introduce firewall stage (#61)

as described in lorax documentation, we need to support raw
ports/protocols and services as defined by firewalld:
https://weldr.io/lorax/lorax-composer.html#customizations-firewall

stages/org.osbuild.firewall

@@ -0,0 +1,31 @@
+#!/usr/bin/python3
+
+import json
+import subprocess
+import sys
+
+
+def main(tree, options):
+    # Takes a list of <port|application protocol>:<transport protocol> pairs
+    ports = options["ports"]
+    # These must be defined for firewalld. It has a set of pre-defined services here: /usr/lib/firewalld/services/, but
+    # you can also define you own XML files in /etc/firewalld.
+    enabled_services = options["enabled_services"]
+    disabled_services = options["disabled_services"]
+
+    # firewall-offline-cmd does not implement --root option so we must chroot it
+    subprocess.run(["chroot",
+                    tree,
+                    "firewall-offline-cmd"] +
+                   list(map(lambda x: f"--port={x}", ports)) +
+                   list(map(lambda x: f"--service={x}", enabled_services)) +
+                   list(map(lambda x: f"--remove-service={x}", disabled_services)),
+                   check=True)
+
+    return 0
+
+
+if __name__ == '__main__':
+    args = json.load(sys.stdin)
+    r = main(args["tree"], args["options"])
+    sys.exit(r)

test/firewall-test.json

@@ -0,0 +1,34 @@
+{
+  "name": "Example Image",
+  "stages": [
+    {
+      "name": "org.osbuild.dnf",
+      "options": {
+        "releasever": "30",
+        "repos": {
+          "fedora": {
+            "name": "Fedora",
+            "metalink": "https://mirrors.fedoraproject.org/metalink?repo=fedora-$releasever&arch=$basearch",
+            "gpgkey": "file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$releasever-$basearch"
+          }
+        },
+        "packages": ["@Core", "firewalld"]
+	}
+    },
+    {
+      "name": "org.osbuild.firewall",
+      "options": {
+        "ports": ["53:tcp", "88:udp"],
+        "enabled_services": ["http", "ftp"],
+        "disabled_services": ["telnet"]
+      }
+    }
+  ],
+  "assembler": {
+    "name": "org.osbuild.tar",
+    "options": {
+      "filename": "firewall-output.tar.xz",
+      "compression": "xz"
+    }
+  }
+}

test/run-tests.py

@@ -70,14 +70,34 @@ def build_timezone_image():
     run_osbuild(rel_path("timezone-test.json"))
 
 
-def test_timezone():
+def build_firewall_image():
+    run_osbuild(rel_path("firewall-test.json"))
+
+
+def extract_to_tempdir(image_file):
     extract_dir = tempfile.mkdtemp(prefix="osbuild-")
-    subprocess.run(["tar", "xf", OUTPUT_DIR + "/timezone-output.tar.xz"], cwd=extract_dir, check=True)
+    subprocess.run(["tar", "xf", OUTPUT_DIR + image_file], cwd=extract_dir, check=True)
+    return extract_dir
+
+
+def test_timezone():
+    extract_dir = extract_to_tempdir("timezone-output.tar.xz")
     ls = subprocess.run(["ls", "-l", "etc/localtime"], cwd=extract_dir, check=True, stdout=subprocess.PIPE)
     ls_output = ls.stdout.decode("utf-8")
     assert "Europe/Prague" in ls_output
 
 
+def test_firewall():
+    extract_dir = extract_to_tempdir("firewall-output.tar.xz")
+    cat = subprocess.run(["cat", "etc/firewalld/zones/public.xml"], cwd=extract_dir, check=True, stdout=subprocess.PIPE)
+    cat_output = cat.stdout.decode("utf-8")
+    assert 'service name="http"' in cat_output
+    assert 'service name="ftp"' in cat_output
+    assert 'service name="telnet"' not in cat_output
+    assert 'port port="53" protocol="tcp"' in cat_output
+    assert 'port port="88" protocol="udp"' in cat_output
+
+
 def evaluate_test(test):
     try:
         test()
@@ -98,3 +118,5 @@ if __name__ == '__main__':
     build_timezone_image()
     evaluate_test(test_timezone)
 
+    build_firewall_image()
+    evaluate_test(test_firewall)