nixpkgs/nixos/modules/security/acme.nix
2020-04-21 15:50:31 +02:00

465 lines
19 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.security.acme;
certOpts = { name, ... }: {
options = {
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.";
};
user = mkOption {
type = types.str;
default = "root";
description = "User running the ACME client.";
};
group = mkOption {
type = types.str;
default = "root";
description = "Group running the ACME client.";
};
allowKeysForGroup = mkOption {
type = types.bool;
default = false;
description = ''
Give read permissions to the specified group
(<option>security.acme.cert.&lt;name&gt;.group</option>) to read SSL private certificates.
'';
};
postRun = mkOption {
type = types.lines;
default = "";
example = "systemctl reload nginx.service";
description = ''
Commands to run after new certificates go live. Typically
the web server and other servers using certificates need to
be reloaded.
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.";
};
extraDomains = mkOption {
type = types.attrsOf (types.nullOr types.str);
default = {};
example = literalExample ''
{
"example.org" = "/srv/http/nginx";
"mydomain.org" = null;
}
'';
description = ''
A list of extra domain names, which are included in the one certificate to be issued, with their
own server roots if needed.
'';
};
keyType = mkOption {
type = types.str;
default = "ec384";
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>
'';
};
extraLegoRenewFlags = mkOption {
type = types.listOf types.str;
default = [];
description = ''
Additional flags to pass to lego renew.
'';
};
};
};
in
{
###### interface
imports = [
(mkRemovedOptionModule [ "security" "acme" "production" ] ''
Use security.acme.server to define your staging ACME server URL instead.
To use Let's Encrypt's 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)))
];
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";
extraDomains = { "www.example.com" = null; "foo.example.com" = "/var/www/foo/"; };
};
"bar.example.com" = {
webroot = "/var/www/challenges/";
email = "bar@example.com";
};
}
'';
};
};
};
###### implementation
config = mkMerge [
(mkIf (cfg.certs != { }) {
assertions = let
certs = (mapAttrsToList (k: v: v) cfg.certs);
in [
{
assertion = all (certOpts: certOpts.dnsProvider == null || certOpts.webroot == null) certs;
message = ''
Options `security.acme.certs.<name>.dnsProvider` and
`security.acme.certs.<name>.webroot` are mutually exclusive.
'';
}
{
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.
'';
}
{
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/
'';
}
];
systemd.services = let
services = concatLists servicesLists;
servicesLists = mapAttrsToList certToServices cfg.certs;
certToServices = cert: data:
let
# StateDirectory must be relative, and will be created under /var/lib by systemd
lpath = "acme/${cert}";
apath = "/var/lib/${lpath}";
spath = "/var/lib/acme/.lego/${cert}";
fileMode = if data.allowKeysForGroup then "640" else "600";
globalOpts = [ "-d" data.domain "--email" data.email "--path" "." "--key-type" data.keyType ]
++ optionals (cfg.acceptTerms) [ "--accept-tos" ]
++ optionals (data.dnsProvider != null && !data.dnsPropagationCheck) [ "--dns.disable-cp" ]
++ concatLists (mapAttrsToList (name: root: [ "-d" name ]) data.extraDomains)
++ (if data.dnsProvider != null then [ "--dns" data.dnsProvider ] else [ "--http" "--http.webroot" data.webroot ])
++ optionals (cfg.server != null || data.server != null) ["--server" (if data.server == null then cfg.server else data.server)];
certOpts = optionals data.ocspMustStaple [ "--must-staple" ];
runOpts = escapeShellArgs (globalOpts ++ [ "run" ] ++ certOpts);
renewOpts = escapeShellArgs (globalOpts ++
[ "renew" "--days" (toString cfg.validMinDays) ] ++
certOpts ++ data.extraLegoRenewFlags);
acmeService = {
description = "Renew ACME Certificate for ${cert}";
after = [ "network.target" "network-online.target" ];
wants = [ "network-online.target" ];
wantedBy = mkIf (!config.boot.isContainer) [ "multi-user.target" ];
serviceConfig = {
Type = "oneshot";
User = data.user;
Group = data.group;
PrivateTmp = true;
StateDirectory = "acme/.lego/${cert} acme/.lego/accounts ${lpath}";
StateDirectoryMode = if data.allowKeysForGroup then "750" else "700";
WorkingDirectory = spath;
