ftplib - 504 Security mechanism 'TLS' not implemented

Question

I'm trying to connect to Secure FTP using ftplib, but it does not work for some reason (trying to connect to www.sharefile.com ftp. there it says to use this address: company.sharefileftp.com)

I'm trying this approach (FTPES - FTP over explicit TLS/SSL in Python):

from ftplib import FTP_TLS
ftps = FTP_TLS('company.sharefileftp.com')
ftps.login('user', 'pass')           # login anonymously before securing control channel
ftps.prot_p()          # switch to secure data connection.. IMPORTANT! Otherwise, only the user and password is encrypted and not all the file data.
ftps.retrlines('LIST')

filename = 'remote_filename.bin'
print 'Opening local file ' + filename
myfile = open(filename, 'wb')

ftps.retrbinary('RETR %s' % filename, myfile.write)

ftps.close()

But it gives me this error (when calling this line ftps.login('testuser', 'testpass')):

error_perm                                Traceback (most recent call last)
<ipython-input-17-bfe01179f1c2> in <module>()
----> ftps.login('user', 'pass')

/usr/lib/python2.7/ftplib.pyc in login(self, user, passwd, acct, secure)
    650         def login(self, user='', passwd='', acct='', secure=True):
    651             if secure and not isinstance(self.sock, ssl.SSLSocket):
--> 652                 self.auth()
    653             return FTP.login(self, user, passwd, acct)
    654 

/usr/lib/python2.7/ftplib.pyc in auth(self)
    658                 raise ValueError("Already using TLS")
    659             if self.ssl_version == ssl.PROTOCOL_TLSv1:
--> 660                 resp = self.voidcmd('AUTH TLS')
    661             else:
    662                 resp = self.voidcmd('AUTH SSL')

/usr/lib/python2.7/ftplib.pyc in voidcmd(self, cmd)
    252         """Send a command and expect a response beginning with '2'."""
    253         self.putcmd(cmd)
--> 254         return self.voidresp()
    255 
    256     def sendport(self, host, port):

/usr/lib/python2.7/ftplib.pyc in voidresp(self)
    227     def voidresp(self):
    228         """Expect a response beginning with '2'."""
--> 229         resp = self.getresp()
    230         if resp[:1] != '2':
    231             raise error_reply, resp

/usr/lib/python2.7/ftplib.pyc in getresp(self)
    222             raise error_temp, resp
    223         if c == '5':
--> 224             raise error_perm, resp
    225         raise error_proto, resp
    226 

error_perm: 504 Security mechanism 'TLS' not implemented.

P.S. But I can connect using FTP (not secure one):

>>> from ftplib import FTP
>>> ftp = FTP('company.sharefileftp.com')     # connect to host, default port
>>> ftp.login('user', 'pass')                     # user anonymous, passwd anonymous@

Answer 1

The server simply does not support TLS, neither the old 'AUTH SSL' nor the newer 'AUTH TLS'. This problem is unrelated to python as the following test with telnet shows:

$telnet company.sharefileftp.com 21
Trying 54.194.108.219...
Connected to company.sharefileftp.com.
Escape character is '^]'.
220 ftp-eu-1.sharefileftp.com FTP Server Ready
AUTH TLS
504 Security mechanism 'TLS' not implemented.
AUTH SSL
504 Security mechanism 'SSL' not implemented.
QUIT
221-Sent: 142 bytes   Rcvd: 26 bytes   Time: 15s
221 ftp-eu-1.sharefileftp.com session ended.
Connection closed by foreign host.

But it does support the (old and never standardized) implicit TLS:

$ openssl s_client -connect company.sharefileftp.com:990
...
SSL-Session:
    Protocol  : TLSv1
   Cipher    : RC4-SHA
...
220 ftp-eu-1.sharefileftp.com FTP Server Ready (SSL)

Answer 2

You are connecting with the Explicit TLS/SSL (what is generally the recommended mode).

It seems that the sharefile.com does support Implicit TLS/SSL only (what is quite unusual).

Contrary, it seems that the ftplib does not support Implicit TLS/SSL out of the box.

You can fix it though. See answers to:
Python FTP implicit TLS connection issue