/
renewer.go
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/
renewer.go
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// Copyright (c) 2022 Cisco and/or its affiliates. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cert
import (
"context"
"time"
"emperror.dev/errors"
"github.com/go-logr/logr"
)
// AfterCheckFunctionType is the function signature for functions run if the
// check was triggered from outside or after the certificate was renewed.
type AfterCheckFunctionType func(certificate *Certificate, needsUpdate bool) error
// Renewer handles the automatic renewal of certificates.
type Renewer struct {
// logger is the interface containing log helper functions.
logger logr.Logger
// dnsNames are holding the DNS names for the server certificate generation.
dnsNames []string
// certificateDirectoryPath is the path of the directory where the generated
// certificates should be written.
certificateDirectoryPath string
// afterCheckFunctions are optional callbacks for triggered checks and
// renewals.
afterCheckFunctions []AfterCheckFunctionType
}
// NewRenewer returns a certificate renewer configured to the specified values.
func NewRenewer(
logger logr.Logger,
dnsNames []string,
certificateDirectoryPath string,
shouldCheckCertificate bool,
afterCheckFunctions ...AfterCheckFunctionType,
) (*Renewer, error) {
if dnsNames == nil {
dnsNames = []string{}
}
renewer := &Renewer{
logger: logger,
dnsNames: dnsNames,
certificateDirectoryPath: certificateDirectoryPath,
afterCheckFunctions: afterCheckFunctions,
}
if shouldCheckCertificate {
err := renewer.checkCertificate(true)
if err != nil {
return nil, errors.Wrap(err, "checking certificate failed")
}
}
return renewer, nil
}
func (renewer *Renewer) Start(ctx context.Context, triggers <-chan struct{}) error {
if renewer == nil {
return errors.Errorf("invalid nil renewer")
}
err := renewer.checkCertificate(true)
if err != nil {
return errors.Wrap(err, "checking certificate failed")
}
ticker := time.NewTicker(30 * time.Second)
defer ticker.Stop()
for {
select {
case <-triggers:
_ = renewer.checkCertificate(true)
case <-ticker.C:
_ = renewer.checkCertificate(false)
case <-ctx.Done():
return nil
}
}
}
// CheckCertificate checks the certificate to be valid, renews it if it is
// not and runs the after check functions.
func (renewer *Renewer) checkCertificate(wasTriggered bool) error {
if renewer == nil {
return errors.Errorf("invalid nil renewer")
}
renewer.logger.Info("checking certificate")
isValid, certificate, err := renewer.verifyCertificate()
if err != nil {
renewer.logger.Error(err, "verifying certificate failed")
}
var wasRenewed bool
if isValid {
renewer.logger.Info("certificate is valid")
} else {
renewer.logger.Info("certificate is invalid")
certificate, err = renewer.renewCertificate()
if err != nil {
renewer.logger.Error(err, "renewing certificate failed")
}
wasRenewed = true
}
for _, afterCheckFunction := range renewer.afterCheckFunctions {
err = afterCheckFunction(certificate, wasRenewed || wasTriggered)
if err != nil {
renewer.logger.Error(err, "running after check function failed")
}
}
return nil
}
// renewCertificate generates and returns a new certificate for the stored DNS
// names and writes them to the stored directory path.
func (renewer *Renewer) renewCertificate() (*Certificate, error) {
if renewer == nil {
return nil, errors.Errorf("invalid nil renewer")
}
renewer.logger.Info("renewing certificate")
certificate, err := NewCertificate(renewer.dnsNames)
if err != nil {
return nil, errors.WrapWithDetails(
err,
"creating new certificate for DNS names failed",
"dnsNames", renewer.dnsNames,
)
}
err = certificate.Write(renewer.certificateDirectoryPath)
if err != nil {
return nil, errors.WrapWithDetails(
err,
"writing renewed certificate to directory failed",
"directoryPath", renewer.certificateDirectoryPath,
)
}
return certificate, nil
}
// verifyCertificate verifies whether the underlying certificate is still valid.
func (renewer *Renewer) verifyCertificate() (isValid bool, certificate *Certificate, err error) {
if renewer == nil {
return false, nil, errors.Errorf("invalid nil renewer")
}
renewer.logger.Info("verifying certificate")
certificate, err = NewCertificateFromDirectory(renewer.certificateDirectoryPath)
if err != nil {
return false, nil, errors.WrapWithDetails(
err,
"loading certificate from directory failed",
"directoryPath", renewer.certificateDirectoryPath,
)
}
renewer.logger.Info("verifying certificate")
dnsNames := renewer.dnsNames
if len(dnsNames) == 0 {
dnsNames = append(dnsNames, "")
}
isValid = true
for _, dnsName := range dnsNames {
isValid = isValid && certificate.Verify(dnsName, time.Now().AddDate(0, 6, 0))
if !isValid {
break
}
}
return isValid, certificate, nil
}
// WithAfterCheckFunctions adds appends the specified functions to the existing
// after check function chain.
func (renewer *Renewer) WithAfterCheckFunctions(afterCheckFunctions ...AfterCheckFunctionType) {
if renewer == nil {
return
}
renewer.afterCheckFunctions = append(renewer.afterCheckFunctions, afterCheckFunctions...)
}
// WithDNSNames sets the DNS names used by the renewer in the certificate.
func (renewer *Renewer) WithDNSNames(dnsNames ...string) {
if renewer == nil {
return
}
renewer.dnsNames = dnsNames
}