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Merge remote-tracking branch 'github/master'
This commit is contained in:
Patrick Schleizer
commit
94627f0875
525
README.md
525
README.md
@ -1,48 +1,76 @@
|
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# enhances misc security settings #
|
||||
# Enhances miscellaneous security settings
|
||||
|
||||
Inspired by Kernel Self Protection Project (KSPP)
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||||
## Kernel hardening
|
||||
|
||||
* Implements most if not all recommended Linux kernel settings (sysctl) and
|
||||
kernel parameters by KSPP.
|
||||
This section is inspired by the Kernel Self Protection Project (KSPP). It
|
||||
implements all recommended Linux kernel settings by the KSPP and many
|
||||
more.
|
||||
|
||||
* https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project
|
||||
|
||||
kernel hardening:
|
||||
### sysctl
|
||||
|
||||
* deactivates Netfilter's connection tracking helper
|
||||
Netfilter's connection tracking helper module increases kernel attack
|
||||
surface by enabling superfluous functionality such as IRC parsing in
|
||||
the kernel. (!) Hence, this package disables this feature by shipping the
|
||||
`/etc/modprobe.d/30_security-misc.conf` configuration file.
|
||||
sysctl settings are configured via the `/etc/sysctl.d/30_security-misc.conf`
|
||||
configuration file.
|
||||
|
||||
* Kernel symbols in various files in `/proc` are hidden as they can be
|
||||
very useful for kernel exploits.
|
||||
* A kernel pointer points to a specific location in kernel memory. These
|
||||
can be very useful in exploiting the kernel so they are restricted to `CAP_SYSLOG`.
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||||
|
||||
* Kexec is disabled as it can be used to load a malicious kernel.
|
||||
`/etc/modprobe.d/30_security-misc.conf`
|
||||
* The kernel logs are restricted to `CAP_SYSLOG` as they can often leak sensitive
|
||||
information such as kernel pointers.
|
||||
|
||||
* ASLR effectiveness for mmap is increased.
|
||||
* The `ptrace()` system call is restricted to `CAP_SYS_PTRACE`.
|
||||
|
||||
* The TCP/IP stack is hardened by disabling ICMP redirect acceptance,
|
||||
ICMP redirect sending and source routing to prevent man-in-the-middle attacks,
|
||||
ignoring all ICMP requests, enabling TCP syncookies to prevent SYN flood
|
||||
attacks, enabling RFC1337 to protect against time-wait assassination
|
||||
attacks and enabling reverse path filtering to prevent IP spoofing and
|
||||
mitigate vulnerabilities such as CVE-2019-14899.
|
||||
* eBPF is restricted to `CAP_BPF` (`CAP_SYS_ADMIN` on kernel versions prior
|
||||
to 5.8) and JIT hardening techniques such as constant blinding are enabled.
|
||||
|
||||
* Avoids unintentional writes to attacker-controlled files.
|
||||
* Restricts performance events to `CAP_PERFMON` (`CAP_SYS_ADMIN` on kernel
|
||||
versions prior to 5.8).
|
||||
|
||||
* Prevents symlink/hardlink TOCTOU races.
|
||||
* Restricts loading line disciplines to `CAP_SYS_MODULE` to prevent unprivileged
|
||||
attackers from loading vulnerable line disciplines with the `TIOCSETD` ioctl which
|
||||
has been abused in a number of exploits before.
|
||||
|
||||
* SACK can be disabled as it is commonly exploited and is rarely used by
|
||||
uncommenting settings in file `/etc/sysctl.d/30_security-misc.conf`.
|
||||
* Restricts the `userfaultfd()` syscall to `CAP_SYS_PTRACE` as `userfaultfd()` is
|
||||
often abused to exploit use-after-free flaws.
|
||||
|
||||
* Slab merging is disabled as sometimes a slab can be used in a vulnerable
|
||||
way which an attacker can exploit.
|
||||
* Kexec is disabled as it can be used to load a malicious kernel and gain
|
||||
arbitrary code execution in kernel mode.
|
||||
|
||||
* Sanity checks and redzoning are enabled.
|
||||
* The bits of entropy used for mmap ASLR are increased, therefore improving
|
||||
its effectiveness.
