bidirectional alias controls: a new permitted_senders column in the aliases...

bidirectional alias controls: a new permitted_senders column in the aliases table allows setting who can send as an address independently of where the address forwards to

But the default permitted senders are the same as the addresses the alias forwards to.

Merge branch 'dhpiggott-bidirectional-alias-controls'

management/daemon.py

@@ -185,14 +185,15 @@ def mail_aliases():
 	if request.args.get("format", "") == "json":
 		return json_response(get_mail_aliases_ex(env))
 	else:
-		return "".join(x+"\t"+y+"\n" for x, y in get_mail_aliases(env))
+		return "".join(address+"\t"+receivers+"\t"+(senders or "")+"\n" for address, receivers, senders in get_mail_aliases(env))
 
 @app.route('/mail/aliases/add', methods=['POST'])
 @authorized_personnel_only
 def mail_aliases_add():
 	return add_mail_alias(
-		request.form.get('source', ''),
-		request.form.get('destination', ''),
+		request.form.get('address', ''),
+		request.form.get('forwards_to', ''),
+		request.form.get('permitted_senders', ''),
 		env,
 		update_if_exists=(request.form.get('update_if_exists', '') == '1')
 		)
@@ -200,7 +201,7 @@ def mail_aliases_add():
 @app.route('/mail/aliases/remove', methods=['POST'])
 @authorized_personnel_only
 def mail_aliases_remove():
-	return remove_mail_alias(request.form.get('source', ''), env)
+	return remove_mail_alias(request.form.get('address', ''), env)
 
 @app.route('/mail/domains')
 @authorized_personnel_only

management/status_checks.py

@@ -351,11 +351,14 @@ def check_primary_hostname_dns(domain, env, output, dns_domains, dns_zonefiles):
 	check_alias_exists("Hostmaster contact address", "hostmaster@" + domain, env, output)
 
 def check_alias_exists(alias_name, alias, env, output):
-	mail_alises = dict(get_mail_aliases(env))
-	if alias in mail_alises:
-		output.print_ok("%s exists as a mail alias. [%s ↦ %s]" % (alias_name, alias, mail_alises[alias]))
+	mail_aliases = dict([(address, receivers) for address, receivers, *_ in get_mail_aliases(env)])
+	if alias in mail_aliases:
+		if mail_aliases[alias]:
+			output.print_ok("%s exists as a mail alias. [%s ↦ %s]" % (alias_name, alias, mail_aliases[alias]))
 		else:
-		output.print_error("""You must add a mail alias for %s and direct email to you or another administrator.""" % alias)
+			output.print_error("""You must set the destination of the mail alias for %s to direct email to you or another administrator.""" % alias)
+	else:
+		output.print_error("""You must add a mail alias for %s which directs email to you or another administrator.""" % alias)
 
 def check_dns_zone(domain, env, output, dns_zonefiles):
 	# If a DS record is set at the registrar, check DNSSEC first because it will affect the NS query.
@@ -492,7 +495,7 @@ def check_mail_domain(domain, env, output):
 
 	# Check that the postmaster@ email address exists. Not required if the domain has a
 	# catch-all address or domain alias.
-	if "@" + domain not in dict(get_mail_aliases(env)):
+	if "@" + domain not in [address for address, *_ in get_mail_aliases(env)]:
 		check_alias_exists("Postmaster contact address", "postmaster@" + domain, env, output)
 
 	# Stop if the domain is listed in the Spamhaus Domain Block List.

setup/mail-users.sh

@@ -21,7 +21,7 @@ db_path=$STORAGE_ROOT/mail/users.sqlite
 if [ ! -f $db_path ]; then
 	echo Creating new user database: $db_path;
 	echo "CREATE TABLE users (id INTEGER PRIMARY KEY AUTOINCREMENT, email TEXT NOT NULL UNIQUE, password TEXT NOT NULL, extra, privileges TEXT NOT NULL DEFAULT '');" | sqlite3 $db_path;
-	echo "CREATE TABLE aliases (id INTEGER PRIMARY KEY AUTOINCREMENT, source TEXT NOT NULL UNIQUE, destination TEXT NOT NULL);" | sqlite3 $db_path;
+	echo "CREATE TABLE aliases (id INTEGER PRIMARY KEY AUTOINCREMENT, source TEXT NOT NULL UNIQUE, destination TEXT NOT NULL, permitted_senders TEXT);" | sqlite3 $db_path;
 fi
 
 # ### User Authentication
@@ -71,18 +71,23 @@ tools/editconf.py /etc/postfix/main.cf \
 
 # ### Sender Validation
 
-# Use a Sqlite3 database to set login maps. This is used with
-# reject_authenticated_sender_login_mismatch to see if user is
-# allowed to send mail using FROM field specified in the request.
+# We use Postfix's reject_authenticated_sender_login_mismatch filter to
+# prevent intra-domain spoofing by logged in but untrusted users in outbound
+# email. In all outbound mail (the sender has authenticated), the MAIL FROM
+# address (aka envelope or return path address) must be "owned" by the user
+# who authenticated. An SQL query will find who are the owners of any given
+# address.
 tools/editconf.py /etc/postfix/main.cf \
 	smtpd_sender_login_maps=sqlite:/etc/postfix/sender-login-maps.cf
 
