Secure boot works!

This commit is contained in:
Artemis Tosini 2020-05-13 01:19:30 +00:00
parent 41cf59d7a7
commit 8a2a6c9702
Signed by: artemist
GPG key ID: EE5227935FE3FF18
4 changed files with 540 additions and 1 deletions

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@ -1,11 +1,17 @@
{ config, pkgs, ... }:
{
imports = [ ./externals/systemd-boot-secure ];
boot = {
kernelPackages = pkgs.linuxPackages_latest;
kernel.sysctl."vm.swappiness" = 5;
cleanTmpDir = true;
loader.systemd-boot.enable = true;
loader.systemd-boot-secure = {
enable = true;
signed = true;
signing-key = "/root/secure-boot/db.key";
signing-certificate = "/root/secure-boot/db.crt";
};
initrd.luks = {
reusePassphrases = true;

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@ -0,0 +1,179 @@
{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.boot.loader.systemd-boot-secure;
efi = config.boot.loader.efi;
gummibootBuilder = pkgs.substituteAll {
src = ./systemd-boot-builder.py;
isExecutable = true;
inherit (pkgs.buildPackages) python3 sbsigntool;
binutils = pkgs.buildPackages.binutils-unwrapped;
systemd = config.systemd.package;
nix = config.nix.package.out;
timeout = if config.boot.loader.timeout != null then config.boot.loader.timeout else "";
editor = if cfg.editor then "True" else "False";
configurationLimit = if cfg.configurationLimit == null then 0 else cfg.configurationLimit;
inherit (cfg) consoleMode;
inherit (efi) efiSysMountPoint canTouchEfiVariables;
memtest86 = if cfg.memtest86.enable then pkgs.memtest86-efi else "";
inherit (cfg) signed;
signingKey = if cfg.signed then cfg.signing-key else "/no-signing-key";
signingCertificate = if cfg.signed then cfg.signing-certificate else "/no-signing-crt";
};
in {
options.boot.loader.systemd-boot-secure = {
enable = mkOption {
default = false;
type = types.bool;
description = "Whether to enable the systemd-boot (formerly gummiboot) EFI boot manager";
};
signed = mkOption {
default = false;
type = types.bool;
description = ''
Whether or not the bootloader files, including systemd-boot
EFI programs should be signed.
'';
};
signing-key = mkOption {
type = types.path;
example = "/root/secure-boot/db.key";
description = ''
The <literal>db.key</literal> signing key, for signing EFI
programs. Note: Do not pass a store path. Passing the key like
<literal>signing-key = ./db.key;</literal> will copy the
private key in to the Nix store and make it world-readable.
Instead, pass the path as an absolute path string, like:
<literal>signing-key = "/root/secure-boot/db.key";</literal>.
'';
};
signing-certificate = mkOption {
type = types.path;
example = "/root/secure-boot/db.crt";
description = ''
The <literal>db.crt</literal> signing certificate, for signing
EFI programs. Note: certificate files are not private.
'';
};
editor = mkOption {
default = true;
type = types.bool;
description = ''
Whether to allow editing the kernel command-line before
boot. It is recommended to set this to false, as it allows
gaining root access by passing init=/bin/sh as a kernel
parameter. However, it is enabled by default for backwards
compatibility.
'';
};
configurationLimit = mkOption {
default = null;
example = 120;
type = types.nullOr types.int;
description = ''
Maximum number of latest generations in the boot menu.
Useful to prevent boot partition running out of disk space.
<literal>null</literal> means no limit i.e. all generations
that were not garbage collected yet.