|
||||
|
||||
* Memory zeroing at allocation and free time is enabled.
|
||||
* Prevents unintentional writes to attacker-controlled files.
|
||||
|
||||
* Prevents common symlink and hardlink TOCTOU races.
|
||||
|
||||
* Restricts the SysRq key so it can only be used for shutdowns and the
|
||||
Secure Attention Key.
|
||||
|
||||
* The kernel is only allowed to swap if it is absolutely necessary. This
|
||||
prevents writing potentially sensitive contents of memory to disk.
|
||||
|
||||
* TCP timestamps are disabled as it can allow detecting the system time.
|
||||
|
||||
### Boot parameters
|
||||
|
||||
Boot parameters are configured via the `/etc/modprobe.d/30_security-misc.conf`
|
||||
configuration file.
|
||||
|
||||
* Slab merging is disabled which significantly increases the difficulty of
|
||||
heap exploitation by preventing overwriting objects from merged caches and
|
||||
by making it harder to influence slab cache layout.
|
||||
|
||||
* Sanity checks are enabled which add various checks to prevent corruption
|
||||
in certain slab operations.
|
||||
|
||||
* Redzoning is enabled which adds extra areas around slabs that detect when
|
||||
a slab is overwritten past its real size which can help detect overflows.
|
||||
|
||||
* Memory zeroing at allocation and free time is enabled to mitigate some
|
||||
use-after-free vulnerabilities and erase sensitive information in memory.
|
||||
|
||||
* Page allocator freelist randomization is enabled.
|
||||
|
||||
* The machine check tolerance level is decreased which makes the kernel panic
|
||||
on uncorrectable errors in ECC memory that could be exploited.
|
||||
@ -50,293 +78,330 @@ on uncorrectable errors in ECC memory that could be exploited.
|
||||
* Kernel Page Table Isolation is enabled to mitigate Meltdown and increase
|
||||
KASLR effectiveness.
|
||||
|
||||
* Enables all mitigations for CPU vulnerabilities and disables SMT.
|
||||
* vsyscalls are disabled as they are obsolete, are at fixed addresses and thus,
|
||||
are a potential target for ROP.
|
||||
|
||||
* A systemd service clears System.map on boot as these contain kernel symbols
|
||||
that could be useful to an attacker.
|
||||
`/etc/kernel/postinst.d/30_remove-system-map`
|
||||
`/lib/systemd/system/remove-system-map.service`
|
||||
`/usr/lib/security-misc/remove-system.map`
|
||||
* The kernel panics on oopses to thwart certain kernel exploits.
|
||||
|
||||
* Coredumps are disabled as they may contain important information such as
|
||||
encryption keys or passwords.
|
||||
`/etc/security/limits.d/30_security-misc.conf`
|
||||
`/etc/sysctl.d/30_security-misc.conf`
|
||||
`/lib/systemd/coredump.conf.d/30_security-misc.conf`
|
||||
* All mitigations for known CPU vulnerabilities are enabled and SMT is
|
||||
disabled.
|
||||
|
||||
* The thunderbolt and firewire kernel modules are blacklisted as they can be
|
||||
used for DMA (Direct Memory Access) attacks.
|
||||
* IOMMU is enabled to prevent DMA attacks.
|
||||
|
||||
* IOMMU is enabled with a boot parameter to prevent DMA attacks.
|
||||
### Blacklisted kernel modules
|
||||
|
||||
* Bluetooth is blacklisted to reduce attack surface. Bluetooth also has
|
||||
Certain kernel modules are blacklisted to reduce attack surface via the
|
||||
`/etc/modprobe.d/30_security-misc.conf` configuration file.
|
||||
|
||||
* Deactivates Netfilter's connection tracking helper — this module
|
||||
increases kernel attack surface by enabling superfluous functionality
|
||||
such as IRC parsing in the kernel. Hence, this feature is disabled.
|
||||
|
||||
* Uncommon network protocols are blacklisted. This includes:
|
||||
|
||||
DCCP - Datagram Congestion Control Protocol
|
||||
|
||||
SCTP - Stream Control Transmission Protocol
|
||||
|
||||
RDS - Reliable Datagram Sockets
|
||||
|
||||
TIPC - Transparent Inter-process Communication
|
||||
|
||||
HDLC - High-Level Data Link Control
|
||||
|
||||
AX25 - Amateur X.25
|
||||
|
||||
NetRom
|
||||
|
||||
X25
|
||||
|
||||
ROSE
|
||||
|
||||
DECnet
|
||||
|
||||
Econet
|
||||
|
||||
af_802154 - IEEE 802.15.4
|
||||
|
||||
IPX - Internetwork Packet Exchange
|
||||
|
||||
AppleTalk
|
||||
|
||||
PSNAP - Subnetwork Access Protocol
|
||||
|
||||
p8023 - Novell raw IEEE 802.3
|
||||
|
||||
p8022 - IEEE 802.2
|
||||
|
||||
CAN — Controller Area Network
|
||||
|
||||
ATM
|
||||
|
||||
* Bluetooth is also blacklisted to reduce attack surface. Bluetooth has
|
||||
a history of security concerns.
|
||||
https://en.wikipedia.org/wiki/Bluetooth#History_of_security_concerns
|
||||
`/etc/modprobe.d/30_security-misc.conf`
|
||||
|
||||
* A systemd service restricts `/proc/cpuinfo`, `/proc/bus`, `/proc/scsi` and
|
||||
`/sys` to the root user only. This hides a lot of hardware identifiers from
|
||||
unprivileged users and increases security as `/sys` exposes a lot of
|
||||
information that shouldn't be accessible to unprivileged users. As this will
|
||||
break many things, it is disabled by default and can optionally be enabled by
|
||||
running `systemctl enable hide-hardware-info.service` as root.
|
||||
`/usr/lib/security-misc/hide-hardware-info`
|
||||
`/lib/systemd/system/hide-hardware-info.service`
|
||||
`/lib/systemd/system/user@.service.d/sysfs.conf`
|
||||
`/etc/hide-hardware-info.d/30_default.conf`
|
||||
* The Thunderbolt and FireWire kernel modules are blacklisted as they are
|
||||
often vulnerable to DMA attacks.
|
||||
|
||||
* The vivid kernel module is only required for testing and has been the cause
|
||||
of multiple vulnerabilities so it is blacklisted.
|
||||
|
||||
* The MSR kernel module is blacklisted to prevent CPU MSRs from being
|
||||
abused to write to arbitrary memory.
|
||||
|
||||
* Vsyscalls are disabled as they are obsolete, are at fixed addresses and are
|
||||
a target for ROP.
|
||||
### Other
|
||||
|
||||
* Page allocator freelist randomization is enabled.
|
||||
* A systemd service clears the System.map file on boot as these contain kernel
|
||||
pointers. The file is completely overwritten with zeroes to ensure it cannot
|
||||
be recovered. See:
|
||||
|
||||
* The vivid kernel module is blacklisted as it's only required for testing
|
||||
and has been the cause of multiple vulnerabilities.
|
||||
`/etc/kernel/postinst.d/30_remove-system-map`
|
||||
|
||||
`/lib/systemd/system/remove-system-map.service`
|
||||
|
||||
`/usr/lib/security-misc/remove-system.map`
|
||||
|
||||
* Coredumps are disabled as they may contain important information such as
|
||||
encryption keys or passwords. See:
|
||||
|
||||
`/etc/security/limits.d/30_security-misc.conf`
|
||||
|
||||
`/etc/sysctl.d/30_security-misc.conf`
|
||||
|
||||
`/lib/systemd/coredump.conf.d/30_security-misc.conf`
|
||||
|
||||
* An initramfs hook sets the sysctl values in `/etc/sysctl.conf` and
|
||||
`/etc/sysctl.d` before init is executed so sysctl hardening is enabled
|
||||
as early as possible.
|
||||
|
||||
* The kernel panics on oopses to prevent it from continuing to run a flawed
|
||||
process and to deter brute forcing.
|
||||
## Network hardening
|
||||
|
||||
* Restricts the SysRq key so it can only be used for shutdowns and the
|
||||
Secure Attention Key.
|
||||
* TCP syncookies are enabled to prevent SYN flood attacks.
|
||||
|
||||
* Restricts loading line disciplines to `CAP_SYS_MODULE`.
