From 6d299334b0ca99f91890c8396d6ed73839535ec4 Mon Sep 17 00:00:00 2001
From: s1341 <github@shmarya.net>
Date: Thu, 16 Mar 2023 08:40:13 +0200
Subject: [PATCH] nixos/freeipa: init

---
 nixos/modules/module-list.nix  |   1 +
 nixos/modules/security/ipa.nix | 258 +++++++++++++++++++++++++++++++++
 2 files changed, 259 insertions(+)
 create mode 100644 nixos/modules/security/ipa.nix

diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix
index e1e30c99a447..43d951e42b03 100644
--- a/nixos/modules/module-list.nix
+++ b/nixos/modules/module-list.nix
@@ -277,6 +277,7 @@
   ./security/doas.nix
   ./security/duosec.nix
   ./security/google_oslogin.nix
+  ./security/ipa.nix
   ./security/lock-kernel-modules.nix
   ./security/misc.nix
   ./security/oath.nix
diff --git a/nixos/modules/security/ipa.nix b/nixos/modules/security/ipa.nix
new file mode 100644
index 000000000000..7075be95040e
--- /dev/null
+++ b/nixos/modules/security/ipa.nix
@@ -0,0 +1,258 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.security.ipa;
+  pyBool = x:
+    if x
+    then "True"
+    else "False";
+
+  ldapConf = pkgs.writeText "ldap.conf" ''
+    # Turning this off breaks GSSAPI used with krb5 when rdns = false
+    SASL_NOCANON    on
+
+    URI ldaps://${cfg.server}
+    BASE ${cfg.basedn}
+    TLS_CACERT /etc/ipa/ca.crt
+  '';
+  nssDb =
+    pkgs.runCommand "ipa-nssdb"
+    {
+      nativeBuildInputs = [pkgs.nss.tools];
+    } ''
+      mkdir -p $out
+      certutil -d $out -N --empty-password
+      certutil -d $out -A --empty-password -n "${cfg.realm} IPA CA" -t CT,C,C -i ${cfg.certificate}
+    '';
+in {
+  options = {
+    security.ipa = {
+      enable = mkEnableOption (lib.mdDoc "FreeIPA domain integration");
+
+      certificate = mkOption {
+        type = types.package;
+        description = lib.mdDoc ''
+          IPA server CA certificate.
+
+          Use `nix-prefetch-url http://$server/ipa/config/ca.crt` to
+          obtain the file and the hash.
+        '';
+        example = literalExpression ''
+          pkgs.fetchurl {
+            url = http://ipa.example.com/ipa/config/ca.crt;
+            sha256 = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+          };
+        '';
+      };
+
+      domain = mkOption {
+        type = types.str;
+        example = "example.com";
+        description = lib.mdDoc "Domain of the IPA server.";
+      };
+
+      realm = mkOption {
+        type = types.str;
+        example = "EXAMPLE.COM";
+        description = lib.mdDoc "Kerberos realm.";
+      };
+
+      server = mkOption {
+        type = types.str;
+        example = "ipa.example.com";
+        description = lib.mdDoc "IPA Server hostname.";
+      };
+
+      basedn = mkOption {
+        type = types.str;
+        example = "dc=example,dc=com";
+        description = lib.mdDoc "Base DN to use when performing LDAP operations.";
+      };
+
+      offlinePasswords = mkOption {
+        type = types.bool;
+        default = true;
+        description = lib.mdDoc "Whether to store offline passwords when the server is down.";
+      };
+
+      cacheCredentials = mkOption {
+        type = types.bool;
+        default = true;
+        description = lib.mdDoc "Whether to cache credentials.";
+      };
+
+      ifpAllowedUids = mkOption {
+        type = types.listOf types.string;
+        default = ["root"];
+        description = lib.mdDoc "A list of users allowed to access the ifp dbus interface.";
+      };
+
+      dyndns = {
+        enable = mkOption {
+          type = types.bool;
+          default = true;
+          description = lib.mdDoc "Whether to enable FreeIPA automatic hostname updates.";
+        };
+
+        interface = mkOption {
+          type = types.str;
+          example = "eth0";
+          default = "*";
+          description = lib.mdDoc "Network interface to perform hostname updates through.";
+        };
+      };
+
+      chromiumSupport = mkOption {
+        type = types.bool;
+        default = true;
+        description = lib.mdDoc "Whether to whitelist the FreeIPA domain in Chromium.";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = !config.krb5.enable;
