07CKS模拟考试
Question 1 | Contexts
Task weight: 1%
You have access to multiple clusters from your main terminal through kubectl contexts. Write all context names into /opt/course/1/contexts, one per line.
From the kubeconfig extract the certificate of user restricted@infra-prod and write it decoded to /opt/course/1/cert.
Answer:
Maybe the fastest way is just to run:
Or using jsonpath:
k config view -o jsonpath="{.contexts[*].name}"
k config view -o jsonpath="{.contexts[*].name}" | tr " " "\n" # new lines
k config view -o jsonpath="{.contexts[*].name}" | tr " " "\n" > /opt/course/1/contexts
#/opt/course/1/contexts
gianna@infra-prod
infra-prod
restricted@infra-prod
workload-prod
workload-stage
k config view --raw -ojsonpath="{.users[2].user.client-certificate-data}" | base64 -d > /opt/course/1/cert
Or even:
k config view --raw -ojsonpath="{.users[?(.name == 'restricted@infra-prod')].user.client-certificate-data}" | base64 -d > /opt/course/1/cert
# /opt/course/1/cert
-----BEGIN CERTIFICATE-----
MIIDHzCCAgegAwIBAgIQN5Qe/Rj/PhaqckEI23LPnjANBgkqhkiG9w0BAQsFADAV
MRMwEQYDVQQDEwprdWJlcm5ldGVzMB4XDTIwMDkyNjIwNTUwNFoXDTIxMDkyNjIw
NTUwNFowKjETMBEGA1UEChMKcmVzdHJpY3RlZDETMBEGA1UEAxMKcmVzdHJpY3Rl
ZDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAL/Jaf/QQdijyJTWIDij
qa5p4oAh+xDBX3jR9R0G5DkmPU/FgXjxej3rTwHJbuxg7qjTuqQbf9Fb2AHcVtwH
gUjC12ODUDE+nVtap+hCe8OLHZwH7BGFWWscgInZOZW2IATK/YdqyQL5OKpQpFkx
iAknVZmPa2DTZ8FoyRESboFSTZj6y+JVA7ot0pM09jnxswstal9GZLeqioqfFGY6
YBO/Dg4DDsbKhqfUwJVT6Ur3ELsktZIMTRS5By4Xz18798eBiFAHvgJGq1TTwuPM
EhBfwYwgYbalL8DSHeFrelLBKgciwUKjr1lolnnuc1vhkX1peV1J3xrf6o2KkyMc
lY0CAwEAAaNWMFQwDgYDVR0PAQH/BAQDAgWgMBMGA1UdJQQMMAoGCCsGAQUFBwMC
MAwGA1UdEwEB/wQCMAAwHwYDVR0jBBgwFoAUPrspZIWR7YMN8vT5DF3s/LvpxPQw
DQYJKoZIhvcNAQELBQADggEBAIDq0Zt77gXI1s+uW46zBw4mIWgAlBLl2QqCuwmV
kd86eH5bD0FCtWlb6vGdcKPdFccHh8Z6z2LjjLu6UoiGUdIJaALhbYNJiXXi/7cf
M7sqNOxpxQ5X5hyvOBYD1W7d/EzPHV/lcbXPUDYFHNqBYs842LWSTlPQioDpupXp
FFUQPxsenNXDa4TbmaRvnK2jka0yXcqdiXuIteZZovp/IgNkfmx2Ld4/Q+Xlnscf
CFtWbjRa/0W/3EW/ghQ7xtC7bgcOHJesoiTZPCZ+dfKuUfH6d1qxgj6Jwt0HtyEf
QTQSc66BdMLnw5DMObs4lXDo2YE6LvMrySdXm/S7img5YzU=
-----END CERTIFICATE-----
Question 2 | Runtime Security with Falco
Task weight: 4%
Use context: kubectl config use-context workload-prod
Falco is installed with default configuration on node cluster1-node1. Connect using ssh cluster1-node1. Use it to:
Find a Pod running image nginx which creates unwanted package management processes inside its container. Find a Pod running image httpd which modifies /etc/passwd. Save the Falco logs for case 1 under /opt/course/2/falco.log in format:
time-with-nanosconds,container-id,container-name,user-name
No other information should be in any line. Collect the logs for at least 30 seconds.
Afterwards remove the threads (both 1 and 2) by scaling the replicas of the Deployments that control the offending Pods down to 0.
Answer: Falco, the open-source cloud-native runtime security project, is the de facto Kubernetes threat detection engine.
NOTE: Other tools you might have to be familar with are sysdig or tracee
Use Falco as service
First we can investigate Falco config a little:
➜ ssh cluster1-node1
➜ root@cluster1-node1:~# service falco status
● falco.service - LSB: Falco syscall activity monitoring agent
Loaded: loaded (/etc/init.d/falco; generated)
Active: active (running) since Sat 2020-10-10 06:36:15 UTC; 2h 1min ago
...
➜ root@cluster1-node1:~# cd /etc/falco
➜ root@cluster1-node1:/etc/falco# ls
falco.yaml falco_rules.local.yaml falco_rules.yaml k8s_audit_rules.yaml rules.available rules.d
This is the default configuration, if we look into falco.yaml we can see:
# /etc/falco/falco.yaml
...
# Where security notifications should go.
# Multiple outputs can be enabled.
syslog_output:
enabled: true
...
This means that Falco is writing into syslog, hence we can do:
➜ root@cluster1-node1:~# cat /var/log/syslog | grep falco
Sep 15 08:44:04 ubuntu2004 falco: Falco version 0.29.1 (driver version 17f5df52a7d9ed6bb12d3b1768460def8439936d)
Sep 15 08:44:04 ubuntu2004 falco: Falco initialized with configuration file /etc/falco/falco.yaml
Sep 15 08:44:04 ubuntu2004 falco: Loading rules from file /etc/falco/falco_rules.yaml:
...
Yep, quite some action going on in there. Let's investigate the first offending Pod:
➜ root@cluster1-node1:~# cat /var/log/syslog | grep falco | grep nginx | grep process
Sep 16 06:23:47 ubuntu2004 falco: 06:23:47.376241377: Error Package management process launched in container (user=root user_loginuid=-1 command=apk container_id=7a5ea6a080d1 container_name=nginx image=docker.io/library/nginx:1.19.2-alpine)
...
➜ root@cluster1-node1:~# crictl ps -id 7a5ea6a080d1
CONTAINER ID IMAGE NAME ... POD ID
7a5ea6a080d1b 6f715d38cfe0e nginx ... 7a864406b9794
root@cluster1-node1:~# crictl pods -id 7a864406b9794
POD ID ... NAME NAMESPACE ...
7a864406b9794 ... webapi-6cfddcd6f4-ftxg4 team-blue ...
First Pod is webapi-6cfddcd6f4-ftxg4 in Namespace team-blue.
➜ root@cluster1-node1:~# cat /var/log/syslog | grep falco | grep httpd | grep passwd
Sep 16 06:23:48 ubuntu2004 falco: 06:23:48.830962378: Error File below /etc opened for writing (user=root user_loginuid=-1 command=sed -i $d /etc/passwd parent=sh pcmdline=sh -c echo hacker >> /etc/passwd; sed -i '$d' /etc/passwd; true file=/etc/passwdngFmAl program=sed gparent=<NA> ggparent=<NA> gggparent=<NA> container_id=b1339d5cc2de image=docker.io/library/httpd)
➜ root@cluster1-node1:~# crictl ps -id b1339d5cc2de
CONTAINER ID IMAGE NAME ... POD ID
b1339d5cc2dee f6b40f9f8ad71 httpd ... 595af943c3245
root@cluster1-node1:~# crictl pods -id 595af943c3245
POD ID ... NAME NAMESPACE ...
595af943c3245 ... rating-service-68cbdf7b7-v2p6g team-purple ...
Second Pod is rating-service-68cbdf7b7-v2p6g in Namespace team-purple.
Eliminate offending Pods
The logs from before should allow us to find and "eliminate" the offending Pods:
➜ k get pod -A | grep webapi
team-blue webapi-6cfddcd6f4-ftxg4 1/1 Running
➜ k -n team-blue scale deploy webapi --replicas 0
deployment.apps/webapi scaled
➜ k get pod -A | grep rating-service
team-purple rating-service-68cbdf7b7-v2p6g 1/1 Running
➜ k -n team-purple scale deploy rating-service --replicas 0
deployment.apps/rating-service scaled
Use Falco from command line
We can also use Falco directly from command line, but only if the service is disabled:
➜ root@cluster1-node1:~# service falco stop
➜ root@cluster1-node1:~# falco
Thu Sep 16 06:33:11 2021: Falco version 0.29.1 (driver version 17f5df52a7d9ed6bb12d3b1768460def8439936d)
Thu Sep 16 06:33:11 2021: Falco initialized with configuration file /etc/falco/falco.yaml
Thu Sep 16 06:33:11 2021: Loading rules from file /etc/falco/falco_rules.yaml:
Thu Sep 16 06:33:11 2021: Loading rules from file /etc/falco/falco_rules.local.yaml:
Thu Sep 16 06:33:11 2021: Loading rules from file /etc/falco/k8s_audit_rules.yaml:
Thu Sep 16 06:33:12 2021: Starting internal webserver, listening on port 8765
06:33:17.382603204: Error Package management process launched in container (user=root user_loginuid=-1 command=apk container_id=7a5ea6a080d1 container_name=nginx image=docker.io/library/nginx:1.19.2-alpine)
...
We can see that rule files are loaded and logs printed afterwards.
Create logs in correct format
The task requires us to store logs for "unwanted package management processes" in format time,container-id,container-name,user-name. The output from falco shows entries for "Error Package management process launched" in a default format. Let's find the proper file that contains the rule and change it:
➜ root@cluster1-node1:~# cd /etc/falco/
➜ root@cluster1-node1:/etc/falco# grep -r "Package management process launched" .
./falco_rules.yaml: Package management process launched in container (user=%user.name user_loginuid=%user.loginuid
➜ root@cluster1-node1:/etc/falco# cp falco_rules.yaml falco_rules.yaml_ori
➜ root@cluster1-node1:/etc/falco# vim falco_rules.yaml
Find the rule which looks like this:
# Container is supposed to be immutable. Package management should be done in building the image.
- rule: Launch Package Management Process in Container
desc: Package management process ran inside container
condition: >
spawned_process
and container
and user.name != "_apt"
and package_mgmt_procs
and not package_mgmt_ancestor_procs
and not user_known_package_manager_in_container
output: >
Package management process launched in container (user=%user.name user_loginuid=%user.loginuid
command=%proc.cmdline container_id=%container.id container_name=%container.name image=%container.image.repository:%container.image.tag)
priority: ERROR
tags: [process, mitre_persistence]
# Container is supposed to be immutable. Package management should be done in building the image.
- rule: Launch Package Management Process in Container
desc: Package management process ran inside container
condition: >
spawned_process
and container
and user.name != "_apt"
and package_mgmt_procs
and not package_mgmt_ancestor_procs
and not user_known_package_manager_in_container
output: >
Package management process launched in container %evt.time,%container.id,%container.name,%user.name
priority: ERROR
tags: [process, mitre_persistence]
For all available fields we can check https://falco.org/docs/rules/supported-fields, which should be allowed to open during the exam.
Next we check the logs in our adjusted format:
➜ root@cluster1-node1:/etc/falco# falco | grep "Package management"
06:38:28.077150666: Error Package management process launched in container 06:38:28.077150666,090aad374a0a,nginx,root
06:38:33.058263010: Error Package management process launched in container 06:38:33.058263010,090aad374a0a,nginx,root
06:38:38.068693625: Error Package management process launched in container 06:38:38.068693625,090aad374a0a,nginx,root
06:38:43.066159360: Error Package management process launched in container 06:38:43.066159360,090aad374a0a,nginx,root
06:38:48.059792139: Error Package management process launched in container 06:38:48.059792139,090aad374a0a,nginx,root
06:38:53.063328933: Error Package management process launched in container 06:38:53.063328933,090aad374a0a,nginx,root
This looks much better. Copy&paste the output into file /opt/course/2/falco.log on your main terminal. The content should be cleaned like this:
# /opt/course/2/falco.log
06:38:28.077150666,090aad374a0a,nginx,root
06:38:33.058263010,090aad374a0a,nginx,root
06:38:38.068693625,090aad374a0a,nginx,root
06:38:43.066159360,090aad374a0a,nginx,root
06:38:48.059792139,090aad374a0a,nginx,root
06:38:53.063328933,090aad374a0a,nginx,root
06:38:58.070912841,090aad374a0a,nginx,root
06:39:03.069592140,090aad374a0a,nginx,root
06:39:08.064805371,090aad374a0a,nginx,root
06:39:13.078109098,090aad374a0a,nginx,root
06:39:18.065077287,090aad374a0a,nginx,root
06:39:23.061012151,090aad374a0a,nginx,root
For a few entries it should be fast to just clean it up manually. If there are larger amounts of entries we could do:
The tool cut will split input into fields using space as the delimiter (-d""). We then only select the 9th field using -f 9.Local falco rules
There is also a file /etc/falco/falco_rules.local.yaml in which we can override existing default rules. This is a much cleaner solution for production. Choose the faster way for you in the exam if nothing is specified in the task.
