constellation/internal/deploy/ssh/ssh.go

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package ssh
import (
"context"
"fmt"
"log"
"os"
"sync"
"github.com/edgelesssys/constellation/internal/deploy/user"
)
// UserKey describes an user that should be created with a corresponding public SSH key.
type UserKey struct {
Username string
PublicKey string
}
// SSHAccess 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 SSHAccess struct {
userManager user.LinuxUserManager
authorized map[string]bool
mux sync.Mutex
}
// NewSSHAccess creates a new SSHAccess.
func NewSSHAccess(userManager user.LinuxUserManager) *SSHAccess {
return &SSHAccess{
userManager: userManager,
mux: sync.Mutex{},
authorized: map[string]bool{},
}
}
// alreadyAuthorized checks if key was written to authorized keys before.
func (s *SSHAccess) alreadyAuthorized(sshKey UserKey) bool {
_, ok := s.authorized[fmt.Sprintf("%s:%s", sshKey.Username, sshKey.PublicKey)]
return ok
}
// rememberAuthorized marks this key as already written to authorized keys..
func (s *SSHAccess) rememberAuthorized(sshKey UserKey) {
s.authorized[fmt.Sprintf("%s:%s", sshKey.Username, sshKey.PublicKey)] = true
}
func (s *SSHAccess) DeploySSHAuthorizedKey(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
}
log.Printf("Trying to deploy ssh key for %s\n", sshKey.Username)
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)
authorized_keys_d := fmt.Sprintf("%s/authorized_keys.d", sshFolder)
if err := s.userManager.Fs.MkdirAll(authorized_keys_d, 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(authorized_keys_d, user.Uid, user.Gid); err != nil {
return err
}
authorizedKeysPath := fmt.Sprintf("%s/ssh-keys", authorized_keys_d)
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 %s\n", sshKey.PublicKey, sshKey.Username))
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)
log.Printf("Successfully authorized %s\n", sshKey.Username)
return nil
}