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Rename file permission hardening script

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Hardener as the script is the agent that is hardening the file
permissions.
This commit is contained in:
Ben Grande 2024-01-02 13:34:29 +01:00
parent f138cf0f78
commit abf72c2ee4
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GPG key ID: 00C64E14F51F9E56
24 changed files with 54 additions and 55 deletions
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usr/bin/permission-hardener Executable file
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@ -0,0 +1,672 @@
#!/bin/bash
## Copyright (C) 2012 - 2024 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
## 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
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"
echo_wrapper_ignore() {
echo "run: $*"
"$@" 2>/dev/null || true
}
echo_wrapper_silent_ignore() {
#echo "run: $@"
"$@" 2>/dev/null || true
}
echo_wrapper_audit() {
echo "run: $*"
return_code=0
"$@" ||
{
return_code="$?"
exit_code=203
echo "ERROR: above command failed with exit code '${return_code}'! calling function name: '${FUNCNAME[1]}'" >&2
}
}
echo_wrapper_silent_audit() {
#echo "run (debugging): $@"
return_code=0
"$@" ||
{
return_code="$?"
exit_code=204
echo "ERROR: above command '$*' 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 "${store_dir}/new_mode"
}
sanity_tests() {
echo_wrapper_silent_audit which \
capsh getcap setcap stat find dpkg-statoverride getent xargs grep 1>/dev/null
}
add_nosuid_statoverride_entry() {
local fso_to_process
fso_to_process="${fso}"
local should_be_counter
should_be_counter="$(find "${fso_to_process}" -perm /u=s,g=s | wc -l)" || true
local counter_actual
counter_actual=0
local line
while read -r line; do
true "line: ${line}"
counter_actual="$((counter_actual + 1))"
local arr file_name existing_mode existing_owner existing_group
IFS=" " read -r -a arr <<< "${line}"
file_name="${arr[0]}"
existing_mode="${arr[1]}"
existing_owner="${arr[2]}"
existing_group="${arr[3]}"
if test "${#arr[@]}" = 0; then
echo "ERROR: arr is empty. line: '${line}'" >&2
continue
fi
if test -z "${file_name}"; then
echo "ERROR: file_name is empty. line: '${line}'" >&2
continue
fi
if test -z "${existing_mode}"; then
echo "ERROR: existing_mode is empty. line: '${line}'" >&2
continue
fi
if test -z "${existing_owner}"; then
echo "ERROR: existing_owner is empty. line: '${line}'" >&2
continue
fi
if test -z "${existing_group}"; then
echo "ERROR: existing_group is empty. line: '${line}'" >&2
continue
fi
## -h file True if file is a symbolic Link.
## -u file True if file has its set-user-id bit set.
## -g file True if file has its set-group-id bit set.
if test -h "${file_name}"; then
## https://forums.whonix.org/t/disable-suid-binaries/7706/14
true "skip symlink: ${file_name}"
continue
fi
if test -d "${file_name}"; then
true "skip directory: ${file_name}"
continue
fi
local setuid setuid_output setsgid setsgid_output
setuid=""
setuid_output=""
if test -u "${file_name}"; then
setuid=true
setuid_output="set-user-id"
fi
setsgid=""
setsgid_output=""
if test -g "${file_name}"; then
setsgid=true
setsgid_output="set-group-id"
fi
local setuid_or_setsgid
setuid_or_setsgid=""
if test "${setuid}" = "true" || test "${setsgid}" = "true"; then
setuid_or_setsgid=true
fi
if test -z "${setuid_or_setsgid}"; then
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 ${exact_white_list}; do
if test "${file_name}" = "${white_list_entry}"; then
is_exact_whitelisted="true"
## Stop looping through the whitelist.
break
fi
done
local is_match_whitelisted
is_match_whitelisted=""
for matchwhite_list_entry in ${match_white_list}; do
if echo "${file_name}" | grep --quiet --fixed-strings "${matchwhite_list_entry}"; then
is_match_whitelisted="true"
## Stop looping through the match_white_list.
break
fi
done
local is_disable_whitelisted
is_disable_whitelisted=""
for disablematch_list_entry in ${disable_white_list:-}; do
if echo "${file_name}" | grep --quiet --fixed-strings "${disablematch_list_entry}"; then
is_disable_whitelisted="true"
