feat(base_layer): basic contract constitution validation (#4232)

Description
---
* New DAN base layer validator for contract constitutions, checks that:
    * The definition for the contract must be published beforehand
    * There is no other constitution already published for that contract
* Refactored some redundant helper code for validations

Motivation and Context
---
The base layer should check the basic requirements of a valid contract constitution: the definition must already be published and there are no duplicated constitutions.

How Has This Been Tested?
---
* New unit tests to check the new validations
* The existing unit and integration tests pass

base_layer/core/src/validation/dan_validators/acceptance_validator.rs

@@ -22,7 +22,7 @@
 
 use tari_common_types::types::PublicKey;
 
-use super::helpers::{get_contract_constitution, get_sidechain_features, validate_output_type};
+use super::helpers::{fetch_contract_constitution, get_sidechain_features, validate_output_type};
 use crate::{
     chain_storage::{BlockchainBackend, BlockchainDatabase},
     transactions::transaction_components::{
@@ -48,7 +48,7 @@ pub fn validate_acceptance<B: BlockchainBackend>(
     let acceptance_features = get_contract_acceptance(sidechain_features)?;
     let validator_node_public_key = &acceptance_features.validator_node_public_key;
 
-    let constitution = get_contract_constitution(db, contract_id)?;
+    let constitution = fetch_contract_constitution(db, contract_id)?;
 
     validate_public_key(constitution, validator_node_public_key)?;
 

base_layer/core/src/validation/dan_validators/constitution_validator.rs

@@ -0,0 +1,123 @@
+//  Copyright 2022, The Tari Project
+//
+//  Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
+//  following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
+//  disclaimer.
+//
+//  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
+//  following disclaimer in the documentation and/or other materials provided with the distribution.
+//
+//  3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
+//  products derived from this software without specific prior written permission.
+//
+//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+//  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+//  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+//  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+//  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+//  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use tari_common_types::types::FixedHash;
+use tari_utilities::hex::Hex;
+
+use super::helpers::{fetch_contract_features, get_sidechain_features, validate_output_type};
+use crate::{
+    chain_storage::{BlockchainBackend, BlockchainDatabase},
+    transactions::transaction_components::{OutputType, TransactionOutput},
+    validation::ValidationError,
+};
+
+pub fn validate_constitution<B: BlockchainBackend>(
+    db: &BlockchainDatabase<B>,
+    output: &TransactionOutput,
+) -> Result<(), ValidationError> {
+    validate_output_type(output, OutputType::ContractConstitution)?;
+
+    let sidechain_features = get_sidechain_features(output)?;
+    let contract_id = sidechain_features.contract_id;
+
+    validate_definition_existence(db, contract_id)?;
+    validate_duplication(db, contract_id)?;
+
+    Ok(())
+}
+
+fn validate_definition_existence<B: BlockchainBackend>(
+    db: &BlockchainDatabase<B>,
+    contract_id: FixedHash,
+) -> Result<(), ValidationError> {
+    match fetch_contract_features(db, contract_id, OutputType::ContractDefinition)? {
+        Some(_) => Ok(()),
+        None => {
+            let msg = format!(
+                "Contract definition not found for contract_id ({:?})",
+                contract_id.to_hex()
+            );
+            Err(ValidationError::DanLayerError(msg))
+        },
+    }
+}
+
+fn validate_duplication<B: BlockchainBackend>(
+    db: &BlockchainDatabase<B>,
+    contract_id: FixedHash,
+) -> Result<(), ValidationError> {
+    match fetch_contract_features(db, contract_id, OutputType::ContractConstitution)? {
+        Some(_) => {
+            let msg = format!(
+                "Duplicated contract constitution for contract_id ({:?})",
+                contract_id.to_hex()
+            );
+            Err(ValidationError::DanLayerError(msg))
+        },
+        None => Ok(()),
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use tari_common_types::types::FixedHash;
+
+    use crate::validation::dan_validators::test_helpers::{
+        assert_dan_error,
+        create_contract_constitution_schema,
+        init_test_blockchain,
+        publish_constitution,
+        publish_definition,
+        schema_to_transaction,
+    };
+
+    #[test]
+    fn definition_must_exist() {
+        // initialise a blockchain with enough funds to spend at contract transactions
+        let (blockchain, change) = init_test_blockchain();
+
+        // construct a transaction for a constitution, without a prior definition
+        let contract_id = FixedHash::default();
+        let schema = create_contract_constitution_schema(contract_id, change[2].clone(), Vec::new());
+        let (tx, _) = schema_to_transaction(&schema);
+
+        // try to validate the constitution transaction and check that we get the error
+        assert_dan_error(&blockchain, &tx, "Contract definition not found");
+    }
+
+    #[test]
+    fn it_rejects_duplicated_constitutions() {
+        // initialise a blockchain with enough funds to spend at contract transactions
+        let (mut blockchain, change) = init_test_blockchain();
+
+        // publish the contract definition and constitution into a block
+        let contract_id = publish_definition(&mut blockchain, change[0].clone());
+        publish_constitution(&mut blockchain, change[1].clone(), contract_id);
+
+        // construct a transaction for the duplicated contract constitution
+        let schema = create_contract_constitution_schema(contract_id, change[2].clone(), Vec::new());
+        let (tx, _) = schema_to_transaction(&schema);
+
+        // try to validate the duplicated constitution transaction and check that we get the error
+        assert_dan_error(&blockchain, &tx, "Duplicated contract constitution");
+    }
+}

