Implement smtp notify hook

Support notifications via direct SMTP server connection.
Uses Python (2.7.x or 3.4+) to communicate with SMTP server.

notify/smtp.sh

@@ -2,7 +2,103 @@
 
 # support smtp
 
+# This implementation uses Python (2 or 3), which is available in many environments.
+# If you don't have Python, try "mail" notification instead of "smtp".
+
+# SMTP_FROM="[email protected]"  # required
+# SMTP_TO="[email protected]"  # required
+# SMTP_HOST="smtp.example.com"  # required
+# SMTP_PORT="25"  # defaults to 25, 465 or 587 depending on SMTP_SECURE
+# SMTP_SECURE="none"  # one of "none", "ssl" (implicit TLS, TLS Wrapper), "tls" (explicit TLS, STARTTLS)
+# SMTP_USERNAME=""  # set if SMTP server requires login
+# SMTP_PASSWORD=""  # set if SMTP server requires login
+# SMTP_TIMEOUT="15"  # seconds for SMTP operations to timeout
+# SMTP_PYTHON="/path/to/python"  # defaults to system python3 or python
+
 smtp_send() {
+  # Find a Python interpreter:
+  SMTP_PYTHON="${SMTP_PYTHON:-$(_readaccountconf_mutable SMTP_PYTHON)}"
+  if [ "$SMTP_PYTHON" ]; then
+    if _exists "$SMTP_PYTHON"; then
+      _saveaccountconf_mutable SMTP_PYTHON "$SMTP_PYTHON"
+    else
+      _err "SMTP_PYTHON '$SMTP_PYTHON' does not exist."
+      return 1
+    fi
+  else
+    # No SMTP_PYTHON setting; try to run default Python.
+    # (This is not saved with the conf.)
+    if _exists python3; then
+      SMTP_PYTHON="python3"
+    elif _exists python; then
+      SMTP_PYTHON="python"
+    else
+      _err "Can't locate Python interpreter; please define SMTP_PYTHON."
+      return 1
+    fi
+  fi
+  _debug "SMTP_PYTHON" "$SMTP_PYTHON"
+  _debug "Python version" "$($SMTP_PYTHON --version 2>&1)"
+
+  # Validate other settings:
+  SMTP_FROM="${SMTP_FROM:-$(_readaccountconf_mutable SMTP_FROM)}"
+  if [ -z "$SMTP_FROM" ]; then
+    _err "You must define SMTP_FROM as the sender email address."
+    return 1
+  fi
+
+  SMTP_TO="${SMTP_TO:-$(_readaccountconf_mutable SMTP_TO)}"
+  if [ -z "$SMTP_TO" ]; then
+    _err "You must define SMTP_TO as the recipient email address."
+    return 1
+  fi
+
+  SMTP_HOST="${SMTP_HOST:-$(_readaccountconf_mutable SMTP_HOST)}"
+  if [ -z "$SMTP_HOST" ]; then
+    _err "You must define SMTP_HOST as the SMTP server hostname."
+    return 1
+  fi
+  SMTP_PORT="${SMTP_PORT:-$(_readaccountconf_mutable SMTP_PORT)}"
+
+  SMTP_SECURE="${SMTP_SECURE:-$(_readaccountconf_mutable SMTP_SECURE)}"
+  SMTP_SECURE="${SMTP_SECURE:-none}"
+  case "$SMTP_SECURE" in
+    "none") SMTP_DEFAULT_PORT="25";;
+    "ssl")  SMTP_DEFAULT_PORT="465";;
+    "tls")  SMTP_DEFAULT_PORT="587";;
+    *)
+      _err "Invalid SMTP_SECURE='$SMTP_SECURE'. It must be 'ssl', 'tls' or 'none'."
+      return 1
+      ;;
+  esac
+
+  SMTP_USERNAME="${SMTP_USERNAME:-$(_readaccountconf_mutable SMTP_USERNAME)}"
+  SMTP_PASSWORD="${SMTP_PASSWORD:-$(_readaccountconf_mutable SMTP_PASSWORD)}"
+
+  SMTP_TIMEOUT="${SMTP_TIMEOUT:-$(_readaccountconf_mutable SMTP_TIMEOUT)}"
+  SMTP_DEFAULT_TIMEOUT="15"
+
+  _saveaccountconf_mutable SMTP_FROM "$SMTP_FROM"
+  _saveaccountconf_mutable SMTP_TO "$SMTP_TO"
+  _saveaccountconf_mutable SMTP_HOST "$SMTP_HOST"
+  _saveaccountconf_mutable SMTP_PORT "$SMTP_PORT"
+  _saveaccountconf_mutable SMTP_SECURE "$SMTP_SECURE"
+  _saveaccountconf_mutable SMTP_USERNAME "$SMTP_USERNAME"
+  _saveaccountconf_mutable SMTP_PASSWORD "$SMTP_PASSWORD"
+  _saveaccountconf_mutable SMTP_TIMEOUT "$SMTP_TIMEOUT"
+
+  # Send the message:
+  if ! _smtp_send "$@"; then
+    _err "$smtp_send_output"
+    return 1
+  fi
+
+  return 0
+}
+
+# _send subject content statuscode
+# Send the message via Python using SMTP_* settings
+_smtp_send() {
   _subject="$1"
   _content="$2"
   _statusCode="$3" #0: success, 1: error 2($RENEW_SKIP): skipped
@@ -10,6 +106,91 @@ smtp_send() {
   _debug "_content" "$_content"
   _debug "_statusCode" "$_statusCode"
 
-  _err "Not implemented yet."
-  return 1
+  _debug "SMTP_FROM" "$SMTP_FROM"
+  _debug "SMTP_TO" "$SMTP_TO"
+  _debug "SMTP_HOST" "$SMTP_HOST"
+  _debug "SMTP_PORT" "$SMTP_PORT"
+  _debug "SMTP_DEFAULT_PORT" "$SMTP_DEFAULT_PORT"
+  _debug "SMTP_SECURE" "$SMTP_SECURE"
+  _debug "SMTP_USERNAME" "$SMTP_USERNAME"
+  _secure_debug "SMTP_PASSWORD" "$SMTP_PASSWORD"
+  _debug "SMTP_TIMEOUT" "$SMTP_TIMEOUT"
+  _debug "SMTP_DEFAULT_TIMEOUT" "$SMTP_DEFAULT_TIMEOUT"
+
+  if [ "${DEBUG:-$DEBUG_LEVEL_NONE}" -ge "$DEBUG_LEVEL_2" ]; then
+    # Output the SMTP server dialogue. (Note this will include SMTP_PASSWORD!)
+    smtp_debug="True"
+  else
+    smtp_debug=""
+  fi
+
+  # language=Python
+  smtp_send_output="$($SMTP_PYTHON <<EOF
+# This code is meant to work with either Python 2.7.x or Python 3.4+.
+try:
+    try:
+        from email.message import EmailMessage
+    except ImportError:
+        from email.mime.text import MIMEText as EmailMessage  # Python 2
+    from smtplib import SMTP, SMTP_SSL, SMTPException
+    from socket import error as SocketError
+except ImportError as err:
+    print("A required Python standard package is missing. This system may have"
+          " a reduced version of Python unsuitable for sending mail: %s" % err)
+    exit(1)
+
+smtp_debug = """$smtp_debug""" == "True"
+
+smtp_host = """$SMTP_HOST"""
+smtp_port = int("""${SMTP_PORT:-$SMTP_DEFAULT_PORT}""")
+smtp_secure = """$SMTP_SECURE"""
+username = """$SMTP_USERNAME"""
+password = """$SMTP_PASSWORD"""
+timeout=int("""${SMTP_TIMEOUT:-$SMTP_DEFAULT_TIMEOUT}""")  # seconds
+
+from_email="""$SMTP_FROM"""
+to_emails="""$SMTP_TO"""  # can be comma-separated
+subject="""$_subject"""
+content="""$_content"""
+
+try:
+    msg = EmailMessage()
+    msg.set_content(content)
+except (AttributeError, TypeError):
+    # Python 2 MIMEText
+    msg = EmailMessage(content)
+msg["Subject"] = subject
+msg["From"] = from_email
+msg["To"] = to_emails
+
+smtp = None
+try:
+    if smtp_secure == "ssl":
+        smtp = SMTP_SSL(smtp_host, smtp_port, timeout=timeout)
+    else:
+        smtp = SMTP(smtp_host, smtp_port, timeout=timeout)
+    smtp.set_debuglevel(smtp_debug)
+    if smtp_secure == "tls":
+        smtp.starttls()
+    if username or password:
+        smtp.login(username, password)
+    smtp.sendmail(msg["From"], msg["To"].split(","), msg.as_string())
+
+except SMTPException as err:
+    # Output just the error (skip the Python stack trace) for SMTP errors
+    print("Error sending: %r" % err)
+    exit(1)
+
+except SocketError as err:
+    print("Error connecting to %s:%d: %r" % (smtp_host, smtp_port, err))
+    exit(1)
+
+finally:
+    if smtp is not None:
+        smtp.quit()
+EOF
+)"
+  _ret=$?
+  _debug "smtp_send_output" "$smtp_send_output"
+  return "$_ret"
 }