diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h index 8e2d0208d..6af7a8ff4 100644 --- a/include/mbedtls/dhm.h +++ b/include/mbedtls/dhm.h @@ -127,9 +127,15 @@ mbedtls_dhm_context; void mbedtls_dhm_init( mbedtls_dhm_context *ctx ); /** - * \brief This function parses the ServerKeyExchange parameters. + * \brief This function parses the DHM parameters in a + * TLS ServerKeyExchange handshake message + * (DHM modulus, generator, and public key). * - * \param ctx The DHM context. + * \note In a TLS handshake, this is the how the client + * sets up its DHM context from the server's public + * DHM key material. + * + * \param ctx The DHM context to use. This must be initialized. * \param p On input, *p must be the start of the input buffer. * On output, *p is updated to point to the end of the data * that has been read. On success, this is the first byte @@ -143,31 +149,37 @@ void mbedtls_dhm_init( mbedtls_dhm_context *ctx ); * \return An \c MBEDTLS_ERR_DHM_XXX error code on failure. */ int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx, - unsigned char **p, - const unsigned char *end ); + unsigned char **p, + const unsigned char *end ); /** - * \brief This function sets up and writes the ServerKeyExchange - * parameters. + * \brief This function generates a DHM key pair and exports its + * public part together with the DHM parameters in the format + * used in a TLS ServerKeyExchange handshake message. * - * \note The destination buffer must be large enough to hold - * the reduced binary presentation of the modulus, the generator - * and the public key, each wrapped with a 2-byte length field. - * It is the responsibility of the caller to ensure that enough - * space is available. Refer to \c mbedtls_mpi_size to computing - * the byte-size of an MPI. - * - * \note This function assumes that \c ctx->P and \c ctx->G - * have already been properly set. For that, use + * \note This function assumes that the DHM parameters \c ctx->P + * and \c ctx->G have already been properly set. For that, use * mbedtls_dhm_set_group() below in conjunction with * mbedtls_mpi_read_binary() and mbedtls_mpi_read_string(). * - * \param ctx The DHM context. + * \note In a TLS handshake, this is the how the server generates + * and exports its DHM key material. + * + * \param ctx The DHM context to use. This must be initialized + * and have the DHM parameters set. It may or may not + * already have imported the peer's public key. * \param x_size The private key size in Bytes. - * \param olen The number of characters written. - * \param output The destination buffer. - * \param f_rng The RNG function. - * \param p_rng The RNG context. + * \param olen The address at which to store the number of Bytes + * written on success. This must not be \c NULL. + * \param output The destination buffer. This must be a writable buffer of + * sufficient size to hold the reduced binary presentation of + * the modulus, the generator and the public key, each wrapped + * with a 2-byte length field. It is the responsibility of the + * caller to ensure that enough space is available. Refer to + * mbedtls_mpi_size() to computing the byte-size of an MPI. + * \param f_rng The RNG function. 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 doesn't need a context parameter. * * \return \c 0 on success. * \return An \c MBEDTLS_ERR_DHM_XXX error code on failure. @@ -180,12 +192,14 @@ int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size, /** * \brief This function sets the prime modulus and generator. * - * \note This function can be used to set \p P, \p G + * \note This function can be used to set \c ctx->P, \c ctx->G * in preparation for mbedtls_dhm_make_params(). * - * \param ctx The DHM context. - * \param P The MPI holding the DHM prime modulus. - * \param G The MPI holding the DHM generator. + * \param ctx The DHM context to configure. This must be initialized. + * \param P The MPI holding the DHM prime modulus. This must be + * an initialized MPI. + * \param G The MPI holding the DHM generator. This must be an + * initialized MPI. * * \return \c 0 if successful. * \return An \c MBEDTLS_ERR_DHM_XXX error code on failure. @@ -195,11 +209,17 @@ int mbedtls_dhm_set_group( mbedtls_dhm_context *ctx, const mbedtls_mpi *G ); /** - * \brief This function imports the public value of the peer, G^Y. + * \brief This function imports the raw public value of the peer. * - * \param ctx The DHM context. - * \param input The input buffer containing the G^Y value of the peer. - * \param ilen The size of the input buffer. + * \note In a TLS handshake, this is the how the server imports + * the Client's public DHM key. + * + * \param ctx The DHM context to use. This must be initialized and have + * its DHM parameters set, e.g. via mbedtls_dhm_set_group(). + * It may or may not already have generated its own private key. + * \param input The input buffer containing the \c G^Y value of the peer. + * This must be a readable buffer of size \p ilen Bytes. + * \param ilen The size of the input buffer \p input in Bytes. * * \return \c 0 on success. * \return An \c MBEDTLS_ERR_DHM_XXX error code on failure. @@ -208,21 +228,25 @@ int mbedtls_dhm_read_public( mbedtls_dhm_context *ctx, const unsigned char *input, size_t ilen ); /** - * \brief This function