Merge branch 'master' into ldap

CHANGELOG.md

@@ -1,6 +1,14 @@
 CHANGELOG
 =========
 
+In Development
+--------------
+
+Mail:
+
+* An MTA-STS policy for incoming mail is now published (in DNS and over HTTPS) when the primary hostname and email address domain both have a signed TLS certificate installed.
+* MTA-STS reporting is enabled with reports sent to administrator@ the primary hostname.
+
 v0.45 (May 16, 2020)
 --------------------
 

README.md

@@ -28,15 +28,20 @@ It is a one-click email appliance. There are no user-configurable setup options.
 
 The components installed are:
 
-* SMTP ([postfix](http://www.postfix.org/)), IMAP ([dovecot](http://dovecot.org/)), CardDAV/CalDAV ([Nextcloud](https://nextcloud.com/)), Exchange ActiveSync ([z-push](http://z-push.org/))
-* Webmail ([Roundcube](http://roundcube.net/)), static website hosting ([nginx](http://nginx.org/))
-* Spam filtering ([spamassassin](https://spamassassin.apache.org/)), greylisting ([postgrey](http://postgrey.schweikert.ch/))
-* DNS ([nsd4](https://www.nlnetlabs.nl/projects/nsd/)) with [SPF](https://en.wikipedia.org/wiki/Sender_Policy_Framework), DKIM ([OpenDKIM](http://www.opendkim.org/)), [DMARC](https://en.wikipedia.org/wiki/DMARC), [DNSSEC](https://en.wikipedia.org/wiki/DNSSEC), [DANE TLSA](https://en.wikipedia.org/wiki/DNS-based_Authentication_of_Named_Entities), and [SSHFP](https://tools.ietf.org/html/rfc4255) records automatically set
-* Backups ([duplicity](http://duplicity.nongnu.org/)), firewall ([ufw](https://launchpad.net/ufw)), intrusion protection ([fail2ban](http://www.fail2ban.org/wiki/index.php/Main_Page)), system monitoring ([munin](http://munin-monitoring.org/))
+* SMTP ([postfix](http://www.postfix.org/)), IMAP ([dovecot](http://dovecot.org/)), CardDAV/CalDAV ([Nextcloud](https://nextcloud.com/)), and Exchange ActiveSync ([z-push](http://z-push.org/)) servers
+* Webmail ([Roundcube](http://roundcube.net/)), mail filter rules (also using dovecot), email client autoconfig settings (served by [nginx](http://nginx.org/))
+* Spam filtering ([spamassassin](https://spamassassin.apache.org/)) and greylisting ([postgrey](http://postgrey.schweikert.ch/))
+* DNS ([nsd4](https://www.nlnetlabs.nl/projects/nsd/)) with [SPF](https://en.wikipedia.org/wiki/Sender_Policy_Framework), DKIM ([OpenDKIM](http://www.opendkim.org/)), [DMARC](https://en.wikipedia.org/wiki/DMARC), [DNSSEC](https://en.wikipedia.org/wiki/DNSSEC), [DANE TLSA](https://en.wikipedia.org/wiki/DNS-based_Authentication_of_Named_Entities), [MTA-STS](https://tools.ietf.org/html/rfc8461), and [SSHFP](https://tools.ietf.org/html/rfc4255) policy records automatically set
+* TLS certificates automatically provisioned [Let's Encrypt](https://letsencrypt.org/)
+* Backups ([duplicity](http://duplicity.nongnu.org/)), firewall ([ufw](https://launchpad.net/ufw)), intrusion protection ([fail2ban](http://www.fail2ban.org/wiki/index.php/Main_Page)), and basic system monitoring ([munin](http://munin-monitoring.org/))
 
-It also includes:
+It also includes system management tools:
 
-* A control panel and API for adding/removing mail users, aliases, custom DNS records, etc. and detailed system monitoring.
+* Comprehensive health monitoring that checks each day that services are running, ports are open, TLS certificates are valid, and DNS records are correct
+* A control panel for adding/removing mail users, aliases, custom DNS records, configuring backups, etc.
+* An API for all of the actions on the control panel
+
+It also supports static website hosting since the box is serving HTTPS anyway.
 
