@@ -169,8 +169,8 @@ The following exceptions are raised as appropriate:
    A subclass of :exc:`HTTPException`.  Raised if a server responds with a HTTP
    status code that we don't understand.
 
-The constants defined in this module are:
 
+The constants defined in this module are:
 
 .. data:: HTTP_PORT
 
 
@@ -286,10 +286,10 @@ Certificate handling
    Verify that *cert* (in decoded format as returned by
    :meth:`SSLSocket.getpeercert`) matches the given *hostname*.  The rules
    applied are those for checking the identity of HTTPS servers as outlined
-   in :rfc:`2818`, except that IP addresses are not currently supported.
-   In addition to HTTPS, this function should be suitable for checking the
-   identity of servers in various SSL-based protocols such as FTPS, IMAPS,
-   POPS and others.
+   in :rfc:`2818` and :rfc:`6125`, except that IP addresses are not currently
+   supported. In addition to HTTPS, this function should be suitable for
+   checking the identity of servers in various SSL-based protocols such as
+   FTPS, IMAPS, POPS and others.
 
    :exc:`CertificateError` is raised on failure. On success, the function
    returns nothing::
@@ -304,6 +304,13 @@ Certificate handling
 
    .. versionadded:: 3.2
 
+   .. versionchanged:: 3.3.3
+      The function now follows :rfc:`6125`, section 6.4.3 and does neither
+      match multiple wildcards (e.g. ``*.*.com`` or ``*a*.example.org``) nor
+      a wildcard inside an internationalized domain names (IDN) fragment.
+      IDN A-labels such as ``www*.xn--pthon-kva.org`` are still supported,
+      but ``x*.python.org`` no longer matches ``xn--tda.python.org``.
+
 .. function:: cert_time_to_seconds(timestring)
 
    Returns a floating-point value containing a normal seconds-after-the-epoch
 
@@ -214,6 +214,8 @@
 
 # maximal line length when calling readline().
 _MAXLINE = 65536
+_MAXHEADERS = 100
+
 
 class HTTPMessage(email.message.Message):
     # XXX The only usage of this method is in
@@ -261,6 +263,8 @@ def parse_headers(fp, _class=HTTPMessage):
         if len(line) > _MAXLINE:
             raise LineTooLong("header line")
         headers.append(line)
+        if len(headers) > _MAXHEADERS:
+            raise HTTPException("got more than %d headers" % _MAXHEADERS)
         if line in (b'\r\n', b'\n', b''):
             break
     hstring = b''.join(headers).decode('iso-8859-1')
 
@@ -43,6 +43,15 @@
 IMAP4_SSL_PORT = 993
 AllowedVersions = ('IMAP4REV1', 'IMAP4')        # Most recent first
 
+# Maximal line length when calling readline(). This is to prevent
+# reading arbitrary length lines. RFC 3501 and 2060 (IMAP 4rev1)
+# don't specify a line length. RFC 2683 however suggests limiting client
+# command lines to 1000 octets and server command lines to 8000 octets.
+# We have selected 10000 for some extra margin and since that is supposedly
+# also what UW and Panda IMAP does.
+_MAXLINE = 10000
+
+
 #       Commands
 
 Commands = {
@@ -256,7 +265,10 @@ def read(self, size):
 
     def readline(self):
         """Read line from remote."""
-        return self.file.readline()
+        line = self.file.readline(_MAXLINE + 1)
+        if len(line) > _MAXLINE:
+            raise self.error("got more than %d bytes" % _MAXLINE)
+        return line
 
 
     def send(self, data):
 
@@ -85,6 +85,13 @@
            "decode_header",
            ]
 
