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Merge pull request #60385 from stealthybox/feature/kubeadm_710-etcd-ca
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kubeadm 710 Switch to a dedicated CA for kubeadm etcd identities

**What this PR does / why we need it**:
On `kubeadm init`/`kubeadm upgrade`, this PR generates an etcd specific CA for signing the following certs:
- etcd serving cert
- etcd peer cert
- apiserver etcd client cert

These certs were previously signed by the kubernetes CA.
The etcd static pod in `local.go` has also been updated to only mount the `/etcd` subdir of `cfg.CertificatesDir`.

New phase command:
```
kubeadm alpha phase certs etcd-ca
```

See the linked issue for details on why this change is an important security feature.

**Which issue(s) this PR fixes**
Fixes kubernetes/kubeadm#710

**Special notes for your reviewer**:

#### on the master
this should still fail:
```bash
curl localhost:2379/v2/keys  # no output
curl --cacert /etc/kubernetes/pki/etcd/ca.crt https://localhost:2379/v2/keys  # handshake error
```
this should now fail: (previously would succeed)
```
cd /etc/kubernetes/pki
curl --cacert etcd/ca.crt --cert apiserver-kubelet-client.crt --key apiserver-kubelet-client.key https://localhost:2379/v2/keys
  # curl: (35) error:14094412:SSL routines:ssl3_read_bytes:sslv3 alert bad certificate
```
this should still succeed:
```
cd /etc/kubernetes/pki
curl --cacert etcd/ca.crt --cert apiserver-etcd-client.crt --key apiserver-etcd-client.key https://localhost:2379/v2/keys
```

**Release note**:
```release-note
On cluster provision or upgrade, kubeadm generates an etcd specific CA for all etcd related certificates.
```
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Kubernetes Submit Queue authored Mar 1, 2018
2 parents 58731ae + 41974cb commit 5cff6c9
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Showing 14 changed files with 152 additions and 72 deletions.
34 changes: 23 additions & 11 deletions cmd/kubeadm/app/cmd/phases/certs.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -44,15 +44,15 @@ var (

allCertsExample = normalizer.Examples(`
# Creates all PKI assets necessary to establish the control plane,
# functionally equivalent to what generated by kubeadm init.
# functionally equivalent to what generated by kubeadm init.
kubeadm alpha phase certs all
# Creates all PKI assets using options read from a configuration file.
kubeadm alpha phase certs all --config masterconfiguration.yaml
`)

caCertLongDesc = fmt.Sprintf(normalizer.LongDesc(`
Generates the self-signed certificate authority and related key, and saves them into %s and %s files.
Generates the self-signed kubernetes certificate authority and related key, and saves them into %s and %s files.
If both files already exist, kubeadm skips the generation step and existing files will be used.
`+cmdutil.AlphaDisclaimer), kubeadmconstants.CACertName, kubeadmconstants.CAKeyName)
Expand All @@ -74,6 +74,12 @@ var (
If both files already exist, kubeadm skips the generation step and existing files will be used.
`+cmdutil.AlphaDisclaimer), kubeadmconstants.APIServerKubeletClientCertName, kubeadmconstants.APIServerKubeletClientKeyName)

etcdCaCertLongDesc = fmt.Sprintf(normalizer.LongDesc(`
Generates the self-signed etcd certificate authority and related key and saves them into %s and %s files.
If both files already exist, kubeadm skips the generation step and existing files will be used.
`+cmdutil.AlphaDisclaimer), kubeadmconstants.EtcdCACertName, kubeadmconstants.EtcdCAKeyName)

