Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

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sudoranger
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Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#1 Post by sudoranger » 2019-01-30 21:50

My client:
FileZilla Client 3.40.0.

My server:
ProFTPD Version 1.3.5e.

My problem:
Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error? I'm trying to upload a png file which I exported using Adobe Illustrator CC 2018. I only get error for this current png file at the moment. I can upload other files successfully. For some weird reason which I couldn't find in the log, I sometimes can upload this png file and sometimes I can't... I didn't try using other clients yet but I'm guessing this is a proftpd misconfig. I'm the root but I'm not a pro system admin, this is just my personal FTP server to backup my artworks...

I'm not behind any firewall so does the server. No iptables and such. I noticed this problem only occur when it's uploading via BINARY mode? I tried switching to ACTIVE/PASSIVE and ASCII/BINARY to no avail.

For your information, this specific vector file was downloaded from freepik and exported to png. I have no problem uploading my other .png files (at least in my current case not sure about other filetypes yet).

FileZilla Client log

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Status:	Resolving address of <domain>
Status:	Connecting to <IPv6>:21...
Status:	Connection established, waiting for welcome message...
Status:	Initializing TLS...
Status:	Verifying certificate...
Status:	TLS connection established.
Status:	Logged in
Status:	Retrieving directory listing...
Status:	Directory listing of "/home/<username>" successful
Status:	Resolving address of <domain>
Status:	Connecting to <IPv6>:21...
Status:	Connection established, waiting for welcome message...
Status:	Initializing TLS...
Status:	Verifying certificate...
Status:	TLS connection established.
Status:	Logged in
Status:	Starting upload of C:\Users\<username>\Desktop\test.png
Command:	CWD /home/<username>
Response:	250 CWD command successful
Command:	PWD
Response:	257 "/home/<username>" is the current directory
Command:	TYPE I
Response:	200 Type set to I
Command:	EPSV
Response:	229 Entering Extended Passive Mode (|||7472|)
Command:	STOR test.png
Response:	150 Opening BINARY mode data connection for test.png
Response:	450 Transfer aborted. Link to file server lost
Error:	File transfer failed
Status:	Retrieving directory listing of "/home/<username>"...
Status:	Directory listing of "/home/<username>" successful
Status:	Disconnected from server
proftpd.log

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2019-01-31 07:54:55,317 <domain> proftpd[17523] <domain>: ProFTPD 1.3.5e (maint) (built Mon Feb 5 2018 23:27:47 UTC) standalone mode STARTUP
2019-01-30 23:50:37,137 <domain> proftpd[17447] <domain> (<IPv6>[<IPv6>]): notice: user <username>: aborting transfer: Link to file server lost
tls.log

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2019-01-31 07:54:59,119 mod_tls/2.6[17524]: TLS/TLS-C requested, starting TLS handshake
2019-01-31 07:54:59,337 mod_tls/2.6[17524]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-31 07:54:59,337 mod_tls/2.6[17524]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-31 07:54:59,337 mod_tls/2.6[17524]: TLSv1.3 connection accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-30 23:54:59,757 mod_tls/2.6[17524]: Protection set to Private
2019-01-31 07:55:09,100 mod_tls/2.6[17526]: TLS/TLS-C requested, starting TLS handshake
2019-01-31 07:55:09,297 mod_tls/2.6[17526]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-31 07:55:09,298 mod_tls/2.6[17526]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-31 07:55:09,298 mod_tls/2.6[17526]: TLSv1.3 connection accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-30 23:55:09,698 mod_tls/2.6[17526]: Protection set to Private
2019-01-30 23:55:11,310 mod_tls/2.6[17526]: starting TLS negotiation on data connection
2019-01-30 23:55:11,417 mod_tls/2.6[17526]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-30 23:55:11,417 mod_tls/2.6[17526]: TLSv1.3 data connection accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
2019-01-30 23:55:11,809 mod_tls/2.6[17526]: starting TLS negotiation on data connection
2019-01-30 23:55:11,916 mod_tls/2.6[17526]: TLSv1.3 renegotiation accepted, using cipher TLS_AES_256_GCM_SHA384 (256 bits)
xferlog

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Wed Jan 30 23:55:11 2019 0 <IPv6> 0 /home/<username>/test.png b _ i r <username> ftps 0 * i
I read some replies from @boco in the other thread saying:

1. The FTP server you're connected to has a problem. It loses its internal link to one of the storage servers (where the actual files are stored). You need to contact server support so they can fix that.
2. Internal server problems. The FTP server lost the link to its internal storage (large servers have separate storage back-ends). This was a temporary problem.
3. You mean that? This indicates an FTP server problem. The server loses the connection to its storage backend mid-transfer.

However, I'm hosted on a well reputed upsteam provider (not the summer ones) pretty sure this one is on my side not them and FileZilla... I need some heads up from kind senpai out there...

Extra note:
I can transfer this file when not using TLS. I'm using the following conf:

Code: Select all

# /etc/proftpd/proftpd.conf

Include /etc/proftpd/modules.conf

AllowOverwrite on
DefaultChdir ~/sites
DefaultRoot ~
DefaultServer on
MaxClients 3
RootLogin on
ServerIdent on "Welcome to FTP Server"
ServerName "FTP Server"
TimeoutIdle 0
Umask 022 022
UseIPv6 on

<IfModule mod_tls.c>
    TLSDHParamFile /etc/proftpd/dhparams.pem
    TLSCipherSuite HIGH
    TLSEngine on
    TLSLog /var/log/proftpd/tls.log
    TLSOptions NoCertRequest NoSessionReuseRequired
    TLSProtocol SSLv23
    TLSRequired on
    TLSRSACertificateFile /etc/letsencrypt/live/<domain>/fullchain.pem
    TLSRSACertificateKeyFile /etc/letsencrypt/live/<domain>/privkey.pem
</IfModule>

SyslogLevel notice
SystemLog /var/log/proftpd/proftpd.log
TransferLog /var/log/proftpd/xferlog

#SyslogLevel warn
#SystemLog none
#TransferLog none

Include /etc/proftpd/conf.d/

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botg
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#2 Post by botg » 2019-01-31 09:03

This error comes from the server and makes no sense. I suggest contacting ProFTPD support.

paul-ifdnrg
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#3 Post by paul-ifdnrg » 2019-01-31 11:55

i have a similar issue, resolved by downgrading filezilla to 3.39.0

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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#4 Post by botg » 2019-01-31 12:08

Downgrading is not a supported use-case.

eomanis
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#5 Post by eomanis » 2019-02-07 22:36

paul-ifdnrg wrote:
2019-01-31 11:55
i have a similar issue, resolved by downgrading filezilla to 3.39.0
sudoranger wrote:
2019-01-30 21:50
My client:
FileZilla Client 3.40.0.
To weigh in on this, I run an FTP server and one of my users started to have this problem today.
The user in question also uses FileZilla Client 3.40.0.

Before the incident the user has been using my currently running FTP server version without problems. It is ProFTPD 1.3.6 with a backported patch or two, details can be found here:
https://aur.archlinux.org/packages/proftpd/

I myself am not affected despite also using FileZilla Client 3.40.0
My operating system is Arch Linux; the affected user uses OS X.

paul-ifdnrg, sudoranger, are you per chance also using OS X?
In that case this might be an OS X-specific regression from FileZilla Client 3.39.0 to 3.40.0.

sudoranger
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#6 Post by sudoranger » 2019-02-09 17:13

eomanis wrote:
2019-02-07 22:36
paul-ifdnrg, sudoranger, are you per chance also using OS X?
In that case this might be an OS X-specific regression from FileZilla Client 3.39.0 to 3.40.0.
sorry for the late reply, i almost give up with the TLS 1.3 issues on the server-side recently. but since you said this error is also occurring on the 1.3.6 then i feel more reluctant to compile from source.

we are very much aware that this has something to do with the ftp server not supporting TLS 1.3 or the openssl stuff. @botg mentioned it on the other thread.

yes, downgrading might fix the problem but still this is just a workaround. you know the fact that if we downgrade < 3.39 then the whole operation is not using TLS 1.3 and it's not the best practice and a way to move forward.

i also acknowledge that this is purely the server problem and filezilla developers isn't going to comment more on that since it has nothing to do with filezilla client but the server...

i'm not sure what to do next but just hoping that someone from filezilla can offer help to fix those ancient ftp servers...

from my perspective... a client will fail if the server go crazy... so we need to do something to fix the root cause otherwise there's no point of using the client if the server is not doing its job...


---

what do you mean not affected when using OS X? so is this a client's OS problem then? I'm on Windows 10 Pro latest build...

----

just to update on my original post:

the error is happening again to almost all of my files randomly not just the png file mentioned above... already purge my ftp server... not using any at the moment until i find the fix

eomanis
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#7 Post by eomanis » 2019-02-09 23:33

sudoranger wrote:
2019-02-09 17:13
sorry for the late reply, i almost give up with the TLS 1.3 issues on the server-side recently. but since you said this error is also occurring on the 1.3.6 then i feel more reluctant to compile from source.
we are very much aware that this has something to do with the ftp server not supporting TLS 1.3 or the openssl stuff.
My ProFTPD 1.3.6 installation very much does support TLS 1.3, my FileZilla Client 3.40.0 says so:
Protocol: TLS1.3
Cipher: AES-256-GCM
Key exchange: ECDHE-RSA
MAC: AEAD
I suspect that this is not even a ProFTPD thing, but that it rather depends on the OpenSSL libraries available on the system which are used by ProFTPD.
Possibly likewise for FileZilla Client.

So let's just hypothesize for a bit.
If you run both ProFTPD and FileZilla Client on Arch Linux then the issue does not occur.
Maybe "on Arch Linux" can be generalized to "on the same kind of operating system".
Maybe that, in turn, can be generalized to "on operating systems using similar versions of OpenSSL".
Hypothesis: There are problems if the server supports TLS 1.3 but the client only supports TLS 1.2.
sudoranger wrote:
2019-02-09 17:13
@botg mentioned it on the other thread.
Which thread is that?
sudoranger wrote:
2019-02-09 17:13
what do you mean not affected when using OS X? so is this a client's OS problem then? I'm on Windows 10 Pro latest build...
I mean the server is ProFTPD 1.3.6 on Arch Linux.
Me - FileZilla Client 3.40.0 - Arch Linux - not affected
Other user - FileZilla Client 3.40.0 - macOS - affected

The user mentioned that there is a macOS update pending. Maybe this will ship a TLS 1.3-capable version of OpenSSL and fix the problem for said user.

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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#8 Post by boco » 2019-02-10 01:26

FileZilla Client uses GnuTLS, not OpenSSL.
### BEGIN SIGNATURE BLOCK ###
No support requests per PM! You will NOT get any reply!!!
FTP connection problems? Do yourself a favor and read Network Configuration.
All FileZilla products fully support IPv6. http://worldipv6launch.org
### END SIGNATURE BLOCK ###

sudoranger
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#9 Post by sudoranger » 2019-02-10 05:25

eomanis wrote:
2019-02-09 23:33
Which thread is that?
These threads are somewhat related to the same issue we are talking about here.

1. error messages in the latest version

2. GnuTLS error -110: The TLS connection was non-properly terminated. with 3.40-rc2

eomanis
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#10 Post by eomanis » 2019-02-10 16:55

eomanis wrote:
2019-02-09 23:33
The user mentioned that there is a macOS update pending. Maybe this will ship a TLS 1.3-capable version of OpenSSL and fix the problem for said user.
boco wrote:
2019-02-10 01:26
FileZilla Client uses GnuTLS, not OpenSSL.
The user just applied the macOS update but still gets the error.
For the record the user's FileZilla Client says that it is using TLS 1.3.
I also just re-compiled ProFTPD 1.3.6 and the problem still persists. Meh.

Perhaps the macOS FileZilla Client comes with its own GnuTLS library because macOS does not ship GnuTLS?
ProFTPD, for the record, uses OpenSSL via its mod_tls module.
Maybe the GnuTLS library packaged with macOS FileZilla Client 3.40.0 has compatibility issues with OpenSSL 1.1.1.a.

The "filezilla" Arch Linux package depends on the "gnutls" package, which currently is GnuTLS 3.6.6. This indicates that on Arch Linux FileZilla Client uses the GnuTLS of the operating system.
As a reminder, FileZilla Client 3.40.0 on Arch Linux is not affected by the problem, so this might mean that FileZilla 3.40.0 for macOS uses an older GnuTLS version than 3.6.6.

eomanis
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#11 Post by eomanis » 2019-02-10 23:23

eomanis wrote:
2019-02-10 16:55
ProFTPD, for the record, uses OpenSSL via its mod_tls module.
When reading through the TLS module's documentation I found this:

(TLSOptions) EnableDiags
Sets callbacks in the OpenSSL library such that a lot of SSL/TLS protcol information is logged to the TLSLog file. This option is very useful when debugging strange interactions with FTPS clients.

I'm gonna try this one next.

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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#12 Post by boco » 2019-02-11 04:41

I'm not the developer, but, as far as I know, Windows is the only platform where libraries and dependencies are linked statically and generally provided with the package. Linux and Mac use the system libraries provided by the OS.

The current static GnuTLS in the Windows version is also 3.6.6 (as of version 3.40).
### BEGIN SIGNATURE BLOCK ###
No support requests per PM! You will NOT get any reply!!!
FTP connection problems? Do yourself a favor and read Network Configuration.
All FileZilla products fully support IPv6. http://worldipv6launch.org
### END SIGNATURE BLOCK ###

sudoranger
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#13 Post by sudoranger » 2019-02-11 05:25

eomanis wrote:
2019-02-10 23:23
I'm gonna try this one next.
If you have free time, do you mind trying it out on Ubuntu 18.04.1 (or any other distros debian/non-debian based) instead of Arch Linux and tell me the result? I'm not quite sure if this is OS-related. I've read reports on pureftpd and proftpd github issues about TLSv1.3 not working and they are sending a "fallback" PR... I'm still waiting since there's nothing new for the past few weeks... I tried vsftpd and it's also broken as of FZ 3.40 updates.. It was working <=3.39 but @botg said it's the server that is acting up and I can see that too...

manuel
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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#14 Post by manuel » 2019-02-14 11:45

We have tested this now with different ftp clients and proftpd as server. All clients were compiled and run on the same system (updated fedora).

* filezilla linked against gnutls 3.6.5 does not work
* filezilla connected via tlswrap linked against openssl 1.1.1 does work
* lftp linked against gnutls 3.6.5 does work
* lftp linked against openssl 1.1.1 does work

All clients used TLSv1.3 and TLS_AES_256_GCM_SHA384 as cipher. So imho this is either a filezilla or a gnutls issue, although gnutls with lftp works just fine.

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Re: Why do I sometimes/randomly get this "450 Transfer aborted. Link to file server lost" error?

#15 Post by botg » 2019-02-14 13:55

Try using GnuTLS 3.6.6, the same version the official FileZilla binaries are linked against.

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