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K3s Nats tls by openssl

   1526 words   4 minutes 
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  1. 透過 k3d 建立本地 k3s cluster。因為 k3s 也是透過 docker 來摸擬 k8s cluster，所以透過 k3s 本身 port mapping 的配置來對外開放 8080:80 及 4222:31400 二個 port。 8080:80 給 hashicorp/http-echo 用。而 4222:31400 是對應 NATS nodeport 用

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    k3d cluster create dev -p 8080:80@loadbalancer -p 8443:443@loadbalancer -p "4222:31400@server[0]"

  2. 建立 hashicorp/http-echo。等待所有的 Pod 及服務就緒後，就可以透過 http://localhost:8080 來讀取 hashicorp/http-echo

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    kubectl run --image hashicorp/http-echo --port 80 echo -- -listen=:80 --text="Hello from echo"
kubectl expose pod echo --port 80 --target-port 80 --type NodePort --name echo
cat <<EOF | kubectl apply -f -
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: echo-ingress
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          serviceName: echo
          servicePort: 80
EOF

  3. 下一個步驟就是建立 NATS。因為這一次我們要建立的是有啟用 TLS 的 NATS 服務器。而 TLS 的部份我們採用 self signed 的方式來建立，實際使用就看最終部署的情況來決定是誰來產出 cluster 有需的 TLS，而本 Demo 就方便的方式自建

  4. 首先建立所需的 certificate.conf 檔案。其中 IP 及 DNS 可以依照需求進行修改

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    cat <<EOF >> certificate.conf
[req]
default_bits = 2048
prompt = no
default_md = sha256
req_extensions = req_ext
distinguished_name = dn
[dn]
C = TW
ST = New Taipei City
O = Your organization
CN = localhost
[req_ext]
subjectAltName = @alt_names
[alt_names]
DNS.1 = kubernetes
DNS.2 = kubernetes.default
DNS.3 = kubernetes.default.svc
DNS.4 = kubernetes.default.svc.cluster
DNS.5 = kubernetes.default.svc.cluster.local
DNS.6 = localhost
IP.1 = 127.0.0.1
IP.2 = 172.17.34.52
IP.3 = 192.168.0.15
[v3_ext]
authorityKeyIdentifier=keyid,issuer:always
basicConstraints=CA:FALSE
keyUsage=keyEncipherment,dataEncipherment
extendedKeyUsage=serverAuth,clientAuth
subjectAltName=@alt_names
EOF

  5. 產生 NATS 服務器有需的 TLS 檔，及之後提供給 Client 使用的 client1.crt client1.key ca.crt client2.crt client2.key ca.crt。這邊使用的方式是透過 openssl，有效日期也是 demo 方便先設為 1000 天。另外我們將啟用 NATS tls verifyAndMap 的功能。所以我們在 certificate.conf 的 Subject Alternative Name (SAN) 會指定 email，當 NATS 有開啟 verifyAndMap 就會檢查 Subject Alternative Name (SAN)

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    cat <<EOF >> gen.sh
#!/bin/bash

# Move to root directory...
mkdir -p keys
cd keys

# Generate the Certificate Files
openssl genrsa -out ca.key 2048
openssl req -x509 -new -nodes -key ca.key -subj "/CN=localhost" -days 1000 -out ca.crt

# server
openssl genrsa -out server.key 2048
openssl req -new -key server.key -out server.csr -config ../certificate.conf
openssl x509 -req -in server.csr -CA ca.crt -CAkey ca.key \
    -CAcreateserial -out server.crt -days 1000 \
    -extensions v3_ext -extfile ../certificate.conf

# client1
openssl genrsa -out client1.key 2048
openssl req -new -key client1.key -out client1.csr -config ../certificate.conf
openssl x509 -req -in client1.csr -CA ca.crt -CAkey ca.key \
    -CAcreateserial -out client1.crt -days 1000 \
    -extensions v3_ext -extfile <(cat $(PWD)/certificate.conf | sed 's/IP.3 = 192.168.0.15/&\nemail.1 = [email protected]/')

echo $(PWD)
# client2
openssl genrsa -out client2.key 2048
openssl req -new -key client2.key -out client2.csr -config ../certificate.conf
openssl x509 -req -in client2.csr -CA ca.crt -CAkey ca.key \
    -CAcreateserial -out client2.crt -days 1000 \
    -extensions v3_ext -extfile ../certificate.conf        
EOF

chmod +x ./gen.sh
./gen.sh

  6. 我們產生了二組 client tls keypair。我們在產生 client1 的 tls 檔案時加入額外的 Subject Alternative Name (SAN) 資訊 email:[email protected]

    step: A zero trust swiss army knife for working with X509, OAuth, JWT, OATH OTP, etc. step-cli | Automate Certificates & Common Cryptography Primitives

