fix(delivery): use podman unshare for rootless volume population

pkg/agent/delivery/local_docker.go

@@ -149,6 +149,10 @@ func (d *LocalDockerDelivery) populateVolumeDirectCopy(
 	volumeName string,
 	data []byte,
 ) error {
+	if d.isRootlessPodman(ctx) {
+		return d.populateVolumeUnshare(ctx, volumeName, data)
+	}
+
 	mountpoint, err := d.volumeMountpoint(ctx, volumeName)
 	if err != nil {
 		return fmt.Errorf("inspect volume mountpoint: %w", err)
@@ -167,6 +171,28 @@ func (d *LocalDockerDelivery) populateVolumeDirectCopy(
 	return nil
 }
 
+func (d *LocalDockerDelivery) populateVolumeUnshare(
+	ctx context.Context,
+	volumeName string,
+	data []byte,
+) error {
+	mountpoint, err := d.volumeMountpoint(ctx, volumeName)
+	if err != nil {
+		return fmt.Errorf("inspect volume mountpoint: %w", err)
+	}
+
+	destPath := filepath.Join(mountpoint, binaryName())
+
+	cmd := d.cmd(ctx, "unshare", "sh", "-c", `cat > "$1" && chmod 755 "$1"`, "--", destPath)
+	cmd.Stdin = bytes.NewReader(data)
+
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("podman unshare write: %s: %w", string(out), err)
+	}
+	return nil
+}
+
 func (d *LocalDockerDelivery) volumeMountpoint(
 	ctx context.Context,
 	volumeName string,
@@ -191,6 +217,25 @@ func (d *LocalDockerDelivery) removeVolume(ctx context.Context, workspaceID stri
 	return nil
 }
 
+func (d *LocalDockerDelivery) isPodman(ctx context.Context) bool {
+	out, err := d.cmd(ctx, "--version").CombinedOutput()
+	if err != nil {
+		return false
+	}
+	return strings.Contains(string(out), "podman")
+}
+
+func (d *LocalDockerDelivery) isRootlessPodman(ctx context.Context) bool {
+	if !d.isPodman(ctx) {
+		return false
+	}
+	out, err := d.cmd(ctx, "info", "--format", "{{.Host.Security.Rootless}}").CombinedOutput()
+	if err != nil {
+		return false
+	}
+	return strings.TrimSpace(string(out)) == "true"
+}
+
 func (d *LocalDockerDelivery) cmd(ctx context.Context, args ...string) *exec.Cmd {
 	// #nosec G204 -- args are constructed internally, not from user input
 	cmd := exec.CommandContext(ctx, d.dockerCommand(), args...)

