constellation/internal/deploy/ssh/ssh.go
2022-09-22 09:10:19 +02:00

114 lines
3.4 KiB
Go

/*
Copyright (c) Edgeless Systems GmbH
SPDX-License-Identifier: AGPL-3.0-only
*/
package ssh
import (
"context"
"fmt"
"os"
"sync"
"github.com/edgelesssys/constellation/v2/internal/deploy/user"
"github.com/edgelesssys/constellation/v2/internal/logger"
"go.uber.org/zap"
)
// UserKey describes an user that should be created with a corresponding public SSH key.
type UserKey struct {
Username string
PublicKey string
}
// Access reads SSH public keys from a channel, creates the specified users if required and writes the public keys to the users authorized_keys file.
type Access struct {
log *logger.Logger
userManager user.LinuxUserManager
authorized map[UserKey]bool
mux sync.Mutex
}
// NewAccess creates a new Access.
func NewAccess(log *logger.Logger, userManager user.LinuxUserManager) *Access {
return &Access{
log: log,
userManager: userManager,
authorized: map[UserKey]bool{},
}
}
// alreadyAuthorized checks if key was written to authorized keys before.
func (s *Access) alreadyAuthorized(sshKey UserKey) bool {
_, ok := s.authorized[sshKey]
return ok
}
// rememberAuthorized marks this key as already written to authorized keys..
func (s *Access) rememberAuthorized(sshKey UserKey) {
s.authorized[sshKey] = true
}
// GetAuthorizedKeys returns a list of authorized keys for the specified user.
func (s *Access) GetAuthorizedKeys() []UserKey {
s.mux.Lock()
defer s.mux.Unlock()
var authorizedKeys []UserKey
for key := range s.authorized {
authorizedKeys = append(authorizedKeys, key)
}
return authorizedKeys
}
// DeployAuthorizedKey takes an user & public key pair, creates the user if required and deploy a SSH key for them.
func (s *Access) DeployAuthorizedKey(ctx context.Context, sshKey UserKey) error {
// allow only one thread to write to authorized keys, create users and update the authorized map at a time
s.mux.Lock()
defer s.mux.Unlock()
if s.alreadyAuthorized(sshKey) {
return nil
}
s.log.With(zap.String("username", sshKey.Username)).Infof("Trying to deploy ssh key for user")
user, err := s.userManager.EnsureLinuxUserExists(ctx, sshKey.Username)
if err != nil {
return err
}
// CoreOS uses https://github.com/coreos/ssh-key-dir to search for ssh keys in ~/.ssh/authorized_keys.d/*
sshFolder := fmt.Sprintf("%s/.ssh", user.Home)
authorizedKeysD := fmt.Sprintf("%s/authorized_keys.d", sshFolder)
if err := s.userManager.Fs.MkdirAll(authorizedKeysD, 0o700); err != nil {
return err
}
if err := s.userManager.Fs.Chown(sshFolder, user.UID, user.GID); err != nil {
return err
}
if err := s.userManager.Fs.Chown(authorizedKeysD, user.UID, user.GID); err != nil {
return err
}
authorizedKeysPath := fmt.Sprintf("%s/constellation-ssh-keys", authorizedKeysD)
authorizedKeysFile, err := s.userManager.Fs.OpenFile(authorizedKeysPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
if err != nil {
return err
}
_, err = authorizedKeysFile.WriteString(fmt.Sprintf("%s\n", sshKey.PublicKey))
if err != nil {
return err
}
if err := authorizedKeysFile.Close(); err != nil {
return err
}
if err := s.userManager.Fs.Chown(authorizedKeysPath, user.UID, user.GID); err != nil {
return err
}
if err := s.userManager.Fs.Chmod(authorizedKeysPath, 0o644); err != nil {
return err
}
s.rememberAuthorized(sshKey)
s.log.With(zap.String("username", sshKey.Username)).Infof("Successfully authorized user")
return nil
}