mpi: Clear immutable flag on the result of gcry_mpi_set.

* mpi/mpiutil.c (gcry_mpi_set): Reset immutable and const flags.
* tests/mpitests.c (test_const_and_immutable): Add a test for this.
--

gcry_mpi_set shall behave like gcry_mpi_copy and thus reset those
special flags.  Problem reported by Christian Grothoff.

Signed-off-by: Werner Koch <wk@gnupg.org>

2 files changed, 18 insertions, 0 deletions

diff --git a/mpi/mpiutil.c b/mpi/mpiutil.c
index cff15b74..a65d2361 100644
--- a/mpi/mpiutil.c
+++ b/mpi/mpiutil.c
@@ -397,6 +397,7 @@ gcry_mpi_set( gcry_mpi_t w, gcry_mpi_t u)
   MPN_COPY( wp, up, usize );
   w->nlimbs = usize;
   w->flags = u->flags;
+  w->flags &= ~(16|32); /* Reset the immutable and constant flags.  */
   w->sign = usign;
   return w;
 }
diff --git a/tests/mpitests.c b/tests/mpitests.c
index 03c15b90..e1c51d16 100644
--- a/tests/mpitests.c
+++ b/tests/mpitests.c
@@ -143,6 +143,23 @@ test_const_and_immutable (void)
   if (!gcry_mpi_get_flag (one, GCRYMPI_FLAG_CONST))
     die ("const flag unexpectly cleared\n");
 
+
+  second_one = gcry_mpi_set (NULL, GCRYMPI_CONST_ONE);
+  if (gcry_mpi_get_flag (second_one, GCRYMPI_FLAG_IMMUTABLE))
+    die ("immutable flag not cleared by mpi_set (NULL,x)\n");
+  if (gcry_mpi_get_flag (second_one, GCRYMPI_FLAG_CONST))
+    die ("const flag not cleared by mpi_set (NULL,x)\n");
+  gcry_mpi_release (second_one);
+
+  second_one = gcry_mpi_set_ui (NULL, 42);
+  gcry_mpi_set (second_one, GCRYMPI_CONST_ONE);
+  if (gcry_mpi_get_flag (second_one, GCRYMPI_FLAG_IMMUTABLE))
+    die ("immutable flag not cleared after mpi_set (a,x)\n");
+  if (gcry_mpi_get_flag (second_one, GCRYMPI_FLAG_CONST))
+    die ("const flag not cleared mpi_set (a,x)\n");
+  gcry_mpi_release (second_one);
+
+
   /* Due to the the constant flag the release below should be a NOP
      and will leak memory.  */
   gcry_mpi_release (one);