Security: Difference between revisions

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These are security elements that are core features of using Nix(OS).

~~=== Obscurity of Nix store ===~~

In a vanilla NixOS system, the typical [https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard Linux filesystem hierarchy] is, in large part, replaced with the Nix store's [[User Environment|user environments]]. This means that some malware which might rely on finding system tools in particular places might fail. This is a form of [https://en.wikipedia.org/wiki/Security_through_obscurity security through obscurity] and is only a minor layer of protection.

=== Effort to isolate runtime search paths ===

In general, there is an effort to avoid [~~https~~:~~//en.wikipedia.org/wiki/~~Rpath rpath] collisions across users [https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b].

In general, there is an effort to avoid [[wikipedia:Rpath|rpath]] collisions across users [https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b].

=== Multi-user installation ===

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=== Data integrity and authenticity ===

The core installation resources for Nix(OS) have [~~https~~:~~//en.wikipedia.org/wiki/~~SHA-2 SHA256] checksums which are [~~https~~:~~//en.wikipedia.org/wiki/~~GNU_Privacy_Guard GPG] signed by the [https://nixos.org/download.html#nix-verify-installation Nix team] for authenticity. Within the installation data are all the SHA256 checksums for packages that were available within Nixpkgs at build time.

The core installation resources for Nix(OS) have [[wikipedia:SHA-2|SHA256]] checksums which are [[wikipedia:GNU_Privacy_Guard|GPG]] signed by the [https://nixos.org/download.html#nix-verify-installation Nix team] for authenticity. Within the installation data are all the SHA256 checksums for packages that were available within Nixpkgs at build time.

All packages which are pulled into your Nix system via Nixpkgs derivation builds are checked against SHA256 checksums which are already available on your local system (and should be traceable to the signed core Nix install materials).

=== Obscurity of Nix store ===

In a vanilla NixOS system, the typical [https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard Linux filesystem hierarchy] is, in large part, replaced with the Nix store's [[User Environment|user environments]]. This means that some malware which might rely on finding system tools in particular places might fail. This is a form of [https://en.wikipedia.org/wiki/Security_through_obscurity security through obscurity] and is only a minor layer of protection.

== Supported by Nix ==

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==== Flatpaks ====

[https://en.wikipedia.org/wiki/Flatpak Flatpak]'ed applications are [https://docs.flatpak.org/en/latest/sandbox-permissions.html sandboxed] and require explicit privilege declaration for most access outside their own path. NixOS includes [https://nixos.org/manual/nixos/unstable/index.html#module-services-flatpak support for Flatpak]. Note that, since Flatpak application dependencies are [https://stackoverflow.com/questions/26217488/what-is-vendoring bundled/vendored], this introduces ~~other security risks for the application~~ [https://blogs.gentoo.org/mgorny/2021/02/19/the-modern-packagers-security-nightmare/]. Also, most application flatpaks [https://flatkill.org/ do no not make meaningful use of the sandbox].

[https://en.wikipedia.org/wiki/Flatpak Flatpak]'ed applications are [https://docs.flatpak.org/en/latest/sandbox-permissions.html sandboxed] and require explicit privilege declaration for most access outside their own path. NixOS includes [https://nixos.org/manual/nixos/unstable/index.html#module-services-flatpak support for Flatpak]. Note that, since Flatpak application dependencies are [https://stackoverflow.com/questions/26217488/what-is-vendoring bundled/vendored], this introduces [https://blogs.gentoo.org/mgorny/2021/02/19/the-modern-packagers-security-nightmare/ other security risks] for the application . Also, most application flatpaks [https://flatkill.org/ do no not make meaningful use of the sandbox].

==== Linux Containers ====

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NixOS includes support for hosting virtual machines. The Nix store of the host machine is shared read-only with guest machines, making them lighter-weight in terms of storage use than typical VMs. Guest VMs are easily built from Nix configurations.

[https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/qemu-vm.nix qemu-vm.nix - Implementation of QEMU builds of NixOS machine configurations]

* [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/qemu-vm.nix qemu-vm.nix - Implementation of QEMU builds of NixOS machine configurations]

* [https://github.com/firecracker-microvm/firecracker Firecracker microVM] - packages [https://search.nixos.org/packages?channel=unstable&show=firecracker&from=0&size=30&sort=relevance&type=packages&query=firecracker available]

* [https://github.com/astro/microvm.nix microvm.nix] builds and runs NixOS on various hypervisors

===== Test machines =====

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* [https://archive.fosdem.org/2020/schedule/event/kernel_address_space_isolation/attachments/slides/3889/export/events/attachments/kernel_address_space_isolation/slides/3889/Address_Space_Isolation_in_the_Linux_Kernel.pdf 2020 IBM Presentation on Address Space Isolation in the Linux Kernel] - Containers within VMs are a norm for security in the cloud. Addressing ongoing work to improve isolation of containers and VMs.

