Using a Trusted Certificate (from QZ-Print) in an angular 7 app

[Harry Whitehouse]

And I have some test code which works very nicely to test reading a USB scale. It's in the  ngOnInit() section of a particular component.  This works fine, although the security dialog pops up 3 times as each function is called.

  qz.websocket.connect().then(function() {

          let deviceInfo = {"vendorId" : "0x0d8f", "productId" : "0x0200",  "usagePage" : "0x008d"};

          return qz.hid.claimDevice(deviceInfo);

        }).then(function() {

           //console.log("scale device claimed!!");

        }).then(function() {

          let deviceInfo = {"vendorId" : "0x0d8f", "productId" : "0x0200",  "usagePage" : "0x008d", "responseSize" : 20};

          return qz.hid.readData(deviceInfo);

        }).then(function(data) {

           console.log(data);       

       // }).then(function() {

       //   return qz.websocket.disconnect();

       }).catch(function(err) {

          console.error(err);

       }); 

Because I purchased premium support, I was able to use this https://qz.io/wiki/generate-certificate as a guide and quick generate my private & public key along with the signed certificate on the QZ website (very slick BTW).

But now I'm a bit confused on how and where to add this cryptographic subsystem.

1.  When the trusted certificate is properly installed, does it just popup once for a given browser session?  Suppose I move back and forth to other components/pages?  Or will the "allow" feature stay enabled between sessions provides cookies are not cleared?

2.  Am I correct in assuming that all the required keys and certs are installed as part of the Angular code and does not involve the server-side?  I plan to monitor a local USB scale and print label ZPL payload  which is received from our server to a local printer  So I'm assuming that I don't need to install any of the QZ crypto on in our docker containers or any other server-based systems.  

3.  It appears like I would add the code below ahead of my code above with this format:

qz.security.setCertificatePromise(function(resolve, reject) {

    $.ajax({ url: "path/to/digital-certificate.txt", cache: false, dataType: "text" }).then(resolve, reject);

});

where my path might reflect my project directory, e.g. app/assets/certs/digital-certification.txt.

I am a bit confused about the $.ajax -- I haven't used any ajax libraries in Angular thus far -- I suspect they are more known to JS programmers.

Let me stop here before moving on to Signatures. 

Thanks for reading!

Harry

[Tres Finocchiaro]

1.  When the trusted certificate is properly installed, does it just popup once for a given browser session?  Suppose I move back and forth to other components/pages?  Or will the "allow" feature stay enabled between sessions provides cookies are not cleared?

The "Always allow" won't be affected by cleared cookies, it's stored on the client in %appdata%\qz (or OS equivalent)

If you use the "qz:launch" URI, that will be affected by cookies.  That is a technique to launch QZ Tray from a browser link.  The "Remember" checkbox is generally cleared with the cookies.

 

2.  Am I correct in assuming that all the required keys and certs are installed as part of the Angular code and does not involve the server-side?  I plan to monitor a local USB scale and print label ZPL payload  which is received from our server to a local printer  So I'm assuming that I don't need to install any of the QZ crypto on in our docker containers or any other server-based systems.  

Certificate: 100% JavaScript

Signature:  Prefered to be back-end to avoid private-key theft but client-side JavaScript is also supported.  We use jsrsasign library for it in JS.

 

3.  It appears like I would add the code below ahead of my code above with this format:
qz.security.setCertificatePromise(function(resolve, reject) {
    $.ajax({ url: "path/to/digital-certificate.txt", cache: false, dataType: "text" }).then(resolve, reject);
});
where my path might reflect my project directory, e.g. app/assets/certs/digital-certification.txt.
I am a bit confused about the $.ajax -- I haven't used any ajax libraries in Angular thus far -- I suspect they are more known to JS programmers.

It's a jQuery function.  You can use fetch(...) or XHR instead if you'd like.  fetch(...) wasn't common when the API was written.  We may incorporate it in a future version to avoid unnecessary jQuery confusion.

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