From 1adcd95a259c14cbb7f2d3525561ab03360e1339 Mon Sep 17 00:00:00 2001
From: Andres Amaya Garcia <andres.amayagarcia@arm.com>
Date: Mon, 26 Jun 2017 09:58:59 +0100
Subject: [PATCH] Zeroize tmp bufs in entropy.c functions

---
 library/entropy.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/library/entropy.c b/library/entropy.c
index d4d1b27b7..a500b5312 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -242,7 +242,7 @@ static int entropy_gather_internal( mbedtls_entropy_context *ctx )
         if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
                         buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen ) ) != 0 )
         {
-            return( ret );
+            goto cleanup;
         }
 
         /*
@@ -256,9 +256,12 @@ static int entropy_gather_internal( mbedtls_entropy_context *ctx )
     }
 
     if( have_one_strong == 0 )
-        return( MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE );
+        ret = MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE;
 
-    return( 0 );
+cleanup:
+    mbedtls_zeroize( buf, sizeof( buf ) );
+
+    return( ret );
 }
 
 /*
@@ -370,6 +373,8 @@ int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
     ret = 0;
 
 exit:
+    mbedtls_zeroize( buf, sizeof( buf ) );
+
 #if defined(MBEDTLS_THREADING_C)
     if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
         return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
@@ -393,9 +398,9 @@ int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx )
 
     /* Manually update the remaining stream with a separator value to diverge */
     memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
-    mbedtls_entropy_update_manual( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
+    ret = mbedtls_entropy_update_manual( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
 
-    return( 0 );
+    return( ret );
 }
 #endif /* MBEDTLS_ENTROPY_NV_SEED */
 
@@ -421,12 +426,15 @@ int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *p
     ret = 0;
 
 exit:
+    mbedtls_zeroize( buf, sizeof( buf ) );
+
     fclose( f );
     return( ret );
 }
 
 int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path )
 {
+    int ret = 0;
     FILE *f;
     size_t n;
     unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
@@ -442,14 +450,16 @@ int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *
         n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
 
     if( fread( buf, 1, n, f ) != n )
-    {
-        fclose( f );
-        return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
-    }
+        ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
+    else
+        ret = mbedtls_entropy_update_manual( ctx, buf, n );
 
     fclose( f );
 
-    mbedtls_entropy_update_manual( ctx, buf, n );
+    mbedtls_zeroize( buf, sizeof( buf ) );
+
+    if( ret != 0 )
+        return( ret );
 
     return( mbedtls_entropy_write_seed_file( ctx, path ) );
 }