Question 3 | Apiserver Security
Task weight: 3%
Use context: kubectl config use-context workload-prod
You received a list from the DevSecOps team which performed a security investigation of the k8s cluster1 (workload-prod). The list states the following about the apiserver setup:
- Accessible through a NodePort Service
Change the apiserver setup so that:
- Only accessible through a ClusterIP Service
Answer:
In order to modify the parameters for the apiserver, we first ssh into the master node and check which parameters the apiserver process is running with:
➜ ssh cluster1-controlplane1
➜ root@cluster1-controlplane1:~# ps aux | grep kube-apiserver
root 13534 8.6 18.1 1099208 370684 ? Ssl 19:55 8:40 kube-apiserver --advertise-address=192.168.100.11 --allow-privileged=true --anonymous-auth=true --authorization-mode=Node,RBAC --client-ca-file=/etc/kubernetes/pki/ca.crt --enable-admission-plugins=NodeRestriction --enable-bootstrap-token-auth=true --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key --etcd-servers=https://127.0.0.1:2379 --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname --kubernetes-service-node-port=31000 --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt --proxy-client-key-
...
➜ root@cluster1-controlplane1:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes NodePort 10.96.0.1 <none> 443:31000/TCP 5d2h
➜ root@cluster1-controlplane1:~# cp /etc/kubernetes/manifests/kube-apiserver.yaml ~/3_kube-apiserver.yaml
➜ root@cluster1-controlplane1:~# vim /etc/kubernetes/manifests/kube-apiserver.yaml
We should remove the unsecure settings:
# /etc/kubernetes/manifests/kube-apiserver.yaml
apiVersion: v1
kind: Pod
metadata:
annotations:
kubeadm.kubernetes.io/kube-apiserver.advertise-address.endpoint: 192.168.100.11:6443
creationTimestamp: null
labels:
component: kube-apiserver
tier: control-plane
name: kube-apiserver
namespace: kube-system
spec:
containers:
- command:
- kube-apiserver
- --advertise-address=192.168.100.11
- --allow-privileged=true
- --authorization-mode=Node,RBAC
- --client-ca-file=/etc/kubernetes/pki/ca.crt
- --enable-admission-plugins=NodeRestriction
- --enable-bootstrap-token-auth=true
- --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt
- --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt
- --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key
- --etcd-servers=https://127.0.0.1:2379
- --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt
- --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key
- --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
# - --kubernetes-service-node-port=31000 # delete or set to 0
- --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt
- --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key
...
Once the changes are made, give the apiserver some time to start up again. Check the apiserver's Pod status and the process parameters:
➜ root@cluster1-controlplane1:~# kubectl -n kube-system get pod | grep apiserver
kube-apiserver-cluster1-controlplane1 1/1 Running 0 38s
➜ root@cluster1-controlplane1:~# ps aux | grep kube-apiserver | grep node-port
The apiserver got restarted without the unsecure settings. However, the Service kubernetes will still be of type NodePort:
➜ root@cluster1-controlplane1:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes NodePort 10.96.0.1 <none> 443:31000/TCP 5d3h
We need to delete the Service for the changes to take effect:
➜ root@cluster1-controlplane1:~# kubectl delete svc kubernetes
service "kubernetes" deleted
After a few seconds:
➜ root@cluster1-controlplane1:~# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 6s
This should satisfy the DevSecOps team.
Question 4 | Pod Security Standard
Task weight: 8%
Use context: kubectl config use-context workload-prod
There is Deployment container-host-hacker in Namespace team-red which mounts /run/containerd as a hostPath volume on the Node where its running. This means that the Pod can access various data about other containers running on the same Node.
To prevent this configure Namespace team-red to enforce the baseline Pod Security Standard. Once completed, delete the Pod of the Deployment mentioned above.
Check the ReplicaSet events and write the event/log lines containing the reason why the Pod isn't recreated into /opt/course/4/logs.
Answer:
Making Namespaces use Pod Security Standards works via labels. We can simply edit it:
Now we configure the requested label:
# kubectl edit namespace team-red
apiVersion: v1
kind: Namespace
metadata:
labels:
kubernetes.io/metadata.name: team-red
pod-security.kubernetes.io/enforce: baseline # add
name: team-red
...
This should already be enough for the default Pod Security Admission Controller to pick up on that change. Let's test it and delete the Pod to see if it'll be recreated or fails, it should fail!
➜ k -n team-red get pod
NAME READY STATUS RESTARTS AGE
container-host-hacker-dbf989777-wm8fc 1/1 Running 0 115s
➜ k -n team-red delete pod container-host-hacker-dbf989777-wm8fc
pod "container-host-hacker-dbf989777-wm8fc" deleted
➜ k -n team-red get pod
No resources found in team-red namespace.
Usually the ReplicaSet of a Deployment would recreate the Pod if deleted, here we see this doesn't happen. Let's check why:
➜ k -n team-red get rs
NAME DESIRED CURRENT READY AGE
container-host-hacker-dbf989777 1 0 0 5m25s
➜ k -n team-red describe rs container-host-hacker-dbf989777
Name: container-host-hacker-dbf989777
Namespace: team-red
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
...
Warning FailedCreate 2m41s replicaset-controller Error creating: pods "container-host-hacker-dbf989777-bjwgv" is forbidden: violates PodSecurity "baseline:latest": hostPath volumes (volume "containerdata")
Warning FailedCreate 2m2s (x9 over 2m40s) replicaset-controller (combined from similar events): Error creating: pods "container-host-hacker-dbf989777-kjfpn" is forbidden: violates PodSecurity "baseline:latest": hostPath volumes (volume "containerdata")
# /opt/course/4/logs
Warning FailedCreate 2m2s (x9 over 2m40s) replicaset-controller (combined from similar events): Error creating: pods "container-host-hacker-dbf989777-kjfpn" is forbidden: violates PodSecurity "baseline:latest": hostPath volumes (volume "containerdata")
Pod Security Standards can give a great base level of security! But when one finds themselves wanting to deeper adjust the levels like baseline or restricted... this isn't possible and 3rd party solutions like OPA could be looked at.
Question 5 | CIS Benchmark
Task weight: 3%
Use context: kubectl config use-context infra-prod
You're ask to evaluate specific settings of cluster2 against the CIS Benchmark recommendations. Use the tool kube-bench which is already installed on the nodes.
Connect using ssh cluster2-controlplane1 and ssh cluster2-node1.
On the master node ensure (correct if necessary) that the CIS recommendations are set for:
-
The --profiling argument of the kube-controller-manager
-
The ownership of directory /var/lib/etcd
On the worker node ensure (correct if necessary) that the CIS recommendations are set for:
- The permissions of the kubelet configuration /var/lib/kubelet/config.yaml
- The --client-ca-file argument of the kubelet
Answer:
Number 1
First we ssh into the master node run kube-bench against the master components:
➜ ssh cluster2-controlplane1
➜ root@cluster2-controlplane1:~# kube-bench run --targets=master
...
== Summary ==
41 checks PASS
13 checks FAIL
11 checks WARN
0 checks INFO
We see some passes, fails and warnings. Let's check the required task (1) of the controller manager:
➜ root@cluster2-controlplane1:~# kube-bench run --targets=master | grep kube-controller -A 3
1.3.1 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master node and set the --terminated-pod-gc-threshold to an appropriate threshold,
for example:
--terminated-pod-gc-threshold=10
--
1.3.2 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master node and set the below parameter.
--profiling=false
1.3.6 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master node and set the --feature-gates parameter to include RotateKubeletServerCertificate=true.
--feature-gates=RotateKubeletServerCertificate=true
There we see 1.3.2 which suggests to set --profiling=false, so we obey:
Edit the corresponding line:# /etc/kubernetes/manifests/kube-controller-manager.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
component: kube-controller-manager
tier: control-plane
name: kube-controller-manager
namespace: kube-system
spec:
containers:
- command:
- kube-controller-manager
- --allocate-node-cidrs=true
- --authentication-kubeconfig=/etc/kubernetes/controller-manager.conf
- --authorization-kubeconfig=/etc/kubernetes/controller-manager.conf
- --bind-address=127.0.0.1
- --client-ca-file=/etc/kubernetes/pki/ca.crt
- --cluster-cidr=10.244.0.0/16
- --cluster-name=kubernetes
- --cluster-signing-cert-file=/etc/kubernetes/pki/ca.crt
- --cluster-signing-key-file=/etc/kubernetes/pki/ca.key
- --controllers=*,bootstrapsigner,tokencleaner
- --kubeconfig=/etc/kubernetes/controller-manager.conf
- --leader-elect=true
- --node-cidr-mask-size=24
- --port=0
- --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
- --root-ca-file=/etc/kubernetes/pki/ca.crt
- --service-account-private-key-file=/etc/kubernetes/pki/sa.key
- --service-cluster-ip-range=10.96.0.0/12
- --use-service-account-credentials=true
- --profiling=false # add
...
We wait for the Pod to restart, then run kube-bench again to check if the problem was solved:
➜ root@cluster2-controlplane1:~# kube-bench run --targets=master | grep kube-controller -A 3
1.3.1 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master node and set the --terminated-pod-gc-threshold to an appropriate threshold,
for example:
--terminated-pod-gc-threshold=10
--
1.3.6 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master node and set the --feature-gates parameter to include RotateKubeletServerCertificate=true.
--feature-gates=RotateKubeletServerCertificate=true
Problem solved and 1.3.2 is passing:
root@cluster2-controlplane1:~# kube-bench run --targets=master | grep 1.3.2
[PASS] 1.3.2 Ensure that the --profiling argument is set to false (Scored)
Number 2
Next task (2) is to check the ownership of directory /var/lib/etcd, so we first have a look:
➜ root@cluster2-controlplane1:~# ls -lh /var/lib | grep etcd
drwx------ 3 root root 4.0K Sep 11 20:08 etcd
Looks like user root and group root. Also possible to check using:
But what has kube-bench to say about this?➜ root@cluster2-controlplane1:~# kube-bench run --targets=master | grep "/var/lib/etcd" -B5
1.1.12 On the etcd server node, get the etcd data directory, passed as an argument --data-dir,
from the below command:
ps -ef | grep etcd
Run the below command (based on the etcd data directory found above).
For example, chown etcd:etcd /var/lib/etcd
To comply we run the following:
➜ root@cluster2-controlplane1:~# chown etcd:etcd /var/lib/etcd
➜ root@cluster2-controlplane1:~# ls -lh /var/lib | grep etcd
drwx------ 3 etcd etcd 4.0K Sep 11 20:08 etcd
This looks better. We run kube-bench again, and make sure test 1.1.12. is passing.
➜ root@cluster2-controlplane1:~# kube-bench run --targets=master | grep 1.1.12
[PASS] 1.1.12 Ensure that the etcd data directory ownership is set to etcd:etcd (Scored)
Done.
Number 3
To continue with number (3), we'll head to the worker node and ensure that the kubelet configuration file has the minimum necessary permissions as recommended:
➜ ssh cluster2-node1
➜ root@cluster2-node1:~# kube-bench run --targets=node
...
== Summary ==
13 checks PASS
10 checks FAIL
2 checks WARN
0 checks INFO
Also here some passes, fails and warnings. We check the permission level of the kubelet config file:
777 is highly permissive access level and not recommended by the kube-bench guidelines:
➜ root@cluster2-node1:~# kube-bench run --targets=node | grep /var/lib/kubelet/config.yaml -B2
4.1.9 Run the following command (using the config file location identified in the Audit step)
chmod 644 /var/lib/kubelet/config.yaml
We obey and set the recommended permissions:
➜ root@cluster2-node1:~# chmod 644 /var/lib/kubelet/config.yaml
➜ root@cluster2-node1:~# stat -c %a /var/lib/kubelet/config.yaml
644
And check if test 2.2.10 is passing:
➜ root@cluster2-node1:~# kube-bench run --targets=node | grep 4.1.9
[PASS] 2.2.10 Ensure that the kubelet configuration file has permissions set to 644 or more restrictive (Scored)
Number 4
Finally for number (4), let's check whether --client-ca-file argument for the kubelet is set properly according to kube-bench recommendations:
➜ root@cluster2-node1:~# kube-bench run --targets=node | grep client-ca-file
[PASS] 4.2.3 Ensure that the --client-ca-file argument is set as appropriate (Automated)
This looks passing with 4.2.3. The other ones are about the file that the parameter points to and can be ignored here.