|
||||
* ICMP redirect acceptance, ICMP redirect sending, source routing and
|
||||
IPv6 router advertisements are disabled to prevent man-in-the-middle attacks.
|
||||
|
||||
* Restricts the `userfaultfd()` syscall to root.
|
||||
* The kernel is configured to ignore all ICMP requests to avoid Smurf attacks,
|
||||
make the device more difficult to enumerate on the network and prevent clock
|
||||
fingerprinting through ICMP timestamps.
|
||||
|
||||
Improve Entropy Collection
|
||||
* RFC1337 is enabled to protect against time-wait assassination attacks by
|
||||
dropping RST packets for sockets in the time-wait state.
|
||||
|
||||
* Load `jitterentropy_rng` kernel module.
|
||||
`/usr/lib/modules-load.d/30_security-misc.conf`
|
||||
* Reverse path filtering is enabled to prevent IP spoofing and mitigate
|
||||
vulnerabilities such as CVE-2019-14899.
|
||||
|
||||
## Entropy collection improvements
|
||||
|
||||
* The `jitterentropy_rng` kernel module is loaded as early as possible
|
||||
during boot to gather more entropy via the
|
||||
`/usr/lib/modules-load.d/30_security-misc.conf` configuration file.
|
||||
|
||||
* Distrusts the CPU for initial entropy at boot as it is not possible to
|
||||
audit, may contain weaknesses or a backdoor.
|
||||
* https://en.wikipedia.org/wiki/RDRAND#Reception
|
||||
* https://twitter.com/pid_eins/status/1149649806056280069
|
||||
* For more references, see:
|
||||
* `/etc/default/grub.d/40_distrust_cpu.cfg`
|
||||
audit, may contain weaknesses or a backdoor. For references, see:
|
||||
`/etc/default/grub.d/40_distrust_cpu.cfg`
|
||||
|
||||
* Gathers more entropy during boot if using the linux-hardened kernel patch.
|
||||
|
||||
Uncommon network protocols are blacklisted:
|
||||
These are rarely used and may have unknown vulnerabilities.
|
||||
`/etc/modprobe.d/30_security-misc.conf`
|
||||
The network protocols that are blacklisted are:
|
||||
## Restrictive mount options
|
||||
|
||||
* DCCP - Datagram Congestion Control Protocol
|
||||
* SCTP - Stream Control Transmission Protocol
|
||||
* RDS - Reliable Datagram Sockets
|
||||
* TIPC - Transparent Inter-process Communication
|
||||
* HDLC - High-Level Data Link Control
|
||||
* AX25 - Amateur X.25
|
||||
* NetRom
|
||||
* X25
|
||||
* ROSE
|
||||
* DECnet
|
||||
* Econet
|
||||
* af_802154 - IEEE 802.15.4
|
||||
* IPX - Internetwork Packet Exchange
|
||||
* AppleTalk
|
||||
* PSNAP - Subnetwork Access Protocol
|
||||
* p8023 - Novell raw IEEE 802.3
|
||||
* p8022 - IEEE 802.2
|
||||
`/home`, `/tmp`, `/dev/shm` and `/run` are remounted with the `nosuid` and `nodev`
|
||||
mount options to prevent execution of setuid or setgid binaries and creation of
|
||||
devices on those filesystems.
|
||||
|
||||
user restrictions:
|
||||
Optionally, they can also be mounted with `noexec` to prevent execution of any
|
||||
binary. To opt-in to applying `noexec`, execute `touch /etc/noexec` as root
|
||||
and reboot.
|
||||
|
||||
* remount `/home`, `/tmp`, `/dev/shm` and `/run` with `nosuid,nodev`
|
||||
(default) and `noexec` (opt-in). To disable this, run
|
||||
`sudo touch /etc/remount-disable`. To opt-in `noexec`, run
|
||||
`sudo touch /etc/noexec` and reboot (easiest).
|
||||
Alternatively file `/usr/local/etc/remount-disable` or file
|
||||
`/usr/local/etc/noexec` could be used.
|
||||
`/lib/systemd/system/remount-secure.service`
|
||||
`/usr/lib/security-misc/remount-secure`
|
||||
To disable this, execute `touch /etc/remount-disable` as root.