'';
};
consoleMode = mkOption {
default = "keep";
type = types.enum [ "0" "1" "2" "auto" "max" "keep" ];
description = ''
The resolution of the console. The following values are valid:
<itemizedlist>
<listitem><para>
<literal>"0"</literal>: Standard UEFI 80x25 mode
</para></listitem>
<listitem><para>
<literal>"1"</literal>: 80x50 mode, not supported by all devices
</para></listitem>
<listitem><para>
<literal>"2"</literal>: The first non-standard mode provided by the device firmware, if any
</para></listitem>
<listitem><para>
<literal>"auto"</literal>: Pick a suitable mode automatically using heuristics
</para></listitem>
<listitem><para>
<literal>"max"</literal>: Pick the highest-numbered available mode
</para></listitem>
<listitem><para>
<literal>"keep"</literal>: Keep the mode selected by firmware (the default)
</para></listitem>
</itemizedlist>
'';
};
memtest86 = {
enable = mkOption {
default = false;
type = types.bool;
description = ''
Make MemTest86 available from the systemd-boot menu. MemTest86 is a
program for testing memory. MemTest86 is an unfree program, so
this requires <literal>allowUnfree</literal> to be set to
<literal>true</literal>.
'';
};
};
};
config = mkIf cfg.enable {
assertions = [
{
assertion = (config.boot.kernelPackages.kernel.features or { efiBootStub = true; }) ? efiBootStub;
message = "This kernel does not support the EFI boot stub";
}
];
boot.loader.grub.enable = mkDefault false;
boot.loader.supportsInitrdSecrets = true;
system = {
build.installBootLoader = gummibootBuilder;
boot.loader.id = "systemd-boot";
requiredKernelConfig = with config.lib.kernelConfig; [
(isYes "EFI_STUB")
];
};
};
}

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@ -0,0 +1,351 @@
#! @python3@/bin/python3 -B
import argparse
import shutil
import os
import sys
import errno
import subprocess
import glob
import tempfile
import warnings
import ctypes
libc = ctypes.CDLL("libc.so.6")
import re
import datetime
import os.path
def copy_if_not_exists(source, dest):
if not os.path.exists(dest):
shutil.copyfile(source, dest)
def system_dir(profile, generation):
if profile:
return "/nix/var/nix/profiles/system-profiles/%s-%d-link" % (profile, generation)
else:
return "/nix/var/nix/profiles/system-%d-link" % (generation)
SECURE_BOOT_ENTRY = """title NixOS{profile}
version Generation {generation} {description} (Secure Boot)
efi {efi}
"""
BOOT_ENTRY = """title NixOS{profile}
version Generation {generation} {description}
linux {kernel}
initrd {initrd}
options {kernel_params}
"""
# The boot loader entry for memtest86.
#
# TODO: This is hard-coded to use the 64-bit EFI app, but it could probably
# be updated to use the 32-bit EFI app on 32-bit systems. The 32-bit EFI
# app filename is BOOTIA32.efi.
MEMTEST_BOOT_ENTRY = """title MemTest86
efi /efi/memtest86/BOOTX64.efi
"""
def write_loader_conf(profile, generation):
with open("@efiSysMountPoint@/loader/loader.conf.tmp", 'w') as f:
if "@timeout@" != "":
f.write("timeout @timeout@\n")
if profile:
f.write("default nixos-%s-generation-%d\n" % (profile, generation))
else:
f.write("default nixos-generation-%d\n" % (generation))
if "@editor@" != "1":
f.write("editor 0\n");
f.write("console-mode @consoleMode@\n");
os.rename("@efiSysMountPoint@/loader/loader.conf.tmp", "@efiSysMountPoint@/loader/loader.conf")
def profile_path(profile, generation, name):
return os.readlink("%s/%s" % (system_dir(profile, generation), name))
def copy_from_profile(profile, generation, name, dry_run=False):
store_file_path = profile_path(profile, generation, name)
suffix = os.path.basename(store_file_path)
store_dir = os.path.basename(os.path.dirname(store_file_path))
efi_file_path = "/efi/nixos/%s-%s.efi" % (store_dir, suffix)
if not dry_run:
copy_if_not_exists(store_file_path, "@efiSysMountPoint@%s" % (efi_file_path))
return efi_file_path
def describe_generation(generation_dir):
try:
with open("%s/nixos-version" % generation_dir) as f:
nixos_version = f.read()
except IOError:
nixos_version = "Unknown"
kernel_dir = os.path.dirname(os.path.realpath("%s/kernel" % generation_dir))
module_dir = glob.glob("%s/lib/modules/*" % kernel_dir)[0]
kernel_version = os.path.basename(module_dir)
build_time = int(os.path.getctime(generation_dir))
build_date = datetime.datetime.fromtimestamp(build_time).strftime('%F')
description = "NixOS {}, Linux Kernel {}, Built on {}".format(
nixos_version, kernel_version, build_date
)
return description
def write_entry(profile, generation, machine_id):
kernel = copy_from_profile(profile, generation, "kernel")
initrd = copy_from_profile(profile, generation, "initrd")
try:
append_initrd_secrets = profile_path(profile, generation, "append-initrd-secrets")
subprocess.check_call([append_initrd_secrets, "@efiSysMountPoint@%s" % (initrd)])
except FileNotFoundError:
pass
if profile:
entry_file = "@efiSysMountPoint@/loader/entries/nixos-%s-generation-%d.conf" % (profile, generation)
else:
entry_file = "@efiSysMountPoint@/loader/entries/nixos-generation-%d.conf" % (generation)
generation_dir = os.readlink(system_dir(profile, generation))
tmp_path = "%s.tmp" % (entry_file)
kernel_params = "systemConfig=%s init=%s/init " % (generation_dir, generation_dir)
with open("%s/kernel-params" % (generation_dir)) as params_file:
kernel_params = kernel_params + params_file.read()
with open(tmp_path, 'w') as f:
f.write(BOOT_ENTRY.format(profile=" [" + profile + "]" if profile else "",
generation=generation,
kernel=kernel,
initrd=initrd,
kernel_params=kernel_params,
description=describe_generation(generation_dir)))
if machine_id is not None:
f.write("machine-id %s\n" % machine_id)
os.rename(tmp_path, entry_file)
def sb_efi_file_name_relative(profile, generation):
if profile:
return "efi/nixos/nixos-%s-generation-%d.efi" % (profile, generation)
else:
return "efi/nixos/nixos-generation-%d.efi" % (generation)
def make_signed_efi(profile, generation, efi_file):
with tempfile.TemporaryDirectory() as tmpdir:
append_initrd_secrets = profile_path(profile, generation, "append-initrd-secrets")
if os.path.exists(append_initrd_secrets):
initrd = f"{tmpdir}/initrd"
shutil.copyfile(
profile_path(profile, generation, "initrd"),
initrd
)
subprocess.check_call([append_initrd_secrets, "@efiSysMountPoint@%s" % (initrd)])
else:
initrd = profile_path(profile, generation, "initrd"),
generation_dir = os.readlink(system_dir(profile, generation))
tmp_path = "%s/efistub" % (tmpdir)
kernel_params = "systemConfig=%s init=%s/init " % (generation_dir, generation_dir)
with open("%s/kernel-params" % (generation_dir)) as params_file:
kernel_params = kernel_params + params_file.read()
kernel_param_file = "%s/kernel_params" % tmpdir
with open(kernel_param_file, 'w') as f:
f.write(kernel_params)
subprocess.check_call([
"@binutils@/bin/objcopy",
"--add-section", ".osrel={}/etc/os-release".format(generation_dir), "--change-section-vma", ".osrel=0x20000",
"--add-section", ".cmdline={}".format(kernel_param_file), "--change-section-vma", ".cmdline=0x30000",
"--add-section", ".linux={}/kernel".format(generation_dir), "--change-section-vma", ".linux=0x40000",
"--add-section", ".initrd={}".format(initrd), "--change-section-vma", ".initrd=0x3000000",