To further investigate we run the following command to locate the kubelet config file, and open it:
➜ root@cluster2-node1:~# ps -ef | grep kubelet
root 5157 1 2 20:28 ? 00:03:22 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.2
root 19940 11901 0 22:38 pts/0 00:00:00 grep --color=auto kubelet
➜ root@croot@cluster2-node1:~# vim /var/lib/kubelet/config.yaml
# /var/lib/kubelet/config.yaml
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
anonymous:
enabled: false
webhook:
cacheTTL: 0s
enabled: true
x509:
clientCAFile: /etc/kubernetes/pki/ca.crt
...
Question 6 | Verify Platform Binaries
Task weight: 2%
(can be solved in any kubectl context)
There are four Kubernetes server binaries located at /opt/course/6/binaries. You're provided with the following verified sha512 values for these:
kube-apiserver
f417c0555bc0167355589dd1afe23be9bf909bf98312b1025f12015d1b58a1c62c9908c0067a7764fa35efdac7016a9efa8711a44425dd6692906a7c283f032c
kube-controller-manager
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33boa8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60
kube-proxy
52f9d8ad045f8eee1d689619ef8ceef2d86d50c75a6a332653240d7ba5b2a114aca056d9e513984ade24358c9662714973c1960c62a5cb37dd375631c8a614c6
kubelet
4be40f2440619e990897cf956c32800dc96c2c983bf64519854a3309fa5aa21827991559f9c44595098e27e6f2ee4d64a3fdec6baba8a177881f20e3ec61e26c
Delete those binaries that don't match with the sha512 values above.
Answer:
We check the directory:
To generate the sha512 sum of a binary we do:
➜ sha512sum kube-apiserver
f417c0555bc0167355589dd1afe23be9bf909bf98312b1025f12015d1b58a1c62c9908c0067a7764fa35efdac7016a9efa8711a44425dd6692906a7c283f032c kube-apiserver
Looking good, next:
➜ sha512sum kube-controller-manager
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33b0a8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60 kube-controller-manager
Okay, next:
➜ sha512sum kube-proxy
52f9d8ad045f8eee1d689619ef8ceef2d86d50c75a6a332653240d7ba5b2a114aca056d9e513984ade24358c9662714973c1960c62a5cb37dd375631c8a614c6 kube-proxy
Also good, and finally:
➜ sha512sum kubelet
7b720598e6a3483b45c537b57d759e3e82bc5c53b3274f681792f62e941019cde3d51a7f9b55158abf3810d506146bc0aa7cf97b36f27f341028a54431b335be kubelet
Catch! Binary kubelet has a different hash!
But did we actually compare everything properly before? Let's have a closer look at kube-controller-manager again:
Edit to only have the provided hash and the generated one in one line each:
# ./compare
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33b0a8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33boa8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60
Looks right at a first glance, but if we do:
➜ cat compare | uniq
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33b0a8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60
60100cc725e91fe1a949e1b2d0474237844b5862556e25c2c655a33boa8225855ec5ee22fa4927e6c46a60d43a7c4403a27268f96fbb726307d1608b44f38a60
This shows they are different, by just one character actually.
To complete the task we do:
Question 7 | Open Policy Agent
Task weight: 6%
Use context: kubectl config use-context infra-prod
The Open Policy Agent and Gatekeeper have been installed to, among other things, enforce blacklisting of certain image registries. Alter the existing constraint and/or template to also blacklist images from very-bad-registry.com.
Test it by creating a single Pod using image very-bad-registry.com/image in Namespace default, it shouldn't work.
You can also verify your changes by looking at the existing Deployment untrusted in Namespace default, it uses an image from the new untrusted source. The OPA contraint should throw violation messages for this one.
Answer:
We look at existing OPA constraints, these are implemeted using CRDs by Gatekeeper:
➜ k get crd
NAME CREATED AT
blacklistimages.constraints.gatekeeper.sh 2020-09-14T19:29:31Z
configs.config.gatekeeper.sh 2020-09-14T19:29:04Z
constraintpodstatuses.status.gatekeeper.sh 2020-09-14T19:29:05Z
constrainttemplatepodstatuses.status.gatekeeper.sh 2020-09-14T19:29:05Z
constrainttemplates.templates.gatekeeper.sh 2020-09-14T19:29:05Z
requiredlabels.constraints.gatekeeper.sh 2020-09-14T19:29:31Z
So we can do:
➜ k get constraint
NAME AGE
blacklistimages.constraints.gatekeeper.sh/pod-trusted-images 10m
NAME AGE
requiredlabels.constraints.gatekeeper.sh/namespace-mandatory-labels 10m
and then look at the one that is probably about blacklisting images:
# kubectl edit blacklistimages pod-trusted-images
apiVersion: constraints.gatekeeper.sh/v1beta1
kind: BlacklistImages
metadata:
...
spec:
match:
kinds:
- apiGroups:
- ""
kinds:
- Pod
````
It looks like this constraint simply applies the template to all Pods, no arguments passed. So we edit the template:
```sh
k edit constrainttemplates blacklistimages
# kubectl edit constrainttemplates blacklistimages
apiVersion: templates.gatekeeper.sh/v1beta1
kind: ConstraintTemplate
metadata:
...
spec:
crd:
spec:
names:
kind: BlacklistImages
targets:
- rego: |
package k8strustedimages
images {
image := input.review.object.spec.containers[_].image
not startswith(image, "docker-fake.io/")
not startswith(image, "google-gcr-fake.com/")
not startswith(image, "very-bad-registry.com/") # ADD THIS LINE
}
violation[{"msg": msg}] {
not images
msg := "not trusted image!"
}
target: admission.k8s.gatekeeper.sh
We simply have to add another line. After editing we try to create a Pod of the bad image:
➜ k run opa-test --image=very-bad-registry.com/image
Error from server ([denied by pod-trusted-images] not trusted image!): admission webhook "validation.gatekeeper.sh" denied the request: [denied by pod-trusted-images] not trusted image!
Nice! After some time we can also see that Pods of the existing Deployment "untrusted" will be listed as violators:
➜ k describe blacklistimages pod-trusted-images
...
Total Violations: 2
Violations:
Enforcement Action: deny
Kind: Namespace
Message: you must provide labels: {"security-level"}
Name: sidecar-injector
Enforcement Action: deny
Kind: Pod
Message: not trusted image!
Name: untrusted-68c4944d48-tfsnb
Namespace: default
Events: <none>
Great, OPA fights bad registries !
Question 8 | Secure Kubernetes Dashboard
Task weight: 3%
Use context: kubectl config use-context workload-prod
The Kubernetes Dashboard is installed in Namespace kubernetes-dashboard and is configured to:
- Allow users to "skip login"
- Allow insecure access (HTTP without authentication)
- Allow basic authentication
- Allow access from outside the cluster
You are asked to make it more secure by:
- Deny users to "skip login"
- Deny insecure access, enforce HTTPS (self signed certificates are ok for now)
- Add the --auto-generate-certificates argument
- Enforce authentication using a token (with possibility to use RBAC)
- Allow only cluster internal access
Answer:
Head to https://github.com/kubernetes/dashboard/tree/master/docs to find documentation about the dashboard. This link is not on the allowed list of urls during the real exam. This means you should be provided will all information necessary in case of a task like this.
First we have a look in Namespace kubernetes-dashboard:
➜ k -n kubernetes-dashboard get pod,svc
NAME READY STATUS RESTARTS AGE
pod/dashboard-metrics-scraper-7b59f7d4df-fbpd9 1/1 Running 0 24m
pod/kubernetes-dashboard-6d8cd5dd84-w7wr2 1/1 Running 0 24m
NAME TYPE ... PORT(S) AGE
service/dashboard-metrics-scraper ClusterIP ... 8000/TCP 24m
service/kubernetes-dashboard NodePort ... 9090:32520/TCP,443:31206/TCP 24m
We can see one running Pod and a NodePort Service exposing it. Let's try to connect to it via a NodePort, we can use IP of any Node:
(your port might be a different)
➜ k get node -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP ...
cluster1-controlplane1 Ready master 37m v1.24.1 192.168.100.11 ...
cluster1-node1 Ready <none> 36m v1.24.1 192.168.100.12 ...
cluster1-node2 Ready <none> 34m v1.24.1 192.168.100.13 ...
➜ curl http://192.168.100.11:32520
<!--
Copyright 2017 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
The dashboard is not secured because it allows unsecure HTTP access without authentication and is exposed externally. It's is loaded with a few parameter making it insecure, let's fix this.
First we create a backup in case we need to undo something:
k -n kubernetes-dashboard get deploy kubernetes-dashboard -oyaml > 8_deploy_kubernetes-dashboard.yaml
Then:
The changes to make are :
template:
spec:
containers:
- args:
- --namespace=kubernetes-dashboard
- --authentication-mode=token # change or delete, "token" is default
- --auto-generate-certificates # add
#- --enable-skip-login=true # delete or set to false
#- --enable-insecure-login # delete
image: kubernetesui/dashboard:v2.0.3
imagePullPolicy: Always
name: kubernetes-dashboard
Next, we'll have to deal with the NodePort Service:
k -n kubernetes-dashboard get svc kubernetes-dashboard -o yaml > 8_svc_kubernetes-dashboard.yaml # backup
k -n kubernetes-dashboard edit svc kubernetes-dashboard
And make the following changes:
spec:
clusterIP: 10.107.176.19
externalTrafficPolicy: Cluster # delete
internalTrafficPolicy: Cluster
ports:
- name: http
nodePort: 32513 # delete
port: 9090
protocol: TCP
targetPort: 9090
- name: https
nodePort: 32441 # delete
port: 443
protocol: TCP
targetPort: 8443
selector:
k8s-app: kubernetes-dashboard
sessionAffinity: None
type: ClusterIP # change or delete
status:
loadBalancer: {}
Let's confirm the changes, we can do that even without having a browser:
➜ k run tmp --image=nginx:1.19.2 --restart=Never --rm -it -- bash
If you don't see a command prompt, try pressing enter.
root@tmp:/# curl http://kubernetes-dashboard.kubernetes-dashboard:9090
curl: (7) Failed to connect to kubernetes-dashboard.kubernetes-dashboard port 9090: Connection refused
➜ root@tmp:/# curl https://kubernetes-dashboard.kubernetes-dashboard
curl: (60) SSL certificate problem: self signed certificate
More details here: https://curl.haxx.se/docs/sslcerts.html
curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
➜ root@tmp:/# curl https://kubernetes-dashboard.kubernetes-dashboard -k
<!--
Copyright 2017 The Kubernetes Authors.
We see that insecure access is disabled and HTTPS works (using a self signed certificate for now). Let's also check the remote access:
(your port might be a different)
➜ curl http://192.168.100.11:32520
curl: (7) Failed to connect to 192.168.100.11 port 32520: Connection refused
➜ k -n kubernetes-dashboard get svc
NAME TYPE CLUSTER-IP ... PORT(S)
dashboard-metrics-scraper ClusterIP 10.111.171.247 ... 8000/TCP
kubernetes-dashboard ClusterIP 10.100.118.128 ... 9090/TCP,443/TCP
Much better.
Question 9 | AppArmor Profile
Task weight: 3%
Use context: kubectl config use-context workload-prod
Some containers need to run more secure and restricted. There is an existing AppArmor profile located at /opt/course/9/profile for this.
-
Install the AppArmor profile on Node
cluster1-node1. Connect usingssh cluster1-node1. -
Add label
security=apparmorto the Node -
Create a Deployment named
apparmorin Namespacedefaultwith: - One replica of image
nginx:1.19.2 - NodeSelector for
security=apparmor - Single container named c1 with the AppArmor profile enabled
The Pod might not run properly with the profile enabled. Write the logs of the Pod into /opt/course/9/logs so another team can work on getting the application running.
