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- /**
- * \file ecdh.h
- *
- * \brief This file contains ECDH definitions and functions.
- *
- * The Elliptic Curve Diffie-Hellman (ECDH) protocol is an anonymous
- * key agreement protocol allowing two parties to establish a shared
- * secret over an insecure channel. Each party must have an
- * elliptic-curve public–private key pair.
- *
- * For more information, see <em>NIST SP 800-56A Rev. 2: Recommendation for
- * Pair-Wise Key Establishment Schemes Using Discrete Logarithm
- * Cryptography</em>.
- */
- /*
- * 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_ECDH_H
- #define MBEDTLS_ECDH_H
- #if !defined(MBEDTLS_CONFIG_FILE)
- #include "mbedtls/config.h"
- #else
- #include MBEDTLS_CONFIG_FILE
- #endif
- #include "mbedtls/ecp.h"
- #if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
- #undef MBEDTLS_ECDH_LEGACY_CONTEXT
- #include "everest/everest.h"
- #endif
- #ifdef __cplusplus
- extern "C" {
- #endif
- /**
- * Defines the source of the imported EC key.
- */
- typedef enum
- {
- MBEDTLS_ECDH_OURS, /**< Our key. */
- MBEDTLS_ECDH_THEIRS, /**< The key of the peer. */
- } mbedtls_ecdh_side;
- #if !defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
- /**
- * Defines the ECDH implementation used.
- *
- * Later versions of the library may add new variants, therefore users should
- * not make any assumptions about them.
- */
- typedef enum
- {
- MBEDTLS_ECDH_VARIANT_NONE = 0, /*!< Implementation not defined. */
- MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0,/*!< The default Mbed TLS implementation */
- #if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
- MBEDTLS_ECDH_VARIANT_EVEREST /*!< Everest implementation */
- #endif
- } mbedtls_ecdh_variant;
- /**
- * The context used by the default ECDH implementation.
- *
- * Later versions might change the structure of this context, therefore users
- * should not make any assumptions about the structure of
- * mbedtls_ecdh_context_mbed.
- */
- typedef struct mbedtls_ecdh_context_mbed
- {
- mbedtls_ecp_group grp; /*!< The elliptic curve used. */
- mbedtls_mpi d; /*!< The private key. */
- mbedtls_ecp_point Q; /*!< The public key. */
- mbedtls_ecp_point Qp; /*!< The value of the public key of the peer. */
- mbedtls_mpi z; /*!< The shared secret. */
- #if defined(MBEDTLS_ECP_RESTARTABLE)
- mbedtls_ecp_restart_ctx rs; /*!< The restart context for EC computations. */
- #endif
- } mbedtls_ecdh_context_mbed;
- #endif
- /**
- *
- * \warning Performing multiple operations concurrently on the same
- * ECDSA context is not supported; objects of this type
- * should not be shared between multiple threads.
- * \brief The ECDH context structure.