# Only try loading the credentialsFile if the dns challenge is enabled
EnvironmentFile = if data.dnsProvider != null then data.credentialsFile else null;
ExecStart = pkgs.writeScript "acme-start" ''
#!${pkgs.runtimeShell} -e
test -L ${spath}/accounts -o -d ${spath}/accounts || ln -s ../accounts ${spath}/accounts
${pkgs.lego}/bin/lego ${renewOpts} || ${pkgs.lego}/bin/lego ${runOpts}
'';
ExecStartPost =
let
keyName = builtins.replaceStrings ["*"] ["_"] data.domain;
script = pkgs.writeScript "acme-post-start" ''
#!${pkgs.runtimeShell} -e
cd ${apath}
# Test that existing cert is older than new cert
KEY=${spath}/certificates/${keyName}.key
KEY_CHANGED=no
if [ -e $KEY -a $KEY -nt key.pem ]; then
KEY_CHANGED=yes
cp -p ${spath}/certificates/${keyName}.key key.pem
cp -p ${spath}/certificates/${keyName}.crt fullchain.pem
cp -p ${spath}/certificates/${keyName}.issuer.crt chain.pem
ln -sf fullchain.pem cert.pem
cat key.pem fullchain.pem > full.pem
fi
chmod ${fileMode} *.pem
chown '${data.user}:${data.group}' *.pem
if [ "$KEY_CHANGED" = "yes" ]; then
: # noop in case postRun is empty
${data.postRun}
fi
'';
in
"+${script}";
};
};
selfsignedService = {
description = "Create preliminary self-signed certificate for ${cert}";
path = [ pkgs.openssl ];
script =
''
workdir="$(mktemp -d)"
# Create CA
openssl genrsa -des3 -passout pass:xxxx -out $workdir/ca.pass.key 2048
openssl rsa -passin pass:xxxx -in $workdir/ca.pass.key -out $workdir/ca.key
openssl req -new -key $workdir/ca.key -out $workdir/ca.csr \
-subj "/C=UK/ST=Warwickshire/L=Leamington/O=OrgName/OU=Security Department/CN=example.com"
openssl x509 -req -days 1 -in $workdir/ca.csr -signkey $workdir/ca.key -out $workdir/ca.crt
# Create key
openssl genrsa -des3 -passout pass:xxxx -out $workdir/server.pass.key 2048
openssl rsa -passin pass:xxxx -in $workdir/server.pass.key -out $workdir/server.key
openssl req -new -key $workdir/server.key -out $workdir/server.csr \
-subj "/C=UK/ST=Warwickshire/L=Leamington/O=OrgName/OU=IT Department/CN=example.com"
openssl x509 -req -days 1 -in $workdir/server.csr -CA $workdir/ca.crt \
-CAkey $workdir/ca.key -CAserial $workdir/ca.srl -CAcreateserial \
-out $workdir/server.crt
# Copy key to destination
cp $workdir/server.key ${apath}/key.pem
# Create fullchain.pem (same format as "simp_le ... -f fullchain.pem" creates)
cat $workdir/{server.crt,ca.crt} > "${apath}/fullchain.pem"
# Create full.pem for e.g. lighttpd
cat $workdir/{server.key,server.crt,ca.crt} > "${apath}/full.pem"
# Give key acme permissions
chown '${data.user}:${data.group}' "${apath}/"{key,fullchain,full}.pem
chmod ${fileMode} "${apath}/"{key,fullchain,full}.pem
'';
serviceConfig = {
Type = "oneshot";
PrivateTmp = true;
StateDirectory = lpath;
User = data.user;
Group = data.group;
};
unitConfig = {
# Do not create self-signed key when key already exists
ConditionPathExists = "!${apath}/key.pem";
};
};
in (
[ { name = "acme-${cert}"; value = acmeService; } ]
++ optional cfg.preliminarySelfsigned { name = "acme-selfsigned-${cert}"; value = selfsignedService; }
);
servicesAttr = listToAttrs services;
in
servicesAttr;
systemd.tmpfiles.rules =
map (data: "d ${data.webroot}/.well-known/acme-challenge - ${data.user} ${data.group}") (filter (data: data.webroot != null) (attrValues cfg.certs));
systemd.timers = let
# Allow systemd to pick a convenient time within the day
# to run the check.
# This allows the coalescing of multiple timer jobs.
# We divide by the number of certificates so that if you
# have many certificates, the renewals are distributed over
# the course of the day to avoid rate limits.
numCerts = length (attrNames cfg.certs);
_24hSecs = 60 * 60 * 24;
AccuracySec = "${toString (_24hSecs / numCerts)}s";
in flip mapAttrs' cfg.certs (cert: data: nameValuePair
("acme-${cert}")
({
description = "Renew ACME Certificate for ${cert}";
wantedBy = [ "timers.target" ];
timerConfig = {
OnCalendar = cfg.renewInterval;
Unit = "acme-${cert}.service";
Persistent = "yes";
inherit AccuracySec;
# Skew randomly within the day, per https://letsencrypt.org/docs/integration-guide/.
RandomizedDelaySec = "24h";
};
})
);
systemd.targets.acme-selfsigned-certificates = mkIf cfg.preliminarySelfsigned {};
systemd.targets.acme-certificates = {};
})
];
meta = {
maintainers = with lib.maintainers; [ abbradar fpletz globin m1cr0man ];
doc = ./acme.xml;
};
}