Issue 12139: add CCC command support to FTP_TLS class to revert the SSL connection back to clear-text.
diff --git a/Doc/library/ftplib.rst b/Doc/library/ftplib.rst
index f4205f4..087e200 100644
--- a/Doc/library/ftplib.rst
+++ b/Doc/library/ftplib.rst
@@ -426,6 +426,14 @@
Set up secure control connection by using TLS or SSL, depending on what specified in :meth:`ssl_version` attribute.
+.. method:: FTP_TLS.ccc()
+
+ Revert control channel back to plaintex. This can be useful to take
+ advantage of firewalls that know how to handle NAT with non-secure FTP
+ without opening fixed ports.
+
+ .. versionadded:: 3.3
+
.. method:: FTP_TLS.prot_p()
Set up secure data connection.
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index 4374d02..63f8b15 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -192,6 +192,17 @@
* :func:`~ssl.RAND_pseudo_bytes`: generate pseudo-random bytes.
+ftplib
+------
+
+The :class:`~ftplib.FTP_TLS` class now provides a new
+:func:`~ftplib.FTP_TLS.ccc` function to revert control channel back to
+plaintex. This can be useful to take advantage of firewalls that know how to
+handle NAT with non-secure FTP without opening fixed ports.
+
+(Patch submitted by Giampaolo Rodolà in :issue:`12139`.)
+
+
Optimizations
=============
diff --git a/Lib/ftplib.py b/Lib/ftplib.py
index d15a135..eaaa6fd 100644
--- a/Lib/ftplib.py
+++ b/Lib/ftplib.py
@@ -708,6 +708,14 @@
self.file = self.sock.makefile(mode='r', encoding=self.encoding)
return resp
+ def ccc(self):
+ '''Switch back to a clear-text control connection.'''
+ if not isinstance(self.sock, ssl.SSLSocket):
+ raise ValueError("not using TLS")
+ resp = self.voidcmd('CCC')
+ self.sock = self.sock.unwrap()
+ return resp
+
def prot_p(self):
'''Set up secure data connection.'''
# PROT defines whether or not the data channel is to be protected.
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index 78e0fb4..5734fd3 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -303,11 +303,11 @@
_ssl_closing = False
def secure_connection(self):
- self.del_channel()
socket = ssl.wrap_socket(self.socket, suppress_ragged_eofs=False,
certfile=CERTFILE, server_side=True,
do_handshake_on_connect=False,
ssl_version=ssl.PROTOCOL_SSLv23)
+ self.del_channel()
self.set_socket(socket)
self._ssl_accepting = True
@@ -342,7 +342,10 @@
# http://www.mail-archive.com/openssl-users@openssl.org/msg60710.html
pass
self._ssl_closing = False
- super(SSLConnection, self).close()
+ if getattr(self, '_ccc', False) == False:
+ super(SSLConnection, self).close()
+ else:
+ pass
def handle_read_event(self):
if self._ssl_accepting:
@@ -410,12 +413,18 @@
def __init__(self, conn):
DummyFTPHandler.__init__(self, conn)
self.secure_data_channel = False
+ self._ccc = False
def cmd_auth(self, line):
"""Set up secure control channel."""
self.push('234 AUTH TLS successful')
self.secure_connection()
+ def cmd_ccc(self, line):
+ self.push('220 Reverting back to clear-text')
+ self._ccc = True
+ self._do_ssl_shutdown()
+
def cmd_pbsz(self, line):
"""Negotiate size of buffer for secure data transfer.
For TLS/SSL the only valid value for the parameter is '0'.
@@ -872,6 +881,15 @@
self.assertIs(sock.context, ctx)
self.assertIsInstance(sock, ssl.SSLSocket)
+ def test_ccc(self):
+ self.assertRaises(ValueError, self.client.ccc)
+ self.client.login(secure=True)
+ self.assertIsInstance(self.client.sock, ssl.SSLSocket)
+ self.client.ccc()
+ self.assertRaises(ValueError, self.client.sock.unwrap)
+ self.client.sendcmd('noop')
+ self.client.quit()
+
class TestTimeouts(TestCase):