+        message = "krb5 must be disabled through `krb5.enable` for FreeIPA integration to work.";
+      }
+      {
+        assertion = !config.users.ldap.enable;
+        message = "ldap must be disabled through `users.ldap.enable` for FreeIPA integration to work.";
+      }
+    ];
+
+    environment.systemPackages = with pkgs; [krb5Full freeipa];
+
+    environment.etc = {
+      "ipa/default.conf".text = ''
+        [global]
+        basedn = ${cfg.basedn}
+        realm = ${cfg.realm}
+        domain = ${cfg.domain}
+        server = ${cfg.server}
+        host = ${config.networking.hostName}
+        xmlrpc_uri = https://${cfg.server}/ipa/xml
+        enable_ra = True
+      '';
+
+      "ipa/nssdb".source = nssDb;
+
+      "krb5.conf".text = ''
+        [libdefaults]
+         default_realm = ${cfg.realm}
+         dns_lookup_realm = false
+         dns_lookup_kdc = true
+         rdns = false
+         ticket_lifetime = 24h
+         forwardable = true
+         udp_preference_limit = 0
+
+        [realms]
+         ${cfg.realm} = {
+          kdc = ${cfg.server}:88
+          master_kdc = ${cfg.server}:88
+          admin_server = ${cfg.server}:749
+          default_domain = ${cfg.domain}
+          pkinit_anchors = FILE:/etc/ipa/ca.crt
+        }
+
+        [domain_realm]
+         .${cfg.domain} = ${cfg.realm}
+         ${cfg.domain} = ${cfg.realm}
+         ${cfg.server} = ${cfg.realm}
+
+        [dbmodules]
+          ${cfg.realm} = {
+            db_library = ${pkgs.freeipa}/lib/krb5/plugins/kdb/ipadb.so
+          }
+      '';
+
+      "openldap/ldap.conf".source = ldapConf;
+    };
+
+    environment.etc."chromium/policies/managed/freeipa.json" = mkIf cfg.chromiumSupport {
+      text = ''
+        { "AuthServerWhitelist": "*.${cfg.domain}" }
+      '';
+    };
+
+    system.activationScripts.ipa = stringAfter ["etc"] ''
+      # libcurl requires a hard copy of the certificate
+      if ! ${pkgs.diffutils}/bin/diff ${cfg.certificate} /etc/ipa/ca.crt > /dev/null 2>&1; then
+        rm -f /etc/ipa/ca.crt
+        cp ${cfg.certificate} /etc/ipa/ca.crt
+      fi
+
+      if [ ! -f /etc/krb5.keytab ]; then
+        cat <<EOF
+
+          In order to complete FreeIPA integration, please join the domain by completing the following steps:
+          1. Authenticate as an IPA user authorized to join new hosts, e.g. kinit admin@${cfg.realm}
+          2. Join the domain and obtain the keytab file: ipa-join
+          3. Install the keytab file: sudo install -m 600 krb5.keytab /etc/
+          4. Restart sssd systemd service: sudo systemctl restart sssd
+
+      EOF
+      fi
+    '';
+
+    services.sssd.config = ''
+      [domain/${cfg.domain}]
+      id_provider = ipa
+      auth_provider = ipa
+      access_provider = ipa
+      chpass_provider = ipa
+
+      ipa_domain = ${cfg.domain}
+      ipa_server = _srv_, ${cfg.server}
+      ipa_hostname = ${config.networking.hostName}.${cfg.domain}
+
+      cache_credentials = ${pyBool cfg.cacheCredentials}
+      krb5_store_password_if_offline = ${pyBool cfg.offlinePasswords}
+      ${optionalString ((toLower cfg.domain) != (toLower cfg.realm))
+        "krb5_realm = ${cfg.realm}"}
+
+      dyndns_update = ${pyBool cfg.dyndns.enable}
+      dyndns_iface = ${cfg.dyndns.interface}
+
+      ldap_tls_cacert = /etc/ipa/ca.crt
+      ldap_user_extra_attrs = mail:mail, sn:sn, givenname:givenname, telephoneNumber:telephoneNumber, lock:nsaccountlock
+
+      [sssd]
+      debug_level = 65510
+      services = nss, sudo, pam, ssh, ifp
+      domains = ${cfg.domain}
+
+      [nss]
+      homedir_substring = /home
+
+      [pam]
+      pam_pwd_expiration_warning = 3
+      pam_verbosity = 3
+
+      [sudo]
+      debug_level = 65510
+
+      [autofs]
+
+      [ssh]
+
+      [pac]
+
+      [ifp]
+      user_attributes = +mail, +telephoneNumber, +givenname, +sn, +lock
+      allowed_uids = ${concatStringsSep ", " cfg.ifpAllowedUids}
+    '';
+
+    services.ntp.servers = singleton cfg.server;
+    services.sssd.enable = true;
+    services.ntp.enable = true;
+
+    security.pki.certificateFiles = singleton cfg.certificate;
+  };
+}