From 2f18596c32d145f194c3d1eac9b9e77b560aad71 Mon Sep 17 00:00:00 2001
From: Cesar Pereida Garcia <cesar.pereidagarcia@tut.fi>
Date: Thu, 5 Sep 2019 12:13:11 +0300
Subject: [PATCH] [crypto/asn1] 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/9779)
---
 crypto/asn1/x_bignum.c | 17 ++++++++++++++---
 crypto/rsa/rsa_lib.c   |  6 ++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/crypto/asn1/x_bignum.c b/crypto/asn1/x_bignum.c
index da57e77a7a..c1e3e523a0 100644
--- a/crypto/asn1/x_bignum.c
+++ b/crypto/asn1/x_bignum.c
@@ -130,9 +130,20 @@ static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
 static int bn_secure_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
                          int utype, char *free_cont, const ASN1_ITEM *it)
 {
-    if (!*pval)
-        bn_secure_new(pval, it);
-    return bn_c2i(pval, cont, len, utype, free_cont, it);
+    int ret;
+    BIGNUM *bn;
+
+    if (!*pval && !bn_secure_new(pval, it))
+        return 0;
+
+    ret = bn_c2i(pval, cont, len, utype, free_cont, it);
+    if (!ret)
+        return 0;
+
+    /* Set constant-time flag for all secure BIGNUMS */
+    bn = (BIGNUM *)*pval;
+    BN_set_flags(bn, BN_FLG_CONSTTIME);
+    return ret;
 }
 
 static int bn_print(BIO *out, ASN1_VALUE **pval, const ASN1_ITEM *it,
diff --git a/crypto/rsa/rsa_lib.c b/crypto/rsa/rsa_lib.c
index 49c34b7c36..c21d3d9382 100644
--- a/crypto/rsa/rsa_lib.c
+++ b/crypto/rsa/rsa_lib.c
@@ -198,6 +198,7 @@ int RSA_set0_key(RSA *r, BIGNUM *n, BIGNUM *e, BIGNUM *d)
     if (d != NULL) {
         BN_clear_free(r->d);
         r->d = d;
+        BN_set_flags(r->d, BN_FLG_CONSTTIME);
     }
 
     return 1;
@@ -215,10 +216,12 @@ int RSA_set0_factors(RSA *r, BIGNUM *p, BIGNUM *q)
     if (p != NULL) {
         BN_clear_free(r->p);
         r->p = p;
+        BN_set_flags(r->p, BN_FLG_CONSTTIME);
     }
     if (q != NULL) {
         BN_clear_free(r->q);
         r->q = q;
+        BN_set_flags(r->q, BN_FLG_CONSTTIME);
     }
 
     return 1;
@@ -237,14 +240,17 @@ int RSA_set0_crt_params(RSA *r, BIGNUM *dmp1, BIGNUM *dmq1, BIGNUM *iqmp)
     if (dmp1 != NULL) {
         BN_clear_free(r->dmp1);
         r->dmp1 = dmp1;
+        BN_set_flags(r->dmp1, BN_FLG_CONSTTIME);
     }
     if (dmq1 != NULL) {
         BN_clear_free(r->dmq1);
         r->dmq1 = dmq1;
+        BN_set_flags(r->dmq1, BN_FLG_CONSTTIME);
     }
     if (iqmp != NULL) {
         BN_clear_free(r->iqmp);
         r->iqmp = iqmp;
+        BN_set_flags(r->iqmp, BN_FLG_CONSTTIME);
     }
 
     return 1;
-- 
2.25.1