Trusted types attributes #1268

lukewarlow · 2024-03-27T19:22:16Z

This calls the get Trusted Types-compliant attribute value algorithm from Trusted Types (w3c/trusted-types#418) from attribute's change, append, and replace.

Changed the signature of setAttribute and setAttributeNS to accept Trusted Types as values. The underlying Attr node's values continue to be DOMString, so moving nodes across elements or adding standalone attributes to elements can cause TT violations. This matches WPT tests and the Chromium's implementation.

See and #789. Supercedes #809 and #1247

At least two implementers are interested (and none opposed):
- Chromium
- Gecko
Tests are written and can be reviewed and commented upon at:
- https://github.com/web-platform-tests/wpt/tree/master/trusted-types
Implementation bugs are filed:
- Chromium:https://bugs.chromium.org/p/chromium/issues/detail?id=739170
- Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1508286
- WebKit: https://bugs.webkit.org/show_bug.cgi?id=266630
MDN issue is filed: …
The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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lukewarlow · 2024-03-27T19:22:41Z

This is a clone of #1247 where I will finish any outstanding work to get this across the line

lukewarlow · 2024-04-11T12:21:53Z

See also #1258 which is another integration point with the DOM spec that we need for TT.

dom.bs

otherdaniel · 2024-04-15T17:13:57Z

dom.bs

+   <li><p><a>Validate and set attribute value</a> <var>attr</var>'s <a for="Attr">value</a> for
+   <var>attr</var> with <var>element</var>.
+
+   <li><p>If <var>element</var> <a lt="has an attribute">has</a> an <a>attribute</a>


I still find it difficult to wrap my head around this logic. I think conceptually, we want to have the old value -- from before the call, and thus before a default policy might have mucked with it. That's what should go into the change attribute logic. But once we have that, I'm not sure why we'd need to throw an exception here. I'm not sure why we'd have to care whether the default policy does anything funny with the attribute in the mean time.

I've read through this spec path and I believe that, if the default policy removes the existing attribute node, then this will call replace an attribute, which in turn calls replace a list item, which results in a no-op because the old value no longer exists to be replaced.

So I think in this situation you're probably right the spec doesn't need to do anything, will make that change.

Having said that I'm slightly uneasy about stuff like attribute change steps still firing and how that all works spec wise.

Both Chromium and WebKit don't actually follow the spec 100% here and so I think would actually result in a different behaviour to this spec (the index lookup happens after the TT call) so that's also not ideal.

lukewarlow · 2024-04-22T13:18:23Z

I think I've addressed all the comments from #1247.

I do want to point out Chrome and WebKit don't (or at least not in a way obvious to me) 100% follow the flow of the spec and as a result this may result in differences specifically in weird cases with attribute mutation.

So that bit especially it would be good to get feedback on.

It's also worth being aware that like Chromium's implementation this spec means that certain ways to update a nodes value don't work with a trusted type object as a user might expect. (e.g. iframe.getAttributeNode('srcdoc').value = trustedHTMLObj; will throw unless allowed by a default policy). I think in pratice this will be fine, and in some cases is the only real option we have without nodes keeping track of whether they're trusted or not (which would add lots of complexity)

annevk

This change is either incomplete or makes many cosmetic changes that would be best proposed separately as they confuse me quite a bit.

dom.bs

lukewarlow · 2024-04-22T15:47:56Z

This change is either incomplete or makes many cosmetic changes that would be best proposed separately as they confuse me quite a bit.

Apologies I thought I'd reverted all of these changes but I missed a few, it's because I changed stuff and then changed it back and this led to some wonky diffs. Have hopefully reverted all of these unnecessary changes

annevk · 2024-04-22T16:07:37Z

dom.bs

+ <li><p>If <var>attribute</var>'s <a for=Attr>element</a> <a lt="has an attribute">has</a>
+ an <a>attribute</a> <var>attribute</var>, then <a>handle attribute changes</a> for
+ <var>attribute</var> with <var>attribute</var>'s <a for=Attr>element</a>, <var>oldValue</var>, and
+ <var>value</var>.