|
||||
|
||||
* An optional systemd service mounts `/proc` with `hidepid=2` at boot to
|
||||
prevent users from seeing each other's processes. Not enabled because not
|
||||
compatible with pkexec.
|
||||
Alternatively, file `/usr/local/etc/remount-disable` or `/usr/local/etc/noexec`
|
||||
could be used.
|
||||
|
||||
* The kernel logs are restricted to root only.
|
||||
|
||||
* The BPF JIT compiler is restricted to the root user and is hardened.
|
||||
|
||||
* The ptrace system call is restricted to the root user only.
|
||||
|
||||
restricts access to the root account:
|
||||
## Root access restrictions
|
||||
|
||||
* `su` is restricted to only users within the group `sudo` which prevents
|
||||
users from using `su` to gain root access or to switch user accounts.
|
||||
users from using `su` to gain root access or to switch user accounts —
|
||||
`/usr/share/pam-configs/wheel-security-misc`
|
||||
(Which results in a change in file `/etc/pam.d/common-auth`.)
|
||||
(which results in a change in file `/etc/pam.d/common-auth`).
|
||||
|
||||
* Add user `root` to group `sudo`. This is required to make above work so
|
||||
login as a user in a virtual console is still possible.
|
||||
`debian/security-misc.postinst`
|
||||
* Add user `root` to group `sudo`. This is required due to the above restriction so
|
||||
that logging in from a virtual console is still possible — `debian/security-misc.postinst`
|
||||
|
||||
* Abort login for users with locked passwords.
|
||||
`/usr/lib/security-misc/pam-abort-on-locked-password`
|
||||
* Abort login for users with locked passwords —
|
||||
`/usr/lib/security-misc/pam-abort-on-locked-password`.
|
||||
|
||||
* Logging into the root account from a virtual, serial, whatnot console is
|
||||
prevented by shipping an existing and empty `/etc/securetty`.
|
||||
(Deletion of `/etc/securetty` has a different effect.)
|
||||
`/etc/securetty.security-misc`
|
||||
prevented by shipping an existing and empty `/etc/securetty` file
|
||||
(deletion of `/etc/securetty` has a different effect).
|
||||
|
||||
* Console Lockdown.
|
||||
Allow members of group 'console' to use console.
|
||||
Everyone else except members of group
|
||||
'console-unrestricted' are restricted from using console using ancient,
|
||||
unpopular login methods such as using `/bin/login` over networks, which might
|
||||
be exploitable. (CVE-2001-0797) Using pam_access.
|
||||
Not enabled by default in this package since this package does not know which
|
||||
users shall be added to group 'console' and would break console.
|
||||
`/usr/share/pam-configs/console-lockdown-security-misc`
|
||||
`/etc/security/access-security-misc.conf`
|
||||
This package does not yet automatically lock the root account password. It
|
||||
is not clear if this would be sane in such a package although, it is recommended
|
||||
to lock and expire the root account.
|
||||
|
||||
Protect Linux user accounts against brute force attacks.
|
||||
Lock user accounts after 50 failed login attempts using `pam_tally2`.
|
||||
`/usr/share/pam-configs/tally2-security-misc`
|
||||
In new Whonix builds, root account will be locked by package
|
||||
dist-base-files.
|
||||
|
||||
informational output during Linux PAM:
|
||||
See:
|
||||
|
||||
* https://www.whonix.org/wiki/Root
|
||||
* https://www.whonix.org/wiki/Dev/Permissions
|
||||
* https://forums.whonix.org/t/restrict-root-access/7658
|
||||
|
||||
However, a locked root password will break rescue and emergency shell.
|
||||
Therefore, this package enables passwordless rescue and emergency shell.
|
||||
This is the same solution that Debian will likely adapt for Debian
|
||||
installer: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=802211
|
||||
|
||||
See:
|
||||
|
||||
* `/etc/systemd/system/emergency.service.d/override.conf`
|
||||
* `/etc/systemd/system/rescue.service.d/override.conf`
|
||||
|
||||
Adverse security effects can be prevented by setting up BIOS password
|
||||
protection, GRUB password protection and/or full disk encryption.
