use timing-safe compares for checking results in signature verification

(there are no known attacks, this is just inexpensive prudence)

feedback and ok tb@ jsing@

1 files changed, 4 insertions, 3 deletions

diff --git a/src/lib/libcrypto/rsa/rsa_sign.c b/src/lib/libcrypto/rsa/rsa_sign.c
index 2383259dda..50e07f4f1e 100644
--- a/src/lib/libcrypto/rsa/rsa_sign.c
+++ b/src/lib/libcrypto/rsa/rsa_sign.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: rsa_sign.c,v 1.30 2018/07/23 17:37:17 tb Exp $ */
+/* $OpenBSD: rsa_sign.c,v 1.31 2018/09/05 00:55:33 djm Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -214,7 +214,8 @@ int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,
                                 RSAerror(RSA_R_INVALID_MESSAGE_LENGTH);
                                 goto err;
                         }
-                        if (memcmp(decrypt_buf, m, SSL_SIG_LENGTH) != 0) {
+                        if (timingsafe_bcmp(decrypt_buf,
+                            m, SSL_SIG_LENGTH) != 0) {
                                 RSAerror(RSA_R_BAD_SIGNATURE);
                                 goto err;
                         }
@@ -244,7 +245,7 @@ int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,
                         goto err;
 
                 if (encoded_len != decrypt_len ||
-                    memcmp(encoded, decrypt_buf, encoded_len) != 0) {
+                    timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) {
                         RSAerror(RSA_R_BAD_SIGNATURE);
                         goto err;
                 }