css sanitization in style attributes

[microcosm-cc]

css sanitization in style attributes

[buro9]

Merged, thanks for the great addition.

[gerad]

Nothing is ever as easy as it seems. There's no package manager in the project, I'll have to bring one in. Hopefully there are no objections to https://github.com/golang/dep

[buro9]

I'm going to put some thought into what the interface for a fully integrated CSS sanitizer might be.

This may take me a while as I'm flying around a bit right now, but should have a proposal within a couple of weeks.

It will likely follow the implementation style of the proposal PR you had, but allow for full configurability of a policy for CSS on a per entity/tag basis.

[pauln]

Have you made any progress on your proposal for CSS sanitising, @buro9? Even a basic level of CSS support (for style attributes, as per @gerad's proposal) would help tremendously.

[StevenGutzwiller]

@buro9 My team currently uses bluemonday for sanitizing inserted html styled with css, and we would like to make changes to fix this issue.

Currently I think it makes sense for the API to add something along the lines of the following:

AllowStyles(string[])-allows all listed style properties

Matching(regex) adds handler to style that checks if it matches regex

MatchingEnum(...string) adds handler to style that checks if it matches list of enums

MatchingHandler(function(string)bool) adds handler to style that takes in string representing the
property value and returns if it is valid

Globally() adds style policy to all elements

OnElements(...string) add style to specified elements

I was thinking each CSS3 property could have a default handler that prevents all/most values that can be overwritten with MatchingHandler().

This doesn't prevent security issues, but the user would have to specifically whitelist styles and override the default handler in order to cause issues.

How does this sound to you?

[buro9]

That sounds like a really good API for this. I'd approve and merge PRs that followed that API.