Kubeadm证书过期时间调整

kubeadm 默认证书为一年，一年过期后，会导致api service不可用，使用过程中会出现：x509: certificate has expired or is not yet valid.

方案一 通过修改kubeadm 调整证书过期时间

修改代码，调整过期时间

克隆代码：git clone https://github.com/kubernetes/kubernetes.git, 切换到指定的tag或者版本修改vendor/k8s.io/client-go/util/cert/cert.go文件，git diff 对比如下：

diff --git a/staging/src/k8s.io/client-go/util/cert/cert.go b/staging/src/k8s.io/client-go/util/cert/cert.go
index fb7f5fa..e800962 100644
--- a/staging/src/k8s.io/client-go/util/cert/cert.go
+++ b/staging/src/k8s.io/client-go/util/cert/cert.go
@@ -104,7 +104,7 @@ func NewSignedCert(cfg Config, key *rsa.PrivateKey, caCert *x509.Certificate, ca
                IPAddresses:  cfg.AltNames.IPs,
                SerialNumber: serial,
                NotBefore:    caCert.NotBefore,
-               NotAfter:     time.Now().Add(duration365d).UTC(),
+               NotAfter:     time.Now().Add(duration365d * 10).UTC(),
                KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
                ExtKeyUsage:  cfg.Usages,
        }
@@ -149,7 +149,7 @@ func GenerateSelfSignedCertKey(host string, alternateIPs []net.IP, alternateDNS
                        CommonName: fmt.Sprintf("%s-ca@%d", host, time.Now().Unix()),
                },
                NotBefore: time.Now(),
-               NotAfter:  time.Now().Add(time.Hour * 24 * 365),
+               NotAfter:  time.Now().Add(time.Hour * 24 * 3650),

                KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
                BasicConstraintsValid: true,

编译代码

这里我们可以使用官方容器对代码进行编译。

k8s.gcr.io/kube-cross:v1.12.5-1，如果不能翻墙的用户，可以拉取我个人下的镜像skymyyang/kube-cross:v1.12.5-1

docker pull skymyyang/kube-cross:v1.12.5-1

编译

docker run --rm -v 你修改后的代码目录:/go/src/k8s.io/kubernetes -it skymyyang/kube-cross:v1.12.5-1 bash

cd /go/src/k8s.io/kubernetes

# 编译kubeadm, 这里主要编译kubeadm 即可
make all WHAT=cmd/kubeadm GOFLAGS=-v

# 编译kubelet
# make all WHAT=cmd/kubelet GOFLAGS=-v

# 编译kubectl
# make all WHAT=cmd/kubectl GOFLAGS=-v

#编译完产物在 _output/bin/kubeadm 目录下
#将kubeadm 文件拷贝出来，替换系统中的kubeadm

替换证书

#用新的kubeadm 替换官方的kubeadm
chmod +x kubeadm && cp -f kubeadm /usr/bin

#备份原有的证书
mv /etc/kubernetes/pki /etc/kubernetes/pki.old

#生成新的证书，kubeadm.yaml 指定你自己服务器上的
kubeadm alpha phase certs all --config  ~/kubeadm.yaml

#备份原有的conf文件
mv /etc/kubernetes/*conf /etc/kubernetes/*conf-old

#根据新证书重新生成新的配置文件
kubeadm alpha phase kubeconfig all --config ~/kubeadm.yaml

#替换老的config文件
cp -f /etc/kubernetes/admin.conf ~/.kube/config

方案二 启用自动轮换kubelet 证书

kubelet证书分为server和client两种， k8s 1.9默认启用了client证书的自动轮换，但server证书自动轮换需要用户开启

增加 kubelet 参数

# 在/etc/systemd/system/kubelet.service.d/10-kubeadm.conf 增加如下参数
Environment="KUBELET_EXTRA_ARGS=--feature-gates=RotateKubeletServerCertificate=true"

增加 controller-manager 参数

# 在/etc/kubernetes/manifests/kube-controller-manager.yaml 添加如下参数
  - command:
    - kube-controller-manager
    - --experimental-cluster-signing-duration=87600h0m0s
    - --feature-gates=RotateKubeletServerCertificate=true
    - ....

