[DoT] Raise exception on error + tests coverage

Do not print error, instead raise an exception that need to be caught.
The calling method will then decide if the error should be displayed or
not.

homer.py

@@ -704,6 +704,15 @@ for ip in ip_set:
         error("\"%s\" not a name or an IP address" % url)
     except socket.gaierror:
         error("Could not resolve \"%s\"" % url)
+    except homer.ConnectionDOTException as e:
+        if not monitoring:
+            print(e, file=sys.stderr)
+            err = "Could not connect to \"%s\"" % url
+            if opts.connectTo is not None:
+                err += " on %s" % opts.connectTo
+            error(err)
+        else:
+            error(e)
     except (homer.ConnectionException, homer.DOHException) as e:
         error(e)
     if conn.dot and not conn.success:

homer/connection.py

+import sys
 import io
 import socket
 import signal
@@ -110,24 +111,35 @@ class ConnectionDOT(Connection):
 
         signal.signal(signal.SIGALRM, homer.exceptions.timeout_connection)
 
+        # contains a set of tuples ('ip address', 'error message')
+        errors = set()
+        i = 0
         for addrinfo in addrinfo_set:
-            if self.establish_session(addrinfo[0], addrinfo[1]):
-                self.success = True
-                break
+            # catch the raised exceptions and store them in the error set
+            # if that the last element of the loop raises an exception
+            # it will also be catched, but in this case we are sure we can not
+            # establish a connection therefore we raise an exception containing
+            # a string with all the errors
+            try:
+                self.establish_session(addrinfo[0], addrinfo[1])
+            except homer.ConnectionDOTException as e:
+                errors.add((addrinfo[0][0], str(e)))
                 if self.verbose and self.connect_to is None:
-                print("Could not connect to %s" % addrinfo[0][0])
-                print("Trying another IP address")
-
-        # we could not establish a connection
-        if not self.success:
+                    print(e, file=sys.stderr)
                 # we tried all the resolved IPs
+                if i == (len(addrinfo_set) - 1):
                     if self.verbose and self.connect_to is None:
                         print("No other IP address")
-
-            error = "Could not connect to \"%s\"" % self.server
-            if self.connect_to is not None:
-                error += " on %s" % self.connect_to
-            raise homer.ConnectionDOTException(error)
+                    # join all the errors into a single string
+                    err = ', '.join( "%s: %s" % (e[0], e[1]) for e in errors)
+                    raise homer.ConnectionDOTException(err)
+                if self.verbose and self.connect_to is None:
+                    print("Could not connect to %s" % addrinfo[0][0])
+                    print("Trying another IP address")
+            else:
+                self.success = True
+                break
+            i += 1
 
     def establish_session(self, addr, sock_family):
         """Return True if a TLS session is established."""
@@ -162,26 +174,16 @@ class ConnectionDOT(Connection):
             self.session.connect((addr))
             self.session.do_handshake()
         except homer.exceptions.TimeoutConnectionError:
-            if self.verbose:
-                print("Timeout")
-            return False
+            raise homer.ConnectionDOTException("Timeout")
         except OSError:
-            if self.verbose:
-                print("Cannot connect")
-            return False
+            raise homer.ConnectionDOTException("Cannot connect")
         except OpenSSL.SSL.SysCallError as e:
-            if self.verbose:
-                print("OpenSSL error: %s" % e.args[1], file=sys.stderr)
-            return False
+            raise homer.ConnectionDOTException("OpenSSL error: %s" % e.args[1])
         except OpenSSL.SSL.ZeroReturnError:
             # see #18
-            if self.verbose:
-                print("Error: The SSL connection has been closed (try with --nosni to avoid sending SNI ?)", file=sys.stderr)
-            return False
+            raise homer.ConnectionDOTException("Error: The SSL connection has been closed (try with --nosni to avoid sending SNI ?)")
         except OpenSSL.SSL.Error as e:
-            if self.verbose:
-                print("OpenSSL error: %s" % ', '.join(err[0][2] for err in e.args), file=sys.stderr)
-            return False
+            raise homer.ConnectionDOTException("OpenSSL error: %s" % ', '.join(err[0][2] for err in e.args))
 
         # RFC 7858, section 4.2 and appendix A
         self.cert = self.session.get_peer_certificate()
@@ -201,12 +203,10 @@ class ConnectionDOT(Connection):
             if self.key is None:
                 valid = homer.validate_hostname(self.check_name_cert, self.cert)
                 if not valid:
-                    error("Certificate error: \"%s\" is not in the certificate" % (self.check_name_cert), exit=False)
-                    return False
+                    raise homer.ConnectionDOTException("Certificate error: \"%s\" is not in the certificate" % (self.check_name_cert))
             else:
                 if key_string != self.key:
-                    error("Key error: expected \"%s\", got \"%s\"" % (self.key, key_string), exit=False)
-                    return False
+                    raise homer.ConnectionDOTException("Key error: expected \"%s\", got \"%s\"" % (self.key, key_string))
 
         # restore the timer
         signal.alarm(0)

tests.yaml

@@ -868,6 +868,20 @@ tests:
       stderr: ''
       partstdout: 'Cannot find'
 
+    - exe: './check_dot'
+      name: '[check_dot] Certificate error'
+      markers:
+          - 'dot'
+          - 'monitoring'
+          - 'exception'
+      args:
+          - '-H'
+          - 'doh.bortzmeyer.fr'
+          - '-n'
+          - 'dnsforum.bj'
+      retcode: 2
+      partstdout: 'certificate'
+
 
 ################################################################################
 
@@ -1054,6 +1068,20 @@ tests:
       stderr: ''
       partstdout: 'Cannot find'
 
+    - exe: './check_doh'
+      name: '[check_doh] Certificate error'
+      markers:
+          - 'doh'
+          - 'monitoring'
+          - 'exception'
+      args:
+          - '-H'
+          - 'dot.bortzmeyer.fr'
+          - '-n'
+          - 'dnsforum.bj'
+      retcode: 2
+      partstdout: 'certificate'
+
 ################################################################################
 
     - exe: './homer.py'