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Implementing CSRF Protection in modifications
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24 Apr 2008
Rating:
 (2 votes
- 4.50 average) With the new version released today for vBulletin 3.6.10 and 3.7.0 RC4, a new protection against Cross Site Request Forgery (CSRF) has been introduced. This new protection might influence the coding in modifications. Scott MacVicar took the time to compile a short explanation on this new protection for the coders on vBulletin.org: Changes for CSRF protection with third party modifications Cross Site Request Forgery (CSRF) involves taking advantage of the stateless nature of HTTP, there are no ways to ensure the exact origin of a request, its also not possible to detect what was actually initiated by a user and what was forced by a third party script. A token was added to the latest version of each of the vBulletin products, with the release of 3.6.10 and 3.7.0 RC4 it is no longer possible to submit a POST request directly without passing in the known token. The addition of a security token for each POST request removes the ability for a remote page to force a user to submit an action. At the moment this protection will only apply to vBulletin files and third party files will need to opt into this protection and add the appropriate hidden field. This was done to preserve backwards compatibility. Adding Protection to your own files To opt your entire file into CSRF protection the following should be added to the top of the file under the define for THIS_SCRIPT. PHP Code:
define('CSRF_PROTECTION', true);
If this value is set to false then all CSRF protection is removed for the file, this is appropriate for something that intentionally accepts remote POST requests. You should always add this to your file, even if you don't think the script is ever going to receive POST requests. An absence of this defined constant within your files will result in the old style referrer checking being performed. Template Changes The following should be added to all of the forms which POST back to vBulletin or a vBulletin script. This will automatically be filled out with a 40 character hash that is unique to the user. Code:
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" /> Exempting Certain Actions It may be appropriate to exempt a particular action from the CSRF protection, in this case you can add the following to the file. PHP Code:
define('CSRF_SKIP_LIST', 'action_one,action_two');
If the skip list needs to be changed at runtime is it available within the registry object, using the init_startup hook the following code would be used to exempt 'example.php?do=action_three'. PHP Code:
if (THIS_SCRIPT == 'example')
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