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operating-systems: buer: Add kicksecure kernel arguments and sysctl settings

sioyek
Luis Guilherme Coelho 2024-02-12 01:59:53 -03:00
parent 1f5167d9be
commit 57c0fc0644
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GPG Key ID: 1F2E76ACE3F531C8
2 changed files with 484 additions and 6 deletions
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464
modules/kicksecure-configs.scm Normal file
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;; Contents extracted from Kicksecure's resources.
(define-module (radix modules kicksecure-configs)
#:export (kicksecure-delete
%kicksecure-kernel-arguments
%kicksecure-sysctl-rules))
(define (kicksecure-delete name lst)
"Return a newly-created copy of LST with elements or pairs whose
keys `string-prefix?' with NAME removed.
For example:
(kicksecure-delete \"loglevel\"
'(\"quiet\" \"loglevel=0\" \"loglevel=1\"))
=> (\"quiet\")
(kicksecure-delete \"net.ipv6.conf\"
'((\"net.ipv6.conf.all.accept_ra\" . \"0\")
(\"net.ipv6.conf.default.accept_ra\" . \"0\")))
=> ()"
(filter (lambda (item)
(not (cond
((pair? item) (string-prefix? name (car item)))
(else (string-prefix? name item)))))
lst))
;; Source: <https://github.com/Kicksecure/security-misc>
;; Extracted with the following command:
;; cat etc/default/grub.d/* | \
;; sed -E \
;; -e 's@GRUB_CMDLINE_LINUX(_DEFAULT)?=".GRUB_CMDLINE_LINUX(_DEFAULT)? @"@g' \
;; -e 's@(=(on|off|force|1|0)|quiet) @\1" "@g' \
;; -e 's@(.*dpkg.*|.*GRUB_CMDLINE.*)@#\1@g' \
;; -e 's@^#+@;;@g'
(define %kicksecure-kernel-arguments
'(;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Enables all known mitigations for CPU vulnerabilities.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/index.html
;; https://forums.whonix.org/t/should-all-kernel-patches-for-cpu-bugs-be-unconditionally-enabled-vs-performance-vs-applicability/7647
;; Enable mitigations for Spectre variant 2 (indirect branch speculation).
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/spectre.html
"spectre_v2=on"
;; Disable Speculative Store Bypass.
"spec_store_bypass_disable=on"
;; Enable mitigations for the L1TF vulnerability through disabling SMT
;; and L1D flush runtime control.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html
"l1tf=full,force"
;; Enable mitigations for the MDS vulnerability through clearing buffer cache
;; and disabling SMT.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html
"mds=full,nosmt"
;; Patches the TAA vulnerability by disabling TSX and enables mitigations using
;; TSX Async Abort along with disabling SMT.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html
"tsx=off" "tsx_async_abort=full,nosmt"
;; Mark all huge pages in the EPT as non-executable to mitigate iTLB multihit.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/multihit.html
"kvm.nx_huge_pages=force"
;; Enables mitigations for SRBDS to prevent MDS attacks on RDRAND and RDSEED instructions.
;; Only mitigated through microcode updates from Intel.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/special-register-buffer-data-sampling.html
;; https://access.redhat.com/solutions/5142691
;; Force disable SMT as it has caused numerous CPU vulnerabilities.
;; The only full mitigation of cross-HT attacks is to disable SMT.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/core-scheduling.html
;; https://forums.whonix.org/t/should-all-kernel-patches-for-cpu-bugs-be-unconditionally-enabled-vs-performance-vs-applicability/7647/17
"nosmt=force"
;; Enables the prctl interface to prevent leaks from L1D on context switches.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1d_flush.html
"l1d_flush=on"
;; Mitigates numerous MMIO Stale Data vulnerabilities and disables SMT.
;;
;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html
"mmio_stale_data=full,nosmt"
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Distrusts the bootloader for initial entropy at boot.
