1 files changed, 41 insertions, 0 deletions
diff --git a/include/internal/constant_time.h b/include/internal/constant_time.h
index 0ed6f823c1..9ffa4399a3 100644
--- a/include/internal/constant_time.h
+++ b/include/internal/constant_time.h
@@ -140,6 +140,47 @@ static ossl_inline uint64_t constant_time_lt_64(uint64_t a, uint64_t b)
     return constant_time_msb_64(a ^ ((a ^ b) | ((a - b) ^ b)));
 }
 
+#ifdef BN_ULONG
+static ossl_inline BN_ULONG value_barrier_bn(BN_ULONG a)
+{
+#if !defined(OPENSSL_NO_ASM) && defined(__GNUC__)
+    BN_ULONG r;
+    __asm__("" : "=r"(r) : "0"(a));
+#else
+    volatile BN_ULONG r = a;
+#endif
+    return r;
+}
+
+static ossl_inline BN_ULONG constant_time_msb_bn(BN_ULONG a)
+{
+    return 0 - (a >> (sizeof(a) * 8 - 1));
+}
+
+static ossl_inline BN_ULONG constant_time_lt_bn(BN_ULONG a, BN_ULONG b)
+{
+    return constant_time_msb_bn(a ^ ((a ^ b) | ((a - b) ^ b)));
+}
+
+static ossl_inline BN_ULONG constant_time_is_zero_bn(BN_ULONG a)
+{
+    return constant_time_msb_bn(~a & (a - 1));
+}
+
+static ossl_inline BN_ULONG constant_time_eq_bn(BN_ULONG a,
+                                                BN_ULONG b)
+{
+    return constant_time_is_zero_bn(a ^ b);
+}
+
+static ossl_inline BN_ULONG constant_time_select_bn(BN_ULONG mask,
+                                                    BN_ULONG a,
+                                                    BN_ULONG b)
+{
+    return (value_barrier_bn(mask) & a) | (value_barrier_bn(~mask) & b);
+}
+#endif
+
 static ossl_inline unsigned int constant_time_ge(unsigned int a,
                                                  unsigned int b)
 {