+# maximal line length when calling readline(). This is to prevent
+# reading arbitrary lenght lines. RFC 3977 limits NNTP line length to
+# 512 characters, including CRLF. We have selected 2048 just to be on
+# the safe side.
+_MAXLINE = 2048
+
+
 # Exceptions raised when an error or invalid response is received
 class NNTPError(Exception):
     """Base class for all nntplib exceptions"""
@@ -424,7 +431,9 @@ def _getline(self, strip_crlf=True):
         """Internal: return one line from the server, stripping _CRLF.
         Raise EOFError if the connection is closed.
         Returns a bytes object."""
-        line = self.file.readline()
+        line = self.file.readline(_MAXLINE +1)
+        if len(line) > _MAXLINE:
+            raise NNTPDataError('line too long')
         if self.debugging > 1:
             print('*get*', repr(line))
         if not line: raise EOFError
 
@@ -40,6 +40,12 @@ class error_proto(Exception): pass
 LF = b'\n'
 CRLF = CR+LF
 
+# maximal line length when calling readline(). This is to prevent
+# reading arbitrary lenght lines. RFC 1939 limits POP3 line length to
+# 512 characters, including CRLF. We have selected 2048 just to be on
+# the safe side.
+_MAXLINE = 2048
+
 
 class POP3:
 
@@ -118,7 +124,10 @@ def _putcmd(self, line):
     # Raise error_proto('-ERR EOF') if the connection is closed.
 
     def _getline(self):
-        line = self.file.readline()
+        line = self.file.readline(_MAXLINE + 1)
+        if len(line) > _MAXLINE:
+            raise error_proto('line too long')
+
         if self._debugging > 1: print('*get*', repr(line))
         if not line: raise error_proto('-ERR EOF')
         octets = len(line)
 
@@ -166,31 +166,59 @@ class CertificateError(ValueError):
     pass
 
 
-def _dnsname_to_pat(dn, max_wildcards=1):
+def _dnsname_match(dn, hostname, max_wildcards=1):
+    """Matching according to RFC 6125, section 6.4.3
+
+    http://tools.ietf.org/html/rfc6125#section-6.4.3
+    """
     pats = []
-    for frag in dn.split(r'.'):
-        if frag.count('*') > max_wildcards:
-            # Issue #17980: avoid denials of service by refusing more
-            # than one wildcard per fragment.  A survey of established
-            # policy among SSL implementations showed it to be a
-            # reasonable choice.
-            raise CertificateError(
-                "too many wildcards in certificate DNS name: " + repr(dn))
-        if frag == '*':
-            # When '*' is a fragment by itself, it matches a non-empty dotless
-            # fragment.
-            pats.append('[^.]+')
-        else:
-            # Otherwise, '*' matches any dotless fragment.
-            frag = re.escape(frag)
-            pats.append(frag.replace(r'\*', '[^.]*'))
-    return re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
+    if not dn:
+        return False
+
+    leftmost, *remainder = dn.split(r'.')
+
+    wildcards = leftmost.count('*')
+    if wildcards > max_wildcards:
+        # Issue #17980: avoid denials of service by refusing more
+        # than one wildcard per fragment.  A survery of established
+        # policy among SSL implementations showed it to be a
+        # reasonable choice.
+        raise CertificateError(
+            "too many wildcards in certificate DNS name: " + repr(dn))
+
+    # speed up common case w/o wildcards
+    if not wildcards:
+        return dn.lower() == hostname.lower()
+
+    # RFC 6125, section 6.4.3, subitem 1.
+    # The client SHOULD NOT attempt to match a presented identifier in which
+    # the wildcard character comprises a label other than the left-most label.
+    if leftmost == '*':
+        # When '*' is a fragment by itself, it matches a non-empty dotless
+        # fragment.
+        pats.append('[^.]+')
+    elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
+        # RFC 6125, section 6.4.3, subitem 3.
+        # The client SHOULD NOT attempt to match a presented identifier
+        # where the wildcard character is embedded within an A-label or
+        # U-label of an internationalized domain name.
+        pats.append(re.escape(leftmost))
+    else:
+        # Otherwise, '*' matches any dotless string, e.g. www*
+        pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
+
+    # add the remaining fragments, ignore any wildcards
+    for frag in remainder:
+        pats.append(re.escape(frag))
+
+    pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
+    return pat.match(hostname)
 
 
 def match_hostname(cert, hostname):
     """Verify that *cert* (in decoded format as returned by
-    SSLSocket.getpeercert()) matches the *hostname*.  RFC 2818 rules
-    are mostly followed, but IP addresses are not accepted for *hostname*.
+    SSLSocket.getpeercert()) matches the *hostname*.  RFC 2818 and RFC 6125
+    rules are followed, but IP addresses are not accepted for *hostname*.
 
