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Specify validation of share_target at manifest load time. #28

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Specify validation of share_target at manifest load time. #28

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94 changes: 90 additions & 4 deletions index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -164,9 +164,9 @@ <h2>
</li>
</ul>
</section>
<section>
<section data-link-for="WebAppManifest">
<h2>
Extension to the <code>WebAppManifest</code> dictionary
Extension to the Web App Manifest
</h2>
<p>
The following IDL extends the <dfn data-cite=
Expand All @@ -181,7 +181,27 @@ <h2>
ShareTarget share_target;
};
</pre>
<section data-dfn-for="WebAppManifest" data-link-for="WebAppManifest">
<p>
The following steps are added to the <a data-cite=
"!appmanifest#dfn-extension-point">extension point</a> in the steps for
<a data-cite="!appmanifest#dfn-processing-a-manifest">processing a
manifest</a>:
</p>
<ol>
<li>Set <var>manifest</var>["<a>share_target</a>"] to the result of
running <a>post-processing the <code>share_target</code> member</a>
given <var>manifest</var>["<a>share_target</a>"],
<var>manifest</var>["<a data-cite=
"!appmanifest#dom-webappmanifest-scope"><code>scope</code></a>"], and
<var>manifest URL</var>.
</li>
</ol>
<div class="issue">
The extension point actually needs to come after the other fields are
post-processed. Otherwise, we will be using a potentially invalid or
relative scope URL.
</div>
<section data-dfn-for="WebAppManifest">
<h3>
<code>share_target</code> member
</h3>
Expand All @@ -199,6 +219,67 @@ <h3>
"!WebShare#dfn-share-target">share target</a>.
</p>
<div class="issue" data-number="27"></div>
<p>
The steps for <dfn>post-processing the <code>share_target</code>
member</dfn> is given by the following algorithm. The algorithm takes
a <a>ShareTarget</a> <var>share target</var>, a <a data-cite=
"!URL#concept-url">URL</a> <var>scope URL</var>, and a <a data-cite=
"!URL#concept-url">URL</a> <var>manifest URL</var>. This algorithm
returns a <a>ShareTarget</a> or <code>undefined</code>.
</p>
<ol>
<li>If <var>share target</var> is <code>undefined</code>, then return
<code>undefined</code>.
</li>
<li>Let <var>URL template</var> be <var>share
target["<a data-link-for="ShareTarget">url_template</a>"]</var>.
</li>
<li>If <var>URL template</var> is <code>undefined</code>, then return
<code>undefined</code>.
</li>
<li>Let <var>test relative URL</var> be the result of running the <a>
replace placeholders</a> algorithm on <var>URL template</var> with
<code>{}</code> (the empty <a data-cite=
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@mgiuca mgiuca Nov 27, 2017 •
edited
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It isn't quite correct to substitute the empty dictionary to find out whether a URL template will expand to within scope.

Consider a manifest:

{
    "scope": "/foo",
    "share_target": {
        "url_template": "/fo{text}o"
    }
}

The manifest will parse correctly, because expanding url_template with text = "" is "/foo". But if given any non-empty text, it will expand to be out of scope.

There are a few solutions to this:

  1. Fix the scope checking algorithm (this) to somehow make sure it fails if any substitution would move it outside the scope.
  2. Prevent template parameters from appearing in the path part (i.e., before the query) entirely.

"!WebShare#dom-sharedata"><code>ShareData</code></a>). If the
result is failure, <a data-cite=
"!appmanifest#dfn-issue-a-developer-warning">issue a developer
warning</a> that the URL template is invalid, and return
<code>undefined</code>.
</li>
<li>Let <var>test absolute URL</var> be the result of running the
<a data-cite="!URL#concept-url-parser">URL parser</a> on <var>test
relative URL</var>, with <var>manifest URL</var> as the
<var>base</var>, and no <var>encoding override</var>. If <var>test
absolute URL</var> is failure, <a data-cite=
"!appmanifest#dfn-issue-a-developer-warning">issue a developer
warning</a> that the URL template is invalid, and return
<code>undefined</code>.
</li>
<li>If <var>test absolute URL</var> is not <a data-cite=
"!appmanifest#dfn-within-scope">within scope</a> of <var>scope
URL</var>, <a data-cite="!appmanifest#dfn-issue-a-developer-warning">
issue a developer warning</a> that the URL template is outside of
the manifest scope, and return <code>undefined</code>.
</li>
<li>Return <var>share target</var>.
</li>
</ol>
<div class="note">
<p>
Unlike the other post-processing steps for URL members of the
manifest, this algorithm does not update the manifest object with
the absolute URL for <a data-link-for=
"ShareTarget">url_template</a>. This is because the <a data-cite=
"!URL#concept-url-parser">URL parser</a> won't work on the URL
template; it can only be run after the placeholders are replaced at
launch time.
</p>
<p>
Therefore, the above steps just validate the URL template, and if
it is invalid, ignore the share target. The launch algorithm below
repeats these same steps using the actual share data.
</p>
</div>
</section>
<section data-dfn-for="ShareTarget" data-link-for="ShareTarget">
<h3>
Expand Down Expand Up @@ -377,6 +458,12 @@ <h3>
empty <var>features</var>.
</li>
</ol>
<p class="note">
This algorithm never aborts if <var>manifest</var> has had the
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This isn't strictly true, due to the above problem.

<a>post-processing the <code>share_target</code> member</a> algorithm
run on it. That algorithm deletes any <a>share_target</a> member that
would fail these checks.
</p>
<p>
The <dfn>replace placeholders</dfn> algorithm takes a <a data-cite=
"!WEBIDL#idl-USVString">USVString</a> <var>template</var> and
Expand Down Expand Up @@ -444,7 +531,6 @@ <h3>
into the URL template.
</p>
</div>
<div class="issue" data-number="25"></div>
</section>
</section>
<section class="informative">
Expand Down