1 /** 2 * \file ecjpake.h 3 * 4 * \brief Elliptic curve J-PAKE 5 */ 6 /* 7 * Copyright The Mbed TLS Contributors 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 #ifndef MBEDTLS_ECJPAKE_H 23 #define MBEDTLS_ECJPAKE_H 24 #include "mbedtls/private_access.h" 25 26 /* 27 * J-PAKE is a password-authenticated key exchange that allows deriving a 28 * strong shared secret from a (potentially low entropy) pre-shared 29 * passphrase, with forward secrecy and mutual authentication. 30 * https://en.wikipedia.org/wiki/Password_Authenticated_Key_Exchange_by_Juggling 31 * 32 * This file implements the Elliptic Curve variant of J-PAKE, 33 * as defined in Chapter 7.4 of the Thread v1.0 Specification, 34 * available to members of the Thread Group http://threadgroup.org/ 35 * 36 * As the J-PAKE algorithm is inherently symmetric, so is our API. 37 * Each party needs to send its first round message, in any order, to the 38 * other party, then each sends its second round message, in any order. 39 * The payloads are serialized in a way suitable for use in TLS, but could 40 * also be use outside TLS. 41 */ 42 #include "mbedtls/build_info.h" 43 44 #include "mbedtls/ecp.h" 45 #include "mbedtls/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 * convention from the Thread v1.0 spec. Correspondence is indicated in the 69 * description as a pair C: client name, S: server name 70 */ 71 typedef struct mbedtls_ecjpake_context 72 { 73 mbedtls_md_type_t MBEDTLS_PRIVATE(md_type); /**< Hash to use */ 74 mbedtls_ecp_group MBEDTLS_PRIVATE(grp); /**< Elliptic curve */ 75 mbedtls_ecjpake_role MBEDTLS_PRIVATE(role); /**< Are we client or server? */ 76 int MBEDTLS_PRIVATE(point_format); /**< Format for point export */ 77 78 mbedtls_ecp_point MBEDTLS_PRIVATE(Xm1); /**< My public key 1 C: X1, S: X3 */ 79 mbedtls_ecp_point MBEDTLS_PRIVATE(Xm2); /**< My public key 2 C: X2, S: X4 */ 80 mbedtls_ecp_point MBEDTLS_PRIVATE(Xp1); /**< Peer public key 1 C: X3, S: X1 */ 81 mbedtls_ecp_point MBEDTLS_PRIVATE(Xp2); /**< Peer public key 2 C: X4, S: X2 */ 82 mbedtls_ecp_point MBEDTLS_PRIVATE(Xp); /**< Peer public key C: Xs, S: Xc */ 83 84 mbedtls_mpi MBEDTLS_PRIVATE(xm1); /**< My private key 1 C: x1, S: x3 */ 85 mbedtls_mpi MBEDTLS_PRIVATE(xm2); /**< My private key 2 C: x2, S: x4 */ 86 87 mbedtls_mpi MBEDTLS_PRIVATE(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 not empty 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 Set the point format for future reads and writes. 132 * 133 * \param ctx The ECJPAKE context to configure. 134 * \param point_format The point format to use: 135 * #MBEDTLS_ECP_PF_UNCOMPRESSED (default) 136 * or #MBEDTLS_ECP_PF_COMPRESSED. 137 * 138 * \return \c 0 if successful. 139 * \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if \p point_format 140 * is invalid. 141 */ 142 int mbedtls_ecjpake_set_point_format( mbedtls_ecjpake_context *ctx, 143 int point_format ); 144 145 /** 146 * \brief Check if an ECJPAKE context is ready for use. 147 * 148 * \param ctx The ECJPAKE context to check. This must be 149 * initialized. 150 * 151 * \return \c 0 if the context is ready for use. 152 * \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA otherwise. 153 */ 154 int mbedtls_ecjpake_check( const mbedtls_ecjpake_context *ctx ); 155 156 /** 157 * \brief Generate and write the first round message 158 * (TLS: contents of the Client/ServerHello extension, 159 * excluding extension type and length bytes). 160 * 161 * \param ctx The ECJPAKE context to use. This must be 162 * initialized and set up. 163 * \param buf The buffer to write the contents to. This must be a 164 * writable buffer of length \p len Bytes. 165 * \param len The length of \p buf in Bytes. 166 * \param olen The address at which to store the total number 167 * of Bytes written to \p buf. This must not be \c NULL. 168 * \param f_rng The RNG function to use. This must not be \c NULL. 169 * \param p_rng The RNG parameter to be passed to \p f_rng. This 170 * may be \c NULL if \p f_rng doesn't use a context. 171 * 172 * \return \c 0 if successful. 173 * \return A negative error code on failure. 174 */ 175 int mbedtls_ecjpake_write_round_one( mbedtls_ecjpake_context *ctx, 176 unsigned char *buf, size_t len, size_t *olen, 177 int (*f_rng)(void *, unsigned char *, size_t), 178 void *p_rng ); 179 180 /** 181 * \brief Read and process the first round message 182 * (TLS: contents of the Client/ServerHello extension, 183 * excluding extension type and length bytes). 184 * 185 * \param ctx The ECJPAKE context to use. This must be initialized 186 * and set up. 187 * \param buf The buffer holding the first round message. This must 188 * be a readable buffer of length \p len Bytes. 189 * \param len The length in Bytes of \p buf. 190 * 191 * \return \c 0 if successful. 192 * \return A negative error code on failure. 193 */ 194 int mbedtls_ecjpake_read_round_one( mbedtls_ecjpake_context *ctx, 195 const unsigned char *buf, 196 size_t len ); 197 198 /** 199 * \brief Generate and write the second round message 200 * (TLS: contents of the Client/ServerKeyExchange). 201 * 202 * \param ctx The ECJPAKE context to use. This must be initialized, 203 * set up, and already have performed round one. 204 * \param buf The buffer to write the round two contents to. 205 * This must be a writable buffer of length \p len Bytes. 206 * \param len The size of \p buf in Bytes. 207 * \param olen The address at which to store the total number of Bytes 208 * written to \p buf. This must not be \c NULL. 209 * \param f_rng The RNG function to use. This must not be \c NULL. 210 * \param p_rng The RNG parameter to be passed to \p f_rng. This 211 * may be \c NULL if \p f_rng doesn't use a context. 212 * 213 * \return \c 0 if successful. 214 * \return A negative error code on failure. 215 */ 216 int mbedtls_ecjpake_write_round_two( mbedtls_ecjpake_context *ctx, 217 unsigned char *buf, size_t len, size_t *olen, 218 int (*f_rng)(void *, unsigned char *, size_t), 219 void *p_rng ); 220 221 /** 222 * \brief Read and process the second round message 223 * (TLS: contents of the Client/ServerKeyExchange). 224 * 225 * \param ctx The ECJPAKE context to use. This must be initialized 226 * and set up and already have performed round one. 227 * \param buf The buffer holding the second round message. This must 228 * be a readable buffer of length \p len Bytes. 229 * \param len The length in Bytes of \p buf. 230 * 231 * \return \c 0 if successful. 232 * \return A negative error code on failure. 233 */ 234 int mbedtls_ecjpake_read_round_two( mbedtls_ecjpake_context *ctx, 235 const unsigned char *buf, 236 size_t len ); 237 238 /** 239 * \brief Derive the shared secret 240 * (TLS: Pre-Master Secret). 241 * 242 * \param ctx The ECJPAKE context to use. This must be initialized, 243 * set up and have performed both round one and two. 244 * \param buf The buffer to write the derived secret to. This must 245 * be a writable buffer of length \p len Bytes. 246 * \param len The length of \p buf in Bytes. 247 * \param olen The address at which to store the total number of Bytes 248 * written to \p buf. This must not be \c NULL. 249 * \param f_rng The RNG function to use. This must not be \c NULL. 250 * \param p_rng The RNG parameter to be passed to \p f_rng. This 251 * may be \c NULL if \p f_rng doesn't use a context. 252 * 253 * \return \c 0 if successful. 254 * \return A negative error code on failure. 255 */ 256 int mbedtls_ecjpake_derive_secret( mbedtls_ecjpake_context *ctx, 257 unsigned char *buf, size_t len, size_t *olen, 258 int (*f_rng)(void *, unsigned char *, size_t), 259 void *p_rng ); 260 261 /** 262 * \brief Write the shared key material to be passed to a Key 263 * Derivation Function as described in RFC8236. 264 * 265 * \param ctx The ECJPAKE context to use. This must be initialized, 266 * set up and have performed both round one and two. 267 * \param buf The buffer to write the derived secret to. This must 268 * be a writable buffer of length \p len Bytes. 269 * \param len The length of \p buf in Bytes. 270 * \param olen The address at which to store the total number of bytes 271 * written to \p buf. This must not be \c NULL. 272 * \param f_rng The RNG function to use. This must not be \c NULL. 273 * \param p_rng The RNG parameter to be passed to \p f_rng. This 274 * may be \c NULL if \p f_rng doesn't use a context. 275 * 276 * \return \c 0 if successful. 277 * \return A negative error code on failure. 278 */ 279 int mbedtls_ecjpake_write_shared_key( mbedtls_ecjpake_context *ctx, 280 unsigned char *buf, size_t len, size_t *olen, 281 int (*f_rng)(void *, unsigned char *, size_t), 282 void *p_rng ); 283 284 /** 285 * \brief This clears an ECJPAKE context and frees any 286 * embedded data structure. 287 * 288 * \param ctx The ECJPAKE context to free. This may be \c NULL, 289 * in which case this function does nothing. If it is not 290 * \c NULL, it must point to an initialized ECJPAKE context. 291 */ 292 void mbedtls_ecjpake_free( mbedtls_ecjpake_context *ctx ); 293 294 #if defined(MBEDTLS_SELF_TEST) 295 296 /** 297 * \brief Checkup routine 298 * 299 * \return 0 if successful, or 1 if a test failed 300 */ 301 int mbedtls_ecjpake_self_test( int verbose ); 302 303 #endif /* MBEDTLS_SELF_TEST */ 304 305 #ifdef __cplusplus 306 } 307 #endif 308 309 310 #endif /* ecjpake.h */ 311
