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nixpkgs/nixos/modules/security/acme.nix
Lucas Savva 34b5c5c1a4
nixos/acme: More features and fixes
- Allow for key reuse when domains are the only thing that
  were changed.
- Fixed systemd service failure when preliminarySelfsigned
  was set to false
2020-09-06 01:28:19 +01:00

674 lines
24 KiB
Nix

{ 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;
# 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 = 0027;
StateDirectoryMode = 750;
ProtectSystem = "full";
PrivateTmp = true;
WorkingDirectory = "/tmp";
};
# 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";
};
serviceConfig = commonServiceConfig // {
StateDirectory = "acme/.minica";
BindPaths = "/var/lib/acme/.minica:/tmp/ca";
};
# Working directory will be /tmp
script = ''
minica \
--ca-key ca/key.pem \
--ca-cert ca/cert.pem \
--domains selfsigned.local
chmod 600 ca/*
'';
};
# Previously, all certs were owned by whatever user was configured in
# config.security.acme.certs.<cert>.user. Now everything is owned by and
# run by the acme user.
userMigrationService = {
description = "Fix owner and group of all ACME certificates";
script = with builtins; concatStringsSep "\n" (mapAttrsToList (cert: data: ''
for fixpath in /var/lib/acme/${escapeShellArg cert} /var/lib/acme/.lego/${escapeShellArg cert}; do
if [ -d "$fixpath" ]; then
chmod -R 750 "$fixpath"
chown -R acme:${data.group} "$fixpath"
fi
done
'') certConfigs);
# We don't want this to run every time a renewal happens
serviceConfig.RemainAfterExit = true;
};
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} ${data.keyType}
'';
mkHash = with builtins; val: substring 0 20 (hashString "sha256" val);
certDir = mkHash hashData;
domainHash = mkHash "${concatStringsSep " " extraDomains} ${data.domain}";
othersHash = mkHash "${toString acmeServer} ${data.keyType}";
accountDir = "/var/lib/acme/.lego/accounts/" + othersHash;
protocolOpts = if useDns then (
[ "--dns" data.dnsProvider ]
++ optionals (!data.dnsPropagationCheck) [ "--dns.disable-cp" ]
) 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 data.ocspMustStaple [ "--must-staple" ]
++ optionals (acmeServer != null) [ "--server" acmeServer ]
++ concatMap (name: [ "-d" name ]) extraDomains
++ data.extraLegoFlags;
runOpts = escapeShellArgs (
commonOpts
++ [ "run" ]
++ data.extraLegoRunFlags
);
renewOpts = escapeShellArgs (
commonOpts
++ [ "renew" "--reuse-key" ]
++ data.extraLegoRenewFlags
);
in {
inherit accountDir selfsignedDeps;
webroot = data.webroot;
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 ${cert}";
after = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
requires = [ "acme-selfsigned-ca.service" "acme-fixperms.service" ];
path = with pkgs; [ minica ];
unitConfig = {
ConditionPathExists = "!/var/lib/acme/${cert}/key.pem";
};
serviceConfig = commonServiceConfig // {
Group = data.group;
StateDirectory = "acme/${cert}";
BindPaths = "/var/lib/acme/.minica:/tmp/ca /var/lib/acme/${cert}:/tmp/${keyName}";
};
# Working directory will be /tmp
# minica will output to a folder sharing the name of the first domain
# in the list, which will be ${data.domain}
script = ''
minica \
--ca-key ca/key.pem \
--ca-cert ca/cert.pem \
--domains ${escapeShellArg (builtins.concatStringsSep "," ([ data.domain ] ++ extraDomains))}
# Create files to match directory layout for real certificates
cd '${keyName}'
cp ../ca/cert.pem chain.pem
cat cert.pem chain.pem > fullchain.pem
cat key.pem fullchain.pem > full.pem
chmod 640 *
# Group might change between runs, re-apply it
chown 'acme:${data.group}' *
'';
};
renewService = {
description = "Renew ACME certificate for ${cert}";
after = [ "network.target" "network-online.target" "acme-fixperms.service" ] ++ selfsignedDeps;
wants = [ "network-online.target" "acme-fixperms.service" ] ++ selfsignedDeps;
# https://github.com/NixOS/nixpkgs/pull/81371#issuecomment-605526099
wantedBy = optionals (!config.boot.isContainer) [ "multi-user.target" ];
path = with pkgs; [ lego coreutils diffutils ];
serviceConfig = commonServiceConfig // {
Group = data.group;
# AccountDir dir will be created by tmpfiles to ensure correct permissions
# And to avoid deletion during systemctl clean
# acme/.lego/${cert} is listed so that it is deleted during systemctl clean
StateDirectory = "acme/${cert} acme/.lego/${cert} acme/.lego/${cert}/${certDir}";
# Needs to be space separated, but can't use a multiline string because that'll include newlines
BindPaths =
"${accountDir}:/tmp/accounts " +
"/var/lib/acme/${cert}:/tmp/out " +
"/var/lib/acme/.lego/${cert}/${certDir}:/tmp/certificates ";
# Only try loading the credentialsFile if the dns challenge is enabled
EnvironmentFile = mkIf useDns data.credentialsFile;
# Run as root (Prefixed with +)
ExecStartPost = "+" + (pkgs.writeShellScript "acme-postrun" ''
cd /var/lib/acme/${escapeShellArg cert}
if [ -e renewed ]; then
rm renewed
${data.postRun}
fi
'');
};
# Working directory will be /tmp
script = ''
set -euo pipefail
echo '${domainHash}' > domainhash.txt
# Check if we can renew
if [ -e 'certificates/${keyName}.key' -a -e 'certificates/${keyName}.crt' ]; then
# When domains are updated, there's no need to do a full
# Lego run, but it's likely renew won't work if days is too low.
if [ -e certificates/domainhash.txt ] && cmp -s domainhash.txt certificates/domainhash.txt; then
lego ${renewOpts} --days ${toString cfg.validMinDays}
else
# Any number > 90 works, but this one is over 9000 ;-)
lego ${renewOpts} --days 9001
fi
# Otherwise do a full run
else
lego ${runOpts}
fi
mv domainhash.txt certificates/
chmod 640 certificates/*
chmod -R 700 accounts/*
# Group might change between runs, re-apply it
chown 'acme:${data.group}' certificates/*
# Copy all certs to the "real" certs directory
CERT='certificates/${keyName}.crt'
if [ -e "$CERT" ] && ! cmp -s "$CERT" out/fullchain.pem; then
touch out/renewed
echo Installing new certificate
cp -vp 'certificates/${keyName}.crt' out/fullchain.pem
cp -vp 'certificates/${keyName}.key' out/key.pem
cp -vp 'certificates/${keyName}.issuer.crt' out/chain.pem
ln -sf fullchain.pem out/cert.pem
cat out/key.pem out/fullchain.pem > out/full.pem
fi
'';
};
};
certConfigs = mapAttrs certToConfig cfg.certs;
certOpts = { name, ... }: {
options = {
# user option has been removed
user = mkOption {
visible = false;
default = "_mkRemovedOptionModule";
};
# allowKeysForGroup option has been removed
allowKeysForGroup = mkOption {
visible = false;
default = "_mkRemovedOptionModule";
};
# extraDomains was replaced with extraDomainNames
extraDomains = mkOption {
visible = false;
default = "_mkMergedOptionModule";
};
webroot = mkOption {
type = types.nullOr types.str;
default = null;
example = "/var/lib/acme/acme-challenges";
description = ''
Where the webroot of the HTTP vhost is located.
<filename>.well-known/acme-challenge/</filename> directory
will be created below the webroot if it doesn't exist.
<literal>http://example.org/.well-known/acme-challenge/</literal> must also
be available (notice unencrypted HTTP).
'';
};
server = mkOption {
type = types.nullOr types.str;
default = null;
description = ''
ACME Directory Resource URI. Defaults to Let's Encrypt's
production endpoint,
<link xlink:href="https://acme-v02.api.letsencrypt.org/directory"/>, if unset.
'';
};
domain = mkOption {
type = types.str;
default = name;
description = "Domain to fetch certificate for (defaults to the entry name).";
};
email = mkOption {
type = types.nullOr types.str;
default = cfg.email;
description = "Contact email address for the CA to be able to reach you.";
};
group = mkOption {
type = types.str;
default = "acme";
description = "Group running the ACME client.";
};
postRun = mkOption {
type = types.lines;
default = "";
example = "cp full.pem backup.pem";
description = ''
Commands to run after new certificates go live. Note that
these commands run as the root user.
Executed in the same directory with the new certificate.
'';
};
directory = mkOption {
type = types.str;
readOnly = true;
default = "/var/lib/acme/${name}";
description = "Directory where certificate and other state is stored.";
};
extraDomainNames = mkOption {
type = types.listOf types.str;
default = [];
example = literalExample ''
[
"example.org"
"mydomain.org"
]
'';
description = ''
A list of extra domain names, which are included in the one certificate to be issued.
'';
};
keyType = mkOption {
type = types.str;
default = "ec256";
description = ''
Key type to use for private keys.
For an up to date list of supported values check the --key-type option
at <link xlink:href="https://go-acme.github.io/lego/usage/cli/#usage"/>.
'';
};
dnsProvider = mkOption {
type = types.nullOr types.str;
default = null;
example = "route53";
description = ''
DNS Challenge provider. For a list of supported providers, see the "code"
field of the DNS providers listed at <link xlink:href="https://go-acme.github.io/lego/dns/"/>.
'';
};
credentialsFile = mkOption {
type = types.path;
description = ''
Path to an EnvironmentFile for the cert's service containing any required and
optional environment variables for your selected dnsProvider.
To find out what values you need to set, consult the documentation at
<link xlink:href="https://go-acme.github.io/lego/dns/"/> for the corresponding dnsProvider.
'';
example = "/var/src/secrets/example.org-route53-api-token";
};
dnsPropagationCheck = mkOption {
type = types.bool;
default = true;
description = ''
Toggles lego DNS propagation check, which is used alongside DNS-01
challenge to ensure the DNS entries required are available.
'';
};
ocspMustStaple = mkOption {
type = types.bool;
default = false;
description = ''
Turns on the OCSP Must-Staple TLS extension.
Make sure you know what you're doing! See:
<itemizedlist>
<listitem><para><link xlink:href="https://blog.apnic.net/2019/01/15/is-the-web-ready-for-ocsp-must-staple/" /></para></listitem>
<listitem><para><link xlink:href="https://blog.hboeck.de/archives/886-The-Problem-with-OCSP-Stapling-and-Must-Staple-and-why-Certificate-Revocation-is-still-broken.html" /></para></listitem>
</itemizedlist>
'';
};
extraLegoFlags = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Additional global flags to pass to all lego commands.
'';
};
extraLegoRenewFlags = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Additional flags to pass to lego renew.
'';
};
extraLegoRunFlags = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Additional flags to pass to lego run.
'';
};
};
};
in {
options = {
security.acme = {
validMinDays = mkOption {
type = types.int;
default = 30;
description = "Minimum remaining validity before renewal in days.";
};
email = mkOption {
type = types.nullOr types.str;
default = null;
description = "Contact email address for the CA to be able to reach you.";
};
renewInterval = mkOption {
type = types.str;
default = "daily";
description = ''
Systemd calendar expression when to check for renewal. See
<citerefentry><refentrytitle>systemd.time</refentrytitle>
<manvolnum>7</manvolnum></citerefentry>.
'';
};
server = mkOption {
type = types.nullOr types.str;
default = null;
description = ''
ACME Directory Resource URI. Defaults to Let's Encrypt's
production endpoint,
<link xlink:href="https://acme-v02.api.letsencrypt.org/directory"/>, if unset.
'';
};
preliminarySelfsigned = mkOption {
type = types.bool;
default = true;
description = ''
Whether a preliminary self-signed certificate should be generated before
doing ACME requests. This can be useful when certificates are required in
a webserver, but ACME needs the webserver to make its requests.
With preliminary self-signed certificate the webserver can be started and
can later reload the correct ACME certificates.
'';
};
acceptTerms = mkOption {
type = types.bool;
default = false;
description = ''
Accept the CA's terms of service. The default provider is Let's Encrypt,
you can find their ToS at <link xlink:href="https://letsencrypt.org/repository/"/>.
'';
};
certs = mkOption {
default = { };
type = with types; attrsOf (submodule certOpts);
description = ''
Attribute set of certificates to get signed and renewed. Creates
<literal>acme-''${cert}.{service,timer}</literal> systemd units for
each certificate defined here. Other services can add dependencies
to those units if they rely on the certificates being present,
or trigger restarts of the service if certificates get renewed.
'';
example = literalExample ''
{
"example.com" = {
webroot = "/var/www/challenges/";
email = "foo@example.com";
extraDomainNames = [ "www.example.com" "foo.example.com" ];
};
"bar.example.com" = {
webroot = "/var/www/challenges/";
email = "bar@example.com";
};
}
'';
};
};
};
imports = [
(mkRemovedOptionModule [ "security" "acme" "production" ] ''
Use security.acme.server to define your staging ACME server URL instead.
To use the let's encrypt staging server, use security.acme.server =
"https://acme-staging-v02.api.letsencrypt.org/directory".
''
)
(mkRemovedOptionModule [ "security" "acme" "directory" ] "ACME Directory is now hardcoded to /var/lib/acme and its permisisons are managed by systemd. See https://github.com/NixOS/nixpkgs/issues/53852 for more info.")
