Do the error handling in pkey_rsa_decrypt in constant time

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/8365)

diff --git a/crypto/rsa/rsa_pmeth.c b/crypto/rsa/rsa_pmeth.c
index 2295fa57db7492907ef55b7fd54cefda70becd39..8931d7e8ab81f54a42d427bcc973986253fec90b 100644 (file)
--- a/crypto/rsa/rsa_pmeth.c
+++ b/crypto/rsa/rsa_pmeth.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -7,6 +7,8 @@
  * https://www.openssl.org/source/license.html
  */
 
+#include "internal/constant_time_locl.h"
+
 #include <stdio.h>
 #include "internal/cryptlib.h"
 #include <openssl/asn1t.h>
@@ -340,10 +342,9 @@ static int pkey_rsa_decrypt(EVP_PKEY_CTX *ctx,
         ret = RSA_private_decrypt(inlen, in, out, ctx->pkey->pkey.rsa,
                                   rctx->pad_mode);
     }
-    if (ret < 0)
-        return ret;
-    *outlen = ret;
-    return 1;
+    *outlen = constant_time_select_s(constant_time_msb_s(ret), *outlen, ret);
+    ret = constant_time_select_int(constant_time_msb(ret), ret, 1);
+    return ret;
 }
 
 static int check_padding_md(const EVP_MD *md, int padding)