创建 rbac 对象

创建rbac对象，允许节点轮换kubelet server证书：

cat > ca-update.yaml << EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    rbac.authorization.kubernetes.io/autoupdate: "true"
  labels:
    kubernetes.io/bootstrapping: rbac-defaults
  name: system:certificates.k8s.io:certificatesigningrequests:selfnodeserver
rules:
- apiGroups:
  - certificates.k8s.io
  resources:
  - certificatesigningrequests/selfnodeserver
  verbs:
  - create
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: kubeadm:node-autoapprove-certificate-server
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:certificates.k8s.io:certificatesigningrequests:selfnodeserver
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: system:nodes
EOF

kubectl create –f ca-update.yaml

如果证书已经过期，如何进行重新签发证书

针对kubeadm 1.13.x 及以上处理

准备kubeadm.conf 配置文件一份

apiVersion: kubeadm.k8s.io/v1beta1
kind: ClusterConfiguration
kubernetesVersion: v1.14.1 #-->这里改成你集群对应的版本
imageRepository: registry.cn-hangzhou.aliyuncs.com/google_containers 
#这里使用国内的镜像仓库，否则在重新签发的时候会报错：could not fetch a Kubernetes version from the internet: unable to get URL "https://dl.k8s.io/release/stable-1.txt"

重新签发命令

kubeadm alpha certs renew all --config=/root/kubeadm.conf

运行如上命令会重新生成以下证书
#-- /etc/kubernetes/pki/apiserver.key
#-- /etc/kubernetes/pki/apiserver.crt

#-- /etc/kubernetes/pki/apiserver-etcd-client.key
#-- /etc/kubernetes/pki/apiserver-etcd-client.crt

#-- /etc/kubernetes/pki/apiserver-kubelet-client.key
#-- /etc/kubernetes/pki/apiserver-kubelet-client.crt

#-- /etc/kubernetes/pki/front-proxy-client.key
#-- /etc/kubernetes/pki/front-proxy-client.crt

#-- /etc/kubernetes/pki/etcd/healthcheck-client.key
#-- /etc/kubernetes/pki/etcd/healthcheck-client.crt

#-- /etc/kubernetes/pki/etcd/peer.key
#-- /etc/kubernetes/pki/etcd/peer.crt

#-- /etc/kubernetes/pki/etcd/server.key
#-- /etc/kubernetes/pki/etcd/server.crt

完成后重启kube-apiserver,kube-controller,kube-scheduler,etcd这4个容器

针对kubeadm 1.13.0（不包含1.13.0） 以下处理

移动证书和配置【注意！必须移动，不然会使用现有的证书，不会重新生成】

cd /etc/kubernetes
mkdir ./pki_bak
mkdir ./pki_bak/etcd
mkdir ./conf_bak
mv pki/apiserver* ./pki_bak/
mv pki/front-proxy-client.* ./pki_bak/
mv pki/etcd/healthcheck-client.* ./pki_bak/etcd/
mv pki/etcd/peer.* ./pki_bak/etcd/
mv pki/etcd/server.* ./pki_bak/etcd/
mv ./admin.conf ./conf_bak/
mv ./kubelet.conf ./conf_bak/
mv ./controller-manager.conf ./conf_bak/
mv ./scheduler.conf ./conf_bak/

创建证书

kubeadm alpha phase certs all --apiserver-advertise-address=${MASTER_API_SERVER_IP} --apiserver-cert-extra-sans=主机内网ip,主机公网ip

运行如上命令会重新生成以下证书
#-- /etc/kubernetes/pki/apiserver.key
#-- /etc/kubernetes/pki/apiserver.crt

#-- /etc/kubernetes/pki/apiserver-etcd-client.key
#-- /etc/kubernetes/pki/apiserver-etcd-client.crt

#-- /etc/kubernetes/pki/apiserver-kubelet-client.key
#-- /etc/kubernetes/pki/apiserver-kubelet-client.crt

#-- /etc/kubernetes/pki/front-proxy-client.key
#-- /etc/kubernetes/pki/front-proxy-client.crt

#-- /etc/kubernetes/pki/etcd/healthcheck-client.key
#-- /etc/kubernetes/pki/etcd/healthcheck-client.crt

#-- /etc/kubernetes/pki/etcd/peer.key
#-- /etc/kubernetes/pki/etcd/peer.crt

#-- /etc/kubernetes/pki/etcd/server.key
#-- /etc/kubernetes/pki/etcd/server.crt

不移动证书会有如下提示
#[certificates] Using the existing apiserver certificate and key.
#[certificates] Using the existing apiserver-kubelet-client certificate and key.
#[certificates] Using the existing front-proxy-client certificate and key.
#[certificates] Using the existing etcd/server certificate and key.
#[certificates] Using the existing etcd/peer certificate and key.
#[certificates] Using the existing etcd/healthcheck-client certificate and key.
#[certificates] Using the existing apiserver-etcd-client certificate and key.
#[certificates] valid certificates and keys now exist in "/etc/kubernetes/pki"
#[certificates] Using the existing sa key.

