Rmys
134 lines
5.9 KiB
Diff
134 lines
5.9 KiB
Diff
From 117bd40b3844733e96a8f5ccc9460900698cffbe Mon Sep 17 00:00:00 2001
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From: "Miss Islington (bot)"
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<31488909+miss-islington@users.noreply.github.com>
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Date: Tue, 16 Mar 2021 14:08:30 -0700
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Subject: [PATCH 26/30] [3.6] bpo-43285 Make ftplib not trust the PASV
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response. (GH-24838) (GH-24881) (GH-24882)
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The IPv4 address value returned from the server in response to the PASV command
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should not be trusted. This prevents a malicious FTP server from using the
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response to probe IPv4 address and port combinations on the client network.
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Instead of using the returned address, we use the IP address we're
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already connected to. This is the strategy other ftp clients adopted,
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and matches the only strategy available for the modern IPv6 EPSV command
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where the server response must return a port number and nothing else.
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For the rare user who _wants_ this ugly behavior, set a `trust_server_pasv_ipv4_address`
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attribute on your `ftplib.FTP` instance to True..
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(cherry picked from commit 0ab152c6b5d95caa2dc1a30fa96e10258b5f188e)
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
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(cherry picked from commit 664d1d16274b47eea6ec92572e1ebf3939a6fa0c)
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Rebased for Python 2.7 by Michał Górny <mgorny@gentoo.org>
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---
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Lib/ftplib.py | 9 +++++-
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Lib/test/test_ftplib.py | 29 +++++++++++++++++--
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.../2021-03-13-03-48-14.bpo-43285.g-Hah3.rst | 8 +++++
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3 files changed, 43 insertions(+), 3 deletions(-)
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create mode 100644 Misc/NEWS.d/next/Security/2021-03-13-03-48-14.bpo-43285.g-Hah3.rst
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diff --git a/Lib/ftplib.py b/Lib/ftplib.py
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index 6644554792..0550f0ab9f 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 8a3eb067a4..f3217d686d 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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@@ -109,8 +113,9 @@ 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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- ip = ip.replace('.', ',')
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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('.', ','); p1 = port // 256; p2 = port % 256
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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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conn, addr = sock.accept()
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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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diff --git a/Misc/NEWS.d/next/Security/2021-03-13-03-48-14.bpo-43285.g-Hah3.rst b/Misc/NEWS.d/next/Security/2021-03-13-03-48-14.bpo-43285.g-Hah3.rst
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new file mode 100644
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index 0000000000..8312b7e885
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Security/2021-03-13-03-48-14.bpo-43285.g-Hah3.rst
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@@ -0,0 +1,8 @@
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+:mod:`ftplib` no longer trusts the IP address value returned from the server
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+in response to the PASV command by default. This prevents a malicious FTP
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+server from using the response to probe IPv4 address and port combinations
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+on the client network.
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+
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+Code that requires the former vulnerable behavior may set a
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+``trust_server_pasv_ipv4_address`` attribute on their
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+:class:`ftplib.FTP` instances to ``True`` to re-enable it.
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--
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2.32.0
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