[fix] False positive on blacklist due to search in resovconf

data/hooks/diagnosis/24-mail.py

@@ -13,6 +13,7 @@ from moulinette.utils.filesystem import read_yaml
 from yunohost.diagnosis import Diagnoser
 from yunohost.domain import _get_maindomain, domain_list
 from yunohost.settings import settings_get
+from yunohost.utils.network import dig
 
 DEFAULT_DNS_BLACKLIST = "/usr/share/yunohost/other/dnsbl_list.yml"
 
@@ -155,26 +156,25 @@ class MailDiagnoser(Diagnoser):
                 if not blacklist[item_type]:
                     continue
 
-                # Determine if we are listed on this RBL
+                # Build the query for DNSBL
-                try:
                 subdomain = item
                 if item_type != "domain":
                     rev = dns.reversename.from_address(item)
                     subdomain = str(rev.split(3)[0])
                 query = subdomain + '.' + blacklist['dns_server']
-                    # TODO add timeout lifetime
+
-                    dns.resolver.query(query, "A")
+                # Do the DNS Query
-                except (dns.resolver.NXDOMAIN, dns.resolver.NoNameservers, dns.resolver.NoAnswer,
+                status, answers = dig(query, 'A')
-                dns.exception.Timeout):
+                if status != 'ok':
                     continue
 
                 # Try to get the reason
                 details = []
-                try:
+                status, answers = dig(query, 'TXT')
-                    reason = str(dns.resolver.query(query, "TXT")[0])
-                    details.append("diagnosis_mail_blacklist_reason")
-                except Exception:
                 reason = "-"
+                if status == 'ok':
+                    reason = ', '.join(answers)
+                    details.append("diagnosis_mail_blacklist_reason")
 
                 details.append("diagnosis_mail_blacklist_website")
 

src/yunohost/utils/network.py

@@ -21,6 +21,7 @@
 import os
 import re
 import logging
+import dns.resolver
 
 from moulinette.utils.network import download_text
 from moulinette.utils.process import check_output
@@ -84,6 +85,24 @@ def get_gateway():
     return addr.popitem()[1] if len(addr) == 1 else None
 
 
+def dig(qname, rdtype="A", timeout=5, resolvers=["127.0.0.1"], edns_size=1500):
+    """
+    Do a quick DNS request and avoid the "search" trap inside /etc/resolv.conf
+    """
+
+    resolver = dns.resolver.Resolver(configure=False)
+    resolver.use_edns(0, 0, edns_size)
+    resolver.nameservers = resolvers
+    resolver.timeout = timeout
+    try:
+        answers = resolver.query(qname, rdtype)
+    except (dns.resolver.NXDOMAIN, dns.resolver.NoNameservers, dns.resolver.NoAnswer,
+    dns.exception.Timeout) as e:
+        return ("nok", e.__class__.__name__, e)
+
+    return ("ok", [(answer.to_text(), answer) for answer in answers])
+
+
 def _extract_inet(string, skip_netmask=False, skip_loopback=True):
     """
     Extract IP addresses (v4 and/or v6) from a string limited to one