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nixpkgs/nixos/modules/system/boot/binfmt.nix
polykernel 4a9d9928dc nixos/nix-daemon: use structural settings
The `nix.*` options, apart from options for setting up the
daemon itself, currently provide a lot of setting mappings
for the Nix daemon configuration. The scope of the mapping yields
convience, but the line where an option is considered essential
is blurry. For instance, the `extra-sandbox-paths` mapping is
provided without its primary consumer, and the corresponding
`sandbox-paths` option is also not mapped.

The current system increases the maintenance burden as maintainers have to
closely follow upstream changes. In this case, there are two state versions
of Nix which have to be maintained collectively, with different options
avaliable.

This commit aims to following the standard outlined in RFC 42[1] to
implement a structural setting pattern. The Nix configuration is encoded
at its core as key-value pairs which maps nicely to attribute sets, making
it feasible to express in the Nix language itself. Some existing options are
kept such as `buildMachines` and `registry` which present a simplified interface
to managing the respective settings. The interface is exposed as `nix.settings`.

Legacy configurations are mapped to their corresponding options under `nix.settings`
for backwards compatibility.

Various options settings in other nixos modules and relevant tests have been
updated to use structural setting for consistency.

The generation and validation of the configration file has been modified to
use `writeTextFile` instead of `runCommand` for clarity. Note that validation
is now mandatory as strict checking of options has been pushed down to the
derivation level due to freeformType consuming unmatched options. Furthermore,
validation can not occur when cross-compiling due to current limitations.

A new option `publicHostKey` was added to the `buildMachines`
submodule corresponding to the base64 encoded public host key settings
exposed in the builder syntax. The build machine generation was subsequently
rewritten to use `concatStringsSep` for better performance by grouping
concatenations.

[1] - https://github.com/NixOS/rfcs/blob/master/rfcs/0042-config-option.md
2022-01-26 21:04:50 -05:00

