Golang FTP PASS (password) command works locally, but doesn't while running on ECS

Getting Help
1

I have a go server that uses github.com/jlaffaye/ftp library for getting FTP files from a remote server.
I first of all get the connection

	conn, err := ftp.DialTimeout(cfg.Host+cfg.Port, time.Second*15)
	if err != nil {
		return nil, fmt.Errorf("ftp dial error: %v", err)
	}

After which, I try to login with

	err = conn.Login(cfg.Username, pwd)
	if err != nil {
		return nil, fmt.Errorf("ftp login error: %v", err)
	}

I log in successfully while running locally.
This is also confirmed while looking at the output of

		code, msg, err := c.cmd(StatusLoggedIn, "PASS %s", password)
		log.Printf("pass, code %d, msg %s, err %v", code, msg, err)
		if err != nil {
			return err
		}

Which is from my vendor pkg under \vendor\github.com\jlaffaye\ftp\ftp.go
With the output being

2021/06/16 23:12:45 pass, code 230, msg User xxxx logged in, err <nil>

While running the same service deployed on amazon ECS,
the output of the vendored pkg under \vendor\github.com\jlaffaye\ftp\ftp.go becomes

2021/06/16 20:24:28 pass, code 0, msg , err EOF

Any idea on what might be causing this?

2

Also wanted to note that

runs the FTP USER command also. This step passes while running both locally and on ECS

4

using an if errors.Is(err, io.EOF) and returning nil if true helps, but later still get EOF while running other FTP commands.

5

@justin-obn Have you tried using the DialWithDebugOutput DialOption? Maybe that will help point you in the right direction. For example,

c, err := ftp.Dial(
  host,
  ftp.DialWithDebugOutput(os.Stdout),
  ftp.DialWithTimeout(time.Second*15),
)
1 Like
6

@n0muh I’ll try that, but did some debugging already with telnet.
From local machine connected to the needed VPN, I can connect

# telnet ftp.xxxxxxxxx.net 21
Trying xx.xxx.xxx.xxx...
Connected to xxxxxxxxxxx.net.
Escape character is '^]'.
220 ProFTPD 1.3.5 Server (ProFTPD Default Installation) [xx.xxx.xxx.xxx]
USER xxxx
331 Password required for xxxx
PASS xxxxxxxxx
230 User xxx logged in

From an EC2 machine in a different VPC

Connected to ftp.xxxxxxxxxxxx.net.
Escape character is '^]'.
220 ProFTPD 1.3.5 Server (ProFTPD Default Installation) [xx.xxx.xxx.xxx]
USER xxxx
331 Password required for xxxx
PASS xxxxxxxx
Connection closed by foreign host.
7

@n0muh Thanks, the debug output really helped. It seems the ftp server is not reachable when running from amazon ECS because the IP address for the ec2 machine isn’t whitelisted

2 Likes
8

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