pkg/agent/delivery/local_docker_test.go

@@ -124,3 +124,142 @@ func TestPopulateVolume_FallbackToDirectCopy(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, os.FileMode(0o755), info.Mode().Perm())
 }
+
+func TestIsPodman_Docker(t *testing.T) {
+	tmpDir := t.TempDir()
+	scriptPath := filepath.Join(tmpDir, "fake-docker.sh")
+	script := "#!/bin/sh\necho 'Docker version 24.0.7, build afdd53b'\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+	assert.False(t, d.isPodman(context.Background()))
+}
+
+func TestIsPodman_Podman(t *testing.T) {
+	tmpDir := t.TempDir()
+	scriptPath := filepath.Join(tmpDir, "fake-podman.sh")
+	script := "#!/bin/sh\necho 'podman version 4.9.3'\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+	assert.True(t, d.isPodman(context.Background()))
+}
+
+func TestIsRootlessPodman_DockerRuntime(t *testing.T) {
+	tmpDir := t.TempDir()
+	scriptPath := filepath.Join(tmpDir, "fake-docker.sh")
+	script := "#!/bin/sh\necho 'Docker version 24.0.7, build afdd53b'\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+	assert.False(t, d.isRootlessPodman(context.Background()))
+}
+
+func TestIsRootlessPodman_PodmanRootful(t *testing.T) {
+	tmpDir := t.TempDir()
+	scriptPath := filepath.Join(tmpDir, "fake-podman.sh")
+	script := "#!/bin/sh\n" +
+		"case \"$1\" in\n" +
+		"  --version) echo 'podman version 4.9.3' ;;\n" +
+		"  info) echo 'false' ;;\n" +
+		"  *) exit 1 ;;\n" +
+		"esac\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+	assert.False(t, d.isRootlessPodman(context.Background()))
+}
+
+func TestIsRootlessPodman_PodmanRootless(t *testing.T) {
+	tmpDir := t.TempDir()
+	scriptPath := filepath.Join(tmpDir, "fake-podman.sh")
+	script := "#!/bin/sh\n" +
+		"case \"$1\" in\n" +
+		"  --version) echo 'podman version 4.9.3' ;;\n" +
+		"  info) echo 'true' ;;\n" +
+		"  *) exit 1 ;;\n" +
+		"esac\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+	assert.True(t, d.isRootlessPodman(context.Background()))
+}
+
+func TestPopulateVolumeDirectCopy_RootlessPodman_UsesUnshare(t *testing.T) {
+	tmpDir := t.TempDir()
+	mountDir := filepath.Join(tmpDir, "mount")
+	require.NoError(t, os.MkdirAll(mountDir, 0o750))
+
+	scriptPath := filepath.Join(tmpDir, "fake-podman.sh")
+	script := "#!/bin/sh\n" +
+		"case \"$1\" in\n" +
+		"  --version) echo 'podman version 4.9.3' ;;\n" +
+		"  info) echo 'true' ;;\n" +
+		"  volume) echo '" + mountDir + "' ;;\n" +
+		"  unshare) shift; exec \"$@\" ;;\n" +
+		"  *) exit 1 ;;\n" +
+		"esac\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	binaryContent := []byte("fake-agent-binary-rootless")
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+
+	err := d.populateVolumeDirectCopy(context.Background(), "test-vol", binaryContent)
+	require.NoError(t, err)
+
+	destPath := filepath.Join(mountDir, binaryName())
+	data, err := os.ReadFile(destPath) //nolint:gosec // test reads from a temp directory we control
+	require.NoError(t, err)
+	assert.Equal(t, binaryContent, data)
+
+	info, err := os.Stat(destPath)
+	require.NoError(t, err)
+	assert.Equal(t, os.FileMode(0o755), info.Mode().Perm())
+}
+
+func TestPopulateVolumeDirectCopy_Docker_SkipsUnshare(t *testing.T) {
+	tmpDir := t.TempDir()
+	mountDir := filepath.Join(tmpDir, "mount")
+	require.NoError(t, os.MkdirAll(mountDir, 0o750))
+
+	scriptPath := filepath.Join(tmpDir, "fake-docker.sh")
+	script := "#!/bin/sh\n" +
+		"case \"$1\" in\n" +
+		"  --version) echo 'Docker version 24.0.7, build afdd53b' ;;\n" +
+		"  volume) echo '" + mountDir + "' ;;\n" +
+		"  unshare) echo 'unshare should not be called' >&2; exit 1 ;;\n" +
+		"  *) exit 1 ;;\n" +
+		"esac\n"
+	require.NoError(t, os.WriteFile(scriptPath, []byte(script), 0o600))
+	// #nosec G302 -- test script must be executable
+	require.NoError(t, os.Chmod(scriptPath, 0o755))
+
+	binaryContent := []byte("fake-agent-binary-docker")
+
+	d := &LocalDockerDelivery{DockerCommand: scriptPath}
+
+	err := d.populateVolumeDirectCopy(context.Background(), "test-vol", binaryContent)
+	require.NoError(t, err)
+
+	destPath := filepath.Join(mountDir, binaryName())
+	data, err := os.ReadFile(destPath) //nolint:gosec // test reads from a temp directory we control
+	require.NoError(t, err)
+	assert.Equal(t, binaryContent, data)
+
+	info, err := os.Stat(destPath)
+	require.NoError(t, err)
+	assert.Equal(t, os.FileMode(0o755), info.Mode().Perm())
+}