Fix dangling pointer issue

This fixes an issue with the handling of the nonce field when opening
authentication sessions. The ESYS layer expects either a pointer to a
valid nonce of at least 16 bytes, or NULL if no nonce is provided. Our
handling, however, passed down an invalid pointer that was referencing a
now-defunct structure.

What happened, both before #340 and after, was that the `Nonce` input
was moved into a separate scope, either a `match` or a lambda function,
then converted to `TPM2B_NONCE`. A reference to this `TPM2B_NONCE` was
taken and converted to `*const TPM2B_NONCE`, which was passed outside of
the scope. The pointer, therefore, ended up referencing a structure that
was dropped at the end of that inner scope.

To ensure memory safety, we need to keep ownership of the `TPM2B_NONCE`
while the call is being made.

Signed-off-by: Ionut Mihalcea <[email protected]>

Author: ionut-arm

tss-esapi/src/context/tpm_commands/session_commands.rs

@@ -59,6 +59,7 @@ impl Context {
         auth_hash: HashingAlgorithm,
     ) -> Result<Option<AuthSession>> {
         let mut session_handle = ObjectHandle::None.into();
+        let potential_tpm2b_nonce = nonce.map(|v| v.into());
         let ret = unsafe {
             Esys_StartAuthSession(
                 self.mut_context(),
@@ -70,7 +71,7 @@ impl Context {
                 self.optional_session_1(),
                 self.optional_session_2(),
                 self.optional_session_3(),
-                nonce.map_or_else(null, |v| &v.into()),
+                potential_tpm2b_nonce.as_ref().map_or_else(null, |v| v),
                 session_type.into(),
                 &symmetric.try_into()?,
                 auth_hash.into(),