Response: 425 Unable to build data connection: TLS session of data connection not resumed.

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tsmorales
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Joined: 2023-06-01 11:56
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Response: 425 Unable to build data connection: TLS session of data connection not resumed.

#1 Post by tsmorales » 2023-06-01 12:17

Hi Everyone!

We did some little changes on windows server that is running my filezilla server, but I not changed anythink in Filezilla server.
So now all client that already connected one time in my FTP Server are receiving the error bellow.

Status: Disconnected from server
Status: Selected port usually in use by a different protocol.
Status: Resolving address of xxx.xxx.com.br
Status: Connecting to 20.49.x.xxx:990...
Status: Connection established, waiting for welcome message...
Response: 220-FileZilla Server 1.7.1
Response: 220 Please visit https://filezilla-project.org/
Command: AUTH TLS
Response: 234 Using authentication type TLS.
Status: Initializing TLS...
Status: TLS connection established.
Command: USER xxxx
Response: 331 Please, specify the password.
Command: PASS ************
Response: 230 Login successful.
Command: PBSZ 0
Response: 200 PBSZ=0
Command: PROT P
Response: 200 Protection level set to P
Status: Logged in
Status: Retrieving directory listing...
Command: PWD
Response: 257 "/" is current directory.
Command: TYPE I
Response: 200 Type set to I
Command: PASV
Response: 227 Entering Passive Mode (20,49,X,XXX,80,61)
Command: MLSD
Response: 150 About to start data transfer.
Response: 425 Unable to build data connection: TLS session of data connection not resumed.
Error: Failed to retrieve directory listing


I tried to create a new server with same IP and domain, restored de configuration file, and the error is the same.

I´m executing last version of filezilla Server (1.7.1) and client (3.64.0)

The last test I did was install the client in a new machine, that never had filezilla client installed and it is working perfectly.
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botg
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Re: Response: 425 Unable to build data connection: TLS session of data connection not resumed.

#2 Post by botg » 2023-06-01 14:10

Port 990 is for the legacy implicit FTP over TLS, don't place the listener for explicit FTP over TLS on this port. You should use port 21 for the recommended explicit FTP over TLS.

Both FileZilla and FileZilla Server fully support TLS session resumption on the data connection. Seeing the resumption failure dialog thus can only mean one of two things:
  1. There is a malicious firewall or AV product somewhere between the client and the server that injects fake certificates into the connection (this is why checking certificate fingerprints is so important, it foils these malicious components)
  2. There is a NAT router sitting in front of the server and the ports aren't forwarded 1:1

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