rust/pvsecret: User defined signatures and verifications

Introduces the ability to `pvsecret` to add a signature (ecdsa or rsa)
to the program-reserved space (user-data) of an add-secret request
during the request creation. Additionally, some arbitrary data may be
inserted.

The new command `verify` checks if add-secret requests are sane (e.g.
start with the correct magic value). If the request contains a
user-signature `verify` will also verify this signature.

Acked-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pvsecret/src/cmd.rs

@@ -5,6 +5,9 @@
 mod create;
 pub use create::create;
 
+mod verify;
+pub use verify::verify;
+
 // Commands (directly) related to UVCs are only available on s389x
 #[cfg(target_arch = "s390x")]
 mod add;