From 54f3bedf38a2fe4c1a03e979e5f0503e0f8db367 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Sat, 2 Sep 2023 17:31:39 -0500
Subject: [PATCH] verifySignature: return `false` if the id is invalid

---
 event.test.ts | 23 ++++++++++++++++++++++-
 event.ts      |  8 +++++++-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/event.test.ts b/event.test.ts
index 625447a..ca19e8c 100644
--- a/event.test.ts
+++ b/event.test.ts
@@ -278,6 +278,27 @@ describe('Event', () => {
 
       expect(isValid).toEqual(false)
     })
+
+    it('should return false for an invalid event id', () => {
+      const privateKey = 'd217c1ff2f8a65c3e3a1740db3b9f58b8c848bb45e26d00ed4714e4a0f4ceecf'
+
+      const event = finishEvent(
+        {
+          kind: 1,
+          tags: [],
+          content: 'Hello, world!',
+          created_at: 1617932115,
+        },
+        privateKey,
+      )
+
+      // tamper with the id
+      event.id = event.id.replace(/0/g, '1')
+
+      const isValid = verifySignature(event)
+
+      expect(isValid).toEqual(false)
+    })
   })
 
   describe('getSignature', () => {
@@ -296,9 +317,9 @@ describe('Event', () => {
       const sig = getSignature(unsignedEvent, privateKey)
 
       // verify the signature
-      // @ts-expect-error
       const isValid = verifySignature({
         ...unsignedEvent,
+        id: getEventHash(unsignedEvent),
         sig,
       })
 
diff --git a/event.ts b/event.ts
index e0440fb..75dc650 100644
--- a/event.ts
+++ b/event.ts
@@ -115,8 +115,14 @@ export function validateEvent<T>(event: T): event is T & UnsignedEvent<number> {
 /** Verify the event's signature. This function mutates the event with a `verified` symbol, making it idempotent. */
 export function verifySignature<K extends number>(event: Event<K>): event is VerifiedEvent<K> {
   if (typeof event[verifiedSymbol] === 'boolean') return event[verifiedSymbol]
+
+  const hash = getEventHash(event)
+  if (hash !== event.id) {
+    return false
+  }
+
   try {
-    event[verifiedSymbol] = schnorr.verify(event.sig, getEventHash(event), event.pubkey)
+    event[verifiedSymbol] = schnorr.verify(event.sig, hash, event.pubkey)
     return event[verifiedSymbol]
   } catch (err) {
     return false