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diff --git a/Lib/ftplib.py b/Lib/ftplib.py
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index 6644554..0550f0a 100644
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--- a/Lib/ftplib.py
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+++ b/Lib/ftplib.py
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@@ -108,6 +108,8 @@ class FTP:
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file = None
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welcome = None
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passiveserver = 1
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+ # Disables https://bugs.python.org/issue43285 security if set to True.
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+ trust_server_pasv_ipv4_address = False
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# Initialization method (called by class instantiation).
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# Initialize host to localhost, port to standard ftp port
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@@ -310,8 +312,13 @@ class FTP:
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return sock
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def makepasv(self):
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+ """Internal: Does the PASV or EPSV handshake -> (address, port)"""
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if self.af == socket.AF_INET:
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- host, port = parse227(self.sendcmd('PASV'))
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+ untrusted_host, port = parse227(self.sendcmd('PASV'))
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+ if self.trust_server_pasv_ipv4_address:
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+ host = untrusted_host
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+ else:
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+ host = self.sock.getpeername()[0]
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else:
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host, port = parse229(self.sendcmd('EPSV'), self.sock.getpeername())
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return host, port
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diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
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index 8a3eb06..62a3f5e 100644
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--- a/Lib/test/test_ftplib.py
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+++ b/Lib/test/test_ftplib.py
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@@ -67,6 +67,10 @@ class DummyFTPHandler(asynchat.async_chat):
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self.rest = None
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self.next_retr_data = RETR_DATA
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self.push('220 welcome')
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+ # We use this as the string IPv4 address to direct the client
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+ # to in response to a PASV command. To test security behavior.
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+ # https://bugs.python.org/issue43285/.
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+ self.fake_pasv_server_ip = '252.253.254.255'
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def collect_incoming_data(self, data):
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self.in_buffer.append(data)
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@@ -109,7 +113,8 @@ class DummyFTPHandler(asynchat.async_chat):
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sock.bind((self.socket.getsockname()[0], 0))
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sock.listen(5)
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sock.settimeout(10)
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- ip, port = sock.getsockname()[:2]
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+ port = sock.getsockname()[1]
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+ ip = self.fake_pasv_server_ip
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ip = ip.replace('.', ',')
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p1, p2 = divmod(port, 256)
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self.push('227 entering passive mode (%s,%d,%d)' %(ip, p1, p2))
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@@ -577,6 +582,26 @@ class TestFTPClass(TestCase):
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# IPv4 is in use, just make sure send_epsv has not been used
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self.assertEqual(self.server.handler_instance.last_received_cmd, 'pasv')
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+ def test_makepasv_issue43285_security_disabled(self):
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+ """Test the opt-in to the old vulnerable behavior."""
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+ self.client.trust_server_pasv_ipv4_address = True
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+ bad_host, port = self.client.makepasv()
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+ self.assertEqual(
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+ bad_host, self.server.handler_instance.fake_pasv_server_ip)
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+ # Opening and closing a connection keeps the dummy server happy
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+ # instead of timing out on accept.
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+ socket.create_connection((self.client.sock.getpeername()[0], port),
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+ timeout=TIMEOUT).close()
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+
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+ def test_makepasv_issue43285_security_enabled_default(self):
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+ self.assertFalse(self.client.trust_server_pasv_ipv4_address)
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+ trusted_host, port = self.client.makepasv()
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+ self.assertNotEqual(
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+ trusted_host, self.server.handler_instance.fake_pasv_server_ip)
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+ # Opening and closing a connection keeps the dummy server happy
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+ # instead of timing out on accept.
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+ socket.create_connection((trusted_host, port), timeout=TIMEOUT).close()
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+
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def test_line_too_long(self):
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self.assertRaises(ftplib.Error, self.client.sendcmd,
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'x' * self.client.maxline * 2)
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