etcdServerCertLongDesc = fmt.Sprintf(normalizer.LongDesc(`
Generates the etcd serving certificate and key and saves them into %s and %s files.
Expand Down Expand Up @@ -166,37 +172,43 @@ func getCertsSubCommands(defaultKubernetesVersion string) []*cobra.Command {
},
{
use: "ca",
short: "Generates self-signed CA to provision identities for each component in the cluster",
short: "Generates a self-signed kubernetes CA to provision identities for components of the cluster",
long: caCertLongDesc,
cmdFunc: certsphase.CreateCACertAndKeyfiles,
cmdFunc: certsphase.CreateCACertAndKeyFiles,
},
{
use: "apiserver",
short: "Generates API server serving certificate and key",
short: "Generates an API server serving certificate and key",
long: apiServerCertLongDesc,
cmdFunc: certsphase.CreateAPIServerCertAndKeyFiles,
},
{
use: "apiserver-kubelet-client",
short: "Generates client certificate for the API server to connect to the kubelets securely",
short: "Generates a client certificate for the API server to connect to the kubelets securely",
long: apiServerKubeletCertLongDesc,
cmdFunc: certsphase.CreateAPIServerKubeletClientCertAndKeyFiles,
},
{
use: "etcd-ca",
short: "Generates a self-signed CA to provision identities for etcd",
long: etcdCaCertLongDesc,
cmdFunc: certsphase.CreateEtcdCACertAndKeyFiles,
},
{
use: "etcd-server",
short: "Generates etcd serving certificate and key",
short: "Generates an etcd serving certificate and key",
long: etcdServerCertLongDesc,
cmdFunc: certsphase.CreateEtcdServerCertAndKeyFiles,
},
{
use: "etcd-peer",
short: "Generates etcd peer certificate and key",
short: "Generates an etcd peer certificate and key",
long: etcdPeerCertLongDesc,
cmdFunc: certsphase.CreateEtcdPeerCertAndKeyFiles,
},
{
use: "apiserver-etcd-client",
short: "Generates client certificate for the API server to connect to etcd securely",
short: "Generates a client certificate for the API server to connect to etcd securely",
long: apiServerEtcdServerCertLongDesc,
cmdFunc: certsphase.CreateAPIServerEtcdClientCertAndKeyFiles,
},
Expand All @@ -208,13 +220,13 @@ func getCertsSubCommands(defaultKubernetesVersion string) []*cobra.Command {
},
{
use: "front-proxy-ca",
short: "Generates front proxy CA certificate and key for a Kubernetes cluster",
short: "Generates a front proxy CA certificate and key for a Kubernetes cluster",
long: frontProxyCaCertLongDesc,
cmdFunc: certsphase.CreateFrontProxyCACertAndKeyFiles,
},
{
use: "front-proxy-client",
short: "Generates front proxy CA client certificate and key for a Kubernetes cluster",
short: "Generates a front proxy CA client certificate and key for a Kubernetes cluster",
long: frontProxyClientCertLongDesc,
cmdFunc: certsphase.CreateFrontProxyClientCertAndKeyFiles,
},
Expand Down
7 changes: 7 additions & 0 deletions cmd/kubeadm/app/constants/constants.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,13 @@ const (
// APIServerKubeletClientCertCommonName defines kubelet client certificate common name (CN)
APIServerKubeletClientCertCommonName = "kube-apiserver-kubelet-client"

// EtcdCACertAndKeyBaseName defines etcd's CA certificate and key base name
EtcdCACertAndKeyBaseName = "etcd/ca"
// EtcdCACertName defines etcd's CA certificate name
EtcdCACertName = "etcd/ca.crt"
// EtcdCAKeyName defines etcd's CA key name
EtcdCAKeyName = "etcd/ca.key"

// EtcdServerCertAndKeyBaseName defines etcd's server certificate and key base name
EtcdServerCertAndKeyBaseName = "etcd/server"
// EtcdServerCertName defines etcd's server certificate name
Expand Down
81 changes: 56 additions & 25 deletions cmd/kubeadm/app/phases/certs/certs.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,9 +34,10 @@ import (
func CreatePKIAssets(cfg *kubeadmapi.MasterConfiguration) error {

certActions := []func(cfg *kubeadmapi.MasterConfiguration) error{
CreateCACertAndKeyfiles,
CreateCACertAndKeyFiles,
CreateAPIServerCertAndKeyFiles,
CreateAPIServerKubeletClientCertAndKeyFiles,
CreateEtcdCACertAndKeyFiles,
CreateEtcdServerCertAndKeyFiles,
CreateEtcdPeerCertAndKeyFiles,
CreateAPIServerEtcdClientCertAndKeyFiles,
Expand All @@ -57,9 +58,9 @@ func CreatePKIAssets(cfg *kubeadmapi.MasterConfiguration) error {
return nil
}

// CreateCACertAndKeyfiles create a new self signed CA certificate and key files.
// CreateCACertAndKeyFiles create a new self signed cluster CA certificate and key files.
// If the CA certificate and key files already exists in the target folder, they are used only if evaluated equal; otherwise an error is returned.
func CreateCACertAndKeyfiles(cfg *kubeadmapi.MasterConfiguration) error {
func CreateCACertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := NewCACertAndKey()
if err != nil {
Expand All @@ -76,7 +77,7 @@ func CreateCACertAndKeyfiles(cfg *kubeadmapi.MasterConfiguration) error {

// CreateAPIServerCertAndKeyFiles create a new certificate and key files for the apiserver.
// If the apiserver certificate and key files already exists in the target folder, they are used only if evaluated equal; otherwise an error is returned.
// It assumes the cluster CA certificate and key files should exists into the CertificatesDir
// It assumes the cluster CA certificate and key files exist in the CertificatesDir.
func CreateAPIServerCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.CACertAndKeyBaseName)
Expand All @@ -98,9 +99,9 @@ func CreateAPIServerCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {
)
}

