forked from TrueCloudLab/distribution
123 lines
3.5 KiB
Go
123 lines
3.5 KiB
Go
// Copyright 2022 Google LLC.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package cert contains certificate tools for Google API clients.
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// This package is intended to be used with crypto/tls.Config.GetClientCertificate.
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//
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// The certificates can be used to satisfy Google's Endpoint Validation.
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// See https://cloud.google.com/endpoint-verification/docs/overview
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//
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// This package is not intended for use by end developers. Use the
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// google.golang.org/api/option package to configure API clients.
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package cert
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import (
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"crypto/tls"
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"crypto/x509"
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"encoding/json"
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"errors"
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"fmt"
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"io/ioutil"
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"os"
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"os/exec"
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"os/user"
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"path/filepath"
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"sync"
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"time"
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)
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const (
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metadataPath = ".secureConnect"
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metadataFile = "context_aware_metadata.json"
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)
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type secureConnectSource struct {
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metadata secureConnectMetadata
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// Cache the cert to avoid executing helper command repeatedly.
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cachedCertMutex sync.Mutex
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cachedCert *tls.Certificate
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}
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type secureConnectMetadata struct {
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Cmd []string `json:"cert_provider_command"`
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}
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// NewSecureConnectSource creates a certificate source using
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// the Secure Connect Helper and its associated metadata file.
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//
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// The configFilePath points to the location of the context aware metadata file.
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// If configFilePath is empty, use the default context aware metadata location.
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func NewSecureConnectSource(configFilePath string) (Source, error) {
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if configFilePath == "" {
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user, err := user.Current()
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if err != nil {
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// Error locating the default config means Secure Connect is not supported.
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return nil, errSourceUnavailable
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}
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configFilePath = filepath.Join(user.HomeDir, metadataPath, metadataFile)
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}
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file, err := ioutil.ReadFile(configFilePath)
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if err != nil {
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if errors.Is(err, os.ErrNotExist) {
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// Config file missing means Secure Connect is not supported.
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return nil, errSourceUnavailable
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}
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return nil, err
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}
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var metadata secureConnectMetadata
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if err := json.Unmarshal(file, &metadata); err != nil {
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return nil, fmt.Errorf("cert: could not parse JSON in %q: %w", configFilePath, err)
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}
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if err := validateMetadata(metadata); err != nil {
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return nil, fmt.Errorf("cert: invalid config in %q: %w", configFilePath, err)
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}
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return (&secureConnectSource{
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metadata: metadata,
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}).getClientCertificate, nil
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}
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func validateMetadata(metadata secureConnectMetadata) error {
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if len(metadata.Cmd) == 0 {
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return errors.New("empty cert_provider_command")
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}
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return nil
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}
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func (s *secureConnectSource) getClientCertificate(info *tls.CertificateRequestInfo) (*tls.Certificate, error) {
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s.cachedCertMutex.Lock()
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defer s.cachedCertMutex.Unlock()
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if s.cachedCert != nil && !isCertificateExpired(s.cachedCert) {
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return s.cachedCert, nil
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}
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// Expand OS environment variables in the cert provider command such as "$HOME".
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for i := 0; i < len(s.metadata.Cmd); i++ {
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s.metadata.Cmd[i] = os.ExpandEnv(s.metadata.Cmd[i])
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}
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command := s.metadata.Cmd
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data, err := exec.Command(command[0], command[1:]...).Output()
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if err != nil {
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return nil, err
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}
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cert, err := tls.X509KeyPair(data, data)
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if err != nil {
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return nil, err
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}
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s.cachedCert = &cert
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return &cert, nil
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}
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// isCertificateExpired returns true if the given cert is expired or invalid.
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func isCertificateExpired(cert *tls.Certificate) bool {
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if len(cert.Certificate) == 0 {
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return true
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}
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parsed, err := x509.ParseCertificate(cert.Certificate[0])
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if err != nil {
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return true
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}
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return time.Now().After(parsed.NotAfter)
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}
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