Firejail
Firejail 是一個易於使用的 SUID 沙盒程序，它通過使用 Linux 命名空間、seccomp-bpf 和 Linux 功能來限制不受信任的應用程式的運行環境以降低安全漏洞被利用的風險。
安裝[編輯 | 編輯原始碼]
安裝 firejail包 或者 firejail-gitAUR 包. 還有可以與 Firejail 一起使用的 GUI 應用程式, firetools包.
/etc/firejail/firefox.profile），但大多數提供的配置文件仍然嚴重依賴黑名單。這意味着，任何沒有被配置文件明確禁止的東西都會被應用程式訪問。例如，如果你在/mnt/btrfs中有 btrfs 快照，沙盒裏的程序可能被禁止訪問$HOME/.ssh，但仍能訪問/mnt/btrfs/@some-snapshot/$HOME/.ssh。請確保檢查您的配置文件。見#測試配置文件。配置[編輯 | 編輯原始碼]
大多數用户不需要任何自定義配置，並且可以繼續 #使用方法.
Firejail 使用配置文件為其中執行的每個應用程式設置安全保護 - 您可以在 /etc/firejail/application.profile 中找到默認配置文件. 如果您需要為未包含的應用程式自定義配置文件，或者希望修改默認值, 您可以在 ~/.config/firejail/ 目錄中放置新規則或默認值副本. 一個應用程式可能有多個自定義配置文件，並且您可以在多個應用程式之間共享同一個配置文件.
如果 firejail 沒有特定應用程式的配置文件，它會使用其限制性的系統範圍默認配置文件。如果沒有事先創建自定義且限制較少的配置文件，這可能會導致應用程式無法按預期運行。
使用方法[編輯 | 編輯原始碼]
要使用 firejail 對該應用程式的默認保護（默認配置文件）執行應用程式，請執行以下命令 :
$ firejail <应用程序名称>
一次性添加到默認配置文件可以作為命令行選項添加（參見 firejail(1)）。 例如，要執行帶有 seccomp 保護的 okular，請執行以下命令 :
$ firejail --seccomp okular
您可以為單個程序定義多個非默認配置文件。 創建配置文件後，您可以通過執行來使用它 :
$ firejail --profile=/absolute/path/to/profile <program name>
默認配置使用 Firejail[編輯 | 編輯原始碼]
默認情況下將 Firejail 用於具有配置文件的所有應用程式 , 使用 sudo 運行 firecfg 工具:
$ sudo firecfg
這將在/usr/local/bin中創建指向/usr/bin/firejail，用於 Firejail 有默認或自定配置文件的程序的符號連結。請注意，firecfg(1) 只與/etc/firejail/firecfg.config中列出的程序建立符號連結。某些命令行界面的程序是不存在的，例如 tar、curl 和 git。這些程序需要手動建立符號連結。請參閱 Profiles not in firecfg #2507 了解為什麼不包括這些程序。firecfg 還將當前用户加入 Firejail 用户訪問數據庫，並檢查/usr/share/applications/*.desktop文件是否包含相應可執行文件的完整路徑，然後刪除完整路徑並將其複製到~/.local/share/applications/。這確保了/usr/local/bin中的符號連結將被使用，從而防止 Firejail 被繞過。如果您的系統中沒有安裝 sudo，請以 root 身份執行：
# firecfg
以及以一般用户執行：
$ firecfg --fix
以修復 .desktop 文件
在某些情況下，您可能需要手動修改~/.local/share/applications/中 ".desktop " 文件的Exec=行，以直接調用 Firejail。
/etc/pacman.d/hooks/firejail.hook
[Trigger] Type = Path Operation = Install Operation = Upgrade Operation = Remove Target = usr/bin/* Target = usr/local/bin/* Target = usr/share/applications/*.desktop [Action] Description = Configure symlinks in /usr/local/bin based on firecfg.config... When = PostTransaction Depends = firejail Exec = /bin/sh -c 'firecfg >/dev/null 2>&1'
要手動連結各個應用程式，請執行以下操作：
# ln -s /usr/bin/firejail /usr/local/bin/application
/usr/local/binmust be set before/usr/binand/binin thePATHenvironment variable.- To run a symbolic program with custom Firejail setting, simple prefix firejail as seen in #使用方法.
- For a daemon, you will need to overwrite the systemd unit file for that daemon to call firejail, see systemd#Editing provided units.
- Symbolic links to gzip and xz interfere with makepkg's ability to preload
libfakeroot.so. See BBS#230913.
Use with hardened_malloc[編輯 | 編輯原始碼]
hardened_mallocAUR is a hardened implementation of glibc's malloc() allocator, originally written for Android but extended for use on the desktop. While not integrated into glibc yet, it can be used selectively with LD_PRELOAD. The proper way to launch an application within firejail using hardened_malloc is demonstrated below. To make it permanent, you would need to create your own entry in /usr/local/bin for the desired application.
$ firejail --env=LD_PRELOAD='/usr/lib/libhardened_malloc.so' /usr/bin/firefox
Alternatively, add the following to a custom profile:
env LD_PRELOAD='/usr/lib/libhardened_malloc.so'
The various environment variables and settings that can be used to tune hardened_malloc can be found on its github page.
Enable AppArmor support[編輯 | 編輯原始碼]
Since 0.9.60-1, Firejail has supported more direct integration with AppArmor through a generic AppArmor profile. During installation, the profile, firejail-default, is placed in /etc/apparmor.d directory, and needs to be loaded into the kernel by running the following command as root:
# apparmor_parser -r /etc/apparmor.d/firejail-default
Local customizations of the apparmor profile are supported by editing the file /etc/apparmor.d/local/firejail-local
AppArmor is already enabled for a large number of Firejail profiles. There are several ways to enable AppArmor confinement on top of a Firejail security profile:
- Pass the
--apparmorflag to Firejail in the command line, e.g.$ firejail --apparmor firefox - Use a custom profile and add the
apparmorcommand. - Enable Apparmor globally in
/etc/firejail/globals.localand disable as needed through the use ofignore apparmorin/etc/firejail/<ProgramName>.local.
Note that enabling AppArmor by above methods always means that /etc/apparmor.d/firejail-default is used. If you rather want to use a specific AppArmor profile for an application, you have to use the above mentioned ignore apparmor command. However, that is not recommended, as using both Firejail and AppArmor for the same applications often creates problems.
Verifying Firejail is being used[編輯 | 編輯原始碼]
$ firejail --list
A more comprehensive output is produced by
$ firejail --tree
Creating custom profiles[編輯 | 編輯原始碼]
Whitelists and blacklists[編輯 | 編輯原始碼]
Blacklists are heavily used in various /etc/firejail/*.inc files which are included in most profiles. Blacklists are permissive:
- Deny access to a directory or file and permit everything else:
blacklist <directory/file> - Disable/undo/ignore blacklisting a directory or file already blacklisted, e.g., in an *.inc file:
noblacklist <directory/file>
The order in which they appear in a profile is important: noblacklist directives must be added above blacklist directives.
Whitelists block everything what is not explicitly whitelisted. They should not be used in profiles for applications that need access to random locations (e.g., text editors, image viewers/editors).
- Allow access to a directory or file and forbid everything else:
whitelist <directory/file> - Disable/undo/ignore whitelisting a directory or file already whitelisted, e.g., in an *.inc file:
nowhitelist <directory/file>
The order in which they appear in a profile is important: nowhitelist directives must be added above whitelist directives.
Whitelisting is always done before blacklisting. As mentioned, a whitelist directive blacklists everything else. A blacklist directive is therefore a fallback if there are no whitelist directives or if a whitelist directive is too permissive.
(no)blacklist and (no)whitelist directives are often used in combination. Example: /etc/firejail/disable-programs.inc (which is included in all profiles) contains the directive:
blacklist ${HOME}/.mozilla
in order to block access to that directory for all applications sandboxed by Firejail. /etc/firejail/firefox.profile must disable this directive and must add a whitelist directive to allow access to that directory (as the Firefox profile is a whitelisted profile):
noblacklist ${HOME}/.mozilla
whitelist ${HOME}/.mozilla
Profile writing[編輯 | 編輯原始碼]
The basic process is:
- Copy
/usr/share/doc/firejail/profile.templateto/etc/firejail/or~/.config/firejail/and rename it toProfileName.profilewhere ProfileName should match the name of the executable to be sandboxed - Change the line
include PROFILE.localtoinclude ProfileName.local - Gradually comment/uncomment the various options while checking at each stage that the application runs inside the new sandbox. Do not change the order of the sections in that template.
- Detailed explanations of the possible options for a Firejail profile can be found in the firejail-profile(5) man page
- Test the profile for security holes, see #Testing profiles
If you want to create a whitelisted profile (i.e. a profile which contains whitelist directives) you can build a whitelist of permitted locations by executing
$ firejail --build application
Keep in mind that a whitelisted profile is problematic for applications that need to access random locations (like text editors or file managers).
- The idea is to be as restrictive as possible, while still maintaining usability. This may involve sacrificing potentially dangerous functionality and a change in cavalier work habits.
- By default, seccomp filters work on a blacklist (which can be found in
/usr/share/doc/firejail/syscalls.txt). It is possible to useseccomp.keepto build a custom whitelist of filters for an application. [1]. A convenient way to automate these steps is to execute/usr/lib/firejail/syscalls.sh. If the application is still broken because of missing syscalls, you should follow the instructions at the bottom of/usr/share/doc/firejail/syscalls.txt.
Persistent local customisation[編輯 | 編輯原始碼]
The standard profile layout includes the capability to make persistent local customisations through the inclusion of .local files[2]. Basically, each officially supported profile contains the lines include ProgramName.local and include globals.local. These *.local files might be located in /etc/firejail or in ~/.config/firejail. Since the order of precedence is determined by which is read first, this makes for a very powerful way of making local customisations.
For example, with reference this firejail question, to globally enable Apparmor and disable Internet connectivity, one could simply create/edit /etc/firejail/globals.local to include the lines
# enable Apparmor and disable Internet globally net none apparmor
Then, to allow, for example, "curl" to connect to the internet, yet still maintain its apparmor confinement, one would create/edit /etc/firejail/curl.local to include the lines.
# enable internet for curl ignore net
Since curl.local is read before globals.local, ignore net overrides net none, and, as a bonus, the above changes would be persistent across future updates.
Testing profiles[編輯 | 編輯原始碼]
In order to test and audit a Firejail profile you may find the following to be useful:
firejail --debug $Program > $PathToOutputFileGives a detailed breakdown of the sandboxfirejail --debug-blacklists $Programandfirejail --debug-whitelists $Programshow the blacklisted and whitelisted directories and files for the current profile.firejail --debug-capsgives a list of caps supported by the current Firejail software build. This is useful when building a caps whitelist.firejail --helpfor a full list of--debugoptionsfiremon PIDmonitors the running process. Seefiremon --helpfor details- Executing
sudo jailchecktests running sandboxes. See the jailcheck(1) man page for details. - checksec包 may also be useful in testing which standard security features are being used
Firejail with Xorg[編輯 | 編輯原始碼]
On Xorg any program can listen to all keyboard input and record all screens. The purpose of sandboxing X11 is to restrict this behavior, which is especially problematic for complex programs working with potentially malicious input like browsers.
Xephyr and Xpra allow you to sandbox Xorg. Although Xpra provides full clipboard support, it is recommended to use Xephyr due to the very notable and permanent lag with nested X11 sessions.
For a complete setup with (not ideal) clipboard support (clipboard is still always shared), see Sakaki's Gentoo guide, especially the section about the clipboard and automatic rescaling.
Alternatively, if clipboard support is not needed but windows need to be managed, install a standalone window manager such as Openbox.
xephyr-screen WidthxHeight can be set in /etc/firejail/firejail.config where Width and Height are in pixels and based on your screen resolution.
To open the sandbox:
$ firejail --x11 --net=device openbox
device is your active network interface, which is needed to ensure that DNS works. Then right click and select your applications to run.
--net=device out of the command as DNS should work automatically.See the Firejail Wordpress site for a simpler guide.
According to the guide:
- The sandbox replaces the regular X11 server with Xpra or Xephyr server. This prevents X11 keyboard loggers and screenshot utilities from accessing the main X11 server.
Note that the statement:
- The only way to disable the abstract socket
@/tmp/.X11-unix/X0is by using a network namespace. If for any reasons you cannot use a network namespace, the abstract socket will still be visible inside the sandbox. Hackers can attach keylogger and screenshot programs to this socket.
is incorrect, xserverrc can be edited to -nolisten local, which disables the abstract sockets of X11 and helps isolate it.
Sandboxing a browser[編輯 | 編輯原始碼]
Openbox can be configured to start a certain browser at startup. program.profile is the respective profile contained in /etc/firejail, and --startup "command" is the command line used to start the program. For example, to start Chromium in the sandbox:
$ firejail --x11 --profile=/etc/firejail/chromium.profile openbox --startup "chromium"
Tips and tricks[編輯 | 編輯原始碼]
Hardening Firejail[編輯 | 編輯原始碼]
The security risk of Firejail being a SUID executable can be mitigated by adding the line
force-nonewprivs yes
to /etc/firejail/firejail.config. However, this can break specific applications. On Arch Linux, VirtualBox doesn't start anymore. With the linux-hardened包 kernel Wireshark and Chromium-based browsers are also affected.
Further hardening measures include creating a special firejail group with adding the user to that group and changing the file mode for the firejail executable. For details see here.
Paths containing spaces[編輯 | 編輯原始碼]
If you need to reference, whitelist, or blacklist a directory within a custom profile, such as with palemoonAUR, you must do so using the absolute path, without encapsulation or escapes:
/home/user/.moonchild productions
Private mode[編輯 | 編輯原始碼]
Firejail also includes a one time private mode, in which no mounts are made in the chroots to your home directory. In doing this, you can execute applications without performing any changes to disk. For example, to execute okular in private mode, do the following:
$ firejail --seccomp --private okular
Experimental improved tools[編輯 | 編輯原始碼]
Some of the Firejail developers recognized issues with the tools it ships with and made their own, improved versions of them.
- firecfg.py, an improved version of
firecfg. - fjp, a tool to interact with Firejail profiles.
- firejail-handler-http, which helps with opening HTTP(S) links properly when sandboxing applications.
- firejail-handler-extra, like above but handles other protocols.
Troubleshooting[編輯 | 編輯原始碼]
Firejail can be hard to debug. The symptoms of a misconfigured or otherwise unfitting setup range from random segmentation faults and hangs in the applications to simple error messages.
Some applications are harder to sandbox than others. For example web browsers and Electron applications tend to need more troubleshooting than others since there is much that can go wrong. It is crucial to check the FAQ and open issues first, since debugging can take quite some time.
Remove Firejail symbolic links[編輯 | 編輯原始碼]
To remove Firejail created symbolic links (e.g. reset to default):
# firecfg --clean
If you do not want to use Firejail for a specific application (e.g., because you prefer to rather confine it with AppArmor), you have to manually remove the related symbolic link:
# rm /usr/local/bin/application
As a subsequent execution of firecfg would re-add the removed symlinks, the respective applications should be commented in /etc/firejail/firecfg.config.
Verify if any leftovers of Desktop entries are still overruled by Firejail.
PulseAudio[編輯 | 編輯原始碼]
If Firejail causes PulseAudio issues with sandboxed applications [3], the following command may be used:
$ firecfg --fix-sound
This commands creates a custom ~/.config/pulse/client.conf file for the current user with enable-shm = no and possible other workarounds.
hidepid[編輯 | 編輯原始碼]
If the system uses the hidepid 內核參數, Firemon can only be run as root. This, among other things, will cause problems with the Firetools GUI incorrectly reporting "Capabilities", "Protocols" and the status of "Seccomp"[4].
Proprietary Nvidia drivers[編輯 | 編輯原始碼]
Some users report problems when using Firejail and proprietary graphic drivers from NVIDIA (e.g. [5], [6] or [7]). This can often be solved by disabling the noroot Firejail option in the application's profile file.
--net options and Linux kernel >=4.20.0[編輯 | 編輯原始碼]
There is a bug on firejail 0.5.96 with linux >= 4.20.0, see [8] and [9]
Example error message:
$ firejail --noprofile --net=eth0 ls Parent pid 8521, child pid 8522 Error send: arp.c:182 arp_check: Invalid argument Error: proc 8521 cannot sync with peer: unexpected EOF Peer 8522 unexpectedly exited with status 1
Warning: Cannot confine the application using AppArmor[編輯 | 編輯原始碼]
For some applications (e.g. Firefox [10]) starting with Firejail may result in warnings like:
Warning: Cannot confine the application using AppArmor. Maybe firejail-default AppArmor profile is not loaded into the kernel. As root, run "aa-enforce firejail-default" to load it.
When running the suggested command you might see:
ERROR: Cache read/write disabled: interface file missing. (Kernel needs AppArmor 2.4 compatibility patch.)
This means that AppArmor is not enabled as a kernel parameter, so you have to set it according to AppArmor#Installation.
/usr/bin/patch: **** Can't open patch file[編輯 | 編輯原始碼]
This means the PKGBUILD uses patch with the -i argument so a whitelist for $SRCDEST in /etc/makepkg.conf is needed.
Create the override patch.local with the value of your $SRCDEST:
whitelist /path/to/makepkg/sources
Changing the PKGBUILD to use stdin also works:
patch -p1 < ../file.patch
Graphical applications hang on start with AMDGPU[編輯 | 編輯原始碼]
Some graphical applications, e.g. Firefox and mpv, will hang on start when using AMDGPU with Mesa >= 19.3.4. See [11]. The issue is fixed upstream, so firejail-gitAUR should work. Alternatively, for all affected applications, add seccomp !kcmp to their profiles in etc/firejail. If they already have a seccomp statement, you can concatenate them as a comma-separated list, eg seccomp !chroot,!kcmp.
Daemonizing/backgrounded processes hang[編輯 | 編輯原始碼]
There is a known issue that prevents processes from daemonizing. There is currently no solution to this except not using Firejail to sandbox the affected application. Because it is a bug within Firejail, no configuration can solve this issue. Fortunately the applications mentioned in the issue usually do not have a large attack surface, so the risks of running them without a sandbox are comparatively low.
See also[編輯 | 編輯原始碼]
- Firejail GitHub project page
- bubblewrap, a minimal alternative to Firejail