// CreateAPIServerKubeletClientCertAndKeyFiles create a new CA certificate for kubelets calling apiserver
// CreateAPIServerKubeletClientCertAndKeyFiles create a new certificate for kubelets calling apiserver.
// If the apiserver-kubelet-client certificate and key files already exists in the target folder, they are used only if evaluated equals; otherwise an error is returned.
// It assumes the cluster CA certificate and key files should exists into the CertificatesDir
// It assumes the cluster CA certificate and key files exist in the CertificatesDir.
func CreateAPIServerKubeletClientCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.CACertAndKeyBaseName)
Expand All @@ -122,73 +123,92 @@ func CreateAPIServerKubeletClientCertAndKeyFiles(cfg *kubeadmapi.MasterConfigura
)
}

// CreateEtcdCACertAndKeyFiles create a self signed etcd CA certificate and key files.
// The etcd CA and client certs are used to secure communication between etcd peers and connections to etcd from the API server.
// This is a separate CA, so that kubernetes client identities cannot connect to etcd directly or peer with the etcd cluster.
// If the etcd CA certificate and key files already exists in the target folder, they are used only if evaluated equals; otherwise an error is returned.
func CreateEtcdCACertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

etcdCACert, etcdCAKey, err := NewEtcdCACertAndKey()
if err != nil {
return err
}

return writeCertificateAuthorithyFilesIfNotExist(
cfg.CertificatesDir,
kubeadmconstants.EtcdCACertAndKeyBaseName,
etcdCACert,
etcdCAKey,
)
}

// CreateEtcdServerCertAndKeyFiles create a new certificate and key file for etcd.
// If the etcd serving certificate and key file already exist in the target folder, they are used only if evaluated equal; otherwise an error is returned.
// It assumes the cluster CA certificate and key file exist in the CertificatesDir
// It assumes the etcd CA certificate and key file exist in the CertificatesDir
func CreateEtcdServerCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.CACertAndKeyBaseName)
etcdCACert, etcdCAKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.EtcdCACertAndKeyBaseName)
if err != nil {
return err
}

etcdServerCert, etcdServerKey, err := NewEtcdServerCertAndKey(cfg, caCert, caKey)
etcdServerCert, etcdServerKey, err := NewEtcdServerCertAndKey(cfg, etcdCACert, etcdCAKey)
if err != nil {
return err
}

return writeCertificateFilesIfNotExist(
cfg.CertificatesDir,
kubeadmconstants.EtcdServerCertAndKeyBaseName,
caCert,
etcdCACert,
etcdServerCert,
etcdServerKey,
)
}

// CreateEtcdPeerCertAndKeyFiles create a new certificate and key file for etcd peering.
// If the etcd peer certificate and key file already exist in the target folder, they are used only if evaluated equal; otherwise an error is returned.
// It assumes the cluster CA certificate and key file exist in the CertificatesDir
// It assumes the etcd CA certificate and key file exist in the CertificatesDir
func CreateEtcdPeerCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.CACertAndKeyBaseName)
etcdCACert, etcdCAKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.EtcdCACertAndKeyBaseName)
if err != nil {
return err
}

etcdPeerCert, etcdPeerKey, err := NewEtcdPeerCertAndKey(cfg, caCert, caKey)
etcdPeerCert, etcdPeerKey, err := NewEtcdPeerCertAndKey(cfg, etcdCACert, etcdCAKey)
if err != nil {
return err
}

return writeCertificateFilesIfNotExist(
cfg.CertificatesDir,
kubeadmconstants.EtcdPeerCertAndKeyBaseName,
caCert,
etcdCACert,
etcdPeerCert,
etcdPeerKey,
)
}

// CreateAPIServerEtcdClientCertAndKeyFiles create a new client certificate for the apiserver calling etcd
// If the apiserver-etcd-client certificate and key file already exist in the target folder, they are used only if evaluated equal; otherwise an error is returned.
// It assumes the cluster CA certificate and key file exist in the CertificatesDir
// It assumes the etcd CA certificate and key file exist in the CertificatesDir
func CreateAPIServerEtcdClientCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.CACertAndKeyBaseName)
etcdCACert, etcdCAKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.EtcdCACertAndKeyBaseName)
if err != nil {
return err
}

apiEtcdClientCert, apiEtcdClientKey, err := NewAPIServerEtcdClientCertAndKey(caCert, caKey)
apiEtcdClientCert, apiEtcdClientKey, err := NewAPIServerEtcdClientCertAndKey(etcdCACert, etcdCAKey)
if err != nil {
return err
}

return writeCertificateFilesIfNotExist(
cfg.CertificatesDir,
kubeadmconstants.APIServerEtcdClientCertAndKeyBaseName,
caCert,
etcdCACert,
apiEtcdClientCert,
apiEtcdClientKey,
)
Expand Down Expand Up @@ -232,7 +252,7 @@ func CreateFrontProxyCACertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) erro

