Add XOAUTH2 authenticator

NEWS.md

@@ -1,4 +1,9 @@
 # NEWS
+## Unreleased
+
+### Improvements
+
+* Add XOAUTH2 authenticator <https://github.com/ruby/net-smtp/pull/47>
 
 ## Version 0.3.3 (2022-10-29)
 

lib/net/smtp.rb

@@ -857,6 +857,20 @@ def auth_login(user, secret)
       res
     end
 
+    def auth_xoauth2(user, oauth2_token)
+      check_auth_args user, oauth2_token
+
+      auth_string = build_oauth2_string(user, oauth2_token)
+      res = send_xoauth2(base64_encode(auth_string))
+
+      if res.continue?
+        res = get_final_status
+      end
+
+      check_auth_response res
+      res
+    end
+
     def auth_cram_md5(user, secret)
       check_auth_args user, secret
       res = critical {
@@ -915,6 +929,22 @@ def cram_secret(secret, mask)
       buf
     end
 
+    def send_xoauth2(auth_token)
+      critical {
+        get_response("AUTH XOAUTH2 #{auth_token}")
+      }
+    end
+
+    def build_oauth2_string(user, oauth2_token)
+      format("user=%s\1auth=Bearer %s\1\1", user, oauth2_token)
+    end
+
+    def get_final_status
+      critical {
+        get_response("")
+      }
+    end
+
     #
     # SMTP command dispatcher
     #

test/net/smtp/test_smtp.rb

@@ -151,6 +151,23 @@ def test_unsucessful_auth_plain
       assert_equal "535", err.response.status
     end
 
+    def test_auth_xoauth2
+      sock = FakeSocket.new("235 2.7.0 Authentication successful\r\n")
+      smtp = Net::SMTP.new 'localhost', 25
+      smtp.instance_variable_set :@socket, sock
+      assert smtp.auth_xoauth2("foo", "bar").success?
+      assert_equal "AUTH XOAUTH2 dXNlcj1mb28BYXV0aD1CZWFyZXIgYmFyAQE=\r\n", sock.write_io.string
+    end
+
+    def test_unsucessful_auth_xoauth2
+      sock = FakeSocket.new("535 5.7.8 BadCredentials\r\n")
+      smtp = Net::SMTP.new 'localhost', 25
+      smtp.instance_variable_set :@socket, sock
+      err = assert_raise(Net::SMTPAuthenticationError) { smtp.auth_xoauth2("foo", "bar") }
+      assert_equal "535 5.7.8 BadCredentials\n", err.message
+      assert_equal "535", err.response.status
+    end
+
     def test_auth_login
       sock = FakeSocket.new("334 VXNlcm5hbWU6\r\n334 UGFzc3dvcmQ6\r\n235 2.7.0 Authentication successful\r\n")
       smtp = Net::SMTP.new 'localhost', 25