debian-cis/bin/hardening/12.11_find_sgid_files.sh

#!/bin/bash

#
# CIS Debian Hardening
#

#
# 12.11 Find SGID System Executables (Not Scored)
#

set -e # One error, it's over
set -u # One variable unset, it's over

# shellcheck disable=2034
HARDENING_LEVEL=2
DESCRIPTION="Find SGID system executables."
IGNORED_PATH=''

# This function will be called if the script status is on enabled / audit mode
audit () {
    info "Checking if there are sgid files"
    FS_NAMES=$(df --local -P | awk '{ if (NR!=1) print $6 }' )
    # shellcheck disable=2086
    if [ ! -z $IGNORED_PATH ]; then
        FOUND_BINARIES=$( $SUDO_CMD find $FS_NAMES -xdev -type f -perm -2000 -regextype 'egrep' ! -regex "$IGNORED_PATH" -print)
    else
        FOUND_BINARIES=$( $SUDO_CMD find $FS_NAMES -xdev -type f -perm -2000 -print)
    fi
    BAD_BINARIES=""
    for BINARY in $FOUND_BINARIES; do
        if grep -qw "$BINARY" <<< "$EXCEPTIONS"; then
            debug "$BINARY is confirmed as an exception"
        else
            BAD_BINARIES="$BAD_BINARIES $BINARY"
        fi
    done
    if [ ! -z "$BAD_BINARIES" ]; then
        crit "Some sgid files are present"
        FORMATTED_RESULT=$(sed "s/ /\n/g" <<< "$BAD_BINARIES" | sort | uniq | tr '\n' ' ')
        crit "$FORMATTED_RESULT"
    else
        ok "No unknown sgid files found"
    fi
}

# This function will be called if the script status is on enabled mode
apply () {
    info "Removing sgid on valid binary may seriously harm your system, report only here"
}

# This function will create the config file for this check with default values
create_config() {
    cat <<EOF
status=audit
# Put here valid binaries with sgid enabled separated by spaces
EXCEPTIONS="/sbin/unix_chkpwd /usr/sbin/unix_chkpwd /usr/bin/bsd-write /usr/bin/chage /usr/bin/crontab /usr/bin/expiry /usr/bin/mutt_dotlock /usr/bin/screen /usr/bin/ssh-agent /usr/bin/wall /usr/sbin/postdrop /usr/sbin/postqueue /usr/bin/at /usr/bin/dotlockfile /usr/bin/mail-lock /usr/bin/mail-touchlock /usr/bin/mail-unlock"
EOF
}

# This function will check config parameters required
check_config() {
    if [ -z "$EXCEPTIONS" ]; then
        EXCEPTIONS="@"
    fi
}

# Source Root Dir Parameter
if [ -r /etc/default/cis-hardening ]; then
    . /etc/default/cis-hardening
fi
if [ -z "$CIS_ROOT_DIR" ]; then
     echo "There is no /etc/default/cis-hardening file nor cis-hardening directory in current environment."
     echo "Cannot source CIS_ROOT_DIR variable, aborting."
    exit 128
fi

# Main function, will call the proper functions given the configuration (audit, enabled, disabled)
if [ -r "$CIS_ROOT_DIR"/lib/main.sh ]; then
    # shellcheck source=/opt/debian-cis/lib/main.sh
    . "$CIS_ROOT_DIR"/lib/main.sh
else
    echo "Cannot find main.sh, have you correctly defined your root directory? Current value is $CIS_ROOT_DIR in /etc/default/cis-hardening"
    exit 128
fi