fix: disallow contract registration in pxe of contract with duplicate…

… private function selectors (#9773)

Related to #4433

This PR adds pretty naive validation when adding a contract artifact to
the pxe database. Specifically it rejects adding contract artifacts to
the PXE with duplicate private function selectors.

This also assumes the absence of partial artifacts.

yarn-project/pxe/src/database/contracts/contract_artifact_db.ts

@@ -9,6 +9,7 @@ export interface ContractArtifactDatabase {
    * Adds a new contract artifact to the database or updates an existing one.
    * @param id - Id of the corresponding contract class.
    * @param contract - Contract artifact to add.
+   * @throws - If there are duplicate private function selectors.
    */
   addContractArtifact(id: Fr, contract: ContractArtifact): Promise<void>;
   /**

yarn-project/pxe/src/database/kv_pxe_database.ts

@@ -15,7 +15,7 @@ import {
   SerializableContractInstance,
   computePoint,
 } from '@aztec/circuits.js';
-import { type ContractArtifact } from '@aztec/foundation/abi';
+import { type ContractArtifact, FunctionSelector, FunctionType } from '@aztec/foundation/abi';
 import { toBufferBE } from '@aztec/foundation/bigint-buffer';
 import { Fr } from '@aztec/foundation/fields';
 import {
@@ -142,6 +142,19 @@ export class KVPxeDatabase implements PxeDatabase {
   }
 
   public async addContractArtifact(id: Fr, contract: ContractArtifact): Promise<void> {
+    const privateSelectors = contract.functions
+      .filter(functionArtifact => functionArtifact.functionType === FunctionType.PRIVATE)
+      .map(privateFunctionArtifact =>
+        FunctionSelector.fromNameAndParameters(
+          privateFunctionArtifact.name,
+          privateFunctionArtifact.parameters,
+        ).toString(),
+      );
+
+    if (privateSelectors.length !== new Set(privateSelectors).size) {
+      throw new Error('Repeated function selectors of private functions');
+    }
+
     await this.#contractArtifacts.set(id.toString(), contractArtifactToBuffer(contract));
   }
 

yarn-project/pxe/src/database/pxe_database_test_suite.ts

@@ -8,9 +8,11 @@ import {
   computePoint,
 } from '@aztec/circuits.js';
 import { makeHeader } from '@aztec/circuits.js/testing';
+import { FunctionType } from '@aztec/foundation/abi';
 import { randomInt } from '@aztec/foundation/crypto';
 import { Fr, Point } from '@aztec/foundation/fields';
 import { BenchmarkingContractArtifact } from '@aztec/noir-contracts.js/Benchmarking';
+import { TestContractArtifact } from '@aztec/noir-contracts.js/Test';
 
 import { IncomingNoteDao } from './incoming_note_dao.js';
 import { OutgoingNoteDao } from './outgoing_note_dao.js';
@@ -439,6 +441,19 @@ export function describePxeDatabase(getDatabase: () => PxeDatabase) {
         await expect(database.getContractArtifact(id)).resolves.toEqual(artifact);
       });
 
+      it('does not store a contract artifact with a duplicate private function selector', async () => {
+        const artifact = TestContractArtifact;
+        const index = artifact.functions.findIndex(fn => fn.functionType === FunctionType.PRIVATE);
+
+        const copiedFn = structuredClone(artifact.functions[index]);
+        artifact.functions.push(copiedFn);
+
+        const id = Fr.random();
+        await expect(database.addContractArtifact(id, artifact)).rejects.toThrow(
+          'Repeated function selectors of private functions',
+        );
+      });
+
       it('stores a contract instance', async () => {
         const address = AztecAddress.random();
         const instance = SerializableContractInstance.random().withAddress(address);