Issue #2054: ftplib now provides an FTP_TLS class to do secure FTP using

TLS or SSL.  Patch by Giampaolo Rodola'.

Doc/library/ftplib.rst

@@ -49,6 +49,41 @@ The module defines the following items:
    .. versionchanged:: 2.6
       *timeout* was added.
 
+.. class:: FTP_TLS([host[, user[, passwd[, acct[, keyfile[, certfile[, timeout]]]]]]])
+
+   A :class:`FTP` subclass which adds TLS support to FTP as described in
+   :rfc:`4217`.
+   Connect as usual to port 21 implicitly securing the FTP control connection
+   before authenticating. Securing the data connection requires user to
+   explicitly ask for it by calling :exc:`prot_p()` method.
+   *keyfile* and *certfile* are optional - they can contain a PEM formatted
+   private key and certificate chain file for the SSL connection.
+
+   .. versionadded:: 2.7 Contributed by Giampaolo Rodola'
+
+
+   Here's a sample session using :class:`FTP_TLS` class:
+
+   >>> from ftplib import FTP_TLS
+   >>> ftps = FTP_TLS('ftp.python.org')
+   >>> ftps.login()              # login anonimously previously securing control channel
+   >>> ftps.prot_p()             # switch to secure data connection
+   >>> ftps.retrlines('LIST')    # list directory content securely
+   total 9
+   drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 .
+   drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 ..
+   drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 bin
+   drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 etc
+   d-wxrwxr-x   2 ftp      wheel        1024 Sep  5 13:43 incoming
+   drwxr-xr-x   2 root     wheel        1024 Nov 17  1993 lib
+   drwxr-xr-x   6 1094     wheel        1024 Sep 13 19:07 pub
+   drwxr-xr-x   3 root     wheel        1024 Jan  3  1994 usr
+   -rw-r--r--   1 root     root          312 Aug  1  1994 welcome.msg
+   '226 Transfer complete.'
+   >>> ftps.quit()
+   >>>
+
+
 
    .. attribute:: all_errors
 
@@ -329,3 +364,26 @@ followed by ``lines`` for the text version or ``binary`` for the binary version.
    :meth:`close` or :meth:`quit` you cannot reopen the connection by issuing
    another :meth:`login` method).
 
+
+FTP_TLS Objects
+---------------
+
+:class:`FTP_TLS` class inherits from :class:`FTP`, defining these additional objects:
+
+.. attribute:: FTP_TLS.ssl_version
+
+   The SSL version to use (defaults to *TLSv1*).
+
+.. method:: FTP_TLS.auth()
+
+   Set up secure control connection by using TLS or SSL, depending on what specified in :meth:`ssl_version` attribute.
+
+.. method:: FTP_TLS.prot_p()
+
+   Set up secure data connection.
+
+.. method:: FTP_TLS.prot_c()
+
+   Set up clear text data connection.
+
+

Lib/ftplib.py

@@ -33,6 +33,7 @@ python ftplib.py -d localhost -l -p -l
 # Modified by Jack to work on the mac.
 # Modified by Siebren to support docstrings and PASV.
 # Modified by Phil Schwartz to add storbinary and storlines callbacks.
+# Modified by Giampaolo Rodola' to add TLS support.
 #
 
 import os
@@ -575,6 +576,181 @@ class FTP:
             self.file = self.sock = None
 