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    step certificate inspect keys/client1.crt 
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 11938605982689757523 (0xa5ae72e347938953)
    Signature Algorithm: SHA1-RSA
        Issuer: CN=localhost
        Validity
            Not Before: Aug 19 03:20:51 2021 UTC
            Not After : May 15 03:20:51 2024 UTC
        Subject: C=TW,ST=New Taipei City,O=Your organization,CN=localhost
        Subject Public Key Info:
            Public Key Algorithm: RSA
                Public-Key: (2048 bit)
                Modulus:
                    ...
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Authority Key Identifier:
                keyid
            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Key Usage:
                Key Encipherment, Data Encipherment
            X509v3 Extended Key Usage:
                Server Authentication, Client Authentication
            X509v3 Subject Alternative Name:
                DNS:kubernetes, DNS:kubernetes.default, DNS:kubernetes.default.svc, DNS:kubernetes.default.svc.cluster, DNS:kubernetes.default.svc.cluster.local, DNS:localhost
                email:[email protected]
                IP Address:127.0.0.1, IP Address:172.17.34.52, IP Address:192.168.0.15
    Signature Algorithm: SHA1-RSA
        ...    

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    step certificate inspect keys/client2.crt 
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 11938605982689757524 (0xa5ae72e347938954)
    Signature Algorithm: SHA1-RSA
        Issuer: CN=localhost
        Validity
            Not Before: Aug 19 03:20:51 2021 UTC
            Not After : May 15 03:20:51 2024 UTC
        Subject: C=TW,ST=New Taipei City,O=Your organization,CN=localhost
        Subject Public Key Info:
            Public Key Algorithm: RSA
                Public-Key: (2048 bit)
                Modulus:
                    ...
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Authority Key Identifier:
                keyid
            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Key Usage:
                Key Encipherment, Data Encipherment
            X509v3 Extended Key Usage:
                Server Authentication, Client Authentication
            X509v3 Subject Alternative Name:
                DNS:kubernetes, DNS:kubernetes.default, DNS:kubernetes.default.svc, DNS:kubernetes.default.svc.cluster, DNS:kubernetes.default.svc.cluster.local, DNS:localhost
                IP Address:127.0.0.1, IP Address:172.17.34.52, IP Address:192.168.0.15
    Signature Algorithm: SHA1-RSA
        ...

  7. 透過 kubectl 建立稍後 NATS 服務器所需 TLS 相關的 secret nats-server-tls

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    kubectl create namespace nats
kubectl create secret generic nats-server-tls \
  --from-file=ca.crt=./keys/ca.crt \
  --from-file=tls.crt=./keys/server.crt \
  --from-file=tls.key=./keys/server.key \
  --namespace nats

  8. 透過 helm 來安裝 NATS 服務器，並指定稍早建立相關的 secret nats-server-tls

    記得先加入 nats helm chart repo

    $ helm repo add nats https://nats-io.github.io/k8s/helm/charts/

    $ helm repo update

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    helm install nats nats/nats \
    --set nats.tls.secret.name=nats-server-tls \
    --set nats.tls.ca=ca.crt \
    --set nats.tls.cert=tls.crt \
    --set nats.tls.key=tls.key \
    --set nats.tls.verifyAndMap=true \
    --set auth.enabled=true \
    --set auth.basic.users[0].user=[email protected] \
    --namespace nats

  9. 基本上作完這一步，如果我們透過 port-forward 的方式來 forward nats/nats-client 4222 已經可以讀取到 NATS 服務器。不過使用 helm 安裝的 nats/nats 預設沒有對外開放服務，又因為使用 k3s cluster 受限於 docker 的原因，我們需要額外指定 NodePort 31400 對應 k3s 4222:31400 的設定來給外部讀取

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    cat <<EOF >> nats-np.yaml
apiVersion: v1
kind: Service
metadata:
  name: nats-np
  namespace: nats
  labels:
    app.kubernetes.io/name: nats
    app.kubernetes.io/instance: nats
spec:
  type: NodePort
  ports:
    - name: tcp-client
      port: 4222
      nodePort: 31400
      targetPort: client
  selector:
    app.kubernetes.io/name: nats
    app.kubernetes.io/instance: nats
EOF

kubectl apply -f nats-np.yaml

  10. 讀取 nats://localhost:4222

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    nats -s localhost:4222 pub say hi

    nats: error: x509: certificate signed by unknown authority, try –help

    由於我們建立 NATS 服務器啟用 TLS，稍早也建立了一組 client1.crt client1.key ca.crt。再連接 NATS 服務器時代入相關的 tls 檔案即可正常操作

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    nats -s localhost \
    --tlscert=./keys/client1.crt \
    --tlskey=./keys/client1.key \
    --tlsca=./keys/ca.crt \
    pub say hi

    因為 NATS 啟用了 verifyAndMap，所以 client2.crt client2.key ca.crt 因為其 Subject Alternative Name (SAN) 沒有包含 email 資訊，所以就算擁有 tls keypair 也沒有權限讀取

    nats: error: nats: Authorization Violation, try –help

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    nats -s localhost \
    --tlscert=./keys/client2.crt \
    --tlskey=./keys/client2.key \
    --tlsca=./keys/ca.crt \
    pub say hi
Updated on 2023-09-07  43a38bf
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 k3s, tls, NATS, k8s
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