Hi, Manash
After sending the previous e-mail, I got thinking the following
situation. An admin goes to a deployment which reports a problem. Each
of the deployments
for that admin has the schoolserver address 172.18.96.1. This is the
case for the three schools in Rwanda and also for the three schools in
the Philippines.
Will your technique work to register multiple servers with the same IP?
Tony
On 04/17/2016 03:17 PM, Manash Raja wrote:
Regarding SSH. I think I have found a good solution. (I have tested
it.) Thanks @Tony for telling where exactly the problem occurs.
Commit :
https://github.com/sugarlabs/sugar/pull/679/commits/930726741744ebdf6d464b84b31210aa0897124a
Commit message : ds-backup works independently on its own by using
priave/public key pair and ignoring known_hosts by setting
'StrictHostKeyChecking no'. Problem might arise when other
applications or user try to connect ssh to server without using
private/public key. In that case known_hosts should be maintained to
avoid conflict. Eg scenario: Client ssh into xsce1 on server_address
say schoolserver id1 of xsce1 stored at known_hosts. Client tries for
ssh into xsce2 with same server_address (schoolserver) id2 of xsce2
does not match with id1. Hence error. Solution: If registration is
successful, we know that we have correct server_address of the xsce,
hence we take its identification using 'ssh-keyscan -H -t ecdsa
server_address' and add it to known_hosts. So when ssh is initiated,
the id of the xsce server is found along with its server_address.
It removes the use of "ssh-keygen -R" and hence will be more secured.
It might happen that multiple identification for a particular
server_address is present in the known_hosts file as "schoolserver" is
mostly used as the server address. But ssh will take the one that matches.
On Sun, Apr 17, 2016 at 7:27 AM, Tony Anderson <[email protected]
<mailto:[email protected]>> wrote:
In the current backup system, the only involvement of the user is
to register. The ds-backup script uses the serial-number of the
XO. The 'known_host' check must pass in order for this to work.
Normally, this is not a problem because a given deployed XO only
ever sees one server. It is usually only a problem for the person
setting up multiple deployments (or multiple servers).
Adam Holt apparently contemplates setting up multiple Raspberry Pi
size servers with an SD card for content at a single deployment. I
believe that this environment will not support backup and so there
would be no need to register (except possibly for ejabberd - I
haven't looked at that in years). Possibly HaitiOS should not
execute the ds_backup script. However, if the script fails there
is consequence. What will be required is that each server on a
single network have a unique name to support access by
url:http://schoolserver1, http://schoolserver2, ....
I assume 10.105.57.97 is the IP address of the server. In the
server setup, the server is set as the network gateway and
provides dns translation from
server name to IP. This works with one school server per network
(the norm). In the special case of multiple school servers, one
should supply DHCP services and be the gateway. The other school
servers would need fixed IP addresses. Currently, the school
server is set up as 172.18.96.1 with a netmask of 255.255.224.0.
In this scheme, other school servers could be given fixed
addresses such as 172.18.126.1, 172.18.126.2, .... I have attached
the relevant information from the school server: /etc/dchpd-xs.conf.
Naturally, you can save the IP address if that is more convenient.
The logic of the situation is that a user should keep its Journal
backup on a single school server. The current ds_backup would take
duplicate the same backup on each server. I suppose Sugar could be
modified to specify backup to a designated school server. The
proposed backup would fragment the Journal objects since it would
assume that objects have been backed up and so not make copies on
alternate school servers.
I am sure in Adam's scenario, the SD cards will not afford
complete backups from multiple laptops on each SD card. Most
likely, there would have to be a dedicated server for backup with
an essentially empty card.
On your third question, system adminstrators use ssh. This is not
a problem because access is by password. The server is set up for
ssh xsce-admin@schoolserver
Once logged in, an adminstrator can su to root. This requires two
independent passwords to authenticate.
Tony
On 04/17/2016 05:24 AM, Manash Raja wrote:
Hi,
Here are some updates.*
ssh:* I found from the source code for ds-backup provided by
James http://dev.laptop.org/git/users/quozl/ds-backup/ and while
searching along the lines of Tony (/The script stores and
retrieves using sftp with authentication by public/private key./)
that communication by ds-backup is done using this command:
/usr/bin/ssh -o "PasswordAuthentication no" -o
"StrictHostKeyChecking no" -i ~/.sugar/default/owner.key -l
serial_number server_address
as you all know that ~/.sugar/default/owner.key is the private
key for ~/.sugar/default/owner.key.pub public key. The public key
is sent to the server at the time of registration. The server
adds this public key to
/library/users/serial_number/.ssh/authorized_keys .
I understand that ds-backup don't care about the .ssh/known_hosts
on the client side due to "StrictHostKeyChecking no" even though
the file is getting populated.
