refactor: inputs/ --> {sys,home}/
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225 changed files with 77 additions and 88 deletions
195
sys/modules/base/security/kernel.nix
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195
sys/modules/base/security/kernel.nix
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{ lib, config, ... }:
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let
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inherit (lib) optionals mkForce concatLists;
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inherit (builtins) elem;
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features = config.systemModules.host.hardware.features;
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in
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{
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security = {
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# Protects the kernel from being tampered with at runtime. prevents the ability to hibernate.
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protectKernelImage = true;
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# page table isolation (PTI) is a kernel option designed to protect against
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# side-channel attacks, including Meltdown & Spectre vunerabilities.
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forcePageTableIsolation = true;
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# locking kernel modules during runtime breaks certain services by stopping them from being
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# loaded at runtime. we use some of these services, so we disable this kernel option.
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lockKernelModules = false;
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# we enable simultaneous multithreading (SMT) because while it increases our attack surface
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# disabling it comes at a large perfomance loss.
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allowSimultaneousMultithreading = true;
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# slight increase in attack surface, but allows for sandboxing
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allowUserNamespaces = true;
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# we don't need unpivileged user namespaces unless we are messing with containers so we disable
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unprivilegedUsernsClone = false;
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};
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boot = {
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kernel = {
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sysctl = {
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# obfuscate kernel pointers to protect against attacks that rely on memory layout of the kernel
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"kernel.kptr_restrict" = 2;
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# we don't make use of sysrq so we disable it to protect ourselves against potential physical attacks
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"kernel.sysrq" = mkForce 0;
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# limits the exposer of the kernel memory address via dmesg
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"kernel.dmesg_restrict" = 1;
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# we are not a kernel developer so we disable this to prevent potential information leaks & attacks
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"kernel.ftrace_enabled" = false;
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# disables performance events for all non-root users, root can only acess events that are explicitly
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# enabled.
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"kernel.perf_event_paranoid" = 3;
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# disables the use of berkeley packet filter (BPF) to unpriviliged users.
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"kernel.unprivileged_bpf_disabled" = 1;
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# prevents potentially leaking sensitive information from the boot console kernel log.
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"kernel.printk" = "3 3 3 3";
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# just-in-time (JIT) compiler for the berkeley packet filter (BPF). disable this as we dont make use
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# of it and reduces potential security risks.
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"net.core.bpf_jit_enable" = false;
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# disables core dumps for SUID and SGID this reduces the risk of exposing sensitive information
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# that might reside in the memory at the time of a crash
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"fs.suid_dumpable" = 0;
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# enforces strict access to files only allows the user or root to write regular files
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"fs.protected_regular" = 2;
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"fs.protected_fifos" = 2;
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# disables the automatic loading of TTY line disciplines
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"dev.tty.ldisc_autoload" = "0";
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};
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};
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# https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html
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kernelParams = [
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# kernel errors can trigger something known as an "oops", by settings oops=panic we add a fail-safe
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# mechanism to ensure that in the advent of an oops the system reboots, preventing the system from running
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# in a potentially compromised state.
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"oops=panic"
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# enforces signature checking on all kernel modules before they are loaded.
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"module.sig_enforce=1"
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# enables memory page poisoning, increasing the difficulty for attackers to exploit
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# use-after-free vulnerabillities.
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"page_poison=on"
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# enables kernel adress space layout randomization (KASLR) which mitigates memory exploits
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# & increases system entropy.
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"page_alloc.shuffle=1"
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# randomizes the kernel stack offset, mitigating stack-based attacks.
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"randomize_kstack_offset=on"
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# lockdown aims to restrict certain kernel functionality that could be exploited by an attacker with
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# user space code.
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"lockdown=confidentiality"
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# disables a common interface that contains sensitive info on the kernel
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"debugfs=off"
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# prevent kernel from blanking plymouth out of the frame buffer console
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"fbcon=nodefer"
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# enables auditing of integrity measurement events
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"integrity_audit=1"
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# increases memory safety by modifying the state of the memory objects more closely & helps detecting
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# & identifying bugs
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"slub_debug=FZP"
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# disables the legacy vyscall mechanism, reducing attack surface.
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"vsyscall=none"
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# reduce exposure to heap attacks by preventing different slab caches from being merged.
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"slab_nomerge"
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"rootflags=noatime"
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"lsm=landlock,lockdown,yama,integrity,apparmor,bpf,tomoyo,selinux"
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];
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blacklistedKernelModules = concatLists [
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# Obscure network protocols
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[
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"dccp" # Datagram Congestion Control Protocol
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"sctp" # Stream Control Transmission Protocol
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"rds" # Reliable Datagram Sockets
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"tipc" # Transparent Inter-Process Communication
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"n-hdlc" # High-level Data Link Control
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"netrom" # NetRom
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"x25" # X.25
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"ax25" # Amatuer X.25
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"rose" # ROSE
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"decnet" # DECnet
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"econet" # Econet
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"af_802154" # IEEE 802.15.4
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"ipx" # Internetwork Packet Exchange
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"appletalk" # Appletalk
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"psnap" # SubnetworkAccess Protocol
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"p8022" # IEEE 802.3
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"p8023" # Novell raw IEEE 802.3
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"can" # Controller Area Network
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"atm" # ATM
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]
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# Old or rare or insufficiently audited filesystems
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[
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"adfs" # Active Directory Federation Services
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"affs" # Amiga Fast File System
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"befs" # "Be File System"
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"bfs" # BFS, used by SCO UnixWare OS for the /stand slice
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"cifs" # Common Internet File System
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"cramfs" # compressed ROM/RAM file system
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"efs" # Extent File System
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"erofs" # Enhanced Read-Only File System
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"exofs" # EXtended Object File System
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"freevxfs" # Veritas filesystem driver
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"f2fs" # Flash-Friendly File System
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"vivid" # Virtual Video Test Driver (unnecessary, and a historical cause of escalation issues)
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"gfs2" # Global File System 2
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"hpfs" # High Performance File System (used by OS/2)
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"hfs" # Hierarchical File System (Macintosh)
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"hfsplus" # " same as above, but with extended attributes
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"jffs2" # Journalling Flash File System (v2)
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"jfs" # Journaled File System - only useful for VMWare sessions
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"ksmbd" # SMB3 Kernel Server
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"minix" # minix fs - used by the minix OS
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"nfsv3" # " (v3)
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"nfsv4" # Network File System (v4)
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"nfs" # Network File System
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"nilfs2" # New Implementation of a Log-structured File System
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"omfs" # Optimized MPEG Filesystem
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"qnx4" # extent-based file system used by the QNX4 and QNX6 OSes
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"qnx6" # "
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"squashfs" # compressed read-only file system (used by live CDs)
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"sysv" # implements all of Xenix FS, SystemV/386 FS and Coherent FS.
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"udf" # https://docs.kernel.org/5.15/filesystems/udf.html
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]
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# Disable Thunderbolt and FireWire to prevent DMA attacks
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[
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"thunderbolt"
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"firewire-core"
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]
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# if bluetooth is enabled, whitelist the module
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# necessary for bluetooth dongles to work
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(optionals (! (elem "bluetooth" features)) [
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"bluetooth" # let bluetooth work
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"btusb" # let bluetooth dongles work
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])
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];
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};
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}
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