// CreateFrontProxyClientCertAndKeyFiles create a new certificate for proxy server client.
// If the front-proxy-client certificate and key files already exists in the target folder, they are used only if evaluated equals; otherwise an error is returned.
// It assumes the front proxy CAA certificate and key files should exists into the CertificatesDir
// It assumes the front proxy CA certificate and key files exist in the CertificatesDir.
func CreateFrontProxyClientCertAndKeyFiles(cfg *kubeadmapi.MasterConfiguration) error {

frontProxyCACert, frontProxyCAKey, err := loadCertificateAuthority(cfg.CertificatesDir, kubeadmconstants.FrontProxyCACertAndKeyBaseName)
Expand Down Expand Up @@ -265,7 +285,7 @@ func NewCACertAndKey() (*x509.Certificate, *rsa.PrivateKey, error) {
return caCert, caKey, nil
}

// NewAPIServerCertAndKey generate CA certificate for apiserver, signed by the given CA.
// NewAPIServerCertAndKey generate certificate for apiserver, signed by the given CA.
func NewAPIServerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

altNames, err := pkiutil.GetAPIServerAltNames(cfg)
Expand All @@ -286,7 +306,7 @@ func NewAPIServerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.Ce
return apiCert, apiKey, nil
}

// NewAPIServerKubeletClientCertAndKey generate CA certificate for the apiservers to connect to the kubelets securely, signed by the given CA.
// NewAPIServerKubeletClientCertAndKey generate certificate for the apiservers to connect to the kubelets securely, signed by the given CA.
func NewAPIServerKubeletClientCertAndKey(caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

config := certutil.Config{
Expand All @@ -302,7 +322,18 @@ func NewAPIServerKubeletClientCertAndKey(caCert *x509.Certificate, caKey *rsa.Pr
return apiClientCert, apiClientKey, nil
}

// NewEtcdServerCertAndKey generate CA certificate for etcd, signed by the given CA.
// NewEtcdCACertAndKey generate a self signed etcd CA.
func NewEtcdCACertAndKey() (*x509.Certificate, *rsa.PrivateKey, error) {

etcdCACert, etcdCAKey, err := pkiutil.NewCertificateAuthority()
if err != nil {
return nil, nil, fmt.Errorf("failure while generating etcd CA certificate and key: %v", err)
}

return etcdCACert, etcdCAKey, nil
}

// NewEtcdServerCertAndKey generate certificate for etcd, signed by the given CA.
func NewEtcdServerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

altNames, err := pkiutil.GetEtcdAltNames(cfg)
Expand All @@ -323,7 +354,7 @@ func NewEtcdServerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.C
return etcdServerCert, etcdServerKey, nil
}

// NewEtcdPeerCertAndKey generate CA certificate for etcd peering, signed by the given CA.
// NewEtcdPeerCertAndKey generate certificate for etcd peering, signed by the given CA.
func NewEtcdPeerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

altNames, err := pkiutil.GetEtcdPeerAltNames(cfg)
Expand All @@ -344,7 +375,7 @@ func NewEtcdPeerCertAndKey(cfg *kubeadmapi.MasterConfiguration, caCert *x509.Cer
return etcdPeerCert, etcdPeerKey, nil
}

// NewAPIServerEtcdClientCertAndKey generate CA certificate for the apiservers to connect to etcd securely, signed by the given CA.
// NewAPIServerEtcdClientCertAndKey generate certificate for the apiservers to connect to etcd securely, signed by the given CA.
func NewAPIServerEtcdClientCertAndKey(caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

config := certutil.Config{
Expand Down Expand Up @@ -383,7 +414,7 @@ func NewFrontProxyCACertAndKey() (*x509.Certificate, *rsa.PrivateKey, error) {
return frontProxyCACert, frontProxyCAKey, nil
}

// NewFrontProxyClientCertAndKey generate CA certificate for proxy server client, signed by the given front proxy CA.
// NewFrontProxyClientCertAndKey generate certificate for proxy server client, signed by the given front proxy CA.
func NewFrontProxyClientCertAndKey(frontProxyCACert *x509.Certificate, frontProxyCAKey *rsa.PrivateKey) (*x509.Certificate, *rsa.PrivateKey, error) {

config := certutil.Config{
Expand Down
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