From 27ce0b5ff19f44d89efea491cf7d538ee7354abf 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 1.3:Set PEM buffer to zero before freeing it

Set PEM buffer to zero before freeing it, to avoid private keys
being leaked to memory after releasing it.
---
 ChangeLog     | 6 ++++++
 library/pem.c | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index a3171d7eb4..92f1baee8c 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 1.3.21 branch released 2017-08-10
 
 Security
diff --git a/library/pem.c b/library/pem.c
index b2c16c292a..76905b358a 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -389,6 +389,8 @@ int pem_read_buffer( pem_context *ctx, const char *header, const char *footer,
 
 void pem_free( pem_context *ctx )
 {
+    if ( ctx->buf != NULL )
+        polarssl_zeroize( ctx->buf, ctx->buflen );
     polarssl_free( ctx->buf );
     polarssl_free( ctx->info );