Update config form for hostnames and domainnames

- Make minimum length 1 for the fields.

- Write tests.

- Update description to reflect the new conditions.

plinth/modules/config/config.py

@@ -59,28 +59,39 @@ class TrimmedCharField(forms.CharField):
 
 class ConfigurationForm(forms.Form):
     """Main system configuration form"""
-    # We're more conservative than RFC 952 and RFC 1123
+    # See:
+    # https://tools.ietf.org/html/rfc952
+    # https://tools.ietf.org/html/rfc1035#section-2.3.1
+    # https://tools.ietf.org/html/rfc1123#section-2
+    # https://tools.ietf.org/html/rfc2181#section-11
     hostname = TrimmedCharField(
         label=ugettext_lazy('Hostname'),
         help_text=\
-        ugettext_lazy('Your hostname is the local name by which other machines '
+        ugettext_lazy('Hostname is the local name by which other machines on '
-                      'on your LAN can reach you. It must be alphanumeric, '
+                      'the local network reach your machine.  It must start '
-                      'start with an alphabet and must not be greater than 63 '
+                      'and end with an alphabet or a digit and have as '
-                      'characters in length.'),
+                      'interior characters only alphabets, digits and '
+                      'hyphens.  Total length must be 63 characters or less.'),
         validators=[
-            validators.RegexValidator(r'^[a-zA-Z][-a-zA-Z0-9]{,61}[a-zA-Z0-9]$',
+            validators.RegexValidator(
-                                      ugettext_lazy('Invalid hostname'))])
+                r'^[a-zA-Z0-9]([-a-zA-Z0-9]{,61}[a-zA-Z0-9])?$',
+                ugettext_lazy('Invalid hostname'))])
 
     domainname = TrimmedCharField(
         label=ugettext_lazy('Domain Name'),
         help_text=\
-        ugettext_lazy('Your domain name is the global name by which other '
+        ugettext_lazy('Domain name is the global name by which other machines '
-                      'machines on the Internet can reach you. It must consist '
+                      'on the Internet can reach you.  It must consist of '
-                      'of alphanumeric words separated by dots.'),
+                      'labels separated by dots.  Each label must start and '
+                      'end with an alphabet or a digit and have as interior '
+                      'characters only alphabets, digits and hyphens.  Length '
+                      'of each label must be 63 characters or less.  Total '
+                      'length of domain name must be 253 characters or less.'),
         required=False,
         validators=[
-            validators.RegexValidator(r'^[a-zA-Z][-a-zA-Z0-9.]*[a-zA-Z0-9]$',
+            validators.RegexValidator(
-                                      ugettext_lazy('Invalid domain name'))])
+                r'^[a-zA-Z0-9]([-a-zA-Z0-9.]*[a-zA-Z0-9])?$',
+                ugettext_lazy('Invalid domain name'))])
 
 
 def init():

plinth/modules/config/tests/test_config.py

@@ -0,0 +1,65 @@
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+Tests for config module.
+"""
+
+import unittest
+
+from ..config import ConfigurationForm
+
+
+class TestConfig(unittest.TestCase):
+    """Test cases for testing the config module."""
+    def test_hostname_field(self):
+        """Test that hostname field accepts only valid hostnames."""
+        valid_hostnames = [
+            'a', '0a', 'a0', 'AAA', '00', '0-0', 'example-hostname', 'example',
+            '012345678901234567890123456789012345678901234567890123456789012']
+        invalid_hostnames = [
+            '', '-', '-a', 'a-', '.a', 'a.', 'a.a', '?', 'a?a',
+            '0123456789012345678901234567890123456789012345678901234567890123']
+
+        for hostname in valid_hostnames:
+            form = ConfigurationForm({'hostname': hostname,
+                                      'domainname': 'example.com'})
+            self.assertTrue(form.is_valid())
+
+        for hostname in invalid_hostnames:
+            form = ConfigurationForm({'hostname': hostname,
+                                      'domainname': 'example.com'})
+            self.assertFalse(form.is_valid())
+
+    def test_domainname_field(self):
+        """Test that domainname field accepts only valid domainnames."""
+        valid_domainnames = [
+            '', 'a', '0a', 'a0', 'AAA', '00', '0-0', 'example-hostname',
+            'example', 'example.org', 'a.b.c.d', 'a-0.b-0.c-0',
+            '012345678901234567890123456789012345678901234567890123456789012']
+        invalid_domainnames = [
+            '-', '-a', 'a-', '.a', 'a.', '?', 'a?a']
+
+        for domainname in valid_domainnames:
+            form = ConfigurationForm({'hostname': 'example',
+                                      'domainname': domainname})
+            self.assertTrue(form.is_valid())
+
+        for domainname in invalid_domainnames:
+            form = ConfigurationForm({'hostname': 'example',
+                                      'domainname': domainname})
+            self.assertFalse(form.is_valid())