## Stop looping through the disablewhitelist.
break
fi
done
if test "${whitelists_disable_all:-}" = "true"; then
true "INFO: whitelists_disable_all=true - ${setuid_output} ${setsgid_output} found - file_name: '${file_name}' | existing_mode: '${existing_mode}'"
elif test "${is_disable_whitelisted}" = "true"; then
true "INFO: white list disabled - ${setuid_output} ${setsgid_output} found - file_name: '${file_name}' | existing_mode: '${existing_mode}'"
else
if test "${is_exact_whitelisted}" = "true"; then
true "INFO: SKIP whitelisted - ${setuid_output} ${setsgid_output} found - file_name: '${file_name}' | existing_mode: '${existing_mode}'"
continue
fi
if test "${is_match_whitelisted}" = "true"; then
true "INFO: SKIP matchwhitelisted - ${setuid_output} ${setsgid_output} found - file_name: '${file_name}' | existing_mode: '${existing_mode}' | matchwhite_list_entry: '${matchwhite_list_entry}'"
continue
fi
fi
echo "INFO: ${setuid_output} ${setsgid_output} found - file_name: '${file_name}' | existing_mode: '${existing_mode}' | new_mode: '${new_mode}'"
# shellcheck disable=SC2086
if dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --list "${file_name}" >/dev/null; then
true "OK 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_silent_audit dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${file_name}"
fi
## No need to check "dpkg-statoverride --list" for existing entries.
## If existing_mode was correct already, we would not have reached this
## point. Since existing_mode is incorrect, remove from dpkg-statoverride
## and re-add.
## Remove from real database.
echo_wrapper_silent_ignore dpkg-statoverride --remove "${file_name}"
## Remove from separate database.
# shellcheck disable=SC2086
echo_wrapper_silent_ignore 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 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_silent_audit dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --add "${existing_owner}" "${existing_group}" "${new_mode}" "${file_name}"
## /lib will hit ARG_MAX if using bash 'shopt -s globstar' and '/lib/**'.
## Using 'find' with '-perm /u=s,g=s' is faster and avoids ARG_MAX.
## https://forums.whonix.org/t/disable-suid-binaries/7706/17
done < <(find "${fso_to_process}" -perm /u=s,g=s -print0 | xargs -I{} -0 stat -c "%n %a %U %G" {})
## Sanity test.
if test ! "${should_be_counter}" = "${counter_actual}"; then
echo "INFO: fso_to_process: '${fso_to_process}' | counter_actual : '${counter_actual}'"
echo "INFO: fso_to_process: '${fso_to_process}' | should_be_counter: '${should_be_counter}'"
exit_code=202
echo "ERROR: counter does not check out." >&2
fi
}
set_file_perms() {
true "INFO: START parsing config_file: '${config_file}'"
local line
while read -r line || test -n "${line}"; do
if test -z "${line}"; then
continue
fi
if [[ "${line}" =~ ^# ]]; then
continue
fi
if [[ "${line}" =~ [0-9a-zA-Z/] ]]; then
true "OK line contains only white listed characters."
else
exit_code=200
echo "ERROR: cannot parse line with invalid character. line: '${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
echo "INFO: whitelists_disable_all=true - all whitelists disabled."
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 <<<"${line}"; then
exit_code=201
echo "ERROR: cannot parse. line: '${line}'" >&2
## Debugging.
du -hs /tmp || true
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
## Debugging.
#echo "line: '${line}'"
#echo "fso: '${fso}'"
#echo "mode_from_config: '${mode_from_config}'"
#echo "owner_from_config: '${owner_from_config}'"
local fso_without_trailing_slash
fso_without_trailing_slash="${fso%/}"
if test "${mode_from_config}" = "disablewhitelist"; then
## TODO: test/add white spaces inside file name support
disable_white_list+="${fso} "
continue
fi
if test "${mode_from_config}" = "exactwhitelist"; then
## TODO: test/add white spaces inside file name support
exact_white_list+="${fso} "
continue
fi
if test "${mode_from_config}" = "matchwhitelist"; then
## TODO: test/add white spaces inside file name support
match_white_list+="${fso} "
continue
fi
if test ! -e "${fso}"; then
true "INFO: fso: '${fso}' - does not exist. This is likely normal."
continue
fi
## Use dpkg-statoverride so permissions are not reset during upgrades.
if test "${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
echo "ERROR: Mode '${mode_from_config}' is invalid!" >&2
continue
fi
if test "${string_length_of_mode_from_config}" -lt "3"; then
echo "ERROR: Mode '${mode_from_config}' is invalid!" >&2
continue
fi
if ! grep --quiet --fixed-strings "${owner_from_config}:" "${store_dir}/private/passwd"; then
echo "ERROR: owner_from_config '${owner_from_config}' does not exist!" >&2
continue
fi
if ! grep --quiet --fixed-strings "${group_from_config}:" "${store_dir}/private/group"; then
echo "ERROR: group_from_config '${group_from_config}' does not exist!" >&2
continue
fi
local mode_for_grep
mode_for_grep="${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="${mode_from_config:1}"
fi
local stat_output
stat_output=""
if ! stat_output="$(stat -c "%n %a %U %G" "${fso_without_trailing_slash}")"; then
echo "ERROR: failed to run 'stat' for fso_without_trailing_slash: '${fso_without_trailing_slash}'!" >&2
continue
fi
local arr file_name existing_mode existing_owner existing_group
IFS=" " read -r -a arr <<< "${stat_output}"
file_name="${arr[0]}"
existing_mode="${arr[1]}"
existing_owner="${arr[2]}"
existing_group="${arr[3]}"
if test "${#arr[@]}" = 0; then
echo "ERROR: arr is empty. stat_output: '${stat_output}' | line: '${line}'" >&2
continue
fi
if test -z "${file_name}"; then
echo "ERROR: file_name is empty. stat_output: '${stat_output}' | line: '${line}'" >&2
continue
fi
if test -z "${existing_mode}"; then
echo "ERROR: existing_mode is empty. stat_output: '${stat_output}' | line: '${line}'" >&2
continue
fi
if test -z "${existing_owner}"; then
echo "ERROR: existing_owner is empty. stat_output: '${stat_output}' | line: '${line}'" >&2
continue
fi
if test -z "${existing_group}"; then
echo "ERROR: ${existing_group} is empty. stat_output: '${stat_output}' | line: '${line}'" >&2
continue
fi
## Check there is an entry for the fso.
##
## example: dpkg-statoverride --list | grep /home
## output:
## root root 755 /home
##
## dpkg-statoverride does not show leading '0'.
local dpkg_statoverride_list_output=""
local dpkg_statoverride_list_exit_code=0
dpkg_statoverride_list_output="$(dpkg-statoverride --list "${fso_without_trailing_slash}")" || {
dpkg_statoverride_list_exit_code=$?
true
}
if test "${dpkg_statoverride_list_exit_code}" = "0"; then
true "There is an fso entry. Check if owner/group/mode match."
local grep_line
grep_line="${owner_from_config} ${group_from_config} ${mode_for_grep} ${fso_without_trailing_slash}"
if echo "${dpkg_statoverride_list_output}" | grep --quiet --fixed-strings "${grep_line}"; then
true "OK The owner/group/mode matches. No further action required."
else
true "The owner/group/mode do not match, therefore remove and re-add the entry to update it."
## 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
true "OK Existing mode already saved previously. No need to save again."
else
## Save existing_mode in separate database.
## Not using --update as not intending to enforce existing_mode.
# shellcheck disable=SC2086
echo_wrapper_silent_audit dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${fso_without_trailing_slash}"
fi
# shellcheck disable=SC2086
echo_wrapper_silent_ignore dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --remove "${fso_without_trailing_slash}"
## Remove from and add to real database.
echo_wrapper_silent_ignore dpkg-statoverride --remove "${fso_without_trailing_slash}"
echo_wrapper_audit dpkg-statoverride --add --update "${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_silent_audit dpkg-statoverride ${dpkg_admindir_parameter_new_mode} --add "${owner_from_config}" "${group_from_config}" "${mode_from_config}" "${fso_without_trailing_slash}"
fi
else
true "There is no fso entry. Therefore add one."
