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mailinabox/setup/dkim.sh
Aaron Ten Clay 62efe985f1
Disable OpenDMARC sending reports (#2299)
OpenDMARC report messages, while potentially useful for peer operators of mail servers, are abusable and should not be enabled by default. This change prioritizes the safety of the Box's reputation.
2023-09-02 07:10:04 -04:00

125 lines
4.6 KiB
Bash
Executable File

#!/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]" \
"FailureReports=false"
# 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"
# Disables generation of failure reports for sending domains that publish a
# "none" policy.
tools/editconf.py /etc/opendmarc.conf -s \
"FailureReportsOnNone=false"
# 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