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Document parameter preconditions in DHM module

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This commit is contained in:
Hanno Becker 2018-12-12 19:38:01 +00:00
parent af0c6cb9e0
commit 6c5c45f400
1 changed files with 97 additions and 61 deletions
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158
include/mbedtls/dhm.h
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@ -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 */