# shellcheck disable=SC2086
if dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --list "${fso_without_trailing_slash}" >/dev/null; then
true "OK Existing mode already saved previously. No need to save again."
else
## Save existing_mode in separate database.
## Not using --update as not intending to enforce existing_mode.
# shellcheck disable=SC2086
echo_wrapper_silent_audit dpkg-statoverride ${dpkg_admindir_parameter_existing_mode} --add "${existing_owner}" "${existing_group}" "${existing_mode}" "${fso_without_trailing_slash}"
fi
## Add to real database.
echo_wrapper_audit dpkg-statoverride --add --update "${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_silent_audit 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
continue
fi
if test "${capability_from_config}" = "none"; then
## https://forums.whonix.org/t/disable-suid-binaries/7706/45
## sudo setcap -r /bin/ping 2>/dev/null
## Failed to set capabilities on file '/bin/ping' (No data available)
## The value of the capability argument is not permitted for a file. Or
## the file is not a regular (non-symlink) file
## Therefore use echo_wrapper_ignore.
echo_wrapper_ignore setcap -r "${fso}"
getcap_output="$(getcap "${fso}")"
if test -n "${getcap_output}"; then
exit_code=205
echo "ERROR: removing capabilities for fso '${fso}' failed!" >&2
continue
fi
else
if ! capsh --print | grep --fixed-strings "Bounding set" | grep --quiet "${capability_from_config}"; then
echo "ERROR: capability_from_config '${capability_from_config}' does not exist!" >&2
continue
fi
## feature request: dpkg-statoverride: support for capabilities
## https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=502580
echo_wrapper_audit setcap "${capability_from_config}+ep" "${fso}"
fi
done <"${config_file}"
true "INFO: END parsing config_file: '${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=$(getent passwd)
echo "${passwd_file_contents_temp}" | tee "${store_dir}/private/passwd" >/dev/null
group_file_contents_temp=$(getent group)
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
echo "\
INFO: 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
Use 'meld' or another diff tool to view the differences:
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
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
echo "ERROR: cannot parse line: ${line}" >&2
continue
fi
true "owner: '${owner}' group: '${group}' mode: '${mode}' file_name: '${file_name}'"
if test "${remove_file}" = "all"; then
proceed=true
verbose=""
remove_one=false
else
if test "${remove_file}" = "${file_name}"; then
proceed=true
verbose="--verbose"
remove_one=true
else
proceed=false
verbose=""
fi
fi
if test "${proceed}" = "false"; then
continue
fi
if test "${remove_one}" = "true"; then
set -o xtrace
fi
if test -e "${file_name}"; then
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
chmod ${verbose} "${mode}" "${file_name}" || exit_code=203
else
echo "INFO: file_name: '${file_name}' - does not exist. This is likely normal."
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 ! "${remove_file}" = "all"; then
if test ! "${remove_one}" = "true"; then
echo "INFO: no file removed.
File '${remove_file}' has not removed from SUID Disabler and Permission Hardener during this invocation of this program.
Note: This is expected if already done earlier.
Note: This program expects the full path to the file. Example:
$0 disable /usr/bin/newgrp
The following syntax will not work:
$0 disable program-name
The following example will not work:
$0 disable newgrp
To remove all:
$0 disable all
This change might not be permanent (because of the permission-hardener.service systemd unit). For full instructions, see:
https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener
To view list of changed by SUID Disabler and Permission Hardener:
https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#View_List_of_Permissions_Changed_by_SUID_Disabler_and_Permission_Hardener
For re-enabling any specific SUID binary:
https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#Re-Enable_Specific_SUID_Binaries
For completely disabling SUID Disabler and Permission Hardener:
https://www.kicksecure.com/wiki/SUID_Disabler_and_Permission_Hardener#Disable_SUID_Disabler_and_Permission_Hardener"
fi
fi
}
check_root(){
if test "$(id -u)" != "0"; then
echo "ERROR: Not running as root, aborting."
exit 1
fi
}
usage(){
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 "${1:-}" in
"") usage;;
*) spare "${1}";;
esac
;;
-h|--help) usage 0;;
*) usage 1;;
esac
if test "${exit_code}" != "0"; then
echo "ERROR: Exiting with non-zero exit code: '${exit_code}'" >&2
fi
exit "${exit_code}"