So the ssh command is concerned of mainly the public/private key
pair, serial and the server address. If we know the serial of the
laptop that is registered with a server we can connect
successfully with it using the above command. But it might fail
using a normal ssh command due to known_host conflict. If we
assume that all the server communication (sftp and rsync) will
occur using private/public keys, then we don't even need to do
"ssh-keygen -R hostame" or "rm ~/.ssh/known_hosts" I guess.
The issue might have been caused when wrong serial was used to
connect to a server which do not have it registered. Which has
now been fixed in the patch by retaining the serial for previous
registrations.
I have tested that we can add to .ssh/config
Host custom_server_name
HostName 10.105.57.97
PasswordAuthentication no
StrictHostKeyChecking no
IdentityFile ~/.sugar/default/owner.key
User <serial>
and it works by simply calling : ssh custom_server_name
So we can work upon it.
A few doubts:
1. What should be used in custom_server_name?
2. How do we expect our codes to sftp or rsync with server?
ds-backup will run properly in backup if we keep setting the
proper serial. But other than that no application does sftp
or rsync to server, so we can define the proper way now.
3. How do we expect a human user to use ssh? the longer command
or .ssh/config based command? or simply ssh user@server with
constant modifications to known_hosts.
*XSCE vs XS*:
The patch I built uses relies on xs-authserver which is absent in
xs. I really want to add support for XS for this feature. And I
discussed on #schoolserver to know if there is any other way to
get idmgr database info on client side. XS doesn't seem to
support it well enough. I have identified a way to solve this
issues by modifying "registration-server" and "idmanager.py"
scripts of idmgr.
@Jerry
I'm concerned with backwards compatibility, the original
'schoolserver'(XS)
based on CentOS-6 doesn't offer the xs-authserver service,
hence why I
mentioned it. I would not want to break a deployment where
the older server
version is used.
It would not break deployment, as Tony mentioned. The maximum
harm that can be caused is to have multiple registrations for a
single laptop in XS due to inability of XS to provide list of
registered laptops to the client.
A few doubts:
1. Rough percentage of XS against XSCE out there?
2. Scope of modifying idmgr? I am still looking for alternatives
in XS that doesn't need server side modification but till
then I really want to know what are the steps if we finally
need to modify to establish a clear implementation.
3. Even without XS support, the patch solves the issue of taking
the load out of teachers, just that same backup path cannot
be ensured if serial keeps changing. Hence, is this a
significant issue to need a server modification? As if not,
then we can move on and wait until the XS catches up.
@Tony, certainly as you said things can be reorganized starting
from now in small steps so that future features can easily fall
into place. This registration feature may change a component here
and there (like idmgr) but in the progress it might provide a
cleaner and better framework for server related features. (LDAP
being one of them).
Thanks.
On Sat, Apr 16, 2016 at 7:56 AM, Tony Anderson
<[email protected] <mailto:[email protected]>> wrote:
The operative code on the school server is
/usr/libexec/create_user. What Manash describes
is apparently using the db setup by idmgr to list the
registered laptops. I don't think you will
break compatibility.
What I hope we can look at is implementing LDAP as a central
authentication for all of the services which
require a user name, password. Of the top of my head -
Moodle, Khan Academy Lite, OwnCloud, and Elgg.
My brief experience with OwnCloud is that it is a shell
requiring a lot of configuration. I would be interested if TK has
actually deployed it and, if so, how he uses it. I don't know
of any one else who is using it at the moment.
Tony
On 04/16/2016 10:05 AM, Jerry Vonau wrote:
On April 15, 2016 at 6:56 PM Manash Raja
<[email protected] <mailto:[email protected]>> wrote:
@Jerry,
I haven't modified anything for this feature on the
server side. I found
that it uses both idmgr and xs-authserver. But the
5000 port is used by
xs-authserver to display a list of registered
laptops. I didn't enable it
myself, it was there. All I did was to setup my
server according to the
instructions and enabled the "XO register" feature
from the admin page.
I'm concerned with backwards compatibility, the original
'schoolserver'(XS)
based on CentOS-6 doesn't offer the xs-authserver
service, hence why I
mentioned it. I would not want to break a deployment
where the older server
version is used.
@Tony,
Can you tell me how ownCloud is supported by XSCE? I
saw it in the
services
ready to be enabled. So can we not move the storage
location of
/library/user/<some_id> inside or account based user
directories to the
cloud storage locations.
Thanks
The ownCloud service is not enabled out of the box, same
as the
'xo-services'. You can enable it and play around, figure
out how and where
the users' data is stored. Either idmgr or ownCloud could
be altered to
suit the need. Here it would be safe to rely on
xs-authserver's information
as there is no existing implementation of owncloud in
previous releases of
the server software. I can help push the server-side PR's
through.
Jerry
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