Wednesday, February 19, 2020

Listing AWS Public EBS Snapshots

Create Volume Permissions

The create volume permissions fall into the following categories:

       o public : The owner of the snapshot granted create volume  permissions
         for  the snapshot to the all group. All AWS accounts have create vol-
         ume permissions for these snapshots.

       o explicit : The owner of the snapshot granted  create  volume  permis-
         sions to a specific AWS account.

       o implicit  : An AWS account has implicit create volume permissions for
         all snapshots it owns.


 o owner-alias  - Value from an Amazon-maintained list (amazon | self
            | all | aws-marketplace | microsoft ) of snapshot owners.  Not  to
            be  confused  with the user-configured AWS account alias, which is
            set from the IAM console.

Run aws ec2 describe-snapshots help to get the help for command in scope.

Below command lists public EBS snapshots
praveend$ aws ec2 describe-snapshots --profile pd-dev --region us-east-1 --output table --filters Name=owner-alias,Values=all

Sunday, September 15, 2019

Testing/Writing Chef Cookbooks

Writing cookbooks

Cookbooks has attributes, recipes, templates etc

Using Community cookbooks
  1. Modify Berksfile in the cookbook by adding cookbook name, say, cookbook 'yum-centos', '~> 3.0.0'
  2. Modify metadata.rb in cookbook by updating dependencies, say, depends 'yum-centos', '~> 3.0.0'
  3. Execute below commands
$ berks install
$ berks upload

Make sure we have below configs/files
  • Chef cookbook
  • Chef Environment
  • Chef Role
Testing cookbook locally

  1. Install vagrant from
  2. Install Virtualbox
  3. Modify .kitchen.yml file referring to community cookbook recipe to test locally.
  4. Goto cookbook directory and execute kitchen commands to build, list, login to new created resource from chef cookbooks.
$ kitchen converge
$ kitchen list
$ kitchen login
Update authentication key
# Connect to chef server 
[pd@ip-disects ~]$ ssh -A -t SSH_SERVER_IP 

# Following commands are executed on chef server 
[pd@ip-disects ~]$ sudo chef-server-ctl user-create praveend Praveen Darshanam Myp@ssw0rd -f /tmp/praveend.key 
ERROR: Conflict 
Response: Username or email address already in use. 

[pd@ip-disects ~]$ sudo chef-server-ctl user-delete praveend 
Do you want to delete the user praveend? (Y/N) y 
Checking organization memberships... 
Checking admin group memberships for 1 org(s). 
FATAL: praveend is in the 'admins' group of the following organization(s): 
- disects

Run this command again with the --remove-from-admin-groups option to remove the user from these admin group(s) automatically. 
[pd@ip-disects ~]$ sudo chef-server-ctl user-delete praveend --remove-from-admin-groups 
Do you want to delete the user praveend? (Y/N) y 
Checking organization memberships... 
Checking admin group memberships for 1 org(s). 
Removing praveend from admins group of 'disects' 
Deleting user praveend. 

[pd@ip-disects ~]$ sudo chef-server-ctl user-create praveend Praveen Darshanam Myp@ssw0rd -f /tmp/praveend.key 
[pd@ip-disects ~]$ sudo chef-server-ctl org-user-add disects praveend --admin 
User praveend is added to admins and billing-admins group

Upload working cookbook to chef server after local testing. Test the cookbook on a cluster node to make sure everything is working fine, this needs some experience though.
$ knife cookbook upload cookbook_name

Kubernetes ingress custom Certificates with valid CA

Irrespective of ingress FQDN, Kubernetes creates Certificates with domain name ingress.local which creates below issues.
CoreOS Dex need certificates from valid CA, self-signed certificates will now work
Gardener dashboard authentication has issues with self-signed certificates. AuthN flow will not happen without accepting invalid Cert error
Accessing ingress in any browser will complain self-signed server error

Fix: Lets encrypt

Install Certbot from LetsEncrypt
$ brew install certbot

Create wildcard Certificate for domain, * 

Before entering Yes to confirm, make sure you add TXT record entry as prompted by certbot.
# create directories named le_wd, le_cd, le_ld before executing below command
$ certbot certonly --manual -d *  --work-dir=le_wd --config-dir=le_cd --logs-dir=le_ld 

# Check if certificates are created
$ certbot certificates --work-dir=le_wd --config-dir=le_cd --logs-dir=le_ld

Certs are located at le_cd/live/ /

Create secret with the Certificates we want to use
$ kubectl create secret tls pd-custom-certs --key --cert -n namespace_of_interest

Configure ingress with the TLS secret.
----SNIP(FQDN 1)---- ingress: enabled: true path: / hosts: - tls: - hosts: - secretName: pd-custom-certs ----SNIP(FQDN 2)---- ingress: enabled: true path: / hosts: - tls: - secretName: pd-custom-certs hosts: -

Accessing ingress should not show invalid Cert errors now.

Kubernetes Pod Security Policies

Start minikube with RBAC and admission-plugins enabled
$ minikube start --extra-config=apiserver.authorization-mode=Node,RBAC --extra-config=apiserver.enable-admission-plugins=PodSecurityPolicy
# or
$ minikube start --extra-config=apiserver.authorization-mode=Node,RBAC --extra-config=apiserver.Admission.PluginNames=PodSecurityPolicy

These commands are not working on my Mac machine, looks like API Server issue as it is not accepting any requests (might not be up).