base_layer/core/src/validation/dan_validators/definition_validator.rs

@@ -23,7 +23,7 @@
 use tari_common_types::types::FixedHash;
 use tari_utilities::hex::Hex;
 
-use super::helpers::{get_sidechain_features, validate_output_type};
+use super::helpers::{fetch_contract_features, get_sidechain_features, validate_output_type};
 use crate::{
     chain_storage::{BlockchainBackend, BlockchainDatabase},
     transactions::transaction_components::{OutputType, TransactionOutput},
@@ -48,20 +48,16 @@ fn validate_duplication<B: BlockchainBackend>(
     db: &BlockchainDatabase<B>,
     contract_id: FixedHash,
 ) -> Result<(), ValidationError> {
-    let outputs = db
-        .fetch_contract_outputs_by_contract_id_and_type(contract_id, OutputType::ContractDefinition)
-        .map_err(|err| ValidationError::DanLayerError(format!("Could not search outputs: {}", err)))?;
-
-    let is_duplicated = !outputs.is_empty();
-    if is_duplicated {
-        let msg = format!(
-            "Duplicated contract definition for contract_id ({:?})",
-            contract_id.to_hex()
-        );
-        return Err(ValidationError::DanLayerError(msg));
+    match fetch_contract_features(db, contract_id, OutputType::ContractDefinition)? {
+        Some(_) => {
+            let msg = format!(
+                "Duplicated contract definition for contract_id ({:?})",
+                contract_id.to_hex()
+            );
+            Err(ValidationError::DanLayerError(msg))
+        },
+        None => Ok(()),
     }
-
-    Ok(())
 }
 
 #[cfg(test)]

base_layer/core/src/validation/dan_validators/helpers.rs

@@ -21,6 +21,7 @@
 //  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 use tari_common_types::types::FixedHash;
+use tari_utilities::hex::Hex;
 
 use crate::{
     chain_storage::{BlockchainBackend, BlockchainDatabase},
@@ -44,59 +45,51 @@ pub fn validate_output_type(
     Ok(())
 }
 
-pub fn get_sidechain_features(output: &TransactionOutput) -> Result<&SideChainFeatures, ValidationError> {
-    match output.features.sidechain_features.as_ref() {
-        Some(features) => Ok(features),
-        None => Err(ValidationError::DanLayerError(
-            "Sidechain features not found".to_string(),
-        )),
-    }
-}
-
-pub fn get_contract_constitution<B: BlockchainBackend>(
+pub fn fetch_contract_features<B: BlockchainBackend>(
     db: &BlockchainDatabase<B>,
     contract_id: FixedHash,
-) -> Result<ContractConstitution, ValidationError> {
-    let contract_outputs = db
-        .fetch_contract_outputs_by_contract_id_and_type(contract_id, OutputType::ContractConstitution)
-        .unwrap();
-
-    if contract_outputs.is_empty() {
-        return Err(ValidationError::DanLayerError(
-            "Contract constitution not found".to_string(),
-        ));
+    output_type: OutputType,
+) -> Result<Option<SideChainFeatures>, ValidationError> {
+    let outputs = db
+        .fetch_contract_outputs_by_contract_id_and_type(contract_id, output_type)
+        .map_err(|err| ValidationError::DanLayerError(format!("Could not search outputs: {}", err)))?;
+    if outputs.is_empty() {
+        return Ok(None);
     }
 
