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HMAC_DRBG documentation improvements clarifications

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Improve the formatting and writing of the documentation based on what
had been done for CTR_DRBG.

Document the maximum size and nullability of some buffer parameters.
This commit is contained in:
Gilles Peskine 2019-09-30 15:01:15 +02:00
parent ec51dd12fa
commit 74efcd2b71
1 changed files with 158 additions and 100 deletions
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258
include/mbedtls/hmac_drbg.h
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@ -1,10 +1,14 @@
/** /**
* \file hmac_drbg.h * \file hmac_drbg.h
* *
* \brief HMAC_DRBG (NIST SP 800-90A) * \brief The HMAC_DRBG pseudorandom generator.
*
* This module implements the HMAC_DRBG pseudorandom generator described
* in <em>NIST SP 800-90A: Recommendation for Random Number Generation Using
* Deterministic Random Bit Generators</em>.
*/ */
/* /*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved * Copyright (C) 2006-2019, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0 * SPDX-License-Identifier: Apache-2.0
* *
* Licensed under the Apache License, Version 2.0 (the "License"); you may * Licensed under the Apache License, Version 2.0 (the "License"); you may
@ -104,38 +108,50 @@ typedef struct mbedtls_hmac_drbg_context
} mbedtls_hmac_drbg_context; } mbedtls_hmac_drbg_context;
/** /**
* \brief HMAC_DRBG context initialization * \brief HMAC_DRBG context initialization.
* Makes the context ready for mbedtls_hmac_drbg_seed(),
* mbedtls_hmac_drbg_seed_buf() or
* mbedtls_hmac_drbg_free().
* *
* \param ctx HMAC_DRBG context to be initialized * This function makes the context ready for mbedtls_hmac_drbg_seed(),
* mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free().
*
* \param ctx HMAC_DRBG context to be initialized.
*/ */
void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx ); void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
/** /**
* \brief HMAC_DRBG initial seeding * \brief HMAC_DRBG initial seeding.
* Seed and setup entropy source for future reseeds.
* *
* \param ctx HMAC_DRBG context to be seeded * Set the initial seed and set up the entropy source for future reseeds.
* \param md_info MD algorithm to use for HMAC_DRBG *
* \param f_entropy Entropy callback (p_entropy, buffer to fill, buffer * \param ctx HMAC_DRBG context to be seeded.
* length) * \param md_info MD algorithm to use for HMAC_DRBG.
* \param p_entropy Entropy context * \param f_entropy The entropy callback, taking as arguments the
* \param custom Personalization data (Device specific identifiers) * \p p_entropy context, the buffer to fill, and the
* (Can be NULL) * length of the buffer.
* \param len Length of personalization data * \param p_entropy The entropy context to pass to \p f_entropy.
* \param custom Personalization data, that is device-specific
* identifiers. This can be NULL, in which case the
* personalization data is empty regardless of the value
* of \p len.
* \param len The length of the personalization data.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
* and also at most
* #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len * 3 / 2
* where \p entropy_len is the entropy length
* (see mbedtls_hmac_drbg_set_entropy_len()).
* *
* \note The "security strength" as defined by NIST is set to: * \note The "security strength" as defined by NIST is set to:
* 128 bits if md_alg is SHA-1, * 128 bits if \p md_info is SHA-1,
* 192 bits if md_alg is SHA-224, * 192 bits if \p md_info is SHA-224,
* 256 bits if md_alg is SHA-256 or higher. * 256 bits if \p md_info is SHA-256, SHA-384 or SHA-512.
* Note that SHA-256 is just as efficient as SHA-224. * Note that SHA-256 is just as efficient as SHA-224.
* *
* \return 0 if successful, or * \return 0 if successful.
* MBEDTLS_ERR_MD_BAD_INPUT_DATA, or * \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
* MBEDTLS_ERR_MD_ALLOC_FAILED, or * invalid.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED. * \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
* memory to allocate context data.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if the call to \p f_entropy failed.
*/ */
int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
const mbedtls_md_info_t * md_info, const mbedtls_md_info_t * md_info,
@ -146,98 +162,131 @@ int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
/** /**
* \brief Initilisation of simpified HMAC_DRBG (never reseeds). * \brief Initilisation of simpified HMAC_DRBG (never reseeds).
* (For use with deterministic ECDSA.)
* *
* \param ctx HMAC_DRBG context to be initialised * This function is meant for use in algorithms that need a pseudorandom
* \param md_info MD algorithm to use for HMAC_DRBG * input such as deterministic ECDSA.
