84fb8820db
Introduces the option security.protectKernelImage that is intended to control various mitigations to protect the integrity of the running kernel image (i.e., prevent replacing it without rebooting). This makes sense as a dedicated module as it is otherwise somewhat difficult to override for hardened profile users who want e.g., hibernation to work.
57 lines
1.8 KiB
Nix
57 lines
1.8 KiB
Nix
{ config, lib, ... }:
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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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options = {
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security.allowUserNamespaces = mkOption {
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type = types.bool;
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default = true;
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description = ''
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Whether to allow creation of user namespaces. A recurring problem
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with user namespaces is the presence of code paths where the kernel's
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permission checking logic fails to account for namespacing, instead
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permitting a namespaced process to act outside the namespace with the
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same privileges as it would have inside it. This is particularly
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damaging in the common case of running as root within the namespace.
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When user namespace creation is disallowed, attempting to create
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a user namespace fails with "no space left on device" (ENOSPC).
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'';
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};
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security.protectKernelImage = mkOption {
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type = types.bool;
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default = false;
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description = ''
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Whether to prevent replacing the running kernel image.
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'';
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};
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};
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config = mkMerge [
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(mkIf (!config.security.allowUserNamespaces) {
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# Setting the number of allowed user namespaces to 0 effectively disables
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# the feature at runtime. Note that root may raise the limit again
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# at any time.
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boot.kernel.sysctl."user.max_user_namespaces" = 0;
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assertions = [
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{ assertion = config.nix.useSandbox -> config.security.allowUserNamespaces;
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message = "`nix.useSandbox = true` conflicts with `!security.allowUserNamespaces`.";
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}
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];
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})
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(mkIf config.security.protectKernelImage {
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# Disable hibernation (allows replacing the running kernel)
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boot.kernelParams = [ "nohibernate" ];
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# Prevent replacing the running kernel image w/o reboot
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boot.kernel.sysctl."kernel.kexec_load_disabled" = mkDefault true;
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})
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];
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}
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