生成新配置文件

kubeadm alpha phase kubeconfig all --apiserver-advertise-address=${MASTER_API_SERVER_IP}

将新生成的admin配置文件覆盖掉原本的admin文件

mv $HOME/.kube/config $HOME/.kube/config.old
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
sudo chmod 777 $HOME/.kube/config

完成后重启kube-apiserver,kube-controller,kube-scheduler,etcd这4个容器

如果有多台master，则将第一台生成的相关证书拷贝到其余master即可。

kubeadm 1.14 证书调整教程

kubeadm部署的kubernets证书一直都是个诟病，默认都只有一年有效期，kubeadm 1.14.x安装后有部分证书还是一年有效期，但个别证书已修改为10年有效期，但对我们使用来说，一年有效期还是一个比较的坑，需要进行调整。

修改kubeadm 1.14.x源码，调整证书过期时间

kubeadm1.14.x 安装过后crt证书如下所示

/etc/kubernetes/pki/apiserver.crt
/etc/kubernetes/pki/front-proxy-ca.crt         #10年有效期
/etc/kubernetes/pki/ca.crt                     #10年有效期
/etc/kubernetes/pki/apiserver-etcd-client.crt
/etc/kubernetes/pki/front-proxy-client.crt     #10年有效期
/etc/kubernetes/pki/etcd/server.crt
/etc/kubernetes/pki/etcd/ca.crt                #10年有效期
/etc/kubernetes/pki/etcd/peer.crt              #10年有效期
/etc/kubernetes/pki/etcd/healthcheck-client.crt
/etc/kubernetes/pki/apiserver-kubelet-client.crt

如上所示，除了标注说明的证书为10年有效期，其余都是1年有效期，我们查看下原先调整证书有效期的源码，克隆kubernetes 源码，切换到1.14.1 tag 查看：
代码目录： staging/src/k8s.io/client-go/util/cert/cert.go

const duration365d = time.Hour * 24 * 365

func NewSelfSignedCACert(cfg Config, key crypto.Signer) (*x509.Certificate, error) {
    now := time.Now()
    tmpl := x509.Certificate{
        SerialNumber: new(big.Int).SetInt64(0),
        Subject: pkix.Name{
            CommonName:   cfg.CommonName,
            Organization: cfg.Organization,
        },
        NotBefore:             now.UTC(),
        //这里已经调整为10年有效期
        NotAfter:              now.Add(duration365d * 10).UTC(),
        KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
        BasicConstraintsValid: true,
        IsCA:                  true,
    }

    certDERBytes, err := x509.CreateCertificate(cryptorand.Reader, &tmpl, &tmpl, key.Public(), key)
    if err != nil {
        return nil, err
    }
    return x509.ParseCertificate(certDERBytes)
}

如上所示，通过NewSelfSignedCACert这个方法签发的证书都默认为10年有效期了，但这个只影响部分证书，但这样还没满足我们的需求，个别证书的有效期调整，在经过对源码的分析后，找到了如下的逻辑：

发现部分证书是通过NewSignedCert这个方法签发，而这个方法签发的证书默认只有一年有效期，查看代码逻辑：
代码: cmd/kubeadm/app/util/pkiutil/pki_helpers.go

const duration365d = time.Hour * 24 * 365

func NewSignedCert(cfg *certutil.Config, key crypto.Signer, caCert *x509.Certificate, caKey crypto.Signer) (*x509.Certificate, error) {
    serial, err := rand.Int(rand.Reader, new(big.Int).SetInt64(math.MaxInt64))
    if err != nil {
        return nil, err
    }
    if len(cfg.CommonName) == 0 {
        return nil, errors.New("must specify a CommonName")
    }
    if len(cfg.Usages) == 0 {
        return nil, errors.New("must specify at least one ExtKeyUsage")
    }

    certTmpl := x509.Certificate{
        Subject: pkix.Name{
            CommonName:   cfg.CommonName,
            Organization: cfg.Organization,
        },
        DNSNames:     cfg.AltNames.DNSNames,
        IPAddresses:  cfg.AltNames.IPs,
        SerialNumber: serial,
        NotBefore:    caCert.NotBefore,
        // 只有一年有效期
        NotAfter:     time.Now().Add(duration365d).UTC(),
        KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
        ExtKeyUsage:  cfg.Usages,
    }
    certDERBytes, err := x509.CreateCertificate(cryptorand.Reader, &certTmpl, caCert, key.Public(), caKey)
    if err != nil {
        return nil, err
    }
    return x509.ParseCertificate(certDERBytes)
}

至此，调整NewSignedCert这个方法，重新进行编译，将证书有效期调整为你想要的任何时间。

原文链接：

http://icyxp.github.io/blog/2019/05/k8s-kubeadm14-ca-upgrade.html