Should this be value or attribute's value? They can be different, right?

dom.bs

lukewarlow · 2024-05-07T15:54:52Z

@otherdaniel, @annevk , and @smaug---- regarding the case where the default policy changes assumptions about the existence of an attribute mid-way through what would you prefer the spec say to do? Currently I've specced to throw, but Chromium currently re-looks up the index (spec doesn't explicitly work on an index basis but Chromium and WebKit do)

annevk · 2024-05-13T14:58:26Z

Attributes are stored in a list and those do have indices per Infra. What am I missing?

lukewarlow · 2024-05-13T15:03:24Z

Sorry I mean algorithmically the spec and implementations don't follow the same flow. So it's trickier to reason between the spec and implementation. This might just be my lack of familiarity with these APIs too.

annevk · 2024-05-13T15:11:38Z

The path of least resistance is prolly matching Chromium. Introducing new paths that throw is always risky. If you are looking for guidance as to how, I'd need quite a bit more context to provide helpful suggestions.

See w3c/trusted-types#418 and whatwg#789. Supercedes PR whatwg#809.

…an attribute

lukewarlow · 2024-05-16T15:44:07Z

The path of least resistance is prolly matching Chromium. Introducing new paths that throw is always risky. If you are looking for guidance as to how, I'd need quite a bit more context to provide helpful suggestions.

I've partially matched Chromium but gone a bit further with the error correction as Chromium still has some bugs wrt mutating attributes within the default policy.

lukewarlow · 2024-05-16T15:44:40Z

@otherdaniel if you've got time could you read through this to ensure it makes sense to you?

lukewarlow · 2024-05-16T15:49:29Z

dom.bs

@@ -6530,23 +6545,39 @@ string <var>namespace</var> (default null):</p>

 <div algorithm>
 <p>To <dfn export id=concept-element-attributes-set-value>set an attribute value</dfn> given an


This algorithm covers setAttributeNS

lukewarlow · 2024-05-16T15:49:54Z

dom.bs

- <a for=Attr>local name</a> is <var>qualifiedName</var>, <a for=Attr>value</a> is
- <var>value</var>, and <a for=Node>node document</a> is <a>this</a>'s <a for=Node>node document</a>,
- then <a lt="append an attribute">append</a> this <a>attribute</a> to <a>this</a>, and then return.
+ <li><p>Let <var>attributeExists</var> be false if <var>attribute</var> is null, and true otherwise.


This algorithm covers setAttribute

lukewarlow · 2024-05-16T15:51:10Z

dom.bs

@@ -7382,7 +7430,13 @@ string <var>value</var>, run these steps:
 <li><p>If <var>attribute</var>'s <a for=Attr>element</a> is null, then set <var>attribute</var>'s
 <a for=Attr>value</a> to <var>value</var>.

- <li><p>Otherwise, <a lt="change an attribute">change</a> <var>attribute</var> to <var>value</var>.
+ <li><p>Otherwise:


This covers attr.nodeValue, attr.value, and attr.textContent.

lukewarlow · 2024-05-16T15:53:00Z

dom.bs

@@ -6519,6 +6529,11 @@ string <var>namespace</var> (default null):</p>

 <li><p>If <var>oldAttr</var> is <var>attr</var>, return <var>attr</var>.

+ <li><p>Let <var>verifiedValue</var> be the result of calling <a>verify attribute value</a>


This covers, setAttributeNode, setAttributeNodeNS, setNamedItem and setNamedItemNS

lukewarlow · 2024-05-16T16:39:59Z

dom.bs

@@ -6870,11 +6918,17 @@ method steps are:
  <p>If <var>attribute</var> is null, then:

  <ol>
-   <li><p>If <var>force</var> is not given or is true, create an <a>attribute</a> whose
+   <li><p>Set <var>attribute</var> to an <a>attribute</a> whose


This covers toggleAttribute. I need to double check this because I think it could still lead to a weird state in it's current form.

