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Issue #4473: Add a POP3.stls() to switch a clear-text POP3 session into an encrypted POP3 session, on supported servers. 

Patch by Lorenzo Catucci.
This commit is contained in:
Antoine Pitrou 2012-11-23 20:13:48 +01:00
parent 25cee19beb
commit 8618d7457b
4 changed files with 176 additions and 39 deletions
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19
Doc/library/poplib.rst
View File

@ -13,8 +13,11 @@
--------------
This module defines a class, :class:`POP3`, which encapsulates a connection to a
POP3 server and implements the protocol as defined in :rfc:`1725`. The
:class:`POP3` class supports both the minimal and optional command sets.
POP3 server and implements the protocol as defined in :rfc:`1939`. The
:class:`POP3` class supports both the minimal and optional command sets from
:rfc:`1939`. The :class:`POP3` class also supports the `STLS` command introduced
in :rfc:`2595` to enable encrypted communication on an already established connection.
Additionally, this module provides a class :class:`POP3_SSL`, which provides
support for connecting to POP3 servers that use SSL as an underlying protocol
layer.
@ -184,6 +187,18 @@ An :class:`POP3` instance has the following methods:
the unique id for that message in the form ``'response mesgnum uid``, otherwise
result is list ``(response, ['mesgnum uid', ...], octets)``.
.. method:: POP3.stls(context=None)
Start a TLS session on the active connection as specified in :rfc:`2595`.
This is only allowed before user authentication
*context* parameter is a :class:`ssl.SSLContext` object which allows
bundling SSL configuration options, certificates and private keys into
a single (potentially long-lived) structure.
.. versionadded:: 3.4
Instances of :class:`POP3_SSL` have no additional methods. The interface of this
subclass is identical to its parent.

48
Lib/poplib.py
View File

@ -15,6 +15,12 @@ Based on the J. Myers POP3 draft, Jan. 96
import re, socket
try:
import ssl
HAVE_SSL = True
except ImportError:
HAVE_SSL = False
__all__ = ["POP3","error_proto"]
# Exception raised when an error or invalid response is received:
@ -56,6 +62,7 @@ class POP3:
TOP msg n top(msg, n)
UIDL [msg] uidl(msg = None)
CAPA capa()
STLS stls()
Raises one exception: 'error_proto'.
@ -82,6 +89,7 @@ class POP3:
timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
self.host = host
self.port = port
self._tls_established = False
self.sock = self._create_socket(timeout)
self.file = self.sock.makefile('rb')
self._debugging = 0
@ -352,21 +360,42 @@ class POP3:
raise error_proto('-ERR CAPA not supported by server')
return caps
try:
import ssl
except ImportError:
pass
else:
def stls(self, context=None):
"""Start a TLS session on the active connection as specified in RFC 2595.
context - a ssl.SSLContext
"""
if not HAVE_SSL:
raise error_proto('-ERR TLS support missing')
if self._tls_established:
raise error_proto('-ERR TLS session already established')
caps = self.capa()
if not 'STLS' in caps:
raise error_proto('-ERR STLS not supported by server')
if context is None:
context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
context.options |= ssl.OP_NO_SSLv2
resp = self._shortcmd('STLS')
self.sock = context.wrap_socket(self.sock)
self.file = self.sock.makefile('rb')
self._tls_established = True
return resp
if HAVE_SSL:
class POP3_SSL(POP3):
"""POP3 client class over SSL connection
Instantiate with: POP3_SSL(hostname, port=995, keyfile=None, certfile=None)
Instantiate with: POP3_SSL(hostname, port=995, keyfile=None, certfile=None,
context=None)
hostname - the hostname of the pop3 over ssl server
port - port number
keyfile - PEM formatted file that countains your private key
certfile - PEM formatted certificate chain file
context - a ssl.SSLContext
See the methods of the parent class POP3 for more documentation.
"""
@ -392,6 +421,13 @@ else:
sock = ssl.wrap_socket(sock, self.keyfile, self.certfile)
return sock
def stls(self, keyfile=None, certfile=None, context=None):
"""The method unconditionally raises an exception since the
STLS command doesn't make any sense on an already established
SSL/TLS session.
"""
raise error_proto('-ERR TLS session already established')
__all__.append("POP3_SSL")
if __name__ == "__main__":

