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Document mutex invariant for CTR_DRBG

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Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-02-09 18:44:02 +01:00
parent f4b3429782
commit da290f9bcd
2 changed files with 9 additions and 0 deletions
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7
include/mbedtls/ctr_drbg.h
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@ -200,6 +200,13 @@ typedef struct mbedtls_ctr_drbg_context
void *p_entropy; /*!< The context for the entropy function. */
#if defined(MBEDTLS_THREADING_C)
/* Invariant: the mutex is initialized if and only if f_entropy != NULL.
* This means that the mutex is initialized during the initial seeding
* in mbedtls_ctr_drbg_seed() and freed in mbedtls_ctr_drbg_free().
*
* Note that this invariant may change without notice. Do not rely on it
* and do not access the mutex directly in application code.
*/
mbedtls_threading_mutex_t mutex;
#endif
}

2
library/ctr_drbg.c
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@ -68,6 +68,7 @@ void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx )
return;
#if defined(MBEDTLS_THREADING_C)
/* The mutex is initialized iff f_entropy is set. */
if( ctx->f_entropy != NULL )
mbedtls_mutex_free( &ctx->mutex );
#endif
@ -458,6 +459,7 @@ int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
memset( key, 0, MBEDTLS_CTR_DRBG_KEYSIZE );
/* The mutex is initialized iff f_entropy is set. */
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif