ipn/ipnlocal: reenable profile tests on Windows

This fix does not seem ideal, but the test infrastructure using a local
goos doesn't seem to avoid all of the associated challenges, but is
somewhat deeply tied to the setup.

The core issue this addresses for now is that when run on Windows there
can be no code paths that attempt to use an invalid UID string, which on
Windows is described in [1].

For the goos="linux" tests, we now explicitly skip the affected
migration code if runtime.GOOS=="windows", and for the Windows test we
explicitly use the running users uid, rather than just the string
"user1". We also now make the case where a profile exists and has
already been migrated a non-error condition toward the outer API.

Updates #7876

[1] https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/manage/understand-security-identifiers

Signed-off-by: James Tucker <jftucker@gmail.com>

ipn/ipnlocal/profiles.go

@@ -22,6 +22,8 @@ import (
 	"tailscale.com/util/winutil"
 )
 
+var errAlreadyMigrated = errors.New("profile migration already completed")
+
 // profileManager is a wrapper around a StateStore that manages
 // multiple profiles and the current profile.
 type profileManager struct {
@@ -66,7 +68,7 @@ func (pm *profileManager) SetCurrentUserID(uid ipn.WindowsUserID) error {
 	b, err := pm.store.ReadState(ipn.CurrentProfileKey(string(uid)))
 	if err == ipn.ErrStateNotExist || len(b) == 0 {
 		if runtime.GOOS == "windows" {
-			if err := pm.migrateFromLegacyPrefs(); err != nil {
+			if err := pm.migrateFromLegacyPrefs(); err != nil && !errors.Is(err, errAlreadyMigrated) {
 				return err
 			}
 		} else {
@@ -544,7 +546,14 @@ func newProfileManagerWithGOOS(store ipn.StateStore, logf logger.Logf, goos stri
 		if err := pm.setPrefsLocked(prefs); err != nil {
 			return nil, err
 		}
-	} else if len(knownProfiles) == 0 && goos != "windows" {
+		// Most platform behavior is controlled by the goos parameter, however
+		// some behavior is implied by build tag and fails when run on Windows,
+		// so we explicitly avoid that behavior when running on Windows.
+		// Specifically this reaches down into legacy preference loading that is
+		// specialized by profiles_windows.go and fails in tests on an invalid
+		// uid passed in from the unix tests. The uid's used for Windows tests
+		// and runtime must be valid Windows security identifier structures.
+	} else if len(knownProfiles) == 0 && goos != "windows" && runtime.GOOS != "windows" {
 		// No known profiles, try a migration.
 		if err := pm.migrateFromLegacyPrefs(); err != nil {
 			return nil, err
@@ -562,7 +571,7 @@ func (pm *profileManager) migrateFromLegacyPrefs() error {
 	sentinel, prefs, err := pm.loadLegacyPrefs()
 	if err != nil {
 		metricMigrationError.Add(1)
-		return err
+		return fmt.Errorf("load legacy prefs: %w", err)
 	}
 	if err := pm.SetPrefs(prefs); err != nil {
 		metricMigrationError.Add(1)

ipn/ipnlocal/profiles_test.go

@@ -5,7 +5,7 @@ package ipnlocal
 
 import (
 	"fmt"
-	"runtime"
+	"os/user"
 	"strconv"
 	"testing"
 
@@ -18,9 +18,6 @@ import (
 )
 
 func TestProfileCurrentUserSwitch(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("TODO(#7876): test regressed on windows while CI was broken")
-	}
 	store := new(mem.Store)
 
 	pm, err := newProfileManagerWithGOOS(store, logger.Discard, "linux")
@@ -77,9 +74,6 @@ func TestProfileCurrentUserSwitch(t *testing.T) {
 }
 
 func TestProfileList(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("TODO(#7876): test regressed on windows while CI was broken")
-	}
 	store := new(mem.Store)
 
 	pm, err := newProfileManagerWithGOOS(store, logger.Discard, "linux")
@@ -158,9 +152,6 @@ func TestProfileList(t *testing.T) {
 