145
Lib/test/test_poplib.py
View File

@ -18,6 +18,13 @@ threading = test_support.import_module('threading')
HOST = test_support.HOST
PORT = 0
SUPPORTS_SSL = False
if hasattr(poplib, 'POP3_SSL'):
import ssl
SUPPORTS_SSL = True
CERTFILE = os.path.join(os.path.dirname(__file__) or os.curdir, "keycert.pem")
# the dummy data returned by server when LIST and RETR commands are issued
LIST_RESP = b'1 1\r\n2 2\r\n3 3\r\n4 4\r\n5 5\r\n.\r\n'
RETR_RESP = b"""From: postmaster@python.org\
@ -40,6 +47,8 @@ class DummyPOP3Handler(asynchat.async_chat):
self.set_terminator(b"\r\n")
self.in_buffer = []
self.push('+OK dummy pop3 server ready. <timestamp>')
self.tls_active = False
self.tls_starting = False
def collect_incoming_data(self, data):
self.in_buffer.append(data)
@ -114,16 +123,65 @@ class DummyPOP3Handler(asynchat.async_chat):
self.push('+OK closing.')
self.close_when_done()
def _get_capas(self):
_capas = dict(self.CAPAS)
if not self.tls_active and SUPPORTS_SSL:
_capas['STLS'] = []
return _capas
def cmd_capa(self, arg):
self.push('+OK Capability list follows')
if self.CAPAS:
for cap, params in self.CAPAS.items():
if self._get_capas():
for cap, params in self._get_capas().items():
_ln = [cap]
if params:
_ln.extend(params)
self.push(' '.join(_ln))
self.push('.')
if SUPPORTS_SSL:
def cmd_stls(self, arg):
if self.tls_active is False:
self.push('+OK Begin TLS negotiation')
tls_sock = ssl.wrap_socket(self.socket, certfile=CERTFILE,
server_side=True,
do_handshake_on_connect=False,
suppress_ragged_eofs=False)
self.del_channel()
self.set_socket(tls_sock)
self.tls_active = True
self.tls_starting = True
self.in_buffer = []
self._do_tls_handshake()
else:
self.push('-ERR Command not permitted when TLS active')
def _do_tls_handshake(self):
try:
self.socket.do_handshake()
except ssl.SSLError as err:
if err.args[0] in (ssl.SSL_ERROR_WANT_READ,
ssl.SSL_ERROR_WANT_WRITE):
return
elif err.args[0] == ssl.SSL_ERROR_EOF:
return self.handle_close()
raise
except socket.error as err:
if err.args[0] == errno.ECONNABORTED:
return self.handle_close()
else:
self.tls_active = True
self.tls_starting = False
def handle_read(self):
if self.tls_starting:
self._do_tls_handshake()
else:
try:
asynchat.async_chat.handle_read(self)
except ssl.SSLEOFError:
self.handle_close()
class DummyPOP3Server(asyncore.dispatcher, threading.Thread):
@ -254,13 +312,25 @@ class TestPOP3Class(TestCase):
self.assertIsNone(self.client.sock)
self.assertIsNone(self.client.file)
if SUPPORTS_SSL:
SUPPORTS_SSL = False
if hasattr(poplib, 'POP3_SSL'):
import ssl
def test_stls_capa(self):
capa = self.client.capa()
self.assertTrue('STLS' in capa.keys())
SUPPORTS_SSL = True
CERTFILE = os.path.join(os.path.dirname(__file__) or os.curdir, "keycert.pem")
def test_stls(self):
expected = b'+OK Begin TLS negotiation'
resp = self.client.stls()
self.assertEqual(resp, expected)
def test_stls_context(self):
expected = b'+OK Begin TLS negotiation'
ctx = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
resp = self.client.stls(context=ctx)
self.assertEqual(resp, expected)
if SUPPORTS_SSL:
class DummyPOP3_SSLHandler(DummyPOP3Handler):
@ -272,34 +342,13 @@ if hasattr(poplib, 'POP3_SSL'):
self.del_channel()
self.set_socket(ssl_socket)
# Must try handshake before calling push()
self._ssl_accepting = True
self._do_ssl_handshake()
self.tls_active = True
self.tls_starting = True
self._do_tls_handshake()
self.set_terminator(b"\r\n")
self.in_buffer = []
self.push('+OK dummy pop3 server ready. <timestamp>')
def _do_ssl_handshake(self):
try:
self.socket.do_handshake()
except ssl.SSLError as err:
if err.args[0] in (ssl.SSL_ERROR_WANT_READ,
ssl.SSL_ERROR_WANT_WRITE):
return
elif err.args[0] == ssl.SSL_ERROR_EOF:
return self.handle_close()
raise
except socket.error as err:
if err.args[0] == errno.ECONNABORTED:
return self.handle_close()
else:
self._ssl_accepting = False
def handle_read(self):
if self._ssl_accepting:
self._do_ssl_handshake()
else:
DummyPOP3Handler.handle_read(self)
class TestPOP3_SSLClass(TestPOP3Class):
# repeat previous tests by using poplib.POP3_SSL
@ -330,6 +379,39 @@ if hasattr(poplib, 'POP3_SSL'):
self.assertIs(self.client.sock.context, ctx)
self.assertTrue(self.client.noop().startswith(b'+OK'))
def test_stls(self):
self.assertRaises(poplib.error_proto, self.client.stls)
test_stls_context = test_stls
def test_stls_capa(self):
capa = self.client.capa()
self.assertFalse('STLS' in capa.keys())
class TestPOP3_TLSClass(TestPOP3Class):
# repeat previous tests by using poplib.POP3.stls()
def setUp(self):
self.server = DummyPOP3Server((HOST, PORT))
self.server.start()
self.client = poplib.POP3(self.server.host, self.server.port, timeout=3)
self.client.stls()
def tearDown(self):
if self.client.file is not None and self.client.sock is not None:
self.client.quit()
self.server.stop()
def test_stls(self):
self.assertRaises(poplib.error_proto, self.client.stls)
test_stls_context = test_stls
def test_stls_capa(self):
capa = self.client.capa()
self.assertFalse(b'STLS' in capa.keys())
class TestTimeouts(TestCase):
@ -389,6 +471,7 @@ def test_main():
tests = [TestPOP3Class, TestTimeouts]
if SUPPORTS_SSL:
tests.append(TestPOP3_SSLClass)
tests.append(TestPOP3_TLSClass)
thread_info = test_support.threading_setup()
try:
test_support.run_unittest(*tests)

3
Misc/NEWS
View File

@ -138,6 +138,9 @@ Core and Builtins
Library
-------
- Issue #4473: Add a POP3.stls() to switch a clear-text POP3 session into
an encrypted POP3 session, on supported servers. Patch by Lorenzo Catucci.
- Issue #4473: Add a POP3.capa() method to query the capabilities advertised
by the POP3 server. Patch by Lorenzo Catucci.