;;
;; https://lkml.org/lkml/2022/6/5/271
"random.trust_bootloader=off"
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; 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
;; https://archive.nytimes.com/www.nytimes.com/interactive/2013/09/05/us/documents-reveal-nsa-campaign-against-encryption.html
;; https://forums.whonix.org/t/entropy-config-random-trust-cpu-yes-or-no-rng-core-default-quality/8566
;; https://lkml.org/lkml/2022/6/5/271
"random.trust_cpu=off"
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Enables IOMMU to prevent DMA attacks.
"intel_iommu=on" "amd_iommu=force_isolation"
;; Disable the busmaster bit on all PCI bridges during very
;; early boot to avoid holes in IOMMU.
;;
;; https://mjg59.dreamwidth.org/54433.html
;; https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4444f8541dad16fefd9b8807ad1451e806ef1d94
"efi=disable_early_pci_dma"
;; Enables strict enforcement of IOMMU TLB invalidation so devices will never be able to access stale data contents
;; https://github.com/torvalds/linux/blob/master/drivers/iommu/Kconfig#L97
;; Page 11 of https://lenovopress.lenovo.com/lp1467.pdf
"iommu=force" "iommu.passthrough=0" "iommu.strict=1"
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;;kpkg="linux-image-$(dpkg --print-architecture)" || true
;;kver="$(dpkg-query --show --showformat='${Version}' "$kpkg")" 2>/dev/null || true
;;echo "## kver: $kver"
;; Disables the merging of slabs of similar sizes.
;; Sometimes a slab can be used in a vulnerable way which an attacker can exploit.
"slab_nomerge"
;; Enables sanity checks (F) and redzoning (Z).
;; Disabled due to kernel deciding to implicitly disable kernel pointer hashing
;; https://github.com/torvalds/linux/commit/792702911f581f7793962fbeb99d5c3a1b28f4c3
;;"slub_debug=FZ"
;; Zero memory at allocation and free time.
"init_on_alloc=1" "init_on_free=1"
;; Machine check exception handler decides whether the system should panic or not based on the exception that happened.
;; https://forums.whonix.org/t/kernel-hardening/7296/494
;;"mce=0"
;; Enables Kernel Page Table Isolation which mitigates Meltdown and improves KASLR.
"pti=on"
;; Vsyscalls are obsolete, are at fixed addresses and are a target for ROP.
"vsyscall=none"
;; Enables page allocator freelist randomization.
"page_alloc.shuffle=1"
;; Enables randomisation of the kernel stack offset on syscall entries (introduced in kernel 5.13).
;; https://lkml.org/lkml/2019/3/18/246
"randomize_kstack_offset=on"
;; Enables kernel lockdown.
;;
;; Disabled for now as it enforces module signature verification which breaks
;; too many things.
;; https://forums.whonix.org/t/enforce-kernel-module-software-signature-verification-module-signing-disallow-kernel-module-loading-by-default/7880
;;
;;if dpkg --compare-versions "${kver}" ge "5.4"; then
;; "lockdown=confidentiality"
;;fi
;; Gather more entropy during boot.
;;
;; Requires linux-hardened kernel patch.
;; https://github.com/anthraxx/linux-hardened
"extra_latent_entropy"
;; Restrict access to debugfs since it can contain a lot of sensitive information.
;; https://lkml.org/lkml/2020/7/16/122
;; https://github.com/torvalds/linux/blob/fb1201aececc59990b75ef59fca93ae4aa1e1444/Documentation/admin-guide/kernel-parameters.txt#L835-L848
"debugfs=off"
;; Force the kernel to panic on "oopses" (which may be due to false positives)
;; https://forums.whonix.org/t/set-oops-panic-kernel-parameter-or-kernel-panic-on-oops-1-sysctl-for-better-security/7713
;; Implemented differently:
;; /usr/libexec/security-misc/panic-on-oops
;; /etc/profile.d/security-misc.sh
;; /etc/sudoers.d/security-misc
;;"oops=panic"
;; Requires every module to be signed before being loaded.
;; Any module that is unsigned or signed with an invalid key cannot be loaded.
;; This makes it harder to load a malicious module.
