1 files changed, 68 insertions, 3 deletions

diff --git a/src/lib/libcrypto/ec/ecp_smpl.c b/src/lib/libcrypto/ec/ecp_smpl.c
index a25fd1df84..fe935251d9 100644
--- a/src/lib/libcrypto/ec/ecp_smpl.c
+++ b/src/lib/libcrypto/ec/ecp_smpl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ecp_smpl.c,v 1.22 2018/07/16 17:32:39 tb Exp $ */
+/* $OpenBSD: ecp_smpl.c,v 1.23 2018/11/05 20:18:21 tb Exp $ */
 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * for the OpenSSL project.
  * Includes code written by Bodo Moeller for the OpenSSL project.
@@ -107,7 +107,8 @@ EC_GFp_simple_method(void)
                 .mul_single_ct = ec_GFp_simple_mul_single_ct,
                 .mul_double_nonct = ec_GFp_simple_mul_double_nonct,
                 .field_mul = ec_GFp_simple_field_mul,
-                .field_sqr = ec_GFp_simple_field_sqr
+                .field_sqr = ec_GFp_simple_field_sqr,
+                .blind_coordinates = ec_GFp_simple_blind_coordinates,
         };
 
         return &ret;
@@ -1406,13 +1407,70 @@ ec_GFp_simple_field_mul(const EC_GROUP * group, BIGNUM * r, const BIGNUM * a, co
         return BN_mod_mul(r, a, b, &group->field, ctx);
 }
 
-
 int 
 ec_GFp_simple_field_sqr(const EC_GROUP * group, BIGNUM * r, const BIGNUM * a, BN_CTX * ctx)
 {
         return BN_mod_sqr(r, a, &group->field, ctx);
 }
 
+/*
+ * Apply randomization of EC point projective coordinates:
+ *
+ *      (X, Y, Z) = (lambda^2 * X, lambda^3 * Y, lambda * Z)
+ * 
+ * where lambda is in the interval [1, group->field).
+ */
+int
+ec_GFp_simple_blind_coordinates(const EC_GROUP *group, EC_POINT *p, BN_CTX *ctx)
+{
+        BIGNUM *lambda = NULL;
+        BIGNUM *tmp = NULL;
+        int ret = 0;
+
+        BN_CTX_start(ctx);
+        if ((lambda = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((tmp = BN_CTX_get(ctx)) == NULL)
+                goto err;
+
+        /* Generate lambda in [1, group->field - 1] */
+        do {
+                if (!BN_rand_range(lambda, &group->field))
+                        goto err;
+        } while (BN_is_zero(lambda));
+
+        if (group->meth->field_encode != NULL &&
+            !group->meth->field_encode(group, lambda, lambda, ctx))
+                goto err;
+
+        /* Z = lambda * Z */
+        if (!group->meth->field_mul(group, &p->Z, lambda, &p->Z, ctx))
+                goto err;
+
+        /* tmp = lambda^2 */
+        if (!group->meth->field_sqr(group, tmp, lambda, ctx))
+                goto err;
+
+        /* X = lambda^2 * X */
+        if (!group->meth->field_mul(group, &p->X, tmp, &p->X, ctx))
+                goto err;
+
+        /* tmp = lambda^3 */
+        if (!group->meth->field_mul(group, tmp, tmp, lambda, ctx))
+                goto err;
+
+        /* Y = lambda^3 * Y */
+        if (!group->meth->field_mul(group, &p->Y, tmp, &p->Y, ctx))
+                goto err;
+
+        ret = 1;
+
+ err:
+        BN_CTX_end(ctx);
+        return ret;
+}
+
+
 #define EC_POINT_BN_set_flags(P, flags) do {                            \
         BN_set_flags(&(P)->X, (flags));                                 \
         BN_set_flags(&(P)->Y, (flags));                                 \
@@ -1537,6 +1595,13 @@ ec_GFp_simple_mul_ct(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
             (bn_wexpand(&r->Z, group_top) == NULL))
                 goto err;
 
+        /*
+         * Apply coordinate blinding for EC_POINT if the underlying EC_METHOD
+         * implements it.
+         */
+        if (!ec_point_blind_coordinates(group, s, ctx))
+                goto err;
+
         /* top bit is a 1, in a fixed pos */
         if (!EC_POINT_copy(r, s))
                 goto err;