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Fix mutex leak in HMAC_DRBG

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mbedtls_hmac_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_hmac_drbg_free() no longer reinitializes the
mutex. To preserve the property that mbedtls_hmac_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_hmac_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 2021-01-31 00:06:51 +01:00
parent f305d92480
commit b791dc66ce
1 changed files with 10 additions and 8 deletions
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18
library/hmac_drbg.c
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@ -54,10 +54,6 @@ void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx )
memset( ctx, 0, sizeof( mbedtls_hmac_drbg_context ) );
ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
/*
@ -129,6 +125,10 @@ int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
if( ( ret = mbedtls_md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 )
return( ret );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
/*
* Set initial working state.
* Use the V memory location, which is currently all 0, to initialize the
@ -254,6 +254,10 @@ int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
if( ( ret = mbedtls_md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 )
return( ret );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
md_size = mbedtls_md_get_size( md_info );
/*
@ -421,14 +425,12 @@ void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx )
return;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
if( ctx->md_ctx.md_info != NULL )
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_md_free( &ctx->md_ctx );
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_hmac_drbg_context ) );
ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
#if defined(MBEDTLS_FS_IO)