Diff: include/mbedtls/ecjpake.h

Revision:

0:cdf462088d13

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+++ b/include/mbedtls/ecjpake.h	Thu Jan 05 00:18:44 2017 +0000
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+/**
+ * \file ecjpake.h
+ *
+ * \brief Elliptic curve J-PAKE
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+#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.
+ */
+
+#include "ecp.h"
+#include "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;
+
+/**
+ * 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
+{
+    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;
+
+/**
+ * \brief           Initialize a context
+ *                  (just makes it ready for setup() or free()).
+ *
+ * \param ctx       context to initialize
+ */
+void mbedtls_ecjpake_init( mbedtls_ecjpake_context *ctx );
+
+/**
+ * \brief           Set up a 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       context to set up
+ * \param role      Our role: client or server
+ * \param hash      hash function to use (MBEDTLS_MD_XXX)
+ * \param curve     elliptic curve identifier (MBEDTLS_ECP_DP_XXX)
+ * \param secret    pre-shared secret (passphrase)
+ * \param len       length of the shared secret
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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 a context is ready for use
+ *
+ * \param ctx       Context to check
+ *
+ * \return          0 if the context is ready for use,
+ *                  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       Context to use
+ * \param buf       Buffer to write the contents to
+ * \param len       Buffer size
+ * \param olen      Will be updated with the number of bytes written
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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       Context to use
+ * \param buf       Pointer to extension contents
+ * \param len       Extension length
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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       Context to use
+ * \param buf       Buffer to write the contents to
+ * \param len       Buffer size
+ * \param olen      Will be updated with the number of bytes written
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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       Context to use
+ * \param buf       Pointer to the message
+ * \param len       Message length
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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       Context to use
+ * \param buf       Buffer to write the contents to
+ * \param len       Buffer size
+ * \param olen      Will be updated with the number of bytes written
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successfull,
+ *                  a negative error code otherwise
+ */
+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           Free a context's content
+ *
+ * \param ctx       context to free
+ */
+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
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ecjpake.h */