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spam: use Sieve for rewriting subject with Rspamd & SA/Amavis (#3820)

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Georg Lauterbach 2024-01-29 13:38:01 +01:00 • committed by GitHub
parent 3b11a8305e
commit afb0093939
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16 changed files with 262 additions and 179 deletions
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61
target/scripts/startup/setup.d/security/misc.sh
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@ -81,13 +81,9 @@ function __setup__security__spamassassin() {
# shellcheck disable=SC2016
sed -i -r 's|^\$sa_kill_level_deflt (.*);|\$sa_kill_level_deflt = '"${SA_KILL}"';|g' /etc/amavis/conf.d/20-debian_defaults
if [[ ${SA_SPAM_SUBJECT} == 'undef' ]]; then
# shellcheck disable=SC2016
sed -i -r 's|^\$sa_spam_subject_tag (.*);|\$sa_spam_subject_tag = undef;|g' /etc/amavis/conf.d/20-debian_defaults
else
# shellcheck disable=SC2016
sed -i -r 's|^\$sa_spam_subject_tag (.*);|\$sa_spam_subject_tag = '"'${SA_SPAM_SUBJECT}'"';|g' /etc/amavis/conf.d/20-debian_defaults
fi
# disable rewriting the subject as this is handles by _setup_spam_subject (which uses Dovecot Sieve)
# shellcheck disable=SC2016
sed -i -r 's|^\$sa_spam_subject_tag (.*);|\$sa_spam_subject_tag = undef;|g' /etc/amavis/conf.d/20-debian_defaults
# activate short circuits when SA BAYES is certain it has spam or ham.
if [[ ${SA_SHORTCIRCUIT_BAYES_SPAM} -eq 1 ]]; then
@ -245,6 +241,57 @@ function __setup__security__amavis() {
fi
}
# If `SPAM_SUBJECT` is not empty, we create a Sieve script that alters the `Subject`
# header, in order to prepend a user-defined string.
function _setup_spam_subject() {
if [[ -z ${SPAM_SUBJECT} ]]
then
_log 'debug' 'Spam subject is not set - no prefix will be added to spam e-mails'
else
_log 'debug' "Spam subject is set - the prefix '${SPAM_SUBJECT}' will be added to spam e-mails"
_log 'trace' "Enabling '+editheader' Sieve extension"
# check whether sieve_global_extensions is disabled (and enabled it if so)
sed -i -E 's|#(sieve_global_extensions.*)|\1|' /etc/dovecot/conf.d/90-sieve.conf
# then append the extension
sedfile -i -E 's|(sieve_global_extensions.*)|\1 +editheader|' /etc/dovecot/conf.d/90-sieve.conf
_log 'trace' "Adding global (before) Sieve script for subject rewrite"
# This directory contains Sieve scripts that are executed before user-defined Sieve
# scripts run.
local DOVECOT_SIEVE_GLOBAL_BEFORE_DIR='/usr/lib/dovecot/sieve-global/before'
local DOVECOT_SIEVE_FILE='spam_subject'
readonly DOVECOT_SIEVE_GLOBAL_BEFORE_DIR DOVECOT_SIEVE_FILE
mkdir -p "${DOVECOT_SIEVE_GLOBAL_BEFORE_DIR}"
# ref: https://superuser.com/a/1502589
cat >"${DOVECOT_SIEVE_GLOBAL_BEFORE_DIR}/${DOVECOT_SIEVE_FILE}.sieve" << EOF
require ["editheader","variables"];
if anyof (header :contains "X-Spam-Flag" "YES",
header :contains "X-Spam" "Yes")
{
# Match the entire subject ...
if header :matches "Subject" "*" {
# ... to get it in a match group that can then be stored in a variable:
set "subject" "\${1}";
}
# We can't "replace" a header, but we can delete (all instances of) it and
# re-add (a single instance of) it:
deleteheader "Subject";
# Note that the header is added ":last" (so it won't appear before possible
# "Received" headers).
addheader :last "Subject" "${SPAM_SUBJECT}\${subject}";
}
EOF
sievec "${DOVECOT_SIEVE_GLOBAL_BEFORE_DIR}/${DOVECOT_SIEVE_FILE}.sieve"
chown dovecot:root "${DOVECOT_SIEVE_GLOBAL_BEFORE_DIR}/${DOVECOT_SIEVE_FILE}."{sieve,svbin}
fi
}
# We can use Sieve to move spam emails to the "Junk" folder.
function _setup_spam_to_junk() {
if [[ ${MOVE_SPAM_TO_JUNK} -eq 1 ]]; then