Add calendar/address-book sharing backend

Introduce internal/db, a small SQLite-backed store (pure-Go modernc.org/sqlite, no CGO) at <data_dir>/nidus.db holding calendar_shares and addressbook_shares grant tables (owner, resource name, shared-with user, read/write permission). This is the first step towards user management and a web UI: a real datastore that a future admin CLI/UI can build on, instead of the static config.yaml. Wire sharing into the CalDAV/CardDAV backends: - ListCalendars/ListAddressBooks now also include resources shared with the requesting user, exposed under the synthetic local name "<owner>~<name>" in the grantee's own home-set — no separate account, no data copying, the object still physically lives under the owner's store.Store namespace. - All read paths (Get/List/QueryCalendarObjects, address book equivalents) resolve the synthetic name back to (owner, real name) and require any share (read or write) to exist. - All write paths (Put/Delete object, DeleteCalendar/AddressBook) additionally require a write-permission share; read-only shares get a 403 Forbidden. - CreateCalendar/CreateAddressBook remain scoped to the acting user's own namespace — sharing an existing collection is done via ShareCalendar/ ShareAddressBook, not by creating one directly in someone else's name. Add internal/db/shares_test.go (grant/lookup/update/unshare/list semantics) and internal/{caldav,carddav}/backend_test.go (shared calendar/address book visibility, write permission enforcement, unauthorized access rejection). Update README (features, new "Sharing calendars and address books" section, project layout, dependencies) and copilot-instructions.md to document the new package and sharing model. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-08-18 20:10:31 +02:00
parent 21bac66b07
commit daa51d62b1
12 changed files with 1041 additions and 59 deletions
@@ -14,24 +14,34 @@ import (
 	"github.com/emersion/go-webdav/caldav"
 	"github.com/yourusername/caldav-server/internal/auth"
 	"github.com/yourusername/caldav-server/internal/config"
+	"github.com/yourusername/caldav-server/internal/db"
 	"github.com/yourusername/caldav-server/internal/store"
 )

+// sharedNameSep separates the owner from the calendar name in the
+// synthetic name used for calendars shared with another user, e.g.
+// "alice~work" for alice's "work" calendar as seen by whoever it was
+// shared with. It must not collide with characters allowed in real
+// calendar names (validated wherever calendar names are taken as input).
+const sharedNameSep = "~"
+
 // Backend implements caldav.Backend using a filesystem store.
 type Backend struct {
 	cfg    *config.Config
 	store  *store.Store
+	dbase  *db.DB // may be nil if sharing is not configured
 	logger *slog.Logger
 }

-// NewBackend creates a CalDAV backend.
-func NewBackend(cfg *config.Config, st *store.Store, logger *slog.Logger) *Backend {
-	return &Backend{cfg: cfg, store: st, logger: logger}
+// NewBackend creates a CalDAV backend. dbase may be nil, in which case
+// calendar sharing is disabled (only a user's own calendars are visible).
+func NewBackend(cfg *config.Config, st *store.Store, dbase *db.DB, logger *slog.Logger) *Backend {
+	return &Backend{cfg: cfg, store: st, dbase: dbase, logger: logger}
 }

 // NewHandler returns an http.Handler for the /cal/ prefix.
-func NewHandler(cfg *config.Config, st *store.Store, logger *slog.Logger) http.Handler {
-	b := NewBackend(cfg, st, logger)
+func NewHandler(cfg *config.Config, st *store.Store, dbase *db.DB, logger *slog.Logger) http.Handler {
+	b := NewBackend(cfg, st, dbase, logger)
 	return &caldav.Handler{Backend: b}
 }

@@ -74,7 +84,7 @@ func (b *Backend) ListCalendars(ctx context.Context) ([]caldav.Calendar, error)
 			b.logger.Warn("ensuring calendar directory", "calendar", name, "error", err)
 			continue
 		}
-		cals = append(cals, b.calendarMeta(p.Username, name))
+		cals = append(cals, b.calendarMeta(p.Username, name, name))
 	}

 	// Also include any extra calendars that exist on disk but aren't in config
@@ -86,7 +96,22 @@ func (b *Backend) ListCalendars(ctx context.Context) ([]caldav.Calendar, error)
 	for _, dir := range disk {
 		if strings.HasPrefix(dir, "cal-") && !configured[dir] {
 			name := strings.TrimPrefix(dir, "cal-")
-			cals = append(cals, b.calendarMeta(p.Username, name))
+			cals = append(cals, b.calendarMeta(p.Username, name, name))
+		}
+	}
+
+	// Include calendars other users have shared with this one.
+	if b.dbase != nil {
+		shares, err := b.dbase.CalendarsSharedWith(p.Username)
+		if err != nil {
+			b.logger.Warn("listing shared calendars", "error", err)
+		}
+		for _, sh := range shares {
+			if _, err := b.store.GetCollection(sh.Owner, "cal-"+sh.CalendarName); err != nil {
+				continue // owner's calendar no longer exists
+			}
+			localName := sharedCalendarName(sh.Owner, sh.CalendarName)
+			cals = append(cals, b.calendarMeta(sh.Owner, sh.CalendarName, localName))
 		}
 	}

@@ -94,24 +119,32 @@ func (b *Backend) ListCalendars(ctx context.Context) ([]caldav.Calendar, error)
 }

 func (b *Backend) GetCalendar(ctx context.Context, calPath string) (*caldav.Calendar, error) {
-	user, name, err := b.parseCalPath(ctx, calPath)
+	requester, localName, err := b.parseCalPath(ctx, calPath)
 	if err != nil {
 		return nil, err
 	}
-	if _, err := b.store.GetCollection(user, "cal-"+name); err != nil {
+	owner, realName, _, err := b.resolveCalendar(requester, localName, false)
+	if err != nil {
+		return nil, err
+	}
+	if _, err := b.store.GetCollection(owner, "cal-"+realName); err != nil {
 		return nil, webdav.NewHTTPError(http.StatusNotFound, err)
 	}
-	cal := b.calendarMeta(user, name)
+	cal := b.calendarMeta(owner, realName, localName)
 	return &cal, nil
 }

 func (b *Backend) GetCalendarObject(ctx context.Context, objPath string, req *caldav.CalendarCompRequest) (*caldav.CalendarObject, error) {
-	user, calName, objID, err := b.parseObjPath(ctx, objPath)
+	requester, localName, objID, err := b.parseObjPath(ctx, objPath)
+	if err != nil {
+		return nil, err
+	}
+	owner, realName, _, err := b.resolveCalendar(requester, localName, false)
 	if err != nil {
 		return nil, err
 	}

-	data, err := b.store.GetObject(user, "cal-"+calName, objID)
+	data, err := b.store.GetObject(owner, "cal-"+realName, objID)
 	if err != nil {
 		return nil, webdav.NewHTTPError(http.StatusNotFound, err)
 	}
@@ -120,23 +153,27 @@ func (b *Backend) GetCalendarObject(ctx context.Context, objPath string, req *ca
 }

 func (b *Backend) ListCalendarObjects(ctx context.Context, calPath string, req *caldav.CalendarCompRequest) ([]caldav.CalendarObject, error) {
-	user, calName, err := b.parseCalPath(ctx, calPath)
+	requester, localName, err := b.parseCalPath(ctx, calPath)
+	if err != nil {
+		return nil, err
+	}
+	owner, realName, _, err := b.resolveCalendar(requester, localName, false)
 	if err != nil {
 		return nil, err
 	}

-	ids, err := b.store.ListObjects(user, "cal-"+calName)
+	ids, err := b.store.ListObjects(owner, "cal-"+realName)
 	if err != nil {
 		return nil, err
 	}

 	var objs []caldav.CalendarObject
 	for _, id := range ids {
-		data, err := b.store.GetObject(user, "cal-"+calName, id)
+		data, err := b.store.GetObject(owner, "cal-"+realName, id)
 		if err != nil {
 			continue
 		}
-		obj, err := b.decodeObject(calObjectPath(calName, id), data)
+		obj, err := b.decodeObject(calObjectPath(localName, id), data)
 		if err != nil {
 			b.logger.Warn("decoding calendar object", "id", id, "error", err)
 			continue
@@ -160,21 +197,32 @@ func (b *Backend) CreateCalendar(ctx context.Context, calendar *caldav.Calendar)
 	if p == nil {
 		return webdav.NewHTTPError(http.StatusUnauthorized, fmt.Errorf("not authenticated"))
 	}
-	// Derive collection name from the trailing path segment.
+	// Derive collection name from the trailing path segment. Calendars are
+	// always created under the acting user's own namespace — sharing an
+	// existing calendar is done via ShareCalendar, not by creating one
+	// directly in someone else's name.
 	name := path.Base(strings.TrimSuffix(calendar.Path, "/"))
 	return b.store.EnsureCollection(p.Username, "cal-"+name)
 }

 func (b *Backend) DeleteCalendar(ctx context.Context, calPath string) error {
-	user, name, err := b.parseCalPath(ctx, calPath)
+	requester, localName, err := b.parseCalPath(ctx, calPath)
 	if err != nil {
 		return err
 	}
-	return b.store.DeleteCollection(user, "cal-"+name)
+	owner, realName, _, err := b.resolveCalendar(requester, localName, true)
+	if err != nil {
+		return err
+	}
+	return b.store.DeleteCollection(owner, "cal-"+realName)
 }