creates its own private key, \c X, and - * exports \c G^X. + * \brief This function creates a DHM key pair and exports + * the raw public key in big-endian format. * * \note The destination buffer is always fully written * so as to contain a big-endian representation of G^X mod P. - * If it is larger than ctx->len, it is padded accordingly + * If it is larger than \c ctx->len, it is padded accordingly * with zero-bytes at the beginning. * - * \param ctx The DHM context. + * \param ctx The DHM context to use. This must be initialized and + * have the DHM parameters set. It may or may not already + * have imported the peer's public key. * \param x_size The private key size in Bytes. - * \param output The destination buffer. - * \param olen The length of the destination buffer. Must be at least - * equal to ctx->len (the size of \c P). - * \param f_rng The RNG function. - * \param p_rng The RNG context. + * \param output The destination buffer. This must be a writable buffer of + * size \p olen Bytes. + * \param olen The length of the destination buffer. This must be at least + * equal to `ctx->len` (the size of \c P). + * \param f_rng The RNG function. 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 doesn't need a context argument. * * \return \c 0 on success. * \return An \c MBEDTLS_ERR_DHM_XXX error code on failure. @@ -233,22 +257,27 @@ int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size, void *p_rng ); /** - * \brief This function derives and exports the shared secret - * \c (G^Y)^X mod \c P. + * \brief This function derives and exports the shared secret + * \c (G^Y)^X mod \c P. * - * \note If \p f_rng is not NULL, it is used to blind the input as - * a countermeasure against timing attacks. Blinding is used - * only if our private key \c X is re-used, and not used - * otherwise. We recommend always passing a non-NULL - * \p f_rng argument. + * \note If \p f_rng is not \c NULL, it is used to blind the input as + * a countermeasure against timing attacks. Blinding is used + * only if our private key \c X is re-used, and not used + * otherwise. We recommend always passing a non-NULL + * \p f_rng argument. * - * \param ctx The DHM context. - * \param output The destination buffer. - * \param output_size The size of the destination buffer. Must be at least - * the size of ctx->len (the size of \c P). + * \param ctx The DHM context to use. This must be initialized + * and have its own private key generated and the peer's + * public key imported. + * \param output The buffer to write the generated shared key to. This + * must be a writable buffer of size \p output_size Bytes. + * \param output_size The size of the destination buffer. This must be at + * least the size of \c ctx->len (the size of \c P). * \param olen On exit, holds the actual number of Bytes written. - * \param f_rng The RNG function, for blinding purposes. - * \param p_rng The RNG context. + * \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 An \c MBEDTLS_ERR_DHM_XXX error code on failure. @@ -259,9 +288,12 @@ int mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx, void *p_rng ); /** - * \brief This function frees and clears the components of a DHM context. + * \brief This function frees and clears the components + * of a DHM context. * - * \param ctx The DHM context to free and clear. + * \param ctx The DHM context to free and clear. This may be \c NULL, + * in which case this function is a no-op. If it is not \c NULL, + * it must point to an initialized DHM context. */ void mbedtls_dhm_free( mbedtls_dhm_context *ctx ); @@ -270,17 +302,19 @@ void mbedtls_dhm_free( mbedtls_dhm_context *ctx ); /** * \brief This function parses DHM parameters in PEM or DER format. * - * \param dhm The DHM context to initialize. - * \param dhmin The input buffer. - * \param dhminlen The size of the buffer, including the terminating null - * Byte for PEM data. + * \param dhm The DHM context to import the DHM parameters into. + * This must be initialized. + * \param dhmin The input buffer. This must be a readable buffer of + * length \p dhminlen Bytes. + * \param dhminlen The size of the input buffer \p dhmin, including the + * terminating \c NULL Byte for PEM data. * * \return \c 0 on success. - * \return An \c MBEDTLS_ERR_DHM_XXX or \c MBEDTLS_ERR_PEM_XXX error code - * error code on failure. + * \return An \c MBEDTLS_ERR_DHM_XXX or \c MBEDTLS_ERR_PEM_XXX error + * code on failure. */ int mbedtls_dhm_parse_dhm( mbedtls_dhm_context *dhm, const unsigned char *dhmin, - size_t dhminlen ); + size_t dhminlen ); #if defined(MBEDTLS_FS_IO) /** \ingroup x509_module */ @@ -288,11 +322,13 @@ int mbedtls_dhm_parse_dhm( mbedtls_dhm_context *dhm, const unsigned char *dhmin, * \brief This function loads and parses DHM parameters from a file. * * \param dhm The DHM context to load the parameters to. + * This must be initialized. * \param path The filename to read the DHM parameters from. + * This must not be \c NULL. * * \return \c 0 on success. - * \return An \c MBEDTLS_ERR_DHM_XXX or \c MBEDTLS_ERR_PEM_XXX error code - * error code on failure. + * \return An \c MBEDTLS_ERR_DHM_XXX or \c MBEDTLS_ERR_PEM_XXX + * error code on failure. */ int mbedtls_dhm_parse_dhmfile( mbedtls_dhm_context *dhm, const char *path ); #endif /* MBEDTLS_FS_IO */