 For more information on how Mail-in-a-Box handles your privacy, see the [security details page](security.md).
 

conf/mta-sts.txt

@@ -0,0 +1,4 @@
+version: STSv1
+mode: MODE
+mx: PRIMARY_HOSTNAME
+max_age: 86400

conf/nginx-alldomains.conf

@@ -21,6 +21,9 @@
 	location = /mail/config-v1.1.xml {
 		alias /var/lib/mailinabox/mozilla-autoconfig.xml;
 	}
+	location = /.well-known/mta-sts.txt {
+		alias /var/lib/mailinabox/mta-sts.txt;
+	}
 
 	# Roundcube Webmail configuration.
 	rewrite ^/mail$ /mail/ redirect;

management/dns_update.py

@@ -9,8 +9,9 @@ import ipaddress
 import rtyaml
 import dns.resolver
 
-from mailconfig import get_mail_domains
+from mailconfig import get_mail_domains, get_mail_aliases
 from utils import shell, load_env_vars_from_file, safe_domain_name, sort_domains
+from ssl_certificates import get_ssl_certificates, check_certificate
 
 # From https://stackoverflow.com/questions/3026957/how-to-validate-a-domain-name-using-regex-php/16491074#16491074
 # This regular expression matches domain names according to RFCs, it also accepts fqdn with an leading dot,
@@ -304,6 +305,52 @@ def build_zone(domain, all_domains, additional_records, www_redirect_domains, en
 		if not has_rec(qname, rtype):
 			records.append((qname, rtype, value, explanation))
 
+	# If this is a domain name that there are email addresses configured for, i.e. "something@"
+	# this domain name, then the domain name is a MTA-STS (https://tools.ietf.org/html/rfc8461)
+	# Policy Domain.
+	#
+	# A "_mta-sts" TXT record signals the presence of a MTA-STS policy, and an effectively random policy
+	# ID is used to signal that a new policy may (or may not) be deployed any time the DNS is
+	# updated.
+	#
+	# The policy itself is served at the "mta-sts" (no underscore) subdomain over HTTPS. Therefore
+	# the TLS certificate used by Postfix for STARTTLS must be a valid certificate for the MX
+	# domain name (PRIMARY_HOSTNAME) *and* the TLS certificate used by nginx for HTTPS on the mta-sts
+	# subdomain must be valid certificate for that domain. Do not set an MTA-STS policy if either
+	# certificate in use is not valid (e.g. because it is self-signed and a valid certificate has not
+	# yet been provisioned).
+	mta_sts_enabled = False
+	if domain in get_mail_domains(env):
+		# Check that PRIMARY_HOSTNAME and the mta_sts domain both have valid certificates.
+		for d in (env['PRIMARY_HOSTNAME'], "mta-sts." + domain):
+			cert = get_ssl_certificates(env).get(d)
+			if not cert:
+				break # no certificate provisioned for this domain
+			cert_status = check_certificate(d, cert['certificate'], cert['private-key'])
+			if cert_status[0] != 'OK':
+				break # certificate is not valid
+		else:
+			# 'break' was not encountered above, so both domains are good
+			mta_sts_enabled = True
+	if mta_sts_enabled:
+		mta_sts_records = [
+			("mta-sts", "A", env["PUBLIC_IP"], "Optional. MTA-STS Policy Host serving /.well-known/mta-sts.txt."),
+			("mta-sts", "AAAA", env.get('PUBLIC_IPV6'), "Optional. MTA-STS Policy Host serving /.well-known/mta-sts.txt."),
+			("_mta-sts", "TXT", "v=STSv1; id=%sZ" % datetime.datetime.now().strftime("%Y%m%d%H%M%S"), "Optional. Part of the MTA-STS policy for incoming mail. If set, a MTA-STS policy must also be published.")
+		]
+		# Rules can be custom configured accoring to https://tools.ietf.org/html/rfc8460.
+		# Skip if the rules below if the user has set a custom _smtp._tls record.
+		if not has_rec("_smtp._tls", "TXT", prefix="v=TLSRPTv1;"):
+			tls_rpt_string = ""
+			tls_rpt_email = env.get("MTA_STS_TLSRPT_EMAIL", "postmaster@%s" % env['PRIMARY_HOSTNAME'])
+			if tls_rpt_email: # if a reporting address is not cleared
+				tls_rpt_string = " rua=mailto:%s" % tls_rpt_email
+			mta_sts_records.append(("_smtp._tls", "TXT", "v=TLSRPTv1;%s" % tls_rpt_string, "Optional. Enables MTA-STS reporting."))
+		for qname, rtype, value, explanation in mta_sts_records:
+			if value is None or value.strip() == "": continue # skip IPV6 if not set
+			if not has_rec(qname, rtype):
+				records.append((qname, rtype, value, explanation))
+
 	# Sort the records. The None records *must* go first in the nsd zone file. Otherwise it doesn't matter.
 	records.sort(key = lambda rec : list(reversed(rec[0].split(".")) if rec[0] is not None else ""))
 

