Provide constant time operations for uint8_t.

These will be used in upcoming changes.

ok tb@

diff --git a/lib/libcrypto/crypto_internal.h b/lib/libcrypto/crypto_internal.h
index 924cf6d..8229db2 100644 (file)
--- a/lib/libcrypto/crypto_internal.h
+++ b/lib/libcrypto/crypto_internal.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: crypto_internal.h,v 1.9 2024/03/28 08:36:13 jsing Exp $ */
+/*     $OpenBSD: crypto_internal.h,v 1.10 2024/04/17 14:43:37 jsing Exp $ */
 /*
  * Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
  *
@@ -26,6 +26,73 @@
 #define CTASSERT(x) \
     extern char _ctassert[(x) ? 1 : -1] __attribute__((__unused__))
 
+/*
+ * Constant time operations for uint8_t.
+ */
+#ifndef HAVE_CRYPTO_CT_NE_ZERO_U8
+static inline int
+crypto_ct_ne_zero_u8(uint8_t v)
+{
+       return (uint8_t)(v | ~(v - 1)) >> ((sizeof(v) * 8) - 1);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_NE_ZERO_MASK_U8
+static inline uint8_t
+crypto_ct_ne_zero_mask_u8(uint8_t v)
+{
+       return 0 - crypto_ct_ne_zero_u8(v);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_EQ_ZERO_U8
+static inline int
+crypto_ct_eq_zero_u8(uint8_t v)
+{
+       return 1 - crypto_ct_ne_zero_u8(v);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_EQ_ZERO_MASK_U8
+static inline uint8_t
+crypto_ct_eq_zero_mask_u8(uint8_t v)
+{
+       return 0 - crypto_ct_eq_zero_u8(v);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_NE_U8
+static inline int
+crypto_ct_ne_u8(uint8_t a, uint8_t b)
+{
+       return crypto_ct_ne_zero_u8(a - b);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_NE_MASK_U8
+static inline uint8_t
+crypto_ct_ne_mask_u8(uint8_t a, uint8_t b)
+{
+       return 0 - crypto_ct_ne_u8(a, b);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_EQ_U8
+static inline int
+crypto_ct_eq_u8(uint8_t a, uint8_t b)
+{
+       return crypto_ct_eq_zero_u8(a - b);
+}
+#endif
+
+#ifndef HAVE_CRYPTO_CT_EQ_MASK_U8
+static inline uint8_t
+crypto_ct_eq_mask_u8(uint8_t a, uint8_t b)
+{
+       return 0 - crypto_ct_eq_u8(a, b);
+}
+#endif
+
 /*
  * crypto_load_be32toh() loads a 32 bit unsigned big endian value as a 32 bit
  * unsigned host endian value, from the specified address in memory. The memory