Add the ability to override the sender header of email via SMTP (#1657)

* Add the ability to override the sender header of email via SMTP with the `MAILSENDER_ADDR` config value
* Closes #1644

CTFd/config.ini

@@ -84,6 +84,14 @@ MAIL_TLS =
 # Whether to connect to the SMTP server over SSL
 MAIL_SSL =
 
+# MAILSENDER_ADDR
+# The email address that is responsible for the transmission of emails.
+# This is very often the MAILFROM_ADDR value but can be specified if your email
+# is delivered by a different domain than what's specified in your MAILFROM_ADDR.
+# If this isn't specified, the MAILFROM_ADDR value is used.
+# It is fairly rare to need to set this value.
+MAILSENDER_ADDR =
+
 # MAILGUN_API_KEY
 # Mailgun API key to send email over Mailgun. As of CTFd v3, Mailgun integration is deprecated.
 # Installations using the Mailgun API should migrate over to SMTP settings.

CTFd/config.py

@@ -147,6 +147,8 @@ class ServerConfig(object):
 
     MAIL_SSL: bool = process_boolean_str(config_ini["email"]["MAIL_SSL"])
 
+    MAILSENDER_ADDR: str = empty_str_cast(config_ini["email"]["MAILSENDER_ADDR"])
+
     MAILGUN_API_KEY: str = empty_str_cast(config_ini["email"]["MAILGUN_API_KEY"])
 
     MAILGUN_BASE_URL: str = empty_str_cast(config_ini["email"]["MAILGUN_API_KEY"])

CTFd/utils/email/smtp.py

@@ -56,7 +56,15 @@ def sendmail(addr, text, subject):
         msg["From"] = mailfrom_addr
         msg["To"] = addr
 
-        smtp.send_message(msg)
+        # Check whether we are using an admin-defined SMTP server
+        custom_smtp = bool(get_config("mail_server"))
+
+        # We should only consider the MAILSENDER_ADDR value on servers defined in config
+        if custom_smtp:
+            smtp.send_message(msg)
+        else:
+            mailsender_addr = get_app_config("MAILSENDER_ADDR")
+            smtp.send_message(msg, from_addr=mailsender_addr)
 
         smtp.quit()
         return True, "Email sent"