     CertificateError is raised on failure. On success, the function
     returns nothing.
@@ -201,7 +229,7 @@ def match_hostname(cert, hostname):
     san = cert.get('subjectAltName', ())
     for key, value in san:
         if key == 'DNS':
-            if _dnsname_to_pat(value).match(hostname):
+            if _dnsname_match(value, hostname):
                 return
             dnsnames.append(value)
     if not dnsnames:
@@ -212,7 +240,7 @@ def match_hostname(cert, hostname):
                 # XXX according to RFC 2818, the most specific Common Name
                 # must be used.
                 if key == 'commonName':
-                    if _dnsname_to_pat(value).match(hostname):
+                    if _dnsname_match(value, hostname):
                         return
                     dnsnames.append(value)
     if len(dnsnames) > 1:
 
@@ -347,6 +347,15 @@ def test_readinto_head(self):
             self.fail("Did not expect response from HEAD request")
         self.assertEqual(bytes(b), b'\x00'*5)
 
+    def test_too_many_headers(self):
+        headers = '\r\n'.join('Header%d: foo' % i
+                              for i in range(client._MAXHEADERS + 1)) + '\r\n'
+        text = ('HTTP/1.1 200 OK\r\n' + headers)
+        s = FakeSocket(text)
+        r = client.HTTPResponse(s)
+        self.assertRaisesRegex(client.HTTPException,
+                               r"got more than \d+ headers", r.begin)
+
     def test_send_file(self):
         expected = (b'GET /foo HTTP/1.1\r\nHost: example.com\r\n'
                     b'Accept-Encoding: identity\r\nContent-Length:')
 
@@ -325,6 +325,17 @@ def cmd_AUTHENTICATE(self, tag, args):
             self.assertEqual(ret, "OK")
 
 
+    def test_linetoolong(self):
+        class TooLongHandler(SimpleIMAPHandler):
+            def handle(self):
+                # Send a very long response line
+                self.wfile.write(b'* OK ' + imaplib._MAXLINE*b'x' + b'\r\n')
+
+        with self.reaped_server(TooLongHandler) as server:
+            self.assertRaises(imaplib.IMAP4.error,
+                              self.imap_class, *server.server_address)
+
+
 class ThreadedNetworkedTests(BaseThreadedNetworkedTests):
 
     server_class = socketserver.TCPServer
 
@@ -584,6 +584,11 @@ def handle_NEWNEWS(self, group, date_str, time_str):
                 <a4929a40-6328-491a-aaaf-cb79ed7309a2@q2g2000vbk.googlegroups.com>
                 <f30c0419-f549-4218-848f-d7d0131da931@y3g2000vbm.googlegroups.com>
                 .""")
+        elif (group == 'comp.lang.python' and
+              date_str in ('20100101', '100101') and
+              time_str == '090000'):
+            self.push_lit('too long line' * 3000 +
+                          '\n.')
         else:
             self.push_lit("""\
                 230 An empty list of newsarticles follows
@@ -1179,6 +1184,11 @@ def test_ihave(self):
         self.assertEqual(cm.exception.response,
                          "435 Article not wanted")
 
+    def test_too_long_lines(self):
+        dt = datetime.datetime(2010, 1, 1, 9, 0, 0)
+        self.assertRaises(nntplib.NNTPDataError,
+                          self.server.newnews, "comp.lang.python", dt)
+
 
 class NNTPv1Tests(NNTPv1v2TestsMixin, MockedNNTPTestsMixin, unittest.TestCase):
     """Tests an NNTP v1 server (no capabilities)."""