handle negative scalars correctly when doing point multiplication

diff --git a/crypto/ec/ec_mult.c b/crypto/ec/ec_mult.c
index ddd3db592154f0df8b235f21e453a665ed412afe..01574d8c93bc6286964b6ee806ceb475235aaf6e 100644 (file)
--- a/crypto/ec/ec_mult.c
+++ b/crypto/ec/ec_mult.c
@@ -187,10 +187,18 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar,
                if (i < num)
                        {
                        if (!EC_POINT_copy(val_sub[i][0], points[i])) goto err;
+                       if (scalars[i]->neg)
+                               {
+                               if (!EC_POINT_invert(group, val_sub[i][0], ctx)) goto err;
+                               }
                        }
                else
                        {
                        if (!EC_POINT_copy(val_sub[i][0], generator)) goto err;
+                       if (scalar->neg)
+                               {
+                               if (!EC_POINT_invert(group, val_sub[i][0], ctx)) goto err;
+                               }
                        }
 
                if (wsize[i] > 1)

diff --git a/crypto/ec/ectest.c b/crypto/ec/ectest.c
index b68e27e98a1f4ee4e5b69d06430d469107a9edea..766a0dbc753e4fedcbb1d5a593be03d221791b54 100644 (file)
--- a/crypto/ec/ectest.c
+++ b/crypto/ec/ectest.c
@@ -519,7 +519,7 @@ int main(int argc, char *argv[])
                scalars[0] = y; /* (group order + 1)/2,  so  y*Q + y*Q = Q */
                scalars[1] = y;
 
-               fprintf(stdout, "simultaneous multiplication ... ");
+               fprintf(stdout, "simultaneous multiplication ...");
                fflush(stdout);
 
                /* z is still the group order */
@@ -528,7 +528,22 @@ int main(int argc, char *argv[])
                if (0 != EC_POINT_cmp(group, P, R, ctx)) ABORT;
                if (0 != EC_POINT_cmp(group, R, Q, ctx)) ABORT;
 
-               fprintf(stdout, "ok\n\n");
+               fprintf(stdout, ".");
+               fflush(stdout);
+
+               if (!BN_pseudo_rand(y, BN_num_bits(y), 0, 0)) ABORT;
+               if (!BN_copy(z, y)) ABORT;
+               z->neg = 1;
+
+               points[0] = Q;
+               points[1] = Q;
+               scalars[0] = y;
+               scalars[1] = z;
+
+               if (!EC_POINTs_mul(group, P, NULL, 2, points, scalars, ctx)) ABORT;
+               if (!EC_POINT_is_at_infinity(group, P)) ABORT;
+
+               fprintf(stdout, " ok\n\n");
        }