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Fix mutex leak in CTR_DRBG

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mbedtls_ctr_drbg_free() left a mutex in the initialized state. This
caused a resource leak on platforms where mbedtls_mutex_init()
allocates resources.

To fix this, mbedtls_ctr_drbg_free() no longer reinitializes the
mutex. To preserve the property that mbedtls_ctr_drbg_free() leaves
the object in an initialized state, which is generally true throughout
the library except regarding mutex objects on some platforms, no
longer initialize the mutex in mbedtls_ctr_drbg_init(). Since the
mutex is only used after seeding, and seeding is only permitted once,
call mbedtls_mutex_init() as part of the seeding process.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-01-30 13:05:32 +01:00
parent 39a1a26d0b
commit f4b3429782
1 changed files with 6 additions and 8 deletions
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14
library/ctr_drbg.c
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@ -56,10 +56,6 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx )
ctx->reseed_counter = -1; ctx->reseed_counter = -1;
ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL; ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
} }
/* /*
@ -72,15 +68,13 @@ void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx )
return; return;
#if defined(MBEDTLS_THREADING_C) #if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex ); if( ctx->f_entropy != NULL )
mbedtls_mutex_free( &ctx->mutex );
#endif #endif
mbedtls_aes_free( &ctx->aes_ctx ); mbedtls_aes_free( &ctx->aes_ctx );
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) ); mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL; ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
ctx->reseed_counter = -1; ctx->reseed_counter = -1;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
} }
void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx, void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
@ -464,6 +458,10 @@ int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
memset( key, 0, MBEDTLS_CTR_DRBG_KEYSIZE ); memset( key, 0, MBEDTLS_CTR_DRBG_KEYSIZE );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
mbedtls_aes_init( &ctx->aes_ctx ); mbedtls_aes_init( &ctx->aes_ctx );
ctx->f_entropy = f_entropy; ctx->f_entropy = f_entropy;