diff --git a/library/sha256.c b/library/sha256.c
index ad25d38..337b8e6 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -100,7 +100,7 @@
 /*
  * SHA-256 context setup
  */
-void mbedtls_sha256_starts( mbedtls_sha256_context *ctx, int is224 )
+int mbedtls_sha256_starts_ext( mbedtls_sha256_context *ctx, int is224 )
 {
     ctx->total[0] = 0;
     ctx->total[1] = 0;
@@ -131,6 +131,8 @@
     }
 
     ctx->is224 = is224;
+
+    return( 0 );
 }
 
 #if !defined(MBEDTLS_SHA256_PROCESS_ALT)
@@ -179,7 +181,8 @@
     d += temp1; h = temp1 + temp2;              \
 }
 
-void mbedtls_sha256_process( mbedtls_sha256_context *ctx, const unsigned char data[64] )
+int mbedtls_sha256_process_ext( mbedtls_sha256_context *ctx,
+                                const unsigned char data[64] )
 {
     uint32_t temp1, temp2, W[64];
     uint32_t A[8];
@@ -232,20 +235,24 @@
 
     for( i = 0; i < 8; i++ )
         ctx->state[i] += A[i];
+
+    return( 0 );
 }
 #endif /* !MBEDTLS_SHA256_PROCESS_ALT */
 
 /*
  * SHA-256 process buffer
  */
-void mbedtls_sha256_update( mbedtls_sha256_context *ctx, const unsigned char *input,
-                    size_t ilen )
+int mbedtls_sha256_update_ext( mbedtls_sha256_context *ctx,
+                               const unsigned char *input,
+                               size_t ilen )
 {
+    int ret;
     size_t fill;
     uint32_t left;
 
     if( ilen == 0 )
-        return;
+        return( 0 );
 
     left = ctx->total[0] & 0x3F;
     fill = 64 - left;
@@ -259,7 +266,10 @@
     if( left && ilen >= fill )
     {
         memcpy( (void *) (ctx->buffer + left), input, fill );
-        mbedtls_sha256_process( ctx, ctx->buffer );
+
+        if( ( ret = mbedtls_sha256_process_ext( ctx, ctx->buffer ) ) != 0 )
+            return( ret );
+
         input += fill;
         ilen  -= fill;
         left = 0;
@@ -267,13 +277,17 @@
 
     while( ilen >= 64 )
     {
-        mbedtls_sha256_process( ctx, input );
+        if( ( ret = mbedtls_sha256_process_ext( ctx, input ) ) != 0 )
+            return( ret );
+
         input += 64;
         ilen  -= 64;
     }
 
     if( ilen > 0 )
         memcpy( (void *) (ctx->buffer + left), input, ilen );
+
+    return( 0 );
 }
 
 static const unsigned char sha256_padding[64] =
@@ -287,8 +301,10 @@
 /*
  * SHA-256 final digest
  */
-void mbedtls_sha256_finish( mbedtls_sha256_context *ctx, unsigned char output[32] )
+int mbedtls_sha256_finish_ext( mbedtls_sha256_context *ctx,
+                               unsigned char output[32] )
 {
+    int ret;
     uint32_t last, padn;
     uint32_t high, low;
     unsigned char msglen[8];
@@ -303,8 +319,11 @@
     last = ctx->total[0] & 0x3F;
     padn = ( last < 56 ) ? ( 56 - last ) : ( 120 - last );
 
-    mbedtls_sha256_update( ctx, sha256_padding, padn );
-    mbedtls_sha256_update( ctx, msglen, 8 );
+    if( ( ret = mbedtls_sha256_update_ext( ctx, sha256_padding, padn ) ) != 0 )
+            return( ret );
+
+    if( ( ret = mbedtls_sha256_update_ext( ctx, msglen, 8 ) ) != 0 )
+            return( ret );
 
     PUT_UINT32_BE( ctx->state[0], output,  0 );
     PUT_UINT32_BE( ctx->state[1], output,  4 );
@@ -316,6 +335,8 @@
 
     if( ctx->is224 == 0 )
         PUT_UINT32_BE( ctx->state[7], output, 28 );
+
+    return( 0 );
 }
 
 #endif /* !MBEDTLS_SHA256_ALT */
@@ -323,16 +344,28 @@
 /*
  * output = SHA-256( input buffer )
  */
-void mbedtls_sha256( const unsigned char *input, size_t ilen,
-             unsigned char output[32], int is224 )
+int mbedtls_sha256_ext( const unsigned char *input,
+                        size_t ilen,
+                        unsigned char output[32],
+                        int is224 )
 {
+    int ret;
     mbedtls_sha256_context ctx;
 
     mbedtls_sha256_init( &ctx );
-    mbedtls_sha256_starts( &ctx, is224 );
-    mbedtls_sha256_update( &ctx, input, ilen );
-    mbedtls_sha256_finish( &ctx, output );
+
+    if( ( ret = mbedtls_sha256_starts_ext( &ctx, is224 ) ) != 0 )
+            return( ret );
+
+    if( ( ret = mbedtls_sha256_update_ext( &ctx, input, ilen ) ) != 0 )
+            return( ret );
+
+    if( ( ret = mbedtls_sha256_finish_ext( &ctx, output ) ) != 0 )
+            return( ret );
+
     mbedtls_sha256_free( &ctx );
+
+    return( 0 );
 }
 
 #if defined(MBEDTLS_SELF_TEST)
@@ -415,29 +448,31 @@
         if( verbose != 0 )
             mbedtls_printf( "  SHA-%d test #%d: ", 256 - k * 32, j + 1 );
 
-        mbedtls_sha256_starts( &ctx, k );
+        if( mbedtls_sha256_starts_ext( &ctx, k ) != 0 )
+            goto fail;
 
         if( j == 2 )
         {
             memset( buf, 'a', buflen = 1000 );
 
             for( j = 0; j < 1000; j++ )
-                mbedtls_sha256_update( &ctx, buf, buflen );
+                if( mbedtls_sha256_update_ext( &ctx, buf, buflen ) != 0 )
+                    goto fail;
+
         }
         else
-            mbedtls_sha256_update( &ctx, sha256_test_buf[j],
-                                 sha256_test_buflen[j] );
+        {
+           if(  mbedtls_sha256_update_ext( &ctx, sha256_test_buf[j],
+                                           sha256_test_buflen[j] ) != 0 )
+                goto fail;
+        }
 
-        mbedtls_sha256_finish( &ctx, sha256sum );
+        if( mbedtls_sha256_finish_ext( &ctx, sha256sum ) != 0 )
+            goto fail;
+
 
         if( memcmp( sha256sum, sha256_test_sum[i], 32 - k * 4 ) != 0 )
-        {
-            if( verbose != 0 )
-                mbedtls_printf( "failed\n" );
-
-            ret = 1;
-            goto exit;
-        }
+            goto fail;
 
         if( verbose != 0 )
             mbedtls_printf( "passed\n" );
@@ -446,6 +481,14 @@
     if( verbose != 0 )
         mbedtls_printf( "\n" );
 
+    goto exit;
+
+fail:
+    if( verbose != 0 )
+        mbedtls_printf( "failed\n" );
+
+    ret = 1;
+
 exit:
     mbedtls_sha256_free( &ctx );
     mbedtls_free( buf );