mailinabox/setup/dkim.sh

#!/bin/bash
# DKIM
# --------
#
# DKIMpy 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 DKIMpy/OpenDMARC...
apt_install dkimpy-milter python3-dkim opendmarc

# Make sure configuration directories exist.
mkdir -p /etc/dkim;
mkdir -p $STORAGE_ROOT/mail/dkim2

# Used in InternalHosts and ExternalIgnoreList configuration directives.
# Not quite sure why.
echo "127.0.0.1" > /etc/dkim/TrustedHosts

# We need to at least create these files, since we reference them later.
touch /etc/dkim/KeyTable
touch /etc/dkim/SigningTable

tools/editconf.py /etc/dkimpy-milter/dkimpy-milter.conf -s \
    "MacroList=daemon_name|ORIGINATING"
    "MacroListVerify=daemon_name|VERIFYING"
    "Canonicalization=relaxed/simple"
    "MinimumKeyBits=1024"
    "ExternalIgnoreList=refile:/etc/dkim/TrustedHosts"
    "InternalHosts=refile:/etc/dkim/TrustedHosts"
    "KeyTable=refile:/etc/dkim/KeyTable"
    "KeyTableEd25519=refile:/etc/dkim/KeyTableEd25519"
    "SigningTable=refile:/etc/dkim/SigningTable"
    "Socket=inet:8892@127.0.0.1"
    "RequireSafeKeys=false"

# Create a new DKIM key. This creates mail.private and mail.txt
# in $STORAGE_ROOT/mail/dkim. The former is the private key and
# the latter is the suggested DNS TXT entry which we'll include
# in our DNS setup. Note that the files are named after the
# 'selector' of the key, which we can change later on to support
# key rotation.
if [ ! -f "$STORAGE_ROOT/mail/dkim2/box-rsa.key" ]; then
	# All defaults are supposed to be ok, default key for rsa is 2048 bit
	dknewkey --ktype rsa $STORAGE_ROOT/mail/dkim2/box-rsa
	dknewkey --ktype ed25519 $STORAGE_ROOT/mail/dkim2/box-ed25519
	
	# Force them into the format dns_update.py expects
	sed -i 's/v=DKIM1;/box-rsa._domainkey IN      TXT      ( "v=DKIM1; s=email;/' $STORAGE_ROOT/mail/dkim2/box-rsa.dns
	echo '" )' >> box-rsa.dns
	sed -i 's/v=DKIM1;/box-ed25519._domainkey IN      TXT      ( "v=DKIM1; s=email;/' $STORAGE_ROOT/mail/dkim2/box-ed25519.dns
	echo '" )' >> box-ed25519.dns
fi

# Ensure files are owned by the dkimpy-milter user and are private otherwise.
chown -R dkimpy-milter:dkimpy-milter $STORAGE_ROOT/mail/dkim2
chmod go-rwx $STORAGE_ROOT/mail/dkim2

tools/editconf.py /etc/opendmarc.conf -s \
	"Syslog=true" \
	"Socket=inet:8893@[127.0.0.1]" \
	"FailureReports=true"

# 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"

# Enables generation of failure reports for sending domains that publish a
# "none" policy.

tools/editconf.py /etc/opendmarc.conf -s \
        "FailureReportsOnNone=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/dkimpy-milter/dkimpy-milter.conf -s \
        "AlwaysAddARHeader=true"

# Add DKIMpy and OpenDMARC as milters to postfix, which is how DKIMpy
# 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
# DKIM 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 DKIMpy milter
# (see mail-postfix.sh).
tools/editconf.py /etc/postfix/main.cf \
	"smtpd_milters=inet:127.0.0.1:8892 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

# There is a fault in the dkim code for Ubuntu 20.04, let's fix it. Not necessary for Ubuntu 21.04 or newer
sed -i 's/return b""\.join(r\.items\[0\]\.strings)/return b""\.join(list(r\.items)\[0\]\.strings)/' /usr/lib/python3/dist-packages/dkim/dnsplug.py

# Restart services.
restart_service dkimpy-milter
restart_service opendmarc
restart_service postfix