fix(modal): Fix use of inline styles for Content Security Policy

[farrago]

Summary

Inline styles are not allowed under CSP, so this replaces the inline styles used by $modalStack with calls to angular.element.css()

Details

$modalStack.open creates two divs directly with angular.element, and both divs have inline style elements (i.e. '<div style="...">').

If Content Security Policy (CSP) is enabled, these inline styles cannot be applied and cause errors. e.g. in chrome:

[Report Only] Refused to apply inline style because it violates the following Content Security Policy directive: "default-src 'self'". Either the 'unsafe-inline' keyword, a hash ('sha256-xHgdoELGuMXNdMeJ4PQkbzZpH1rlmZwpY3b56d2ZvpI='), or a nonce ('nonce-...') is required to enable inline execution. Note also that 'style-src' was not explicitly set, so 'default-src' is used as a fallback.

This is fixed by replacing the inline styles with calls to angular.element.css() (which boils down to HTMLElement.style.foo = bar;) as this does not trigger the inline styles violation.

• For the 'faux' modal div, this is simply done immediately.
• For the temporary div that is replaced by the modal-window, it is a bit more complex:
  • If you just apply to this temp div using .css() it still fails when the modal-window directive replaces it because Angular merges the attributes of the temp div and the new one. The temp div has an inline style (set by .css()), and trying to apply this style='...' as an attribute to the new div causes the same inline execution error.
  • Instead we pass the top position through a custom attribute (mm-top), then the modal-window applies the value to itself using element.css().

Setup

Browser: Chrome 52.0.2743.116 m (up to date), plus same result in Firefox, Edge, etc.
OS: Windows 10
Server: NodeJS 4.4.3
CSP Headers: content-security-policy-report-only: default-src 'self'; report-uri /api/v0/csp-report (This reports but doesn't prevent violations of the policy while debugging rules).

Notes

As per the error reported by Chrome, this could theoretically be worked around by using 'unsafe-inline' but this is, as named, unsafe. It could also be worked around with a hash for each case but that isn't well supported by browsers yet, and there are a lot of different cases that would need a hash for each one. Nonces are even harder to use with library code.

Test Plan:

• Run all the unit tests and check they all pass
• Test the library in my own project and check no CSP warnings are given
• Open and close some modals at various window scroll positions and check they still position correctly

[farrago]

I should mention that the default templates also use inline styles which will cause CSP violations.

For a fully CSP-compliant result you will also have to use your own replacement templates that don't use inline styles and instead set the styling through your application's own CSS.