F-9768: rot: scrub NV auth and session state at exit

The TPM NV auth copy and the HMAC session state lived on the
stack until process teardown. Zeroize both at the common exit
label after the TPM device is unloaded, on success and error
paths alike.

tools/tpm/rot.c

@@ -204,6 +204,11 @@ exit:
     wolfTPM2_UnloadHandle(&dev, &tpmSession.handle);
     wolfTPM2_Cleanup(&dev);
 
+    /* Scrub the NV auth copy and the session state from the stack on
+     * every exit path. */
+    wc_ForceZero(&nv, sizeof(nv));
+    wc_ForceZero(&tpmSession, sizeof(tpmSession));
+
     return rc;
 }