#!/bin/bash # OpenDKIM # -------- # # OpenDKIM provides a service that puts a DKIM signature on outbound mail. # # The DNS configuration for DKIM is done in the management daemon. source setup/functions.sh # load our functions source /etc/mailinabox.conf # load global vars # Install DKIM... echo Installing OpenDKIM/OpenDMARC... apt_install opendkim opendkim-tools opendmarc # Make sure configuration directories exist. mkdir -p /etc/opendkim; mkdir -p $STORAGE_ROOT/mail/dkim # Used in InternalHosts and ExternalIgnoreList configuration directives. # Not quite sure why. echo "127.0.0.1" > /etc/opendkim/TrustedHosts # We need to at least create these files, since we reference them later. # Otherwise, opendkim startup will fail touch /etc/opendkim/KeyTable touch /etc/opendkim/SigningTable if grep -q "ExternalIgnoreList" /etc/opendkim.conf; then true # already done #NODOC else # Add various configuration options to the end of `opendkim.conf`. cat >> /etc/opendkim.conf << EOF; Canonicalization relaxed/simple MinimumKeyBits 1024 ExternalIgnoreList refile:/etc/opendkim/TrustedHosts InternalHosts refile:/etc/opendkim/TrustedHosts KeyTable refile:/etc/opendkim/KeyTable SigningTable refile:/etc/opendkim/SigningTable Socket inet:8891@127.0.0.1 RequireSafeKeys false EOF fi # Create a new DKIM key. This creates mail.private and mail.txt # in $STORAGE_ROOT/mail/dkim. The former is the private key and # the latter is the suggested DNS TXT entry which we'll include # in our DNS setup. Note that the files are named after the # 'selector' of the key, which we can change later on to support # key rotation. # # A 1024-bit key is seen as a minimum standard by several providers # such as Google. But they and others use a 2048 bit key, so we'll # do the same. Keys beyond 2048 bits may exceed DNS record limits. if [ ! -f "$STORAGE_ROOT/mail/dkim/mail.private" ]; then opendkim-genkey -b 2048 -r -s mail -D $STORAGE_ROOT/mail/dkim fi # Ensure files are owned by the opendkim user and are private otherwise. chown -R opendkim:opendkim $STORAGE_ROOT/mail/dkim chmod go-rwx $STORAGE_ROOT/mail/dkim tools/editconf.py /etc/opendmarc.conf -s \ "Syslog=true" \ "Socket=inet:8893@[127.0.0.1]" # SPFIgnoreResults causes the filter to ignore any SPF results in the header # of the message. This is useful if you want the filter to perfrom SPF checks # itself, or because you don't trust the arriving header. This added header is # used by spamassassin to evaluate the mail for spamminess. tools/editconf.py /etc/opendmarc.conf -s \ "SPFIgnoreResults=true" # SPFSelfValidate causes the filter to perform a fallback SPF check itself # when it can find no SPF results in the message header. If SPFIgnoreResults # is also set, it never looks for SPF results in headers and always performs # the SPF check itself when this is set. This added header is used by # spamassassin to evaluate the mail for spamminess. tools/editconf.py /etc/opendmarc.conf -s \ "SPFSelfValidate=true" # AlwaysAddARHeader Adds an "Authentication-Results:" header field even to # unsigned messages from domains with no "signs all" policy. The reported DKIM # result will be "none" in such cases. Normally unsigned mail from non-strict # domains does not cause the results header field to be added. This added header # is used by spamassassin to evaluate the mail for spamminess. tools/editconf.py /etc/opendkim.conf -s \ "AlwaysAddARHeader=true" # Add OpenDKIM and OpenDMARC as milters to postfix, which is how OpenDKIM # intercepts outgoing mail to perform the signing (by adding a mail header) # and how they both intercept incoming mail to add Authentication-Results # headers. The order possibly/probably matters: OpenDMARC relies on the # OpenDKIM Authentication-Results header already being present. # # Be careful. If we add other milters later, this needs to be concatenated # on the smtpd_milters line. # # The OpenDMARC milter is skipped in the SMTP submission listener by # configuring smtpd_milters there to only list the OpenDKIM milter # (see mail-postfix.sh). tools/editconf.py /etc/postfix/main.cf \ "smtpd_milters=inet:127.0.0.1:8891 inet:127.0.0.1:8893"\ non_smtpd_milters=\$smtpd_milters \ milter_default_action=accept # We need to explicitly enable the opendmarc service, or it will not start hide_output systemctl enable opendmarc # Restart services. restart_service opendkim restart_service opendmarc restart_service postfix