Thanks Felix,
Glad you like my idea. Since ajaxterm runs its own web server (and
you can specify the port is listens on, which would be one per customer), I
think it's just a matter of using php to control access to this resource.
Another, easier way, would be to just use Apache's .htaccess stuff
(No sessions required). Just protect one directory per user, and in each
directory simply have an index.php that runs the correct ajaxterm command for
the user. Then Apache could use it's reverse proxy mechanism to give the user
access to ajax term. The "logical" address of the ajax term would be a child of
the inital htaccess protected directory. This isn't as nice and doesn't scale
well, but I'm pretty sure it would work..
From: Felix Kuperjans
[mailto:felix@xxxxxxxxxxxxxxxxxx]
Sent: Fri 18/06/2010
15:25
To: Jonathan Tripathy
Cc:
xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Web Console
Access
Hi Jonathan, I think this is a great idea: The Domain-0 has full
SSH-security (can be limited to your webserver's internal ip address for further
security) and the webserver is not running on Dom0. You could combine this
approaches: SSH on Dom0, with RSA authentification and (for example)
sudo-wrapped xm console, accessed by your ajaxterm software. It would be even
possible to provide both methods to your customers, if the SSH daemon is secured
enough, or just allow that web console. When the web console is secure enough,
this will not expose any security threats to your customers, and it would never
be a threat to your Dom0s. You'll need to ask the ajaxterm developers, I only
know that many PHP session ids are *not* safely generated and ajax can even
extend that problem (on the other hand, suhosin fixes that problem). SSH's
HMAC-method is more safe, but many applications rely on PHP's safety (some of
them without being hacked), so it would offer enough security if the application
has no big security issues. Regards, Felix Am 18.06.2010 16:09,
schrieb Jonathan Tripathy:
Hi Felix,
What I was thinking of doing (And i'll need to consult with my
php/java folk here to get this working in a secure way), is to run Ajaxterm on
the web server itself. When launch Ajaxterm, there is a -c option that allows
you to specify a command. With an ssh key stored in the web
server's filesystem (Which only is allowed to preform global xm
functions), I could do something like (The command would run locally on the
web server):
Where $vm_id could be storaed in a database and would be the name
of the DomU running
What you think?
Hi Jonathan, if you can do that, it's good. But you'll always need
some kind of access to the Dom0 to get the console data and to reboot / reset
/ rescue the VMs (whatever you want to offer to your
customers). Regards, Felix Am 18.06.2010 15:17, schrieb
Jonathan Tripathy:
Hi Felix,
Probably the main reason why I want to use a web console is so
that I can run the web server on a different machine (Or maybe in a VM
connected to an isolated network).
Thanks for the tip on the Grub password for the Dom0. That's
scary about the KVM!
Thanks
Jonathan
Hi Jonathan, the Dom0 cannot be compromised as long as your SSH
or web-based console does not have any security leaks. PHP sessions are
not as secure as SSH, but with SSL and suhosin patched PHP considerably
OK. As I said, I don't use web-based consoles so I can't help you
there, but I'd *really* consider whether it is a good thing to setup a
webserver on a Dom0 and it may be probably hard to do web-based consoles
without that. Regards, Felix P.S. Anyway, considering the
method I posted, you should always setup GRUB and BIOS passwords for all of
your Dom0s. I once requested KVM access at my provider and ended up at the
wrong server... Am 18.06.2010 15:03, schrieb Jonathan Tripathy:
Hi Felix,
I actually have that guy's book who wrote that article - The
book of Xen - very good book indeed!
What I really wish to do, is provide a similar sort of thing
to that SSH setup, except allow it to be accessed via a web browser. I
have an idea where I can use ajaxterm and some PHP scripting. Once a user
logs on with a username and password, I could tell php to start ajaxterm
and piple xm console through it. This is what Slicehost does I think. The
console would be protected with php sessions.
But my main worry was whether or not the Dom0 could be
compramised via the above method, but I don't think that's the case.
Thanks
Jonathan
Hi Jonathan, this is a common way to reset lost / forgotton
root passwords: You need: - Physical access to a machine (if you
want to reset the password of the Dom0 or a native linux) or console
access to a DomU - Access to the kernel command line, via lilo, grub or
pygrub/pvgrub in XEN Then you do: - Modify the kernel command
line, add the init=/bin/bash option, for example: kernel
/linux-2.6.32.15-xen root=/dev/xvda2 init=/bin/bash - You'll directly
end up in a root console without password or any services started after
the kernel booted - enter those commands: mount -o remount,rw
/ passwd root <enter new password> exec
/sbin/init The root password will then be the newly set
one. DomUs generally are not vulnerable to this method, as long as
the kernel command line is set in the domain configuration. But
pygrub/pvgrub is a nice thing for hosting customers, because they can
compile their own kernels, containing their preferred settings, modules
and builtin functionality. Generally this problem is avoided by adding a
password to grub, but some customers may forget that step. So physical
access can always be a strong weapon, but it is necessary for repairing a
machine or for some advanced setups (especially when setting up a
firewall, one easily gets locked out of the server...). I think the best
way is securing this access, by restricting virtual console access to
highly encrypted and authenticated sessions (IMHO the best way is SSH
here). I'd also think about customers forgetting to log out,
because leaving xm console does *not* logout root inside the
console. The tutorial I posted to your I/O question contains a
SSH-based setup for xm console access with sudo, which may be nice to
start with. I personally use an own wrapper inside a chroot jail, to
provide the ability of entering commands like create / rescue / setup
(rescue starts another domain configuration with NFS root + rescue-Kernel,
setup starts a virtual Debian setup). It's quite handy for VPS
customers. Regards, Felix Am 18.06.2010 14:26, schrieb
Jonathan Tripathy:
Hi Felix,
Thanks for the email.
>a simple init=/bin/bash added to the kernel command
line allows resetting the root password...
ok this worries me. Can
you please explain this a little further? Do you need to have access to
the Dom0 to begin with?
Thanks
Hi Jonathan, do you definitely need a web console (so really
browser-based) or would you consider a SSH-based console? I
personally prefer SSH because it is more secure, easier to set up and it
is somehow the default way of accessing remote consoles. You can do a
modified SSH setup that only allows access to the console, or
optionally, access to xm console, xm list, xm shutdown, xm create but
restricted to the own VM of your customer. With chroot-jails etc., other
commands cannot be executed. SSH also has the advantage of good copy
& paste of larger commands, and the possibility to work with
multiple client certificates and / or passwords. Probably your
administrative interface allows uploading of multiple public keys, so
that your customers can have multiple adminsitrative accounts for the
server (but only one can access the console at a time). I've got
no experiences with ajaxterm, but you should really control its
security: Console access is quite useful for hackers, e.g. some
customer may forget to log out root or if you use pvgrub / pygrub, a
simple init=/bin/bash added to the kernel command line allows resetting
the root password... So it must be a really secure application, not
vulnerable to XSS, SQL Injections, Connection hijacking, ... and SSL
encrypted. Regards, Felix Kuperjans Am 18.06.2010
13:02, schrieb Jonathan Tripathy:
Hi Everyone,
Does anyone have any idea on how to give my customers a
"web console" for their VMs?
Using http://antony.lesuisse.org/software/ajaxterm/ I
can manually set up a remote session for them, by doing ajaxterm.py -c xm console <DOMNAME> However is there any way to make this automatic? Maybe I could put it in the vif script? Thanks
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