NPAPI:ClearSiteData

Status

Under consideration.

Contributors

• Last modified: December 23, 2010
• Authors: Julian Reschke (greenbytes), Dan Witte (Mozilla), Bernhard Bauer (Chromium), Rajesh Gwalani (Adobe), Josh Aas (Mozilla)

Overview

Allows browsers to request that plugins clear locally stored private data.

Specification

The following method will allow browsers to request that plugins clear data. Note that plugins (but no instances) must be initialized and function tables retrieved in order to call this method.

NPError NPP_ClearSiteData(
   const char* site,       // site for which to clear data
   PRUint64 flags,         // what type of data to clear
   PRUInt64 maxAge         // max. age of information in seconds
);

• The flags argument is a bit mask representing the type(s) of data to clear.

/* NP_CLEAR_ALL: Clear all private data */
#define NP_CLEAR_ALL        0

/* NP_CLEAR_CACHE: Clear cached data which can simply be retrieved again as requested.
   To be used out of concern for space and not necessarily privacy. */
#define NP_CLEAR_CACHE      1 << 0

/* More flags may be defined later, this spec will be updated. */

• The site argument is interpreted as follows:
  • If NULL, all site-specific data and more generic data on browsing history (for instance, number of sites visited) should be cleared.
  • If !NULL, argument is a domain per the domain portion of the URI specification but with a requirement for NFKC-normalized UTF-8 encoding. No other encoding is allowed. All sub-domains of the specified domain are to be cleared as well. If a sub-domain is specified only it and its sub-domains are to be cleared. For example, if a browser specifies "b.a.com" then data for "b.a.com" and "c.b.a.com" is to be cleared but data for "a.com" is not to be cleared.
• The maxAge argument is the maximum age in seconds of data to clear, inclusive. If maxAge is 0, no data is cleared. If maxAge is the maximum unsigned 64-bit integer, all data is cleared.

The following new NPError values will be available for return from NPP_ClearSiteData.

// can't clear by time range
#define NPERR_TIMERANGE_NOT_SUPPORTED (NPERR_BASE + 14)
// can't clear by origin
#define NPERR_LIMITBYORIGIN_NOT_SUPPORTED (NPERR_BASE + 15)
// malformed 'origin' string
#define NPERR_MALFORMED_ORIGIN (NPERR_BASE + 16)

For any other type of error the plugin must return NPERR_GENERIC_ERROR.

If site data is in use by an instance of the plugin when NPP_ClearSiteData is called then it is up to the plugin to do the right thing.

Open Issues

• Do we need a method for discovering what site data the plugin has? Mozilla and Apple have expressed a strong desire for this.

Notes

Overview of current UIs

Type	Firefox	IE	Opera	Safari	Chrome
Browsing History	yes	yes	yes	yes	yes
Download History	yes	yes	yes	yes	yes
Form History	yes	yes	?	yes	yes
Search History	yes	?	?	?	?
Cookies	yes	yes	temporary/all	yes	yes
Cache	yes	yes	yes	yes	yes
Active Logins	yes	yes	"password manager"	yes	yes
Site Preferences	yes	?	?	?	?

In addition, IE has "InPrivate Filtering Data" (what is this?)

In addition, Opera has "delete password protected pages and data" and "bookmark visited times".

In addition, Safari has "webpage preview images", "website icons" and "top sites"

Parameters	Firefox	IE	Opera	Safari	Chrome
Time Range	yes	no	no	no	yes
By Site	yes (context menu in history)	??	??	??	??

Type of Data

• things the user enters, except for credentials (form data)
• credentials
• things cached by the UA (pages, preview images, icons)
• local data stored by the server / web application (cookies, HTML5 local storage, Flash/Silverlight local storage)
• history information (bookmarks, visited URIs)
• settings specific to a site (for instance, preferences with respect to privacy, script disabling...)

Time range

Several UAs offer to restrict the clear operation to a time range such as "today" or "last week".

Site/URI

Firefox supports "forget about this site". Other UAs do not appear to support this.

Existing Discussion and Documentation

Mail thread on plugin-futures: https://mail.mozilla.org/private/plugin-futures/2010-January/001150.html

In particular, Lloyd Hilaiel proposed an alternate approach where plugins would store everything in a standard filesystem based layout, so the UA itself can do the clearing. See https://mail.mozilla.org/private/plugin-futures/2010-January/001156.html

Flash Local Storage: http://www.macromedia.com/support/documentation/en/flashplayer/help/help02.html

Firefox issue - clearing local storage with time range: https://bugzilla.mozilla.org/show_bug.cgi?id=527667