Have updated this to work how chrome appears to

The TT-check in Chromium's toggleAttribute was unintentional. It came about as a side effect of how toggleAttribute was implemented on top of other methods. We can't come up with any XSS based on toggleAttribute. It'd probably be best to remove it from the PR, and that we fix our implementation on our end.

… Chrome.

lukewarlow force-pushed the trusted-types-attributes branch 2 times, most recently from 3562fcb to ac5b4aa Compare April 10, 2024 15:52

lukewarlow mentioned this pull request Apr 11, 2024

Draft integration with Trusted Types, take 2. #1247

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otherdaniel reviewed Apr 15, 2024

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lukewarlow marked this pull request as ready for review April 22, 2024 12:53

lukewarlow requested review from annevk and smaug---- April 22, 2024 13:13

lukewarlow force-pushed the trusted-types-attributes branch from ba80870 to 36476b5 Compare April 22, 2024 13:57

lukewarlow mentioned this pull request Apr 22, 2024

[Meta] Upstream changes w3c/trusted-types#476

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lukewarlow force-pushed the trusted-types-attributes branch from 370f5c9 to 4421d50 Compare April 22, 2024 15:46

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koto added 3 commits May 16, 2024 16:39

Draft integration with Trusted Types, take 2.

6d4b27d

See w3c/trusted-types#418 and whatwg#789. Supercedes PR whatwg#809.

Added integration in 'set an attribute value'.

98ba2fe

Removed stringification.

ce190dd

koto and others added 14 commits May 16, 2024 16:39

Fixed formatting.

a751131

Fixed copy-paste error in setAttribute() and indentation.

a4463f2

Fix build

3475f8f

Change code to pass sink values through to TT code.

d446134

Move validate and set attribute into append an attribute

d835bc4

Remove sink values from spec

3fe269c

Revert changes to setAttributeNode and setAttributeNodeNS method steps

6958b06

Remove throw from set an attribute and move TT check down to replace …

90b3abb

…an attribute

Revert unneeded changes

3efbaa8

Address comment

20564e4

Add missing and

e3803db

Address some comments

0e0516f

Re-add early return

1c71c66

Change dfn to use given rather than with

0f0ed54

lukewarlow force-pushed the trusted-types-attributes branch 2 times, most recently from 4089eaf to 02db8c7 Compare May 16, 2024 15:41

lukewarlow requested a review from otherdaniel May 16, 2024 15:43

lukewarlow requested a review from annevk May 16, 2024 15:44

Update how the enforcement is done

55af76e

lukewarlow force-pushed the trusted-types-attributes branch from 02db8c7 to 55af76e Compare May 16, 2024 15:47

lukewarlow commented May 16, 2024

View reviewed changes

Add tentative enforcement for toggleAttribute

6e40964

lukewarlow commented May 16, 2024

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Update enforcement for toggleAttribute to match behaviour observed in…

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… Chrome.

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Trusted types attributes #1268

Trusted types attributes #1268

lukewarlow commented Mar 27, 2024 •

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otherdaniel May 22, 2024

		@@ -6530,23 +6545,39 @@ string <var>namespace</var> (default null):</p>

		<div algorithm>
		<p>To <dfn export id=concept-element-attributes-set-value>set an attribute value</dfn> given an

		@@ -6519,6 +6529,11 @@ string <var>namespace</var> (default null):</p>

		<li><p>If <var>oldAttr</var> is <var>attr</var>, return <var>attr</var>.

		<li><p>Let <var>verifiedValue</var> be the result of calling <a>verify attribute value</a>

Trusted types attributes #1268

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lukewarlow commented Mar 27, 2024 •

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