ssh-sftp-perl-users

[Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[Bryan B. <br...@bu...>]

Greetings, Some time ago I used Net::SSH::Perl, but gave it up for Expect.
 Now I'm back looking at Net::SSH2, but would still like to put expect on
top of it.  I want to use Net::SSH2 because it appears thread safe, while
spawining a process with a tty in expect for perl is not.

What I want to do is create a Net::SSH2 object, connect, get an
interactive shell, and interact with it via a file handle.  Then i can use
expect on top of that and do whatever I like.

I dont fully understand channels, but from what I remember with
Net::SSH::Perl, a new channel had to be created every time you sent a
command.  But now there is a Net::SSH2::Channel->shell() function, perhaps
there is a way to launch a shell on a channel and interact with that?

I see Net::SSH2::Channel is itself a tied filehandle, but attempts to
directly manipulate that dont result in what I expected.

Thanks.

Bryan
http://www.sourceforge.net/projects/rover

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[David R. <dbr...@cp...>]

On Thursday January 19, 2006 09:02, Bryan Bueter wrote:
> Greetings, Some time ago I used Net::SSH::Perl, but gave it up for Expect.
>  Now I'm back looking at Net::SSH2, but would still like to put expect on
> top of it.  I want to use Net::SSH2 because it appears thread safe, while
> spawining a process with a tty in expect for perl is not.
> 
> What I want to do is create a Net::SSH2 object, connect, get an
> interactive shell, and interact with it via a file handle.  Then i can use
> expect on top of that and do whatever I like.
> 
> I dont fully understand channels, but from what I remember with
> Net::SSH::Perl, a new channel had to be created every time you sent a
> command.  But now there is a Net::SSH2::Channel->shell() function, perhaps
> there is a way to launch a shell on a channel and interact with that?

There is.  The shell() function just makes the channel a shell channel, and you can send commands to it.

> I see Net::SSH2::Channel is itself a tied filehandle, but attempts to
> directly manipulate that dont result in what I expected.

In what way?  If you can give details I'll try to fix them.

-- 
Dave
Isa. 40:31

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[Bryan B. <br...@bu...>]

>> I dont fully understand channels, but from what I remember with
>> Net::SSH::Perl, a new channel had to be created every time you sent a
>> command.  But now there is a Net::SSH2::Channel->shell() function,
>> perhaps
>> there is a way to launch a shell on a channel and interact with that?
>
> There is.  The shell() function just makes the channel a shell channel,
> and you can send commands to it.
>

Does this act like a normal shell?  Primarily does it just exec shell and
pass IO back and forth, or is it interpreted somehow?

>> I see Net::SSH2::Channel is itself a tied filehandle, but attempts to
>> directly manipulate that dont result in what I expected.
>
> In what way?  If you can give details I'll try to fix them.
>
> --
> Dave
> Isa. 40:31
>

With this snipit of code:

-- snip -->
use Net::SSH2;
use Expect;

my $ssh2 = Net::SSH2->new();
$ssh2->connect("127.0.0.1");
$ssh2->auth(username => scalar getpwuid($<), interact => 1) or die;

my $chan = $ssh2->channel();
$chan->shell();

my $exp_obj = Expect->exp_init( $chan );
<-- end --

Returns the following when I run the script:
$ ./test.pl
[user username]
Password: ERROR: cannot find method `FILENO' in class Expect at ./test3.pl
line 13

Line 13 is the expect init line.  Maybe its an expect bug, but I dont
think so.  I've been able to open expect on raw sockets before.  So i
think it has something to do with the way channel() sets itself up.

Thanks.

Bryan
http://sourceforge.net/projects/rove

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[David R. <dbr...@cp...>]

On Friday January 20, 2006 03:52, Bryan Bueter wrote:
> >> I dont fully understand channels, but from what I remember with
> >> Net::SSH::Perl, a new channel had to be created every time you sent a
> >> command.  But now there is a Net::SSH2::Channel->shell() function,
> >> perhaps
> >> there is a way to launch a shell on a channel and interact with that?
> >
> > There is.  The shell() function just makes the channel a shell channel,
> > and you can send commands to it.
> 
> Does this act like a normal shell?  Primarily does it just exec shell and
> pass IO back and forth, or is it interpreted somehow?

I think it does act like a normal shell; you'll probably have to test it 
though.  I'm not sure what the ssh spec says regarding the actual shell at 
the other end.