;;
;; Not enabled by default yet due to issues:
;; https://forums.whonix.org/t/enforce-kernel-module-software-signature-verification-module-signing-disallow-kernel-module-loading-by-default/7880/61
;; https://github.com/dell/dkms/issues/359
;;"module.sig_enforce=1"
;; Copyright (C) 2023 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; https://www.kicksecure.com/wiki/Security-misc#Remount_Secure
;; Disable Remount Secure.
;;"remountsecure=0"
;; Re-mount with nodev, nosuid only.
;;"remountsecure=1"
;; Re-mount with nodev, nosuid and most with noexec except for /home.
;;"remountsecure=2"
;; Re-mount with nodev, nosuid and all with noexec including /home.
;;"remountsecure=3"
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Prevent kernel info leaks in console during boot.
;; https://phabricator.whonix.org/T950
;; LANG=C str_replace is provided by package helper-scripts.
;; The following command actually removed "quiet" from the kernel command line.
;; If verbosity is desired, the user might want to keep this line.
;; Remove "quiet" from GRUB_CMDLINE_LINUX_DEFAULT because "quiet" must be first.
;;GRUB_CMDLINE_LINUX_DEFAULT="$(echo "$GRUB_CMDLINE_LINUX_DEFAULT" | LANG=C str_replace "quiet" "")"
;; If verbosity is desired, the user might want to out-comment the following line.
"quiet" "loglevel=0"
;; NOTE:
;; After editing this file, running:
;; sudo update-grub
;; is required.
;;
;; If higher verbosity is desired, the user might also want to delete file
;; /etc/sysctl.d/30_silent-kernel-printk.conf
;; (or out-comment its settings).
;;
;; Alternatively, the user could consider to install the debug-misc package,
;; which will undo the settings found here.
))
;; Source <https://github.com/Kicksecure/security-misc>>
;; Extracted with the following command:
;; cat usr/lib/sysctl.d/* | \
;; sed -E \
;; -e 's@^([0-9a-z_\.]*) ?= ?(.*)@("\1" . "\2")@g' \
;; -e 's@\|/bin@\|/run/current-system/profile/bin@g' \
;; -e 's@^#+@;;@g'
(define %kicksecure-sysctl-rules
'(;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Quote https://www.kernel.org/doc/html/latest/admin-guide/sysctl/kernel.html
;;
;; kexec_load_disabled:
;;
;; A toggle indicating if the kexec_load syscall has been disabled. This value defaults to 0 (false: kexec_load enabled), but can be set to 1 (true: kexec_load disabled). Once true, kexec can no longer be used, and the toggle cannot be set back to false. This allows a kexec image to be loaded before disabling the syscall, allowing a system to set up (and later use) an image without it being altered. Generally used together with the "modules_disabled" sysctl.
;; Disables kexec which can be used to replace the running kernel.
("kernel.kexec_load_disabled" . "1")
;; Why is this in a dedicated config file?
;; Package ram-wipe requires kexec. However, ram-wipe could not ship a config
;; file /etc/sysctl.d/40_ram-wipe.conf which sets 'kernel.kexec_load_disabled=0'.
;; This is because once systemd-sysctl.service has set 'kernel.kexec_load_disabled=1'
;; it cannot be undone without reboot. This is a upstream Linux security feature.
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; Prevent kernel info leaks in console during boot.
;; https://phabricator.whonix.org/T950
("kernel.printk" . "3 3 3 3")
;; NOTE:
;; For higher verbosity, the user might also want to delete file
;; /etc/default/grub.d/41_quiet.cfg
;; (or out-comment its settings).
;;
;; Alternatively, the user could consider to install the debug-misc package,
;; which will undo the settings found here.
;; Copyright (C) 2019 - 2023 ENCRYPTED SUPPORT LP <adrelanos@whonix.org>
;; See the file COPYING for copying conditions.
;; NOTE:
;; This file has a weird file name so /usr/lib/sysctl.d/99-protect-links.conf
;; is parsed first and /usr/lib/sysctl.d/990-security-misc.conf is parsed
;; afterwards. See also:
;; https://github.com/Kicksecure/security-misc/pull/135
;; Restricts the kernel log to root only.
