bug/tnc: fix braavos sig verification

src/app/api/tnc/signUser/route.ts

@@ -3,7 +3,8 @@
 import { LATEST_TNC_DOC_VERSION, SIGNING_DATA } from '@/constants';
 import { db } from '@/db';
 import { standariseAddress } from '@/utils';
-import { Account, RpcProvider } from 'starknet';
+import { Account, CallData, RpcProvider, stark } from 'starknet';
+import { toBigInt } from 'ethers';
 
 export async function POST(req: Request) {
   const { address, signature } = await req.json();
@@ -45,7 +46,8 @@
 
   console.log(`Verifying signature for address: ${parsedAddress}`);
   try {
-    isValid = await myAccount.verifyMessage(SIGNING_DATA, parsedSignature);
+    const hash = await myAccount.hashMessage(SIGNING_DATA);
+    isValid = await verifyMessageHash(myAccount, hash, parsedSignature);
     console.log('isValid', isValid);
   } catch (error) {
     console.log('verification failed:', error);
@@ -98,3 +100,44 @@
     user: updatedUser,
   });
 }
+
+async function verifyMessageHash(
+  account: Account,
+  hash: string,
+  signature: string[],
+  entrypoint = 'isValidSignature',
+) {
+  try {
+    const resp = await account.callContract({
+      contractAddress: account.address,
+      entrypoint,
+      calldata: CallData.compile({
+        hash: toBigInt(hash).toString(),
+        signature: stark.formatSignature(signature),
+      }),
+    });
+    if (Number(resp[0]) == 0) {
+      return false;
+    }
+    return true;
+  } catch (err: any) {
+    if (entrypoint === 'isValidSignature') {
+      console.warn(
+        'could be Invalid message selector, trying with is_valid_signature',
+      );
+      return verifyMessageHash(account, hash, signature, 'is_valid_signature');
+    }
+
+    if (
+      [
+        'argent/invalid-signature',
+        'is invalid, with respect to the public key',
+      ].some((errMessage) => err.message.includes(errMessage))
+    ) {
+      return false;
+    }
+    throw Error(
+      `Signature verification request is rejected by the network: ${err}`,
+    );
+  }
+}

src/components/TncModal.tsx

@@ -5,7 +5,6 @@ import { addressAtom } from '@/store/claims.atoms';
 import {
   Button,
   Center,
-  Link,
   Modal,
   ModalBody,
   ModalContent,
@@ -101,9 +100,12 @@ const TncModal: React.FC<TncModalProps> = (props) => {
     setIsSigningPending(true);
 
     try {
-      const signature = (await account.signMessage(SIGNING_DATA)) as string[];
+      const _signature = (await account.signMessage(SIGNING_DATA)) as string[];
 
-      console.log('signature', signature);
+      console.log('signature', _signature);
+      const sig_len = _signature.length;
+      const signature =
+        sig_len > 2 ? _signature.slice(sig_len - 2, sig_len) : _signature;
       if (signature && signature.length > 0) {
         const res2 = await axios.post('/api/tnc/signUser', {
           address,
@@ -154,15 +156,17 @@ const TncModal: React.FC<TncModalProps> = (props) => {
             signing. You are required to sign this to continue using the App.
           </Text>
 
-          <Text textAlign="left" width={'100%'} fontWeight={'bold'}>
-            <Link
-              href={SIGNING_DATA.message.document}
-              color="white"
-              target="_blank"
-              _hover={{ textDecor: 'underline' }}
-            >
-              T&C Document link <ExternalLinkIcon />
-            </Link>
+          <Text
+            textAlign="left"
+            as={'a'}
+            width={'100%'}
+            fontWeight={'bold'}
+            href={SIGNING_DATA.message.document}
+            color="white"
+            target="_blank"
+            _hover={{ textDecor: 'underline' }}
+          >
+            T&C Document link <ExternalLinkIcon />
           </Text>
 
           <Text textAlign="left" width={'100%'}>