Improve hostname and domain name validation

DNS plugin did not check DNS zone and DNS record validity and
user was thus able to create domains like "foo bar" or other
invalid DNS labels which would really confuse both user and
bind-dyndb-ldap plugin.

This patch at first consolidates hostname/domain name validators
so that they use common functions and we don't have regular
expressions and other checks defined in several places. These
new cleaned validators are then used for zone/record name
validation.

https://fedorahosted.org/freeipa/ticket/2384

ipalib/util.py

@@ -213,6 +213,36 @@ def normalize_zonemgr(zonemgr):
 
     return zonemgr
 
+def validate_dns_label(dns_label, allow_underscore=False):
+    label_chars = r'a-z0-9'
+    underscore_err_msg = ''
+    if allow_underscore:
+        label_chars += "_"
+        underscore_err_msg = u' _,'
+    label_regex = r'^[%(chars)s]([%(chars)s-]?[%(chars)s])*$' % dict(chars=label_chars)
+    regex = re.compile(label_regex, re.IGNORECASE)
+
+    if len(dns_label) > 63:
+        raise ValueError(_('DNS label cannot be longer that 63 characters'))
+
+    if not regex.match(dns_label):
+        raise ValueError(_('only letters, numbers,%(underscore)s and - are allowed. ' \
+                           '- must not be the DNS label character') \
+                           % dict(underscore=underscore_err_msg))
+
+def validate_domain_name(domain_name):
+    if domain_name.endswith('.'):
+        domain_name = domain_name[:-1]
+
+    domain_name = domain_name.split(".")
+
+    # apply DNS name validator to every name part
+    map(lambda label:validate_dns_label(label), domain_name)
+
+    if not domain_name[-1].isalpha():
+        # see RFC 1123
+        raise ValueError(_('top level domain label must be alphabetic'))
+
 def validate_zonemgr(zonemgr):
     """ See RFC 1033, 1035 """
     regex_domain = re.compile(r'^[a-z0-9]([a-z0-9-]?[a-z0-9])*$', re.IGNORECASE)
@@ -252,8 +282,7 @@ def validate_zonemgr(zonemgr):
             if not regex_local_part.match(local_part):
                 raise ValueError(local_part_errmsg)
 
-    if not all(regex_domain.match(part) for part in domain.split(".")):
-        raise ValueError(_('domain name may only include letters, numbers, and -'))
+    validate_domain_name(domain)
 
 def validate_hostname(hostname, check_fqdn=True):
     """ See RFC 952, 1123
@@ -261,20 +290,18 @@ def validate_hostname(hostname, check_fqdn=True):
     :param hostname Checked value
     :param check_fqdn Check if hostname is fully qualified
     """
-    regex_name = re.compile(r'^[a-z0-9]([a-z0-9-]?[a-z0-9])*$', re.IGNORECASE)
-
     if len(hostname) > 255:
         raise ValueError(_('cannot be longer that 255 characters'))
 
     if hostname.endswith('.'):
         hostname = hostname[:-1]
 
-    if check_fqdn and '.' not in hostname:
-        raise ValueError(_('not fully qualified'))
-
-    if not all(regex_name.match(part) for part in hostname.split(".")):
-        raise ValueError(_('only letters, numbers, and - are allowed. ' \
-                           '- must not be the last name character'))
+    if '.' not in hostname:
+        if check_fqdn:
+            raise ValueError(_('not fully qualified'))
+        validate_dns_label(hostname)
+    else:
+        validate_domain_name(hostname)
 
 def validate_sshpubkey(ugettext, pubkey):
     try: