error reading response: unexpected EOF while storing a 0 file size using TLS

[ior308]

Dear,

opening a local file of 0 bytes and storing to vsftpd via TLS, I got this error:

error reading response: unexpected EOF

Without TLS it works well. Any Idea ?

Best regards

[ior308]

Here the output vsftpd side:
Tue Nov 8 08:27:04 2022 [pid 351212] CONNECT: Client "::ffff:192.168.1.122"
Tue Nov 8 08:27:04 2022 [pid 351212] FTP response: Client "::ffff:192.168.1.122", "220 (vsFTPd 3.0.3)"
Tue Nov 8 08:27:04 2022 [pid 351212] FTP command: Client "::ffff:192.168.1.122", "AUTH TLS"
Tue Nov 8 08:27:04 2022 [pid 351212] FTP response: Client "::ffff:192.168.1.122", "234 Proceed with negotiation."
Tue Nov 8 08:27:04 2022 [pid 351212] FTP command: Client "::ffff:192.168.1.122", "USER root"
Tue Nov 8 08:27:04 2022 [pid 351212] [root] FTP response: Client "::ffff:192.168.1.122", "331 Please specify the password."
Tue Nov 8 08:27:04 2022 [pid 351212] [root] FTP command: Client "::ffff:192.168.1.122", "PASS "
Tue Nov 8 08:27:04 2022 [pid 351211] [root] OK LOGIN: Client "::ffff:192.168.1.122"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "230 Login successful."
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "PBSZ 0"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "200 PBSZ set to 0."
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "PROT P"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "200 PROT now Private."
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "FEAT"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "211-Features:"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " AUTH TLS\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " EPRT\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " EPSV\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " MDTM\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " PASV\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " PBSZ\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " PROT\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " REST STREAM\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " SIZE\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " TVFS\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", " UTF8\x0D\x0A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "211 End"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "TYPE A"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "200 Switching to ASCII mode."
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "PASV"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "227 Entering Passive Mode (192,168,1,122,190,143)."
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP command: Client "::ffff:192.168.1.122", "STOR msg-dst.txt"
Tue Nov 8 08:27:04 2022 [pid 351216] [root] FTP response: Client "::ffff:192.168.1.122", "150 Ok to send data."

[ior308]

And here some debug I added while storing client side, when does not work and when works (without TLS):

7 220 (vsFTPd 3.0.3)
7 234 Proceed with negotiation.
7 331 Please specify the password.
7 230 Login successful.
7 200 PBSZ set to 0.
7 200 PROT now Private.
7 211 Features:
AUTH TLS
EPRT
EPSV
MDTM
PASV
PBSZ
PROT
REST STREAM
SIZE
TVFS
UTF8
End
7 200 Switching to ASCII mode.
7 227 Entering Passive Mode (192,168,1,122,190,143).
7 150 Ok to send data.
io.Copy: 0
7 0 error reading response: unexpected EOF
6 0 0 error reading response: unexpected EOF
4: error reading response: unexpected EOF
panic: error reading response: unexpected EOF

---

7 220 (vsFTPd 3.0.3)
7 331 Please specify the password.
7 230 Login successful.
7 211 Features:
EPRT
EPSV
MDTM
PASV
REST STREAM
SIZE
TVFS
UTF8
End
7 200 Switching to ASCII mode.
7 227 Entering Passive Mode (192,168,1,122,186,107).
7 150 Ok to send data.
io.Copy: 0
7 226 Transfer complete.
8

[ior308]

With TLS, it seems that io.copy of zero bytes is ignored. Adding a fake write of zero it works ?!

transfer.go
...

func (c *Client) transferFromOffset
...
n, err := io.Copy(dest, src)
dest.Write([]byte{})

..