From e9c4474b83cdc82d61d448479eecef7938b28c8e Mon Sep 17 00:00:00 2001
From: Sean Tan <sean.tan.ly@gmail.com>
Date: Mon, 24 May 2021 20:42:28 +0800
Subject: [PATCH] fix(deprecation): :crypto.hmac -> :crypto.mac, Bitwise.^^^ ->
 Bitwise.bxor (#669)

---
 lib/stripe/webhook.ex        | 11 +++++++++--
 test/stripe/webhook_test.exs |  9 ++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/lib/stripe/webhook.ex b/lib/stripe/webhook.ex
index c5b61f58..024a6a74 100644
--- a/lib/stripe/webhook.ex
+++ b/lib/stripe/webhook.ex
@@ -116,10 +116,17 @@ defmodule Stripe.Webhook do
   end
 
   defp compute_signature(payload, secret) do
-    :crypto.hmac(:sha256, secret, payload)
+    hmac(:sha256, secret, payload)
     |> Base.encode16(case: :lower)
   end
 
+  # TODO: remove when we require OTP 22
+  if System.otp_release() >= "22" do
+    defp hmac(digest, key, data), do: :crypto.mac(:hmac, digest, key, data)
+  else
+    defp hmac(digest, key, data), do: :crypto.hmac(digest, key, data)
+  end
+
   defp secure_equals?(input, expected) when byte_size(input) == byte_size(expected) do
     input = String.to_charlist(input)
     expected = String.to_charlist(expected)
@@ -135,7 +142,7 @@ defmodule Stripe.Webhook do
     import Bitwise
 
     acc
-    |> bor(input_codepoint ^^^ expected_codepoint)
+    |> bor(bxor(input_codepoint, expected_codepoint))
     |> secure_compare(input, expected)
   end
 
diff --git a/test/stripe/webhook_test.exs b/test/stripe/webhook_test.exs
index b4c66c5b..53051458 100644
--- a/test/stripe/webhook_test.exs
+++ b/test/stripe/webhook_test.exs
@@ -11,10 +11,17 @@ defmodule Stripe.WebhookTest do
   @secret "secret"
 
   defp generate_signature(timestamp, payload, secret \\ @secret) do
-    :crypto.hmac(:sha256, secret, "#{timestamp}.#{payload}")
+    hmac(:sha256, secret, "#{timestamp}.#{payload}")
     |> Base.encode16(case: :lower)
   end
 
+  # TODO: remove when we require OTP 22
+  if System.otp_release() >= "22" do
+    defp hmac(digest, key, data), do: :crypto.mac(:hmac, digest, key, data)
+  else
+    defp hmac(digest, key, data), do: :crypto.hmac(digest, key, data)
+  end
+
   defp create_signature_header(timestamp, scheme, signature) do
     "t=#{timestamp},#{scheme}=#{signature}"
   end