wrappers: update desktop helpers to support desktop IDs (canonical#14296

) {Ensure,Remove}SnapDesktopFiles are updated to support desktop file IDs. Snaps are allowed to have their desktop files copied without name mangling (with snap name prefix) if the file name is listed under desktop-file-ids attribute in their desktop interface declartion. This is needed to support desktop IDs detailed in SD170 spec. Signed-off-by: Zeyad Gouda <[email protected]>
pedronis · Sep 2, 2024 · 4159f95 · 4159f95
1 parent 01d54ca
commit 4159f95
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Showing 3 changed files with 379 additions and 34 deletions.
diff --git a/overlord/snapstate/snapstate_test.go b/overlord/snapstate/snapstate_test.go
@@ -9125,11 +9125,15 @@ Name=test
 Exec=test-snap
 `[1:]), 0o644), IsNil)
 
+	var mockOldDesktopFile = []byte(`
+[Desktop Entry]
+Name=old-content
+X-SnapInstanceName=test-snap`)
 	desktopFile := filepath.Join(dirs.SnapDesktopFilesDir, "test-snap_test-snap.desktop")
 	otherDesktopFile := filepath.Join(dirs.SnapDesktopFilesDir, "test-snap_other.desktop")
 	c.Assert(os.MkdirAll(dirs.SnapDesktopFilesDir, 0o755), IsNil)
-	c.Assert(os.WriteFile(desktopFile, []byte("old content"), 0o644), IsNil)
-	c.Assert(os.WriteFile(otherDesktopFile, []byte("other old content"), 0o644), IsNil)
+	c.Assert(os.WriteFile(desktopFile, mockOldDesktopFile, 0o644), IsNil)
+	c.Assert(os.WriteFile(otherDesktopFile, mockOldDesktopFile, 0o644), IsNil)
 
 	err := s.snapmgr.Ensure()
 	c.Assert(err, IsNil)

diff --git a/wrappers/desktop.go b/wrappers/desktop.go
@@ -22,6 +22,7 @@ package wrappers
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -247,7 +248,45 @@ func findDesktopFiles(rootDir string) ([]string, error) {
 	return desktopFiles, nil
 }
 
-func deriveDesktopFilesContent(s *snap.Info) (map[string]osutil.FileState, error) {
+// Note: explicitSnapDesktopFileIDs doesn't check if the desktop plug
+// is connected because the desktop-file-ids attribute is controlled
+// by an allow-installation rule.
+func explicitSnapDesktopFileIDs(s *snap.Info) (map[string]bool, error) {
+	var desktopPlug *snap.PlugInfo
+	for _, plug := range s.Plugs {
+		if plug.Interface == "desktop" {
+			desktopPlug = plug
+			break
+		}
+	}
+	if desktopPlug == nil {
+		return nil, nil
+	}
+
+	attrVal, exists := desktopPlug.Lookup("desktop-file-ids")
+	if !exists {
+		// desktop-file-ids attribute is optional
+		return nil, nil
+	}
+
+	// desktop-file-ids must be a list of strings
+	desktopFileIDs, ok := attrVal.([]interface{})
+	if !ok {
+		return nil, errors.New(`internal error: "desktop-file-ids" must be a list of strings`)
+	}
+
+	desktopFileIDsMap := make(map[string]bool, len(desktopFileIDs))
+	for _, val := range desktopFileIDs {
+		desktopFileID, ok := val.(string)
+		if !ok {
+			return nil, errors.New(`internal error: "desktop-file-ids" must be a list of strings`)
+		}
+		desktopFileIDsMap[desktopFileID] = true
+	}
+	return desktopFileIDsMap, nil
+}
+
+func deriveDesktopFilesContent(s *snap.Info, desktopFileIDs map[string]bool) (map[string]osutil.FileState, error) {
 	rootDir := filepath.Join(s.MountDir(), "meta", "gui")
 	desktopFiles, err := findDesktopFiles(rootDir)
 	if err != nil {
@@ -261,11 +300,16 @@ func deriveDesktopFilesContent(s *snap.Info) (map[string]osutil.FileState, error
 		if err != nil {
 			return nil, err
 		}
-		// FIXME: don't blindly use the snap desktop filename, mangle it
-		// but we can't just use the app name because a desktop file
-		// may call the same app with multiple parameters, e.g.
-		// --create-new, --open-existing etc
-		base = fmt.Sprintf("%s_%s", s.DesktopPrefix(), base)
+		// Don't mangle desktop files if listed under desktop-file-ids attribute
+		// XXX: Do we want to fail if a desktop-file-ids entry doesn't
+		// have a corresponding file?
+		if !desktopFileIDs[strings.TrimSuffix(base, ".desktop")] {
+			// FIXME: don't blindly use the snap desktop filename, mangle it
+			// but we can't just use the app name because a desktop file
+			// may call the same app with multiple parameters, e.g.
+			// --create-new, --open-existing etc
+			base = fmt.Sprintf("%s_%s", s.DesktopPrefix(), base)
+		}
 		installedDesktopFileName := filepath.Join(dirs.SnapDesktopFilesDir, base)
 		fileContent = sanitizeDesktopFile(s, installedDesktopFileName, fileContent)
 		content[base] = &osutil.MemoryFileState{
@@ -276,6 +320,60 @@ func deriveDesktopFilesContent(s *snap.Info) (map[string]osutil.FileState, error
 	return content, nil
 }
 