management/ssl_certificates.py

@@ -183,7 +183,7 @@ def get_certificates_to_provision(env, limit_domains=None, show_valid_certs=True
 	# for and subtract:
 	# * domains not in limit_domains if limit_domains is not empty
 	# * domains with custom "A" records, i.e. they are hosted elsewhere
-	# * domains with actual "A" records that point elsewhere
+	# * domains with actual "A" records that point elsewhere (misconfiguration)
 	# * domains that already have certificates that will be valid for a while
 
 	from web_update import get_web_domains
@@ -259,15 +259,41 @@ def provision_certificates(env, limit_domains):
 			"result": "skipped",
 		})
 
+	# Break into groups by DNS zone: Group every domain with its parent domain, if
+	# its parent domain is in the list of domains to request a certificate for.
+	# Start with the zones so that if the zone doesn't need a certificate itself,
+	# its children will still be grouped together. Sort the provision domains to
+	# put parents ahead of children.
+	# Since Let's Encrypt requests are limited to 100 domains at a time,
+	# we'll create a list of lists of domains where the inner lists have
+	# at most 100 items. By sorting we also get the DNS zone domain as the first
+	# entry in each list (unless we overflow beyond 100) which ends up as the
+	# primary domain listed in each certificate.
+	from dns_update import get_dns_zones
+	certs = { }
+	for zone, zonefile in get_dns_zones(env):
+		certs[zone] = [[]]
+	for domain in sort_domains(domains, env):
+		# Does the domain end with any domain we've seen so far.
+		for parent in certs.keys():
+			if domain.endswith("." + parent):
+				# Add this to the parent's list of domains.
+				# Start a new group if the list already has
+				# 100 items.
+				if len(certs[parent][-1]) == 100:
+					certs[parent].append([])
+				certs[parent][-1].append(domain)
+				break
+		else:
+			# This domain is not a child of any domain we've seen yet, so
+			# start a new group. This shouldn't happen since every zone
+			# was already added.
+			certs[domain] = [[domain]]
 
-	# Break into groups of up to 100 certificates at a time, which is Let's Encrypt's
-	# limit for a single certificate. We'll sort to put related domains together.
-	max_domains_per_group = 100
-	domains = sort_domains(domains, env)
-	certs = []
-	while len(domains) > 0:
-		certs.append( domains[:max_domains_per_group] )
-		domains = domains[max_domains_per_group:]
+	# Flatten to a list of lists of domains (from a mapping). Remove empty
+	# lists (zones with no domains that need certs).
+	certs = sum(certs.values(), [])
+	certs = [_ for _ in certs if len(_) > 0]
 
 	# Prepare to provision.
 

management/status_checks.py

@@ -5,11 +5,13 @@
 # what to do next.
 
 import sys, os, os.path, re, subprocess, datetime, multiprocessing.pool
+import asyncio
 
 import dns.reversename, dns.resolver
 import dateutil.parser, dateutil.tz
 import idna
 import psutil
+import postfix_mta_sts_resolver.resolver
 
 from dns_update import get_dns_zones, build_tlsa_record, get_custom_dns_config, get_secondary_dns, get_custom_dns_records
 from web_update import get_web_domains, get_domains_with_a_records
@@ -309,6 +311,17 @@ def run_domain_checks(rounded_time, env, output, pool):
 
 	domains_to_check = mail_domains | dns_domains | web_domains
 
+	# Remove "www", "autoconfig", "autodiscover", and "mta-sts" subdomains, which we group with their parent,
+	# if their parent is in the domains to check list.
+	domains_to_check = [
+		d for d in domains_to_check
+		if not (
+		   d.split(".", 1)[0] in ("www", "autoconfig", "autodiscover", "mta-sts")
+		   and len(d.split(".", 1)) == 2
+		   and d.split(".", 1)[1] in domains_to_check
+		)
+	]
+
 	# Get the list of domains that we don't serve web for because of a custom CNAME/A record.
 	domains_with_a_records = get_domains_with_a_records(env)
 
@@ -327,6 +340,11 @@ def run_domain_checks(rounded_time, env, output, pool):
 def run_domain_checks_on_domain(domain, rounded_time, env, dns_domains, dns_zonefiles, mail_domains, web_domains, domains_with_a_records):
 	output = BufferedOutput()
 
