1 files changed, 54 insertions, 14 deletions

diff --git a/src/crypto/x25519.c b/src/crypto/x25519.c
index d58f7168c..95c42ea13 100644
--- a/src/crypto/x25519.c
+++ b/src/crypto/x25519.c
@@ -22,6 +22,7 @@
  */
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+FILE_SECBOOT ( PERMITTED );
 
 /** @file
  *
@@ -334,6 +335,7 @@ static void x25519_init_constants ( void ) {
 
 /** Initialisation function */
 struct init_fn x25519_init_fn __init_fn ( INIT_NORMAL ) = {
+	.name = "x25519",
 	.initialise = x25519_init_constants,
 };
 
@@ -563,8 +565,8 @@ void x25519_invert ( const union x25519_oct258 *invertend,
  * @v value		Big integer to be subtracted from, if possible
  */
 static void x25519_reduce_by ( const x25519_t *subtrahend, x25519_t *value ) {
-	unsigned int max_bit = ( ( 8 * sizeof ( *value ) ) - 1 );
 	x25519_t tmp;
+	int underflow;
 
 	/* Conditionally subtract subtrahend
 	 *
@@ -572,8 +574,8 @@ static void x25519_reduce_by ( const x25519_t *subtrahend, x25519_t *value ) {
 	 * time) if the subtraction underflows.
 	 */
 	bigint_copy ( value, &tmp );
-	bigint_subtract ( subtrahend, value );
-	bigint_swap ( value, &tmp, bigint_bit_is_set ( value, max_bit ) );
+	underflow = bigint_subtract ( subtrahend, value );
+	bigint_swap ( value, &tmp, underflow );
 }
 
 /**
@@ -783,16 +785,29 @@ static void x25519_reverse ( struct x25519_value *value ) {
 }
 
 /**
+ * Check if X25519 value is zero
+ *
+ * @v value		Value to check
+ * @ret is_zero		Value is zero
+ */
+int x25519_is_zero ( const struct x25519_value *value ) {
+	x25519_t point;
+
+	/* Check if value is zero */
+	bigint_init ( &point, value->raw, sizeof ( value->raw ) );
+	return bigint_is_zero ( &point );
+}
+
+/**
  * Calculate X25519 key
  *
  * @v base		Base point
  * @v scalar		Scalar multiple
  * @v result		Point to hold result (may overlap base point)
- * @ret rc		Return status code
  */
-int x25519_key ( const struct x25519_value *base,
-		 const struct x25519_value *scalar,
-		 struct x25519_value *result ) {
+void x25519_key ( const struct x25519_value *base,
+		  const struct x25519_value *scalar,
+		  struct x25519_value *result ) {
 	struct x25519_value *tmp = result;
 	union x25519_quad257 point;
 
@@ -813,15 +828,24 @@ int x25519_key ( const struct x25519_value *base,
 	/* Reverse result */
 	bigint_done ( &point.value, result->raw, sizeof ( result->raw ) );
 	x25519_reverse ( result );
+}
+
+/**
+ * Check if this is the point at infinity
+ *
+ * @v point		Curve point
+ * @ret is_infinity	This is the point at infinity
+ */
+static int x25519_curve_is_infinity ( const void *point ) {
 
-	/* Fail if result was all zeros (as required by RFC8422) */
-	return ( bigint_is_zero ( &point.value ) ? -EPERM : 0 );
+	/* We use all zeroes for the point at infinity (as per RFC8422) */
+	return x25519_is_zero ( point );
 }
 
 /**
  * Multiply scalar by curve point
  *
- * @v base		Base point (or NULL to use generator)
+ * @v base		Base point
  * @v scalar		Scalar multiple
  * @v result		Result point to fill in
  * @ret rc		Return status code
@@ -829,16 +853,32 @@ int x25519_key ( const struct x25519_value *base,
 static int x25519_curve_multiply ( const void *base, const void *scalar,
 				   void *result ) {
 
-	/* Use base point if applicable */
-	if ( ! base )
-		base = &x25519_generator;
+	x25519_key ( base, scalar, result );
+	return 0;
+}
+
+/**
+ * Add curve points (as a one-off operation)
+ *
+ * @v addend		Curve point to add
+ * @v augend		Curve point to add
+ * @v result		Curve point to hold result
+ * @ret rc		Return status code
+ */
+static int x25519_curve_add ( const void *addend __unused,
+			      const void *augend __unused,
+			      void *result __unused ) {
 
-	return x25519_key ( base, scalar, result );
+	return -ENOTTY;
 }
 
 /** X25519 elliptic curve */
 struct elliptic_curve x25519_curve = {
 	.name = "x25519",
+	.pointsize = sizeof ( struct x25519_value ),
 	.keysize = sizeof ( struct x25519_value ),
+	.base = x25519_generator.raw,
+	.is_infinity = x25519_curve_is_infinity,
 	.multiply = x25519_curve_multiply,
+	.add = x25519_curve_add,
 };