nixos/acme: Add defaults and inheritDefaults option

Allows configuring many default settings for certificates,
all of which can still be overridden on a per-cert basis.
Some options have been moved into .defaults from security.acme,
namely email, server, validMinDays and renewInterval. These
changes will not break existing configurations thanks to
mkChangedOptionModule.

With this, it is also now possible to configure DNS-01 with
web servers whose virtualHosts utilise enableACME. The only
requirement is you set `acmeRoot = null` for each vhost.

The test suite has been revamped to cover these additions
and also to generally make it easier to maintain. Test config
for apache and nginx has been fully standardised, and it
is now much easier to add a new web server if it follows
the same configuration patterns as those two. I have also
optimised the use of switch-to-configuration which should
speed up testing.

2 files changed, 15 insertions, 5 deletions

diff --git a/nixos/modules/services/web-servers/apache-httpd/default.nix b/nixos/modules/services/web-servers/apache-httpd/default.nix
index 992a58875e435..1a49b4ca15c7c 100644
--- a/nixos/modules/services/web-servers/apache-httpd/default.nix
+++ b/nixos/modules/services/web-servers/apache-httpd/default.nix
@@ -154,7 +154,7 @@ let
       sslServerKey = if useACME then "${sslCertDir}/key.pem" else hostOpts.sslServerKey;
       sslServerChain = if useACME then "${sslCertDir}/chain.pem" else hostOpts.sslServerChain;
 
-      acmeChallenge = optionalString useACME ''
+      acmeChallenge = optionalString (useACME && hostOpts.acmeRoot != null) ''
         Alias /.well-known/acme-challenge/ "${hostOpts.acmeRoot}/.well-known/acme-challenge/"
         <Directory "${hostOpts.acmeRoot}">
             AllowOverride None
@@ -677,9 +677,16 @@ in
     };
 
     security.acme.certs = let
-      acmePairs = map (hostOpts: nameValuePair hostOpts.hostName {
+      acmePairs = map (hostOpts: let
+        hasRoot = hostOpts.acmeRoot != null;
+      in nameValuePair hostOpts.hostName {
         group = mkDefault cfg.group;
-        webroot = hostOpts.acmeRoot;
+        # if acmeRoot is null inherit config.security.acme
+        # Since config.security.acme.certs.<cert>.webroot's own default value
+        # should take precedence set priority higher than mkOptionDefault
+        webroot = mkOverride (if hasRoot then 1000 else 2000) hostOpts.acmeRoot;
+        # Also nudge dnsProvider to null in case it is inherited
+        dnsProvider = mkOverride (if hasRoot then 1000 else 2000) null;
         extraDomainNames = hostOpts.serverAliases;
         # Use the vhost-specific email address if provided, otherwise let
         # security.acme.email or security.acme.certs.<cert>.email be used.
diff --git a/nixos/modules/services/web-servers/apache-httpd/vhost-options.nix b/nixos/modules/services/web-servers/apache-httpd/vhost-options.nix
index 8bb7e91ec9cdb..c52ab2c596e01 100644
--- a/nixos/modules/services/web-servers/apache-httpd/vhost-options.nix
+++ b/nixos/modules/services/web-servers/apache-httpd/vhost-options.nix
@@ -128,9 +128,12 @@ in
     };
 
     acmeRoot = mkOption {
-      type = types.str;
+      type = types.nullOr types.str;
       default = "/var/lib/acme/acme-challenge";
-      description = "Directory for the acme challenge which is PUBLIC, don't put certs or keys in here";
+      description = ''
+        Directory for the acme challenge which is PUBLIC, don't put certs or keys in here.
+        Set to null to inherit from config.security.acme.
+      '';
     };
 
     sslServerCert = mkOption {