Merge ~lloydwaltersj/maas:interface-name into maas:master

[Jack Lloyd-Walters]

sanitise domain names

modify regex to better sanitise domain names
introduce slightly more verbose error message for domain names.

[MAAS Lander (maas-lander)]

UNIT TESTS
-b interface-name lp:~lloydwaltersj/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: FAILED
LOG: http://maas-ci.internal:8080/job/maas/job/branch-tester/13170/console
COMMIT: e55e431f76cc7140af14d40f82a9de1a781d94e9

review: Needs Fixing

[MAAS Lander (maas-lander)]

UNIT TESTS
-b interface-name lp:~lloydwaltersj/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: FAILED
LOG: http://maas-ci.internal:8080/job/maas/job/branch-tester/13171/console
COMMIT: f89fd2bc4e8085762f7be3e0cf8ee072e4cd3a5f

review: Needs Fixing

119be40... by Jack Lloyd-Walters on 2022-07-06

actually fix merge conflict this time

[MAAS Lander (maas-lander)]

UNIT TESTS
-b interface-name lp:~lloydwaltersj/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: 119be4037c471e7c6a494c0107a33864e0a793c4

review: Approve

[Alexsander de Souza (alexsander-souza)]

+1

review: Approve

diff --git a/src/maasserver/models/domain.py b/src/maasserver/models/domain.py
index f3c1d71..a793e01 100644
--- a/src/maasserver/models/domain.py
+++ b/src/maasserver/models/domain.py
@@ -30,17 +30,24 @@ from maasserver.utils.orm import MAASQueriesMixin
 
 # Labels are at most 63 octets long, and a name can be many of them.
 LABEL = r"[a-zA-Z0-9]([-a-zA-Z0-9]{0,62}[a-zA-Z0-9]){0,1}"
-NAMESPEC = rf"({LABEL}.)*{LABEL}.?"
+NAMESPEC = rf"({LABEL}[.])*{LABEL}[.]?"
 
 
 def validate_domain_name(value):
     """Django validator: `value` must be a valid DNS Zone name."""
-    namespec = re.compile("^%s$" % NAMESPEC)
-    if not namespec.search(value) or len(value) > 255:
-        raise ValidationError("Invalid domain name: %s." % value)
+    namespec = re.compile(f"^{NAMESPEC}$")
+    if len(value) > 255:
+        raise ValidationError(
+            "Domain name length cannot exceed 255 characters."
+        )
+    if not namespec.match(value):
+        disallowed_chars = re.sub("[a-zA-Z0-9-.]*", "", value)
+        if disallowed_chars:
+            raise ValidationError("Domain name contains invalid characters.")
+        raise ValidationError(f"Invalid domain name: {value}.")
     if value == Config.objects.get_config("maas_internal_domain"):
         raise ValidationError(
-            "Domain name cannot duplicate maas internal domain name"
+            "Domain name cannot duplicate maas internal domain name."
         )