feat: Cap Nonce to Slot# of the transaction. | NPG-000 (#712)

# Description

Prevents an extraordinarily large Nonce from eclipsing other later
registrations.


## Checklist

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: kukkok3 <[email protected]>

src/voting-tools-rs/src/data/mod.rs

@@ -225,14 +225,15 @@ impl RawRegistration {
         &self,
         cddl_config: &CddlConfig,
         network_id: NetworkId,
+        slot_no: SlotNo,
     ) -> Result<SignedRegistration, Box<dyn Error>> {
         // validate cddl: 61284
         validate_reg_cddl(&self.bin_reg, cddl_config)?;
 
         // validate cddl: 61285
         validate_sig_cddl(&self.bin_sig, cddl_config)?;
 
-        let registration = self.raw_reg_conversion(network_id)?;
+        let registration = self.raw_reg_conversion(network_id, slot_no)?;
 
         let signature = self.raw_sig_conversion()?;
 
@@ -245,7 +246,11 @@ impl RawRegistration {
         })
     }
 
-    fn raw_reg_conversion(&self, network_id: NetworkId) -> Result<Registration, Box<dyn Error>> {
+    fn raw_reg_conversion(
+        &self,
+        network_id: NetworkId,
+        slot_no: SlotNo,
+    ) -> Result<Registration, Box<dyn Error>> {
         let decoded: ciborium::value::Value =
             ciborium::de::from_reader(Cursor::new(&self.bin_reg))?;
 
@@ -283,7 +288,14 @@ impl RawRegistration {
 
         // A nonce that identifies that most recent delegation
         let nonce = match inspect_nonce(metamap) {
-            Ok(value) => value,
+            Ok(value) => {
+                if value.0 < slot_no.0 {
+                    // Don't allow nonce > slot number
+                    value
+                } else {
+                    Nonce(slot_no.0)
+                }
+            }
             Err(value) => return value,
         };
 

src/voting-tools-rs/src/verification/verify.rs

@@ -100,7 +100,7 @@ pub fn filter_registrations(
         };
 
         // deserialize the raw Binary CBOR.
-        let reg = match rawreg.to_signed(&cddl, network_id) {
+        let reg = match rawreg.to_signed(&cddl, network_id, SlotNo(slot as u64)) {
             Err(err) => {
                 invalids.push(InvalidRegistration {
                     spec_61284: Some(prefix_hex(&rawreg.bin_reg)),