-    // we assume that only one constitution should be present in the blockchain for any given contract
-    // TODO: create a validation to avoid duplicated constitution publishing
-    let utxo_info = match contract_outputs.first() {
+    let utxo_info = match outputs.first() {
         Some(value) => value,
-        None => {
-            return Err(ValidationError::DanLayerError(
-                "Contract constitution UtxoMindInfo not found".to_string(),
-            ))
-        },
+        None => return Ok(None),
     };
 
-    let constitution_output = match utxo_info.output.as_transaction_output() {
+    let transaction_output = match utxo_info.output.as_transaction_output() {
         Some(value) => value,
-        None => {
-            return Err(ValidationError::DanLayerError(
-                "Contract constitution output not found".to_string(),
-            ))
-        },
+        None => return Ok(None),
     };
 
-    let constitution_features = match constitution_output.features.sidechain_features.as_ref() {
+    match transaction_output.features.sidechain_features.as_ref() {
+        Some(value) => Ok(Some(value.clone())),
+        None => Ok(None),
+    }
+}
+
+pub fn fetch_contract_constitution<B: BlockchainBackend>(
+    db: &BlockchainDatabase<B>,
+    contract_id: FixedHash,
+) -> Result<ContractConstitution, ValidationError> {
+    let features_result = fetch_contract_features(db, contract_id, OutputType::ContractConstitution)?;
+
+    let features = match features_result {
         Some(value) => value,
         None => {
-            return Err(ValidationError::DanLayerError(
-                "Contract constitution output features not found".to_string(),
-            ))
+            return Err(ValidationError::DanLayerError(format!(
+                "Contract constitution not found for contract_id {}",
+                contract_id.to_hex()
+            )))
         },
     };
 
-    let constitution = match constitution_features.constitution.as_ref() {
+    let constitution = match features.constitution.as_ref() {
         Some(value) => value,
         None => {
             return Err(ValidationError::DanLayerError(
@@ -107,3 +100,12 @@ pub fn get_contract_constitution<B: BlockchainBackend>(
 
     Ok(constitution.clone())
 }
+
+pub fn get_sidechain_features(output: &TransactionOutput) -> Result<&SideChainFeatures, ValidationError> {
+    match output.features.sidechain_features.as_ref() {
+        Some(features) => Ok(features),
+        None => Err(ValidationError::DanLayerError(
+            "Sidechain features not found".to_string(),
+        )),
+    }
+}

base_layer/core/src/validation/dan_validators/mod.rs

@@ -29,6 +29,9 @@ use crate::{
 mod acceptance_validator;
 use acceptance_validator::validate_acceptance;
 
+mod constitution_validator;
+use constitution_validator::validate_constitution;
+
 mod definition_validator;
 use definition_validator::validate_definition;
 
@@ -54,6 +57,7 @@ impl<B: BlockchainBackend> MempoolTransactionValidation for TxDanLayerValidator<
         for output in tx.body().outputs() {
             match output.features.output_type {
                 OutputType::ContractDefinition => validate_definition(&self.db, output)?,
+                OutputType::ContractConstitution => validate_constitution(&self.db, output)?,
                 OutputType::ContractValidatorAcceptance => validate_acceptance(&self.db, output)?,
                 _ => continue,
             }

base_layer/core/src/validation/dan_validators/test_helpers.rs

@@ -74,6 +74,11 @@ pub fn publish_definition(blockchain: &mut TestBlockchain, change: UnblindedOutp
     contract_id
 }
 
+pub fn publish_constitution(blockchain: &mut TestBlockchain, change: UnblindedOutput, contract_id: FixedHash) {
+    let schema = create_contract_constitution_schema(contract_id, change, Vec::new());
+    create_block(blockchain, "constitution", schema);
+}
+
 pub fn schema_to_transaction(schema: &TransactionSchema) -> (Transaction, Vec<UnblindedOutput>) {
     let mut utxos = Vec::new();