feat: add sha256 and hmac_sha256 filters for cryptographic operations (#889)

src/build/crypto-impl-browser.ts

@@ -0,0 +1,27 @@
+function bufferToHex (buffer: ArrayBuffer): string {
+  const bytes = new Uint8Array(buffer)
+  let hex = ''
+  for (let i = 0; i < bytes.length; i++) {
+    hex += bytes[i].toString(16).padStart(2, '0')
+  }
+  return hex
+}
+
+export async function sha256 (str: string): Promise<string> {
+  const data = new TextEncoder().encode(str)
+  const digest = await crypto.subtle.digest('SHA-256', data)
+  return bufferToHex(digest)
+}
+
+export async function hmacSha256 (str: string, key: string): Promise<string> {
+  const encoder = new TextEncoder()
+  const cryptoKey = await crypto.subtle.importKey(
+    'raw',
+    encoder.encode(key),
+    { name: 'HMAC', hash: 'SHA-256' },
+    false,
+    ['sign']
+  )
+  const signature = await crypto.subtle.sign('HMAC', cryptoKey, encoder.encode(str))
+  return bufferToHex(signature)
+}