 // TestProfileManagement tests creating, loading, and switching profiles.
 func TestProfileManagement(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("TODO(#7876): test regressed on windows while CI was broken")
-	}
 	store := new(mem.Store)
 
 	pm, err := newProfileManagerWithGOOS(store, logger.Discard, "linux")
@@ -312,10 +303,11 @@ func TestProfileManagement(t *testing.T) {
 // TestProfileManagementWindows tests going into and out of Unattended mode on
 // Windows.
 func TestProfileManagementWindows(t *testing.T) {
-
-	if runtime.GOOS == "windows" {
-		t.Skip("TODO(#7876): test regressed on windows while CI was broken")
+	u, err := user.Current()
+	if err != nil {
+		t.Fatal(err)
 	}
+	uid := ipn.WindowsUserID(u.Uid)
 
 	store := new(mem.Store)
 
@@ -365,8 +357,8 @@ func TestProfileManagementWindows(t *testing.T) {
 
 	{
 		t.Logf("Set user1 as logged in user")
-		if err := pm.SetCurrentUserID("user1"); err != nil {
-			t.Fatal(err)
+		if err := pm.SetCurrentUserID(uid); err != nil {
+			t.Fatalf("can't set user id: %s", err)
 		}
 		checkProfiles(t)
 		t.Logf("Save prefs for user1")
@@ -401,7 +393,7 @@ func TestProfileManagementWindows(t *testing.T) {
 
 	{
 		t.Logf("Set user1 as current user")
-		if err := pm.SetCurrentUserID("user1"); err != nil {
+		if err := pm.SetCurrentUserID(uid); err != nil {
 			t.Fatal(err)
 		}
 		wantCurProfile = "test"
@@ -411,8 +403,8 @@ func TestProfileManagementWindows(t *testing.T) {
 		t.Logf("set unattended mode")
 		wantProfiles["test"] = setPrefs(t, "test", true)
 	}
-	if pm.CurrentUserID() != "user1" {
-		t.Fatalf("CurrentUserID = %q; want %q", pm.CurrentUserID(), "user1")
+	if pm.CurrentUserID() != uid {
+		t.Fatalf("CurrentUserID = %q; want %q", pm.CurrentUserID(), uid)
 	}
 
 	// Recreate the profile manager to ensure that it starts with test profile.
@@ -421,7 +413,7 @@ func TestProfileManagementWindows(t *testing.T) {
 		t.Fatal(err)
 	}
 	checkProfiles(t)
-	if pm.CurrentUserID() != "user1" {
-		t.Fatalf("CurrentUserID = %q; want %q", pm.CurrentUserID(), "user1")
+	if pm.CurrentUserID() != uid {
+		t.Fatalf("CurrentUserID = %q; want %q", pm.CurrentUserID(), uid)
 	}
 }

ipn/ipnlocal/profiles_windows.go

@@ -6,6 +6,7 @@ package ipnlocal
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"os/user"
 	"path/filepath"
@@ -21,8 +22,6 @@ const (
 	legacyPrefsExt                   = ".conf"
 )
 
-var errAlreadyMigrated = errors.New("profile migration already completed")
-
 func legacyPrefsDir(uid ipn.WindowsUserID) (string, error) {
 	// TODO(aaron): Ideally we'd have the impersonation token for the pipe's
 	// client and use it to call SHGetKnownFolderPath, thus yielding the correct
@@ -56,6 +55,9 @@ func (pm *profileManager) loadLegacyPrefs() (string, ipn.PrefsView, error) {
 
 	prefsPath := filepath.Join(userLegacyPrefsDir, legacyPrefsFile+legacyPrefsExt)
 	prefs, err := ipn.LoadPrefs(prefsPath)
+	if errors.Is(err, fs.ErrNotExist) {
+		return "", ipn.PrefsView{}, errAlreadyMigrated
+	}
 	if err != nil {
 		return "", ipn.PrefsView{}, err
 	}