Make entropy double-free work
Although the library documentation does not guarantee that calling
mbedtls_entropy_free() twice works, it's a plausible assumption and it's
natural to write code that frees an object twice. While this is uncommon for
an entropy context, which is usually a global variable, it came up in our
own unit tests (random_twice tests in test_suite_random in the
development branch).
Announce this in the same changelog entry as for RSA because it's the same
bug in the two modules.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/entropy.c b/library/entropy.c
index 666c556..c5f414a 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -146,6 +146,11 @@
void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
{
+ /* If the context was already free, don't call free() again.
+ * This is important for mutexes which don't allow double-free. */
+ if( ctx->accumulator_started == -1 )
+ return;
+
#if defined(MBEDTLS_HAVEGE_C)
mbedtls_havege_free( &ctx->havege_data );
#endif
@@ -162,7 +167,7 @@
#endif
ctx->source_count = 0;
mbedtls_platform_zeroize( ctx->source, sizeof( ctx->source ) );
- ctx->accumulator_started = 0;
+ ctx->accumulator_started = -1;
}
int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,