#!/bin/bash ## Copyright (C) 2012 - 2024 ENCRYPTED SUPPORT LP ## See the file COPYING for copying conditions. ## https://forums.whonix.org/t/disable-suid-binaries/7706 ## https://forums.whonix.org/t/re-mount-home-and-other-with-noexec-and-nosuid-among-other-useful-mount-options-for-better-security/7707 ## dpkg-statoverride does not support end-of-options ("--"). set -o errexit -o nounset -o pipefail exit_code=0 store_dir="/var/lib/permission-hardener" dpkg_admindir_parameter_existing_mode="--admindir ${store_dir}/existing_mode" dpkg_admindir_parameter_new_mode="--admindir ${store_dir}/new_mode" delimiter="#permission-hardener-delimiter#" # shellcheck disable=SC1091 source /usr/libexec/helper-scripts/safe_echo.sh # shellcheck disable=SC2034 log_level=notice # shellcheck disable=SC1091 source /usr/libexec/helper-scripts/log_run_die.sh echo_wrapper_ignore() { if test "${1}" = "verbose"; then shift log notice "Run: $*" else shift fi "$@" 2>/dev/null || true } echo_wrapper_audit() { if test "${1}" = "verbose"; then shift log notice "Run: $*" else shift fi return_code=0 "$@" || { return_code="$?" exit_code=203 log error "Command '$*' failed with exit code '${return_code}'! calling function name: '${FUNCNAME[1]}'" >&2 } } make_store_dir(){ mkdir --parents "${store_dir}/private" mkdir --parents "${store_dir}/existing_mode" mkdir --parents "${store_dir}/new_mode" } ## Some tools may fail on newlines and even variable assignment to array may ## fail if a variable that will be assigned to an array element contains ## characters that are used as delimiters. block_newlines(){ local newline_variable newline_value newline_variable="${1}" newline_value="${2}" ## dpkg-statoverride: error: path may not contain newlines #if [[ "${newline_value}" == *$'\n'* ]]; then if [[ "${newline_value}" != "${newline_value//$'\n'/NEWLINE}" ]]; then log warn "Skipping ${newline_variable} that contains newlines: '${newline_value}'" >&2 return 1 fi } output_stat(){ local file_name file_name="${1}" if test -z "${file_name}"; then log error "File name is empty. file_name: '${file_name}'" >&2 return 1 fi block_newlines file "${file_name}" ## dpkg-statoverride can actually handle '--file-name'. # if [[ $file_name == --* ]]; then # log warn "File name starts with '--'. This would be interpreted by dpkg-statoverride as an option. Skipping. file_name: '${file_name}'" >&2 # return 1 # fi declare -a arr local file_name_from_stat stat_output stat_output_newlined if ! stat_output="$(stat --format="%a${delimiter}%U${delimiter}%G${delimiter}%n${delimiter}" -- "${file_name}")"; then log error "Failed to run 'stat' on file: '${file_name}'!" >&2 return 1 fi if [ "$stat_output" = "" ]; then log error "stat_output is empty. File name: '${file_name}' Stat output: '${stat_output}' stat_output_newlined: '${stat_output_newlined}' line: '${line}' " >&2 return 1 fi stat_output_newlined="$(printf '%s\n' "${stat_output//${delimiter}/$'\n'}")" if test "${stat_output_newlined}" = ""; then log error "stat_output_newlined is empty. File name: '${file_name}' Stat output: '${stat_output}' stat_output_newlined: '${stat_output_newlined}' line: '${line}' " >&2 return 1 fi readarray -t arr <<< "${stat_output_newlined}" if test "${#arr[@]}" = 0; then log error "Array length is 0. File name: '${file_name}' Stat output: '${stat_output}' stat_output_newlined: '${stat_output_newlined}' line: '${line}' " >&2 return 1 fi existing_mode="${arr[0]}" existing_owner="${arr[1]}" existing_group="${arr[2]}" file_name_from_stat="${arr[3]}" if [ ! "$file_name" = "$file_name_from_stat" ]; then log error "\ File name is different from file name received from stat: File name: '${file_name}' File name from stat: '${file_name_from_stat}' line: '${line}' " >&2 return 1 fi if test -z "${existing_mode}"; then log error "Existing mode is empty. Stat output: '${stat_output}', line: '${line}'" >&2 return 1 fi if test -z "${existing_owner}"; then log error "Existing owner is empty. Stat output: '${stat_output}', line: '${line}'" >&2 return 1 fi if test -z "${existing_group}"; then log error "Existing group is empty. Stat output: '${stat_output}', line: '${line}'" >&2 return 1 fi } sanity_tests() { echo_wrapper_audit silent \ which \ capsh getcap setcap stat find dpkg-statoverride getent grep 1>/dev/null } add_nosuid_statoverride_entry() { local fso_to_process fso_to_process="${fso}" local should_be_counter should_be_counter=0 local counter_actual counter_actual=0 local dummy_line while IFS="" read -r -d "" dummy_line; do log info "Test would parse line: '${dummy_line}'" should_be_counter=$((should_be_counter + 1)) done < <(safe_echo_nonewline "${fso_to_process}" | find -files0-from - -perm /u=s,g=s -print0) ## False positive on SC2185 (find without path argument) #1748 ## https://github.com/koalaman/shellcheck/issues/1748 ## ## /usr/lib will hit ARG_MAX if using bash 'shopt -s globstar' and '/usr/lib/**'. ## Using 'find' with '-perm /u=s,g=s' is faster and avoids ARG_MAX. ## https://forums.whonix.org/t/disable-suid-binaries/7706/17 local line while IFS="" read -r -d "" file_name; do counter_actual=$((counter_actual + 1)) ## sets: ## exiting_mode ## existing_owner ## existing_group output_stat "${file_name}" ## -h file True if file is a symbolic Link. ## -u file True if file has its set-user-id bit set. ## -g file True if file has its set-group-id bit set. if test -h "${file_name}"; then ## https://forums.whonix.org/t/disable-suid-binaries/7706/14 log info "Skip symlink: '${file_name}'" continue fi if test -d "${file_name}"; then log info "Skip directory: '${file_name}'" continue fi local setuid setgid setuid="" if test -u "${file_name}"; then setuid=true fi setgid="" if test -g "${file_name}"; then setgid=true fi local setuid_or_setgid setuid_or_setgid="" if test "${setuid}" = "true" || test "${setgid}" = "true"; then setuid_or_setgid=true fi if test -z "${setuid_or_setgid}"; then log info "Neither setuid nor setgid. Skipping. file_name: '${file_name}'" continue fi ## Remove suid / gid and execute permission for 'group' and 'others'. ## Similar to: chmod og-ugx /path/to/filename ## Removing execution permission is useful to make binaries such as 'su' ## fail closed rather than fail open if suid was removed from these. ## Do not remove read access since no security benefit and easier to ## manually undo for users. ## Are there suid or sgid binaries which are still useful if suid / sgid ## has been removed from these? new_mode="744" local is_exact_whitelisted is_exact_whitelisted="" for white_list_entry in "${exact_white_list[@]:-}"; do if test -z "${white_list_entry}"; then log info "white_list_entry unset. Skipping. file_name: '${file_name}'" continue fi if test "${file_name}" = "${white_list_entry}"; then is_exact_whitelisted="true" log info "is_exact_whitelisted=true. Skipping. file_name: '${file_name}'" ## Stop looping through the whitelist. break fi done local is_match_whitelisted is_match_whitelisted="" for matchwhite_list_entry in "${match_white_list[@]:-}"; do if test -z "${matchwhite_list_entry}"; then log info "matchwhite_list_entry unset. Skipping. file_name: '${file_name}'" continue fi if safe_echo "${file_name}" | grep --quiet --fixed-strings -- "${matchwhite_list_entry}"; then is_match_whitelisted="true" log info "is_match_whitelisted=true. Skipping. file_name: '${file_name}'" ## Stop looping through the match_white_list. break fi done local is_disable_whitelisted is_disable_whitelisted="" for disablematch_list_entry in "${disable_white_list[@]:-}"; do if test -z "${disablematch_list_entry}"; then log info "disablematch_list_entry unset. Skipping. file_name: '${file_name}'" continue fi if safe_echo "${file_name}" | grep --quiet --fixed-strings -- "${disablematch_list_entry}"; then is_disable_whitelisted="true" log info "is_disable_whitelisted=true. Skipping. file_name: '${file_name}'" ## Stop looping through the disablewhitelist. break fi done local clean_output_prefix clean_output clean_output_prefix="Managing (S|G)UID of line:" clean_output="${setuid:+setuid='true'} ${setgid:+setgid='true'} existing_mode='${existing_mode}' new_mode='${new_mode}' file='${file_name}'" if test "${whitelists_disable_all:-}" = "true"; then log info "${clean_output_prefix} whitelists_disable_all=true ${clean_output}" elif test "${is_disable_whitelisted}" = "true"; then log info "${clean_output_prefix} is_disable_whitelisted=true ${clean_output}" else if test "${is_exact_whitelisted}" = "true"; then log info "${clean_output_prefix} is_exact_whitelisted=true ${clean_output}" continue fi if test "${is_match_whitelisted}" = "true"; then log info "${clean_output_prefix} is_match_whitelisted=true matchwhite_list_entry='${matchwhite_list_entry}' ${clean_output}" continue fi fi log notice "${clean_output_prefix} ${clean_output}" # shellcheck disable=SC2086 if dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --list "${file_name}" >/dev/null; then log info "Existing mode already saved previously. Not saving again." else ## Save existing_mode in separate database. ## Not using --update as not intending to enforce existing_mode. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${file_name}" fi ## No need to check "dpkg-statoverride --list" for existing entries. ## If existing_mode was correct already, we would not have reached this ## point. Since existing_mode is incorrect, remove from dpkg-statoverride ## and re-add. ## Remove from real database. echo_wrapper_ignore silent dpkg-statoverride --remove "${file_name}" ## Remove from separate database. # shellcheck disable=SC2086 echo_wrapper_ignore silent dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --remove "${file_name}" ## Add to real database and use --update to make changes on disk. echo_wrapper_audit verbose dpkg-statoverride --add --update "${existing_owner}" "${existing_group}" "${new_mode}" "${file_name}" ## Not using --update as this is only for recording. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --add "${existing_owner}" "${existing_group}" "${new_mode}" "${file_name}" done < <(safe_echo_nonewline "${fso_to_process}" | find -files0-from - -perm /u=s,g=s -print0) ## Sanity test. if test ! "${should_be_counter}" = "${counter_actual}"; then log info "File (parsed/wanted): '${fso_to_process}': (${counter_actual}/${should_be_counter})" log error "Expected number of files to be parsed was not met." >&2 exit_code=202 fi } set_file_perms() { log info "START parsing config file: '${config_file}'" local line while read -r line || test -n "${line}"; do if test -z "${line}"; then true "DEBUG: line is empty. Skipping." continue fi if [[ "${line}" =~ ^\s*# ]]; then continue fi if ! [[ "${line}" =~ [0-9a-zA-Z/] ]]; then exit_code=200 log error "Line contains invalid characters: '${line}'" >&2 ## Safer to exit with error in this case. ## https://forums.whonix.org/t/disable-suid-binaries/7706/59 exit "${exit_code}" fi if test "${line}" = 'whitelists_disable_all=true'; then whitelists_disable_all=true log info "whitelists_disable_all=true" continue fi #global fso local mode_from_config owner_from_config group_from_config capability_from_config if ! read -r fso mode_from_config owner_from_config group_from_config capability_from_config <<<"${line}"; then exit_code=201 log error "Cannot parse line: '${line}'" >&2 ## Debugging. du -hs /tmp || true safe_echo "test -w /tmp: '$(test -w /tmp)'" >&2 || true ## Safer to exit with error in this case. ## https://forums.whonix.org/t/disable-suid-binaries/7706/59 exit "${exit_code}" fi log info "Parsing line: fso='${fso}' mode_from_config='${mode_from_config}' owner_from_config='${owner_from_config}' group_from_config='${group_from_config}' capability_from_config='${capability_from_config}'" ## Debugging. #safe_echo "line: '${line}'" #safe_echo "fso: '${fso}'" #safe_echo "mode_from_config: '${mode_from_config}'" #safe_echo "owner_from_config: '${owner_from_config}'" local fso_without_trailing_slash fso_without_trailing_slash="${fso%/}" declare -g disable_white_list exact_white_list match_white_list case "${mode_from_config}" in disablewhitelist) disable_white_list+=("${fso}") continue ;; exactwhitelist) exact_white_list+=("${fso}") continue ;; matchwhitelist) match_white_list+=("${fso}") continue ;; esac if test ! -e "${fso}"; then log info "File does not exist: '${fso}'" continue fi ## Use dpkg-statoverride so permissions are not reset during upgrades. if test "${mode_from_config}" = "nosuid"; then ## If mode_from_config is "nosuid" the config does not set owner and ## group. Therefore do not enforce owner/group check. add_nosuid_statoverride_entry else local string_length_of_mode_from_config string_length_of_mode_from_config="${#mode_from_config}" if test "${string_length_of_mode_from_config}" -gt "4"; then log error "Invalid mode: '${mode_from_config}'" >&2 continue fi if test "${string_length_of_mode_from_config}" -lt "3"; then log error "Invalid mode: '${mode_from_config}'" >&2 continue fi if ! grep --quiet --fixed-strings -- "${owner_from_config}:" "${store_dir}/private/passwd"; then log error "Owner from config does not exist: '${owner_from_config}'" >&2 continue fi if ! grep --quiet --fixed-strings -- "${group_from_config}:" "${store_dir}/private/group"; then log error "Group from config does not exist: '${group_from_config}'" >&2 continue fi local mode_for_grep mode_for_grep="${mode_from_config}" first_character_of_mode_from_config="${mode_from_config::1}" if test "${first_character_of_mode_from_config}" = "0"; then ## Remove leading '0'. mode_for_grep="${mode_from_config:1}" fi file_name="${fso_without_trailing_slash}" ## sets: ## exiting_mode ## existing_owner ## existing_group output_stat "${file_name}" ## Check there is an entry for the fso. ## ## example: dpkg-statoverride --list | grep /home ## output: ## root root 755 /home ## ## dpkg-statoverride does not show leading '0'. local dpkg_statoverride_list_output="" local dpkg_statoverride_list_exit_code=0 dpkg_statoverride_list_output="$(dpkg-statoverride --list "${fso_without_trailing_slash}")" || { dpkg_statoverride_list_exit_code=$? true } if test "${dpkg_statoverride_list_exit_code}" = "0"; then local grep_line grep_line="${owner_from_config} ${group_from_config} ${mode_for_grep} ${fso_without_trailing_slash}" if safe_echo "${dpkg_statoverride_list_output}" | grep --quiet --fixed-strings -- "${grep_line}"; then log info "The owner/group/mode matches fso entry. No further action required." else log info "The owner/group/mode does not match fso entry, updating entry." ## fso_without_trailing_slash instead of fso to prevent ## "dpkg-statoverride: warning: stripping trailing /" # shellcheck disable=SC2086 if dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --list "${fso_without_trailing_slash}" >/dev/null; then log info "Existing mode already saved previously. Not saving again." else ## Save existing_mode in separate database. ## Not using --update as not intending to enforce existing_mode. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${fso_without_trailing_slash}" fi # shellcheck disable=SC2086 echo_wrapper_ignore silent dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --remove "${fso_without_trailing_slash}" ## Remove from and add to real database. echo_wrapper_ignore silent dpkg-statoverride --remove "${fso_without_trailing_slash}" echo_wrapper_audit verbose dpkg-statoverride --add --update "${owner_from_config}" "${group_from_config}" "${mode_from_config}" "${fso_without_trailing_slash}" ## Save in separate database. ## Not using --update as this is only for saving. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --add "${owner_from_config}" "${group_from_config}" "${mode_from_config}" "${fso_without_trailing_slash}" fi else log info "There is no fso entry, adding one." # shellcheck disable=SC2086 if dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --list "${fso_without_trailing_slash}" >/dev/null; then log info "Existing mode already saved previously. Not saving again." else ## Save existing_mode in separate database. ## Not using --update as not intending to enforce existing_mode. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${fso_without_trailing_slash}" fi ## Add to real database. echo_wrapper_audit verbose dpkg-statoverride --add --update "${owner_from_config}" "${group_from_config}" "${mode_from_config}" "${fso_without_trailing_slash}" ## Save in separate database. ## Not using --update as this is only for saving. # shellcheck disable=SC2086 echo_wrapper_audit silent dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --add "${owner_from_config}" "${group_from_config}" "${mode_from_config}" "${fso_without_trailing_slash}" fi fi if test -z "${capability_from_config}"; then log info "capability_from_config is empty. Skipping. file_name: '${file_name}'" continue fi if test "${capability_from_config}" = "none"; then ## https://forums.whonix.org/t/disable-suid-binaries/7706/45 ## sudo setcap -r /bin/ping 2>/dev/null ## Failed to set capabilities on file '/bin/ping' (No data available) ## The value of the capability argument is not permitted for a file. Or ## the file is not a regular (non-symlink) file ## Therefore use echo_wrapper_ignore. echo_wrapper_ignore verbose setcap -r -- "${fso}" getcap_output="$(getcap -- "${fso}")" if test -n "${getcap_output}"; then exit_code=205 log error "Removing capabilities failed. File: '${fso}'" >&2 continue fi else if ! capsh --print | grep --fixed-strings -- "Bounding set" | grep --quiet -- "${capability_from_config}"; then log error "Capability from config does not exist: '${capability_from_config}'" >&2 continue fi ## feature request: dpkg-statoverride: support for capabilities ## https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=502580 echo_wrapper_audit verbose setcap "${capability_from_config}+ep" -- "${fso}" fi done <"${config_file}" log info "END parsing config file: '${config_file}'" } parse_config_folder() { touch "${store_dir}/private/passwd" chmod og-rwx "${store_dir}/private/passwd" touch "${store_dir}/private/group" chmod og-rwx "${store_dir}/private/group" local passwd_file_contents_temp ## Query contents of password and group databases only once and buffer them ## ## If we don't buffer we sometimes get incorrect results when checking for ## entries using 'if getent passwd | grep --quiet -- '^root:'; ...' since ## 'grep' exits after the first match in this case causing 'getent' to ## receive SIGPIPE, which then fails the pipeline since 'set -o pipefail' is ## set for this script. passwd_file_contents_temp="$(getent passwd)" safe_echo "${passwd_file_contents_temp}" | tee -- "${store_dir}/private/passwd" >/dev/null group_file_contents_temp="$(getent group)" safe_echo "${group_file_contents_temp}" | tee -- "${store_dir}/private/group" >/dev/null #passwd_file_contents="$(cat "${store_dir}/private/passwd")" #group_file_contents="$(cat "${store_dir}/private/group")" shopt -s nullglob for config_file in \ /etc/permission-hardener.d/*.conf \ /usr/local/etc/permission-hardener.d/*.conf \ /etc/permission-hardening.d/*.conf \ /usr/local/etc/permission-hardening.d/*.conf do set_file_perms done } apply() { check_root make_store_dir sanity_tests parse_config_folder log notice "\ To compare the