fix: handle unicode redirect payloads in dapp transport

.changeset/fresh-redirects-dance.md

@@ -0,0 +1,5 @@
+---
+'@0xsequence/dapp-client': patch
+---
+
+Fix redirect transport payload encoding so Unicode characters are handled correctly in redirect requests and responses.

packages/wallet/dapp-client/src/DappTransport.ts

@@ -14,9 +14,26 @@ import {
 
 const isBrowserEnvironment = typeof window !== 'undefined' && typeof document !== 'undefined'
 
+const bytesToBinaryString = (bytes: Uint8Array) => {
+  let binary = ''
+  const chunkSize = 0x8000
+  for (let i = 0; i < bytes.length; i += chunkSize) {
+    binary += String.fromCharCode(...bytes.subarray(i, i + chunkSize))
+  }
+  return binary
+}
+
+const binaryStringToBytes = (value: string) => {
+  const bytes = new Uint8Array(value.length)
+  for (let i = 0; i < value.length; i += 1) {
+    bytes[i] = value.charCodeAt(i)
+  }
+  return bytes
+}
+
 const base64Encode = (value: string) => {
-  if (typeof btoa !== 'undefined') {
-    return btoa(value)
+  if (typeof btoa !== 'undefined' && typeof TextEncoder !== 'undefined') {
+    return btoa(bytesToBinaryString(new TextEncoder().encode(value)))
   }
   if (typeof Buffer !== 'undefined') {
     return Buffer.from(value, 'utf-8').toString('base64')
@@ -25,8 +42,13 @@ const base64Encode = (value: string) => {
 }
 
 const base64Decode = (value: string) => {
-  if (typeof atob !== 'undefined') {
-    return atob(value)
+  if (typeof atob !== 'undefined' && typeof TextDecoder !== 'undefined') {
+    const decoded = atob(value)
+    try {
+      return new TextDecoder('utf-8', { fatal: true }).decode(binaryStringToBytes(decoded))
+    } catch {
+      return decoded
+    }
   }
   if (typeof Buffer !== 'undefined') {
     return Buffer.from(value, 'base64').toString('utf-8')

packages/wallet/dapp-client/test/DappTransport.test.ts

@@ -0,0 +1,89 @@
+import { describe, expect, it } from 'vitest'
+
+import { DappTransport } from '../src/DappTransport.js'
+import { TransportMode } from '../src/types/index.js'
+
+const encodeBase64Utf8 = (value: string) => {
+  let binary = ''
+  for (const byte of new TextEncoder().encode(value)) {
+    binary += String.fromCharCode(byte)
+  }
+  return btoa(binary)
+}
+
+const decodeBase64Utf8 = (value: string) => {
+  const binary = atob(value)
+  const bytes = new Uint8Array(binary.length)
+  for (let i = 0; i < binary.length; i += 1) {
+    bytes[i] = binary.charCodeAt(i)
+  }
+  return new TextDecoder().decode(bytes)
+}
+
+const createSessionStorage = () => {
+  const values = new Map<string, string>()
+  return {
+    getItem: (key: string) => values.get(key) ?? null,
+    setItem: (key: string, value: string) => {
+      values.set(key, value)
+    },
+    removeItem: (key: string) => {
+      values.delete(key)
+    },
+  }
+}
+
+describe('DappTransport redirect URLs', () => {
+  it('encodes unicode payloads as UTF-8 base64', async () => {
+    const transport = new DappTransport('https://wallet.example', TransportMode.REDIRECT, {}, createSessionStorage())
+    const payload = { message: 'Sign in to Sequence 🌍' }
+
+    const redirectUrl = await transport.getRequestRedirectUrl('signMessage', payload, 'https://dapp.example/callback')
+    const encodedPayload = new URL(redirectUrl).searchParams.get('payload')
+
+    if (!encodedPayload) {
+      throw new Error('Expected redirect URL to include a payload')
+    }
+    expect(JSON.parse(decodeBase64Utf8(encodedPayload))).toEqual(payload)
+  })
+
+  it('decodes unicode redirect response payloads', async () => {
+    const storage = createSessionStorage()
+    const transport = new DappTransport('https://wallet.example', TransportMode.REDIRECT, {}, storage)
+    const requestUrl = await transport.getRequestRedirectUrl('signMessage', {}, 'https://dapp.example/callback')
+    const id = new URL(requestUrl).searchParams.get('id')
+    const payload = { message: 'Signed by Sequence 🌍' }
+    const responseUrl = new URL('https://dapp.example/callback')
+
+    if (!id) {
+      throw new Error('Expected redirect URL to include an id')
+    }
+    responseUrl.searchParams.set('id', id)
+    responseUrl.searchParams.set('payload', encodeBase64Utf8(JSON.stringify(payload)))
+
+    await expect(transport.getRedirectResponse(false, responseUrl.toString())).resolves.toEqual({
+      action: 'signMessage',
+      payload,
+    })
+  })
+
+  it('decodes legacy Latin-1 redirect response payloads', async () => {
+    const storage = createSessionStorage()
+    const transport = new DappTransport('https://wallet.example', TransportMode.REDIRECT, {}, storage)
+    const requestUrl = await transport.getRequestRedirectUrl('signMessage', {}, 'https://dapp.example/callback')
+    const id = new URL(requestUrl).searchParams.get('id')
+    const payload = { message: 'Signed by Sequence Café' }
+    const responseUrl = new URL('https://dapp.example/callback')
+
+    if (!id) {
+      throw new Error('Expected redirect URL to include an id')
+    }
+    responseUrl.searchParams.set('id', id)
+    responseUrl.searchParams.set('payload', btoa(JSON.stringify(payload)))
+
+    await expect(transport.getRedirectResponse(false, responseUrl.toString())).resolves.toEqual({
+      action: 'signMessage',
+      payload,
+    })
+  })
+})