all: fix chlog, imp api

CHANGELOG.md

@@ -25,13 +25,16 @@ See also the [v0.107.54 GitHub milestone][ms-v0.107.54].
 NOTE: Add new changes BELOW THIS COMMENT.
 -->
 
+### Security
+
+- Incorrect handling of sensitive files permissions on Windows ([#7314]).
+
 ### Changed
 
 - Improved filtering performance ([#6818]).
 
 ### Fixed
 
-- Incorrect handling of sensitive files permissions on Windows ([#7314]).
 - Repetitive statistics log messages ([#7338]).
 - Custom client cache ([#7250]).
 - Missing runtime clients with information from the system hosts file on first

internal/aghos/permission.go

@@ -1,6 +1,9 @@
 package aghos
 
-import "io/fs"
+import (
+	"io/fs"
+	"os"
+)
 
 // TODO(e.burkov):  Add platform-independent tests.
 
@@ -28,6 +31,12 @@ func WriteFile(filename string, data []byte, perm fs.FileMode) (err error) {
 	return writeFile(filename, data, perm)
 }
 
+// OpenFile is an extension for [os.OpenFile] that properly handles Windows
+// access rights.
+func OpenFile(name string, flag int, perm fs.FileMode) (file *os.File, err error) {
+	return openFile(name, flag, perm)
+}
+
 // Stat is an extension for [os.Stat] that properly handles Windows access
 // rights.
 func Stat(name string) (fi fs.FileInfo, err error) {

internal/aghos/permission_unix.go

@@ -27,6 +27,13 @@ func writeFile(filename string, data []byte, perm fs.FileMode) (err error) {
 	return os.WriteFile(filename, data, perm)
 }
 
+// openFile is a Unix implementation of [OpenFile].
+func openFile(name string, flag int, perm fs.FileMode) (file *os.File, err error) {
+	// #nosec G304 -- This function simply wraps the [os.OpenFile] function, so
+	// the security concerns should be addressed to the [OpenFile] calls.
+	return os.OpenFile(name, flag, perm)
+}
+
 // stat is a Unix implementation of [Stat].
 func stat(name string) (fi os.FileInfo, err error) {
 	return os.Stat(name)

internal/aghos/permission_windows.go

@@ -180,7 +180,7 @@ func mkdirAll(path string, perm os.FileMode) (err error) {
 	parent, _ := filepath.Split(path)
 
 	err = os.MkdirAll(parent, perm)
-	if err != nil {
+	if err != nil && !errors.Is(err, os.ErrExist) {
 		return fmt.Errorf("creating parent directories: %w", err)
 	}
 
@@ -197,6 +197,26 @@ func writeFile(filename string, data []byte, perm os.FileMode) (err error) {
 	return chmod(filename, perm)
 }
 
+// openFile is a Windows implementation of [OpenFile].
+func openFile(name string, flag int, perm os.FileMode) (file *os.File, err error) {
+	// Only change permissions if the file not yet exists, but should be
+	// created.
+	if flag&os.O_CREATE != 0 {
+		return os.OpenFile(name, flag, perm)
+	}
+
+	_, err = stat(name)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			defer func() { err = errors.WithDeferred(err, chmod(name, perm)) }()
+		} else {
+			return nil, fmt.Errorf("getting file info: %w", err)
+		}
+	}
+
+	return os.OpenFile(name, flag, perm)
+}
+
 // newWellKnownTrustee returns a trustee for a well-known SID.
 func newWellKnownTrustee(stype windows.WELL_KNOWN_SID_TYPE) (t *windows.TRUSTEE, err error) {
 	sid, err := windows.CreateWellKnownSid(stype)
@@ -213,8 +233,8 @@ func newWellKnownTrustee(stype windows.WELL_KNOWN_SID_TYPE) (t *windows.TRUSTEE,
 // Constants reflecting the UNIX permission bits.
 const (
 	ownerWrite = 0b010_000_000
-	groupWrite = 0b000_100_000
-	worldWrite = 0b000_000_100
+	groupWrite = 0b000_010_000
+	worldWrite = 0b000_000_010
 
 	ownerAll = 0b111_000_000
 	groupAll = 0b000_111_000

internal/querylog/qlogfile.go

@@ -57,6 +57,7 @@ type qLogFile struct {
 
 // newQLogFile initializes a new instance of the qLogFile.
 func newQLogFile(path string) (qf *qLogFile, err error) {
+	// Don't use [aghos.OpenFile] here, because the file is expected to exist.
 	f, err := os.OpenFile(path, os.O_RDONLY, aghos.DefaultPermFile)
 	if err != nil {
 		return nil, err

internal/querylog/querylogfile.go

@@ -71,7 +71,7 @@ func (l *queryLog) flushToFile(b *bytes.Buffer) (err error) {
 
 	filename := l.logFile
 
-	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, aghos.DefaultPermFile)
+	f, err := aghos.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, aghos.DefaultPermFile)
 	if err != nil {
 		return fmt.Errorf("creating file %q: %w", filename, err)
 	}

internal/stats/stats.go

@@ -384,7 +384,13 @@ func (s *StatsCtx) openDB() (err error) {
 	s.logger.Debug("opening database")
 
 	var db *bbolt.DB
-	db, err = bbolt.Open(s.filename, aghos.DefaultPermFile, nil)
+
+	opts := *bbolt.DefaultOptions
+	// Use the custom OpenFile function to properly handle access rights on
+	// Windows.
+	opts.OpenFile = aghos.OpenFile
+
+	db, err = bbolt.Open(s.filename, aghos.DefaultPermFile, &opts)
 	if err != nil {
 		if err.Error() == "invalid argument" {
 			const lines = `AdGuard Home cannot be initialized due to an incompatible file system.