add recoverPublicKeyFromMetadata util

packages/status-js/src/client.ts

@@ -22,6 +22,7 @@ import { Account } from './account'
 import { idToContentTopic } from './contentTopic'
 import { createSymKeyFromPassword } from './encryption'
 import { payloadToId } from './utils/payload-to-id'
+import { recoverPublicKeyFromMetadata } from './utils/recover-public-key-from-metadata'
 import { CommunityDescription } from './wire/community_description'
 
 import type { WakuMessage } from 'js-waku'
@@ -246,6 +247,13 @@ class Community {
       return
     }
 
+    try {
+      const pk = recoverPublicKeyFromMetadata(decodedMetadata)
+      console.log('pk', pk)
+    } catch (err) {
+      console.error(err)
+    }
+
     console.log('MESSAGE: DECODED METADATA')
 
     let shouldUpdate = false

packages/status-js/src/utils/recover-public-key-from-metadata.test.ts

@@ -0,0 +1,10 @@
+import { recoverPublicKeyFromMetadata } from './recover-public-key-from-metadata'
+
+import type { ApplicationMetadataMessage } from '~/protos/application-metadata-message'
+
+describe('TODO: recoverPublicKeyFromMetadata', () => {
+  it('should recover public key', async () => {
+    const metadata: ApplicationMetadataMessage = {}
+    expect(recoverPublicKeyFromMetadata(metadata)).toEqual({})
+  })
+})

packages/status-js/src/utils/recover-public-key-from-metadata.ts

@@ -0,0 +1,25 @@
+import { keccak256 } from 'ethereum-cryptography/keccak'
+import { recoverPublicKey } from 'ethereum-cryptography/secp256k1'
+import { bytesToHex } from 'ethereum-cryptography/utils'
+
+import type { ApplicationMetadataMessage } from '../../protos/application-metadata-message'
+
+/**
+ * returns the public key of the signer
+ * msg must be the  32-byte keccak hash of the message to be signed.
+ * sig must be a 65-byte compact ECDSA signature containing the recovery id as the last element.
+ */
+export function recoverPublicKeyFromMetadata(
+  metadata: ApplicationMetadataMessage
+): string {
+  const signature = metadata.signature.slice(0, 64)
+  const recoveryId = metadata.signature.slice(-1)
+
+  const pk = recoverPublicKey(
+    keccak256(metadata.payload),
+    signature,
+    Number(recoveryId)
+  )
+
+  return bytesToHex(pk)
+}