debian-cis/bin/hardening/6.1.14_find_sgid_files.sh

#!/bin/bash

# run-shellcheck
#
# CIS Debian Hardening
#

#
# 6.1.14 Audit SGID executables (Not Scored)
#

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

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

# find emits following error if directory or file disappear during
# tree traversal: find: ‘/tmp/xxx’: No such file or directory
FIND_IGNORE_NOSUCHFILE_ERR=false

# This function will be called if the script status is on enabled / audit mode
audit() {
    info "Checking if there are sgid files"
    if [ -n "$IGNORED_PATH" ]; then
        # maybe IGNORED_PATH allow us to filter out some FS
        FS_NAMES=$(df --local -P | awk '{if (NR!=1) print $6}' | grep -vE "$IGNORED_PATH")

        [ "${FIND_IGNORE_NOSUCHFILE_ERR}" = true ] && set +e
        # shellcheck disable=2086
        FOUND_BINARIES=$($SUDO_CMD find $FS_NAMES -xdev -ignore_readdir_race -type f -perm -2000 -regextype 'egrep' ! -regex $IGNORED_PATH -print)
        [ "${FIND_IGNORE_NOSUCHFILE_ERR}" = true ] && set -e

    else
        FS_NAMES=$(df --local -P | awk '{if (NR!=1) print $6}')

        [ "${FIND_IGNORE_NOSUCHFILE_ERR}" = true ] && set +e
        # shellcheck disable=2086
        FOUND_BINARIES=$($SUDO_CMD find $FS_NAMES -xdev -ignore_readdir_race -type f -perm -2000 -print)
        [ "${FIND_IGNORE_NOSUCHFILE_ERR}" = true ] && set -e
    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 $BINARY"
        fi
    done
    if [ -n "$BAD_BINARIES" ]; then
        crit "Some sgid files are present"
        # shellcheck disable=SC2001
        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
    # shellcheck source=../../debian/default
    . /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 "$CIS_ROOT_DIR"/lib/main.sh ]; then
    # shellcheck source=../../lib/main.sh
    . "$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