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More CTR_DRBG documentation improvements and clarifications

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This commit is contained in:
Gilles Peskine 2019-09-30 15:01:02 +02:00
parent 6fdf0b3a47
commit ec51dd12fa
1 changed files with 23 additions and 10 deletions
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33
include/mbedtls/ctr_drbg.h
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@ -1,7 +1,8 @@
/** /**
* \file ctr_drbg.h * \file ctr_drbg.h
* *
* \brief This file contains CTR_DRBG definitions and functions. * \brief This file contains definitions and functions for the
* CTR_DRBG pseudorandom generator.
* *
* CTR_DRBG is a standardized way of building a PRNG from a block-cipher * CTR_DRBG is a standardized way of building a PRNG from a block-cipher
* in counter mode operation, as defined in <em>NIST SP 800-90A: * in counter mode operation, as defined in <em>NIST SP 800-90A:
@ -200,6 +201,9 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
* with mbedtls_entropy_init() (which registers the platform's default * with mbedtls_entropy_init() (which registers the platform's default
* entropy sources). * entropy sources).
* *
* \p f_entropy is always called with a buffer size equal to the entropy
* length described in the documentation of mbedtls_ctr_drbg_set_entropy_len().
*
* Personalization data can be provided in addition to the more generic * Personalization data can be provided in addition to the more generic
* entropy source, to make this instantiation as unique as possible. * entropy source, to make this instantiation as unique as possible.
* *
@ -227,7 +231,7 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
* \param f_entropy The entropy callback, taking as arguments the * \param f_entropy The entropy callback, taking as arguments the
* \p p_entropy context, the buffer to fill, and the * \p p_entropy context, the buffer to fill, and the
* length of the buffer. * length of the buffer.
* \param p_entropy The entropy context. * \param p_entropy The entropy context to pass to \p f_entropy.
* \param custom Personalization data, that is device-specific * \param custom Personalization data, that is device-specific
* identifiers. This can be NULL, in which case the * identifiers. This can be NULL, in which case the
* personalization data is empty regardless of the value * personalization data is empty regardless of the value
@ -258,7 +262,8 @@ void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx );
* The default value is off. * The default value is off.
* *
* \note If enabled, entropy is gathered at the beginning of * \note If enabled, entropy is gathered at the beginning of
* every call to mbedtls_ctr_drbg_random_with_add(). * every call to mbedtls_ctr_drbg_random_with_add()
* or mbedtls_ctr_drbg_random().
* Only use this if your entropy source has sufficient * Only use this if your entropy source has sufficient
* throughput. * throughput.
* *
@ -270,8 +275,9 @@ void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
/** /**
* \brief This function sets the amount of entropy grabbed on each * \brief This function sets the amount of entropy grabbed on each
* seed or reseed. The default value is * seed or reseed.
* #MBEDTLS_CTR_DRBG_ENTROPY_LEN. *
* The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
* *
* \note For compliance with NIST SP 800-90A, the entropy length * \note For compliance with NIST SP 800-90A, the entropy length
* (\p len bytes = \p len * 8 bits) * (\p len bytes = \p len * 8 bits)
@ -308,7 +314,12 @@ void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx,
/** /**
* \brief This function sets the reseed interval. * \brief This function sets the reseed interval.
* The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL. *
* The reseed interval is the number of calls to mbedtls_ctr_drbg_random()
* or mbedtls_ctr_drbg_random_with_add() after which the entropy function
* is called again.
*
* The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
* *
* \param ctx The CTR_DRBG context. * \param ctx The CTR_DRBG context.
* \param interval The reseed interval. * \param interval The reseed interval.
@ -362,7 +373,7 @@ int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
* \param p_rng The CTR_DRBG context. This must be a pointer to a * \param p_rng The CTR_DRBG context. This must be a pointer to a
* #mbedtls_ctr_drbg_context structure. * #mbedtls_ctr_drbg_context structure.
* \param output The buffer to fill. * \param output The buffer to fill.
* \param output_len The length of the buffer. * \param output_len The length of the buffer in bytes.
* \param additional Additional data to update. Can be NULL, in which * \param additional Additional data to update. Can be NULL, in which
* case the additional data is empty regardless of * case the additional data is empty regardless of
* the value of \p add_len. * the value of \p add_len.
@ -437,7 +448,7 @@ MBEDTLS_DEPRECATED void mbedtls_ctr_drbg_update(
* *
* \return \c 0 on success. * \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on reseed
* failure. * failure.
*/ */
int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path ); int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
@ -451,8 +462,10 @@ int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char
* *
* \return \c 0 on success. * \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
* #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure. * reseed failure.
* \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if the existing
* seed file is too large.
*/ */
int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path ); int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
#endif /* MBEDTLS_FS_IO */ #endif /* MBEDTLS_FS_IO */