JS - Add the basic architecture to be able to execute embedded js #12432

calixteman · 2020-10-01T12:16:52Z

As a first step, we (mozilla) want to execute safely the embedded javascript for the PDF.js embedded in Firefox.
A second step will be to add a sandbox for the webextension version.
So, in order to accomplish the first step, there is a patch in review on m-c:
https://phabricator.services.mozilla.com/D91746
to add a sandbox with no privileges to eval js.
And here's the basic stuff to use it.
I implemented only few things to be able to test using the form:
https://www.guidedesimpots.lu/wp-content/uploads/2019/02/160F-2019.pdf
which has basic actions to format correctly numbers (with 2 digits).
Few explanations:

all the Field objects, app, console, ... live in the sandbox it's why some js code is generated in scripting_api/code_gen.js and used to init the sandbox. All the intermediary stuff which is not in the api shouldn't be accessibe.
all the objects available (Field, app, ...) are wrapped in a proxy (see scripting_api/proxy.js) in order to control the access to different properties: all the properties starting with a _ are private.
the script may add some properties starting a _, the proxy handle that in adding them in the _expandos property (see scripting_api/pdf_object.js)
all the generated code use class.toString method which mean that we've the true objects and we can easily test them in pdf.js
and we can easily test the behaviour of the objects in eval the generate code.

In order to achieve the second step, we plan to use quickjs (/~https://github.com/yurydelendik/quickjs) compiled with emscripten but of course any other good solution is welcome.

web/app.js

web/firefoxcom.js

src/scripting_api/error.js

src/scripting_api/code_gen.js

src/scripting_api/pdf_object.js

src/pdf.scripting_api.js

calixteman · 2020-10-15T15:32:28Z

This patch is ready for review and is probably the more import piece.
Once it's merged we'll ask for a review of the patch to create the Sandbox on firefox's side.

timvandermeij

I had a quick first look, but it's a lot to oversee. I would really want to suggest to either cut this PR up in much smaller chunks with links to the relevant specifications, or remove a lot of the now unused parts (all the stubs, et cetera) because as-is it's quite hard to review due to the large number of properties, methods, et cetera.

Aside from that, the general approach seems OK to me.

timvandermeij · 2020-10-15T21:43:10Z

gulpfile.js

@@ -1244,7 +1244,7 @@ function buildLib(defines, dir) {
  return merge([
    gulp.src(
      [
-        "src/{core,display,shared}/*.js",
+        "src/{core,display,scripting_api,shared}/*.js",


I'm not sure about creating another folder for this since the folder structure as-is was carefully chosen to indicate if code is exclusively for the core/display layers or is shared. It looks like the scripting code is shared? If so, maybe move the directory inside the shared directory, and maybe call it scripting instead to avoid confusion with the normal PDF.js API? I'd like to also hear other opinions before doing this.

I think a separate folder is good here. Though I'm leaning towards us not including these files in the bundled pdf.js file. That's going to make pdf.js file grow and the forms scripting api will have to be parsed regardless if it is used and it will not actually be used in the regular js context. Can we bundle them into a separate file and just load it as text since we're eval'ing it anyway?

timvandermeij · 2020-10-15T21:49:15Z

src/scripting_api/aformat.js

+ * limitations under the License.
+ */
+
+class AFormat {


Where does the name AFormat come from? Is it in a specification somewhere?

I was tired when I changed that...
So the "correct" name is AForm because all theses functions lived in a file (distributed with Acrobat few years ago) called AForm.js (see http://www.sfu.ca/~wcs/ForGraham/Aladdin%20stuff/Acrobat%20Reader%205.0/Contents/MacOS/JavaScripts/AForm.js).
There's no real documentation about those: only few indications here https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/FormsAPIReference.pdf#page=119.
In pdfium, these functions are implemented in a file called cjs_publicmethods.cpp.
So I guess the specifications are the code itself as found in AForm.js.
I implemented them here:
/~https://github.com/calixteman/pdf.js/blob/sandbox_experimental/src/scripting_api/aformat.js
but it's for an other PR.

timvandermeij · 2020-10-15T21:49:46Z

src/scripting_api/aformat.js

+    this._util = util;
+  }
+
+  AFNumber_Format(


Same question here: this seems like an odd name. Why is it named like this? And are those parameters documented somewhere (since bCurrencyPrepend does not seem to be used)?

See my answer above.
About the current implementation: it's just a very basic one.
My goal here with this PR is just to set up the basis and so I implemented it quickly to have something which works.

src/scripting_api/app.js

src/scripting_api/publics.js

src/scripting_api/scripting.js

web/app.js

src/display/annotation_layer.js

calixteman · 2020-10-16T14:32:30Z

I fixed the first nits and remove all the stubs.
Be aware that I've a lot of other PRs to do: my current work is here /~https://github.com/calixteman/pdf.js/tree/sandbox_experimental/src/scripting_api

brendandahl · 2020-10-16T19:59:51Z

gulpfile.js

@@ -1244,7 +1244,7 @@ function buildLib(defines, dir) {
  return merge([
    gulp.src(
      [
-        "src/{core,display,shared}/*.js",
+        "src/{core,display,scripting_api,shared}/*.js",


I think a separate folder is good here. Though I'm leaning towards us not including these files in the bundled pdf.js file. That's going to make pdf.js file grow and the forms scripting api will have to be parsed regardless if it is used and it will not actually be used in the regular js context. Can we bundle them into a separate file and just load it as text since we're eval'ing it anyway?

src/scripting_api/code_gen.js

timvandermeij

It's looking more manageable than before, so thank you for doing that.

src/pdf.js

src/scripting_api/app.js

src/scripting_api/field.js

src/scripting_api/util.js

brendandahl · 2020-10-22T22:06:29Z

/botio-linux test

pdfjsbot · 2020-10-22T22:06:31Z

From: Bot.io (Linux m4)

Received

Command cmd_test from @brendandahl received. Current queue size: 0

Live output at: http://54.67.70.0:8877/e61da9e6dfeb09c/output.txt

pdfjsbot · 2020-10-22T22:33:00Z

From: Bot.io (Linux m4)

Failed

Full output at http://54.67.70.0:8877/e61da9e6dfeb09c/output.txt

Total script time: 26.48 mins

Font tests: Passed
Unit tests: Passed
Regression tests: FAILED

Image differences available at: http://54.67.70.0:8877/e61da9e6dfeb09c/reftest-analyzer.html#web=eq.log

brendandahl · 2020-10-23T00:10:24Z

/botio-windows test

brendandahl · 2020-10-23T00:12:34Z

/botio-windows test

pdfjsbot · 2020-10-23T00:12:36Z

From: Bot.io (Windows)

Received

Command cmd_test from @brendandahl received. Current queue size: 0

Live output at: http://54.215.176.217:8877/b1d497fd614b74f/output.txt

Snuffleupagus requested changes Oct 1, 2020

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JS - Add the basic architecture to be able to execute embedded js

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brendandahl approved these changes Oct 23, 2020

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brendandahl merged commit 1eaf9c9 into mozilla:master Oct 23, 2020

nmtigor mentioned this pull request Sep 20, 2022

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JS - Add the basic architecture to be able to execute embedded js #12432

JS - Add the basic architecture to be able to execute embedded js #12432

calixteman commented Oct 1, 2020

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JS - Add the basic architecture to be able to execute embedded js #12432

JS - Add the basic architecture to be able to execute embedded js #12432

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