kicksecure.scm

;; Contents extracted from Kicksecure's resources.

(define-module (testament kicksecure)
  #: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://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html
    ;; https://forums.whonix.org/t/should-all-kernel-patches-for-cpu-bugs-be-unconditionally-enabled-vs-performance-vs-applicability/7647

    ;; Enable known mitigations for CPU vulnerabilities and disable SMT.
    "mitigations=auto,nosmt"

    ;; 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"

    ;; Enable mitigations for RETBleed (Arbitrary Speculative Code Execution with
    ;; Return Instructions) vulnerability and disable SMT.
    ;;
    "retbleed=auto,nosmt"

    ;; Control RAS overflow mitigation on AMD Zen CPUs.
    ;; The current default kernel parameter is 'spec_rstack_overflow=safe-ret'
    ;; This default will used until provided sufficient evidence to modify.
    ;;
    ;; https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/srso.html

    ;; 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")

    ;; Disable asynchronous I/O for all processes.
    ;; Valid only for linux kernel version >= 6.6.
    ;; Command is retained here for future-proofing and completeness.
    ;; https://forums.whonix.org/t/io-uring-security-vulnerabilties/16890/6
    ("kernel.io_uring_disabled" . "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")
    ))