|
||||
|
||||
## Console lockdown
|
||||
|
||||
This uses pam_access to allow members of group `console` to use console but
|
||||
restrict everyone else (except members of group `console-unrestricted`) from
|
||||
using console with ancient, unpopular login methods such as `/bin/login`
|
||||
over networks as this might be exploitable. (CVE-2001-0797)
|
||||
|
||||
This is not enabled by default in this package since this package does not
|
||||
know which users shall be added to group 'console' and thus, would break console.
|
||||
|
||||
See:
|
||||
|
||||
* `/usr/share/pam-configs/console-lockdown-security-misc`
|
||||
* `/etc/security/access-security-misc.conf`
|
||||
|
||||
## Brute force attack protection
|
||||
|
||||
User accounts are locked after 50 failed login attempts using `pam_tally2`.
|
||||
|
||||
Informational output during Linux PAM:
|
||||
|
||||
* Show failed and remaining password attempts.
|
||||
* Document unlock procedure if Linux user account got locked.
|
||||
* Point out, that there is no password feedback for `su`.
|
||||
* Explain locked (root) account if locked.
|
||||
* Point out that there is no password feedback for `su`.
|
||||
* Explain locked root account if locked.
|
||||
|
||||
See:
|
||||
|
||||
* `/usr/share/pam-configs/tally2-security-misc`
|
||||
* `/usr/lib/security-misc/pam_tally2-info`
|
||||
* `/usr/lib/security-misc/pam-abort-on-locked-password`
|
||||
|
||||
access rights restrictions:
|
||||
## Access rights restrictions
|
||||
|
||||
* Strong Linux User Account Separation.
|
||||
Removes read, write and execute access for others for all users who have
|
||||
home folders under folder `/home` by running for example
|
||||
"chmod o-rwx /home/user"
|
||||
during package installation, upgrade or pam `mkhomedir`. This will be done
|
||||
only once per folder in folder `/home` so users who wish to relax file
|
||||
permissions are free to
|
||||
do so. This is to protect previously created files in user home folder which
|
||||
were previously created with lax file permissions prior installation of this
|
||||
package.
|
||||
`debian/security-misc.postinst`
|
||||
`/usr/lib/security-misc/permission-lockdown`
|
||||
`/usr/share/pam-configs/mkhomedir-security-misc`
|
||||
### Strong user account separation
|
||||
|
||||
* SUID / GUID removal and permission hardening.
|
||||
A systemd service removed SUID / GUID from non-essential binaries as these are
|
||||
often used in privilege escalation attacks.
|
||||
It is disabled by default for now during testing and can optionally be enabled
|
||||
by running `systemctl enable permission-hardening.service` as root.
|
||||
https://forums.whonix.org/t/disable-suid-binaries/7706
|
||||
`/usr/lib/security-misc/permission-hardening`
|
||||
`/lib/systemd/system/permission-hardening.service`
|
||||
`/etc/permission-hardening.d/30_default.conf`
|
||||
Read, write and execute access for "others" are removed during package
|
||||
installation, upgrade or PAM `mkhomedir` for all users who have home
|
||||
folders in `/home` by running, for example:
|
||||
|
||||
access rights relaxations:
|
||||
```
|
||||
chmod o-rwx /home/user
|
||||
```
|
||||
|
||||
Redirect calls for `pkexec` to `lxqt-sudo` because `pkexec` is incompatible
|
||||
with `hidepid`.
|
||||
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=860040
|
||||
https://forums.whonix.org/t/cannot-use-pkexec/8129
|
||||
`/usr/bin/pkexec.security-misc`
|
||||
This will be done only once per folder in `/home` so users who wish to
|
||||
relax file permissions are free to do so. This is to protect files in a
|
||||
home folder that were previously created with lax file permissions prior
|
||||
to the installation of this package.
|
||||
|
||||
This package does (not yet) automatically lock the root account password.
|
||||
It is not clear that would be sane in such a package.
|
||||
It is recommended to lock and expire the root account.
|
||||
In new Whonix builds, root account will be locked by package
|
||||
dist-base-files.
|
||||
https://www.whonix.org/wiki/Root
|
||||
https://www.whonix.org/wiki/Dev/Permissions
|
||||
https://forums.whonix.org/t/restrict-root-access/7658
|
||||
However, a locked root password will break rescue and emergency shell.
