Mailing List Archive

* mpi/mpi-add.c (_gcry_mpi_addm, _gcry_mpi_subm): Take copy of M when
W and M are the same MPI.
* mpi/mpi-mul.c (_gcry_mpi_mulm): Likewise.
* tests/mpitests.c (test_addm_subm_mulm): New.
(main): Run addm/subm/mulm test.
--

Reported-by: Guido Vranken <guidovranken@gmail.com>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
---
mpi/mpi-add.c | 22 ++++++++++++++++++++
mpi/mpi-mul.c | 11 ++++++++++
tests/mpitests.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 86 insertions(+)

diff --git a/mpi/mpi-add.c b/mpi/mpi-add.c
index 41dc3900..51dc71b7 100644
--- a/mpi/mpi-add.c
+++ b/mpi/mpi-add.c
@@ -227,13 +227,35 @@ _gcry_mpi_sub(gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
void
_gcry_mpi_addm( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m)
{
+ gcry_mpi_t temp_m = NULL;
+
+ if (w == m)
+ {
+ temp_m = mpi_copy (m);
+ m = temp_m;
+ }
+
mpi_add (w, u, v);
mpi_mod (w, w, m);
+
+ if (temp_m)
+ mpi_free(temp_m);
}

void
_gcry_mpi_subm( gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m)
{
+ gcry_mpi_t temp_m = NULL;
+
+ if (w == m)
+ {
+ temp_m = mpi_copy (m);
+ m = temp_m;
+ }
+
mpi_sub (w, u, v);
mpi_mod (w, w, m);
+
+ if (temp_m)
+ mpi_free(temp_m);
}
diff --git a/mpi/mpi-mul.c b/mpi/mpi-mul.c
index 60f1ca48..e8e57475 100644
--- a/mpi/mpi-mul.c
+++ b/mpi/mpi-mul.c
@@ -207,6 +207,17 @@ _gcry_mpi_mul (gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v)
void
_gcry_mpi_mulm (gcry_mpi_t w, gcry_mpi_t u, gcry_mpi_t v, gcry_mpi_t m)
{
+ gcry_mpi_t temp_m = NULL;
+
+ if (w == m)
+ {
+ temp_m = mpi_copy (m);
+ m = temp_m;
+ }
+
mpi_mul (w, u, v);
_gcry_mpi_tdiv_r (w, w, m);
+
+ if (temp_m)
+ mpi_free(temp_m);
}
diff --git a/tests/mpitests.c b/tests/mpitests.c
index 48ea18b2..1203acdd 100644
--- a/tests/mpitests.c
+++ b/tests/mpitests.c
@@ -687,6 +687,58 @@ test_powm (void)
}


+/* What we test here is that we don't overwrite our divider and that
+ using the same mpi for divider and result works. */
+static int
+test_addm_subm_mulm (void)
+{
+ int i;
+
+ for (i = 0; i < 3; i++)
+ {
+ unsigned int expect;
+ const char *func;
+ gcry_mpi_t A;
+ gcry_mpi_t B;
+ gcry_mpi_t C;
+
+ A = gcry_mpi_set_ui (NULL, 2);
+ B = gcry_mpi_set_ui (NULL, 4);
+ C = gcry_mpi_set_ui (NULL, 7);
+
+ if (i == 0)
+ {
+ func = "mpi_addm";
+ expect = 6;
+ gcry_mpi_addm(C, A, B, C);
+ }
+ else if (i == 1)
+ {
+ func = "mpi_subm";
+ expect = 5;
+ gcry_mpi_subm(C, A, B, C);
+ }
+ else if (i == 2)
+ {
+ func = "mpi_mulm";
+ expect = 1;
+ gcry_mpi_mulm(C, A, B, C);
+ }
+
+ if (gcry_mpi_is_neg (C) || gcry_mpi_cmp_ui (C, expect))
+ {
+ die ("test_addm_subm_mulm failed for %s at %d\n", func, __LINE__);
+ }
+
+ gcry_mpi_release(A);
+ gcry_mpi_release(B);
+ gcry_mpi_release(C);
+ }
+
+ return 1;
+}
+
+
int
main (int argc, char* argv[])
{
@@ -710,6 +762,7 @@ main (int argc, char* argv[])
test_sub ();
test_mul ();
test_powm ();
+ test_addm_subm_mulm ();

return !!error_count;
}
--
2.39.2


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