feat: encode legacy signatures as script with one element

data_structures/src/transaction.rs

@@ -1,5 +1,6 @@
 use serde::{Deserialize, Serialize};
 
+use crate::stack::{Item, MyValue, ScriptError};
 use crate::{
     chain::{
         Block, Bn256PublicKey, DataRequestOutput, Epoch, Hash, Hashable, Input, KeyedSignature,
@@ -199,13 +200,22 @@ pub fn mint(tx: &Transaction) -> Option<&MintTransaction> {
 }
 
 pub fn vtt_signature_to_witness(ks: &KeyedSignature) -> Vec<u8> {
-    // TODO: it would be nice to encode KeyedSignature as a script
-    // This way vtt.witness is always a valid script
-    ks.to_pb_bytes().unwrap()
+    let script = vec![Item::Value(MyValue::from_signature(ks))];
+
+    crate::stack::encode(&script).unwrap()
 }
 
-pub fn vtt_witness_to_signature(witness: &[u8]) -> KeyedSignature {
-    KeyedSignature::from_pb_bytes(witness).unwrap()
+pub fn vtt_witness_to_signature(witness: &[u8]) -> Result<KeyedSignature, ScriptError> {
+    let script = crate::stack::decode(witness)?;
+
+    if script.len() != 1 {
+        return Err(ScriptError::InvalidSignature);
+    }
+
+    match &script[0] {
+        Item::Value(value) => value.to_signature(),
+        _ => Err(ScriptError::InvalidSignature),
+    }
 }
 
 #[derive(Debug, Default, Eq, PartialEq, Clone, Serialize, Deserialize, ProtobufConvert, Hash)]

src/cli/node/json_rpc_client.rs

@@ -904,21 +904,17 @@ pub fn sign_tx(
 
         match tx {
             Transaction::ValueTransfer(ref mut vtt) => {
-                let signature_bytes = signature.to_pb_bytes()?;
-                // TODO: this only works if the witness field represents a script
-                // It could also represent a signature in the case of normal value transfer
-                // transactions. It would be nice to also support signing normal transactions here
+                let signature_bytes = MyValue::from_signature(&signature);
+                // This also works with normal transactions, because the signature is encoded as a
+                // script with one element.
                 let mut script = witnet_data_structures::stack::decode(&vtt.witness[input_index])?;
 
                 println!(
                     "-----------------------\nPrevious witness:\n-----------------------\n{}",
                     witnet_data_structures::stack::parser::script_to_string(&script)
                 );
 
-                script.insert(
-                    signature_position_in_witness,
-                    Item::Value(MyValue::Bytes(signature_bytes)),
-                );
+                script.insert(signature_position_in_witness, Item::Value(signature_bytes));
 
                 println!(
                     "-----------------------\nNew witness:\n-----------------------\n{}",

validations/src/validations.rs

@@ -1243,7 +1243,7 @@ pub fn validate_transaction_signatures(
         if input.redeem_script.is_empty() {
             // Validate that public key hash of the pointed output matches public
             // key in the provided signature
-            let keyed_signature = vtt_witness_to_signature(witness);
+            let keyed_signature = vtt_witness_to_signature(witness)?;
             validate_pkh_signature(input, &keyed_signature, utxo_set).map_err(fte)?;
 
             // Validate the actual signature