1.5.26 m.trust

优质

小牛编辑

132浏览

2023-12-01

If you're writing a template for a view, use m() instead.

This method flags a string as trusted HTML.

Trusted HTML is allowed to render arbitrary, potentially invalid markup, as well as run arbitrary Javascript, and therefore the developer is responsible for either:

sanitizing the markup contained in the string, or
acknowledging that the string is authorized to run any code that may be contained within it.

Note that browsers ignore <script> tags that have been inserted into the DOM via innerHTML. They do this because once the element is ready (and thus, has an accessible innerHTML property), their rendering engines cannot backtrack to the parsing-stage if the script calls something like document.write("</body>").

For this reason, m.trust will not auto-run <script> tags from trusted strings.

Browsers do, however, allow scripts to be run asynchronously via a number of execution points, such as the onload or onerror attributes in <img> and <iframe>.

IE also allows running of Javascript via CSS behaviors in <link>/<style> tags and style attributes.

It's worth noting that the execution points listed above are commonly used for security attacks in combination with malformed markup, e.g. strings with mismatched attribute quotes like " onload="alert(1).

Mithril templates are defended against these attacks by default, except when markup is injected via m.trust.

It is the developer's responsibility to ensure the input to m.trust cannot be maliciously modified by user-entered data.

Usage

//assume this content comes from the server
var content = "<h1>Error: invalid user</h1>";

m.render("body", [
    m("div", m.trust(content))
]);

yields:

<body>
    <div>
        <h1>Error: invalid user</h1>
    </div>
</body>

Signature

How to read signatures

String trust(String html)

String html
A string containing HTML markup
returns String trustedHtml
The returned string is a String object instance (as opposed to a string primitive) containing the same HTML content, and exposing a flag property for internal use within Mithril. Do not create or manipulate trust flags manually.
Also note that concatenating or splitting a trusted string removes the trust flag. If doing such operations, the final string needs to be flagged as trusted.