Ready for review. I have tested this out locally.

When the realm configuration files are large I'm seeing an error but this seems to be this related to this issue keycloak/keycloak#14733 but is not an issue with this specific PR.

Hi! Thanks for working on this.

One issue I can see arising from this is file/directory permissions - the service runs with DynamicUser set, so there's no globally available user to assign file ownership. We don't want to force the user to make the files world-readable, since they may contain sensitive data.

A solution could be to treat them the same way we already do ssl certificates / keys and create LoadCredential entries for all realms. This would change the option type to a list of paths to single-file json realm specifications that we could then copy to data/import and start Keycloak with --import-realm. This would also mean that the realms wouldn't be overridden on every start, which is probably more useful, since this feature mostly seems like a "restore from a backup" thing you'd want to do once.

Additionally, this should be added to the tests.

@talyz thanks for getting back!

One issue I can see arising from this is file/directory permissions - the service runs with DynamicUser set, so there's no globally available user to assign file ownership. We don't want to force the user to make the files world-readable, since they may contain sensitive data.

This isn't in the PR but keycloak supports environment variables within the json files see https://www.keycloak.org/server/importExport in the Using Environment Variables within the Realm Configuration Files section. If we had a way to pass environment variables to the systemd start. Would this be worth including the in the PR?

This would also mean that the realms wouldn't be overridden on every start, which is probably more useful, since this feature mostly seems like a "restore from a backup" thing you'd want to do once.

For me personally I like the idea of it overriding every time since this would allow me to declaratively manage users/groups/clients etc but I definitely see how only importing if the realm doesn't exist is valuable (and probably preferred by most). Maybe I add an option for override true/false?

Additionally, this should be added to the tests.

Will work on this once we have the scope down.

This isn't in the PR but keycloak supports environment variables within the json files see https://www.keycloak.org/server/importExport in the Using Environment Variables within the Realm Configuration Files section. If we had a way to pass environment variables to the systemd start. Would this be worth including the in the PR?

I suppose this could be done with systemd.services.keycloak.environment, but I'm not sure how useful it is in practice.

For me personally I like the idea of it overriding every time since this would allow me to declaratively manage users/groups/clients etc but I definitely see how only importing if the realm doesn't exist is valuable (and probably preferred by most). Maybe I add an option for override true/false?

I would love to support declarative realms as well, but in my mind, that would entail having a settings-like interface where you can write the realm spec in nix. The json format keycloak uses doesn't feel like it's made to be written manually (it's not documented, afaik, and I'm not sure how stable it is). I think you'd need to use the API to get the level of simplicity required and to be able to get a system where a part of a realm is declarative and another isn't - if a user changes their password, we don't want to reset it when the server restarts, for example.

I would love to support declarative realms as well, but in my mind, that would entail having a settings-like interface where you can write the realm spec in nix.

If I reworked this PR in this way how would you feel? Last time I added a bunch of nixos options there was some pushback due to the complexity. I would be happy to add this similar to how it was done for grafana https://github.com/nixos/nixpkgs/blob/nixpkgs-unstable/nixos/modules/services/monitoring/grafana.nix.

The specification is reasonably easy to find with an export. Here is an example with some of the options.

let keycloak-realms = pkgs.runCommand "keycloak-realms" {} ''
      mkdir -p $out
      echo '${builtins.toJSON example-realm}' > $out/example-realm.json
   '';

    # https://github.com/keycloak/keycloak-demo/blob/master/demo-realm.json
    example-realm = {
      realm = "demo1";
      enabled = true;

      users = [{
        username = "costrouc";
        enabled = true;
        firstName = "Chris";
        lastName = "Ostrouchov";
        credentials = [{
          type = "password";
          value = "test";
        }];
        realmRoles = [
          "user"
        ];
      }];

      groups = [{
        name = "admin-group";
        path = "/admin-group";
        attributes = {
          key = ["value1" "value2"];
        };
        realmRoles = [];
      }];

      roles = {
        realm = [
          {
            name = "user";
            description = "User privileges";
            attributes = {};
          }
          {
            name = "admin";
            description = "Administrator privileges";
            attributes = {};
          }
        ];
      };

      defaultRoles = [
        "user"
      ];

      clients = [
        {
          clientId = "conda-store";
          enabled = true;
          publicClient = false;
          serviceAccountsEnabled = true;
          redirectUris = [
            "https://example.com/callback"
          ];
          webOrigins = [
            "https://example.com"
          ];
        }
        {
          clientId = "demo-new-one";
          enabled = true;
          publicClient = false;
          clientAuthenticatorType = "client-secret";
          secret = "mysupersecret";
          redirectUris = [
            "https://demo-new-one.com/callback"
          ];
        }
      ];
    };
in {
services.keycloak.realmImportsDirectory = "${keycloak-realm}";
```}