-# SQL statement to set login map which includes the case when user is
-# sending email using a valid alias.
-# This is the same as virtual-alias-maps.cf, See below
+# Postfix will query the exact address first, where the priority will be alias
+# records first, then user records. If there are no matches for the exact
+# address, then Postfix will query just the domain part, which we call
+# catch-alls and domain aliases. A NULL permitted_senders column means to
+# take the value from the destination column.
 cat > /etc/postfix/sender-login-maps.cf << EOF;
 dbpath=$db_path
-query = SELECT destination from (SELECT destination, 0 as priority FROM aliases WHERE source='%s' UNION SELECT email as destination, 1 as priority FROM users WHERE email='%s') ORDER BY priority LIMIT 1;
+query = SELECT permitted_senders FROM (SELECT permitted_senders, 0 AS priority FROM aliases WHERE source='%s' AND permitted_senders IS NOT NULL UNION SELECT destination AS permitted_senders, 1 AS priority FROM aliases WHERE source='%s' AND permitted_senders IS NULL UNION SELECT email as permitted_senders, 2 AS priority FROM users WHERE email='%s') ORDER BY priority LIMIT 1;
 EOF
 
 # ### Destination Validation
@@ -95,13 +100,13 @@ tools/editconf.py /etc/postfix/main.cf \
 	virtual_alias_maps=sqlite:/etc/postfix/virtual-alias-maps.cf \
 	local_recipient_maps=\$virtual_mailbox_maps
 
-# SQL statement to check if we handle mail for a domain, either for users or aliases.
+# SQL statement to check if we handle incoming mail for a domain, either for users or aliases.
 cat > /etc/postfix/virtual-mailbox-domains.cf << EOF;
 dbpath=$db_path
 query = SELECT 1 FROM users WHERE email LIKE '%%@%s' UNION SELECT 1 FROM aliases WHERE source LIKE '%%@%s'
 EOF
 
-# SQL statement to check if we handle mail for a user.
+# SQL statement to check if we handle incoming mail for a user.
 cat > /etc/postfix/virtual-mailbox-maps.cf << EOF;
 dbpath=$db_path
 query = SELECT 1 FROM users WHERE email='%s'
@@ -127,9 +132,13 @@ EOF
 # might be returned by the UNION, so the whole query is wrapped in
 # another select that prioritizes the alias definition to preserve
 # postfix's preference for aliases for whole email addresses.
+#
+# Since we might have alias records with an empty destination because
+# it might have just permitted_senders, skip any records with an
+# empty destination here so that other lower priority rules might match.
 cat > /etc/postfix/virtual-alias-maps.cf << EOF;
 dbpath=$db_path
-query = SELECT destination from (SELECT destination, 0 as priority FROM aliases WHERE source='%s' UNION SELECT email as destination, 1 as priority FROM users WHERE email='%s') ORDER BY priority LIMIT 1;
+query = SELECT destination from (SELECT destination, 0 as priority FROM aliases WHERE source='%s' AND destination<>'' UNION SELECT email as destination, 1 as priority FROM users WHERE email='%s') ORDER BY priority LIMIT 1;
 EOF
 
 # Restart Services

setup/migrate.py

@@ -101,6 +101,16 @@ def migration_8(env):
 	# a new key, which will be 2048 bits.
 	os.unlink(os.path.join(env['STORAGE_ROOT'], 'mail/dkim/mail.private'))
 
+def migration_9(env):
+	# Add a column to the aliases table to store permitted_senders,
+	# which is a list of user account email addresses that are
+	# permitted to send mail using this alias instead of their own
+	# address. This was motivated by the addition of #427 ("Reject
+	# outgoing mail if FROM does not match Login") - which introduced
+	# the notion of outbound permitted-senders.
+	db = os.path.join(env["STORAGE_ROOT"], 'mail/users.sqlite')
+	shell("check_call", ["sqlite3", db, "ALTER TABLE aliases ADD permitted_senders TEXT"])
+
 def get_current_migration():
 	ver = 0
 	while True:

tools/mail.py

@@ -120,10 +120,10 @@ elif sys.argv[1] == "alias" and len(sys.argv) == 2:
 	print(mgmt("/mail/aliases"))
 
 elif sys.argv[1] == "alias" and sys.argv[2] == "add" and len(sys.argv) == 5:
-	print(mgmt("/mail/aliases/add", { "source": sys.argv[3], "destination": sys.argv[4] }))
+	print(mgmt("/mail/aliases/add", { "address": sys.argv[3], "forwards_to": sys.argv[4] }))
 
 elif sys.argv[1] == "alias" and sys.argv[2] == "remove" and len(sys.argv) == 4:
-	print(mgmt("/mail/aliases/remove", { "source": sys.argv[3] }))
+	print(mgmt("/mail/aliases/remove", { "address": sys.argv[3] }))
 
 else:
 	print("Invalid command-line arguments.")