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lukewarlow merged 4 commits into from
Sep 9, 2024
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Upstream Trusted Types enforcement in EnsureCSPDoesNotBlockStringCompilation #659

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53 changes: 46 additions & 7 deletions index.bs
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Expand Up @@ -751,8 +751,8 @@ spec: WebRTC; urlPrefix: https://www.w3.org/TR/webrtc/

Each <a>violation</a> has a
<dfn for="violation" id="violation-resource" export>resource</dfn>, which is
either null, "`inline`", "`eval`", "`wasm-eval`", or a {{URL}}. It represents the resource
which violated the policy.
either null, "`inline`", "`eval`", "`wasm-eval`", "`trusted-types-policy`", "`trusted-types-sink`" or a {{URL}}.
It represents the resource which violated the policy.

Note: The value null for a <a>violation</a>'s <a
for="violation">resource</a> is only allowed while the <a>violation</a> is
Expand Down Expand Up @@ -1452,6 +1452,47 @@ spec: WebRTC; urlPrefix: https://www.w3.org/TR/webrtc/
returns normally if string compilation is allowed, and throws an "`EvalError`"
if not:

1. If |compilationType| is timer, then:
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<!-- timer is an enum value. -->

1. Let |sourceString| be |codeString|.

1. Else:

1. Let |compilationSink| be `"Function"` if |compilationType| is function, otherwise `"Eval"`.
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<!-- function is an enum value. -->

1. Let |isTrusted| be `true`.

1. If |bodyArg| is not a {{TrustedScript}} object, set |isTrusted| to `false`.
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1. If |isTrusted| is `true` then:

1. If |bodyString| is not equal to |bodyArg|'s [=TrustedScript/data=], set |isTrusted| to `false`.

1. If |isTrusted| is `true`, then:

1. For each |arg| in |parameterArgs|:

1. Let |index| be the index of |arg| in |parameterArgs|.
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@mikewest mikewest Sep 5, 2024

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I'd suggest writing this loop differently, as I don't think Infra provides a way to get the index of a given element in a list. Something like the following:

1.  Assert: |parameterArgs|' [list/length=] is equal to [parameterStrings]' [=list/length=].
1.  [=list/iterate|For each=] |index| of [=the range=] 0 to |parameterArgs|' [=list/length=]:
    1.  Let |arg| be |parameterArgs|[|index|].

Alternatively, we could add something to Infra to either create a For each variant that provides both an item and its index, or some mechanism to get the index of a given item? @annevk might have thoughts about which path might be preferable.

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@lukewarlow lukewarlow Sep 9, 2024

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I've gone with what you suggested for now.


1. If |arg| is not a {{TrustedScript}} object, set |isTrusted| to `false`.

1. If |isTrusted| is `true`, then:

1. if |parameterStrings|[|index|] is not equal to |arg|'s [=TrustedScript/data=], set |isTrusted| to `false`.

1. If |isTrusted| is `true`, let |sourceToValidate| be a new instance of
the {{TrustedScript}} interface, with its [=TrustedScript/data=]
set to |codeString|. Otherwise, let |sourceToValidate| be |codeString|.
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1. Let |sourceString| be the result of executing the [$Get Trusted Type compliant string$] algorithm, with
{{TrustedScript}}, |realm|, |sourceToValidate|, |compilationSink|, and `'script'`.

1. If the algorithm throws an error, throw an {{EvalError}}.

1. If |sourceString| is not equal to |codeString|, throw an {{EvalError}}.

1. Let |result| be "`Allowed`".

2. Let |global| be |realm|'s [=realm/global object=].
Expand All @@ -1477,7 +1518,7 @@ spec: WebRTC; urlPrefix: https://www.w3.org/TR/webrtc/

3. If |source-list| [=list/contains=] the expression
"<a grammar>`'report-sample'`</a>", then set |violation|'s [=violation/sample=] to
the substring of |codeString| containing its first 40 characters.
the substring of |sourceString| containing its first 40 characters.

4. Execute [[#report-violation]] on |violation|.

Expand All @@ -1486,8 +1527,6 @@ spec: WebRTC; urlPrefix: https://www.w3.org/TR/webrtc/

4. If |result| is "`Blocked`", throw an `EvalError` exception.

Note: |parameterStrings|, |bodyString|, |compilationType|, |parameterArgs|, and |bodyArg| are currently unused. They are included for future use.

<h3 id="wasm-integration">Integration with WebAssembly</h3>

WebAssembly defines the {{HostEnsureCanCompileWasmBytes()}} abstract operation
Expand Down Expand Up @@ -3693,10 +3732,10 @@ this algorithm returns normally if compilation is allowed, and throws a

3. If |directive|'s <a for="directive">value</a> contains
"<a grammar>`'strict-dynamic'`</a>":

1. If |request|'s <a for="request">parser metadata</a> is not
<a>"parser-inserted"</a>, return "`Allowed`".

Otherwise, return "`Blocked`".

4. If the result of executing [[#match-response-to-source-list]] on
Expand Down