refactor the mail setup scripts

As the scripts keep growing, it's time to split them up to
keep them understandable.

This splits mail.sh into mail-postfix.sh, mail-dovecot.sh,
and mail-users.sh, which has all of the user database-related
configurations shared by Dovecot and Postfix. Also from
spamassassin.sh the core sieve configuration is moved into
mail-dovecot.sh and the virtual transport setting is moved
into mail-postfix.sh.

Also revising one of the sed scripts in mail-dovecot to
not insert a new additional # at the start of a line each
time the script is run.

setup/mail-users.sh

@@ -0,0 +1,106 @@
+#!/bin/bash
+#
+# User Authentication and Destination Validation
+#
+# This script configures user authentication for Dovecot
+# and Postfix (which relies on Dovecot) and destination
+# validation by quering an Sqlite3 database of mail users. 
+
+source setup/functions.sh # load our functions
+source /etc/mailinabox.conf # load global vars
+
+# The database of mail users (i.e. authenticated users, who have mailboxes)
+# and aliases (forwarders).
+
+db_path=$STORAGE_ROOT/mail/users.sqlite
+
+# Create an empty database if it doesn't yet exist.
+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);" | sqlite3 $db_path;
+	echo "CREATE TABLE aliases (id INTEGER PRIMARY KEY AUTOINCREMENT, source TEXT NOT NULL UNIQUE, destination TEXT NOT NULL);" | sqlite3 $db_path;
+fi
+
+# User Authentication
+#####################
+
+# Have Dovecot query our database, and not system users, for authentication.
+sed -i "s/#*\(\!include auth-system.conf.ext\)/#\1/"  /etc/dovecot/conf.d/10-auth.conf
+sed -i "s/#\(\!include auth-sql.conf.ext\)/\1/"  /etc/dovecot/conf.d/10-auth.conf
+
+# Specify how the database is to be queried for user authentication (passdb)
+# and where user mailboxes are stored (userdb).
+cat > /etc/dovecot/conf.d/auth-sql.conf.ext << EOF;
+passdb {
+  driver = sql
+  args = /etc/dovecot/dovecot-sql.conf.ext
+}
+userdb {
+  driver = static
+  args = uid=mail gid=mail home=$STORAGE_ROOT/mail/mailboxes/%d/%n
+}
+EOF
+
+# Configure the SQL to query for a user's password.
+cat > /etc/dovecot/dovecot-sql.conf.ext << EOF;
+driver = sqlite
+connect = $db_path
+default_pass_scheme = SHA512-CRYPT
+password_query = SELECT email as user, password FROM users WHERE email='%u';
+EOF
+chmod 0600 /etc/dovecot/dovecot-sql.conf.ext # per Dovecot instructions
+
+# Have Dovecot provide an authorization service that Postfix can access & use.
+# Drew Crawford sets the auth-worker process to run as the mail user, but we don't care if it runs as root.
+cat > /etc/dovecot/conf.d/99-local-auth.conf << EOF;
+service auth {
+  unix_listener /var/spool/postfix/private/auth {
+    mode = 0666
+    user = postfix
+    group = postfix
+  }
+}
+EOF
+
+# And have Postfix use that service.
+tools/editconf.py /etc/postfix/main.cf \
+	smtpd_sasl_type=dovecot \
+	smtpd_sasl_path=private/auth \
+	smtpd_sasl_auth_enable=yes
+
+# Destination Validation
+########################
+
+# Use a Sqlite3 database to check whether a destination email address exists,
+# and to perform any email alias rewrites in Postfix.
+tools/editconf.py /etc/postfix/main.cf \
+	virtual_mailbox_domains=sqlite:/etc/postfix/virtual-mailbox-domains.cf \
+	virtual_mailbox_maps=sqlite:/etc/postfix/virtual-mailbox-maps.cf \
+	virtual_alias_maps=sqlite:/etc/postfix/virtual-alias-maps.cf \
+	local_recipient_maps=\$virtual_mailbox_maps
+
+# SQL statement to check if we handle mail for a domain, either for users or aliases.
+cat > /etc/postfix/virtual-mailbox-domains.cf << EOF;
+dbpath=$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.
+cat > /etc/postfix/virtual-mailbox-maps.cf << EOF;
+dbpath=$db_path
+query = SELECT 1 FROM users WHERE email='%s'
+EOF
+
+# SQL statement to rewrite an email address if an alias is present.
+cat > /etc/postfix/virtual-alias-maps.cf << EOF;
+dbpath=$db_path
+query = SELECT destination FROM aliases WHERE source='%s'
+EOF
+
+# Restart Services
+##################
+
+service postfix restart
+service dovecot restart
+
+