Answer:
https://kubernetes.io/docs/tutorials/clusters/apparmor
Part 1
First we have a look at the provided profile:
# /opt/course/9/profile
#include <tunables/global>
profile very-secure flags=(attach_disconnected) {
#include <abstractions/base>
file,
# Deny all file writes.
deny /** w,
}
Very simple profile named very-secure which denies all file writes. Next we copy it onto the Node:
➜ scp /opt/course/9/profile cluster1-node1:~/
Warning: Permanently added the ECDSA host key for IP address '192.168.100.12' to the list of known hosts.
profile 100% 161 329.9KB/s 00:00
➜ ssh cluster1-node1
➜ root@cluster1-node1:~# ls
profile
And install it:
Verify it has been installed:
➜ root@cluster1-node1:~# apparmor_status
apparmor module is loaded.
17 profiles are loaded.
17 profiles are in enforce mode.
/sbin/dhclient
...
man_filter
man_groff
very-secure
0 profiles are in complain mode.
56 processes have profiles defined.
56 processes are in enforce mode.
...
0 processes are in complain mode.
0 processes are unconfined but have a profile defined.
There we see among many others the very-secure one, which is the name of the profile specified in /opt/course/9/profile.
Part 2
We label the Node:
Part 3
Now we can go ahead and create the Deployment which uses the profile.
vim 9_deploy.yaml
# 9_deploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
creationTimestamp: null
labels:
app: apparmor
name: apparmor
namespace: default
spec:
replicas: 1
selector:
matchLabels:
app: apparmor
strategy: {}
template:
metadata:
creationTimestamp: null
labels:
app: apparmor
annotations: # add
container.apparmor.security.beta.kubernetes.io/c1: localhost/very-secure # add
spec:
nodeSelector: # add
security: apparmor # add
containers:
- image: nginx:1.19.2
name: c1 # change
resources: {}
````
```sh
k -f 9_deploy.yaml create
What the damage?
➜ k get pod -owide | grep apparmor
apparmor-85c65645dc-jbch8 0/1 CrashLoopBackOff ... cluster1-node1
➜ k logs apparmor-85c65645dc-w852p
/docker-entrypoint.sh: 13: /docker-entrypoint.sh: cannot create /dev/null: Permission denied
/docker-entrypoint.sh: No files found in /docker-entrypoint.d/, skipping configuration
2021/09/15 11:51:57 [emerg] 1#1: mkdir() "/var/cache/nginx/client_temp" failed (13: Permission denied)
nginx: [emerg] mkdir() "/var/cache/nginx/client_temp" failed (13: Permission denied)
This looks alright, the Pod is running on cluster1-node1 because of the nodeSelector. The AppArmor profile simply denies all filesystem writes, but Nginx needs to write into some locations to run, hence the errors.
It looks like our profile is running but we can confirm this as well by inspecting the container:
➜ ssh cluster1-node1
➜ root@cluster1-node1:~# crictl pods | grep apparmor
be5c0aecee7c7 4 minutes ago Ready apparmor-85c65645dc-jbch8 ...
➜ root@cluster1-node1:~# crictl ps -a | grep be5c0aecee7c7
e4d91cbdf72fb ... Exited c1 6 be5c0aecee7c7
➜ root@cluster1-node1:~# crictl inspect e4d91cbdf72fb | grep -i profile
"apparmor_profile": "localhost/very-secure",
"apparmorProfile": "very-secure",
First we find the Pod by it's name and get the pod-id. Next we use crictl ps -a to also show stopped containers. Then crictl inspect shows that the container is using our AppArmor profile. Notice to be fast between ps and inspect as K8s will restart the Pod periodically when in error state.
To complete the task we write the logs into the required location:
Fixing the errors is the job of another team, lucky us.
Question 10 | Container Runtime Sandbox gVisor
Task weight: 4%
Use context: kubectl config use-context workload-prod
Team purple wants to run some of their workloads more secure. Worker node cluster1-node2 has container engine containerd already installed and its configured to support the runsc/gvisor runtime.
Create a RuntimeClass named gvisor with handler runsc.
Create a Pod that uses the RuntimeClass. The Pod should be in Namespace team-purple, named gvisor-test and of image nginx:1.19.2. Make sure the Pod runs on cluster1-node2.
Write the dmesg output of the successfully started Pod into /opt/course/10/gvisor-test-dmesg.
Answer:
We check the nodes and we can see that all are using containerd:
➜ k get node -o wide
NAME STATUS ROLES ... CONTAINER-RUNTIME
cluster1-controlplane1 Ready control-plane ... containerd://1.5.2
cluster1-node1 Ready <none> ... containerd://1.5.2
cluster1-node2 Ready <none> ... containerd://1.5.2
But just one has containerd configured to work with runsc/gvisor runtime which is cluster1-node2.
(Optionally) we ssh into the worker node and check if containerd+runsc is configured:
➜ ssh cluster1-node2
➜ root@cluster1-node2:~# runsc --version
runsc version release-20201130.0
spec: 1.0.1-dev
➜ root@cluster1-node2:~# cat /etc/containerd/config.toml | grep runsc
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runsc]
runtime_type = "io.containerd.runsc.v1"
Now we best head to the k8s docs for RuntimeClasses https://kubernetes.io/docs/concepts/containers/runtime-class, steal an example and create the gvisor one:
vim 10_rtc.yaml
# 10_rtc.yaml
apiVersion: node.k8s.io/v1
kind: RuntimeClass
metadata:
name: gvisor
handler: runsc
And the required Pod:
vim 10_pod.yaml
# 10_pod.yaml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: gvisor-test
name: gvisor-test
namespace: team-purple
spec:
nodeName: cluster1-node2 # add
runtimeClassName: gvisor # add
containers:
- image: nginx:1.19.2
name: gvisor-test
resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}
After creating the pod we should check if its running and if it uses the gvisor sandbox:
➜ k -n team-purple get pod gvisor-test
NAME READY STATUS RESTARTS AGE
gvisor-test 1/1 Running 0 30s
➜ k -n team-purple exec gvisor-test -- dmesg
[ 0.000000] Starting gVisor...
[ 0.417740] Checking naughty and nice process list...
[ 0.623721] Waiting for children...
[ 0.902192] Gathering forks...
[ 1.258087] Committing treasure map to memory...
[ 1.653149] Generating random numbers by fair dice roll...
[ 1.918386] Creating cloned children...
[ 2.137450] Digging up root...
[ 2.369841] Forking spaghetti code...
[ 2.840216] Rewriting operating system in Javascript...
[ 2.956226] Creating bureaucratic processes...
[ 3.329981] Ready!
Question 11 | Secrets in ETCD
Task weight: 7%
Use context: kubectl config use-context workload-prod
There is an existing Secret called database-access in Namespace team-green.
Read the complete Secret content directly from ETCD (using etcdctl) and store it into /opt/course/11/etcd-secret-content. Write the plain and decoded Secret's value of key "pass" into /opt/course/11/database-password.
Answer:
Let's try to get the Secret value directly from ETCD, which will work since it isn't encrypted.
First, we ssh into the master node where ETCD is running in this setup and check if etcdctl is installed and list its options:
➜ ssh cluster1-controlplane1
➜ root@cluster1-controlplane1:~# etcdctl
NAME:
etcdctl - A simple command line client for etcd.
WARNING:
Environment variable ETCDCTL_API is not set; defaults to etcdctl v2.
Set environment variable ETCDCTL_API=3 to use v3 API or ETCDCTL_API=2 to use v2 API.
USAGE:
etcdctl [global options] command [command options] [arguments...]
...
--cert-file value identify HTTPS client using this SSL certificate file
--key-file value identify HTTPS client using this SSL key file
--ca-file value verify certificates of HTTPS-enabled servers using this CA bundle
...
Among others we see arguments to identify ourselves. The apiserver connects to ETCD, so we can run the following command to get the path of the necessary .crt and .key files:
The output is as follows :
- --etcd-cafile=/etc/kubernetes/pki/etcd/ca.crt
- --etcd-certfile=/etc/kubernetes/pki/apiserver-etcd-client.crt
- --etcd-keyfile=/etc/kubernetes/pki/apiserver-etcd-client.key
- --etcd-servers=https://127.0.0.1:2379 # optional since we're on same node
With this information we query ETCD for the secret value:
➜ root@cluster1-controlplane1:~# ETCDCTL_API=3 etcdctl \
--cert /etc/kubernetes/pki/apiserver-etcd-client.crt \
--key /etc/kubernetes/pki/apiserver-etcd-client.key \
--cacert /etc/kubernetes/pki/etcd/ca.crt get /registry/secrets/team-green/database-access
ETCD in Kubernetes stores data under /registry/{type}/{namespace}/{name}. This is how we came to look for /registry/secrets/team-green/database-access. There is also an example on a page in the k8s documentation which you could save as a bookmark to access fast during the exam.
The tasks requires us to store the output on our terminal. For this we can simply copy&paste the content into a new file on our terminal:
# /opt/course/11/etcd-secret-content
/registry/secrets/team-green/database-access
k8s
v1Secret
database-access
team-green"*$3e0acd78-709d-4f07-bdac-d5193d0f2aa32bB
0kubectl.kubernetes.io/last-applied-configuration{"apiVersion":"v1","data":{"pass":"Y29uZmlkZW50aWFs"},"kind":"Secret","metadata":{"annotations":{},"name":"database-access","namespace":"team-green"}}
z
kubectl-client-side-applyUpdatevFieldsV1:
{"f:data":{".":{},"f:pass":{}},"f:metadata":{"f:annotations":{".":{},"f:kubectl.kubernetes.io/last-applied-configuration":{}}},"f:type":{}}
pass
confidentialOpaque"
We're also required to store the plain and "decrypted" database password. For this we can copy the base64-encoded value from the ETCD output and run on our terminal:
➜ echo Y29uZmlkZW50aWFs | base64 -d > /opt/course/11/database-password
➜ cat /opt/course/11/database-password
confidential
Question 12 | Hack Secrets
Task weight: 8%
Use context: kubectl config use-context restricted@infra-prod
You're asked to investigate a possible permission escape in Namespace restricted. The context authenticates as user restricted which has only limited permissions and shouldn't be able to read Secret values.
Try to find the password-key values of the Secrets secret1, secret2 and secret3 in Namespace restricted. Write the decoded plaintext values into files /opt/course/12/secret1, /opt/course/12/secret2 and /opt/course/12/secret3.
Answer:
First we should explore the boundaries, we can try:
➜ k -n restricted get role,rolebinding,clusterrole,clusterrolebinding
Error from server (Forbidden): roles.rbac.authorization.k8s.io is forbidden: User "restricted" cannot list resource "roles" in API group "rbac.authorization.k8s.io" in the namespace "restricted"
Error from server (Forbidden): rolebindings.rbac.authorization.k8s.io is forbidden: User "restricted" cannot list resource "rolebindings" in API group "rbac.authorization.k8s.io" in the namespace "restricted"
Error from server (Forbidden): clusterroles.rbac.authorization.k8s.io is forbidden: User "restricted" cannot list resource "clusterroles" in API group "rbac.authorization.k8s.io" at the cluster scope
Error from server (Forbidden): clusterrolebindings.rbac.authorization.k8s.io is forbidden: User "restricted" cannot list resource "clusterrolebindings" in API group "rbac.authorization.k8s.io" at the cluster scope
But no permissions to view RBAC resources. So we try the obvious:
➜ k -n restricted get secret
Error from server (Forbidden): secrets is forbidden: User "restricted" cannot list resource "secrets" in API group "" in the namespace "restricted"
➜ k -n restricted get secret -o yaml
apiVersion: v1
items: []
kind: List
metadata:
resourceVersion: ""
selfLink: ""
Error from server (Forbidden): secrets is forbidden: User "restricted" cannot list resource "secrets" in API group "" in the namespace "restricted"
We're not allowed to get or list any Secrets. What can we see though?
➜ k -n restricted get all
NAME READY STATUS RESTARTS AGE
pod1-fd5d64b9c-pcx6q 1/1 Running 0 37s
pod2-6494f7699b-4hks5 1/1 Running 0 37s
pod3-748b48594-24s76 1/1 Running 0 37s
Error from server (Forbidden): replicationcontrollers is forbidden: User "restricted" cannot list resource "replicationcontrollers" in API group "" in the namespace "restricted"
Error from server (Forbidden): services is forbidden: User "restricted" cannot list resource "services" in API group "" in the namespace "restricted"
...
There are some Pods, lets check these out regarding Secret access:
This output provides us with enough information to do:
➜ k -n restricted exec pod1-fd5d64b9c-pcx6q -- cat /etc/secret-volume/password
you-are
➜ echo you-are > /opt/course/12/secret1
And for the second Secret:
➜ k -n restricted exec pod2-6494f7699b-4hks5 -- env | grep PASS
PASSWORD=an-amazing
➜ echo an-amazing > /opt/course/12/secret2
None of the Pods seem to mount secret3 though. Can we create or edit existing Pods to mount secret3?