Create namespace and Service Account
$ kubectl create namespace praveend-psp kubectl create sa test-psp-sa -n praveend-psp

Policy definitions

Friday, December 7, 2018

Kubernetes Privilege Escalation (CVE-2018-1002105)


Kubernetes is an open source production grade container orchestration system for deploying and managing docker/container applications. There are managed kubernetes orchestration service providers like Amazon Elastic Container Service for Kubernetes (EKS), Azure Kubernetes Service (AKS) etc.


Kubernetes cluster users can perform management tasks using kubectl binary which talks to API Server. Example kubectl commands

# display pod resource
kubectl get pods -n my_namespace

# Execute a command in a container
kubectl -n my_namespace exec -it pods_name -- sh

# Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in the pod
kubectl -n my_namespace port-forward pod/mypod 5000 6000

# Get output from ruby-container from pod my-pod-pd

kubectl attach my-pod-pd -c ruby-container

kubectl execution flow (source:


kubelet, kube-proxy run's on each compute node (VM, Worker, EC2 Instance etc), kubelet listens on TCP port 10250 and 10255 (with no authentication/authorization). API Server acts as Reverse Proxy to kubelet and API Aggregation. API Server connects to the kubelet to fulfill commands like exec, port=forward and opens a websocket connection which connects stdin, stdout, or stderr to user’s original call [01].

API Aggregation

Installing or writing additional API's into Kubernetes API Server i.e. extending core API Server


Vulnerability is in Kubernetes API Server, crafted request can execute arbitrary commands on the backend servers (pods) through the same channel client established to backend through API Server [02]

Check nodes Kubernetes version
$ kubectl get nodes -o wide
pd-worker-01 Ready node 13d v1.12.3 Container Linux by CoreOS 1745.7.0 (Rhyolite) 4.14.48-coreos-r2 docker://18.3.1
pd-worker-02 Ready node 13d v1.12.3 Container Linux by CoreOS 1745.7.0 (Rhyolite) 4.14.48-coreos-r2 docker://18.3.1
pd-worker-03 Ready node 13d v1.12.3 Container Linux by CoreOS 1745.7.0 (Rhyolite) 4.14.48-coreos-r2 docker://18.3.1

Vulnerable API Servers

If API server response looks as bellow and using vulnerable API versions of Kubernetes the you are vulnerable using anonymous-user escalation, patch Kubernetes immediately.
HTTP response error code 403 indicates Forbidden i.e. related to Authorization implies we successfully passed through Authentication phase.
{ "kind": "Status", "apiVersion": "v1", "metadata": { }, "status": "Failure", "message": "forbidden: User \"system:anonymous\" cannot get path \"/api/v1/\"", "reason": "Forbidden", "details": { }, "code": 403 }

anonymous user

By default, requests to the kubelet’s HTTPS endpoint that are not rejected by other configured authentication methods are treated as anonymous requests, and given a username of system:anonymous and a group of system:unauthenticated.


There are three levels of escalation mitigations

1. anonymous user -> aggregated API server

API Server admission-controller parameter anonymous-auth is set to fault
$ kubectl get po kube-apiserver-01 -n prod -o yaml | grep -i "anonymous-auth" - --anonymous-auth=false 
$ kubectl get po kube-apiserver-01 -n stage -o yaml | grep -i "anonymous-auth" - --anonymous-auth=false

2. authenticated user -> aggregated API server

Suspend aggregated API servers usage

3. authorized pod exec/attach/portforward -> kubelet API

Remove pod exec/attach/portforward permissions for users



Saturday, January 20, 2018

AWS VPC Flow Logs grok Pattern

Amazon Web Services(AWS) can generate VPC flow logs, format below
2 123456789010 eni-abc123de 49761 3389 6 20 4249 1418530010 1418530070 REJECT OK

For more information on flow logs and grok filter plugin refer below links

grok patterns can be tested using below links

%{NONNEGINT:version} %{NONNEGINT:accountid} %{NOTSPACE:interface-id} %{NOTSPACE:srcaddr} %{NOTSPACE:dstaddr} %{NONNEGINT:srcport} %{NONNEGINT:dstport} %{NONNEGINT:protocol} %{NONNEGINT:packets} %{NONNEGINT:bytes} %{NONNEGINT:starttime} %{NONNEGINT:endtime} %{NOTSPACE:action} %{NOTSPACE:log-status}

Test using grokdebugger

Test using grokconstructor

You can also consider INT instead of NONNEGINT

Found few patterns by googling which looked like below, were not working on grokconstructor website.
%{NUMBER:version} %{NUMBER:account-id} %{NOTSPACE:interface-id} %{NOTSPACE:srcaddr} %{NOTSPACE:dstaddr} %{NOTSPACE:srcport:int} %{NOTSPACE:dstport:int} %{NOTSPACE:protocol:int} %{NOTSPACE:packets:int} %{NOTSPACE:bytes:int} %{NUMBER:start:int} %{NUMBER:end:int} %{NOTSPACE:action} %{NOTSPACE:log-status}

Tested on grokdebugger

Tested on grokconstructor

We can use the extracted variables from grok filter plugin in Kibana search or enhance data using logstash filter plugins geoip, dns, date etc.