Security policy rule - allowing a specific host access to ftp.sophos.com

[rchung54]

Hi DPoppleton,

Still not working.

I get this from the log in the Filezila FTP client. 

Filezila client configured as so for FTP over SSL/TLS

Logs from Unified today.

Any further advice will be appreciated.

[DPoppleton]

This isn't caused by the firewall.... I seem to remember a problem with the MLSD command with certain clients or servers while running a passive FTP connection. Try it as an active connection and I think it would work.

[soujanyabargavi]

Thanks for the info on allowing a specific host access to ftp.sophos.com jira 

[Rikkert_Kooy]

Very important this is NOT sftp (which is a file transfer protocol using the same port and encryption as ssh). We are talking about ftp over ssl.

this is explicit ftp over ssl. Meaning the client wil use ftp to connect to ftp.sophos.com and than do TLS encryption and than with an encrypted connection it will do authentication and negotation which ports to use for the data connection.

fom https://community.sophos.com/kb/en-us/113454

you will need to allow the application: ftp to connect to tcp port 990 for ftp.sophos.com.

after that you will need to allow the application ssl with ports 50000-51000

[rchung54]

Hi Rikkert_Kooy,

Thank you for your reply. My mistake, it is explicit FTP over SSL, not SFTP.

I have added ftp to the Application and already had TCP port 990 under the Service. I also added SSL and the port range 50000-51000, but it is still not working. The Palo is not configured for SSL decrypt/encrypt. Could this be why it is still not working?

Unified logs - it says incomplete in Application. What does this mean please?

Error message on the Filezilla client

Thanks.

[rchung54]

Hi DPoppleton,

I set the Transfer Settings to Active in the FTP client (I guess this what you meant), but still not working. I did what Rikkert_Kooy suggested too and still no joy. Is it because the Palo is not configured with SSL decrypt/encrypt?

Thanks.

[Rikkert_Kooy]

Hi rchung54,

decrypting ssl traffic is not strictly needed to make this connection possible. I have configured passive ftp with explicit ssl in this way before.

I see that your rule is being hit for the passive connection on port 50661 (your filezilla screenshot shows that the client is trying to connect to 195.171.192.29:50661 (197*156+227)), but your ftp client either says the connection has timed out or that the server denied the connection (were the three error messages at the same time?).

What does your Palo alto say is the reason for the session end reason? 

[rchung54]

Hi Rikkert_Kooy,

Yes, i saw the three error messages at the same time on the Filezilla client.

The Session End Reason is 'tcp-rst-from-server'. 

What does it mean where it says 'incomplete' under Application please?

Thanks.

[Rikkert_Kooy]

incomplete means not enough packets have gone through the Palo Alto for it to recognise the application. So it doesn't know yet whether it is SSL (which the rule allows) or something else.

If I read the session end reason it seems like the ftp.sophos.com causes the disconnect, but likely because the client was trying to connect to it for 20 seconds.

Why your FTP client wasn't able to actually connect to the server in passive mode I do not understand.