Expose mbedtls_ct_size_gt and mbedtls_ct_mem_move_to_left in ct interface
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/constant_time.c b/library/constant_time.c
index a786d38..093ae28 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -253,19 +253,7 @@
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
-/** Constant-flow "greater than" comparison:
- * return x > y
- *
- * This is equivalent to \p x > \p y, but is likely to be compiled
- * to code using bitwise operation rather than a branch.
- *
- * \param x The first value to analyze.
- * \param y The second value to analyze.
- *
- * \return 1 if \p x greater than \p y, otherwise 0.
- */
-static unsigned mbedtls_ct_size_gt(size_t x,
- size_t y)
+unsigned mbedtls_ct_size_gt(size_t x, size_t y)
{
/* Return the sign bit (1 for negative) of (y - x). */
return (y - x) >> (sizeof(size_t) * 8 - 1);
@@ -345,23 +333,7 @@
#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
-/** Shift some data towards the left inside a buffer.
- *
- * `mbedtls_ct_mem_move_to_left(start, total, offset)` is functionally
- * equivalent to
- * ```
- * memmove(start, start + offset, total - offset);
- * memset(start + offset, 0, total - offset);
- * ```
- * but it strives to use a memory access pattern (and thus total timing)
- * that does not depend on \p offset. This timing independence comes at
- * the expense of performance.
- *
- * \param start Pointer to the start of the buffer.
- * \param total Total size of the buffer.
- * \param offset Offset from which to copy \p total - \p offset bytes.
- */
-static void mbedtls_ct_mem_move_to_left(void *start,
+void mbedtls_ct_mem_move_to_left(void *start,
size_t total,
size_t offset)
{
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index d8a0fc7..84ca962 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -300,4 +300,42 @@
#endif /* MBEDTLS_BASE64_C */
+
+#if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
+
+/** Constant-flow "greater than" comparison:
+ * return x > y
+ *
+ * This is equivalent to \p x > \p y, but is likely to be compiled
+ * to code using bitwise operation rather than a branch.
+ *
+ * \param x The first value to analyze.
+ * \param y The second value to analyze.
+ *
+ * \return 1 if \p x greater than \p y, otherwise 0.
+ */
+unsigned mbedtls_ct_size_gt(size_t x, size_t y);
+
+/** Shift some data towards the left inside a buffer.
+ *
+ * `mbedtls_ct_mem_move_to_left(start, total, offset)` is functionally
+ * equivalent to
+ * ```
+ * memmove(start, start + offset, total - offset);
+ * memset(start + offset, 0, total - offset);
+ * ```
+ * but it strives to use a memory access pattern (and thus total timing)
+ * that does not depend on \p offset. This timing independence comes at
+ * the expense of performance.
+ *
+ * \param start Pointer to the start of the buffer.
+ * \param total Total size of the buffer.
+ * \param offset Offset from which to copy \p total - \p offset bytes.
+ */
+void mbedtls_ct_mem_move_to_left(void *start,
+ size_t total,
+ size_t offset);
+
+#endif /* defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT) */
+
#endif /* MBEDTLS_CONSTANT_TIME_INTERNAL_H */