[AWS] EKS Security- 6주차

EC2 Instance Profile : 사용하기 편하지만, 최소 권한 부여 원칙에 위배하며 보안상 권고하지 않음 - 링크 → IRSA를 사용 권장

실습 목표 :

파드가 특정 IAM 역할로 Assume 할때 토큰을 AWS에 전송하고, AWS는 토큰과 EKS IdP를 통해 해당 IAM 역할을 사용할 수 있는지 검증

실습 1

-https://aws.amazon.com/ko/blogs/containers/diving-into-iam-roles-for-service-accounts/

# 파드1 생성
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: eks-iam-test1
spec:
  containers:
    - name: my-aws-cli
      image: amazon/aws-cli:latest
      args: ['s3', 'ls']
  restartPolicy: Never
  automountServiceAccountToken: false
EOF

# 확인
kubectl get pod
kubectl describe pod

# 로그 확인
kubectl logs eks-iam-test1

# 파드1 삭제
kubectl delete pod eks-iam-test1

CloudTrail 이벤트 ListBuckets 확인 → 기록 표시까지 약간의 시간 필요

링크 : https://ap-northeast-2.console.aws.amazon.com/cloudtrail/home?region=ap-northeast-2#/events?EventName=ListBuckets

https://ap-northeast-2.console.aws.amazon.com/cloudtrail/home?region=ap-northeast-2#/events?EventName=ListBuckets

ap-northeast-2.console.aws.amazon.com

{
...
  "userIdentity": {
    "type": "AssumedRole",
    "principalId": "xxxx",
    "arn": "arn:aws:sts::111122223333:assumed-role/eksctl-eks-oidc-demo-nodegroup-ng-NodeInstanceRole-xxxx/xxxx",
    "accountId": "111122223333",
    "accessKeyId": "AKIAIOSFODNN7EXAMPLE",
    "sessionContext": {
      "sessionIssuer": {
        "type": "Role",
        "principalId": "xxxx",
        "arn": "arn:aws:iam::xxxx:role/eksctl-eks-oidc-demo-nodegroup-ng-NodeInstanceRole-xxxx",
        "accountId": "111122223333",
        "userName": "eksctl-eks-oidc-demo-nodegroup-ng-NodeInstanceRole-xxxx"
      },
      "webIdFederationData": {},
      "attributes": {
        "creationDate": "2021-12-04T14:54:49Z",
        "mfaAuthenticated": "false"
      },
      "ec2RoleDelivery": "2.0"
    }
  },
  "eventTime": "2021-12-04T15:09:20Z",
  "eventSource": "s3.amazonaws.com",
  "eventName": "ListBuckets",
  "awsRegion": "us-east-2",
  "sourceIPAddress": "192.0.2.1",
  "userAgent": "[aws-cli/2.4.5 Python/3.8.8 Linux/5.4.156-83.273.amzn2.x86_64 docker/x86_64.amzn.2 prompt/off command/s3.ls]",
  "errorCode": "AccessDenied",
  "errorMessage": "Access Denied",
  "requestParameters": {
    "Host": "s3.us-east-2.amazonaws.com"
  },
...
}

권한 없음

실습 2

Kubernetes Service Accounts : https://jwt.io/
- Kubernetes Pods are given an identity through a Kubernetes concept called a Kubernetes Service Account.
- When a Service Account is created, a JWT token is automatically created as a Kubernetes Secret.
- This Secret can then be mounted into Pods and used by that Service Account to authenticate to the Kubernetes API Server.

# 파드2 생성
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: eks-iam-test2
spec:
  containers:
    - name: my-aws-cli
      image: amazon/aws-cli:latest
      command: ['sleep', '36000']
  restartPolicy: Never
EOF

# 확인
kubectl get pod
kubectl describe pod

# aws 서비스 사용 시도
kubectl exec -it eks-iam-test2 -- aws s3 ls

# 서비스 어카운트 토큰 확인
SA_TOKEN=$(kubectl exec -it eks-iam-test2 -- cat /var/run/secrets/kubernetes.io/serviceaccount/token)
echo $SA_TOKEN

# jwt 혹은 아래 JWT 웹 사이트 이용
jwt decode $SA_TOKEN --json --iso8601
...

#헤더
{
  "alg": "RS256",
  "kid": "1a8fcaee12b3a8f191327b5e9b997487ae93baab"
}

# 페이로드 : OAuth2에서 쓰이는 aud, exp 속성 확인! > projectedServiceAccountToken 기능으로 토큰에 audience,exp 항목을 덧붙힘
## iss 속성 : EKS OpenID Connect Provider(EKS IdP) 주소 > 이 EKS IdP를 통해 쿠버네티스가 발급한 토큰이 유요한지 검증
{
  "aud": [
    "https://kubernetes.default.svc"  # 해당 주소는 k8s api의 ClusterIP 서비스 주소 도메인명, kubectl get svc kubernetes
  ],
  "exp": 1716619848,
  "iat": 1685083848,
  "iss": "https://oidc.eks.ap-northeast-2.amazonaws.com/id/F6A7523462E8E6CDADEE5D41DF2E71F6",
  "kubernetes.io": {
    "namespace": "default",
    "pod": {
      "name": "eks-iam-test2",
      "uid": "10dcccc8-a16c-4fc7-9663-13c9448e107a"
    },
    "serviceaccount": {
      "name": "default",
      "uid": "acb6c60d-0c5f-4583-b83b-1b629b0bdd87"
    },
    "warnafter": 1685087455
  },
  "nbf": 1685083848,
  "sub": "system:serviceaccount:default:default"
}