 func (b *Backend) PutCalendarObject(ctx context.Context, objPath string, calendar *ical.Calendar, opts *caldav.PutCalendarObjectOptions) (*caldav.CalendarObject, error) {
-	user, calName, objID, err := b.parseObjPath(ctx, objPath)
+	requester, localName, objID, err := b.parseObjPath(ctx, objPath)
+	if err != nil {
+		return nil, err
+	}
+	owner, realName, _, err := b.resolveCalendar(requester, localName, true)
 	if err != nil {
 		return nil, err
 	}
@@ -186,7 +234,7 @@ func (b *Backend) PutCalendarObject(ctx context.Context, objPath string, calenda
 	}

 	data := []byte(buf.String())
-	if err := b.store.PutObject(user, "cal-"+calName, objID, data); err != nil {
+	if err := b.store.PutObject(owner, "cal-"+realName, objID, data); err != nil {
 		return nil, fmt.Errorf("storing calendar object: %w", err)
 	}

@@ -194,11 +242,15 @@ func (b *Backend) PutCalendarObject(ctx context.Context, objPath string, calenda
 }

 func (b *Backend) DeleteCalendarObject(ctx context.Context, objPath string) error {
-	user, calName, objID, err := b.parseObjPath(ctx, objPath)
+	requester, localName, objID, err := b.parseObjPath(ctx, objPath)
 	if err != nil {
 		return err
 	}
-	if err := b.store.DeleteObject(user, "cal-"+calName, objID); err != nil {
+	owner, realName, _, err := b.resolveCalendar(requester, localName, true)
+	if err != nil {
+		return err
+	}
+	if err := b.store.DeleteObject(owner, "cal-"+realName, objID); err != nil {
 		return webdav.NewHTTPError(http.StatusNotFound, err)
 	}
 	return nil
@@ -206,11 +258,44 @@ func (b *Backend) DeleteCalendarObject(ctx context.Context, objPath string) erro

