Adding deserialization checks (#10)

src/group/tests.rs

@@ -0,0 +1,55 @@
+// Copyright (c) Facebook, Inc. and its affiliates.
+//
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+//! Includes a series of tests for the group implementations
+
+use crate::errors::InternalError;
+use crate::group::Group;
+use crate::CipherSuite;
+
+// Test that the deserialization of a group element should throw an error
+// if the identity element can be deserialized properly
+
+#[test]
+fn test_group_properties() -> Result<(), InternalError> {
+    use crate::tests::Ristretto255Sha512;
+
+    test_identity_element_error::<Ristretto255Sha512>()?;
+    test_zero_scalar_error::<Ristretto255Sha512>()?;
+
+    #[cfg(feature = "p256")]
+    {
+        use crate::tests::P256Sha256;
+
+        test_identity_element_error::<P256Sha256>()?;
+        test_zero_scalar_error::<P256Sha256>()?;
+    }
+
+    Ok(())
+}
+
+// Checks that the identity element cannot be deserialized
+fn test_identity_element_error<CS: CipherSuite>() -> Result<(), InternalError> {
+    let identity = CS::Group::identity();
+    let result = CS::Group::from_element_slice(&identity.to_arr());
+    assert!(match result {
+        Err(InternalError::PointError) => true,
+        _ => false,
+    });
+
+    Ok(())
+}
+
+// Checks that the zero scalar cannot be deserialized
+fn test_zero_scalar_error<CS: CipherSuite>() -> Result<(), InternalError> {
+    let zero_scalar = CS::Group::scalar_zero();
+    let result = CS::Group::from_scalar_slice(&CS::Group::scalar_as_bytes(zero_scalar));
+    assert!(match result {
+        Err(InternalError::ZeroScalarError) => true,
+        _ => false,
+    });
+
+    Ok(())
+}