# 파드2 삭제
kubectl delete pod eks-iam-test2

실습 3

https://github.com/aws/amazon-eks-pod-identity-webhook/ : This webhook is for mutating pods that will require AWS IAM access
- For the webhook to inject a new Token into our Pod, we are going to create a new Kubernetes Service Account, annotate our Service Account with an AWS IAM role ARN, and then reference this new Kubernetes Service Account in a Kubernetes Pod. The eksctl tool can be used to automate a few steps for us, but all of these steps can also be done manually.
- The eksctl create iamserviceaccount command creates:
  1. A Kubernetes Service Account
  2. An IAM role with the specified IAM policy
  3. A trust policy on that IAM role
- Finally, it will also annotate the Kubernetes Service Account with the IAM Role Arn created.

# Create an iamserviceaccount - AWS IAM role bound to a Kubernetes service account
eksctl create iamserviceaccount \
  --name my-sa \
  --namespace default \
  --cluster $CLUSTER_NAME \
  --approve \
  --attach-policy-arn $(aws iam list-policies --query 'Policies[?PolicyName==`AmazonS3ReadOnlyAccess`].Arn' --output text)

# 확인 >> 웹 관리 콘솔에서 CloudFormation Stack >> IAM Role 확인
# aws-load-balancer-controller IRSA는 어떤 동작을 수행할 것 인지 생각해보자!
eksctl get iamserviceaccount --cluster $CLUSTER_NAME

# Inspecting the newly created Kubernetes Service Account, we can see the role we want it to assume in our pod.
kubectl get sa
kubectl describe sa my-sa
Name:                my-sa
Namespace:           default
Labels:              app.kubernetes.io/managed-by=eksctl
Annotations:         eks.amazonaws.com/role-arn: arn:aws:iam::911283464785:role/eksctl-myeks-addon-iamserviceaccount-default-Role1-1MJUYW59O6QGH
Image pull secrets:  <none>
Mountable secrets:   <none>
Tokens:              <none>
Events:              <none>

# 파드3번 생성
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
  name: eks-iam-test3
spec:
  serviceAccountName: my-sa
  containers:
    - name: my-aws-cli
      image: amazon/aws-cli:latest
      command: ['sleep', '36000']
  restartPolicy: Never
EOF

# 해당 SA를 파드가 사용 시 mutatingwebhook으로 Env,Volume 추가함
kubectl get mutatingwebhookconfigurations pod-identity-webhook -o yaml | kubectl neat | yh

# 파드 생성 yaml에 없던 내용이 추가됨!!!!!
# Pod Identity Webhook은 mutating webhook을 통해 아래 Env 내용과 1개의 볼륨을 추가함
kubectl get pod eks-iam-test3
kubectl describe pod eks-iam-test3
...
Environment:
      AWS_STS_REGIONAL_ENDPOINTS:   regional
      AWS_DEFAULT_REGION:           ap-northeast-2
      AWS_REGION:                   ap-northeast-2
      AWS_ROLE_ARN:                 arn:aws:iam::911283464785:role/eksctl-myeks-addon-iamserviceaccount-default-Role1-GE2DZKJYWCEN
      AWS_WEB_IDENTITY_TOKEN_FILE:  /var/run/secrets/eks.amazonaws.com/serviceaccount/token
    Mounts:
      /var/run/secrets/eks.amazonaws.com/serviceaccount from aws-iam-token (ro)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-69rh8 (ro)
...
Volumes:
  aws-iam-token:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  86400
  kube-api-access-sn467:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
...

# 파드에서 aws cli 사용 확인
eksctl get iamserviceaccount --cluster $CLUSTER_NAME
kubectl exec -it eks-iam-test3 -- aws sts get-caller-identity --query Arn
"arn:aws:sts::911283464785:assumed-role/eksctl-myeks-addon-iamserviceaccount-default-Role1-GE2DZKJYWCEN/botocore-session-1685179271"

# 되는 것고 안되는 것은 왜그런가?
kubectl exec -it eks-iam-test3 -- aws s3 ls
kubectl exec -it eks-iam-test3 -- aws ec2 describe-instances --region ap-northeast-2
kubectl exec -it eks-iam-test3 -- aws ec2 describe-vpcs --region ap-northeast-2

iam 서비스 어카운트 생성

서비스 어카운트 상세보기

파트 내용보기

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전 공 설 명 서

[AWS] EKS Security- 6주차 - IRSA

실습 1

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실습 3

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