current and previous permission modes, install 'meld' (or preferred diff tool) for comparison of file mode changes: sudo apt install --no-install-recommends meld meld ${store_dir}/existing_mode/statoverride ${store_dir}/new_mode/statoverride" } spare() { check_root make_store_dir remove_file="${1}" exit_code=0 dpkg_admindir_parameter_existing_mode="--admindir ${store_dir}/existing_mode" dpkg_admindir_parameter_new_mode="--admindir ${store_dir}/new_mode" if test ! -f "${store_dir}/existing_mode/statoverride"; then true "DEBUG: Stat file does not exist, hardening was not applied before." return 0 fi local line while read -r line; do ## example line: ## root root 4755 /usr/lib/eject/dmcrypt-get-device local owner group mode file_name if ! read -r owner group mode file_name <<< "${line}"; then exit_code=201 log error "Cannot parse line: '${line}'" >&2 continue fi log info "Parsing line: owner='${owner}' group='${group}' mode='${mode}' file_name='${file_name}'" if test "${remove_file}" = "all"; then verbose="" remove_one=false else if test "${remove_file}" = "${file_name}"; then verbose="--verbose" remove_one=true safe_echo "${remove_one}" | tee -- "${store_dir}/remove_one" >/dev/null else safe_echo "false" | tee -- "${store_dir}/remove_one" >/dev/null continue fi fi if test "${remove_one}" = "true"; then set -o xtrace fi if test -e "${file_name}"; then # shellcheck disable=SC2086 chown ${verbose} "${owner}:${group}" "${file_name}" || exit_code=202 ## chmod need to be run after chown since chown removes suid. ## https://unix.stackexchange.com/questions/53665/chown-removes-setuid-bit-bug-or-feature # shellcheck disable=SC2086 chmod ${verbose} "${mode}" "${file_name}" || exit_code=203 else log info "File does not exist: '${file_name}'" fi dpkg-statoverride --remove "${file_name}" &>/dev/null || true # shellcheck disable=SC2086 dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --remove "${file_name}" &>/dev/null || true # shellcheck disable=SC2086 dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --remove "${file_name}" &>/dev/null || true if test "${remove_one}" = "true"; then set +o xtrace break fi done < "${store_dir}/existing_mode/statoverride" if test ! "${remove_file}" = "all"; then if test "$(cat "${store_dir}/remove_one")" = "false"; then log info "No file was removed. File '${remove_file}' has not been removed from SUID Disabler and Permission Hardener during this invocation. This is expected if already done earlier. This program expects the full path to the file. Example: $0 disable /usr/bin/newgrp # absolute path: works $0 disable newgrp # relative path: does not work To remove all: $0 disable all This change might not be permanent. For full instructions, see: https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener To view list of changed by SUID Disabler and Permission Hardener: https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#View_List_of_Permissions_Changed_by_SUID_Disabler_and_Permission_Hardener For re-enabling any specific SUID binary: https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#Re-Enable_Specific_SUID_Binaries For completely disabling SUID Disabler and Permission Hardener: https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#Disable_SUID_Disabler_and_Permission_Hardener" fi fi } check_root(){ if test "$(id -u)" != "0"; then log error "Not running as root, aborting." exit 1 fi } usage(){ safe_echo "Usage: ${0##*/} enable ${0##*/} disable [FILE|all] Examples: ${0##*/} enable ${0##*/} disable all ${0##*/} disable /usr/bin/newgrp" >&2 exit "${1}" } case "${1:-}" in enable) shift; apply "$@";; disable) shift case "${1:-}" in "") usage 1;; *) spare "${1}";; esac ;; -h|--help) usage 0;; *) usage 1;; esac if test "${exit_code}" != "0"; then log error "Exiting with non-zero exit code: '${exit_code}'" >&2 fi exit "${exit_code}"