Question

I’m looking for a tool that can take sendmail mailing lists (that is, text files that can be the target of :include: directives in the aliases file) and parse them to generate a list of recipients. The files could, of course, contain comments, recipients with “descriptive” names in addition to actual addresses, a mixture of external addresses and local users and other aliases, etc.

Does there exist either a tool to do this parsing, or a formal specification that would allow me to write one myself? Or will I have to write an ad-hoc one which is nearly certain to contain bugs?

I don’t have root access to the server I’m working on, so sendmail -bv doesn’t work. (Of course, I could always set up my own installation if I just needed to use it as a utility independent of the actual setup.) sendmail -bt does appear to work, but I’m not entirely sure how to use it.

Answer 1

Here is the Python code that I ultimately used to solve this problem. You would have to tweak it to work on a server configured differently from mine.

import os
import re
import subprocess

def find_recipients(usernames):
    recipients = {'local': set(), 'external': set(), 'missing_local': set(),
                  'file': set(), 'program': set(), 'error_messages': set()}
    visited_lists = set()
    sendmail = subprocess.Popen(('sendmail', '-bt'), stdin=subprocess.PIPE,
                                stdout=subprocess.PIPE)
    def handle_local_user(username):
        username = username.lower()
        list_path = '/shared/aliases/' + username
        if os.path.isfile(list_path):
            visit_list(list_path)
        elif os.path.isdir('/home/' + username):
            recipients['local'].add(username)
        else:
            recipients['missing_local'].add(username)
    def visit_list(list_path):
        if list_path not in visited_lists:
            visited_lists.add(list_path)
            with open(list_path, 'r') as ml_file:
                for ml_line in ml_file:
                    if not re.match(r'^\s*(#.*)?$', ml_line):
                        if not ml_line.endswith('\n'):
                            ml_line += '\n'
                        sendmail.stdin.write('/parse ' + ml_line)
                        sendmail.stdin.flush()
                        match = None
                        while match is None:
                            match = re.match(r'^mailer ([^,]*), (.*)\n$',
                                             sendmail.stdout.readline())
                        mailer, recipient_info = match.groups()
                        if mailer == 'local':
                            handle_local_user(
                                re.match(r'^user (.+)$',
                                         recipient_info).group(1))
                        elif mailer == 'relay':
                            user, at, domain = re.match(
                                r'^host smtp\.mydomain\.org, user (.*)$',
                                recipient_info).group(1).partition('@')
                            domain = domain.lower()
                            if domain == 'mydomain.org':
                                handle_local_user(user)
                            else:
                                recipients['external'].add(user + at + domain)
                        elif mailer == '*file*':
                            recipients['file'].add(
                                re.match(r'^user (.+)$',
                                         recipient_info).group(1))
                        elif mailer == 'prog':
                            recipients['program'].add(
                                re.match(r'^user (.+)$',
                                         recipient_info).group(1))
                        elif mailer == '*include*':
                            visit_list(re.match(r'^user (.+)$',
                                                recipient_info).group(1))
                        elif mailer == '*error*':
                            raise RuntimeError('address parsing error: ' +
                                               recipient_info)
                        else:
                            raise RuntimeError('unrecognized mailer: ' +
                                               mailer)
    for un in usernames:
        handle_local_user(un)
    sendmail.communicate('/quit')
    return recipients