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daemon: rewrite authsync + image seeding on ext4 toolkit

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ensureAuthorizedKeyOnWorkDisk and seedAuthorizedKeyOnExt4Image both
drove mount + sudo mkdir/chmod/chown/cat/install to patch
/.ssh/authorized_keys into a work disk or work-seed. Both now delegate
to a shared provisionAuthorizedKey helper that uses the ext4 toolkit
introduced in 7704396 — EnsureExt4RootPerms + MkdirExt4 +
Ext4PathExists/ReadExt4File + WriteExt4FileOwned. No mount, no sudo,
no host-path staging.

Drops ~10 sudo call sites from the VM create and image pull flows
and deletes the TestEnsureAuthorizedKeyOnWorkDiskRepairsNestedRootLayout
premise (flattenNestedWorkHome will disappear entirely in the next
commit — the no-seed path no longer copies /root, and the work-seed
path produces flat seeds).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Thales Maciel 2026-04-23 18:21:50 -03:00
parent 0e28504892
commit f0685366ec
No known key found for this signature in database
GPG key ID: 33112E6833C34679
3 changed files with 34 additions and 163 deletions
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54
internal/daemon/image_seed.go
View file

@ -3,13 +3,10 @@ package daemon
import (
"context"
"fmt"
"os"
"path/filepath"
"strings"
"banger/internal/guest"
"banger/internal/model"
"banger/internal/system"
)
func (s *ImageService) seedAuthorizedKeyOnExt4Image(ctx context.Context, imagePath string) (string, error) {
@ -24,56 +21,7 @@ func (s *ImageService) seedAuthorizedKeyOnExt4Image(ctx context.Context, imagePa
if err != nil {
return "", fmt.Errorf("derive authorized ssh key: %w", err)
}
mountDir, cleanup, err := system.MountTempDir(ctx, s.runner, imagePath, false)
if err != nil {
return "", err
}
defer cleanup()
if err := flattenNestedWorkHome(ctx, s.runner, mountDir); err != nil {
return "", err
}
// Same rationale as in ensureAuthorizedKeyOnWorkDisk — the seed's
// filesystem root becomes /root inside the guest, and sshd's
// StrictModes check walks its ownership and mode.
if err := normaliseHomeDirPerms(ctx, s.runner, mountDir); err != nil {
return "", err
}
sshDir := filepath.Join(mountDir, ".ssh")
if _, err := s.runner.RunSudo(ctx, "mkdir", "-p", sshDir); err != nil {
return "", err
}
if _, err := s.runner.RunSudo(ctx, "chmod", "700", sshDir); err != nil {
return "", err
}
if _, err := s.runner.RunSudo(ctx, "chown", "0:0", sshDir); err != nil {
return "", err
}
authorizedKeysPath := filepath.Join(sshDir, "authorized_keys")
existing, err := s.runner.RunSudo(ctx, "cat", authorizedKeysPath)
if err != nil {
existing = nil
}
merged := mergeAuthorizedKey(existing, publicKey)
tmpFile, err := os.CreateTemp("", "banger-image-authorized-keys-*")
if err != nil {
return "", err
}
tmpPath := tmpFile.Name()
if _, err := tmpFile.Write(merged); err != nil {
_ = tmpFile.Close()
_ = os.Remove(tmpPath)
return "", err
}
if err := tmpFile.Close(); err != nil {
_ = os.Remove(tmpPath)
return "", err
}
defer os.Remove(tmpPath)
if _, err := s.runner.RunSudo(ctx, "install", "-m", "600", tmpPath, authorizedKeysPath); err != nil {
if err := provisionAuthorizedKey(ctx, s.runner, imagePath, publicKey); err != nil {
return "", err
}
return fingerprint, nil