 
+try:
+    import ssl
+except ImportError:
+    pass
+else:
+    class FTP_TLS(FTP):
+        '''A FTP subclass which adds TLS support to FTP as described
+        in RFC-4217.
+
+        Connect as usual to port 21 implicitly securing the FTP control
+        connection before authenticating.
+
+        Securing the data connection requires user to explicitly ask
+        for it by calling prot_p() method.
+
+        Usage example:
+        >>> from ftplib import FTP_TLS
+        >>> ftps = FTP_TLS('ftp.python.org')
+        >>> ftps.login()  # login anonimously previously securing control channel
+        '230 Guest login ok, access restrictions apply.'
+        >>> ftps.prot_p()  # switch to secure data connection
+        '200 Protection level set to P'
+        >>> ftps.retrlines('LIST')  # list directory content securely
+        total 9
+        drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 .
+        drwxr-xr-x   8 root     wheel        1024 Jan  3  1994 ..
+        drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 bin
+        drwxr-xr-x   2 root     wheel        1024 Jan  3  1994 etc
+        d-wxrwxr-x   2 ftp      wheel        1024 Sep  5 13:43 incoming
+        drwxr-xr-x   2 root     wheel        1024 Nov 17  1993 lib
+        drwxr-xr-x   6 1094     wheel        1024 Sep 13 19:07 pub
+        drwxr-xr-x   3 root     wheel        1024 Jan  3  1994 usr
+        -rw-r--r--   1 root     root          312 Aug  1  1994 welcome.msg
+        '226 Transfer complete.'
+        >>> ftps.quit()
+        '221 Goodbye.'
+        >>>
+        '''
+        ssl_version = ssl.PROTOCOL_TLSv1
+
+        def __init__(self, host='', user='', passwd='', acct='', keyfile=None,
+                     certfile=None, timeout=_GLOBAL_DEFAULT_TIMEOUT):
+            self.keyfile = keyfile
+            self.certfile = certfile
+            self._prot_p = False
+            FTP.__init__(self, host, user, passwd, acct, timeout)
+
+        def login(self, user='', passwd='', acct='', secure=True):
+            if secure and not isinstance(self.sock, ssl.SSLSocket):
+                self.auth()
+            return FTP.login(self, user, passwd, acct)
+
+        def auth(self):
+            '''Set up secure control connection by using TLS/SSL.'''
+            if isinstance(self.sock, ssl.SSLSocket):
+                raise ValueError("Already using TLS")
+            if self.ssl_version == ssl.PROTOCOL_TLSv1:
+                resp = self.voidcmd('AUTH TLS')
+            else:
+                resp = self.voidcmd('AUTH SSL')
+            self.sock = ssl.wrap_socket(self.sock, self.keyfile, self.certfile,
+                                        ssl_version=self.ssl_version)
+            self.file = self.sock.makefile(mode='rb')
+            return resp
+
+        def prot_p(self):
+            '''Set up secure data connection.'''
+            # PROT defines whether or not the data channel is to be protected.
+            # Though RFC-2228 defines four possible protection levels,
+            # RFC-4217 only recommends two, Clear and Private.
+            # Clear (PROT C) means that no security is to be used on the
+            # data-channel, Private (PROT P) means that the data-channel
+            # should be protected by TLS.
+            # PBSZ command MUST still be issued, but must have a parameter of
+            # '0' to indicate that no buffering is taking place and the data
+            # connection should not be encapsulated.
+            self.voidcmd('PBSZ 0')
+            resp = self.voidcmd('PROT P')
+            self._prot_p = True
+            return resp
+
+        def prot_c(self):
+            '''Set up clear text data connection.'''
+            resp = self.voidcmd('PROT C')
+            self._prot_p = False
+            return resp
+
+        # --- Overridden FTP methods
+
+        def ntransfercmd(self, cmd, rest=None):
+            conn, size = FTP.ntransfercmd(self, cmd, rest)
+            if self._prot_p:
+                conn = ssl.wrap_socket(conn, self.keyfile, self.certfile,
+                                       ssl_version=self.ssl_version)
+            return conn, size
+
+        def retrbinary(self, cmd, callback, blocksize=8192, rest=None):
+            self.voidcmd('TYPE I')
+            conn = self.transfercmd(cmd, rest)
+            try:
+                while 1:
+                    data = conn.recv(blocksize)
+                    if not data:
+                        break
+                    callback(data)
+                # shutdown ssl layer
+                if isinstance(conn, ssl.SSLSocket):
+                    conn.unwrap()
+            finally:
+                conn.close()
+            return self.voidresp()
+
+        def retrlines(self, cmd, callback = None):
+            if callback is None: callback = print_line
+            resp = self.sendcmd('TYPE A')
+            conn = self.transfercmd(cmd)
+            fp = conn.makefile('rb')
+            try:
+                while 1:
+                    line = fp.readline()
+                    if self.debugging > 2: print '*retr*', repr(line)
+                    if not line:
+                        break
+                    if line[-2:] == CRLF:
+                        line = line[:-2]
+                    elif line[-1:] == '\n':
+                        line = line[:-1]
+                    callback(line)
+                # shutdown ssl layer
+                if isinstance(conn, ssl.SSLSocket):
+                    conn.unwrap()
+            finally:
+                fp.close()
+                conn.close()
+            return self.voidresp()
+
+        def storbinary(self, cmd, fp, blocksize=8192, callback=None):
+            self.voidcmd('TYPE I')
+            conn = self.transfercmd(cmd)
+            try:
+                while 1:
+                    buf = fp.read(blocksize)
+                    if not buf: break
+                    conn.sendall(buf)
+                    if callback: callback(buf)
+                # shutdown ssl layer
+                if isinstance(conn, ssl.SSLSocket):
+                    conn.unwrap()
+            finally:
+                conn.close()
+            return self.voidresp()
+
+        def storlines(self, cmd, fp, callback=None):
+            self.voidcmd('TYPE A')
+            conn = self.transfercmd(cmd)
+            try:
+                while 1:
+                    buf = fp.readline()
+                    if not buf: break
+                    if buf[-2:] != CRLF:
+                        if buf[-1] in CRLF: buf = buf[:-1]
+                        buf = buf + CRLF
+                    conn.sendall(buf)
+                    if callback: callback(buf)
+                # shutdown ssl layer
+                if isinstance(conn, ssl.SSLSocket):
+                    conn.unwrap()
+            finally:
+                conn.close()
+            return self.voidresp()
+
+    __all__.append('FTP_TLS')
+    all_errors = (Error, IOError, EOFError, ssl.SSLError)
+
+
 _150_re = None
 
