December | 2011 | Binarymist

Archive for December, 2011

OpenSSH from Linux to Windows 7 via tunneled RDP

December 27, 2011

I recently acquired a new second hand Asus laptop from my work,
that will be performing a handful of responsibilities on one of my networks.

This is the process I took to set up OpenSSH on Cygwin running on the Windows 7 box.

I won’t be going over the steps to tunnel RDP as I’ve already done this in another post

Make sure your LAN Manager Authentication Level is set as high as practical.
Keeping in mind, that some networked printers using SMB may struggle with these permissions set to high.

Windows Firewall -> Allowed Programs -> checked Remote Desktop.
System Properties -> Remote tab -> turn radio button on to at least “Allow connections from computers running any version of Remote Desktop”
If you like, this can be turned off once SSH is set-up, or you can just turn the firewall rule off that lets RDP in.

CopSSH which I used on my last set of Linux to Windows RDP via SSH set-ups is no longer free.
So I’m not paying for something I can get for free, but with a little extra work involved.

So I looked at some other Windows SSH offerings

freeSSHd which looked like a simple set-up, but it didn’t appear to be currently maintained.
OpenSSH the current latest version of 5.9 released September 6, 2011
A while back OpenSSH wasn’t being maintained. Looks like that’s changed.

OpenSSH is part of Cygwin, so you need to create a
c:\cygwin directory and download setup.exe into it.

Right click on c:\cygwin\setup.exe and select “Run as Administrator”.
Click Next.
If Install from Internet is not checked, check it. Then click Next.
Accept the default “Root Directory” of C:\cygwin. Accept the default for “Install For” as All Users.
Accept the default “Local Package Directory” of C:\cygwin.
Accept the default “Select Your Internet Connection” of “Direct Connection”. Click Next.
Select the closest mirror to you. Click Next.
You can expand the list by clicking the View button, or just expand the Net node.
Find openssh and click the Skip text, so that the Bin check box for the item is on.
Find tcp_wrappers and click the Skip text, so that the Bin check box for the item is on.

If you selected tcp_wrappers and get the “ssh-exchange-identification: Connection closed by remote host” error,
you’ll need to edit /etc/hosts.allow and add the following two lines before the PARANOID line.

ALL: 127.0.0.1/32 : allow
 ALL: [::1]/128: allow

These lines were already in the /etc/hosts.allow

(optional) find the package “diffutils”, click on the word “skip” so that an x appears in Column B,
find the package “zlib”, click on the word “skip” (it should be already selected) so that an x appears in Column B.

Click Next to start the install.
Click Next again to… Resolving Dependencies, keep default “Select required packages…” checked.
At the end of the install, I got the “Program compatibility Assistant” stating… This program might not have installed correctly.
I clicked This program installed correctly.

Add an environment variable to your Systems Path variable.
Edit the Path and append ;c:\cygwin\bin

Right click the new Cygwin Terminal shortcut and Run as administrator.
Make sure the following files have the correct permissions.

/etc/passwd -rw-r–r–
/etc/group -rw-r–r–
/var drwxr-xr-x

Create a sshd.log file in /var/log/

touch /var/log/sshd.log
chmod 664 /var/log/sshd.log

Run ssh-host-config

Cygwin will then ask Should privilege separation be used? Answer Yes
Cygwin will then ask Should this script create a local user ‘sshd’ on this machine? Answer Yes
Cygwin will then ask Do you want to install sshd as service? Answer Yes
Cygwin will then ask for the value of CYGWIN for the daemon: []? Answer ntsec tty
Cygwin will then ask Do you want to use a different name? Answer no
Cygwin will then ask Please enter a password for new user cyg_server? Enter a password twice and remember it.

replicate your Windows user credentials with cygwin

mkpasswd -cl &gt; /etc/passwd
mkgroup --local &gt; /etc/group

I think (although I haven’t tried it yet) when you change your user password, which you should do regularly,
you should be able to run the above 2 commands again to update your password.
As I haven’t done this yet, I would take a backup of these files before I ran the commands.

to start the service, type the following:

net start sshd

Test SSH

ssh localhost

When you make changes to the /etc/sshd_config,
because it’s owned by cyg_server, you’ll need to make any changes as the owner.
I added the following line to the end of the file:

Ciphers blowfish-cbc,aes128-cbc,3des-cbc

As it sounds like Blowfish runs faster than the default AES-128

There are also a collection of changes to be made to the /etc/sshd_config

for example:

Change the LoginGraceTime to as small as possible number.
PermitRootLogin no
Set PasswordAuthentication to no once you get key pair auth set-up.
PermitEmptyPasswords no
You can also setup AllowUsers and DenyUsers.

The options available are here in the man page (link updated 2013-10-06).
This is also helpful, I used this for my CopSSH setup.

Open firewalls TCP port 22 and close the RDP port once SSH is working.

As my blog post says:
ssh-copy-id MyUserName@MyWindows7Box

I already had a key pair with pass phrase, so I used that.
Now we should be able to ssh without being prompted for a password, but instead using key pair auth.

The links I found helpful:

http://pigtail.net/LRP/printsrv/cygwin-sshd.html
http://www.petri.co.il/setup-ssh-server-vista.htm
http://www.scottmurphy.info/open-ssh-server-sshd-cygwin-windows

Tags:Linux, Networking, OpenSSH, Security, SSH
Posted in GNU/Linux, Microsoft, Networking, Security, SSH | 2 Comments »

JavaScript Reserved Words

December 19, 2011

Funnily enough, most of these are not used in the language.
They cannot be used to name variables or parameters.
In saying that,
I did some testing below and that statement’s not entirely accurate.

Usage of keywords in red should be avoided.

