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|
{ config, lib, pkgs, options, ... }:
with lib;
let
cfg = config.security.acme;
# Used to calculate timer accuracy for coalescing
numCerts = length (builtins.attrNames cfg.certs);
_24hSecs = 60 * 60 * 24;
# Used to make unique paths for each cert/account config set
mkHash = with builtins; val: substring 0 20 (hashString "sha256" val);
mkAccountHash = acmeServer: data: mkHash "${toString acmeServer} ${data.keyType} ${data.email}";
accountDirRoot = "/var/lib/acme/.lego/accounts/";
# There are many services required to make cert renewals work.
# They all follow a common structure:
# - They inherit this commonServiceConfig
# - They all run as the acme user
# - They all use BindPath and StateDirectory where possible
# to set up a sort of build environment in /tmp
# The Group can vary depending on what the user has specified in
# security.acme.certs.<cert>.group on some of the services.
commonServiceConfig = {
Type = "oneshot";
User = "acme";
Group = mkDefault "acme";
UMask = 0022;
StateDirectoryMode = 750;
ProtectSystem = "strict";
ReadWritePaths = [
"/var/lib/acme"
];
PrivateTmp = true;
WorkingDirectory = "/tmp";
CapabilityBoundingSet = [ "" ];
DevicePolicy = "closed";
LockPersonality = true;
MemoryDenyWriteExecute = true;
NoNewPrivileges = true;
PrivateDevices = true;
ProtectClock = true;
ProtectHome = true;
ProtectHostname = true;
ProtectControlGroups = true;
ProtectKernelLogs = true;
ProtectKernelModules = true;
ProtectKernelTunables = true;
ProtectProc = "invisible";
ProcSubset = "pid";
RemoveIPC = true;
RestrictAddressFamilies = [
"AF_INET"
"AF_INET6"
];
RestrictNamespaces = true;
RestrictRealtime = true;
RestrictSUIDSGID = true;
SystemCallArchitectures = "native";
SystemCallFilter = [
# 1. allow a reasonable set of syscalls
"@system-service"
# 2. and deny unreasonable ones
"~@privileged @resources"
# 3. then allow the required subset within denied groups
"@chown"
];
};
# In order to avoid race conditions creating the CA for selfsigned certs,
# we have a separate service which will create the necessary files.
selfsignCAService = {
description = "Generate self-signed certificate authority";
path = with pkgs; [ minica ];
unitConfig = {
ConditionPathExists = "!/var/lib/acme/.minica/key.pem";
StartLimitIntervalSec = 0;
};
serviceConfig = commonServiceConfig // {
StateDirectory = "acme/.minica";
BindPaths = "/var/lib/acme/.minica:/tmp/ca";
UMask = 0077;
};
# Working directory will be /tmp
script = ''
minica \
--ca-key ca/key.pem \
--ca-cert ca/cert.pem \
--domains selfsigned.local
'';
};
# Ensures that directories which are shared across all certs
# exist and have the correct user and group, since group
# is configurable on a per-cert basis.
userMigrationService = let
script = with builtins; ''
chown -R acme .lego/accounts
'' + (concatStringsSep "\n" (mapAttrsToList (cert: data: ''
for fixpath in ${escapeShellArg cert} .lego/${escapeShellArg cert}; do
if [ -d "$fixpath" ]; then
chmod -R u=rwX,g=rX,o= "$fixpath"
chown -R acme:${data.group} "$fixpath"
fi
done
'') certConfigs));
in {
description = "Fix owner and group of all ACME certificates";
serviceConfig = commonServiceConfig // {
# We don't want this to run every time a renewal happens
RemainAfterExit = true;
# These StateDirectory entries negate the need for tmpfiles
StateDirectory = [ "acme" "acme/.lego" "acme/.lego/accounts" ];
StateDirectoryMode = 755;
WorkingDirectory = "/var/lib/acme";
# Run the start script as root
ExecStart = "+" + (pkgs.writeShellScript "acme-fixperms" script);
};
};
certToConfig = cert: data: let
acmeServer = if data.server != null then data.server else cfg.server;
useDns = data.dnsProvider != null;
destPath = "/var/lib/acme/${cert}";
selfsignedDeps = optionals (cfg.preliminarySelfsigned) [ "acme-selfsigned-${cert}.service" ];
# Minica and lego have a "feature" which replaces * with _. We need
# to make this substitution to reference the output files from both programs.
# End users never see this since we rename the certs.
keyName = builtins.replaceStrings ["*"] ["_"] data.domain;
# FIXME when mkChangedOptionModule supports submodules, change to that.
# This is a workaround
extraDomains = data.extraDomainNames ++ (
optionals
(data.extraDomains != "_mkMergedOptionModule")
(builtins.attrNames data.extraDomains)
);
# Create hashes for cert data directories based on configuration
# Flags are separated to avoid collisions
hashData = with builtins; ''
${concatStringsSep " " data.extraLegoFlags} -
${concatStringsSep " " data.extraLegoRunFlags} -
${concatStringsSep " " data.extraLegoRenewFlags} -
${toString acmeServer} ${toString data.dnsProvider}
${toString data.ocspMustStaple} ${data.keyType}
'';
certDir = mkHash hashData;
domainHash = mkHash "${concatStringsSep " " extraDomains} ${data.domain}";
accountHash = (mkAccountHash acmeServer data);
accountDir = accountDirRoot + accountHash;
protocolOpts = if useDns then (
[ "--dns" data.dnsProvider ]
++ optionals (!data.dnsPropagationCheck) [ "--dns.disable-cp" ]
++ optionals (data.dnsResolver != null) [ "--dns.resolvers" data.dnsResolver ]
) else (
[ "--http" "--http.webroot" data.webroot ]
);
commonOpts = [
"--accept-tos" # Checking the option is covered by the assertions
"--path" "."
"-d" data.domain
"--email" data.email
"--key-type" data.keyType
] ++ protocolOpts
++ optionals (acmeServer != null) [ "--server" acmeServer ]
++ concatMap (name: [ "-d" name ]) extraDomains
++ data.extraLegoFlags;
# Although --must-staple is common to both modes, it is not declared as a
# mode-agnostic argument in lego and thus must come after the mode.
runOpts = escapeShellArgs (
commonOpts
++ [ "run" ]
++ optionals data.ocspMustStaple [ "--must-staple" ]
++ data.extraLegoRunFlags
);
renewOpts = escapeShellArgs (
commonOpts
++ [ "renew" ]
++ optionals data.ocspMustStaple [ "--must-staple" ]
++ data.extraLegoRenewFlags
);
# We need to collect all the ACME webroots to grant them write
# access in the systemd service.
webroots =
lib.remove null
(lib.unique
(builtins.map
(certAttrs: certAttrs.webroot)
(lib.attrValues config.security.acme.certs)));
in {
inherit accountHash cert selfsignedDeps;
group = data.group;
renewTimer = {
description = "Renew ACME Certificate for ${cert}";
wantedBy = [ "timers.target" ];
timerConfig = {
OnCalendar = cfg.renewInterval;
Unit = "acme-${cert}.service";
Persistent = "yes";
# Allow systemd to pick a convenient time within the day
# to run the check.
# This allows the coalescing of multiple timer jobs.
# We divide by the number of certificates so that if you
# have many certificates, the renewals are distributed over
# the course of the day to avoid rate limits.
AccuracySec = "${toString (_24hSecs / numCerts)}s";
# Skew randomly within the day, per https://letsencrypt.org/docs/integration-guide/.
RandomizedDelaySec = "24h";
};
};
selfsignService = {
description = "Generate self-signed certificate for ${cert}";
after = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
requires = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
path = with pkgs
|