Fix mutex leak in HMAC_DRBG
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>
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 25a0225..d322b65 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -54,10 +54,6 @@
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 @@
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 @@
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 @@
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)