+	# When running inside Flask, the worker threads don't get a thread pool automatically.
+	# Also this method is called in a forked worker pool, so creating a new loop is probably
+	# a good idea.
+	asyncio.set_event_loop(asyncio.new_event_loop())
+
 	# we'd move this up, but this returns non-pickleable values
 	ssl_certificates = get_ssl_certificates(env)
 
@@ -354,6 +372,26 @@ def run_domain_checks_on_domain(domain, rounded_time, env, dns_domains, dns_zone
 	if domain in dns_domains:
 		check_dns_zone_suggestions(domain, env, output, dns_zonefiles, domains_with_a_records)
 
+	# Check auto-configured subdomains. See run_domain_checks.
+	# Skip mta-sts because we check the policy directly.
+	for label in ("www", "autoconfig", "autodiscover"):
+		subdomain = label + "." + domain
+		if subdomain in web_domains or subdomain in mail_domains:
+			# Run checks.
+			subdomain_output = run_domain_checks_on_domain(subdomain, rounded_time, env, dns_domains, dns_zonefiles, mail_domains, web_domains, domains_with_a_records)
+
+			# Prepend the domain name to the start of each check line, and then add to the
+			# checks for this domain.
+			for attr, args, kwargs in subdomain_output[1].buf:
+				if attr == "add_heading":
+					# Drop the heading, but use its text as the subdomain name in
+					# each line since it is in Unicode form.
+					subdomain = args[0]
+					continue
+				if len(args) == 1 and isinstance(args[0], str):
+					args = [ subdomain + ": " + args[0] ]
+				getattr(output, attr)(*args, **kwargs)
+
 	return (domain, output)
 
 def check_primary_hostname_dns(domain, env, output, dns_domains, dns_zonefiles):
@@ -611,6 +649,19 @@ def check_mail_domain(domain, env, output):
 		if mx != recommended_mx:
 			good_news += "  This configuration is non-standard.  The recommended configuration is '%s'." % (recommended_mx,)
 		output.print_ok(good_news)
+
+		# Check MTA-STS policy.
+		loop = asyncio.get_event_loop()
+		sts_resolver = postfix_mta_sts_resolver.resolver.STSResolver(loop=loop)
+		valid, policy = loop.run_until_complete(sts_resolver.resolve(domain))
+		if valid == postfix_mta_sts_resolver.resolver.STSFetchResult.VALID:
+			if policy[1].get("mx") == [env['PRIMARY_HOSTNAME']] and policy[1].get("mode") == "enforce": # policy[0] is the policyid
+				output.print_ok("MTA-STS policy is present.")
+			else:
+				output.print_error("MTA-STS policy is present but has unexpected settings. [{}]".format(policy[1]))
+		else:
+			output.print_error("MTA-STS policy is missing: {}".format(valid))
+
 	else:
 		output.print_error("""This domain's DNS MX record is incorrect. It is currently set to '%s' but should be '%s'. Mail will not
 			be delivered to this box. It may take several hours for public DNS to update after a change. This problem may result from

management/web_update.py

@@ -33,6 +33,9 @@ def get_web_domains(env, include_www_redirects=True, exclude_dns_elsewhere=True,
 		domains |= set('autoconfig.' + maildomain for maildomain in get_mail_domains(env, category='mail'))
 		domains |= set('autodiscover.' + maildomain for maildomain in get_mail_domains(env, category='mail'))
 
+	# 'mta-sts.' for MTA-STS support.
+	domains |= set('mta-sts.' + maildomain for maildomain in get_mail_domains(env))
+
 	if exclude_dns_elsewhere:
 		# ...Unless the domain has an A/AAAA record that maps it to a different
 		# IP address than this box. Remove those domains from our list.

security.md

@@ -101,9 +101,13 @@ The box restricts the envelope sender address (also called the return path or MA
 Incoming Mail
 -------------
 
