Connection leaking by Net::FTP#put (Ruby)
What
The Net::FTP#put doesn’t close FTP data connection when exception occurred.
Even though you call Net::FTP#close, the FTP data connection will not be closed.
$ ruby -v
ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-darwin18]
Why
The Net::FTP#storbinary establish FTP data connection but it not close connection when exception occurred.
# https://github.com/ruby/ruby/blob/00f4c13e22967de1d7e42085b2fc32bf6718f580/lib/net/ftp.rb#L683-L707
def storbinary(cmd, file, blocksize, rest_offset = nil) # :yield: data
if rest_offset
file.seek(rest_offset, IO::SEEK_SET)
end
synchronize do
with_binary(true) do
conn = transfercmd(cmd)
loop do
buf = file.read(blocksize)
break if buf == nil
conn.write(buf)
yield(buf) if block_given?
end
conn.close
voidresp
end
end
rescue Errno::EPIPE
# EPIPE, in this case, means that the data connection was unexpectedly
# terminated. Rather than just raising EPIPE to the caller, check the
# response on the control connection. If getresp doesn't raise a more
# appropriate exception, re-raise the original exception.
getresp
raise
end
Reproduce problem
(1) Launch FTP server
$ docker run --rm \
-p 20-21:20-21 \
-p 21100-21110:21100-21110 \
-e FTP_USER=user \
-e FTP_PASS=pass \
-e PASV_ADDRESS=localhost \
-e PASV_MIN_PORT=21100 \
-e PASV_MAX_PORT=21110 \
fauria/vsftpd
(2) Run script
require 'net/ftp'
def upload
ftp = Net::FTP.new
ftp.read_timeout = 0.1
ftp.passive = true
ftp.connect('localhost')
ftp.login('user', 'pass')
i = 0
ftp.put(__FILE__, '/uploaded', 1) do |data|
i += 1
raise 'Bomb' if i > 3
end
rescue => e
puts e.message
ensure
unless ftp.closed?
ftp.close
puts 'closed.'
end
end
11.times { upload }
puts 'wait'
loop {}
$ ruby -v test.rb
ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-linux]
Bomb
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
Net::ReadTimeout with #<Socket:fd 5>
closed.
500 OOPS: vsf_sysutil_bind, maximum number of attempts to find a listening port exceeded
closed.
wait
(3) Check connection
$ lsof -i:21,21100-21110
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
ruby 31219 koshigoe 7u IPv6 4135154 0t0 TCP localhost:36676->localhost:21106 (ESTABLISHED)
ruby 31219 koshigoe 8u IPv6 4135255 0t0 TCP localhost:46728->localhost:21102 (ESTABLISHED)
ruby 31219 koshigoe 9u IPv6 4137067 0t0 TCP localhost:37788->localhost:21107 (ESTABLISHED)
ruby 31219 koshigoe 10u IPv6 4137128 0t0 TCP localhost:46008->localhost:21108 (ESTABLISHED)
ruby 31219 koshigoe 11u IPv6 4133654 0t0 TCP localhost:39866->localhost:21101 (ESTABLISHED)
ruby 31219 koshigoe 12u IPv6 4133727 0t0 TCP localhost:49142->localhost:21104 (ESTABLISHED)
ruby 31219 koshigoe 13u IPv6 4133784 0t0 TCP localhost:47804->localhost:21109 (ESTABLISHED)
ruby 31219 koshigoe 14u IPv6 4133841 0t0 TCP localhost:46430->localhost:21103 (ESTABLISHED)
ruby 31219 koshigoe 15u IPv6 4135804 0t0 TCP localhost:52886->localhost:21105 (ESTABLISHED)
ruby 31219 koshigoe 16u IPv6 4135854 0t0 TCP localhost:36904->localhost:21100 (ESTABLISHED)
(4) Check process (vsftpd)
sh-4.2# ps aux | grep '[v]sftpd'
root 1 0.1 0.0 11704 2816 ? Ss 09:56 0:00 /bin/bash /usr/sbin/run-vsftpd.sh
root 13 0.0 0.0 53296 3980 ? S 09:56 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 56 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 58 0.0 0.0 75852 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 59 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 61 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 62 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 64 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 65 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 67 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 68 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 70 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 71 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 73 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 74 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 76 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 77 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 79 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 80 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 82 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
nobody 83 0.0 0.0 75752 4584 ? Ss 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf
ftp 85 0.0 0.0 75776 3884 ? S 09:59 0:00 /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf