Extracting data from Apple Safari's cache

Five minutes ago, I overwritten the super-shining-new CSS stylesheet that implements the current color scheme, because i wanted to restore the original one and put it in a new theme for this site, so that people who enjoyed the old theme could continue to use it. But, as the most kiddiest system administrator, i uncompressed the original files from the backup archive OVER the current ones..

Safari to the rescue! Every cached item by safari is stored into a SQlite3 database located in ~/Library/Caches/com.apple.Safari, let’s inspect how it is structured:

 13:54:42 vjt@voyager:~/Library/Caches/com.apple.Safari$ sqlite3 Cache.db 
SQLite version 3.5.1
Enter ".help" for instructions

sqlite> .tables
cfurl_cache_blob_data       cfurl_cache_schema_version

sqlite> .schema cfurl_cache_response 
CREATE TABLE cfurl_cache_response(
  version INTEGER,
  hash_value INTEGER,
  storage_policy INTEGER,
  request_key TEXT UNIQUE,

sqlite> .schema cfurl_cache_blob_data
CREATE TABLE cfurl_cache_blob_data(
  response_object BLOB,
  request_object BLOB,
  receiver_data BLOB,
  proto_props BLOB,
  user_info BLOB);

sqlite> select * from cfurl_cache_response limit 3;
1|0|1897220634|0|http://..../|2008-01-19 11:10:33
2|0|-662909776|0|http://..../|2008-01-19 11:10:33

Wow. Impressive. That’s why i love Apple products, because they are so well structured that you can freely inspect them and use them and their resources for every unplanned task you could have to complete.. even to fix your own mistakes ;). And it’s also intriguing, because you have to scratch your own itch and find the solution while exploring a beautifully constructed software product.

To make a long story short, every cached URL is stored into the request_key field of the cfurl_cache_response table, while in the receiver_data field of the cfurl_cache_blob_data there is the actual cached data. Now we can look for the overwritten bbs theme CSS stylesheet:

sqlite> select entry_ID, request_key from cfurl_cache_response
   ...> where request_key like '%bbs/style.css';

Now, let’s search in the blob_data table the entry with ID 1950:

sqlite> select receiver_data from cfurl_cache_blob_data
   ...> where entry_ID = 1950;
 * Themetastic, for Drupal 5.0
 * Stefan Nagtegaal, iStyledThis [dot] nl
 * Steven Wittens, acko [dot] net`
 * If you use a customized color scheme, you must regenerate it after
 * modifying this file.
[......rest of the stylesheet removed.....]

YAY! Found it! A quick cut&paste.. and the lost theme is back! :D

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