Move mbedtls_cf_mpi_uint_lt function to the constant-time module
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/library/bignum.c b/library/bignum.c
index 48ab24c..cd8e69e 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1247,41 +1247,6 @@
return( 0 );
}
-/** Decide if an integer is less than the other, without branches.
- *
- * \param x First integer.
- * \param y Second integer.
- *
- * \return 1 if \p x is less than \p y, 0 otherwise
- */
-static unsigned mbedtls_cf_mpi_uint_lt( const mbedtls_mpi_uint x,
- const mbedtls_mpi_uint y )
-{
- mbedtls_mpi_uint ret;
- mbedtls_mpi_uint cond;
-
- /*
- * Check if the most significant bits (MSB) of the operands are different.
- */
- cond = ( x ^ y );
- /*
- * If the MSB are the same then the difference x-y will be negative (and
- * have its MSB set to 1 during conversion to unsigned) if and only if x<y.
- */
- ret = ( x - y ) & ~cond;
- /*
- * If the MSB are different, then the operand with the MSB of 1 is the
- * bigger. (That is if y has MSB of 1, then x<y is true and it is false if
- * the MSB of y is 0.)
- */
- ret |= y & cond;
-
-
- ret = ret >> ( sizeof( mbedtls_mpi_uint ) * 8 - 1 );
-
- return (unsigned) ret;
-}
-
/*
* Compare signed values in constant time
*/
diff --git a/library/constant_time.c b/library/constant_time.c
index 7da4046..b513c6a 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -20,6 +20,11 @@
#include "common.h"
#include "constant_time.h"
+#if defined(MBEDTLS_BIGNUM_C)
+#include "mbedtls/bignum.h"
+#endif
+
+
/* constant-time buffer comparison */
int mbedtls_ssl_safer_memcmp( const void *a, const void *b, size_t n )
{
@@ -229,3 +234,42 @@
/* Return the sign bit (1 for negative) of (max - size). */
return( ( max - size ) >> ( sizeof( size_t ) * 8 - 1 ) );
}
+
+#if defined(MBEDTLS_BIGNUM_C)
+
+/** Decide if an integer is less than the other, without branches.
+ *
+ * \param x First integer.
+ * \param y Second integer.
+ *
+ * \return 1 if \p x is less than \p y, 0 otherwise
+ */
+unsigned mbedtls_cf_mpi_uint_lt( const mbedtls_mpi_uint x,
+ const mbedtls_mpi_uint y )
+{
+ mbedtls_mpi_uint ret;
+ mbedtls_mpi_uint cond;
+
+ /*
+ * Check if the most significant bits (MSB) of the operands are different.
+ */
+ cond = ( x ^ y );
+ /*
+ * If the MSB are the same then the difference x-y will be negative (and
+ * have its MSB set to 1 during conversion to unsigned) if and only if x<y.
+ */
+ ret = ( x - y ) & ~cond;
+ /*
+ * If the MSB are different, then the operand with the MSB of 1 is the
+ * bigger. (That is if y has MSB of 1, then x<y is true and it is false if
+ * the MSB of y is 0.)
+ */
+ ret |= y & cond;
+
+
+ ret = ret >> ( sizeof( mbedtls_mpi_uint ) * 8 - 1 );
+
+ return (unsigned) ret;
+}
+
+#endif /* MBEDTLS_BIGNUM_C */
diff --git a/library/constant_time.h b/library/constant_time.h
index eff7f44..3c18b4e 100644
--- a/library/constant_time.h
+++ b/library/constant_time.h
@@ -19,6 +19,10 @@
#include "common.h"
+#if defined(MBEDTLS_BIGNUM_C)
+#include "mbedtls/bignum.h"
+#endif
+
#include <stddef.h>
int mbedtls_ssl_safer_memcmp( const void *a, const void *b, size_t n );
@@ -41,3 +45,10 @@
size_t mbedtls_cf_size_bool_eq( size_t x, size_t y );
unsigned mbedtls_cf_size_gt( size_t size, size_t max );
+
+#if defined(MBEDTLS_BIGNUM_C)
+
+unsigned mbedtls_cf_mpi_uint_lt( const mbedtls_mpi_uint x,
+ const mbedtls_mpi_uint y );
+
+#endif /* MBEDTLS_BIGNUM_C */