-### Encryption
+### Encryption Settings
 
-As discussed above, there is no way to require on-the-wire encryption of mail. When the box receives an incoming email (SMTP on port 25), it offers encryption (STARTTLS) but cannot require that senders use it because some senders may not support STARTTLS at all and other senders may support STARTTLS but not with the latest protocols/ciphers. To give senders the best chance at making use of encryption, the box offers protocols back to TLSv1 and ciphers with key lengths as low as 112 bits. Modern clients (senders) will make use of the 256-bit ciphers and Diffie-Hellman ciphers with a 2048-bit key for perfect forward secrecy, however. ([source](setup/mail-postfix.sh))
+As with outbound email, there is no way to require on-the-wire encryption of incoming mail from all senders. When the box receives an incoming email (SMTP on port 25), it offers encryption (STARTTLS) but cannot require that senders use it because some senders may not support STARTTLS at all and other senders may support STARTTLS but not with the latest protocols/ciphers. To give senders the best chance at making use of encryption, the box offers protocols back to TLSv1 and ciphers with key lengths as low as 112 bits. Modern clients (senders) will make use of the 256-bit ciphers and Diffie-Hellman ciphers with a 2048-bit key for perfect forward secrecy, however. ([source](setup/mail-postfix.sh))
+
+### MTA-STS
+
+The box publishes a SMTP MTA Strict Transport Security ([SMTP MTA-STS](https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol#SMTP_MTA_Strict_Transport_Security)) policy (via DNS and HTTPS) in "enforce" mode. Senders that support MTA-STS will use a secure SMTP connection. (MTA-STS tells senders to connect and expect a signed TLS certificate for the "MX" domain without permitting a fallback to an unencrypted connection.)
 
 ### DANE
 

setup/management.sh

@@ -50,7 +50,7 @@ hide_output $venv/bin/pip install --upgrade pip
 hide_output $venv/bin/pip install --upgrade \
 	rtyaml "email_validator>=1.0.0" "exclusiveprocess" \
 	flask dnspython python-dateutil \
-	"idna>=2.0.0" "cryptography==2.2.2" boto psutil ldap3
+	"idna>=2.0.0" "cryptography==2.2.2" boto psutil postfix-mta-sts-resolver ldap3
 
 # CONFIGURATION
 

setup/start.sh

@@ -82,9 +82,10 @@ if [ ! -f $STORAGE_ROOT/mailinabox.version ]; then
 	chown $STORAGE_USER.$STORAGE_USER $STORAGE_ROOT/mailinabox.version
 fi
 
-
 # Save the global options in /etc/mailinabox.conf so that standalone
-# tools know where to look for data.
+# tools know where to look for data. The default MTA_STS_MODE setting
+# is blank unless set by an environment variable, but see web.sh for
+# how that is interpreted.
 cat > /etc/mailinabox.conf << EOF;
 STORAGE_USER=$STORAGE_USER
 STORAGE_ROOT=$STORAGE_ROOT
@@ -93,6 +94,7 @@ PUBLIC_IP=$PUBLIC_IP
 PUBLIC_IPV6=$PUBLIC_IPV6
 PRIVATE_IP=$PRIVATE_IP
 PRIVATE_IPV6=$PRIVATE_IPV6
+MTA_STS_MODE=${MTA_STS_MODE-}
 EOF
 
 # Start service configuration.

setup/web.sh

@@ -19,7 +19,7 @@ fi
 
 echo "Installing Nginx (web server)..."
 
-apt_install nginx php-cli php-fpm
+apt_install nginx php-cli php-fpm idn2
 
 rm -f /etc/nginx/sites-enabled/default
 
@@ -122,6 +122,21 @@ cat conf/mozilla-autoconfig.xml \
 	 > /var/lib/mailinabox/mozilla-autoconfig.xml
 chmod a+r /var/lib/mailinabox/mozilla-autoconfig.xml
 
+# Create a generic mta-sts.txt file which is exposed via the
+# nginx configuration at /.well-known/mta-sts.txt
+# more documentation is available on: 
+# https://www.uriports.com/blog/mta-sts-explained/
+# default mode is "enforce". Change to "testing" which means
+# "Messages will be delivered as though there was no failure
+# but a report will be sent if TLS-RPT is configured" if you
+# are not sure you want this yet. Or "none".
+PUNY_PRIMARY_HOSTNAME=$(echo "$PRIMARY_HOSTNAME" | idn2)
+cat conf/mta-sts.txt \
+        | sed "s/MODE/${MTA_STS_MODE:-enforce}/" \
+        | sed "s/PRIMARY_HOSTNAME/$PUNY_PRIMARY_HOSTNAME/" \
+         > /var/lib/mailinabox/mta-sts.txt
+chmod a+r /var/lib/mailinabox/mta-sts.txt
+
 # make a default homepage
 if [ -d $STORAGE_ROOT/www/static ]; then mv $STORAGE_ROOT/www/static $STORAGE_ROOT/www/default; fi # migration #NODOC
 mkdir -p $STORAGE_ROOT/www/default
@@ -137,4 +152,3 @@ restart_service php7.2-fpm
 # Open ports.
 ufw_allow http
 ufw_allow https
-