Race Condition Enabling Link Following
The product checks the status of a file or directory before accessing it, which produces a race condition in which the file can be replaced with a link before the access is performed, causing the product to access the wrong file.
While developers might expect that there is a very narrow time window between the time of check and time of use, there is still a race condition. An attacker could cause the product to slow down (e.g. with memory consumption), causing the time window to become larger. Alternately, in some situations, the attacker could win the race by performing a large number of attacks.
Impact: Read Files or DirectoriesModify Files or Directories
ID : DX-49
This code prints the contents of a file if a user has permission.Code Example:
php//resolve file if its a symbolic link* if(is_link($filename)){ ``` $filename = readlink($filename); } if(fileowner($filename) == $user){ echo file_get_contents($realFile); return; } else{ echo 'Access denied'; return false; } }
- PLOVER
- CERT C Secure Coding
- Software Fault Patterns