Firefox3/BorderImage Security Review

Overview

Background links

• https://bugzilla.mozilla.org/show_bug.cgi?id=378217
• http://dev.w3.org/csswg/css3-background/#the-border-image

Security and Privacy

• What security issues do you address in your project?
  • A new CSS property is added. It is parsed using the existing CSS parser APIs
• Is system or subsystem security compromised in any way if your project's configuration files / prefs are corrupt or missing?
  • no
• Include a thorough description of the security assumptions, capabilities and any potential risks (possible attack points) being introduced by your project.
  • Assumes the existing image loading code will detect and gracefully handle malformed images
  • Assumes that floating point division by 0 (or other overflow) won't result in an exception

Exported APIs

• Please provide a table of exported interfaces (APIs, ABIs, protocols, UI, etc.)
  • Just a new CSS property
• Does it interoperate with a web service? How will it do so?
  • nope
• Explain the significant file formats, names, syntax, and semantics.
• Are the externally visible interfaces documented clearly enough for a non-Mozilla developer to use them successfully?
  • yes, though the CSS spec
• Does it change any existing interfaces?
  • no

Module interactions

• What other modules are used (REQUIRES in the makefile, interfaces)
  • nothing new

Data

• What data is read or parsed by this feature
  • the -moz-border-image css property
• What is the output of this feature
  • An array of parsed nsCSSValues
• What storage formats are used
  • nsCSSValue, nsMargin, an enum for the border-image types, and imgIRequest for the image

Reliability

• What failure modes or decision points are presented to the user?
  • If the image cannot be loaded, the border-image is effectively removed (per spec)
  • If the property doesn't parse properly, then the user will see an error in the Error Console as with all malformed CSS properties
• Can its files be corrupted by failures? Does it clean up any locks/files after crashes?
  • n/a

configuration

• Can the end user configure settings, via a UI or about:config? Hidden prefs? Environment variables?
  • none
• Are there build options for developers? [#ifdefs, ac_add_options, etc.]
  • none
• What ranges for the tunable are appropriate? How are they determined?
  • n/a
• What are its on-going maintenance requirements (e.g. Web links, perishable data files)?
  • needs to be kept up to date with the proposed spec and finalized as border-image when the spec is finalized

Relationships to other projects - are there related projects in the community?

• Safari has their own version implemented; there is a proposed w3c spec