From 087e9b8a2986b5b38f97f2938d1e418b3460751c Mon Sep 17 00:00:00 2001
From: Chris Duncan <chris@zoso.dev>
Date: Thu, 30 Apr 2026 13:06:05 -0700
Subject: [PATCH] Check for existing signature when signing blocks.

---
 src/lib/block.ts       | 3 +++
 src/lib/ledger.ts      | 3 +++
 src/lib/wallet/sign.ts | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/src/lib/block.ts b/src/lib/block.ts
index f59b040..69b59e3 100644
--- a/src/lib/block.ts
+++ b/src/lib/block.ts
@@ -411,6 +411,9 @@ export class Block {
 				'NotAllowedError'
 			)
 		}
+		if (this.signature !== undefined) {
+			throw new TypeError('Block signature already exists', { cause: this.signature })
+		}
 		if (typeof input === 'string' && /^[A-F0-9]{128}$/i.test(input)) {
 			this.signature = input
 			return this
diff --git a/src/lib/ledger.ts b/src/lib/ledger.ts
index 4f517b7..433668d 100644
--- a/src/lib/ledger.ts
+++ b/src/lib/ledger.ts
@@ -570,6 +570,9 @@ export class Ledger {
 	* @returns {Promise} Status, signature, and block hash
 	*/
 	static async #signBlock (index: number, block: Block): Promise<LedgerSignResponse> {
+		if (block.signature !== undefined) {
+			throw new TypeError('Block signature already exists', { cause: block.signature })
+		}
 		return this.#enqueue(async () => {
 			try {
 				if (typeof index !== 'number' || index < 0 || index >= HARDENED_OFFSET) {
diff --git a/src/lib/wallet/sign.ts b/src/lib/wallet/sign.ts
index 5b5d000..ce9f756 100644
--- a/src/lib/wallet/sign.ts
+++ b/src/lib/wallet/sign.ts
@@ -19,6 +19,9 @@ export async function _signBlock (wallet: Wallet, vault: Vault, index: unknown,
 		if (!(block instanceof Block)) {
 			throw new TypeError('Invalid Block', { cause: block })
 		}
+		if (block.signature !== undefined) {
+			throw new TypeError('Block signature already exists', { cause: block.signature })
+		}
 		if (wallet.type === 'Ledger') {
 			if (frontier instanceof Block) {
 				try {
-- 
2.47.3