("kernel.dmesg_restrict" . "1")
;; Disables coredumps. This setting may be overwritten by systemd so this may not be useful.
;; security-misc also disables coredumps in other ways.
("kernel.core_pattern" . "|/run/current-system/profile/bin/false")
;; Does not set coredump name to 'core' which is default. Defense in depth.
("kernel.core_uses_pid" . "1")
;; Prevent setuid processes from creating coredumps.
("fs.suid_dumpable" . "0")
;; Don't allow writes to files that we don't own
;; in world writable sticky directories, unless
;; they are owned by the owner of the directory.
("fs.protected_fifos" . "2")
("fs.protected_regular" . "2")
;; Only allow symlinks to be followed when outside of
;; a world-writable sticky directory, or when the owner
;; of the symlink and follower match, or when the directory
;; owner matches the symlink's owner.
;;
;; Prevent hardlinks from being created by users that do not
;; have read/write access to the source file.
;;
;; These prevent many TOCTOU races.
("fs.protected_symlinks" . "1")
("fs.protected_hardlinks" . "1")
;; Hides kernel addresses in various files in /proc.
;; Kernel addresses can be very useful in certain exploits.
;;
;; https://kernsec.org/wiki/index.php/Bug_Classes/Kernel_pointer_leak
("kernel.kptr_restrict" . "2")
;; Improves ASLR effectiveness for mmap.
;; Both explicit sysctl are made redundant due to automation
;; https://forums.whonix.org/t/automate-mmap-randomisation-to-fix-ppc64el/16514
;; Do NOT enable either - displaying only for clarity
;;
;;vm.mmap_rnd_bits=32
;;vm.mmap_rnd_compat_bits=16
;; Restricts the use of ptrace to root. This might break some programs running under WINE.
;; A workaround for WINE would be to give the wineserver and wine-preloader ptrace capabilities. This can be done by running:
;;
;; sudo apt-get install libcap2-bin
;; sudo setcap cap_sys_ptrace=eip /usr/bin/wineserver
;; sudo setcap cap_sys_ptrace=eip /usr/bin/wine-preloader
("kernel.yama.ptrace_scope" . "2")
;; Randomize the addresses for mmap base, heap, stack, and VDSO pages
("kernel.randomize_va_space" . "2")
;; Hardens the BPF JIT compiler and restricts it to root.
("kernel.unprivileged_bpf_disabled" . "1")
("net.core.bpf_jit_harden" . "2")
;; meta start
;; project Kicksecure
;; category networking and security
;; description
;; TCP/IP stack hardening
;; A martian packet is a one with a source address which is blatantly wrong
;; Recommended to keep a log of these to identify these suspicious packets
("net.ipv4.conf.all.log_martians" . "1")
("net.ipv4.conf.default.log_martians" . "1")
;; Protects against time-wait assassination.
;; It drops RST packets for sockets in the time-wait state.
("net.ipv4.tcp_rfc1337" . "1")
;; Disables ICMP redirect acceptance.
("net.ipv4.conf.all.accept_redirects" . "0")
("net.ipv4.conf.default.accept_redirects" . "0")
("net.ipv4.conf.all.secure_redirects" . "0")
("net.ipv4.conf.default.secure_redirects" . "0")
("net.ipv6.conf.all.accept_redirects" . "0")
("net.ipv6.conf.default.accept_redirects" . "0")
;; Disables ICMP redirect sending.
("net.ipv4.conf.all.send_redirects" . "0")
("net.ipv4.conf.default.send_redirects" . "0")
;; Ignores ICMP requests.
("net.ipv4.icmp_echo_ignore_all" . "1")
("net.ipv6.icmp.echo_ignore_all" . "1")
;; Ignores bogus ICMP error responses
("net.ipv4.icmp_ignore_bogus_error_responses" . "1")
;; Enables TCP syncookies.
("net.ipv4.tcp_syncookies" . "1")
;; Disable source routing.