* [https://googleprojectzero.blogspot.com/2021/06/an-epyc-escape-case-study-of-kvm.html An EPYC escape: Case-study of a KVM breakout] - Detailing first known non-userspace vulnerability enabling guest-to-host breakout.

==== Systemd Hardening ====

It is possible to increase the isolation of Systemd services by using hardening options. For example, adding <code>PrivateNetwork=yes</code> option in a Systemd unit removes access to the host network.

For more information, please see [[Systemd_Hardening]].

=== Networking ===

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=== Secure Boot ===

Development of [https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#Secure_Boot UEFI Secure Boot] support is [https://github.com/NixOS/nixpkgs/issues/42127 in flight]. ~~Looking potential for release~~ in ~~22.05~~.

Development of [https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#Secure_Boot UEFI Secure Boot] support is [https://github.com/NixOS/nixpkgs/issues/42127 in flight]. An experimental secure boot implementation is available in [https://github.com/nix-community/lanzaboote Lanzaboote]

=== SELinux ===

It is possible to use [https://en.wikipedia.org/wiki/Security-Enhanced_Linux Security-Enhanced Linux (SELinux)] in NixOS, but proper integration does not exist. This does not appear to have gotten much attention [https://github.com/NixOS/rfcs/pull/41 since 2019].

It is possible to use [https://en.wikipedia.org/wiki/Security-Enhanced_Linux Security-Enhanced Linux (SELinux)] in NixOS, but proper integration does not exist. This does not appear to have gotten much attention [https://github.com/NixOS/rfcs/pull/41 since 2019]. However, there has been revived work in 2025 but there's no telling when things will land in NixOS.

== Nix official references ==

@@ Line 6: / Line 6: @@
 These are security elements that are core features of using Nix(OS).
-=== Obscurity of Nix store ===
-In a vanilla NixOS system, the typical [https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard Linux filesystem hierarchy] is, in large part, replaced with the Nix store's [[User Environment|user environments]]. This means that some malware which might rely on finding system tools in particular places might fail. This is a form of [https://en.wikipedia.org/wiki/Security_through_obscurity security through obscurity] and is only a minor layer of protection.
 === Effort to isolate runtime search paths ===
-In general, there is an effort to avoid [https://en.wikipedia.org/wiki/Rpath rpath] collisions across users [https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b].
+In general, there is an effort to avoid [[wikipedia:Rpath|rpath]] collisions across users [https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b].
 === Multi-user installation ===
@@ Line 21: / Line 17: @@
 === Data integrity and authenticity ===
-The core installation resources for Nix(OS) have [https://en.wikipedia.org/wiki/SHA-2 SHA256] checksums which are [https://en.wikipedia.org/wiki/GNU_Privacy_Guard GPG] signed by the [https://nixos.org/download.html#nix-verify-installation Nix team] for authenticity. Within the installation data are all the SHA256 checksums for packages that were available within Nixpkgs at build time.
+The core installation resources for Nix(OS) have [[wikipedia:SHA-2|SHA256]] checksums which are [[wikipedia:GNU_Privacy_Guard|GPG]] signed by the [https://nixos.org/download.html#nix-verify-installation Nix team] for authenticity. Within the installation data are all the SHA256 checksums for packages that were available within Nixpkgs at build time.
 All packages which are pulled into your Nix system via Nixpkgs derivation builds are checked against SHA256 checksums which are already available on your local system (and should be traceable to the signed core Nix install materials).
+=== Obscurity of Nix store ===
+In a vanilla NixOS system, the typical [https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard Linux filesystem hierarchy] is, in large part, replaced with the Nix store's [[User Environment|user environments]]. This means that some malware which might rely on finding system tools in particular places might fail. This is a form of [https://en.wikipedia.org/wiki/Security_through_obscurity security through obscurity] and is only a minor layer of protection.
 == Supported by Nix ==
@@ Line 46: / Line 46: @@
 ==== Flatpaks ====
-[https://en.wikipedia.org/wiki/Flatpak Flatpak]'ed applications are [https://docs.flatpak.org/en/latest/sandbox-permissions.html sandboxed] and require explicit privilege declaration for most access outside their own path. NixOS includes [https://nixos.org/manual/nixos/unstable/index.html#module-services-flatpak support for Flatpak]. Note that, since Flatpak application dependencies are [https://stackoverflow.com/questions/26217488/what-is-vendoring bundled/vendored], this introduces other security risks for the application [https://blogs.gentoo.org/mgorny/2021/02/19/the-modern-packagers-security-nightmare/]. Also, most application flatpaks [https://flatkill.org/ do no not make meaningful use of the sandbox].
+[https://en.wikipedia.org/wiki/Flatpak Flatpak]'ed applications are [https://docs.flatpak.org/en/latest/sandbox-permissions.html sandboxed] and require explicit privilege declaration for most access outside their own path. NixOS includes [https://nixos.org/manual/nixos/unstable/index.html#module-services-flatpak support for Flatpak]. Note that, since Flatpak application dependencies are [https://stackoverflow.com/questions/26217488/what-is-vendoring bundled/vendored], this introduces [https://blogs.gentoo.org/mgorny/2021/02/19/the-modern-packagers-security-nightmare/ other security risks] for the application . Also, most application flatpaks [https://flatkill.org/ do no not make meaningful use of the sandbox].
 ==== Linux Containers ====
@@ Line 71: / Line 71: @@
 NixOS includes support for hosting virtual machines. The Nix store of the host machine is shared read-only with guest machines, making them lighter-weight in terms of storage use than typical VMs. Guest VMs are easily built from Nix configurations.
-[https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/qemu-vm.nix qemu-vm.nix - Implementation of QEMU builds of NixOS machine configurations]
+* [https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/qemu-vm.nix qemu-vm.nix - Implementation of QEMU builds of NixOS machine configurations]
+* [https://github.com/firecracker-microvm/firecracker Firecracker microVM] - packages [https://search.nixos.org/packages?channel=unstable&show=firecracker&from=0&size=30&sort=relevance&type=packages&query=firecracker available]
+* [https://github.com/astro/microvm.nix microvm.nix] builds and runs NixOS on various hypervisors
 ===== Test machines =====
@@ Line 84: / Line 86: @@
 * [https://archive.fosdem.org/2020/schedule/event/kernel_address_space_isolation/attachments/slides/3889/export/events/attachments/kernel_address_space_isolation/slides/3889/Address_Space_Isolation_in_the_Linux_Kernel.pdf 2020 IBM Presentation on Address Space Isolation in the Linux Kernel] - Containers within VMs are a norm for security in the cloud. Addressing ongoing work to improve isolation of containers and VMs.
 * [https://googleprojectzero.blogspot.com/2021/06/an-epyc-escape-case-study-of-kvm.html An EPYC escape: Case-study of a KVM breakout] - Detailing first known non-userspace vulnerability enabling guest-to-host breakout.
+==== Systemd Hardening ====
+It is possible to increase the isolation of Systemd services by using hardening options. For example, adding <code>PrivateNetwork=yes</code> option in a Systemd unit removes access to the host network.
+For more information, please see [[Systemd_Hardening]].
 === Networking ===
@@ Line 102: / Line 110: @@
 === Secure Boot ===
-Development of [https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#Secure_Boot UEFI Secure Boot] support is [https://github.com/NixOS/nixpkgs/issues/42127 in flight]. Looking potential for release in 22.05.
+Development of [https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface#Secure_Boot UEFI Secure Boot] support is [https://github.com/NixOS/nixpkgs/issues/42127 in flight]. An experimental secure boot implementation is available in [https://github.com/nix-community/lanzaboote Lanzaboote]
 === SELinux ===
-It is possible to use [https://en.wikipedia.org/wiki/Security-Enhanced_Linux Security-Enhanced Linux (SELinux)] in NixOS, but proper integration does not exist. This does not appear to have gotten much attention [https://github.com/NixOS/rfcs/pull/41 since 2019].
+It is possible to use [https://en.wikipedia.org/wiki/Security-Enhanced_Linux Security-Enhanced Linux (SELinux)] in NixOS, but proper integration does not exist. This does not appear to have gotten much attention [https://github.com/NixOS/rfcs/pull/41 since 2019]. However, there has been revived work in 2025 but there's no telling when things will land in NixOS.
 == Nix official references ==