interface: fix check_host_name() pattern matching

The existing pattern matching code:

    val.find('*.') == 0 and name.find(val[1:]) + len(val[1:]) == len(name)

will return True in the following case:

   val = '*.host.com'
   name = 'blah.org'

since string.find() will return -1, len(val[1:]) == 9 and len(name) == 8.

lib/interface.py

@@ -119,30 +119,6 @@ class TcpInterface(threading.Thread):
             queue.put((self, {'method':method, 'params':params, 'result':result, 'id':_id}))
 
 
-    def check_host_name(self, peercert, name):
-        """Simple certificate/host name checker.  Returns True if the
-        certificate matches, False otherwise."""
-        # Check that the peer has supplied a certificate.
-        # None/{} is not acceptable.
-        if not peercert:
-            return False
-        if peercert.has_key("subjectAltName"):
-            for typ, val in peercert["subjectAltName"]:
-                if typ == "DNS"  and (val == name or (val.find('*.') == 0 and name.find(val[1:]) + len(val[1:]) == len(name))):
-                    return True
-        else:
-            # Only check the subject DN if there is no subject alternative
-            # name.
-            cn = None
-            for attr, val in peercert["subject"]:
-                # Use most-specific (last) commonName attribute.
-                if attr == "commonName":
-                    cn = val
-            if cn is not None:
-                return (cn == name or (cn.find('*.') == 0 and name.find(cn[1:]) + len(cn[1:]) == len(name)))
-        return False
-
-
     def get_simple_socket(self):
         try:
             l = socket.getaddrinfo(self.host, self.port, socket.AF_UNSPEC, socket.SOCK_STREAM)
@@ -175,7 +151,7 @@ class TcpInterface(threading.Thread):
                     s = ssl.wrap_socket(s, ssl_version=ssl.PROTOCOL_SSLv23, cert_reqs=ssl.CERT_REQUIRED, ca_certs=ca_path, do_handshake_on_connect=True)
                 except ssl.SSLError, e:
                     s = None
-                if s and self.check_host_name(s.getpeercert(), self.host):
+                if s and check_host_name(s.getpeercert(), self.host):
                     self.print_error("SSL certificate signed by CA")
                     return s
 
@@ -334,6 +310,35 @@ class TcpInterface(threading.Thread):
         self.response_queue.put((self, None))
 
 
+def _match_hostname(name, val):
+    if val == name:
+        return True
+
+    return val.startswith('*.') and name.endswith(val[1:])
+
+
+def check_host_name(peercert, name):
+    """Simple certificate/host name checker.  Returns True if the
+    certificate matches, False otherwise."""
+    # Check that the peer has supplied a certificate.
+    # None/{} is not acceptable.
+    if not peercert:
+        return False
+    if peercert.has_key("subjectAltName"):
+        for typ, val in peercert["subjectAltName"]:
+            if typ == "DNS" and _match_hostname(name, val):
+                return True
+    else:
+        # Only check the subject DN if there is no subject alternative
+        # name.
+        cn = None
+        for attr, val in peercert["subject"]:
+            # Use most-specific (last) commonName attribute.
+            if attr == "commonName":
+                cn = val
+        if cn is not None:
+            return _match_hostname(name, cn)
+    return False
 
 
 def check_cert(host, cert):