(mkRemovedOptionModule [ "security" "acme" "preDelay" ] "This option has been removed. If you want to make sure that something executes before certificates are provisioned, add a RequiredBy=acme-\${cert}.service to the service you want to execute before the cert renewal")
(mkRemovedOptionModule [ "security" "acme" "activationDelay" ] "This option has been removed. If you want to make sure that something executes before certificates are provisioned, add a RequiredBy=acme-\${cert}.service to the service you want to execute before the cert renewal")
(mkChangedOptionModule [ "security" "acme" "validMin" ] [ "security" "acme" "validMinDays" ] (config: config.security.acme.validMin / (24 * 3600)))
];
config = mkMerge [
(mkIf (cfg.certs != { }) {
# FIXME Most of these custom warnings and filters for security.acme.certs.* are required
# because using mkRemovedOptionModule/mkChangedOptionModule with attrsets isn't possible.
warnings = filter (w: w != "") (mapAttrsToList (cert: data: if data.extraDomains != "_mkMergedOptionModule" then ''
The option definition `security.acme.certs.${cert}.extraDomains` has changed
to `security.acme.certs.${cert}.extraDomainNames` and is now a list of strings.
Setting a custom webroot for extra domains is not possible, instead use separate certs.
'' else "") cfg.certs);
assertions = let
certs = attrValues cfg.certs;
in [
{
assertion = cfg.email != null || all (certOpts: certOpts.email != null) certs;
message = ''
You must define `security.acme.certs.<name>.email` or
`security.acme.email` to register with the CA. Note that using
many different addresses for certs may trigger account rate limits.
'';
}
{
assertion = cfg.acceptTerms;
message = ''
You must accept the CA's terms of service before using
the ACME module by setting `security.acme.acceptTerms`
to `true`. For Let's Encrypt's ToS see https://letsencrypt.org/repository/
'';
}
] ++ (builtins.concatLists (mapAttrsToList (cert: data: [
{
assertion = data.user == "_mkRemovedOptionModule";
message = ''
The option definition `security.acme.certs.${cert}.user' no longer has any effect; Please remove it.
Certificate user is now hard coded to the "acme" user. If you would
like another user to have access, consider adding them to the
"acme" group or changing security.acme.certs.${cert}.group.
'';
}
{
assertion = data.allowKeysForGroup == "_mkRemovedOptionModule";
message = ''
The option definition `security.acme.certs.${cert}.allowKeysForGroup' no longer has any effect; Please remove it.
All certs are readable by the configured group. If this is undesired,
consider changing security.acme.certs.${cert}.group to an unused group.
'';
}
# * in the cert value breaks building of systemd services, and makes
# referencing them as a user quite weird too. Best practice is to use
# the domain option.
{
assertion = ! hasInfix "*" cert;
message = ''
The cert option path `security.acme.certs.${cert}.dnsProvider`
cannot contain a * character.
Instead, set `security.acme.certs.${cert}.domain = "${cert}";`
and remove the wildcard from the path.
'';
}
{
assertion = data.dnsProvider == null || data.webroot == null;
message = ''
Options `security.acme.certs.${cert}.dnsProvider` and
`security.acme.certs.${cert}.webroot` are mutually exclusive.
'';
}
]) cfg.certs));
users.users.acme = {
home = "/var/lib/acme";
group = "acme";
isSystemUser = true;
};
users.groups.acme = {};
systemd.services = {
"acme-fixperms" = userMigrationService;
} // (mapAttrs' (cert: conf: nameValuePair "acme-${cert}" conf.renewService) certConfigs)
// (optionalAttrs (cfg.preliminarySelfsigned) ({
"acme-selfsigned-ca" = selfsignCAService;
} // (mapAttrs' (cert: conf: nameValuePair "acme-selfsigned-${cert}" conf.selfsignService) certConfigs)));
systemd.timers = mapAttrs' (cert: conf: nameValuePair "acme-${cert}" conf.renewTimer) certConfigs;
# .lego and .lego/accounts specified to fix any incorrect permissions
systemd.tmpfiles.rules = [
"d /var/lib/acme/.lego - acme acme"
"d /var/lib/acme/.lego/accounts - acme acme"
] ++ (unique (concatMap (conf: [
"d ${conf.accountDir} - acme acme"
] ++ (optional (conf.webroot != null) "d ${conf.webroot}/.well-known/acme-challenge - acme ${conf.group}")
) (attrValues certConfigs)));
# Create some targets which can be depended on to be "active" after cert renewals
systemd.targets = mapAttrs' (cert: conf: nameValuePair "acme-finished-${cert}" {
wantedBy = [ "default.target" ];
requires = [ "acme-${cert}.service" ] ++ conf.selfsignedDeps;
after = [ "acme-${cert}.service" ] ++ conf.selfsignedDeps;
}) certConfigs;
})
];
meta = {
maintainers = lib.teams.acme.members;
doc = ./acme.xml;
};
}