|
||||
Therefore this package enables passwordless rescue and emergency shell.
|
||||
This is the same solution that Debian will likely adapt for Debian
|
||||
installer.
|
||||
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=802211
|
||||
Adverse security effects can be prevented by setting up BIOS password
|
||||
protection, grub password protection and/or full disk encryption.
|
||||
`/etc/systemd/system/emergency.service.d/override.conf`
|
||||
`/etc/systemd/system/rescue.service.d/override.conf`
|
||||
See:
|
||||
|
||||
Let the kernel only swap if it is absolutely necessary.
|
||||
`/etc/sysctl.d/30_security-misc.conf`
|
||||
* `debian/security-misc.postinst`
|
||||
* `/usr/lib/security-misc/permission-lockdown`
|
||||
* `/usr/share/pam-configs/mkhomedir-security-misc`
|
||||
|
||||
Disables TCP Time Stamps:
|
||||
### SUID / SGID removal and permission hardening
|
||||
|
||||
TCP time stamps (RFC 1323) allow for tracking clock
|
||||
information with millisecond resolution. This may or may not allow an
|
||||
attacker to learn information about the system clock at such
|
||||
a resolution, depending on various issues such as network lag.
|
||||
This information is available to anyone who monitors the network
|
||||
somewhere between the attacked system and the destination server.
|
||||
It may allow an attacker to find out how long a given
|
||||
system has been running, and to distinguish several
|
||||
systems running behind NAT and using the same IP address. It might
|
||||
also allow one to look for clocks that match an expected value to find the
|
||||
public IP used by a user.
|
||||
A systemd service removes SUID / SGID bits from non-essential binaries as
|
||||
these are often used in privilege escalation attacks. It is disabled by
|
||||
default for now during testing and can optionally be enabled by running
|
||||
`systemctl enable permission-hardening.service` as root.
|
||||
|
||||
Hence, this package disables this feature by shipping the
|
||||
`/etc/sysctl.d/30_security-misc.conf` configuration file.
|
||||
See:
|
||||
|
||||
Note that TCP time stamps normally have some usefulness. They are
|
||||
needed for:
|
||||
* `/usr/lib/security-misc/permission-hardening`
|
||||
* `/lib/systemd/system/permission-hardening.service`
|
||||
* `/etc/permission-hardening.d`
|
||||
* https://forums.whonix.org/t/disable-suid-binaries/7706
|
||||
|
||||
* the TCP protection against wrapped sequence numbers; however, to
|
||||
trigger a wrap, one needs to send roughly 2^32 packets in one
|
||||
minute: as said in RFC 1700, "The current recommended default
|
||||
time to live (TTL) for the Internet Protocol (IP) [45,105] is 64".
|
||||
So, this probably won't be a practical problem in the context
|
||||
of Anonymity Distributions.
|
||||
* "Round-Trip Time Measurement", which is only useful when the user
|
||||
manages to saturate their connection. When using Anonymity Distributions,
|
||||
probably the limiting factor for transmission speed is rarely the capacity
|
||||
of the user connection.
|
||||
### Access rights relaxations
|
||||
|
||||
Application specific hardening:
|
||||
Calls to `pkexec` are redirected to `lxqt-sudo` because `pkexec` is
|
||||
incompatible with `hidepid=2`.
|
||||
|
||||
* Enables APT seccomp-BPF sandboxing. `/etc/apt/apt.conf.d/40sandbox`
|
||||
See:
|
||||
|
||||
* `/usr/bin/pkexec.security-misc`
|
||||
* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=860040
|
||||
* https://forums.whonix.org/t/cannot-use-pkexec/8129
|
||||
|
||||
## Application-specific hardening
|
||||
|
||||
* Enables APT seccomp-BPF sandboxing — `/etc/apt/apt.conf.d/40sandbox`.
|
||||
* Deactivates previews in Dolphin.
|
||||
* Deactivates previews in Nautilus.
|
||||
`/usr/share/glib-2.0/schemas/30_security-misc.gschema.override`
|
||||
* Deactivates previews in Nautilus —
|
||||
`/usr/share/glib-2.0/schemas/30_security-misc.gschema.override`.
|
||||
* Deactivates thumbnails in Thunar.
