a8989b353a
As discussed in https://github.com/NixOS/nixpkgs/pull/73763, prevailing
consensus is to revert that commit. People use the hardened profile on
machines and run nix builds, and there's no good reason to use
unsandboxed builds at all unless you're in a platform that doesn't
support them.
This reverts commit 00ac71ab19.
146 lines
4.8 KiB
Nix
146 lines
4.8 KiB
Nix
# A profile with most (vanilla) hardening options enabled by default,
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# potentially at the cost of features and performance.
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{ lib, pkgs, ... }:
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with lib;
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{
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meta = {
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maintainers = [ maintainers.joachifm ];
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};
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boot.kernelPackages = mkDefault pkgs.linuxPackages_hardened;
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nix.allowedUsers = mkDefault [ "@users" ];
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environment.memoryAllocator.provider = mkDefault "scudo";
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environment.variables.SCUDO_OPTIONS = mkDefault "ZeroContents=1";
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security.hideProcessInformation = mkDefault true;
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security.lockKernelModules = mkDefault true;
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security.allowUserNamespaces = mkDefault false;
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security.protectKernelImage = mkDefault true;
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security.allowSimultaneousMultithreading = mkDefault false;
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security.forcePageTableIsolation = mkDefault true;
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security.virtualisation.flushL1DataCache = mkDefault "always";
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security.apparmor.enable = mkDefault true;
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boot.kernelParams = [
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# Slab/slub sanity checks, redzoning, and poisoning
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"slub_debug=FZP"
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# Disable slab merging to make certain heap overflow attacks harder
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"slab_nomerge"
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# Overwrite free'd memory
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"page_poison=1"
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# Disable legacy virtual syscalls
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"vsyscall=none"
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# Enable page allocator randomization
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"page_alloc.shuffle=1"
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];
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boot.blacklistedKernelModules = [
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# Obscure network protocols
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"ax25"
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"netrom"
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"rose"
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# Old or rare or insufficiently audited filesystems
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"adfs"
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"affs"
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"bfs"
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"befs"
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"cramfs"
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"efs"
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"erofs"
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"exofs"
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"freevxfs"
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"f2fs"
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"hfs"
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"hpfs"
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"jfs"
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"minix"
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"nilfs2"
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"qnx4"
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"qnx6"
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"sysv"
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"ufs"
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];
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# Restrict ptrace() usage to processes with a pre-defined relationship
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# (e.g., parent/child)
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boot.kernel.sysctl."kernel.yama.ptrace_scope" = mkOverride 500 1;
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# Restrict access to kernel ring buffer (information leaks)
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boot.kernel.sysctl."kernel.dmesg_restrict" = mkDefault true;
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# Hide kptrs even for processes with CAP_SYSLOG
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boot.kernel.sysctl."kernel.kptr_restrict" = mkOverride 500 2;
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# Unprivileged access to bpf() has been used for privilege escalation in
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# the past
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boot.kernel.sysctl."kernel.unprivileged_bpf_disabled" = mkDefault true;
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# Disable bpf() JIT (to eliminate spray attacks)
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boot.kernel.sysctl."net.core.bpf_jit_enable" = mkDefault false;
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# ... or at least apply some hardening to it
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boot.kernel.sysctl."net.core.bpf_jit_harden" = mkDefault true;
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# Raise ASLR entropy for 64bit & 32bit, respectively.
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#
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# Note: mmap_rnd_compat_bits may not exist on 64bit.
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boot.kernel.sysctl."vm.mmap_rnd_bits" = mkDefault 32;
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boot.kernel.sysctl."vm.mmap_rnd_compat_bits" = mkDefault 16;
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# Allowing users to mmap() memory starting at virtual address 0 can turn a
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# NULL dereference bug in the kernel into code execution with elevated
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# privilege. Mitigate by enforcing a minimum base addr beyond the NULL memory
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# space. This breaks applications that require mapping the 0 page, such as
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# dosemu or running 16bit applications under wine. It also breaks older
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# versions of qemu.
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#
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# The value is taken from the KSPP recommendations (Debian uses 4096).
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boot.kernel.sysctl."vm.mmap_min_addr" = mkDefault 65536;
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# Disable ftrace debugging
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boot.kernel.sysctl."kernel.ftrace_enabled" = mkDefault false;
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# Enable strict reverse path filtering (that is, do not attempt to route
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# packets that "obviously" do not belong to the iface's network; dropped
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# packets are logged as martians).
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boot.kernel.sysctl."net.ipv4.conf.all.log_martians" = mkDefault true;
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boot.kernel.sysctl."net.ipv4.conf.all.rp_filter" = mkDefault "1";
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boot.kernel.sysctl."net.ipv4.conf.default.log_martians" = mkDefault true;
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boot.kernel.sysctl."net.ipv4.conf.default.rp_filter" = mkDefault "1";
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# Ignore broadcast ICMP (mitigate SMURF)
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boot.kernel.sysctl."net.ipv4.icmp_echo_ignore_broadcasts" = mkDefault true;
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# Ignore incoming ICMP redirects (note: default is needed to ensure that the
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# setting is applied to interfaces added after the sysctls are set)
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boot.kernel.sysctl."net.ipv4.conf.all.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.all.secure_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.secure_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv6.conf.all.accept_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv6.conf.default.accept_redirects" = mkDefault false;
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# Ignore outgoing ICMP redirects (this is ipv4 only)
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boot.kernel.sysctl."net.ipv4.conf.all.send_redirects" = mkDefault false;
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boot.kernel.sysctl."net.ipv4.conf.default.send_redirects" = mkDefault false;
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# Restrict userfaultfd syscalls to processes with the SYS_PTRACE capability
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boot.kernel.sysctl."vm.unprivileged_userfaultfd" = mkDefault false;
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}
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