[crypto/rsa] Fix multiple SCA vulnerabilities during RSA key validation.

This commit addresses multiple side-channel vulnerabilities present during RSA key validation.
Private key parameters are re-computed using variable-time functions.

This issue was discovered and reported by the NISEC group at TAU Finland.

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9785)

diff --git a/crypto/rsa/rsa_chk.c b/crypto/rsa/rsa_chk.c
index 475dfc56289a1f5df3f57885dd740782fc4444fa..3ea4e029742001c08ca0367ad994b75fc70e78b3 100644 (file)
--- a/crypto/rsa/rsa_chk.c
+++ b/crypto/rsa/rsa_chk.c
@@ -63,6 +63,10 @@ int RSA_check_key(const RSA *key)
         return 0;
     }
 
+    /* Set consant-time flag on private parameters */
+    BN_set_flags(key->p, BN_FLG_CONSTTIME);
+    BN_set_flags(key->q, BN_FLG_CONSTTIME);
+    BN_set_flags(key->d, BN_FLG_CONSTTIME);
     i = BN_new();
     j = BN_new();
     k = BN_new();
@@ -141,6 +145,10 @@ int RSA_check_key(const RSA *key)
     }
 
     if (key->dmp1 != NULL && key->dmq1 != NULL && key->iqmp != NULL) {
+        /* Set consant-time flag on CRT parameters */
+        BN_set_flags(key->dmp1, BN_FLG_CONSTTIME);
+        BN_set_flags(key->dmq1, BN_FLG_CONSTTIME);
+        BN_set_flags(key->iqmp, BN_FLG_CONSTTIME);
         /* dmp1 = d mod (p-1)? */
         if (!BN_sub(i, key->p, BN_value_one())) {
             ret = -1;