[ANN] ZnReadEvalPrintDelegate

Ben,

On 16 May 2013, at 20:30, [hidden email] wrote:

  

Very cool.  btw, does the Zinc HTTPS handle client-certificates?  
    

Certificate management in Zodiac TLS/SSL is weak and platform dependent: basically, the primitives are incompletely implemented. This is not an easy subject.

  

That might be reasonably secure if a private tunnel to the box is not available.
    

I can't imagine working with a server unless I can ssh into it, hence

	ssh -L1701:localhost:1701 myserver.com

would be enough to establish the tunnel. But once you are on the host, you can do the curl requests there of course.

As for remote access, Basic Authentication over HTTPS seems sufficient to me, though it isn't perfect. We use this in production for remote web service APIs. Here is how you could set it up:

(ZnSecureServer on: 1443)
	certificate: '/home/sven/ssl/key-cert.pem';
	delegate: ZnReadEvalPrintDelegate new;
	authenticator: (ZnBasicAuthenticator username: '[hidden email]' password: 'Sm@lltalk');
	start.

Alternatively, an Apache or Nginx proxy with client certificates would do the trick as well.

Sven 

  

cheers -ben

Sven Van Caekenberghe wrote:
    

Hi,

Here is a little tool that might be useful to some you. For others it might be a nice example.

So you have your shiny Pharo server application running in the cloud. When something goes wrong, most of the time you will just restart, manually or automatically. But sometimes you wish you could interact with a running headless server image. Problem is, you can't out of the box.

ZnReadEvalPrintDelegate is a simple tool that exports a REPL Web Service. Much like the emergency evaluator. Primitive but better than nothing. Install it on a port of your choice, running in a independent Zn HTTP server, bound to localhost only.

	ZnReadEvalPrintDelegate startInServerOn: 1701.

There is only one API method: POST a plain/text Smalltalk expression to evaluate, get the result back.	

	ZnClient new
		url: 'http://localhost:1701/repl';
		contents: '42 factorial';
		post.

Here is an example terminal session (logged in to the server, not remote):

A GET on the service /repl gives some help text

$ curl http://localhost:1701/repl
# Pharo Smalltalk REPL. POST expressions to evaluate
# Here is one way (type ctrl-d to end input)
curl -X POST -H'Content-Type:text/plain' --data-binary @- http://localhost:1701/repl

A POST with -d is good for short expressions

$ curl -X POST -H'Content-Type:text/plain' -d '42 factorial' http://localhost:1701/repl
1405006117752879898543142606244511569936384000000000

For longer or multi line expressions you can read input from stdin and end with ctrl-d (copy the expression returned by the GET). Or you could send text files.

$ curl -X POST -H'Content-Type:text/plain' --data-binary @- http://localhost:1701/repl
{ (1 to: 10) sum. (1 to: 10) average }
{55. (11/2)}

There is error handling as well:

$ curl -X POST -H'Content-Type:text/plain' --data-binary @- http://localhost:1701/repl
1 plus: 2
MessageNotUnderstood: SmallInteger>>plus:
SmallInteger(Object)>>doesNotUnderstand: #plus:
	Receiver: 1
	Arguments and temporary variables: 		aMessage: 	plus: 2
		exception: 	MessageNotUnderstood: SmallInteger>>plus:
		resumeValue: 	nil
	Receiver's instance variables: 1
UndefinedObject>>DoIt
Compiler>>evaluate:in:to:notifying:ifFail:logged:
Compiler>>evaluate:in:to:notifying:ifFail:
Compiler>>evaluate:in:to:
ZnReadEvalPrintDelegate>>evaluate: in Block: [| result |...
BlockClosure>>on:do:
ZnReadEvalPrintDelegate>>evaluate: in Block: [:out | [| result |...
String class(SequenceableCollection class)>>new:streamContents:

WARNING: never open this service beyond your local network ! This service gives you absolute control over and access to everything in your image. For example, the following will kill your image:

$ curl -X POST -H'Content-Type:text/plain' -d 'Smalltalk quitPrimitive' http://localhost:1701/repl

All this in one class and a handful of methods.

Enjoy,

Sven

PS1: Part of Zinc HTTP Components, in the bleedingEdge version.

PS2: Of course, basic authentication or HTTPS can be added through simple Zn configuration.

--
Sven Van Caekenberghe
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