fix: BN_swap mishandles flags (1.1.0)

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6101)

diff --git a/crypto/bn/bn_lib.c b/crypto/bn/bn_lib.c
index 07b715d59768964411d7c920c20a9db937606b40..c59bdb7c9e33cd797cfa1617645a852f8ca084d1 100644 (file)
--- a/crypto/bn/bn_lib.c
+++ b/crypto/bn/bn_lib.c
@@ -385,6 +385,11 @@ BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
     return (a);
 }
 
+#define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
+                                    | BN_FLG_CONSTTIME   \
+                                    | BN_FLG_SECURE))
+#define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
+
 void BN_swap(BIGNUM *a, BIGNUM *b)
 {
     int flags_old_a, flags_old_b;
@@ -412,10 +417,8 @@ void BN_swap(BIGNUM *a, BIGNUM *b)
     b->dmax = tmp_dmax;
     b->neg = tmp_neg;
 
-    a->flags =
-        (flags_old_a & BN_FLG_MALLOCED) | (flags_old_b & BN_FLG_STATIC_DATA);
-    b->flags =
-        (flags_old_b & BN_FLG_MALLOCED) | (flags_old_a & BN_FLG_STATIC_DATA);
+    a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
+    b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
     bn_check_top(a);
     bn_check_top(b);
 }