- */
- typedef struct mbedtls_ecdh_context
- {
- #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
- mbedtls_ecp_group grp; /*!< The elliptic curve used. */
- mbedtls_mpi d; /*!< The private key. */
- mbedtls_ecp_point Q; /*!< The public key. */
- mbedtls_ecp_point Qp; /*!< The value of the public key of the peer. */
- mbedtls_mpi z; /*!< The shared secret. */
- int point_format; /*!< The format of point export in TLS messages. */
- mbedtls_ecp_point Vi; /*!< The blinding value. */
- mbedtls_ecp_point Vf; /*!< The unblinding value. */
- mbedtls_mpi _d; /*!< The previous \p d. */
- #if defined(MBEDTLS_ECP_RESTARTABLE)
- int restart_enabled; /*!< The flag for restartable mode. */
- mbedtls_ecp_restart_ctx rs; /*!< The restart context for EC computations. */
- #endif /* MBEDTLS_ECP_RESTARTABLE */
- #else
- uint8_t point_format; /*!< The format of point export in TLS messages
- as defined in RFC 4492. */
- mbedtls_ecp_group_id grp_id;/*!< The elliptic curve used. */
- mbedtls_ecdh_variant var; /*!< The ECDH implementation/structure used. */
- union
- {
- mbedtls_ecdh_context_mbed mbed_ecdh;
- #if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
- mbedtls_ecdh_context_everest everest_ecdh;
- #endif
- } ctx; /*!< Implementation-specific context. The
- context in use is specified by the \c var
- field. */
- #if defined(MBEDTLS_ECP_RESTARTABLE)
- uint8_t restart_enabled; /*!< The flag for restartable mode. Functions of
- an alternative implementation not supporting
- restartable mode must return
- MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED error
- if this flag is set. */
- #endif /* MBEDTLS_ECP_RESTARTABLE */
- #endif /* MBEDTLS_ECDH_LEGACY_CONTEXT */
- }
- mbedtls_ecdh_context;
- /**
- * \brief Check whether a given group can be used for ECDH.
- *
- * \param gid The ECP group ID to check.
- *
- * \return \c 1 if the group can be used, \c 0 otherwise
- */
- int mbedtls_ecdh_can_do( mbedtls_ecp_group_id gid );
- /**
- * \brief This function generates an ECDH keypair on an elliptic
- * curve.
- *
- * This function performs the first of two core computations
- * implemented during the ECDH key exchange. The second core
- * computation is performed by mbedtls_ecdh_compute_shared().
- *
- * \see ecp.h
- *
- * \param grp The ECP group to use. This must be initialized and have
- * domain parameters loaded, for example through
- * mbedtls_ecp_load() or mbedtls_ecp_tls_read_group().
- * \param d The destination MPI (private key).
- * This must be initialized.
- * \param Q The destination point (public key).
- * This must be initialized.
- * \param f_rng The RNG function to use. This must not be \c NULL.
- * \param p_rng The RNG context to be passed to \p f_rng. This may be
- * \c NULL in case \p f_rng doesn't need a context argument.
- *
- * \return \c 0 on success.
- * \return Another \c MBEDTLS_ERR_ECP_XXX or
- * \c MBEDTLS_MPI_XXX error code on failure.
- */
- int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
- int (*f_rng)(void *, unsigned char *, size_t),
- void *p_rng );
- /**
- * \brief This function computes the shared secret.
- *
- * This function performs the second of two core computations
- * implemented during the ECDH key exchange. The first core
- * computation is performed by mbedtls_ecdh_gen_public().
- *
- * \see ecp.h
- *
- * \note If \p f_rng is not NULL, it is used to implement
- * countermeasures against side-channel attacks.
- * For more information, see mbedtls_ecp_mul().
- *
- * \param grp The ECP group to use. This must be initialized and have
- * domain parameters loaded, for example through
- * mbedtls_ecp_load() or mbedtls_ecp_tls_read_group().
- * \param z The destination MPI (shared secret).
- * This must be initialized.
- * \param Q The public key from another party.
- * This must be initialized.
- * \param d Our secret exponent (private key).
- * This must be initialized.
- * \param f_rng The RNG function. This may be \c NULL if randomization
- * of intermediate results during the ECP computations is
- * not needed (discouraged). See the documentation of
- * mbedtls_ecp_mul() for more.
- * \param p_rng The RNG context to be passed to \p f_rng. This may be
- * \c NULL if \p f_rng is \c NULL or doesn't need a
- * context argument.
- *
- * \return \c 0 on success.
- * \return Another \c MBEDTLS_ERR_ECP_XXX or
- * \c MBEDTLS_MPI_XXX error code on failure.
- */
- int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
- const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
- int (*f_rng)(void *, unsigned char *, size_t),
- void *p_rng );
- /**
- * \brief This function initializes an ECDH context.
- *
- * \param ctx The ECDH context to initialize. This must not be \c NULL.
