feat: preSigningValidator

Author: ieow

src/interfaces.ts

@@ -495,3 +495,5 @@ export interface Secp256k1PrecomputedClient {
   client: Client;
   serverCoeffs: Record<string, string>;
 }
+
+export type PreSigningValidatorType = (params: { data: Uint8Array; hashed: boolean }) => Promise<{ success: boolean; error?: string; data?: string }>;

src/mpcCoreKit.ts

@@ -43,6 +43,7 @@ import {
   JWTLoginParams,
   MPCKeyDetails,
   OAuthLoginParams,
+  PreSigningValidatorType,
   Secp256k1PrecomputedClient,
   SessionData,
   SubVerifierDetailsParams,
@@ -99,6 +100,8 @@ export class Web3AuthMPCCoreKit implements ICoreKit {
 
   private atomicCallStackCounter: number = 0;
 
+  private preSigningValidator?: PreSigningValidatorType;
+
   constructor(options: Web3AuthOptions) {
     if (!options.web3AuthClientId) {
       throw CoreKitError.clientIdInvalid();
@@ -456,6 +459,10 @@ export class Web3AuthMPCCoreKit implements ICoreKit {
     }
   }
 
+  setPreSigningValidator(preSigningValidator: PreSigningValidatorType) {
+    this.preSigningValidator = preSigningValidator;
+  }
+
   public async handleRedirectResult(): Promise<void> {
     this.checkReady();
 
@@ -778,6 +785,12 @@ export class Web3AuthMPCCoreKit implements ICoreKit {
   }
 
   public async sign(data: Buffer, hashed: boolean = false, secp256k1Precompute?: Secp256k1PrecomputedClient): Promise<Buffer> {
+    if (this.preSigningValidator) {
+      const result = await this.preSigningValidator({ data, hashed });
+      if (!result.success || result.error) {
+        throw Error(result.error);
+      }
+    }
     this.wasmLib = await this.loadTssWasm();
     if (this.keyType === KeyType.secp256k1) {
       const sig = await this.sign_ECDSA_secp256k1(data, hashed, secp256k1Precompute);