diff options
Diffstat (limited to 'include/mbedtls/ecdh.h')
| -rw-r--r-- | include/mbedtls/ecdh.h | 441 |
1 files changed, 441 insertions, 0 deletions
diff --git a/include/mbedtls/ecdh.h b/include/mbedtls/ecdh.h new file mode 100644 index 0000000..792db79 --- /dev/null +++ b/include/mbedtls/ecdh.h @@ -0,0 +1,441 @@ +/** + * \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 OR GPL-2.0-or-later + */ + +#ifndef MBEDTLS_ECDH_H +#define MBEDTLS_ECDH_H +#include "mbedtls/private_access.h" + +#include "mbedtls/build_info.h" + +#include "mbedtls/ecp.h" + +/* + * Mbed TLS supports two formats for ECDH contexts (#mbedtls_ecdh_context + * defined in `ecdh.h`). For most applications, the choice of format makes + * no difference, since all library functions can work with either format, + * except that the new format is incompatible with MBEDTLS_ECP_RESTARTABLE. + + * The new format used when this option is disabled is smaller + * (56 bytes on a 32-bit platform). In future versions of the library, it + * will support alternative implementations of ECDH operations. + * The new format is incompatible with applications that access + * context fields directly and with restartable ECP operations. + */ + +#if defined(MBEDTLS_ECP_RESTARTABLE) +#define MBEDTLS_ECDH_LEGACY_CONTEXT +#else +#undef MBEDTLS_ECDH_LEGACY_CONTEXT +#endif + +#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 MBEDTLS_PRIVATE(grp); /*!< The elliptic curve used. */ + mbedtls_mpi MBEDTLS_PRIVATE(d); /*!< The private key. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Q); /*!< The public key. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Qp); /*!< The value of the public key of the peer. */ + mbedtls_mpi MBEDTLS_PRIVATE(z); /*!< The shared secret. */ +#if defined(MBEDTLS_ECP_RESTARTABLE) + mbedtls_ecp_restart_ctx MBEDTLS_PRIVATE(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 MBEDTLS_PRIVATE(grp); /*!< The elliptic curve used. */ + mbedtls_mpi MBEDTLS_PRIVATE(d); /*!< The private key. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Q); /*!< The public key. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Qp); /*!< The value of the public key of the peer. */ + mbedtls_mpi MBEDTLS_PRIVATE(z); /*!< The shared secret. */ + int MBEDTLS_PRIVATE(point_format); /*!< The format of point export in TLS messages. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Vi); /*!< The blinding value. */ + mbedtls_ecp_point MBEDTLS_PRIVATE(Vf); /*!< The unblinding value. */ + mbedtls_mpi MBEDTLS_PRIVATE(_d); /*!< The previous \p d. */ +#if defined(MBEDTLS_ECP_RESTARTABLE) + int MBEDTLS_PRIVATE(restart_enabled); /*!< The flag for restartable mode. */ + mbedtls_ecp_restart_ctx MBEDTLS_PRIVATE(rs); /*!< The restart context for EC computations. */ +#endif /* MBEDTLS_ECP_RESTARTABLE */ +#else + uint8_t MBEDTLS_PRIVATE(point_format); /*!< The format of point export in TLS messages + as defined in RFC 4492. */ + mbedtls_ecp_group_id MBEDTLS_PRIVATE(grp_id);/*!< The elliptic curve used. */ + mbedtls_ecdh_variant MBEDTLS_PRIVATE(var); /*!< The ECDH implementation/structure used. */ + union { + mbedtls_ecdh_context_mbed MBEDTLS_PRIVATE(mbed_ecdh); +#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED) + mbedtls_ecdh_context_everest MBEDTLS_PRIVATE(everest_ecdh); +#endif + } MBEDTLS_PRIVATE(ctx); /*!< Implementation-specific context. The + context in use is specified by the \c var + field. */ +#if defined(MBEDTLS_ECP_RESTARTABLE) + uint8_t MBEDTLS_PRIVATE(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 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 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 to use. This must not be \c NULL. + * \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 */ |