+// TODO: Merge desktop file helpers into desktop/desktopentry package
+func snapInstanceNameFromDesktopFile(desktopFile string) (string, error) {
+	file, err := os.Open(desktopFile)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for i := 0; scanner.Scan(); i++ {
+		bline := scanner.Text()
+		if !strings.HasPrefix(bline, "X-SnapInstanceName=") {
+			continue
+		}
+		return strings.TrimPrefix(bline, "X-SnapInstanceName="), nil
+	}
+
+	return "", fmt.Errorf("cannot find X-SnapInstanceName entry in %q", desktopFile)
+}
+
+// forAllDesktopFiles loops over all installed desktop files under
+// dirs.SnapDesktopFilesDir.
+//
+// Only the desktop file base and parsed instance name is passed the callback
+// function.
+func forAllDesktopFiles(cb func(base, instanceName string) error) error {
+	installedDesktopFiles, err := findDesktopFiles(dirs.SnapDesktopFilesDir)
+	if err != nil {
+		return err
+	}
+
+	for _, desktopFile := range installedDesktopFiles {
+		instanceName, err := snapInstanceNameFromDesktopFile(desktopFile)
+		if err != nil {
+			// cannot read instance name from desktop file, ignore
+			logger.Noticef("cannot read instance name: %s", err)
+			continue
+		}
+
+		base := filepath.Base(desktopFile)
+		if err := cb(base, instanceName); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func hasDesktopPrefix(s *snap.Info, desktopFile string) bool {
+	base := filepath.Base(desktopFile)
+	prefix := s.DesktopPrefix() + "_"
+	return strings.HasPrefix(base, prefix) && strings.HasSuffix(base, ".desktop")
+}
+
 // EnsureSnapDesktopFiles puts in place the desktop files for the applications from the snap.
 //
 // It also removes desktop files from the applications of the old snap revision to ensure
@@ -286,17 +384,42 @@ func EnsureSnapDesktopFiles(snaps []*snap.Info) error {
 	}
 
 	var updated []string
-	for _, s := range snaps {
-		if s == nil {
+	for _, info := range snaps {
+		if info == nil {
 			return fmt.Errorf("internal error: snap info cannot be nil")
 		}
-		content, err := deriveDesktopFilesContent(s)
+
+		desktopFileIDs, err := explicitSnapDesktopFileIDs(info)
 		if err != nil {
 			return err
 		}
+		desktopFilesGlobs := []string{fmt.Sprintf("%s_*.desktop", info.DesktopPrefix())}
+		for desktopFileID := range desktopFileIDs {
+			desktopFilesGlobs = append(desktopFilesGlobs, desktopFileID+".desktop")
+		}
+		content, err := deriveDesktopFilesContent(info, desktopFileIDs)
+		if err != nil {
+			return err
+		}
+
+		addGlobPatternAndConflictCheck := func(base, instanceName string) error {
+			// Check if a target desktop file belongs to another snap
+			_, hasTarget := content[base]
+			if hasTarget && instanceName != info.InstanceName() {
+				return fmt.Errorf("cannot install %q: %q already exists for another snap", base, filepath.Join(dirs.SnapDesktopFilesDir, base))
+			}
+			if instanceName == info.InstanceName() && !hasTarget && !hasDesktopPrefix(info, base) {
+				// An unmangled desktop file exists for the snap, add to glob
+				// patterns for removal
+				desktopFilesGlobs = append(desktopFilesGlobs, base)
+			}
+			return nil
+		}
+		if err := forAllDesktopFiles(addGlobPatternAndConflictCheck); err != nil {
+			return err
+		}
 
-		desktopFilesGlob := fmt.Sprintf("%s_*.desktop", s.DesktopPrefix())
-		changed, removed, err := osutil.EnsureDirState(dirs.SnapDesktopFilesDir, desktopFilesGlob, content)
+		changed, removed, err := osutil.EnsureDirStateGlobs(dirs.SnapDesktopFilesDir, desktopFilesGlobs, content)
 		if err != nil {
 			return err
 		}
@@ -318,8 +441,22 @@ func RemoveSnapDesktopFiles(s *snap.Info) error {
 		return nil
 	}
 
-	desktopFilesGlob := fmt.Sprintf("%s_*.desktop", s.DesktopPrefix())
-	_, removed, err := osutil.EnsureDirState(dirs.SnapDesktopFilesDir, desktopFilesGlob, nil)
+	desktopFilesGlobs := []string{fmt.Sprintf("%s_*.desktop", s.DesktopPrefix())}
+
+	addGlobPattern := func(base, instanceName string) error {
+		if instanceName == s.InstanceName() && !hasDesktopPrefix(s, base) {
+			// An unmangled desktop file exists for the snap, add to glob
+			// patterns for removal
+			desktopFilesGlobs = append(desktopFilesGlobs, base)
+		}
+
+		return nil
+	}
+	if err := forAllDesktopFiles(addGlobPattern); err != nil {
+		return err
+	}
+
+	_, removed, err := osutil.EnsureDirStateGlobs(dirs.SnapDesktopFilesDir, desktopFilesGlobs, nil)
 	if err != nil {
 		return err
 	}