From 4dc8af77a91ec3129c66bc686d470fd8cfca80f5 Mon Sep 17 00:00:00 2001
From: Ron Eldor <Ron.Eldor@arm.com>
Date: Tue, 5 Sep 2017 15:34:35 +0300
Subject: [PATCH] Backport 2.1:Set PEM buffer to zero before freeing

Set PEM buffer to zero before freeing it, to avoid private keys
being leaked to memory after releasing it.
---
 ChangeLog     | 6 ++++++
 library/pem.c | 1 +
 2 files changed, 7 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 1d06476d7..f32c7299a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS x.x.x branch released xxxx-xx-xx
+
+Security
+   * Set PEM buffer to zero before freeing it, to avoid decoded private keys
+     being leaked to memory after release.
+
 = mbed TLS 2.1.9 branch released 2017-08-10
 
 Security
diff --git a/library/pem.c b/library/pem.c
index 8dd86a4ac..4c2337393 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -387,6 +387,7 @@ int mbedtls_pem_read_buffer( mbedtls_pem_context *ctx, const char *header, const
 
 void mbedtls_pem_free( mbedtls_pem_context *ctx )
 {
+    memset( ctx->buf, 0, ctx->buflen );
     mbedtls_free( ctx->buf );
     mbedtls_free( ctx->info );