"{}/sw/lib/systemd/boot/efi/linuxx64.efi.stub".format(generation_dir),
tmp_path
])
sign_path(tmp_path, efi_file)
def write_secureboot_entry(profile, generation, machine_id):
if profile:
entry_file = "@efiSysMountPoint@/loader/entries/nixos-%s-generation-%d.conf" % (profile, generation)
else:
entry_file = "@efiSysMountPoint@/loader/entries/nixos-generation-%d.conf" % (generation)
efi_file_relative = sb_efi_file_name_relative(profile, generation)
efi_file = "@efiSysMountPoint@/%s" % (efi_file_relative)
try:
sbverify(efi_file)
except:
make_signed_efi(profile, generation, efi_file)
generation_dir = os.readlink(system_dir(profile, generation))
entry_tmp = entry_file + ".tmp";
with open(entry_tmp, 'w') as fp:
fp.write(SECURE_BOOT_ENTRY.format(
profile=" [" + profile + "]" if profile else "",
generation=generation,
efi=efi_file_relative,
description=describe_generation(generation_dir)
))
if machine_id is not None:
fp.write("machine-id %s\n" % machine_id)
os.rename(entry_tmp, entry_file)
def sign_path(src, output):
with tempfile.TemporaryDirectory() as tmpdir:
print(f"Signing {output}")
subprocess.check_call([
"@sbsigntool@/bin/sbsign",
"--key", "@signingKey@",
"--cert", "@signingCertificate@",
"--output", f"{tmpdir}/signed",
src
])
# Very likely to move across filesystems, so use
# shutil.move over os.rename.
shutil.move(f"{tmpdir}/signed", f"{output}.tmp")
try:
sbverify(f"{output}.tmp")
os.rename(f"{output}.tmp", output)
except:
os.unlink(f"{output}.tmp")
raise
def sbverify(filename):
subprocess.check_call([
"@sbsigntool@/bin/sbverify",
"--cert", "@signingCertificate@",
filename,
])
def mkdir_p(path):
try:
os.makedirs(path)
except OSError as e:
if e.errno != errno.EEXIST or not os.path.isdir(path):
raise
def get_generations(profile=None):
gen_list = subprocess.check_output([
"@nix@/bin/nix-env",
"--list-generations",
"-p",
"/nix/var/nix/profiles/%s" % ("system-profiles/" + profile if profile else "system"),
"--option", "build-users-group", ""],
universal_newlines=True)
gen_lines = gen_list.split('\n')
gen_lines.pop()
configurationLimit = @configurationLimit@
return [ (profile, int(line.split()[0])) for line in gen_lines ][-configurationLimit:]
def remove_old_entries(gens):
rex_profile = re.compile("^@efiSysMountPoint@/loader/entries/nixos-(.*)-generation-.*\.conf$")
rex_generation = re.compile("^@efiSysMountPoint@/loader/entries/nixos.*-generation-(.*)\.conf$")
known_paths = []
for gen in gens:
known_paths.append(copy_from_profile(*gen, "kernel", True))
known_paths.append(copy_from_profile(*gen, "initrd", True))
known_paths.append("@efiSysMountPoint@/%s" % sb_efi_file_name_relative(*gen))
for path in glob.iglob("@efiSysMountPoint@/loader/entries/nixos*-generation-[1-9]*.conf"):
try:
if rex_profile.match(path):
prof = rex_profile.sub(r"\1", path)
else:
prof = "system"
gen = int(rex_generation.sub(r"\1", path))
if not (prof, gen) in gens:
os.unlink(path)
except ValueError:
pass
for path in glob.iglob("@efiSysMountPoint@/efi/nixos/*"):
if not path in known_paths and not os.path.isdir(path):
os.unlink(path)
def get_profiles():
if os.path.isdir("/nix/var/nix/profiles/system-profiles/"):
return [x
for x in os.listdir("/nix/var/nix/profiles/system-profiles/")
if not x.endswith("-link")]
else:
return []
def main():
parser = argparse.ArgumentParser(description='Update NixOS-related systemd-boot files')
parser.add_argument('default_config', metavar='DEFAULT-CONFIG', help='The default NixOS config to boot')
args = parser.parse_args()
try:
with open("/etc/machine-id") as machine_file:
machine_id = machine_file.readlines()[0]
except IOError as e:
if e.errno != errno.ENOENT:
raise
# Since systemd version 232 a machine ID is required and it might not
# be there on newly installed systems, so let's generate one so that
# bootctl can find it and we can also pass it to write_entry() later.
cmd = ["@systemd@/bin/systemd-machine-id-setup", "--print"]
machine_id = subprocess.check_output(cmd).rstrip()
if os.getenv("NIXOS_INSTALL_GRUB") == "1":
warnings.warn("NIXOS_INSTALL_GRUB env var deprecated, use NIXOS_INSTALL_BOOTLOADER", DeprecationWarning)
os.environ["NIXOS_INSTALL_BOOTLOADER"] = "1"
if os.getenv("NIXOS_INSTALL_BOOTLOADER") == "1":
# bootctl uses fopen() with modes "wxe" and fails if the file exists.
if os.path.exists("@efiSysMountPoint@/loader/loader.conf"):
os.unlink("@efiSysMountPoint@/loader/loader.conf")
if "@canTouchEfiVariables@" == "1":
subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "install"])
else:
subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "--no-variables", "install"])
mkdir_p("@efiSysMountPoint@/efi/nixos")
mkdir_p("@efiSysMountPoint@/loader/entries")
if "@signed@" == "1":
sign_path("@efiSysMountPoint@/EFI/BOOT/BOOTX64.EFI", "@efiSysMountPoint@/EFI/BOOT/BOOTX64.EFI")
sign_path("@efiSysMountPoint@/EFI/systemd/systemd-bootx64.efi", "@efiSysMountPoint@/EFI/systemd/systemd-bootx64.efi")
gens = get_generations()
for profile in get_profiles():
gens += get_generations(profile)
remove_old_entries(gens)
for gen in gens:
if "@signed@"== "1":
write_secureboot_entry(*gen, machine_id)
else:
write_entry(*gen, machine_id)
if os.readlink(system_dir(*gen)) == args.default_config:
write_loader_conf(*gen)
memtest_entry_file = "@efiSysMountPoint@/loader/entries/memtest86.conf"
if os.path.exists(memtest_entry_file):
os.unlink(memtest_entry_file)
shutil.rmtree("@efiSysMountPoint@/efi/memtest86", ignore_errors=True)
if "@memtest86@" != "":
mkdir_p("@efiSysMountPoint@/efi/memtest86")
for path in glob.iglob("@memtest86@/*"):
if os.path.isdir(path):
shutil.copytree(path, os.path.join("@efiSysMountPoint@/efi/memtest86", os.path.basename(path)))
else:
shutil.copy(path, "@efiSysMountPoint@/efi/memtest86/")
memtest_entry_file = "@efiSysMountPoint@/loader/entries/memtest86.conf"
memtest_entry_file_tmp_path = "%s.tmp" % memtest_entry_file
with open(memtest_entry_file_tmp_path, 'w') as f:
f.write(MEMTEST_BOOT_ENTRY)
os.rename(memtest_entry_file_tmp_path, memtest_entry_file)
# Since fat32 provides little recovery facilities after a crash,
# it can leave the system in an unbootable state, when a crash/outage
# happens shortly after an update. To decrease the likelihood of this
# event sync the efi filesystem after each update.
rc = libc.syncfs(os.open("@efiSysMountPoint@", os.O_RDONLY))
if rc != 0:
print("could not sync @efiSysMountPoint@: {}".format(os.strerror(rc)), file=sys.stderr)
if __name__ == '__main__':
main()

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@ -53,6 +53,8 @@ in
# Linux tools
cachix
dmidecode
efibootmgr
efitools
gparted
hdparm
iptables
@ -135,6 +137,7 @@ in
curlFull
httpie
iodine
magic-wormhole
megatools
mosh
sshfs