 def parse150(resp):

Lib/test/test_ftplib.py

@@ -1,6 +1,7 @@
 """Test script for ftplib module."""
 
-# Modified by Giampaolo Rodola' to test FTP class and IPv6 environment
+# Modified by Giampaolo Rodola' to test FTP class, IPv6 and TLS
+# environment
 
 import ftplib
 import threading
@@ -8,6 +9,12 @@ import asyncore
 import asynchat
 import socket
 import StringIO
+import errno
+import os
+try:
+    import ssl
+except ImportError:
+    ssl = None
 
 from unittest import TestCase
 from test import test_support
@@ -38,6 +45,8 @@ class DummyDTPHandler(asynchat.async_chat):
 
 class DummyFTPHandler(asynchat.async_chat):
 
+    dtp_handler = DummyDTPHandler
+
     def __init__(self, conn):
         asynchat.async_chat.__init__(self, conn)
         self.set_terminator("\r\n")
@@ -81,7 +90,7 @@ class DummyFTPHandler(asynchat.async_chat):
         ip = '%d.%d.%d.%d' %tuple(addr[:4])
         port = (addr[4] * 256) + addr[5]
         s = socket.create_connection((ip, port), timeout=2)
-        self.dtp = DummyDTPHandler(s, baseclass=self)
+        self.dtp = self.dtp_handler(s, baseclass=self)
         self.push('200 active data connection established')
 
     def cmd_pasv(self, arg):
@@ -93,13 +102,13 @@ class DummyFTPHandler(asynchat.async_chat):
         ip = ip.replace('.', ','); p1 = port / 256; p2 = port % 256
         self.push('227 entering passive mode (%s,%d,%d)' %(ip, p1, p2))
         conn, addr = sock.accept()
-        self.dtp = DummyDTPHandler(conn, baseclass=self)
+        self.dtp = self.dtp_handler(conn, baseclass=self)
 
     def cmd_eprt(self, arg):
         af, ip, port = arg.split(arg[0])[1:-1]
         port = int(port)
         s = socket.create_connection((ip, port), timeout=2)
-        self.dtp = DummyDTPHandler(s, baseclass=self)
+        self.dtp = self.dtp_handler(s, baseclass=self)
         self.push('200 active data connection established')
 
     def cmd_epsv(self, arg):
@@ -110,7 +119,7 @@ class DummyFTPHandler(asynchat.async_chat):
         port = sock.getsockname()[1]
         self.push('229 entering extended passive mode (|||%d|)' %port)
         conn, addr = sock.accept()
-        self.dtp = DummyDTPHandler(conn, baseclass=self)
+        self.dtp = self.dtp_handler(conn, baseclass=self)
 
     def cmd_echo(self, arg):
         # sends back the received string (used by the test suite)
@@ -225,6 +234,126 @@ class DummyFTPServer(asyncore.dispatcher, threading.Thread):
         raise
 
 
+if ssl is not None:
+
+    CERTFILE = os.path.join(os.path.dirname(__file__), "keycert.pem")
+
+    class SSLConnection(object, asyncore.dispatcher):
+        """An asyncore.dispatcher subclass supporting TLS/SSL."""
+
+        _ssl_accepting = False
+
+        def secure_connection(self):
+            self.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._ssl_accepting = True
+
+        def _do_ssl_handshake(self):
+            try:
+                self.socket.do_handshake()
+            except ssl.SSLError, 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, err:
+                if err.args[0] == errno.ECONNABORTED:
+                    return self.handle_close()
+            else:
+                self._ssl_accepting = False
+
+        def handle_read_event(self):
+            if self._ssl_accepting:
+                self._do_ssl_handshake()
+            else:
+                super(SSLConnection, self).handle_read_event()
+
+        def handle_write_event(self):
+            if self._ssl_accepting:
+                self._do_ssl_handshake()
+            else:
+                super(SSLConnection, self).handle_write_event()
+
+        def send(self, data):
+            try:
+                return super(SSLConnection, self).send(data)
+            except ssl.SSLError, err:
+                if err.args[0] in (ssl.SSL_ERROR_EOF, ssl.SSL_ERROR_ZERO_RETURN):
+                    return 0
+                raise
+
+        def recv(self, buffer_size):
+            try:
+                return super(SSLConnection, self).recv(buffer_size)
+            except ssl.SSLError, err:
+                if err.args[0] in (ssl.SSL_ERROR_EOF, ssl.SSL_ERROR_ZERO_RETURN):
+                    self.handle_close()
+                    return ''
+                raise
+
+        def handle_error(self):
+            raise
+
+        def close(self):
+            try:
+                if isinstance(self.socket, ssl.SSLSocket):
+                    if self.socket._sslobj is not None:
+                        self.socket.unwrap()
+            finally:
+                super(SSLConnection, self).close()
+
+
+    class DummyTLS_DTPHandler(SSLConnection, DummyDTPHandler):
+        """A DummyDTPHandler subclass supporting TLS/SSL."""
+
+        def __init__(self, conn, baseclass):
+            DummyDTPHandler.__init__(self, conn, baseclass)
+            if self.baseclass.secure_data_channel:
+                self.secure_connection()
+
+
+    class DummyTLS_FTPHandler(SSLConnection, DummyFTPHandler):
+        """A DummyFTPHandler subclass supporting TLS/SSL."""
+
+        dtp_handler = DummyTLS_DTPHandler
+
+        def __init__(self, conn):
+            DummyFTPHandler.__init__(self, conn)
+            self.secure_data_channel = False
+
+        def cmd_auth(self, line):
+            """Set up secure control channel."""
+            self.push('234 AUTH TLS successful')
+            self.secure_connection()
+
+        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'.
+            Any other value is accepted but ignored.
+            """
+            self.push('200 PBSZ=0 successful.')
+
+        def cmd_prot(self, line):
+            """Setup un/secure data channel."""
+            arg = line.upper()
+            if arg == 'C':
+                self.push('200 Protection set to Clear')
+                self.secure_data_channel = False
+            elif arg == 'P':
+                self.push('200 Protection set to Private')
+                self.secure_data_channel = True
+            else:
+                self.push("502 Unrecognized PROT type (use C or P).")
+
+
+    class DummyTLS_FTPServer(DummyFTPServer):
+        handler = DummyTLS_FTPHandler
+
+
 class TestFTPClass(TestCase):
 
     def setUp(self):
@@ -398,6 +527,81 @@ class TestIPv6Environment(TestCase):
         retr()
 
