Can't find new extensions unless have write perms on extensions directory

1. 1. Problem:

If CiviCRM does not have write permissions for the CiviCRM extensions directory, then it silently fails to search for extensions in that directory.

I found the problem by combing through strace output, and found this:

0.000421 access("sites/all/civicrm/extensions", W_OK) = -1 EACCES (Permission denied)

1. 1. Solution:

When I enabled write access for that directory, things worked correctly.

• For the purposes of adding a manually installed module, CiviCRM should not need, nor assume that it has, write access to this directory. The extensions directory should be opened in a read only mode.

• If there's an error, it should be reported. The web page should indicate that there was an error, and detail like file paths should go into the logs.

• In order that security can be locked down, it should not be necessary for civicrm to have write access to sub-directories of the extensions directory. The cache and tmp directories would be better located in a location outside the web root, like /tmp perhaps. Probably the location needs to be configurable.

• It would be nice to be able to add permissions using drush, and therefore as a user who has write access where the web user does not.

1. 1. Related?

http://issues.civicrm.org/jira/browse/CRM-7705