Sudo 1.8.14 - Unauthorized Privilege

# Exploit Title: sudo -e - a.k.a. sudoedit -  unauthorized privilege escalation

# Date: 07-23-2015

# Exploit Author: Daniel Svartman

# Version: Sudo <=1.8.14

# Tested on: RHEL 5/6/7 and Ubuntu (all versions)

# CVE: CVE-2015-5602.



Hello,



I found a security bug in sudo (checked in the latest versions of sudo

running on RHEL and ubuntu) when a user is granted with root access to

modify a particular file that could be located in a subset of directories.



It seems that sudoedit does not check the full path if a wildcard is used

twice (e.g. /home/*/*/file.txt), allowing a malicious user to replace the

file.txt real file with a symbolic link to a different location (e.g.

/etc/shadow).



I was able to perform such redirect and retrieve the data from the

/etc/shadow file.



In order for you to replicate this, you should configure the following line

in your /etc/sudoers file:



<user_to_grant_priv> ALL=(root) NOPASSWD: sudoedit /home/*/*/test.txt



Then, logged as that user, create a subdirectory within its home folder

(e.g. /home/<user_to_grant_priv>/newdir) and later create a symbolic link

inside the new folder named test.txt pointing to /etc/shadow.



When you run sudoedit /home/<user_to_grant_priv>/newdir/test.txt you will

be allowed to access the /etc/shadow even if have not been granted with

such access in the sudoers file.



I checked this against fixed directories and files (not using a wildcard)

and it does work with symbolic links created under the /home folder.