84
internal/daemon/vm_authsync.go
View file

@ -37,61 +37,12 @@ func (s *WorkspaceService) ensureAuthorizedKeyOnWorkDisk(ctx context.Context, vm
return fmt.Errorf("derive authorized ssh key: %w", err)
}
vmCreateStage(ctx, "prepare_work_disk", "provisioning SSH access on work disk")
workMount, cleanupWork, err := system.MountTempDir(ctx, s.runner, vm.Runtime.WorkDiskPath, false)
if err != nil {
return err
}
defer cleanupWork()
if err := flattenNestedWorkHome(ctx, s.runner, workMount); err != nil {
workDisk := vm.Runtime.WorkDiskPath
if err := provisionAuthorizedKey(ctx, s.runner, workDisk, publicKey); err != nil {
return err
}
// Normalise the work-disk filesystem root: inside the guest this
// mounts at /root, which sshd inspects when StrictModes is on (the
// default after the hardening drop-in). Any drift — owner != root,
// group/other-writable — would make sshd silently reject the key.
if err := normaliseHomeDirPerms(ctx, s.runner, workMount); err != nil {
return err
}
sshDir := filepath.Join(workMount, ".ssh")
if _, err := s.runner.RunSudo(ctx, "mkdir", "-p", sshDir); err != nil {
return err
}
if _, err := s.runner.RunSudo(ctx, "chmod", "700", sshDir); err != nil {
return err
}
if _, err := s.runner.RunSudo(ctx, "chown", "0:0", sshDir); err != nil {
return err
}
authorizedKeysPath := filepath.Join(sshDir, "authorized_keys")
existing, err := s.runner.RunSudo(ctx, "cat", authorizedKeysPath)
if err != nil {
existing = nil
}
merged := mergeAuthorizedKey(existing, publicKey)
tmpFile, err := os.CreateTemp("", "banger-authorized-keys-*")
if err != nil {
return err
}
tmpPath := tmpFile.Name()
if _, err := tmpFile.Write(merged); err != nil {
_ = tmpFile.Close()
_ = os.Remove(tmpPath)
return err
}
if err := tmpFile.Close(); err != nil {
_ = os.Remove(tmpPath)
return err
}
defer os.Remove(tmpPath)
if _, err := s.runner.RunSudo(ctx, "install", "-m", "600", tmpPath, authorizedKeysPath); err != nil {
return err
}
if prep.ClonedFromSeed && image.Managed {
vmCreateStage(ctx, "prepare_work_disk", "refreshing managed work seed")
if err := s.imageWorkSeed(ctx, image, fingerprint); err != nil {
@ -101,6 +52,37 @@ func (s *WorkspaceService) ensureAuthorizedKeyOnWorkDisk(ctx context.Context, vm
return nil
}
// provisionAuthorizedKey writes the managed SSH key into
// /.ssh/authorized_keys on an ext4 image via the sudoless toolkit.
// Shared between work-disk and image-seed paths — both need the same
// sequence: normalise fs-root perms, create /.ssh, merge against any
// existing authorized_keys, rewrite with root:root:0600.
//
// The fs root doubles as /root inside the guest, which sshd walks
// under StrictModes; forcing 0755 root:root here keeps a drifted
// seed image from silently rejecting the key at login time.
func provisionAuthorizedKey(ctx context.Context, runner system.CommandRunner, imagePath string, publicKey []byte) error {
if err := system.EnsureExt4RootPerms(ctx, runner, imagePath, 0o755, 0, 0); err != nil {
return err
}
if err := system.MkdirExt4(ctx, runner, imagePath, "/.ssh", 0o700, 0, 0); err != nil {
return err
}
var existing []byte
exists, err := system.Ext4PathExists(ctx, runner, imagePath, "/.ssh/authorized_keys")
if err != nil {
return err
}
if exists {
existing, err = system.ReadExt4File(ctx, runner, imagePath, "/.ssh/authorized_keys")
if err != nil {
return err
}
}
merged := mergeAuthorizedKey(existing, publicKey)
return system.WriteExt4FileOwned(ctx, runner, imagePath, "/.ssh/authorized_keys", 0o600, 0, 0, merged)
}
// normaliseHomeDirPerms forces the home-directory mount point to
// 0755 root:root. sshd's StrictModes (the default, re-enabled after
// banger stopped shipping "StrictModes no") rejects authorized_keys

59
internal/daemon/vm_test.go
View file

@ -847,65 +847,6 @@ func TestFlattenNestedWorkHomeCopiesEntriesIndividually(t *testing.T) {
runner.assertExhausted()
}
func TestEnsureAuthorizedKeyOnWorkDiskRepairsNestedRootLayout(t *testing.T) {
t.Parallel()
workDiskDir := t.TempDir()
nestedHome := filepath.Join(workDiskDir, "root")
if err := os.MkdirAll(filepath.Join(nestedHome, ".ssh"), 0o700); err != nil {
t.Fatalf("MkdirAll(.ssh): %v", err)
}
if err := os.WriteFile(filepath.Join(nestedHome, ".bashrc"), []byte("export TEST_PROMPT=1\n"), 0o644); err != nil {
t.Fatalf("WriteFile(.bashrc): %v", err)
}
existingKey := "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILEgacykey existing@test\n"
if err := os.WriteFile(filepath.Join(nestedHome, ".ssh", "authorized_keys"), []byte(existingKey), 0o600); err != nil {
t.Fatalf("WriteFile(authorized_keys): %v", err)
}
privateKey, err := rsa.GenerateKey(rand.Reader, 1024)
if err != nil {
t.Fatalf("GenerateKey: %v", err)
}
privateKeyPEM := pem.EncodeToMemory(&pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
})
sshKeyPath := filepath.Join(t.TempDir(), "id_rsa")
if err := os.WriteFile(sshKeyPath, privateKeyPEM, 0o600); err != nil {
t.Fatalf("WriteFile(private key): %v", err)
}
d := &Daemon{
runner: &filesystemRunner{t: t},
config: model.DaemonConfig{SSHKeyPath: sshKeyPath},
}
wireServices(d)
vm := testVM("seed-repair", "image-seed-repair", "172.16.0.61")
vm.Runtime.WorkDiskPath = workDiskDir
if err := d.ws.ensureAuthorizedKeyOnWorkDisk(context.Background(), &vm, model.Image{}, workDiskPreparation{}); err != nil {
t.Fatalf("ensureAuthorizedKeyOnWorkDisk: %v", err)
}
if _, err := os.Stat(filepath.Join(workDiskDir, "root")); !os.IsNotExist(err) {
t.Fatalf("nested root still exists: %v", err)
}
if _, err := os.Stat(filepath.Join(workDiskDir, ".bashrc")); err != nil {
t.Fatalf(".bashrc missing at top level: %v", err)
}
data, err := os.ReadFile(filepath.Join(workDiskDir, ".ssh", "authorized_keys"))
if err != nil {
t.Fatalf("ReadFile(authorized_keys): %v", err)
}
content := string(data)
if !strings.Contains(content, strings.TrimSpace(existingKey)) {
t.Fatalf("authorized_keys missing pre-existing key: %q", content)
}
if !strings.Contains(content, "ssh-rsa ") {
t.Fatalf("authorized_keys missing managed key: %q", content)
}
}
func TestEnsureGitIdentityOnWorkDiskCopiesHostGlobalIdentity(t *testing.T) {
if _, err := exec.LookPath("git"); err != nil {
t.Skip("git not installed")