mailinabox/setup/dkim.sh

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#!/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 opendmarc
# Make sure configuration directories exist.
mkdir -p /etc/dkim;
mkdir -p $STORAGE_ROOT/mail/dkim
# 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
if grep -q "ExternalIgnoreList" /etc/dkimpy-milter/dkimpy-milter.conf; then
true # already done #NODOC
else
# Add various configuration options to the end of `dkimpy-milter.conf`.
cat >> /etc/dkimpy-milter/dkimpy-milter.conf << EOF;
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
EOF
fi
# Create a new DKIM key. This creates mail.private and mail.txt
# in $STORAGE_ROOT/mail/dkim. The former is the private key and
# the latter is the suggested DNS TXT entry which we'll include
# in our DNS setup. Note that the files are named after the
# 'selector' of the key, which we can change later on to support
# key rotation.
if [ ! -f "$STORAGE_ROOT/mail/dkim/box-rsa.key" ]; then
# All defaults are supposed to be ok, default key for rsa is 2048 bit
dknewkey --ktype rsa $STORAGE_ROOT/mail/dkim/box-rsa
dknewkey --ktype ed25519 $STORAGE_ROOT/mail/dkim/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/dkim/box-rsa.dns
echo '" )' >> box-rsa.dns
sed -i 's/v=DKIM1;/box-ed25519._domainkey IN TXT ( "v=DKIM1; s=email;/' $STORAGE_ROOT/mail/dkim/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/dkim
chmod go-rwx $STORAGE_ROOT/mail/dkim
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
# Restart services.
restart_service dkimpy-milter
restart_service opendmarc
restart_service postfix