 59 #if !defined(MBEDTLS_ECJPAKE_ALT) 60 /** 61 * EC J-PAKE context structure. 62 * 63 * J-PAKE is a symmetric protocol, except for the identifiers used in 64 * Zero-Knowledge Proofs, and the serialization of the second message 65 * (KeyExchange) as defined by the Thread spec. 66 * 67 * In order to benefit from this symmetry, we choose a different naming 68 * convetion from the Thread v1.0 spec. Correspondance is indicated in the 69 * description as a pair C: client name, S: server name 70 */ 71 typedef struct mbedtls_ecjpake_context 72 { 73 const mbedtls_md_info_t *md_info; /**< Hash to use */ 74 mbedtls_ecp_group grp; /**< Elliptic curve */ 75 mbedtls_ecjpake_role role; /**< Are we client or server? */ 76 int point_format; /**< Format for point export */ 77 78 mbedtls_ecp_point Xm1; /**< My public key 1 C: X1, S: X3 */ 79 mbedtls_ecp_point Xm2; /**< My public key 2 C: X2, S: X4 */ 80 mbedtls_ecp_point Xp1; /**< Peer public key 1 C: X3, S: X1 */ 81 mbedtls_ecp_point Xp2; /**< Peer public key 2 C: X4, S: X2 */ 82 mbedtls_ecp_point Xp; /**< Peer public key C: Xs, S: Xc */ 83 84 mbedtls_mpi xm1; /**< My private key 1 C: x1, S: x3 */ 85 mbedtls_mpi xm2; /**< My private key 2 C: x2, S: x4 */ 86 87 mbedtls_mpi s; /**< Pre-shared secret (passphrase) */ 88 } mbedtls_ecjpake_context; 89 90 #else /* MBEDTLS_ECJPAKE_ALT */ 91 #include "ecjpake_alt.h" 92 #endif /* MBEDTLS_ECJPAKE_ALT */ 93 94 /** 95 * \brief Initialize an ECJPAKE context. 96 * 97 * \param ctx The ECJPAKE context to initialize. 98 * This must not be \c NULL. 99 */ 100 void mbedtls_ecjpake_init( mbedtls_ecjpake_context *ctx ); 101 102 /** 103 * \brief Set up an ECJPAKE context for use. 104 * 105 * \note Currently the only values for hash/curve allowed by the 106 * standard are #MBEDTLS_MD_SHA256/#MBEDTLS_ECP_DP_SECP256R1. 107 * 108 * \param ctx The ECJPAKE context to set up. This must be initialized. 109 * \param role The role of the caller. This must be either 110 * #MBEDTLS_ECJPAKE_CLIENT or #MBEDTLS_ECJPAKE_SERVER. 111 * \param hash The identifier of the hash function to use, 112 * for example #MBEDTLS_MD_SHA256. 113 * \param curve The identifier of the elliptic curve to use, 114 * for example #MBEDTLS_ECP_DP_SECP256R1. 115 * \param secret The pre-shared secret (passphrase). This must be 116 * a readable buffer of length \p len Bytes. It need 117 * only be valid for the duration of this call. 118 * \param len The length of the pre-shared secret \p secret. 119 * 120 * \return \c 0 if successful. 121 * \return A negative error code on failure. 122 */ 123 int mbedtls_ecjpake_setup( mbedtls_ecjpake_context *ctx, 124 mbedtls_ecjpake_role role, 125 mbedtls_md_type_t hash, 126 mbedtls_ecp_group_id curve, 127 const unsigned char *secret, 128 size_t len ); 129 130 /** 131 * \brief Check if an ECJPAKE context is ready for use. 132 * 133 * \param ctx The ECJPAKE context to check. This must be 134 * initialized. 135 * 136 * \return \c 0 if the context is ready for use. 137 * \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA otherwise. 138 */ 139 int mbedtls_ecjpake_check( const mbedtls_ecjpake_context *ctx ); 140 141 /** 142 * \brief Generate and write the first round message 143 * (TLS: contents of the Client/ServerHello extension, 144 * excluding extension type and length bytes). 145 * 146 * \param ctx The ECJPAKE context to use. This must be 147 * initialized and set up. 148 * \param buf The buffer to write the contents to. This must be a 149 * writable buffer of length \p len Bytes. 150 * \param len The length of \p buf in Bytes. 151 * \param olen The address at which to store the total number 152 * of Bytes written to \p buf. This must not be \c NULL. 153 * \param f_rng The RNG function to use. This must not be \c NULL. 154 * \param p_rng The RNG parameter to be passed to \p f_rng. This 155 * may be \c NULL if \p f_rng doesn't use a context. 156 * 157 * \return \c 0 if successful. 158 * \return A negative error code on failure. 159 */ 160 int mbedtls_ecjpake_write_round_one( mbedtls_ecjpake_context *ctx, 161 unsigned char *buf, size_t len, size_t *olen, 162 int (*f_rng)(void *, unsigned char *, size_t), 163 void *p_rng ); 164 165 /** 166 * \brief Read and process the first round message 167 * (TLS: contents of the Client/ServerHello extension, 168 * excluding extension type and length bytes). 169 * 170 * \param ctx The ECJPAKE context to use. This must be initialized 171 * and set up. 172 * \param buf The buffer holding the first round message. This must 173 * be a readable buffer of length \p len Bytes. 174 * \param len The length in Bytes of \p buf. 175 * 176 * \return \c 0 if successful. 177 * \return A negative error code on failure. 178 */ 179 int mbedtls_ecjpake_read_round_one( mbedtls_ecjpake_context *ctx, 180 const unsigned char *buf, 181 size_t len ); 182 183 /** 184 * \brief Generate and write the second round message 185 * (TLS: contents of the Client/ServerKeyExchange). 186 * 187 * \param ctx The ECJPAKE context to use. This must be initialized, 188 * set up, and already have performed round one. 189 * \param buf The buffer to write the round two contents to. 190 * This must be a writable buffer of length \p len Bytes. 191 * \param len The size of \p buf in Bytes. 192 * \param olen The address at which to store the total number of Bytes 193 * written to \p buf. This must not be \c NULL. 194 * \param f_rng The RNG function to use. This must not be \c NULL. 195 * \param p_rng The RNG parameter to be passed to \p f_rng. This 196 * may be \c NULL if \p f_rng doesn't use a context. 197 * 198 * \return \c 0 if successful. 199 * \return A negative error code on failure. 200 */ 201 int mbedtls_ecjpake_write_round_two( mbedtls_ecjpake_context *ctx, 202 unsigned char *buf, size_t len, size_t *olen, 203 int (*f_rng)(void *, unsigned char *, size_t), 204 void *p_rng ); 205 206 /** 207 * \brief Read and process the second round message 208 * (TLS: contents of the Client/ServerKeyExchange). 209 * 210 * \param ctx The ECJPAKE context to use. This must be initialized 211 * and set up and already have performed round one. 212 * \param buf The buffer holding the second round message. This must 213 * be a readable buffer of length \p len Bytes. 214 * \param len The length in Bytes of \p buf. 215 * 216 * \return \c 0 if successful. 217 * \return A negative error code on failure. 218 */ 219 int mbedtls_ecjpake_read_round_two( mbedtls_ecjpake_context *ctx, 220 const unsigned char *buf, 221 size_t len ); 222 223 /** 224 * \brief Derive the shared secret 225 * (TLS: Pre-Master Secret). 226 * 227 * \param ctx The ECJPAKE context to use. This must be initialized, 228 * set up and have performed both round one and two. 229 * \param buf The buffer to write the derived secret to. This must 230 * be a writable buffer of length \p len Bytes. 231 * \param len The length of \p buf in Bytes. 232 * \param olen The address at which to store the total number of Bytes 233 * written to \p buf. This must not be \c NULL. 234 * \param f_rng The RNG function to use. This must not be \c NULL. 235 * \param p_rng The RNG parameter to be passed to \p f_rng. This 236 * may be \c NULL if \p f_rng doesn't use a context. 237 * 238 * \return \c 0 if successful. 239 * \return A negative error code on failure. 240 */ 241 int mbedtls_ecjpake_derive_secret( mbedtls_ecjpake_context *ctx, 242 unsigned char *buf, size_t len, size_t *olen, 243 int (*f_rng)(void *, unsigned char *, size_t), 244 void *p_rng ); 245 246 /** 247 * \brief This clears an ECJPAKE context and frees any 248 * embedded data structure. 249 * 250 * \param ctx The ECJPAKE context to free. This may be \c NULL, 251 * in which case this function does nothing. If it is not 252 * \c NULL, it must point to an initialized ECJPAKE context. 253 */ 254 void mbedtls_ecjpake_free( mbedtls_ecjpake_context *ctx ); 255 256 #if defined(MBEDTLS_SELF_TEST) 257 258 /** 259 * \brief Checkup routine 260 * 261 * \return 0 if successful, or 1 if a test failed 262 */ 263 int mbedtls_ecjpake_self_test( int verbose ); 264 265 #endif /* MBEDTLS_SELF_TEST */ 266 267 #ifdef __cplusplus 268 } 269 #endif 270 271 272 #endif /* ecjpake.h */ 273