("net.ipv4.conf.all.accept_source_route" . "0")
("net.ipv4.conf.default.accept_source_route" . "0")
("net.ipv6.conf.all.accept_source_route" . "0")
("net.ipv6.conf.default.accept_source_route" . "0")
;; Enable reverse path filtering to prevent IP spoofing and
;; mitigate vulnerabilities such as CVE-2019-14899.
;; https://forums.whonix.org/t/enable-reverse-path-filtering/8594
("net.ipv4.conf.default.rp_filter" . "1")
("net.ipv4.conf.all.rp_filter" . "1")
;; meta end
;; Previously disabled SACK, DSACK, and FACK.
;; https://forums.whonix.org/t/disabling-tcp-sack-dsack-fack/8109
;;net.ipv4.tcp_sack=0
;;net.ipv4.tcp_dsack=0
;;net.ipv4.tcp_fack=0
;; meta start
;; project Kicksecure
;; category networking and security
;; description
;; disable IPv4 TCP Timestamps
("net.ipv4.tcp_timestamps" . "0")
;; meta end
;; Disable SysRq key
("kernel.sysrq" . "0")
;; Restrict loading TTY line disciplines to CAP_SYS_MODULE to prevent
;; unprivileged attackers from loading vulnerable line disciplines
;; with the TIOCSETD ioctl which has been used in exploits before
;; such as https://a13xp0p0v.github.io/2017/03/24/CVE-2017-2636.html
;;
;; https://lkml.org/lkml/2019/4/15/890
("dev.tty.ldisc_autoload" . "0")
;; Restrict the userfaultfd() syscall to root as it can make heap sprays
;; easier.
;;
;; https://duasynt.com/blog/linux-kernel-heap-spray
("vm.unprivileged_userfaultfd" . "0")
;; Let the kernel only swap if it is absolutely necessary.
;; Better not be set to zero:
;; - https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-tunables.html
;; - https://en.wikipedia.org/wiki/Swappiness
("vm.swappiness" . "1")
;; Disallow kernel profiling by users without CAP_SYS_ADMIN
;; https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
("kernel.perf_event_paranoid" . "3")
;; Do not accept router advertisements
("net.ipv6.conf.all.accept_ra" . "0")
("net.ipv6.conf.default.accept_ra" . "0")))

26
operating-systems/buer.scm
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@ -57,6 +57,12 @@
#|S|# #:use-module ((buer files substitute-keys) #:prefix public-key:)
#|T|# #:use-module ((buer files thinkfan) #:prefix file:thinkfan-)
#|Kicksecure configurations|#
#|K|# #:use-module (radix modules kicksecure-configs)
#|SRFI's|#
#:use-module (srfi srfi-1)
#:export (operating-system))
(define operating-system
@ -83,10 +89,10 @@
(kernel linux-libre-6.7)
(kernel-arguments
`("modprobe.blacklist=usbmouse,usbkbd,pcspkr"
"thinkpad_acpi.fan_control=1"
"loglevel=5"
"quiet"))
(cons* "modprobe.blacklist=usbmouse,usbkbd,pcspkr"
"thinkpad_acpi.fan_control=1"
(kicksecure-delete %kicksecure-kernel-arguments
"debugfs")))
(file-systems
(cons* (file-system
@ -317,13 +323,21 @@
`(("/bin/sh" ,(file-append dash-next "/bin/dash"))
("/usr/bin/env" ,(file-append coreutils "/bin/env"))))
(simple-service 'extra-sysctl-settings sysctl-service-type
`(("vm.swappiness" . "180")
("vm.watermark_boost_factor" . "0")
("vm.watermark_scale_factor" . "125")
("vm.page-cluster" . "0")))
#|Miscellaneous services|#
(service urandom-seed-service-type)
(service nscd-service-type)
(service sysctl-service-type
(sysctl-configuration
(sysctl (file-append procps "/sbin/sysctl"))
(settings `(("fs.protected_hardlinks" . "1")
("fs.protected_symlinks" . "1")))))))))
(settings (fold kicksecure-delete
%kicksecure-sysctl-rules
'("net.core.bpf_jit_harden"
"kernel.unprivileged_bpf_disabled")))))))))
operating-system