* \param data Concatenation of entropy string and additional data
* \param data_len Length of data in bytes
* *
* \return 0 if successful, or * \param ctx HMAC_DRBG context to be initialised.
* MBEDTLS_ERR_MD_BAD_INPUT_DATA, or * \param md_info MD algorithm to use for HMAC_DRBG.
* MBEDTLS_ERR_MD_ALLOC_FAILED. * \param data Concatenation of the initial entropy string and
* the additional data.
* \param data_len Length of \p data in bytes.
*
* \return 0 if successful. or
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
* invalid.
* \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
* memory to allocate context data.
*/ */
int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
const mbedtls_md_info_t * md_info, const mbedtls_md_info_t * md_info,
const unsigned char *data, size_t data_len ); const unsigned char *data, size_t data_len );
/** /**
* \brief Enable / disable prediction resistance (Default: Off) * \brief This function turns prediction resistance on or off.
* The default value is off.
* *
* Note: If enabled, entropy is used for ctx->entropy_len before each call! * \note If enabled, entropy is gathered at the beginning of
* Only use this if you have ample supply of good entropy! * every call to mbedtls_hmac_drbg_random_with_add()
* or mbedtls_hmac_drbg_random().
* Only use this if your entropy source has sufficient
* throughput.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param resistance MBEDTLS_HMAC_DRBG_PR_ON or MBEDTLS_HMAC_DRBG_PR_OFF * \param resistance #MBEDTLS_HMAC_DRBG_PR_ON or #MBEDTLS_HMAC_DRBG_PR_OFF.
*/ */
void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx, void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx,
int resistance ); int resistance );
/** /**
* \brief Set the amount of entropy grabbed on each reseed * \brief This function sets the amount of entropy grabbed on each
* (Default: given by the security strength, which * seed or reseed.
* depends on the hash used, see \c mbedtls_hmac_drbg_init() )
* *
* \param ctx HMAC_DRBG context * The default value is given by the security strength, which depends on the
* \param len Amount of entropy to grab, in bytes * hash used. See mbedtls_hmac_drbg_init().
*
* \param ctx The HMAC_DRBG context.
* \param len The amount of entropy to grab, in bytes.
*/ */
void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx, void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx,
size_t len ); size_t len );
/** /**
* \brief Set the reseed interval * \brief Set the reseed interval.
* (Default: MBEDTLS_HMAC_DRBG_RESEED_INTERVAL)
* *
* \param ctx HMAC_DRBG context * The reseed interval is the number of calls to mbedtls_hmac_drbg_random()
* \param interval Reseed interval * or mbedtls_hmac_drbg_random_with_add() after which the entropy function
* is called again.
*
* The default value is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL.
*
* \param ctx The HMAC_DRBG context.
* \param interval The reseed interval.
*/ */
void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx, void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx,
int interval ); int interval );
/** /**
* \brief HMAC_DRBG update state * \brief This function updates the state of the HMAC_DRBG context.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param additional Additional data to update state with, or NULL * \param additional The data to update the state with.
* \param add_len Length of additional data, or 0 * If this is \p NULL, there is no additional data.
* \param add_len Length of \p additional in bytes.
* Unused if \p additional is null.
* *
* \return \c 0 on success, or an error from the underlying * \return \c 0 on success, or an error from the underlying
* hash calculation. * hash calculation.
*
* \note Additional data is optional, pass NULL and 0 as second
* third argument if no additional data is being used.
*/ */
int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t add_len ); const unsigned char *additional, size_t add_len );
/** /**
* \brief HMAC_DRBG reseeding (extracts data from entropy source) * \brief This function reseeds the HMAC_DRBG context, that is
* extracts data from the entropy source.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param additional Additional data to add to state (Can be NULL) * \param additional Additional data to add to the state.
* \param len Length of additional data * If this is \c NULL, there is no additional data
* and \p len should be \c 0.
* \param len The length of the additional data.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
* and also at most
* #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len
* where \p entropy_len is the entropy length
* (see mbedtls_hmac_drbg_set_entropy_len()).
* *
* \return 0 if successful, or * \return 0 if successful.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if a call to the entropy function failed.
*/ */
int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t len ); const unsigned char *additional, size_t len );
/** /**
* \brief HMAC_DRBG generate random with additional update input * \brief This function updates an HMAC_DRBG instance with additional
* data and uses it to generate random data.
* *
* Note: Automatically reseeds if reseed_counter is reached or PR is enabled. * \note The function automatically reseeds if the reseed counter is exceeded.
* *
* \param p_rng HMAC_DRBG context * \param p_rng The HMAC_DRBG context. This must be a pointer to a
* \param output Buffer to fill * #mbedtls_hmac_drbg_context structure.
* \param output_len Length of the buffer * \param output The buffer to fill.
* \param additional Additional data to update with (can be NULL) * \param output_len The length of the buffer in bytes.
* \param add_len Length of additional data (can be 0) * This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
* \param additional Additional data to update with.
* If this is \p NULL, there is no additional data
* and \p add_len should be \c 0.
* \param add_len The length of the additional data.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT.
* *
* \return 0 if successful, or * \return \c 0 if successful.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG, or * if a call to the entropy source failed.
* MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG. * \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
* \p output_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
* \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if
* \p add_len > #MBEDTLS_HMAC_DRBG_MAX_INPUT.
*/ */
int mbedtls_hmac_drbg_random_with_add( void *p_rng, int mbedtls_hmac_drbg_random_with_add( void *p_rng,
unsigned char *output, size_t output_len, unsigned char *output, size_t output_len,
@ -245,24 +294,28 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng,
size_t add_len ); size_t add_len );
/** /**
* \brief HMAC_DRBG generate random * \brief This function uses HMAC_DRBG to generate random data.
* *
* Note: Automatically reseeds if reseed_counter is reached or PR is enabled. * \note The function automatically reseeds if the reseed counter is exceeded.
* *
* \param p_rng HMAC_DRBG context * \param p_rng The HMAC_DRBG context. This must be a pointer to a
* \param output Buffer to fill * #mbedtls_hmac_drbg_context structure.
* \param out_len Length of the buffer * \param output The buffer to fill.
* \param out_len The length of the buffer in bytes.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
* *
* \return 0 if successful, or * \return \c 0 if successful.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG * if a call to the entropy source failed.
* \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
* \p out_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
*/ */
int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len ); int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
/** /**
* \brief Free an HMAC_DRBG context * \brief Free an HMAC_DRBG context
* *
* \param ctx HMAC_DRBG context to free. * \param ctx The HMAC_DRBG context to free.
*/ */
void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx ); void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
@ -273,17 +326,16 @@ void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
#define MBEDTLS_DEPRECATED #define MBEDTLS_DEPRECATED
#endif #endif
/** /**
* \brief HMAC_DRBG update state * \brief This function updates the state of the HMAC_DRBG context.
* *
* \deprecated Superseded by mbedtls_hmac_drbg_update_ret() * \deprecated Superseded by mbedtls_hmac_drbg_update_ret()
* in 2.16.0. * in 2.16.0.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param additional Additional data to update state with, or NULL * \param additional The data to update the state with.
* \param add_len Length of additional data, or 0 * If this is \p NULL, there is no additional data.
* * \param add_len Length of \p additional in bytes.
* \note Additional data is optional, pass NULL and 0 as second * Unused if \p additional is null.
* third argument if no additional data is being used.
*/ */
MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update( MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update(
mbedtls_hmac_drbg_context *ctx, mbedtls_hmac_drbg_context *ctx,
@ -293,26 +345,31 @@ MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update(
#if defined(MBEDTLS_FS_IO) #if defined(MBEDTLS_FS_IO)
/** /**
* \brief Write a seed file * \brief This function writes a seed file.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param path Name of the file * \param path The name of the file.
* *
* \return 0 if successful, 1 on file error, or * \return \c 0 on success.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED * \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on reseed
* failure.
*/ */
int mbedtls_hmac_drbg_write_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path ); int mbedtls_hmac_drbg_write_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
/** /**
* \brief Read and update a seed file. Seed is added to this * \brief This function reads and updates a seed file. The seed
* instance * is added to this instance.
* *
* \param ctx HMAC_DRBG context * \param ctx The HMAC_DRBG context.
* \param path Name of the file * \param path The name of the file.
* *
* \return 0 if successful, 1 on file error, * \return \c 0 on success.
* MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED or * \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
* MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on
* reseed failure.
* \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if the existing
* seed file is too large.
*/ */
int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path ); int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
#endif /* MBEDTLS_FS_IO */ #endif /* MBEDTLS_FS_IO */
@ -320,9 +377,10 @@ int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const ch
#if defined(MBEDTLS_SELF_TEST) #if defined(MBEDTLS_SELF_TEST)
/** /**
* \brief Checkup routine * \brief The HMAC_DRBG Checkup routine.
* *
* \return 0 if successful, or 1 if the test failed * \return \c 0 if successful.
* \return \c 1 if the test failed.
*/ */
int mbedtls_hmac_drbg_self_test( int verbose ); int mbedtls_hmac_drbg_self_test( int verbose );
#endif #endif