> >> I see Net::SSH2::Channel is itself a tied filehandle, but attempts to
> >> directly manipulate that dont result in what I expected.
> >
> > In what way?  If you can give details I'll try to fix them.
> 
> With this snipit of code:
> 
> -- snip -->
> use Net::SSH2;
> use Expect;
> 
> my $ssh2 = Net::SSH2->new();
> $ssh2->connect("127.0.0.1");
> $ssh2->auth(username => scalar getpwuid($<), interact => 1) or die;
> 
> my $chan = $ssh2->channel();
> $chan->shell();
> 
> my $exp_obj = Expect->exp_init( $chan );
> <-- end --
> 
> Returns the following when I run the script:
> $ ./test.pl
> [user username]
> Password: ERROR: cannot find method `FILENO' in class Expect at ./test3.pl
> line 13
> 
> Line 13 is the expect init line.  Maybe its an expect bug, but I dont
> think so.  I've been able to open expect on raw sockets before.  So i
> think it has something to do with the way channel() sets itself up.

Ah, then there's the problem.  Fileno tries to get a real Unix filehandle out 
of the object; since it isn't a real Unix file, you won't get one.

Maybe something can be worked out with pipes so that it really is a handle 
(create a pipe, send the channel data to one end, give expect the other end) 
but it's beyond the scope of the current implementation.

-- 
Dave
Isa. 40:31

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[Bryan B. <br...@bu...>]

>
> Ah, then there's the problem.  Fileno tries to get a real Unix filehandle
> out
> of the object; since it isn't a real Unix file, you won't get one.
>
> Maybe something can be worked out with pipes so that it really is a handle
> (create a pipe, send the channel data to one end, give expect the other
> end)
> but it's beyond the scope of the current implementation.
>
> --
> Dave
> Isa. 40:31

Ok, forgive me if my ignorance misses something here.

Why not just implement channel as a real filehandle?  You would still do
everything as is, but only now you could create a shell, then print things
directly to and read things directly from it.

Which begets the question: What AM I to do with a shell created by
$chan->shell() ?  Do I have to keep polling this to know when I can write
to it?  I havnt been able to do much with this other then print out the
first couple of lines after it connects.  Printing directly to it and/or
execing on top of shell doesnt seem to produce any more output then that.

An example might be handy, and/or some further documentation.

Thanks.


Bryan
http://sourceforge.net/projects/rover

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[David R. <dbr...@cp...>]

On Friday January 20, 2006 09:22, Bryan Bueter wrote:
> >
> > Ah, then there's the problem.  Fileno tries to get a real Unix filehandle
> > out
> > of the object; since it isn't a real Unix file, you won't get one.
> >
> > Maybe something can be worked out with pipes so that it really is a handle
> > (create a pipe, send the channel data to one end, give expect the other
> > end)
> > but it's beyond the scope of the current implementation.
> 
> Ok, forgive me if my ignorance misses something here.
> 
> Why not just implement channel as a real filehandle?  You would still do
> everything as is, but only now you could create a shell, then print things
> directly to and read things directly from it.

Because it's not a real file.  It's a stream multiplexed over an encrypted 
socket connection formatted by the ssh protocol.  If you read the raw socket 
you'd get ssh frames and encrypted data.

> Which begets the question: What AM I to do with a shell created by
> $chan->shell() ?  Do I have to keep polling this to know when I can write
> to it?  I havnt been able to do much with this other then print out the
> first couple of lines after it connects.  Printing directly to it and/or
> execing on top of shell doesnt seem to produce any more output then that.

You don't exec on top of shell - exec is like exec(2) and doesn't let you run 
subsequent operations.  When you have a shell channel you can send it 
commands and read back the responses using the standard I/O commands in 
Net::SSH2::Channel (or with filehandle ops using the tie).

> An example might be handy, and/or some further documentation.

If you get a chance to write one please submit it for inclusion.

Thanks,

-- 
Dave
Isa. 40:31

Re: [Ssh-sftp-perl-users] Using Net::SSH2 as a file handle

[Bryan B. <br...@bu...>]

>
> Because it's not a real file.  It's a stream multiplexed over an encrypted
> socket connection formatted by the ssh protocol.  If you read the raw
> socket
> you'd get ssh frames and encrypted data.
>

I understand the logistics of the SSH connection, and that writing
directly to the socket is not what i'm suggesting.  I'm not a perl hacker
so i'm sure its more complicated then I think, but I what I had in mind
was, since you already create a tied filehandle that one can use to send
IO to after a shell channel is created, why not create a real file handle.

I'll take your previous response as, its way more complicated then I
think, and consider it out of scope.  Unless that explanation somehow
makes a difference.

>
> You don't exec on top of shell - exec is like exec(2) and doesn't let you
> run
> subsequent operations.  When you have a shell channel you can send it
> commands and read back the responses using the standard I/O commands in
> Net::SSH2::Channel (or with filehandle ops using the tie).
>

Yeah, I was having problems actually using a shell channel, i was trying
anything.  So noted.

>> An example might be handy, and/or some further documentation.
>
> If you get a chance to write one please submit it for inclusion.
>
> Thanks,
>
> --
> Dave
> Isa. 40:31

I'll let you know about an example/documentation.  I'll be messing with it
over the next week or so as I have free time, If I come up with something
I'll submit it for your review.

Thanks,

Bryan
http://sourceforge.net/projects/rover