326 lines
13 KiB
Nix

{ config, lib, pkgs, ... }:
let
inherit (lib) mkOption types optionalString stringAfter;
cfg = config.boot.binfmt;
makeBinfmtLine = name: { recognitionType, offset, magicOrExtension
, mask, preserveArgvZero, openBinary
, matchCredentials, fixBinary, ...
}: let
type = if recognitionType == "magic" then "M" else "E";
offset' = toString offset;
mask' = toString mask;
interpreter = "/run/binfmt/${name}";
flags = if !(matchCredentials -> openBinary)
then throw "boot.binfmt.registrations.${name}: you can't specify openBinary = false when matchCredentials = true."
else optionalString preserveArgvZero "P" +
optionalString (openBinary && !matchCredentials) "O" +
optionalString matchCredentials "C" +
optionalString fixBinary "F";
in ":${name}:${type}:${offset'}:${magicOrExtension}:${mask'}:${interpreter}:${flags}";
activationSnippet = name: { interpreter, wrapInterpreterInShell, ... }: if wrapInterpreterInShell then ''
rm -f /run/binfmt/${name}
cat > /run/binfmt/${name} << 'EOF'
#!${pkgs.bash}/bin/sh
exec -- ${interpreter} "$@"
EOF
chmod +x /run/binfmt/${name}
'' else ''
rm -f /run/binfmt/${name}
ln -s ${interpreter} /run/binfmt/${name}
'';
getEmulator = system: (lib.systems.elaborate { inherit system; }).emulator pkgs;
getQemuArch = system: (lib.systems.elaborate { inherit system; }).qemuArch;
# Mapping of systems to “magicOrExtension” and “mask”. Mostly taken from:
# - https://github.com/cleverca22/nixos-configs/blob/master/qemu.nix
# and
# - https://github.com/qemu/qemu/blob/master/scripts/qemu-binfmt-conf.sh
# TODO: maybe put these in a JSON file?
magics = {
armv6l-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
};
armv7l-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
};
aarch64-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\x00\xff\xfe\xff\xff\xff'';
};
aarch64_be-linux = {
magicOrExtension = ''\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
i386-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03\x00'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
i486-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x06\x00'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
i586-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x06\x00'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
i686-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x06\x00'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
x86_64-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x3e\x00'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
alpha-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x26\x90'';
mask = ''\xff\xff\xff\xff\xff\xfe\xfe\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
sparc64-linux = {
magicOrExtension = ''\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x02'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
sparc-linux = {
magicOrExtension = ''\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x12'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
powerpc-linux = {
magicOrExtension = ''\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
powerpc64-linux = {
magicOrExtension = ''\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x15'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
powerpc64le-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x15\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\x00'';
};
mips-linux = {
magicOrExtension = ''\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
mipsel-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
mips64-linux = {
magicOrExtension = ''\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'';
};
mips64el-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
riscv32-linux = {
magicOrExtension = ''\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
riscv64-linux = {
magicOrExtension = ''\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00'';
mask = ''\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'';
};
wasm32-wasi = {
magicOrExtension = ''\x00asm'';
mask = ''\xff\xff\xff\xff'';
};
wasm64-wasi = {
magicOrExtension = ''\x00asm'';
mask = ''\xff\xff\xff\xff'';
};
x86_64-windows = {
magicOrExtension = ".exe";
recognitionType = "extension";
};
i686-windows = {
magicOrExtension = ".exe";
recognitionType = "extension";
};
};
in {
imports = [
(lib.mkRenamedOptionModule [ "boot" "binfmtMiscRegistrations" ] [ "boot" "binfmt" "registrations" ])
];
options = {
boot.binfmt = {
registrations = mkOption {
default = {};
description = ''
Extra binary formats to register with the kernel.
See https://www.kernel.org/doc/html/latest/admin-guide/binfmt-misc.html for more details.
'';
type = types.attrsOf (types.submodule ({ config, ... }: {
options = {
recognitionType = mkOption {
default = "magic";
description = "Whether to recognize executables by magic number or extension.";
type = types.enum [ "magic" "extension" ];
};
offset = mkOption {
default = null;
description = "The byte offset of the magic number used for recognition.";
type = types.nullOr types.int;
};
magicOrExtension = mkOption {
description = "The magic number or extension to match on.";
type = types.str;
};
mask = mkOption {
default = null;
description =
"A mask to be ANDed with the byte sequence of the file before matching";
type = types.nullOr types.str;
};
interpreter = mkOption {
description = ''
The interpreter to invoke to run the program.
Note that the actual registration will point to
/run/binfmt/''${name}, so the kernel interpreter length
limit doesn't apply.
'';
type = types.path;
};
preserveArgvZero = mkOption {
default = false;
description = ''
Whether to pass the original argv[0] to the interpreter.
See the description of the 'P' flag in the kernel docs
for more details;
'';
type = types.bool;
};
openBinary = mkOption {
default = config.matchCredentials;
description = ''
Whether to pass the binary to the interpreter as an open
file descriptor, instead of a path.
'';
type = types.bool;
};
matchCredentials = mkOption {
default = false;
description = ''
Whether to launch with the credentials and security
token of the binary, not the interpreter (e.g. setuid
bit).
See the description of the 'C' flag in the kernel docs
for more details.
Implies/requires openBinary = true.
'';
type = types.bool;
};
fixBinary = mkOption {
default = false;
description = ''
Whether to open the interpreter file as soon as the
registration is loaded, rather than waiting for a
relevant file to be invoked.
See the description of the 'F' flag in the kernel docs
for more details.
'';
type = types.bool;
};
wrapInterpreterInShell = mkOption {
default = true;
description = ''
Whether to wrap the interpreter in a shell script.
This allows a shell command to be set as the interpreter.
'';
type = types.bool;
};
interpreterSandboxPath = mkOption {
internal = true;
default = null;
description = ''
Path of the interpreter to expose in the build sandbox.
'';
type = types.nullOr types.path;
};
};
}));
};
emulatedSystems = mkOption {
default = [];
example = [ "wasm32-wasi" "x86_64-windows" "aarch64-linux" ];
description = ''
List of systems to emulate. Will also configure Nix to
support your new systems.
Warning: the builder can execute all emulated systems within the same build, which introduces impurities in the case of cross compilation.
'';
type = types.listOf types.str;
};
};
};
config = {
boot.binfmt.registrations = builtins.listToAttrs (map (system: {
name = system;
value = let
interpreter = getEmulator system;
qemuArch = getQemuArch system;
preserveArgvZero = "qemu-${qemuArch}" == baseNameOf interpreter;
interpreterReg = let
wrapperName = "qemu-${qemuArch}-binfmt-P";
wrapper = pkgs.wrapQemuBinfmtP wrapperName interpreter;
in
if preserveArgvZero then "${wrapper}/bin/${wrapperName}"
else interpreter;
in {
inherit preserveArgvZero;
interpreter = interpreterReg;
wrapInterpreterInShell = !preserveArgvZero;
interpreterSandboxPath = dirOf (dirOf interpreterReg);
} // (magics.${system} or (throw "Cannot create binfmt registration for system ${system}"));
}) cfg.emulatedSystems);
nix.settings = lib.mkIf (cfg.emulatedSystems != []) {
extra-platforms = cfg.emulatedSystems ++ lib.optional pkgs.stdenv.hostPlatform.isx86_64 "i686-linux";
extra-sandbox-paths = let
ruleFor = system: cfg.registrations.${system};
hasWrappedRule = lib.any (system: (ruleFor system).wrapInterpreterInShell) cfg.emulatedSystems;
in [ "/run/binfmt" ]
++ lib.optional hasWrappedRule "${pkgs.bash}"
++ (map (system: (ruleFor system).interpreterSandboxPath) cfg.emulatedSystems);
};
environment.etc."binfmt.d/nixos.conf".source = builtins.toFile "binfmt_nixos.conf"
(lib.concatStringsSep "\n" (lib.mapAttrsToList makeBinfmtLine config.boot.binfmt.registrations));
system.activationScripts.binfmt = stringAfter [ "specialfs" ] ''
mkdir -p -m 0755 /run/binfmt
${lib.concatStringsSep "\n" (lib.mapAttrsToList activationSnippet config.boot.binfmt.registrations)}
'';
systemd.additionalUpstreamSystemUnits = lib.mkIf (config.boot.binfmt.registrations != {}) [
"proc-sys-fs-binfmt_misc.automount"
"proc-sys-fs-binfmt_misc.mount"
"systemd-binfmt.service"
];
};
}