➜ k -n restricted run test --image=nginx
Error from server (Forbidden): pods is forbidden: User "restricted" cannot create resource "pods" in API group "" in the namespace "restricted"
➜ k -n restricted delete pod pod1
Error from server (Forbidden): pods "pod1" is forbidden: User "restricted" cannot delete resource "pods" in API group "" in the namespace "restricted"
Doesn't look like it.
But the Pods seem to be able to access the Secrets, we can try to use a Pod's ServiceAccount to access the third Secret. We can actually see (like using k -n restricted get pod -o yaml | grep automountServiceAccountToken) that only Pod pod3-* has the ServiceAccount token mounted:
➜ k -n restricted exec -it pod3-748b48594-24s76 -- sh
/ # mount | grep serviceaccount
tmpfs on /run/secrets/kubernetes.io/serviceaccount type tmpfs (ro,relatime)
/ # ls /run/secrets/kubernetes.io/serviceaccount
ca.crt namespace token
NOTE: You should have knowledge about ServiceAccounts and how they work with Pods like described in the docs
We can see all necessary information to contact the apiserver manually:
/ # curl https://kubernetes.default/api/v1/namespaces/restricted/secrets -H "Authorization: Bearer $(cat /run/secrets/kubernetes.io/serviceaccount/token)" -k
...
{
"metadata": {
"name": "secret3",
"namespace": "restricted",
...
}
]
},
"data": {
"password": "cEVuRXRSYVRpT24tdEVzVGVSCg=="
},
"type": "Opaque"
}
...
Let's encode it and write it into the requested location:
➜ echo cEVuRXRSYVRpT24tdEVzVGVSCg== | base64 -d
pEnEtRaTiOn-tEsTeR
➜ echo cEVuRXRSYVRpT24tdEVzVGVSCg== | base64 -d > /opt/course/12/secret3
This will give us:
We hacked all Secrets! It can be tricky to get RBAC right and secure.
NOTE: One thing to consider is that giving the permission to "list" Secrets, will also allow the user to read the Secret values like using kubectl get secrets -o yaml even without the "get" permission set.
Question 13 | Restrict access to Metadata Server
Task weight: 7%
Use context: kubectl config use-context infra-prod
There is a metadata service available at http://192.168.100.21:32000 on which Nodes can reach sensitive data, like cloud credentials for initialisation. By default, all Pods in the cluster also have access to this endpoint. The DevSecOps team has asked you to restrict access to this metadata server.
In Namespace metadata-access:
- Create a NetworkPolicy named
metadata-denywhich prevents egress to192.168.100.21for all Pods but still allows access to everything else - Create a NetworkPolicy named
metadata-allowwhich allows Pods having labelrole: metadata-accessorto access endpoint192.168.100.21
There are existing Pods in the target Namespace with which you can test your policies, but don't change their labels.
Answer:
Check the Pods in the Namespace metadata-access and their labels:
➜ k -n metadata-access get pods --show-labels
NAME ... LABELS
pod1-7d67b4ff9-xrcd7 ... app=pod1,pod-template-hash=7d67b4ff9
pod2-7b6fc66944-2hc7n ... app=pod2,pod-template-hash=7b6fc66944
pod3-7dc879bd59-hkgrr ... app=pod3,role=metadata-accessor,pod-template-hash=7dc879bd59
There are three Pods in the Namespace and one of them has the label role=metadata-accessor.
Check access to the metadata server from the Pods:
➜ k exec -it -n metadata-access pod1-7d67b4ff9-xrcd7 -- curl http://192.168.100.21:32000
metadata server
➜ k exec -it -n metadata-access pod2-7b6fc66944-2hc7n -- curl http://192.168.100.21:32000
metadata server
➜ k exec -it -n metadata-access pod3-7dc879bd59-hkgrr -- curl http://192.168.100.21:32000
metadata server
All three are able to access the metadata server.
To restrict the access, we create a NetworkPolicy to deny access to the specific IP.
# 13_metadata-deny.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: metadata-deny
namespace: metadata-access
spec:
podSelector: {}
policyTypes:
- Egress
egress:
- to:
- ipBlock:
cidr: 0.0.0.0/0
except:
- 192.168.100.21/32
NOTE: You should know about general default-deny K8s NetworkPolcies.
Verify that access to the metadata server has been blocked, but other endpoints are still accessible:
➜ k exec -it -n metadata-access pod1-7d67b4ff9-xrcd7 -- curl http://192.168.100.21:32000
curl: (28) Failed to connect to 192.168.100.21 port 32000: Operation timed out
command terminated with exit code 28
➜ kubectl exec -it -n metadata-access pod1-7d67b4ff9-xrcd7 -- curl -I https://kubernetes.io
HTTP/2 200
cache-control: public, max-age=0, must-revalidate
content-type: text/html; charset=UTF-8
date: Mon, 14 Sep 2020 15:39:39 GMT
etag: "b46e429397e5f1fecf48c10a533f5cd8-ssl"
strict-transport-security: max-age=31536000
age: 13
content-length: 22252
server: Netlify
x-nf-request-id: 1d94a1d1-6bac-4a98-b065-346f661f1db1-393998290
Similarly, verify for the other two Pods.
Now create another NetworkPolicy that allows access to the metadata server from Pods with label role=metadata-accessor.
# 13_metadata-allow.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: metadata-allow
namespace: metadata-access
spec:
podSelector:
matchLabels:
role: metadata-accessor
policyTypes:
- Egress
egress:
- to:
- ipBlock:
cidr: 192.168.100.21/32
Verify that required Pod has access to metadata endpoint and others do not:
➜ k -n metadata-access exec pod3-7dc879bd59-hkgrr -- curl http://192.168.100.21:32000
metadata server
➜ k -n metadata-access exec pod2-7b6fc66944-9ngzr -- curl http://192.168.100.21:32000
^Ccommand terminated with exit code 130
It only works for the Pod having the label. With this we implemented the required security restrictions.
If a Pod doesn't have a matching NetworkPolicy then all traffic is allowed from and to it. Once a Pod has a matching NP then the contained rules are additive. This means that for Pods having label metadata-accessor the rules will be combined to:
# merged policies into one for pods with label metadata-accessor
spec:
podSelector: {}
policyTypes:
- Egress
egress:
- to: # first rule
- ipBlock: # condition 1
cidr: 0.0.0.0/0
except:
- 192.168.100.21/32
- to: # second rule
- ipBlock: # condition 1
cidr: 192.168.100.21/32
We can see that the merged NP contains two separate rules with one condition each. We could read it as:
Allow outgoing traffic if:
(destination is 0.0.0.0/0 but not 192.168.100.21/32) OR (destination is 192.168.100.21/32)
Hence it allows Pods with label metadata-accessor to access everything.
Question 14 | Syscall Activity
Task weight: 4%
Use context: kubectl config use-context workload-prod
There are Pods in Namespace team-yellow. A security investigation noticed that some processes running in these Pods are using the Syscall kill, which is forbidden by a Team Yellow internal policy.
Find the offending Pod(s) and remove these by reducing the replicas of the parent Deployment to 0.
Answer:
Syscalls are used by processes running in Userspace to communicate with the Linux Kernel. There are many available syscalls: https://man7.org/linux/man-pages/man2/syscalls.2.html. It makes sense to restrict these for container processes and Docker/Containerd already restrict some by default, like the reboot Syscall. Restricting even more is possible for example using Seccomp or AppArmor.
But for this task we should simply find out which binary process executes a specific Syscall. Processes in containers are simply run on the same Linux operating system, but isolated. That's why we first check on which nodes the Pods are running:
➜ k -n team-yellow get pod -owide
NAME ... NODE NOMINATED NODE ...
collector1-7585cc58cb-n5rtd 1/1 ... cluster1-node1 <none> ...
collector1-7585cc58cb-vdlp9 1/1 ... cluster1-node1 <none> ...
collector2-8556679d96-z7g7c 1/1 ... cluster1-node1 <none> ...
collector3-8b58fdc88-pjg24 1/1 ... cluster1-node1 <none> ...
collector3-8b58fdc88-s9ltc 1/1 ... cluster1-node1 <none> ...
All on cluster1-node1, hence we ssh into it and find the processes for the first Deployment collector1 .
➜ ssh cluster1-node1
➜ root@cluster1-node1:~# crictl pods --name collector1
POD ID CREATED STATE NAME ...
21aacb8f4ca8d 17 minutes ago Ready collector1-7585cc58cb-vdlp9 ...
186631e40104d 17 minutes ago Ready collector1-7585cc58cb-n5rtd ...
➜ root@cluster1-node1:~# crictl ps --pod 21aacb8f4ca8d
CONTAINER ID IMAGE CREATED ... POD ID
9ea02422f8660 5d867958e04e1 12 minutes ago ... 21aacb8f4ca8d
➜ root@cluster1-node1:~# crictl inspect 9ea02422f8660 | grep args -A1
"args": [
"./collector1-process"
- Using crictl pods we first searched for the Pods of Deployment collector1, which has two replicas
- We then took one pod-id to find it's containers using crictl ps
- And finally we used crictl inspect to find the process name, which is collector1-process
We can find the process PIDs (two because there are two Pods):
➜ root@cluster1-node1:~# ps aux | grep collector1-process
root 35039 0.0 0.1 702208 1044 ? Ssl 13:37 0:00 ./collector1-process
root 35059 0.0 0.1 702208 1044 ? Ssl 13:37 0:00 ./collector1-process
Using the PIDs we can call strace to find Sycalls:
➜ root@cluster1-node1:~# strace -p 35039
strace: Process 35039 attached
futex(0x4d7e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
kill(666, SIGTERM) = -1 ESRCH (No such process)
epoll_pwait(3, [], 128, 999, NULL, 1) = 0
kill(666, SIGTERM) = -1 ESRCH (No such process)
epoll_pwait(3, [], 128, 999, NULL, 1) = 0
kill(666, SIGTERM) = -1 ESRCH (No such process)
epoll_pwait(3, ^Cstrace: Process 35039 detached
<detached ...>
...
First try and already a catch! We see it uses the forbidden Syscall by calling kill(666, SIGTERM).
Next let's check the Deployment collector2 processes:
➜ root@cluster1-node1:~# ps aux | grep collector2-process
root 35375 0.0 0.0 702216 604 ? Ssl 13:37 0:00 ./collector2-process
➜ root@cluster1-node1:~# strace -p 35375
strace: Process 35375 attached
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
...
Looks alright. What about collector3:
➜ root@cluster1-node1:~# ps aux | grep collector3-process
root 35155 0.0 0.1 702472 1040 ? Ssl 13:37 0:00 ./collector3-process
root 35241 0.0 0.1 702472 1044 ? Ssl 13:37 0:00 ./collector3-process
➜ root@cluster1-node1:~# strace -p 35155
strace: Process 35155 attached
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
futex(0x4d9e68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
epoll_pwait(3, [], 128, 999, NULL, 1) = 0
epoll_pwait(3, [], 128, 999, NULL, 1) = 0
...
Also nothing about the forbidden Syscall. So we finalise the task:
And the world is a bit safer again.
Question 15 | Configure TLS on Ingress
Task weight: 4%
Use context: kubectl config use-context workload-prod
In Namespace team-pink there is an existing Nginx Ingress resources named secure which accepts two paths /app and /api which point to different ClusterIP Services.
From your main terminal you can connect to it using for example:
- HTTP:
curl -v http://secure-ingress.test:31080/app - HTTPS:
curl -kv https://secure-ingress.test:31443/app
Right now it uses a default generated TLS certificate by the Nginx Ingress Controller.
You're asked to instead use the key and certificate provided at /opt/course/15/tls.key and /opt/course/15/tls.crt. As it's a self-signed certificate you need to use curl -k when connecting to it.
Answer:
Investigate We can get the IP address of the Ingress and we see it's the same one to which secure-ingress.test is pointing to:
➜ k -n team-pink get ing secure
NAME CLASS HOSTS ADDRESS PORTS AGE
secure <none> secure-ingress.test 192.168.100.12 80 7m11s
➜ ping secure-ingress.test
PING cluster1-node1 (192.168.100.12) 56(84) bytes of data.
64 bytes from cluster1-node1 (192.168.100.12): icmp_seq=1 ttl=64 time=0.316 ms
Now, let's try to access the paths /app and /api via HTTP:
➜ curl http://secure-ingress.test:31080/app
This is the backend APP!