- */
- void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx );
- /**
- * \brief This function sets up the ECDH context with the information
- * given.
- *
- * This function should be called after mbedtls_ecdh_init() but
- * before mbedtls_ecdh_make_params(). There is no need to call
- * this function before mbedtls_ecdh_read_params().
- *
- * This is the first function used by a TLS server for ECDHE
- * ciphersuites.
- *
- * \param ctx The ECDH context to set up. This must be initialized.
- * \param grp_id The group id of the group to set up the context for.
- *
- * \return \c 0 on success.
- */
- int mbedtls_ecdh_setup( mbedtls_ecdh_context *ctx,
- mbedtls_ecp_group_id grp_id );
- /**
- * \brief This function frees a context.
- *
- * \param ctx The 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 ECDH context.
- */
- void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx );
- /**
- * \brief This function generates an EC key pair and exports its
- * in the format used in a TLS ServerKeyExchange handshake
- * message.
- *
- * This is the second function used by a TLS server for ECDHE
- * ciphersuites. (It is called after mbedtls_ecdh_setup().)
- *
- * \see ecp.h
- *
- * \param ctx The ECDH context to use. This must be initialized
- * and bound to a group, for example via mbedtls_ecdh_setup().
- * \param olen The address at which to store the number of Bytes written.
- * \param buf The destination buffer. This must be a writable buffer of
- * length \p blen Bytes.
- * \param blen The length of the destination buffer \p buf in Bytes.
- * \param f_rng The RNG function to use. This must not be \c NULL.
- * \param p_rng The RNG context to be passed to \p f_rng. This may be
- * \c NULL in case \p f_rng doesn't need a context argument.
- *
- * \return \c 0 on success.
- * \return #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
- * operations was reached: see \c mbedtls_ecp_set_max_ops().
- * \return Another \c MBEDTLS_ERR_ECP_XXX error code on failure.
- */
- int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
- unsigned char *buf, size_t blen,
- int (*f_rng)(void *, unsigned char *, size_t),
- void *p_rng );
- /**
- * \brief This function parses the ECDHE parameters in a
- * TLS ServerKeyExchange handshake message.
- *
- * \note In a TLS handshake, this is the how the client
- * sets up its ECDHE context from the server's public
- * ECDHE key material.
- *
- * \see ecp.h
- *
- * \param ctx The ECDHE context to use. This must be initialized.
- * \param buf On input, \c *buf must be the start of the input buffer.
- * On output, \c *buf is updated to point to the end of the
- * data that has been read. On success, this is the first byte
- * past the end of the ServerKeyExchange parameters.
- * On error, this is the point at which an error has been
- * detected, which is usually not useful except to debug
- * failures.
- * \param end The end of the input buffer.
- *
- * \return \c 0 on success.
- * \return An \c MBEDTLS_ERR_ECP_XXX error code on failure.
- *
- */
- int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
- const unsigned char **buf,
- const unsigned char *end );
- /**
- * \brief This function sets up an ECDH context from an EC key.
- *
- * It is used by clients and servers in place of the
- * ServerKeyEchange for static ECDH, and imports ECDH
- * parameters from the EC key information of a certificate.
- *
- * \see ecp.h
- *
- * \param ctx The ECDH context to set up. This must be initialized.
- * \param key The EC key to use. This must be initialized.
- * \param side Defines the source of the key. Possible values are:
- * - #MBEDTLS_ECDH_OURS: The key is ours.
- * - #MBEDTLS_ECDH_THEIRS: The key is that of the peer.
- *
- * \return \c 0 on success.
- * \return Another \c MBEDTLS_ERR_ECP_XXX error code on failure.
- *
- */
- int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx,
- const mbedtls_ecp_keypair *key,
- mbedtls_ecdh_side side );
- /**
- * \brief This function generates a public key and exports it
- * as a TLS ClientKeyExchange payload.
- *
- * This is the second function used by a TLS client for ECDH(E)
- * ciphersuites.
- *
- * \see ecp.h
- *
- * \param ctx The ECDH context to use. This must be initialized
- * and bound to a group, the latter usually by
- * mbedtls_ecdh_read_params().
- * \param olen The address at which to store the number of Bytes written.
- * This must not be \c NULL.
- * \param buf The destination buffer. This must be a writable buffer
- * of length \p blen Bytes.
- * \param blen The size of the destination buffer \p buf in Bytes.
- * \param f_rng The RNG function to use. This must not be \c NULL.
- * \param p_rng The RNG context to be passed to \p f_rng. This may be
- * \c NULL in case \p f_rng doesn't need a context argument.
- *
- * \return \c 0 on success.
- * \return #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
- * operations was reached: see \c mbedtls_ecp_set_max_ops().
- * \return Another \c MBEDTLS_ERR_ECP_XXX error code on failure.
- */
- int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
- unsigned char *buf, size_t blen,
- int (*f_rng)(void *, unsigned char *, size_t),
- void *p_rng );
- /**
- * \brief This function parses and processes the ECDHE payload of a
- * TLS ClientKeyExchange message.
- *
- * This is the third function used by a TLS server for ECDH(E)
- * ciphersuites. (It is called after mbedtls_ecdh_setup() and
- * mbedtls_ecdh_make_params().)
- *
- * \see ecp.h
- *
- * \param ctx The ECDH context to use. This must be initialized
- * and bound to a group, for example via mbedtls_ecdh_setup().
- * \param buf The pointer to the ClientKeyExchange payload. This must
- * be a readable buffer of length \p blen Bytes.
- * \param blen The length of the input buffer \p buf in Bytes.
- *
- * \return \c 0 on success.
- * \return An \c MBEDTLS_ERR_ECP_XXX error code on failure.
- */
- int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
- const unsigned char *buf, size_t blen );
- /**
- * \brief This function derives and exports the shared secret.
- *
- * This is the last function used by both TLS client
- * and servers.
- *
- * \note If \p f_rng is not NULL, it is used to implement
- * countermeasures against side-channel attacks.
- * For more information, see mbedtls_ecp_mul().
- *
- * \see ecp.h
- * \param ctx The ECDH context to use. This must be initialized
- * and have its own private key generated and the peer's
- * public key imported.
- * \param olen The address at which to store the total number of
- * Bytes written on success. This must not be \c NULL.
- * \param buf The buffer to write the generated shared key to. This
- * must be a writable buffer of size \p blen Bytes.
- * \param blen The length of the destination buffer \p buf in Bytes.
- * \param f_rng The RNG function, for blinding purposes. This may
- * b \c NULL if blinding isn't needed.
- * \param p_rng The RNG context. This may be \c NULL if \p f_rng
- * doesn't need a context argument.
- *
- * \return \c 0 on success.
- * \return #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
- * operations was reached: see \c mbedtls_ecp_set_max_ops().
- * \return Another \c MBEDTLS_ERR_ECP_XXX error code on failure.
- */
- int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
- unsigned char *buf, size_t blen,
- int (*f_rng)(void *, unsigned char *, size_t),
- void *p_rng );
- #if defined(MBEDTLS_ECP_RESTARTABLE)
- /**
- * \brief This function enables restartable EC computations for this
- * context. (Default: disabled.)
- *
- * \see \c mbedtls_ecp_set_max_ops()
- *
- * \note It is not possible to safely disable restartable
- * computations once enabled, except by free-ing the context,
- * which cancels possible in-progress operations.
- *
- * \param ctx The ECDH context to use. This must be initialized.
- */
- void mbedtls_ecdh_enable_restart( mbedtls_ecdh_context *ctx );
- #endif /* MBEDTLS_ECP_RESTARTABLE */
- #ifdef __cplusplus
- }
- #endif
- #endif /* ecdh.h */
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