Reserved	Keyword	Comments
abstract	no
boolean	no
break	yes
byte	no	No type of byte in JavaScript
case	yes
catch	yes
char	no	JavaScript doesn’t have char. Use string instead
class	no	technically JavaScript doesn’t have class
const	no	no const, but read-only can be implemented
continue	yes
debugger	yes
default	yes
delete	yes
do	yes
double	no	JavaScript only has number (64 bit floating point)
else	yes
enum	no
export	no
extends	no
false	yes
final	no
finally	yes
float	no	JavaScript only has number (64 bit floating point)
for	yes
function	yes
goto	no
if	yes
implements	no	JavaScript uses prototypal inheritance. Reserved in strict mode
import	no
in	yes
instanceof	yes
int	no	JavaScript only has number (64 bit floating point)
interface	no	technically no interfaces, but they can be implemented. Reserved in strict mode
let	no	Reserved in strict mode
long	no	JavaScript only has number (64 bit floating point)
native	no
new	yes	use in moderation. See comments in Responses below
null	yes
package	no	Reserved in strict mode
private	no	access is inferred. Reserved in strict mode
protected	no	JavaScript has privileged, but it’s inferred. Reserved in strict mode
public	no	access is inferred. Reserved in strict mode
return	yes
short	no	JavaScript only has number (64 bit floating point)
static	no	Reserved in strict mode
super	no
switch	yes
synchronized	no
this	yes
throw	yes
throws	no
transient	no
true	yes
try	yes
typeof	yes
var	yes
volatile	no
void	yes
while	yes
with	yes
yeild	no	Reserved in strict mode

–

When reserved words are used as keys in object literals,
they must be quoted.
They cannot be used with the dot notation,
so it is sometimes necessary to use the bracket notation instead.
Or better, just don’t use them for your names.

var method;                  // ok
var class;                   // illegal
object = {box: value};       // ok
object = {case: value};      // illegal
object = {'case': value};    // ok
object.box = value;          // ok
object.case = value;         // illegal
object['case'] = value;      // ok

–

I noticed in Doug Crockfords JavaScript The Good Parts
in Chapter 2 under Names, where he talks about reserved words.
It says:
“It is not permitted to name a variable or parameter with a reserved
word.
Worse, it is not permitted to use a reserved word as the name of an object
property in an object literal or following a dot in a refinement.”

I tested this in Chrome and FireFox with the following results.

var private = 'Oh yuk'; // if strict mode is on: Uncaught SyntaxError: Unexpected strict mode reserved word
var break = 'break me'; // Uncaught SyntaxError: Unexpected token break

var myFunc = function (private, break) {
   // if strict mode is on or off: Uncaught SyntaxError: Unexpected token break
   // strangly enough, private is always fine as a parameter.
}

var myObj = {
   private: 'dung', // no problem
   break: 'beetle' // no problem
}
console.log('myObj.private: ' + myObj.private) // myObj.private: dung
console.log(' myObj.break: ' + myObj.break); // myObj.break: beetle

JavaScript also predefines a number of global variables and functions
that you should also avoid using their names for your own variables and functions.
Here’s a list:

arguments
Array
Boolean
Date
decodeURI
decodeURIComponent
encodeURI
encodeURIComponent
Error
eval
EvalError
Function
Infinity
isFinite
isNaN
JSON
Math
NaN
Number
Object
parseFloat
parseInt
RangeError
ReferenceError
RegExp
String
SyntaxError
TypeError
undefined
URIError

Tags:JavaScript, Scripting
Posted in JavaScript, Scripting, Uncategorized, Web | 2 Comments »

DVCS vs CVCS

December 3, 2011

Some differences between Distributed Version Control Systems (DVCS) and Centralised Version Control Systems (CVCS)

The central server dilemma

I hear a number of people being fearful about what they hear about DVCS not having a central repository.
In most cases this is not entirely true.
There are a number of DVCS models that work very well utilising one or more central servers.
In fact all the DVCS I’ve worked with or set-up have used one or more central repositories.

One of the key differences between Distributed and Centralised.
Is with distributed, the authoritative or central source is the source you want it to be, rather than being constrained by the system into having to have your source in one place.
There has been occasions where we have had to use one of the developers local repositories when the central server has been down.
This is simply making a decision that the entire team is aware of, that you are going to push / pull to / from an alternative repository.
Hg has it’s own inbuilt web server, so this is very easy to do.

One of the big advantages with a DVCS is the flexibility.
With increased flexibility and power, comes the increased likelihood of someone screwing something up.
Personally I’d much rather have the extra flexibility.

Branching Merging

Is easy and encouraged in DVCS.
DVCS are designed with branching and merging to be a common task.
Therefore they do it well, and some of the paranoia around this concept is no longer justified when you go distributed.

Mercurial (Hg) vs Git commits

Both Hg and Git are distributed.
Git has this extra step between your working directory and your repository called the Index (strangely enough)
All changes in git go into a staging area, then into your repository.
The index is used to combine a set of changes that you want to commit as one operation.
When you commit, what is committed is the contents of your index rather than your working directory.

The idea of the index, is that some of the history is erased once a commit is made, as multiple changes and their details are wrapped into a single commit.
There is a philosophical debate as to which way is better.
Is it better to have every change recorded, or is it better to have a bunch of changes wrapped into an atomic change, so that some detail is negated.
I’m kind of on the fence about this one, as I think there are pros and cons for both arguments.

Interfacing with Hg and Git for Windows users

There are currently several options here.

command line

file explorer

TortoiseHg
TortoiseGit
GitExtensions for Explorer and Visual Studio integration

For Visual Studio users

Tags:distributed version control, hg, mercurial
Posted in GNU/Linux, Microsoft, Version Control | 3 Comments »

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