 
+class TestTLS_FTPClassMixin(TestFTPClass):
+    """Repeat TestFTPClass tests starting the TLS layer for both control
+    and data connections first.
+    """
+
+    def setUp(self):
+        self.server = DummyTLS_FTPServer((HOST, 0))
+        self.server.start()
+        self.client = ftplib.FTP_TLS(timeout=2)
+        self.client.connect(self.server.host, self.server.port)
+        # enable TLS
+        self.client.auth()
+        self.client.prot_p()
+
+
+class TestTLS_FTPClass(TestCase):
+    """Specific TLS_FTP class tests."""
+
+    def setUp(self):
+        self.server = DummyTLS_FTPServer((HOST, 0))
+        self.server.start()
+        self.client = ftplib.FTP_TLS(timeout=2)
+        self.client.connect(self.server.host, self.server.port)
+
+    def tearDown(self):
+        self.client.close()
+        self.server.stop()
+
+    def test_control_connection(self):
+        self.assertFalse(isinstance(self.client.sock, ssl.SSLSocket))
+        self.client.auth()
+        self.assertTrue(isinstance(self.client.sock, ssl.SSLSocket))
+
+    def test_data_connection(self):
+        # clear text
+        sock = self.client.transfercmd('list')
+        self.assertFalse(isinstance(sock, ssl.SSLSocket))
+        sock.close()
+        self.client.voidresp()
+
+        # secured, after PROT P
+        self.client.prot_p()
+        sock = self.client.transfercmd('list')
+        self.assertTrue(isinstance(sock, ssl.SSLSocket))
+        sock.close()
+        self.client.voidresp()
+
+        # PROT C is issued, the connection must be in cleartext again
+        self.client.prot_c()
+        sock = self.client.transfercmd('list')
+        self.assertFalse(isinstance(sock, ssl.SSLSocket))
+        sock.close()
+        self.client.voidresp()
+
+    def test_login(self):
+        # login() is supposed to implicitly secure the control connection
+        self.assertFalse(isinstance(self.client.sock, ssl.SSLSocket))
+        self.client.login()
+        self.assertTrue(isinstance(self.client.sock, ssl.SSLSocket))
+        # make sure that AUTH TLS doesn't get issued again
+        self.client.login()
+
+    def test_auth_issued_twice(self):
+        self.client.auth()
+        self.assertRaises(ValueError, self.client.auth)
+
+    def test_auth_ssl(self):
+        try:
+            self.client.ssl_version = ssl.PROTOCOL_SSLv3
+            self.client.auth()
+            self.assertRaises(ValueError, self.client.auth)
+        finally:
+            self.client.ssl_version = ssl.PROTOCOL_TLSv1
+
+
 class TestTimeouts(TestCase):
 
     def setUp(self):
@@ -499,6 +703,10 @@ def test_main():
             pass
         else:
             tests.append(TestIPv6Environment)
+
+    if ssl is not None:
+        tests.extend([TestTLS_FTPClassMixin, TestTLS_FTPClass])
+
     thread_info = test_support.threading_setup()
     try:
         test_support.run_unittest(*tests)

Misc/NEWS

@@ -429,6 +429,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #2054: ftplib now provides an FTP_TLS class to do secure FTP using
+  TLS or SSL.  Patch by Giampaolo Rodola'.
+
 - Issue #4969: The mimetypes module now reads the MIME database from
   the registry under Windows.  Patch by Gabriel Genellina.