Firmware and Hacking
In late 2015, I decided to start researching IP Cameras. I decided to try out the cheapest models available on Amazon.com, both because I thought those models would be more “fruitful” and because I was trying to do this research on a budget. It turns out that the security on these lower model IP Cameras is really bad.
I looked at five different IP Cameras and was able to gain root access on four of them within a few hours of starting to poke at them. All of the cameras I looked at cost between $30-$70, and can be purchased directly from Amazon.com.
My goals in completing this research were two-fold:
On all four of the cameras I rooted, I was able to exfiltrate image data off of the device.
Today we’re going to look at one of the models I was able to gain root access on. I chose this model because a subsequent patch fixed the vulnerability that allowed me to gain root access.
I started by running nmap to check the available ports. Nothing too interesting there.
Nmap scan report for 192.168.1.13 Host is up (0.0026s latency). Not shown: 65532 closed ports PORT STATE SERVICE 80/tcp open http 443/tcp open https 8750/tcp open unknown
This camera has pretty extensive web administration capabilities, including the ability to upload vendor supplied patches to update the device. However, the version we will be looking at today is the version that comes installed on the device when you open the box: version 2.01. The default credentials, which come printed in the documentation with the device, are
admin:admin. The vulnerability I exploit below is patched in version 2.12 and above, which is available from the DLink website.
My first try involved checking the various HTML inputs. This turned up a couple of not very interesting cross site scripting vulnerabilities that would be hard to exploit in the wild.
My second try began with running wfuzz with the
directory-list-2.3-medium.txt word list that comes with every default Kali Linux installation. For those of you not familiar with wfuzz, it is a tool like dirbuster that facilitates directory enumeration on web servers that do not allow directory indexing. Running wfuzz turned up a lot of html documents that I was already aware of, plus a few more that seemed useless - and then one that turned out to be the beginning of the jackpot: html.htm.
Load html.htm in a browser and the HTML document will contain a list of all the webpages available in the web root. It is more or less a directory index listing. I navigated through each one of the pages until I found the next stage of the jackpot: docmd.htm!
Docmd.htm contains a text box and a submit button. This form allows direct command execution on the device. So what’s the next logical step?
A curl command capable of accomplishing this would look like:
curl 'http://$CAMERA_IP/setSystemCommand' -H 'Authorization: Basic $BASICAUTH_CREDS' -H 'Content-Type: application/x-www-form-urlencoded' --data 'ReplySuccessPage=docmd.htm&ReplyErrorPage=docmd.htm&SystemCommand=telnetd&ConfigSystemCommand=Save'
Fire up telnet or netcat and connect to port 23 of the camera. Root shell accomplished!
While the root shell was not too difficult to load up, it took significantly longer to figure out how to capture image data. I started by documenting all the binaries available in the PATH and elsewhere on the filesystem, and then working my way through each to see what they did:
# ls /bin chmod htmlunpack sounddb imagetp ated umount ps swing busybox nvram_daemon mknod mail kill uvc_stream rm alphapd nvram_set ash openssl ping ralink_init msmtp i2c gpio ls pcmcmd echo notifystream switch mDNSResponder lanconfig touch sed pppoecd reg audiopush cp mkdir upgradefw mount login lld2d iperf mydlinkevent ipush ntpclient iwpriv sleep pwd sh nvram_get cat grep inadyn date schedule mii_mgr mtd_write ov7740 # ls /sbin automount_boot.sh config-udhcpd.sh udhcpc reboot udev config-igmpproxy.sh snort.sh zcip cpubusy.sh ucp wlan.sh pppoe.sh ddns.sh udhcpc.sh acodec route poweroff internet.sh ntp.sh vpn-passthru.sh web.sh snmp.sh video.sh config-dns.sh config-pppoe.sh arp dhcp.sh config-iTunes.sh chpasswd.sh halt ifconfig automount.sh zcip.sh init lan.sh mdev cameraname.sh # ls /usr/bin killall free expr test ftpd arping printf [ [[ uptime ftpputimage top tr # ls /usr/sbin chpasswd inetd brctl telnetd
I eventually came across the
/tmp/mail.txt. Inside that file is the base64 encoded image data from the moment the “mail” command was run. Copy that data into a tmux buffer, write it to your local filesystem and base64 decode that raw data for an image file!
I also created a Metasploit module for this vulnerability: https://www.rapid7.com/db/modules/exploit/linux/http/dlink_dcs_930l_authenticated_remote_command_execution