 // -------- helpers --------

-func (b *Backend) calendarMeta(user, name string) caldav.Calendar {
+// sharedCalendarName builds the synthetic local name a shared calendar is
+// exposed under to the user it was shared with.
+func sharedCalendarName(owner, calName string) string {
+	return owner + sharedNameSep + calName
+}
+
+// resolveCalendar maps a local calendar name (as seen in a URL path by
+// requester) to its real owner and on-disk name, checking permissions
+// along the way. If localName contains sharedNameSep, it's treated as a
+// reference to another user's calendar and looked up in the shares table;
+// otherwise it's assumed to be one of requester's own calendars.
+//
+// If requireWrite is true, a share must grant PermWrite or this returns a
+// 403 Forbidden error. Owners always have full access to their own
+// calendars.
+func (b *Backend) resolveCalendar(requester, localName string, requireWrite bool) (owner, realName string, perm db.Permission, err error) {
+	if ownerName, calName, ok := strings.Cut(localName, sharedNameSep); ok {
+		if b.dbase == nil {
+			return "", "", "", webdav.NewHTTPError(http.StatusNotFound, fmt.Errorf("sharing not enabled"))
+		}
+		share, err := b.dbase.CalendarShareFor(ownerName, calName, requester)
+		if err != nil {
+			return "", "", "", webdav.NewHTTPError(http.StatusForbidden, fmt.Errorf("calendar not shared with you"))
+		}
+		if requireWrite && share.Permission != db.PermWrite {
+			return "", "", "", webdav.NewHTTPError(http.StatusForbidden, fmt.Errorf("read-only share"))
+		}
+		return ownerName, calName, share.Permission, nil
+	}
+	return requester, localName, db.PermWrite, nil
+}
+
+func (b *Backend) calendarMeta(owner, realName, localName string) caldav.Calendar {
+	desc := fmt.Sprintf("%s's %s calendar", owner, realName)
 	return caldav.Calendar{
-		Path:                  calHomePath() + name + "/",
-		Name:                  name,
-		Description:           fmt.Sprintf("%s's %s calendar", user, name),
+		Path:                  calHomePath() + localName + "/",
+		Name:                  localName,
+		Description:           desc,
 		SupportedComponentSet: []string{"VEVENT", "VTODO", "VJOURNAL"},
 		MaxResourceSize:       10 * 1024 * 1024, // 10 MiB
 	}
@@ -0,0 +1,144 @@
+package caldav
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log/slog"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	ical "github.com/emersion/go-ical"
+	"github.com/yourusername/caldav-server/internal/auth"
+	"github.com/yourusername/caldav-server/internal/config"
+	"github.com/yourusername/caldav-server/internal/db"
+	"github.com/yourusername/caldav-server/internal/store"
+)
+
+func newTestBackend(t *testing.T) (*Backend, *db.DB) {
+	t.Helper()
+	dir := t.TempDir()
+
+	st, err := store.NewStore(filepath.Join(dir, "data"))
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	dbase, err := db.Open(filepath.Join(dir, "test.db"))
+	if err != nil {
+		t.Fatalf("db.Open: %v", err)
+	}
+	t.Cleanup(func() { dbase.Close() })
+
+	cfg := &config.Config{
+		Users: map[string]config.UserConfig{
+			"alice": {Calendars: []string{"work"}},
+			"bob":   {Calendars: []string{"personal"}},
+		},
+	}
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	return NewBackend(cfg, st, dbase, logger), dbase
+}
+
+func ctxFor(username string) context.Context {
+	return auth.NewContext(context.Background(), &auth.Principal{Username: username})
+}
+
+// minimalEvent returns a minimal, valid VCALENDAR/VEVENT for use in tests.
+func minimalEvent() *ical.Calendar {
+	const raw = "BEGIN:VCALENDAR\r\n" +
+		"VERSION:2.0\r\n" +
+		"PRODID:-//nidus//test//EN\r\n" +
+		"BEGIN:VEVENT\r\n" +
+		"UID:event1@nidus.test\r\n" +
+		"DTSTAMP:20240101T000000Z\r\n" +
+		"DTSTART:20240101T100000Z\r\n" +
+		"SUMMARY:Test Event\r\n" +
+		"END:VEVENT\r\n" +
+		"END:VCALENDAR\r\n"
+	cal, err := ical.NewDecoder(strings.NewReader(raw)).Decode()
+	if err != nil {
+		panic(fmt.Sprintf("minimalEvent: %v", err))
+	}
+	return cal
+}
+
+func TestListCalendarsIncludesSharedCalendar(t *testing.T) {
+	b, dbase := newTestBackend(t)
+
+	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermRead); err != nil {
+		t.Fatalf("ShareCalendar: %v", err)
+	}
+	// The shared calendar must exist on disk for it to be listed; normally
+	// this happens when alice's own ListCalendars runs and ensures it.
+	if _, err := b.ListCalendars(ctxFor("alice")); err != nil {
+		t.Fatalf("ListCalendars(alice): %v", err)
+	}
+
+	cals, err := b.ListCalendars(ctxFor("bob"))
+	if err != nil {
+		t.Fatalf("ListCalendars: %v", err)
+	}
+
+	var found bool
+	wantName := sharedCalendarName("alice", "work")
+	for _, c := range cals {
+		if c.Name == wantName {
+			found = true
+		}
+	}
+	if !found {
+		t.Errorf("shared calendar %q not found in ListCalendars result: %+v", wantName, cals)
+	}
+}
+
+func TestSharedCalendarReadOnlyRejectsWrite(t *testing.T) {
+	b, dbase := newTestBackend(t)
+
+	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermRead); err != nil {
+		t.Fatalf("ShareCalendar: %v", err)
+	}
+
+	localName := sharedCalendarName("alice", "work")
+	objPath := calObjectPath(localName, "event1.ics")
+
+	_, err := b.PutCalendarObject(ctxFor("bob"), objPath, minimalEvent(), nil)
+	if err == nil {
+		t.Fatal("expected error writing to read-only shared calendar, got nil")
+	}
+}
+
+func TestSharedCalendarWriteAllowed(t *testing.T) {
+	b, dbase := newTestBackend(t)
+
+	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermWrite); err != nil {
+		t.Fatalf("ShareCalendar: %v", err)
+	}
+
+	localName := sharedCalendarName("alice", "work")
+	objPath := calObjectPath(localName, "event1.ics")
+
+	if _, err := b.PutCalendarObject(ctxFor("bob"), objPath, minimalEvent(), nil); err != nil {
+		t.Fatalf("PutCalendarObject with write share: %v", err)
+	}
+
+	// The object should now be visible under alice's own calendar too,
+	// since it's stored in her namespace.
+	obj, err := b.GetCalendarObject(ctxFor("alice"), calObjectPath("work", "event1.ics"), nil)
+	if err != nil {
+		t.Fatalf("GetCalendarObject as owner: %v", err)
+	}
+	if obj == nil {
+		t.Fatal("expected non-nil object")
+	}
+}
+
+func TestUnauthorizedUserCannotAccessUnsharedCalendar(t *testing.T) {
+	b, _ := newTestBackend(t)
+
+	localName := sharedCalendarName("alice", "work")
+	_, err := b.GetCalendar(ctxFor("bob"), calHomePath()+localName+"/")
+	if err == nil {
+		t.Fatal("expected error accessing unshared calendar, got nil")
+	}
+}