[openssl-commits] [openssl] OpenSSL_1_0_2-stable update

[Matt Caswell]

The branch OpenSSL_1_0_2-stable has been updated
       via  86ccadf5bb4d59f2d6acac9b4edd0ae82c580ab4 (commit)
      from  720aa0f534ffd5d5ace4f24a97aab5c9762e482f (commit)


- Log -----------------------------------------------------------------
commit 86ccadf5bb4d59f2d6acac9b4edd0ae82c580ab4
Author: Matt Caswell <matt at openssl.org>
Date:   Wed Sep 27 11:13:47 2017 +0100

    Ensure we test all parameters for BN_FLG_CONSTTIME
    
    RSA_setup_blinding() calls BN_BLINDING_create_param() which later calls
    BN_mod_exp() as follows:
    
    BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx)
    
    ret->mod will have BN_FLG_CONSTTIME set, but ret->e does not. In
    BN_mod_exp() we only test the third param for the existence of this flag.
    We should test all the inputs.
    
    Thanks to Samuel Weiser (samuel.weiser at iaik.tugraz.at) for reporting this
    issue.
    
    This typically only happens once at key load, so this is unlikely to be
    exploitable in any real scenario.
    
    Reviewed-by: Rich Salz <rsalz at openssl.org>
    (Merged from https://github.com/openssl/openssl/pull/4477)
    
    (cherry picked from commit e913d11f444e0b46ec1ebbf3340813693f4d869d)

-----------------------------------------------------------------------

Summary of changes:
 crypto/bn/bn_exp.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 195a786..35facd2 100644
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -145,7 +145,8 @@ int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
     int i, bits, ret = 0;
     BIGNUM *v, *rr;
 
-    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(a, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
         return -1;
@@ -245,7 +246,9 @@ int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
     if (BN_is_odd(m)) {
 # ifdef MONT_EXP_WORD
         if (a->top == 1 && !a->neg
-            && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)) {
+            && (BN_get_flags(p, BN_FLG_CONSTTIME) == 0)
+            && (BN_get_flags(a, BN_FLG_CONSTTIME) == 0)
+            && (BN_get_flags(m, BN_FLG_CONSTTIME) == 0)) {
             BN_ULONG A = a->d[0];
             ret = BN_mod_exp_mont_word(r, A, p, m, ctx, NULL);
         } else
@@ -277,7 +280,9 @@ int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
     BIGNUM *val[TABLE_SIZE];
     BN_RECP_CTX recp;
 
-    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
         return -1;
@@ -411,7 +416,9 @@ int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
     BIGNUM *val[TABLE_SIZE];
     BN_MONT_CTX *mont = NULL;
 
-    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         return BN_mod_exp_mont_consttime(rr, a, p, m, ctx, in_mont);
     }
 
@@ -1217,7 +1224,8 @@ int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,
 #define BN_TO_MONTGOMERY_WORD(r, w, mont) \
                 (BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))
 
-    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_MONT_WORD, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
         return -1;
@@ -1348,7 +1356,9 @@ int BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
     /* Table of variables obtained from 'ctx' */
     BIGNUM *val[TABLE_SIZE];
 
-    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0) {
+    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(a, BN_FLG_CONSTTIME) != 0
+            || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {
         /* BN_FLG_CONSTTIME only supported by BN_mod_exp_mont() */
         BNerr(BN_F_BN_MOD_EXP_SIMPLE, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
         return -1;