➜ curl http://secure-ingress.test:31080/api
This is the API Server!
What about HTTPS?
➜ curl https://secure-ingress.test:31443/api
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html
curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
➜ curl -k https://secure-ingress.test:31443/api
This is the API Server!
HTTPS seems to be already working if we accept self-signed certificated using -k. But what kind of certificate is used by the server?
➜ curl -kv https://secure-ingress.test:31443/api
...
* Server certificate:
* subject: O=Acme Co; CN=Kubernetes Ingress Controller Fake Certificate
* start date: Sep 28 12:28:35 2020 GMT
* expire date: Sep 28 12:28:35 2021 GMT
* issuer: O=Acme Co; CN=Kubernetes Ingress Controller Fake Certificate
* SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.
...
It seems to be "Kubernetes Ingress Controller Fake Certificate".
Implement own TLS certificate
First, let us generate a Secret using the provided key and certificate:
➜ cd /opt/course/15
➜ :/opt/course/15$ ls
tls.crt tls.key
➜ :/opt/course/15$ k -n team-pink create secret tls tls-secret --key tls.key --cert tls.crt
secret/tls-secret created
Now, we configure the Ingress to make use of this Secret:
# kubectl -n team-pink edit ing secure
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
annotations:
...
generation: 1
name: secure
namespace: team-pink
...
spec:
tls: # add
- hosts: # add
- secure-ingress.test # add
secretName: tls-secret # add
rules:
- host: secure-ingress.test
http:
paths:
- backend:
service:
name: secure-app
port: 80
path: /app
pathType: ImplementationSpecific
- backend:
service:
name: secure-api
port: 80
path: /api
pathType: ImplementationSpecific
...
After adding the changes we check the Ingress resource again:
➜ k -n team-pink get ing
NAME CLASS HOSTS ADDRESS PORTS AGE
secure <none> secure-ingress.test 192.168.100.12 80, 443 25m
It now actually lists port 443 for HTTPS. To verify:
➜ curl -k https://secure-ingress.test:31443/api
This is the API Server!
➜ curl -kv https://secure-ingress.test:31443/api
...
* Server certificate:
* subject: CN=secure-ingress.test; O=secure-ingress.test
* start date: Sep 25 18:22:10 2020 GMT
* expire date: Sep 20 18:22:10 2040 GMT
* issuer: CN=secure-ingress.test; O=secure-ingress.test
* SSL certificate verify result: self signed certificate (18), continuing anyway.
...
We can see that the provided certificate is now being used by the Ingress for TLS termination.
Question 16 | Docker Image Attack Surface
Task weight: 7%
Use context: kubectl config use-context workload-prod
There is a Deployment image-verify in Namespace team-blue which runs image registry.killer.sh:5000/image-verify:v1. DevSecOps has asked you to improve this image by:
- Changing the base image to alpine:3.12
- Not installing curl
- Updating nginx to use the version constraint >=1.18.0
- Running the main process as user myuser
Do not add any new lines to the Dockerfile, just edit existing ones. The file is located at /opt/course/16/image/Dockerfile.
Tag your version as v2. You can build, tag and push using:
cd /opt/course/16/image
podman build -t registry.killer.sh:5000/image-verify:v2 .
podman run registry.killer.sh:5000/image-verify:v2 # to test your changes
podman push registry.killer.sh:5000/image-verify:v2
Make the Deployment use your updated image tag v2.
Answer:
We should have a look at the Docker Image at first:
# /opt/course/16/image/Dockerfile
FROM alpine:3.4
RUN apk update && apk add vim curl nginx=1.10.3-r0
RUN addgroup -S myuser && adduser -S myuser -G myuser
COPY ./run.sh run.sh
RUN ["chmod", "+x", "./run.sh"]
USER root
ENTRYPOINT ["/bin/sh", "./run.sh"]
Very simple Dockerfile which seems to execute a script run.sh :
So it only outputs current date and credential information in a loop. We can see that output in the existing Deployment image-verify:
➜ k -n team-blue logs -f -l id=image-verify
Fri Sep 25 20:59:12 UTC 2020
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)
We see its running as root.
Next we update the Dockerfile according to the requirements:
# /opt/course/16/image/Dockerfile
# change
FROM alpine:3.12
# change
RUN apk update && apk add vim nginx>=1.18.0
RUN addgroup -S myuser && adduser -S myuser -G myuser
COPY ./run.sh run.sh
RUN ["chmod", "+x", "./run.sh"]
# change
USER myuser
ENTRYPOINT ["/bin/sh", "./run.sh"]
Then we build the new image:
➜ :/opt/course/16/image$ podman build -t registry.killer.sh:5000/image-verify:v2 .
...
STEP 7/7: ENTRYPOINT ["/bin/sh", "./run.sh"]
COMMIT registry.killer.sh:5000/image-verify:v2
--> ceb8989101b
Successfully tagged registry.killer.sh:5000/image-verify:v2
ceb8989101bccd9f6b9c3b4c6c75f6c3561f19a5b784edd1f1a36fa0fb34a9df
We can then test our changes by running the container locally:
➜ :/opt/course/16/image$ podman run registry.killer.sh:5000/image-verify:v2
Thu Sep 16 06:01:47 UTC 2021
uid=101(myuser) gid=102(myuser) groups=102(myuser)
Thu Sep 16 06:01:48 UTC 2021
uid=101(myuser) gid=102(myuser) groups=102(myuser)
Thu Sep 16 06:01:49 UTC 2021
uid=101(myuser) gid=102(myuser) groups=102(myuser)
Looking good, so we push:
➜ :/opt/course/16/image$ podman push registry.killer.sh:5000/image-verify:v2
Getting image source signatures
Copying blob cd0853834d88 done
Copying blob 5298d0709c3e skipped: already exists
Copying blob e6688e911f15 done
Copying blob dbc406096645 skipped: already exists
Copying blob 98895ed393d9 done
Copying config ceb8989101 done
Writing manifest to image destination
Storing signatures
And we update the Deployment to use the new image:
# kubectl -n team-blue edit deploy image-verify
apiVersion: apps/v1
kind: Deployment
metadata:
...
spec:
...
template:
...
spec:
containers:
- image: registry.killer.sh:5000/image-verify:v2 # change
And afterwards we can verify our changes by looking at the Pod logs:
➜ k -n team-blue logs -f -l id=image-verify
Fri Sep 25 21:06:55 UTC 2020
uid=101(myuser) gid=102(myuser) groups=102(myuser)
Also to verify our changes even further:
➜ k -n team-blue exec image-verify-55fbcd4c9b-x2flc -- curl
OCI runtime exec failed: exec failed: container_linux.go:349: starting container process caused "exec: \"curl\": executable file not found in $PATH": unknown
command terminated with exit code 126
➜ k -n team-blue exec image-verify-55fbcd4c9b-x2flc -- nginx -v
nginx version: nginx/1.18.0
Another task solved.
Question 17 | Audit Log Policy
Task weight: 7%
Use context: kubectl config use-context infra-prod
Audit Logging has been enabled in the cluster with an Audit Policy located at /etc/kubernetes/audit/policy.yaml on cluster2-controlplane1.
Change the configuration so that only one backup of the logs is stored.
Alter the Policy in a way that it only stores logs:
- From Secret resources, level Metadata
- From "system:nodes" userGroups, level RequestResponse
After you altered the Policy make sure to empty the log file so it only contains entries according to your changes, like using truncate -s 0 /etc/kubernetes/audit/logs/audit.log.
NOTE: You can use jq to render json more readable. cat data.json | jq
Answer:
First we check the apiserver configuration and change as requested:
➜ ssh cluster2-controlplane1
➜ root@cluster2-controlplane1:~# cp /etc/kubernetes/manifests/kube-apiserver.yaml ~/17_kube-apiserver.yaml # backup
➜ root@cluster2-controlplane1:~# vim /etc/kubernetes/manifests/kube-apiserver.yaml
# /etc/kubernetes/manifests/kube-apiserver.yaml
apiVersion: v1
kind: Pod
metadata:
annotations:
kubeadm.kubernetes.io/kube-apiserver.advertise-address.endpoint: 192.168.100.21:6443
creationTimestamp: null
labels:
component: kube-apiserver
tier: control-plane
name: kube-apiserver
namespace: kube-system
spec:
containers:
- command:
- kube-apiserver
- --audit-policy-file=/etc/kubernetes/audit/policy.yaml
- --audit-log-path=/etc/kubernetes/audit/logs/audit.log
- --audit-log-maxsize=5
- --audit-log-maxbackup=1 # CHANGE
- --advertise-address=192.168.100.21
- --allow-privileged=true
...
NOTE: You should know how to enable Audit Logging completely yourself as described in the docs. Feel free to try this in another cluster in this environment.
Now we look at the existing Policy:
# /etc/kubernetes/audit/policy.yaml
apiVersion: audit.k8s.io/v1
kind: Policy
rules:
- level: Metadata
We can see that this simple Policy logs everything on Metadata level. So we change it to the requirements:
# /etc/kubernetes/audit/policy.yaml
apiVersion: audit.k8s.io/v1
kind: Policy
rules:
# log Secret resources audits, level Metadata
- level: Metadata
resources:
- group: ""
resources: ["secrets"]
# log node related audits, level RequestResponse
- level: RequestResponse
userGroups: ["system:nodes"]
# for everything else don't log anything
- level: None
After saving the changes we have to restart the apiserver:
➜ root@cluster2-controlplane1:~# cd /etc/kubernetes/manifests/
➜ root@cluster2-controlplane1:/etc/kubernetes/manifests# mv kube-apiserver.yaml ..
➜ root@cluster2-controlplane1:/etc/kubernetes/manifests# watch crictl ps # wait for apiserver gone
➜ root@cluster2-controlplane1:/etc/kubernetes/manifests# truncate -s 0 /etc/kubernetes/audit/logs/audit.log
➜ root@cluster2-controlplane1:/etc/kubernetes/manifests# mv ../kube-apiserver.yaml .
Once the apiserver is running again we can check the new logs and scroll through some entries:
{
"kind": "Event",
"apiVersion": "audit.k8s.io/v1",
"level": "Metadata",
"auditID": "e598dc9e-fc8b-4213-aee3-0719499ab1bd",
"stage": "RequestReceived",
"requestURI": "...",
"verb": "watch",
"user": {
"username": "system:serviceaccount:gatekeeper-system:gatekeeper-admin",
"uid": "79870838-75a8-479b-ad42-4b7b75bd17a3",
"groups": [
"system:serviceaccounts",
"system:serviceaccounts:gatekeeper-system",
"system:authenticated"
]
},
"sourceIPs": [
"192.168.102.21"
],
"userAgent": "manager/v0.0.0 (linux/amd64) kubernetes/$Format",
"objectRef": {
"resource": "secrets",
"apiVersion": "v1"
},
"requestReceivedTimestamp": "2020-09-27T20:01:36.238911Z",
"stageTimestamp": "2020-09-27T20:01:36.238911Z",
"annotations": {
"authentication.k8s.io/legacy-token": "..."
}
}
Above we logged a watch action by OPA Gatekeeper for Secrets, level Metadata.
{
"kind": "Event",
"apiVersion": "audit.k8s.io/v1",
"level": "RequestResponse",
"auditID": "c90e53ed-b0cf-4cc4-889a-f1204dd39267",
"stage": "ResponseComplete",
"requestURI": "...",
"verb": "list",
"user": {
"username": "system:node:cluster2-controlplane1",
"groups": [
"system:nodes",
"system:authenticated"
]
},
"sourceIPs": [
"192.168.100.21"
],
"userAgent": "kubelet/v1.19.1 (linux/amd64) kubernetes/206bcad",
"objectRef": {
"resource": "configmaps",
"namespace": "kube-system",
"name": "kube-proxy",
"apiVersion": "v1"
},
"responseStatus": {
"metadata": {},
"code": 200
},
"responseObject": {
"kind": "ConfigMapList",
"apiVersion": "v1",
"metadata": {
"selfLink": "/api/v1/namespaces/kube-system/configmaps",
"resourceVersion": "83409"
},
"items": [
{
"metadata": {
"name": "kube-proxy",
"namespace": "kube-system",
"selfLink": "/api/v1/namespaces/kube-system/configmaps/kube-proxy",
"uid": "0f1c3950-430a-4543-83e4-3f9c87a478b8",
"resourceVersion": "232",
"creationTimestamp": "2020-09-26T20:59:50Z",
"labels": {
"app": "kube-proxy"
},
"annotations": {
"kubeadm.kubernetes.io/component-config.hash": "..."
