From 5bd272627b2b79108490fe2ecb8e0a5c2911fb5f Mon Sep 17 00:00:00 2001
From: Ron Eldor <Ron.Eldor@arm.com>
Date: Tue, 17 Oct 2017 18:15:41 +0300
Subject: [PATCH] Backport 2.1:Fix crash when calling `mbedtls_ssl_cache_free`
 twice

Set `cache` to zero at the end of `mbedtls_ssl_cache_free` #1104
---
 ChangeLog           |  2 ++
 library/ssl_cache.c | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index da29d7077..1df65edbd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,8 @@ Bugfix
    * Fix leap year calculation in x509_date_is_valid() to ensure that invalid
      dates on leap years with 100 and 400 intervals are handled correctly. Found
      by Nicholas Wilson. #694
+   * Fix crash when calling mbedtls_ssl_cache_free() twice. Found by
+     MilenkoMitrovic, #1104
 
 = mbed TLS 2.1.9 branch released 2017-08-10
 
diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index 711bc535c..47107b6a0 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -43,6 +43,15 @@
 #define mbedtls_free       free
 #endif
 
+#include "mbedtls/ssl_cache.h"
+
+#include <string.h>
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
 void mbedtls_ssl_cache_init( mbedtls_ssl_cache_context *cache )
 {
     memset( cache, 0, sizeof( mbedtls_ssl_cache_context ) );
@@ -321,6 +330,8 @@ void mbedtls_ssl_cache_free( mbedtls_ssl_cache_context *cache )
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_free( &cache->mutex );
 #endif
+
+    mbedtls_zeroize( cache, sizeof(mbedtls_ssl_cache_context) );
 }
 
 #endif /* MBEDTLS_SSL_CACHE_C */