A solution for public-keyed SFTP and Ruby

[Pau Garcia i Quiles]

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Hello,

Lately there has been some talking here on how to send files using scp. Som=
e=20
people are doing just fine by calling scp with a pre-shared password, but=20
neither I like that approach nor does it work for my purpose, so I did a bi=
t=20
of experimentation and found this code works:

=3D=3D=3D=3D=3D=3D=3D=3D=3D
require 'net/ssh'
require 'net/sftp'

class SSHAgent
def initialize
@agent_env =3D Hash.new
agenthandle =3D IO.popen("/usr/bin/ssh-agent -s", "r")
agenthandle.each_line do |line|
if line.index("echo") =3D=3D nil
line =3D line.slice(0..(line.index(';')-1))
key, value =3D line.chomp.split(/=3D/)
puts "Key =3D #{key}, Value =3D #{value}"
@agent_env[key] =3D value
end
end
end
def [](key)
return @agent_env[key]
end
end

agent =3D SSHAgent.new
ENV["SSH_AUTH_SOCK"] =3D agent["SSH_AUTH_SOCK"]
ENV["SSH_AGENT_PID"] =3D agent["SSH_AGENT_PID"]
system("/usr/bin/ssh-add")

Net::SSH.start( '192.168.1.12',
:username=3D>'pgquiles',
:compression_level=3D>0,
:compression=3D>'none'
) do |session|

session.sftp.connect do |sftp|
sftp.put_file("bigvideo.avi", "bigvideo.avi")
end
end
=3D=3D=3D=3D=3D=3D=3D=3D=3D

I was using a passwordless private key for this experiment. Should you want=
to=20
use a password-protected private key, you might want to set the DISPLAY and=
=20
SSH_ASKPASS environment variables or use a smartcard reader and the '-s=20
reader' parameter.

The SSHAgent class comes from http://paste.lisp.org/display/6912 (I don't k=
now=20
who its author is or the license that code is released under)

Lastly, there is an undesired behaviour in Net::SFTP: when you use the=20
put_file method it loads the whole file in memory, therefore you need loads=
=20
of memory if you want to send big files. I've tried a naive fix (iterating=
=20
writes) but it didn't work (it complains about "no such file", I think it's=
a=20
channels-related issue). Jamis Buck, the author of Net::SFTP, told me=20
currently he has no time to fix this issue. In case you feel brave enough,=
=20
the offending method starts in line 202 in=20
net-sftp-1.1.0/lib/net/sftp/session.rb


=2D-=20
Pau Garcia i Quiles
http://www.elpauer.org
(Due to the amount of work, I usually need 10 days to answer)

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