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Document thread safety for CTR_DRBG

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random(), and only this function, is thread-safe.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Signed-off-by: Chris Jones <christopher.jones@arm.com>
This commit is contained in:
Gilles Peskine 2021-02-09 18:44:18 +01:00
parent 2ecc0b89f3
commit 831956980c
1 changed files with 36 additions and 2 deletions
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38
include/mbedtls/ctr_drbg.h
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@ -284,6 +284,15 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
* device. * device.
*/ */
#endif #endif
#if defined(MBEDTLS_THREADING_C)
/**
* \note When Mbed TLS is built with threading support,
* after this function returns successfully,
* it is safe to call mbedtls_ctr_drbg_random()
* from multiple threads. Other operations, including
* reseeding, are not thread-safe.
*/
#endif /* MBEDTLS_THREADING_C */
/** /**
* \param ctx The CTR_DRBG context to seed. * \param ctx The CTR_DRBG context to seed.
* It must have been initialized with * It must have been initialized with
@ -293,6 +302,8 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
* the same context unless you call * the same context unless you call
* mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init() * mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init()
* again first. * again first.
* After a failed call to mbedtls_ctr_drbg_seed(),
* you must call mbedtls_ctr_drbg_free().
* \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.
@ -384,6 +395,11 @@ void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx,
* \brief This function reseeds the CTR_DRBG context, that is * \brief This function reseeds the CTR_DRBG context, that is
* extracts data from the entropy source. * extracts data from the entropy source.
* *
* \note This function is not thread-safe. It is not safe
* to call this function if another thread might be
* concurrently obtaining random numbers from the same
* context or updating or reseeding the same context.
*
* \param ctx The CTR_DRBG context. * \param ctx The CTR_DRBG context.
* \param additional Additional data to add to the state. Can be \c NULL. * \param additional Additional data to add to the state. Can be \c NULL.
* \param len The length of the additional data. * \param len The length of the additional data.
@ -401,6 +417,11 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
/** /**
* \brief This function updates the state of the CTR_DRBG context. * \brief This function updates the state of the CTR_DRBG context.
* *
* \note This function is not thread-safe. It is not safe
* to call this function if another thread might be
* concurrently obtaining random numbers from the same
* context or updating or reseeding the same context.
*
* \param ctx The CTR_DRBG context. * \param ctx The CTR_DRBG context.
* \param additional The data to update the state with. This must not be * \param additional The data to update the state with. This must not be
* \c NULL unless \p add_len is \c 0. * \c NULL unless \p add_len is \c 0.
@ -424,6 +445,11 @@ int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
* This function automatically reseeds if the reseed counter is exceeded * This function automatically reseeds if the reseed counter is exceeded
* or prediction resistance is enabled. * or prediction resistance is enabled.
* *
* \note This function is not thread-safe. It is not safe
* to call this function if another thread might be
* concurrently obtaining random numbers from the same
* context or updating or reseeding the same context.
*
* \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.
@ -452,8 +478,16 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
* *
* This function automatically reseeds if the reseed counter is exceeded * This function automatically reseeds if the reseed counter is exceeded
* or prediction resistance is enabled. * or prediction resistance is enabled.
* */
* #if defined(MBEDTLS_THREADING_C)
/**
* \note When Mbed TLS is built with threading support,
* it is safe to call mbedtls_ctr_drbg_random()
* from multiple threads. Other operations, including
* reseeding, are not thread-safe.
*/
#endif /* MBEDTLS_THREADING_C */
/**
* \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.