},
"managedFields": [
{
...
}
]
},
...
}
]
},
"requestReceivedTimestamp": "2020-09-27T20:01:36.223781Z",
"stageTimestamp": "2020-09-27T20:01:36.225470Z",
"annotations": {
"authorization.k8s.io/decision": "allow",
"authorization.k8s.io/reason": ""
}
}
And in the one above we logged a list action by system:nodes for a ConfigMaps, level RequestResponse.
Because all JSON entries are written in a single line in the file we could also run some simple verifications on our Policy:
# shows Secret entries
cat audit.log | grep '"resource":"secrets"' | wc -l
# confirms Secret entries are only of level Metadata
cat audit.log | grep '"resource":"secrets"' | grep -v '"level":"Metadata"' | wc -l
# shows RequestResponse level entries
cat audit.log | grep -v '"level":"RequestResponse"' | wc -l
# shows RequestResponse level entries are only for system:nodes
cat audit.log | grep '"level":"RequestResponse"' | grep -v "system:nodes" | wc -l
Looks like our job is done.
Question 18 | Investigate Break-in via Audit Log
Task weight: 4%
Use context: kubectl config use-context infra-prod
Namespace security contains five Secrets of type Opaque which can be considered highly confidential. The latest Incident-Prevention-Investigation revealed that ServiceAccount p.auster had too broad access to the cluster for some time. This SA should've never had access to any Secrets in that Namespace.
Find out which Secrets in Namespace security this SA did access by looking at the Audit Logs under /opt/course/18/audit.log.
Change the password to any new string of only those Secrets that were accessed by this SA.
NOTE: You can use jq to render json more readable. cat data.json | jq
Answer: First we look at the Secrets this is about:
➜ k -n security get secret | grep Opaque kubeadmin-token Opaque 1 37m mysql-admin Opaque 1 37m postgres001 Opaque 1 37m postgres002 Opaque 1 37m vault-token Opaque 1 37m Next we investigate the Audit Log file:
➜ cd /opt/course/18
➜ :/opt/course/18$ ls -lh total 7.1M -rw-r--r-- 1 k8s k8s 7.5M Sep 24 21:31 audit.log
➜ :/opt/course/18$ cat audit.log | wc -l 4451 Audit Logs can be huge and it's common to limit the amount by creating an Audit Policy and to transfer the data in systems like Elasticsearch. In this case we have a simple JSON export, but it already contains 4451 lines.
We should try to filter the file down to relevant information:
➜ :/opt/course/18$ cat audit.log | grep "p.auster" | wc -l 28 Not too bad, only 28 logs for ServiceAccount p.auster.
➜ :/opt/course/18$ cat audit.log | grep "p.auster" | grep Secret | wc -l 2 And only 2 logs related to Secrets...
➜ :/opt/course/18$ cat audit.log | grep "p.auster" | grep Secret | grep list | wc -l 0
➜ :/opt/course/18$ cat audit.log | grep "p.auster" | grep Secret | grep get | wc -l 2 No list actions, which is good, but 2 get actions, so we check these out:
cat audit.log | grep "p.auster" | grep Secret | grep get | jq { "kind": "Event", "apiVersion": "audit.k8s.io/v1", "level": "RequestResponse", "auditID": "74fd9e03-abea-4df1-b3d0-9cfeff9ad97a", "stage": "ResponseComplete", "requestURI": "/api/v1/namespaces/security/secrets/vault-token", "verb": "get", "user": { "username": "system:serviceaccount:security:p.auster", "uid": "29ecb107-c0e8-4f2d-816a-b16f4391999c", "groups": [ "system:serviceaccounts", "system:serviceaccounts:security", "system:authenticated" ] }, ... "userAgent": "curl/7.64.0", "objectRef": { "resource": "secrets", "namespace": "security", "name": "vault-token", "apiVersion": "v1" }, ... } { "kind": "Event", "apiVersion": "audit.k8s.io/v1", "level": "RequestResponse", "auditID": "aed6caf9-5af0-4872-8f09-ad55974bb5e0", "stage": "ResponseComplete", "requestURI": "/api/v1/namespaces/security/secrets/mysql-admin", "verb": "get", "user": { "username": "system:serviceaccount:security:p.auster", "uid": "29ecb107-c0e8-4f2d-816a-b16f4391999c", "groups": [ "system:serviceaccounts", "system:serviceaccounts:security", "system:authenticated" ] }, ... "userAgent": "curl/7.64.0", "objectRef": { "resource": "secrets", "namespace": "security", "name": "mysql-admin", "apiVersion": "v1" }, ... } There we see that Secrets vault-token and mysql-admin were accessed by p.auster. Hence we change the passwords for those.
➜ echo new-vault-pass | base64 bmV3LXZhdWx0LXBhc3MK
➜ k -n security edit secret vault-token
➜ echo new-mysql-pass | base64 bmV3LW15c3FsLXBhc3MK
➜ k -n security edit secret mysql-admin Audit Logs ftw.
By running cat audit.log | grep "p.auster" | grep Secret | grep password we can see that passwords are stored in the Audit Logs, because they store the complete content of Secrets. It's never a good idea to reveal passwords in logs. In this case it would probably be sufficient to only store Metadata level information of Secrets which can be controlled via a Audit Policy.
Question 19 | Immutable Root FileSystem
Task weight: 2%
Use context: kubectl config use-context workload-prod
The Deployment immutable-deployment in Namespace team-purple should run immutable, it's created from file /opt/course/19/immutable-deployment.yaml. Even after a successful break-in, it shouldn't be possible for an attacker to modify the filesystem of the running container.
Modify the Deployment in a way that no processes inside the container can modify the local filesystem, only /tmp directory should be writeable. Don't modify the Docker image.
Save the updated YAML under /opt/course/19/immutable-deployment-new.yaml and update the running Deployment.
Answer:
Processes in containers can write to the local filesystem by default. This increases the attack surface when a non-malicious process gets hijacked. Preventing applications to write to disk or only allowing to certain directories can mitigate the risk. If there is for example a bug in Nginx which allows an attacker to override any file inside the container, then this only works if the Nginx process itself can write to the filesystem in the first place.
Making the root filesystem readonly can be done in the Docker image itself or in a Pod declaration.
Let us first check the Deployment immutable-deployment in Namespace team-purple:
# kubectl -n team-purple edit deploy -o yaml
apiVersion: apps/v1
kind: Deployment
metadata:
namespace: team-purple
name: immutable-deployment
labels:
app: immutable-deployment
...
spec:
replicas: 1
selector:
matchLabels:
app: immutable-deployment
template:
metadata:
labels:
app: immutable-deployment
spec:
containers:
- image: busybox:1.32.0
command: ['sh', '-c', 'tail -f /dev/null']
imagePullPolicy: IfNotPresent
name: busybox
restartPolicy: Always
...
The container has write access to the Root File System, as there are no restrictions defined for the Pods or containers by an existing SecurityContext. And based on the task we're not allowed to alter the Docker image.
So we modify the YAML manifest to include the required changes:
cp /opt/course/19/immutable-deployment.yaml /opt/course/19/immutable-deployment-new.yaml
vim /opt/course/19/immutable-deployment-new.yaml
# /opt/course/19/immutable-deployment-new.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
namespace: team-purple
name: immutable-deployment
labels:
app: immutable-deployment
spec:
replicas: 1
selector:
matchLabels:
app: immutable-deployment
template:
metadata:
labels:
app: immutable-deployment
spec:
containers:
- image: busybox:1.32.0
command: ['sh', '-c', 'tail -f /dev/null']
imagePullPolicy: IfNotPresent
name: busybox
securityContext: # add
readOnlyRootFilesystem: true # add
volumeMounts: # add
- mountPath: /tmp # add
name: temp-vol # add
volumes: # add
- name: temp-vol # add
emptyDir: {} # add
restartPolicy: Always
SecurityContexts can be set on Pod or container level, here the latter was asked. Enforcing readOnlyRootFilesystem: true will render the root filesystem readonly. We can then allow some directories to be writable by using an emptyDir volume.
Once the changes are made, let us update the Deployment:
➜ k delete -f /opt/course/19/immutable-deployment-new.yaml
deployment.apps "immutable-deployment" deleted
➜ k create -f /opt/course/19/immutable-deployment-new.yaml
deployment.apps/immutable-deployment created
We can verify if the required changes are propagated:
➜ k -n team-purple exec immutable-deployment-5b7ff8d464-j2nrj -- touch /abc.txt
touch: /abc.txt: Read-only file system
command terminated with exit code 1
➜ k -n team-purple exec immutable-deployment-5b7ff8d464-j2nrj -- touch /var/abc.txt
touch: /var/abc.txt: Read-only file system
command terminated with exit code 1
➜ k -n team-purple exec immutable-deployment-5b7ff8d464-j2nrj -- touch /etc/abc.txt
touch: /etc/abc.txt: Read-only file system
command terminated with exit code 1
➜ k -n team-purple exec immutable-deployment-5b7ff8d464-j2nrj -- touch /tmp/abc.txt
➜ k -n team-purple exec immutable-deployment-5b7ff8d464-j2nrj -- ls /tmp
abc.txt
The Deployment has been updated so that the container's file system is read-only, and the updated YAML has been placed under the required location. Sweet!
Question 20 | Update Kubernetes
Task weight: 8%
Use context: kubectl config use-context workload-stage
The cluster is running Kubernetes 1.24.7, update it to 1.25.2.
Use apt package manager and kubeadm for this.
Use ssh cluster3-controlplane1 and ssh cluster3-node1 to connect to the instances.
Answer:
Let's have a look at the current versions:
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-controlplane1 Ready control-plane 21d v1.24.7
cluster3-node1 Ready <none> 21d v1.24.7
Control Plane Master Components
First we should update the control plane components running on the master node, so we drain it:
➜ k drain cluster3-controlplane1 --ignore-daemonsets
Next we ssh into it and check versions:
➜ ssh cluster3-controlplane1
➜ root@cluster3-controlplane1:~# kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"24", GitVersion:"v1.24.1", GitCommit:"3ddd0f45aa91e2f30c70734b175631bec5b5825a", GitTreeState:"clean", BuildDate:"2022-05-24T12:24:38Z", GoVersion:"go1.18.2", Compiler:"gc", Platform:"linux/amd64"}
➜ root@cluster3-controlplane1:~# kubelet --version
Kubernetes v1.23.1
We see kubeadm is already installed in the required version. Else we would need to install it:
# not necessary because here kubeadm is already installed in correct version
apt-mark unhold kubeadm
apt-mark hold kubectl kubelet
apt install kubeadm=1.24.1-00
apt-mark hold kubeadm
Check what kubeadm has available as an upgrade plan:
➜ root@cluster3-controlplane1:~# kubeadm upgrade plan
...
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
W0804 11:13:33.017862 32724 initconfiguration.go:120] Usage of CRI endpoints without URL scheme is deprecated and can cause kubelet errors in the future. Automatically prepending scheme "unix" to the "criSocket" with value "/run/containerd/containerd.sock". Please update your configuration!
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.23.1
[upgrade/versions] kubeadm version: v1.24.1
[upgrade/versions] Target version: v1.24.3
[upgrade/versions] Latest version in the v1.23 series: v1.23.9
...
You can now apply the upgrade by executing the following command:
kubeadm upgrade apply v1.24.3
Note: Before you can perform this upgrade, you have to update kubeadm to v1.24.3.
...
And we apply to the required version:
➜ root@cluster3-controlplane1:~# kubeadm upgrade apply v1.24.1
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
W0804 11:15:35.345360 32762 initconfiguration.go:120] Usage of CRI endpoints without URL scheme is deprecated and can cause kubelet errors in the future. Automatically prepending scheme "unix" to the "criSocket" with value "/run/containerd/containerd.sock". Please update your configuration!
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade/version] You have chosen to change the cluster version to "v1.24.1"
[upgrade/versions] Cluster version: v1.23.1
[upgrade/versions] kubeadm version: v1.24.1
[upgrade/confirm] Are you sure you want to proceed with the upgrade? [y/N]: y
[upgrade/prepull] Pulling images required for setting up a Kubernetes cluster
....
[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.24.1". Enjoy!
Next we can check if our required version was installed correctly:
➜ root@cluster3-controlplane1:~# kubeadm upgrade plan
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.24.1
[upgrade/versions] kubeadm version: v1.24.1
[upgrade/versions] Target version: v1.24.3
[upgrade/versions] Latest version in the v1.24 series: v1.24.3
...