|
||||
* Enables punycode (`network.IDN_show_punycode`) by default in Thunderbird
|
||||
to make phishing attacks more difficult. Fixing URL not showing real Domain
|
||||
Name (Homograph attack).
|
||||
* Displays domain names in punycode (`network.IDN_show_punycode`) in
|
||||
Thunderbird to prevent IDN homograph attacks (a form of phishing).
|
||||
* Security and privacy enhancements for gnupg's config file
|
||||
`/etc/skel/.gnupg/gpg.conf`. See also:
|
||||
|
||||
https://raw.github.com/ioerror/torbirdy/master/gpg.conf
|
||||
|
||||
https://github.com/ioerror/torbirdy/pull/11
|
||||
|
||||
Want more? Look into these:
|
||||
## Opt-in hardening
|
||||
|
||||
Some hardening is opt-in as it causes too much breakage to be enabled by
|
||||
default.
|
||||
|
||||
* TCP SACK can be disabled as it is commonly exploited and is rarely used by
|
||||
uncommenting settings in the `/etc/sysctl.d/30_security-misc.conf`
|
||||
configuration file.
|
||||
|
||||
* An optional systemd service mounts `/proc` with `hidepid=2` at boot to
|
||||
prevent users from seeing another user's processes. This is disabled by
|
||||
default because it is incompatible with `pkexec`. It can be enabled by
|
||||
executing `systemctl enable proc-hidepid.service` as root.
|
||||
|
||||
* A systemd service restricts `/proc/cpuinfo`, `/proc/bus`, `/proc/scsi` and
|
||||
`/sys` to the root user. This hides a lot of hardware identifiers from
|
||||
unprivileged users and increases security as `/sys` exposes a lot of
|
||||
information that shouldn't be accessible to unprivileged users. As this will
|
||||
break many things, it is disabled by default and can optionally be enabled by
|
||||
executing `systemctl enable hide-hardware-info.service` as root.
|
||||
|
||||
## Related
|
||||
|
||||
* Linux Kernel Runtime Guard (LKRG)
|
||||
* tirdad - TCP ISN CPU Information Leak Protection.
|
||||
* Whonix ™ - Anonymous Operating System
|
||||
* Kicksecure ™ - A Security-hardened, Non-anonymous Linux Distribution
|
||||
* SecBrowser ™ - A Security-hardened, Non-anonymous Browser
|
||||
* And more.
|
||||
* https://www.whonix.org/wiki/Linux_Kernel_Runtime_Guard_LKRG
|
||||
* https://github.com/Whonix/tirdad
|
||||
* https://www.whonix.org
|
||||
* https://www.whonix.org/wiki/Kicksecure
|
||||
* https://www.whonix.org/wiki/SecBrowser
|
||||
* https://github.com/Whonix
|
||||
|
||||
Discussion:
|
||||
## Discussion
|
||||
|
||||
Happening primarily in Whonix forums.
|
||||
|
||||
https://forums.whonix.org/t/kernel-hardening/7296
|
||||
## How to install `security-misc` ##
|
||||
|
||||
## How to install `security-misc`
|
||||
|
||||
See https://www.whonix.org/wiki/Security-misc#install
|
||||
|
||||
## How to Build deb Package from Source Code ##
|
||||
## How to Build deb Package from Source Code
|
||||
|
||||
Can be build using standard Debian package build tools such as:
|
||||
|
||||
@ -349,11 +414,11 @@ See instructions. (Replace `generic-package` with the actual name of this packag
|
||||
* **A)** [easy](https://www.whonix.org/wiki/Dev/Build_Documentation/generic-package/easy), _OR_
|
||||
* **B)** [including verifying software signatures](https://www.whonix.org/wiki/Dev/Build_Documentation/generic-package)
|
||||
|
||||
## Contact ##
|
||||
## Contact
|
||||
|
||||
* [Free Forum Support](https://forums.whonix.org)
|
||||
* [Professional Support](https://www.whonix.org/wiki/Professional_Support)
|
||||
|
||||
## Donate ##
|
||||
## Donate
|
||||
|
||||
`security-misc` requires [donations](https://www.whonix.org/wiki/Donate) to stay alive!
|
||||
|
||||
Loading…
Reference in New Issue
Block a user