Control Plane kubelet and kubectl
➜ root@cluster3-controlplane1:~# apt update
Hit:1 http://ppa.launchpad.net/rmescandon/yq/ubuntu focal InRelease
Hit:3 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 https://packages.cloud.google.com/apt kubernetes-xenial InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
➜ root@cluster3-controlplane1:~# apt-mark unhold kubelet kubectl
kubelet was already not hold.
kubectl was already not hold.
➜ root@cluster3-controlplane1:~# apt install kubelet=1.24.1-00 kubectl=1.24.1-00
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
kubectl kubelet
2 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
Need to get 28.6 MB of archives.
After this operation, 9,044 kB disk space will be freed.
Get:1 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubectl amd64 1.24.1-00 [9,318 kB]
Get:2 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubelet amd64 1.24.1-00 [19.3 MB]
Fetched 28.6 MB in 2s (12.8 MB/s)
(Reading database ... 112511 files and directories currently installed.)
Preparing to unpack .../kubectl_1.24.1-00_amd64.deb ...
Unpacking kubectl (1.24.1-00) over (1.23.1-00) ...
Preparing to unpack .../kubelet_1.24.1-00_amd64.deb ...
Unpacking kubelet (1.24.1-00) over (1.23.1-00) ...
Setting up kubectl (1.24.1-00) ...
Setting up kubelet (1.24.1-00) ...
➜ root@cluster3-controlplane1:~# apt-mark hold kubelet kubectl
kubelet set on hold.
kubectl set on hold.
➜ root@cluster3-controlplane1:~# service kubelet restart
➜ root@cluster3-controlplane1:~# service kubelet status
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since Sun 2022-02-06 15:32:36 UTC; 8s ago
➜ root@cluster3-controlplane1:~# kubectl get node
NAME STATUS ROLES AGE VERSION
cluster3-controlplane1 Ready,SchedulingDisabled control-plane 21d v1.24.1
cluster3-node1 Ready <none> 21d v1.23.1
Done, and uncordon:
Data Plane
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-controlplane1 Ready control-plane 21d v1.24.1
cluster3-node1 Ready <none> 21d v1.23.1
Our data plane consist of one single worker node, so let's update it. First thing is we should drain it:
Next we ssh into it and upgrade kubeadm to the wanted version, or check if already done:
➜ ssh cluster3-node1
➜ root@cluster3-node1:~# apt update
Hit:1 http://ppa.launchpad.net/rmescandon/yq/ubuntu focal InRelease
Hit:3 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Hit:2 https://packages.cloud.google.com/apt kubernetes-xenial InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
➜ root@cluster3-node1:~# apt-mark unhold kubeadm
kubeadm was already not hold.
➜ root@cluster3-node1:~# apt-mark hold kubectl kubelet
kubectl set on hold.
kubelet set on hold.
➜ root@cluster3-node1:~# apt install kubeadm=1.24.1-00
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
kubeadm
1 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
Need to get 9,000 kB of archives.
After this operation, 844 kB disk space will be freed.
Get:1 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubeadm amd64 1.24.1-00 [9,000 kB]
Fetched 9,000 kB in 1s (6,250 kB/s)
(Reading database ... 112511 files and directories currently installed.)
Preparing to unpack .../kubeadm_1.24.1-00_amd64.deb ...
Unpacking kubeadm (1.24.1-00) over (1.23.1-00) ...
Setting up kubeadm (1.24.1-00) ...
➜ root@cluster3-node1:~# apt-mark hold kubeadm
kubeadm set on hold.
➜ root@cluster3-node1:~# kubeadm upgrade node
[upgrade] Reading configuration from the cluster...
[upgrade] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[preflight] Running pre-flight checks
[preflight] Skipping prepull. Not a control plane node.
[upgrade] Skipping phase. Not a control plane node.
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[upgrade] The configuration for this node was successfully updated!
[upgrade] Now you should go ahead and upgrade the kubelet package using your package manager.
Now we follow that kubeadm told us in the last line and upgrade kubelet (and kubectl):
➜ root@cluster3-node1:~# apt-mark unhold kubectl kubelet
Canceled hold on kubectl.
Canceled hold on kubelet.
➜ root@cluster3-node1:~# apt install kubelet=1.24.1-00 kubectl=1.24.1-00
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
kubectl kubelet
2 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
Need to get 28.6 MB of archives.
After this operation, 9,044 kB disk space will be freed.
Get:1 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubectl amd64 1.24.1-00 [9,318 kB]
Get:2 https://packages.cloud.google.com/apt kubernetes-xenial/main amd64 kubelet amd64 1.24.1-00 [19.3 MB]
Fetched 28.6 MB in 1s (24.0 MB/s)
(Reading database ... 112511 files and directories currently installed.)
Preparing to unpack .../kubectl_1.24.1-00_amd64.deb ...
Unpacking kubectl (1.24.1-00) over (1.23.1-00) ...
Preparing to unpack .../kubelet_1.24.1-00_amd64.deb ...
Unpacking kubelet (1.24.1-00) over (1.23.1-00) ...
Setting up kubectl (1.24.1-00) ...
Setting up kubelet (1.24.1-00) ...
➜ root@cluster3-node1:~# service kubelet restart
➜ root@cluster3-node1:~# service kubelet status
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since Sun 2022-02-06 15:38:10 UTC; 3s ago
Looking good, what does the node status say?
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-controlplane1 Ready control-plane 21d v1.24.1
cluster3-node1 Ready,SchedulingDisabled <none> 21d v1.24.1
Beautiful, let's make it schedulable again:
➜ k uncordon cluster3-node1
node/cluster3-node1 uncordoned
➜ k get node
NAME STATUS ROLES AGE VERSION
cluster3-controlplane1 Ready control-plane 21d v1.24.1
cluster3-node1 Ready <none> 21d v1.24.1
We're up to date.
Question 21 | Image Vulnerability Scanning
Task weight: 2%
(can be solved in any kubectl context)
The Vulnerability Scanner trivy is installed on your main terminal. Use it to scan the following images for known CVEs:
- nginx:1.16.1-alpine
- k8s.gcr.io/kube-apiserver:v1.18.0
- k8s.gcr.io/kube-controller-manager:v1.18.0
- docker.io/weaveworks/weave-kube:2.7.0
Write all images that don't contain the vulnerabilities CVE-2020-10878 or CVE-2020-1967 into /opt/course/21/good-images.
Answer:
The tool trivy is very simple to use, it compares images against public databases.
➜ trivy nginx:1.16.1-alpine
2020-10-09T20:59:39.198Z INFO Need to update DB
2020-10-09T20:59:39.198Z INFO Downloading DB...
18.81 MiB / 18.81 MiB [-------------------------------------
2020-10-09T20:59:45.499Z INFO Detecting Alpine vulnerabilities...
nginx:1.16.1-alpine (alpine 3.10.4)
===================================
Total: 7 (UNKNOWN: 0, LOW: 0, MEDIUM: 7, HIGH: 0, CRITICAL: 0)
+---------------+------------------+----------+-------------------
| LIBRARY | VULNERABILITY ID | SEVERITY | INSTALLED VERSION
+---------------+------------------+----------+-------------------
| libcrypto1.1 | CVE-2020-1967 | MEDIUM | 1.1.1d-r2
...
To solve the task we can run:
➜ trivy nginx:1.16.1-alpine | grep -E 'CVE-2020-10878|CVE-2020-1967'
| libcrypto1.1 | CVE-2020-1967 | MEDIUM
| libssl1.1 | CVE-2020-1967 |
➜ trivy k8s.gcr.io/kube-apiserver:v1.18.0 | grep -E 'CVE-2020-10878|CVE-2020-1967'
| perl-base | CVE-2020-10878 | HIGH
➜ trivy k8s.gcr.io/kube-controller-manager:v1.18.0 | grep -E 'CVE-2020-10878|CVE-2020-1967'
| perl-base | CVE-2020-10878 | HIGH
➜ trivy docker.io/weaveworks/weave-kube:2.7.0 | grep -E 'CVE-2020-10878|CVE-2020-1967'
➜
The only image without the any of the two CVEs is docker.io/weaveworks/weave-kube:2.7.0, hence our answer will be:
Question 22 | Manual Static Security Analysis
Task weight: 3%
(can be solved in any kubectl context)
The Release Engineering Team has shared some YAML manifests and Dockerfiles with you to review. The files are located under /opt/course/22/files.
As a container security expert, you are asked to perform a manual static analysis and find out possible security issues with respect to unwanted credential exposure. Running processes as root is of no concern in this task.
Write the filenames which have issues into /opt/course/22/security-issues.
NOTE: In the Dockerfile and YAML manifests, assume that the referred files, folders, secrets and volume mounts are present. Disregard syntax or logic errors.
Answer:
We check location /opt/course/22/files and list the files.
➜ ls -la /opt/course/22/files
total 48
drwxr-xr-x 2 k8s k8s 4096 Sep 16 19:08 .
drwxr-xr-x 3 k8s k8s 4096 Sep 16 19:08 ..
-rw-r--r-- 1 k8s k8s 692 Sep 16 19:08 Dockerfile-go
-rw-r--r-- 1 k8s k8s 897 Sep 16 19:08 Dockerfile-mysql
-rw-r--r-- 1 k8s k8s 743 Sep 16 19:08 Dockerfile-py
-rw-r--r-- 1 k8s k8s 341 Sep 16 19:08 deployment-nginx.yaml
-rw-r--r-- 1 k8s k8s 705 Sep 16 19:08 deployment-redis.yaml
-rw-r--r-- 1 k8s k8s 392 Sep 16 19:08 pod-nginx.yaml
-rw-r--r-- 1 k8s k8s 228 Sep 16 19:08 pv-manual.yaml
-rw-r--r-- 1 k8s k8s 188 Sep 16 19:08 pvc-manual.yaml
-rw-r--r-- 1 k8s k8s 211 Sep 16 19:08 sc-local.yaml
-rw-r--r-- 1 k8s k8s 902 Sep 16 19:08 statefulset-nginx.yaml
We have 3 Dockerfiles and 7 Kubernetes Resource YAML manifests. Next we should go over each to find security issues with the way credentials have been used.
NOTE: You should be comfortable with Docker Best Practices and the Kubernetes Configuration Best Practices.
While navigating through the files we might notice:
Number 1
File Dockerfile-mysql might look innocent on first look. It copies a file secret-token over, uses it and deletes it afterwards. But because of the way Docker works, every RUN, COPY and ADD command creates a new layer and every layer is persistet in the image.
This means even if the file secret-token get's deleted in layer Z, it's still included with the image in layer X and Y. In this case it would be better to use for example variables passed to Docker.
# /opt/course/22/files/Dockerfile-mysql
FROM ubuntu
# Add MySQL configuration
COPY my.cnf /etc/mysql/conf.d/my.cnf
COPY mysqld_charset.cnf /etc/mysql/conf.d/mysqld_charset.cnf
RUN apt-get update && \
apt-get -yq install mysql-server-5.6 &&
# Add MySQL scripts
COPY import_sql.sh /import_sql.sh
COPY run.sh /run.sh
# Configure credentials
COPY secret-token . # LAYER X
RUN /etc/register.sh ./secret-token # LAYER Y
RUN rm ./secret-token # delete secret token again # LATER Z
EXPOSE 3306
CMD ["/run.sh"]
So we do:
Number 2
The file deployment-redis.yaml is fetching credentials from a Secret named mysecret and writes these into environment variables. So far so good, but in the command of the container it's echoing these which can be directly read by any user having access to the logs.
# /opt/course/22/files/deployment-redis.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: mycontainer
image: redis
command: ["/bin/sh"]
args:
- "-c"
- "echo $SECRET_USERNAME && echo $SECRET_PASSWORD && docker-entrypoint.sh" # NOT GOOD
env:
- name: SECRET_USERNAME
valueFrom:
secretKeyRef:
name: mysecret
key: username
- name: SECRET_PASSWORD
valueFrom:
secretKeyRef:
name: mysecret
key: password
Credentials in logs is never a good idea, hence we do:
Number 3
In file statefulset-nginx.yaml, the password is directly exposed in the environment variable definition of the container.
# /opt/course/22/files/statefulset-nginx.yaml
...
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: web
spec:
serviceName: "nginx"
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: k8s.gcr.io/nginx-slim:0.8
env:
- name: Username
value: Administrator
- name: Password
value: MyDiReCtP@sSw0rd # NOT GOOD
ports:
- containerPort: 80
name: web
..
This should better be injected via a Secret. So we do: