Pull request 2294: AGDNS-2455 Windows permissions

Closes #7314.

Squashed commit of the following:

commit f8b6ffeec2f0f96c947cf896c75d05efaca77caf
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Oct 29 14:14:41 2024 +0300

    all: fix chlog

commit 9417b7dc51
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 28 19:41:30 2024 +0300

    aghos: imp doc

commit b91f0e72a7
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 28 19:26:15 2024 +0300

    all: rm bin

commit 9008ee93b1
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 28 18:23:54 2024 +0300

    all: revert permcheck

commit bcc85d50f5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 28 17:48:55 2024 +0300

    all: use aghos more

commit 993e351712
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Oct 28 16:24:56 2024 +0300

    all: fix more bugs

commit a22b0d265e
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 18:30:52 2024 +0300

    all: fix bugs

commit a2309f812a
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 17:05:08 2024 +0300

    all: fix chlog, imp api

commit 42c3f8e91c
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 16:04:47 2024 +0300

    scripts: fix docs

commit 9e781ff18d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 16:03:19 2024 +0300

    scripts: imp docs

commit 1dbc784982
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 15:55:16 2024 +0300

    all: use new functions, add tests

commit dcbabaf4e3
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Oct 25 13:23:50 2024 +0300

    aghos: add stat

commit 72d7c0f881
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Oct 24 17:10:30 2024 +0300

    aghos: add windows functions

CHANGELOG.md

@@ -25,6 +25,10 @@ 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]).
@@ -38,6 +42,7 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 [#6818]: https://github.com/AdguardTeam/AdGuardHome/issues/6818
 [#7250]: https://github.com/AdguardTeam/AdGuardHome/issues/7250
+[#7314]: https://github.com/AdguardTeam/AdGuardHome/issues/7314
 [#7315]: https://github.com/AdguardTeam/AdGuardHome/issues/7315
 [#7338]: https://github.com/AdguardTeam/AdGuardHome/issues/7338
 

internal/aghos/permission.go

@@ -0,0 +1,50 @@
+package aghos
+
+import (
+	"io/fs"
+	"os"
+)
+
+// TODO(e.burkov):  Add platform-independent tests.
+
+// Chmod is an extension for [os.Chmod] that properly handles Windows access
+// rights.
+func Chmod(name string, perm fs.FileMode) (err error) {
+	return chmod(name, perm)
+}
+
+// Mkdir is an extension for [os.Mkdir] that properly handles Windows access
+// rights.
+func Mkdir(name string, perm fs.FileMode) (err error) {
+	return mkdir(name, perm)
+}
+
+// MkdirAll is an extension for [os.MkdirAll] that properly handles Windows
+// access rights.
+func MkdirAll(path string, perm fs.FileMode) (err error) {
+	return mkdirAll(path, perm)
+}
+
+// WriteFile is an extension for [os.WriteFile] that properly handles Windows
+// access rights.
+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.
+//
+// Note that on Windows the "other" permission bits combines the access rights
+// of any trustee that is neither the owner nor the owning group for the file.
+//
+// TODO(e.burkov):  Inspect the behavior for the World (everyone) well-known
+// SID and, perhaps, use it.
+func Stat(name string) (fi fs.FileInfo, err error) {
+	return stat(name)
+}

internal/aghos/permission_unix.go

@@ -0,0 +1,42 @@
+//go:build unix
+
+package aghos
+
+import (
+	"io/fs"
+	"os"
+
+	"github.com/google/renameio/v2/maybe"
+)
+
+// chmod is a Unix implementation of [Chmod].
+func chmod(name string, perm fs.FileMode) (err error) {
+	return os.Chmod(name, perm)
+}
+
+// mkdir is a Unix implementation of [Mkdir].
+func mkdir(name string, perm fs.FileMode) (err error) {
+	return os.Mkdir(name, perm)
+}
+
+// mkdirAll is a Unix implementation of [MkdirAll].
+func mkdirAll(path string, perm fs.FileMode) (err error) {
+	return os.MkdirAll(path, perm)
+}
+
+// writeFile is a Unix implementation of [WriteFile].
+func writeFile(filename string, data []byte, perm fs.FileMode) (err error) {
+	return maybe.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

@@ -0,0 +1,392 @@
+//go:build windows
+
+package aghos
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"unsafe"
+
+	"github.com/AdguardTeam/golibs/errors"
+	"golang.org/x/sys/windows"
+)
+
+// fileInfo is a Windows implementation of [fs.FileInfo], that contains the
+// filemode converted from the security descriptor.
+type fileInfo struct {
+	// fs.FileInfo is embedded to provide the default implementations and data
+	// successfully retrieved by [os.Stat].
+	fs.FileInfo
+
+	// mode is the file mode converted from the security descriptor.
+	mode fs.FileMode
+}
+
+// type check
+var _ fs.FileInfo = (*fileInfo)(nil)
+
+// Mode implements [fs.FileInfo.Mode] for [*fileInfo].
+func (fi *fileInfo) Mode() (mode fs.FileMode) { return fi.mode }
+
+// stat is a Windows implementation of [Stat].
+func stat(name string) (fi os.FileInfo, err error) {
+	absName, err := filepath.Abs(name)
+	if err != nil {
+		return nil, fmt.Errorf("computing absolute path: %w", err)
+	}
+
+	fi, err = os.Stat(absName)
+	if err != nil {
+		// Don't wrap the error, since it's informative enough as is.
+		return nil, err
+	}
+
+	dacl, owner, group, err := retrieveDACL(absName)
+	if err != nil {
+		// Don't wrap the error, since it's informative enough as is.
+		return nil, err
+	}
+
+	var ownerMask, groupMask, otherMask windows.ACCESS_MASK
+	for i := range uint32(dacl.AceCount) {
+		var ace *windows.ACCESS_ALLOWED_ACE
+		err = windows.GetAce(dacl, i, &ace)
+		if err != nil {
+			return nil, fmt.Errorf("getting access control entry at index %d: %w", i, err)
+		}
+
+		entrySid := (*windows.SID)(unsafe.Pointer(&ace.SidStart))
+		switch {
+		case entrySid.Equals(owner):
+			ownerMask |= ace.Mask
+		case entrySid.Equals(group):
+			groupMask |= ace.Mask
+		default:
+			otherMask |= ace.Mask
+		}
+	}
+
+	mode := fi.Mode()
+	perm := masksToPerm(ownerMask, groupMask, otherMask, mode.IsDir())
+
+	return &fileInfo{
+		FileInfo: fi,
+		// Use the file mode from the security descriptor, but use the
+		// calculated permission bits.
+		mode: perm | mode&^fs.FileMode(0o777),
+	}, nil
+}
+
+// retrieveDACL retrieves the discretionary access control list, owner, and
+// group from the security descriptor of the file with the specified absolute
+// name.
+func retrieveDACL(absName string) (dacl *windows.ACL, owner, group *windows.SID, err error) {
+	// desiredSecInfo defines the parts of a security descriptor to retrieve.
+	const desiredSecInfo windows.SECURITY_INFORMATION = windows.OWNER_SECURITY_INFORMATION |
+		windows.GROUP_SECURITY_INFORMATION |
+		windows.DACL_SECURITY_INFORMATION |
+		windows.PROTECTED_DACL_SECURITY_INFORMATION |
+		windows.UNPROTECTED_DACL_SECURITY_INFORMATION
+
+	sd, err := windows.GetNamedSecurityInfo(absName, windows.SE_FILE_OBJECT, desiredSecInfo)
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("getting security descriptor: %w", err)
+	}
+
+	dacl, _, err = sd.DACL()
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("getting discretionary access control list: %w", err)
+	}
+
+	owner, _, err = sd.Owner()
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("getting owner sid: %w", err)
+	}
+
+	group, _, err = sd.Group()
+	if err != nil {
+		return nil, nil, nil, fmt.Errorf("getting group sid: %w", err)
+	}
+
+	return dacl, owner, group, nil
+}
+
+// chmod is a Windows implementation of [Chmod].
+func chmod(name string, perm fs.FileMode) (err error) {
+	fi, err := os.Stat(name)
+	if err != nil {
+		return fmt.Errorf("getting file info: %w", err)
+	}
+
+	entries := make([]windows.EXPLICIT_ACCESS, 0, 3)
+	creatorMask, groupMask, worldMask := permToMasks(perm, fi.IsDir())
+
+	sidMasks := []struct {
+		Key   windows.WELL_KNOWN_SID_TYPE
+		Value windows.ACCESS_MASK
+	}{{
+		Key:   windows.WinCreatorOwnerSid,
+		Value: creatorMask,
+	}, {
+		Key:   windows.WinCreatorGroupSid,
+		Value: groupMask,
+	}, {
+		Key:   windows.WinWorldSid,
+		Value: worldMask,
+	}}
+
+	var errs []error
+	for _, sidMask := range sidMasks {
+		if sidMask.Value == 0 {
+			continue
+		}
+
+		var trustee windows.TRUSTEE
+		trustee, err = newWellKnownTrustee(sidMask.Key)
+		if err != nil {
+			errs = append(errs, err)
+
+			continue
+		}
+
+		entries = append(entries, windows.EXPLICIT_ACCESS{
+			AccessPermissions: sidMask.Value,
+			AccessMode:        windows.GRANT_ACCESS,
+			Inheritance:       windows.NO_INHERITANCE,
+			Trustee:           trustee,
+		})
+	}
+
+	if err = errors.Join(errs...); err != nil {
+		return fmt.Errorf("creating access control entries: %w", err)
+	}
+
+	acl, err := windows.ACLFromEntries(entries, nil)
+	if err != nil {
+		return fmt.Errorf("creating access control list: %w", err)
+	}
+
+	// secInfo defines the parts of a security descriptor to set.
+	const secInfo windows.SECURITY_INFORMATION = windows.DACL_SECURITY_INFORMATION |
+		windows.PROTECTED_DACL_SECURITY_INFORMATION
+
+	err = windows.SetNamedSecurityInfo(name, windows.SE_FILE_OBJECT, secInfo, nil, nil, acl, nil)
+	if err != nil {
+		return fmt.Errorf("setting security descriptor: %w", err)
+	}
+
+	return nil
+}
+
+// mkdir is a Windows implementation of [Mkdir].
+//
+// TODO(e.burkov):  Consider using [windows.CreateDirectory] instead of
+// [os.Mkdir] to reduce the number of syscalls.
+func mkdir(name string, perm os.FileMode) (err error) {
+	name, err = filepath.Abs(name)
+	if err != nil {
+		return fmt.Errorf("computing absolute path: %w", err)
+	}
+
+	err = os.Mkdir(name, perm)
+	if err != nil {
+		return fmt.Errorf("creating directory: %w", err)
+	}
+
+	defer func() {
+		if err != nil {
+			err = errors.WithDeferred(err, os.Remove(name))
+		}
+	}()
+
+	return chmod(name, perm)
+}
+
+// mkdirAll is a Windows implementation of [MkdirAll].
+func mkdirAll(path string, perm os.FileMode) (err error) {
+	parent, _ := filepath.Split(path)
+
+	if parent != "" {
+		err = os.MkdirAll(parent, perm)
+		if err != nil && !errors.Is(err, os.ErrExist) {
+			return fmt.Errorf("creating parent directories: %w", err)
+		}
+	}
+
+	err = mkdir(path, perm)
+	if errors.Is(err, os.ErrExist) {
+		return nil
+	}
+
+	return err
+}
+
+// writeFile is a Windows implementation of [WriteFile].
+func writeFile(filename string, data []byte, perm os.FileMode) (err error) {
+	file, err := openFile(filename, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, perm)
+	if err != nil {
+		return fmt.Errorf("opening file: %w", err)
+	}
+	defer func() { err = errors.WithDeferred(err, file.Close()) }()
+
+	_, err = file.Write(data)
+	if err != nil {
+		return fmt.Errorf("writing data: %w", err)
+	}
+
+	return nil
+}
+
+// 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)
+	if err != nil {
+		return windows.TRUSTEE{}, fmt.Errorf("creating sid for type %d: %w", stype, err)
+	}
+
+	return windows.TRUSTEE{
+		TrusteeForm:  windows.TRUSTEE_IS_SID,
+		TrusteeValue: windows.TrusteeValueFromSID(sid),
+	}, nil
+}
+
+// UNIX file mode permission bits.
+const (
+	permRead    = 0b100
+	permWrite   = 0b010
+	permExecute = 0b001
+)
+
+// Windows access masks for appropriate UNIX file mode permission bits and
+// file types.
+const (
+	fileReadRights windows.ACCESS_MASK = windows.READ_CONTROL |
+		windows.FILE_READ_DATA |
+		windows.FILE_READ_ATTRIBUTES |
+		windows.FILE_READ_EA |
+		windows.SYNCHRONIZE |
+		windows.ACCESS_SYSTEM_SECURITY
+
+	fileWriteRights windows.ACCESS_MASK = windows.WRITE_DAC |
+		windows.WRITE_OWNER |
+		windows.FILE_WRITE_DATA |
+		windows.FILE_WRITE_ATTRIBUTES |
+		windows.FILE_WRITE_EA |
+		windows.DELETE |
+		windows.FILE_APPEND_DATA |
+		windows.SYNCHRONIZE |
+		windows.ACCESS_SYSTEM_SECURITY
+
+	fileExecuteRights windows.ACCESS_MASK = windows.FILE_EXECUTE
+
+	dirReadRights windows.ACCESS_MASK = windows.READ_CONTROL |
+		windows.FILE_LIST_DIRECTORY |
+		windows.FILE_READ_EA |
+		windows.FILE_READ_ATTRIBUTES<<1 |
+		windows.SYNCHRONIZE |
+		windows.ACCESS_SYSTEM_SECURITY
+
+	dirWriteRights windows.ACCESS_MASK = windows.WRITE_DAC |
+		windows.WRITE_OWNER |
+		windows.DELETE |
+		windows.FILE_WRITE_DATA |
+		windows.FILE_APPEND_DATA |
+		windows.FILE_WRITE_EA |
+		windows.FILE_WRITE_ATTRIBUTES<<1 |
+		windows.SYNCHRONIZE |
+		windows.ACCESS_SYSTEM_SECURITY
+
+	dirExecuteRights windows.ACCESS_MASK = windows.FILE_TRAVERSE
+)
+
+// permToMasks converts a UNIX file mode permissions to the corresponding
+// Windows access masks.  The [isDir] argument is used to set specific access
+// bits for directories.
+func permToMasks(fm os.FileMode, isDir bool) (owner, group, world windows.ACCESS_MASK) {
+	mask := fm.Perm()
+
+	owner = permToMask(byte((mask>>6)&0b111), isDir)
+	group = permToMask(byte((mask>>3)&0b111), isDir)
+	world = permToMask(byte(mask&0b111), isDir)
+
+	return owner, group, world
+}
+
+// permToMask converts a UNIX file mode permission bits within p byte to the
+// corresponding Windows access mask.  The [isDir] argument is used to set
+// specific access bits for directories.
+func permToMask(p byte, isDir bool) (mask windows.ACCESS_MASK) {
+	readRights, writeRights, executeRights := fileReadRights, fileWriteRights, fileExecuteRights
+	if isDir {
+		readRights, writeRights, executeRights = dirReadRights, dirWriteRights, dirExecuteRights
+	}
+
+	if p&permRead != 0 {
+		mask |= readRights
+	}
+	if p&permWrite != 0 {
+		mask |= writeRights
+	}
+	if p&permExecute != 0 {
+		mask |= executeRights
+	}
+
+	return mask
+}
+
+// masksToPerm converts Windows access masks to the corresponding UNIX file
+// mode permission bits.
+func masksToPerm(u, g, o windows.ACCESS_MASK, isDir bool) (perm fs.FileMode) {
+	perm |= fs.FileMode(maskToPerm(u, isDir)) << 6
+	perm |= fs.FileMode(maskToPerm(g, isDir)) << 3
+	perm |= fs.FileMode(maskToPerm(o, isDir))
+
+	return perm
+}
+
+// maskToPerm converts a Windows access mask to the corresponding UNIX file
+// mode permission bits.
+func maskToPerm(mask windows.ACCESS_MASK, isDir bool) (perm byte) {
+	readMask, writeMask, executeMask := fileReadRights, fileWriteRights, fileExecuteRights
+	if isDir {
+		readMask, writeMask, executeMask = dirReadRights, dirWriteRights, dirExecuteRights
+	}
+
+	// Remove common bits to avoid false positive detection of unset rights.
+	readMask ^= windows.SYNCHRONIZE | windows.ACCESS_SYSTEM_SECURITY
+	writeMask ^= windows.SYNCHRONIZE | windows.ACCESS_SYSTEM_SECURITY
+
+	if mask&readMask != 0 {
+		perm |= permRead
+	}
+	if mask&writeMask != 0 {
+		perm |= permWrite
+	}
+	if mask&executeMask != 0 {
+		perm |= permExecute
+	}
+
+	return perm
+}

internal/aghos/permission_windows_internal_test.go

@@ -0,0 +1,135 @@
+//go:build windows
+
+package aghos
+
+import (
+	"io/fs"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/sys/windows"
+)
+
+func TestPermToMasks(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name      string
+		perm      fs.FileMode
+		wantUser  windows.ACCESS_MASK
+		wantGroup windows.ACCESS_MASK
+		wantOther windows.ACCESS_MASK
+		isDir     bool
+	}{{
+		name:      "all",
+		perm:      0b111_111_111,
+		wantUser:  fileReadRights | fileWriteRights | fileExecuteRights,
+		wantGroup: fileReadRights | fileWriteRights | fileExecuteRights,
+		wantOther: fileReadRights | fileWriteRights | fileExecuteRights,
+		isDir:     false,
+	}, {
+		name:      "user_write",
+		perm:      0b010_000_000,
+		wantUser:  fileWriteRights,
+		wantGroup: 0,
+		wantOther: 0,
+		isDir:     false,
+	}, {
+		name:      "group_read",
+		perm:      0b000_100_000,
+		wantUser:  0,
+		wantGroup: fileReadRights,
+		wantOther: 0,
+		isDir:     false,
+	}, {
+		name:      "all_dir",
+		perm:      0b111_111_111,
+		wantUser:  dirReadRights | dirWriteRights | dirExecuteRights,
+		wantGroup: dirReadRights | dirWriteRights | dirExecuteRights,
+		wantOther: dirReadRights | dirWriteRights | dirExecuteRights,
+		isDir:     true,
+	}, {
+		name:      "user_write_dir",
+		perm:      0b010_000_000,
+		wantUser:  dirWriteRights,
+		wantGroup: 0,
+		wantOther: 0,
+		isDir:     true,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			user, group, other := permToMasks(tc.perm, tc.isDir)
+			assert.Equal(t, tc.wantUser, user)
+			assert.Equal(t, tc.wantGroup, group)
+			assert.Equal(t, tc.wantOther, other)
+		})
+	}
+}
+
+func TestMasksToPerm(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name     string
+		user     windows.ACCESS_MASK
+		group    windows.ACCESS_MASK
+		other    windows.ACCESS_MASK
+		wantPerm fs.FileMode
+		isDir    bool
+	}{{
+		name:     "all",
+		user:     fileReadRights | fileWriteRights | fileExecuteRights,
+		group:    fileReadRights | fileWriteRights | fileExecuteRights,
+		other:    fileReadRights | fileWriteRights | fileExecuteRights,
+		wantPerm: 0b111_111_111,
+		isDir:    false,
+	}, {
+		name:     "user_write",
+		user:     fileWriteRights,
+		group:    0,
+		other:    0,
+		wantPerm: 0b010_000_000,
+		isDir:    false,
+	}, {
+		name:     "group_read",
+		user:     0,
+		group:    fileReadRights,
+		other:    0,
+		wantPerm: 0b000_100_000,
+		isDir:    false,
+	}, {
+		name:     "no_access",
+		user:     0,
+		group:    0,
+		other:    0,
+		wantPerm: 0,
+		isDir:    false,
+	}, {
+		name:     "all_dir",
+		user:     dirReadRights | dirWriteRights | dirExecuteRights,
+		group:    dirReadRights | dirWriteRights | dirExecuteRights,
+		other:    dirReadRights | dirWriteRights | dirExecuteRights,
+		wantPerm: 0b111_111_111,
+		isDir:    true,
+	}, {
+		name:     "user_write_dir",
+		user:     dirWriteRights,
+		group:    0,
+		other:    0,
+		wantPerm: 0b010_000_000,
+		isDir:    true,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Don't call [fs.FileMode.Perm] since the result is expected to
+			// contain only the permission bits.
+			assert.Equal(t, tc.wantPerm, masksToPerm(tc.user, tc.group, tc.other, tc.isDir))
+		})
+	}
+}

internal/aghrenameio/renameio_windows.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/golibs/errors"
 )
 
@@ -62,7 +63,7 @@ func newPendingFile(filePath string, mode fs.FileMode) (f PendingFile, err error
 		return nil, fmt.Errorf("opening pending file: %w", err)
 	}
 
-	err = file.Chmod(mode)
+	err = aghos.Chmod(file.Name(), mode)
 	if err != nil {
 		return nil, fmt.Errorf("preparing pending file: %w", err)
 	}

internal/filtering/filtering.go

@@ -1057,7 +1057,7 @@ func New(c *Config, blockFilters []Filter) (d *DNSFilter, err error) {
 		}
 	}
 
-	err = os.MkdirAll(filepath.Join(d.conf.DataDir, filterDir), aghos.DefaultPermDir)
+	err = aghos.MkdirAll(filepath.Join(d.conf.DataDir, filterDir), aghos.DefaultPermDir)
 	if err != nil {
 		d.Close()
 

internal/filtering/http.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 	"github.com/AdguardTeam/AdGuardHome/internal/filtering/rulelist"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
@@ -25,7 +26,7 @@ func (d *DNSFilter) validateFilterURL(urlStr string) (err error) {
 
 	if filepath.IsAbs(urlStr) {
 		urlStr = filepath.Clean(urlStr)
-		_, err = os.Stat(urlStr)
+		_, err = aghos.Stat(urlStr)
 		if err != nil {
 			// Don't wrap the error since it's informative enough as is.
 			return err

internal/home/auth.go

@@ -90,7 +90,11 @@ func InitAuth(
 		trustedProxies: trustedProxies,
 	}
 	var err error
-	a.db, err = bbolt.Open(dbFilename, aghos.DefaultPermFile, nil)
+
+	opts := *bbolt.DefaultOptions
+	opts.OpenFile = aghos.OpenFile
+
+	a.db, err = bbolt.Open(dbFilename, aghos.DefaultPermFile, &opts)
 	if err != nil {
 		log.Error("auth: open DB: %s: %s", dbFilename, err)
 		if err.Error() == "invalid argument" {

internal/home/config.go

@@ -708,7 +708,7 @@ func (c *configuration) write() (err error) {
 		return fmt.Errorf("generating config file: %w", err)
 	}
 
-	err = maybe.WriteFile(confPath, buf.Bytes(), aghos.DefaultPermFile)
+	err = aghos.WriteFile(confPath, buf.Bytes(), aghos.DefaultPermFile)
 	if err != nil {
 		return fmt.Errorf("writing config file: %w", err)
 	}

internal/home/home.go

@@ -643,7 +643,7 @@ func run(opts options, clientBuildFS fs.FS, done chan struct{}) {
 	}
 
 	dataDir := Context.getDataDir()
-	err = os.MkdirAll(dataDir, aghos.DefaultPermDir)
+	err = aghos.MkdirAll(dataDir, aghos.DefaultPermDir)
 	fatalOnError(errors.Annotate(err, "creating DNS data dir at %s: %w", dataDir))
 
 	GLMode = opts.glinetMode

internal/next/cmd/signal.go

@@ -9,7 +9,6 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/next/configmgr"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/osutil"
-	"github.com/google/renameio/v2/maybe"
 )
 
 // signalHandler processes incoming signals and shuts services down.
@@ -142,7 +141,7 @@ func (h *signalHandler) writePID() {
 	data = strconv.AppendInt(data, int64(os.Getpid()), 10)
 	data = append(data, '\n')
 
-	err := maybe.WriteFile(h.pidFile, data, 0o644)
+	err := aghos.WriteFile(h.pidFile, data, 0o644)
 	if err != nil {
 		log.Error("sighdlr: writing pidfile: %s", err)
 

internal/next/configmgr/configmgr.go

@@ -21,7 +21,6 @@ import (
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/timeutil"
-	"github.com/google/renameio/v2/maybe"
 	"gopkg.in/yaml.v3"
 )
 
@@ -183,7 +182,7 @@ func (m *Manager) write() (err error) {
 		return fmt.Errorf("encoding: %w", err)
 	}
 
-	err = maybe.WriteFile(m.fileName, b, aghos.DefaultPermFile)
+	err = aghos.WriteFile(m.fileName, b, aghos.DefaultPermFile)
 	if err != nil {
 		return fmt.Errorf("writing: %w", err)
 	}

internal/permcheck/migrate.go

@@ -14,7 +14,7 @@ import (
 //
 // TODO(a.garipov):  Consider ways to detect this better.
 func NeedsMigration(confFilePath string) (ok bool) {
-	s, err := os.Stat(confFilePath)
+	s, err := aghos.Stat(confFilePath)
 	if err != nil {
 		if errors.Is(err, os.ErrNotExist) {
 			// Likely a first run.  Don't check.
@@ -70,7 +70,7 @@ func chmodFile(filePath string) {
 // chmodPath changes the permissions of a single filesystem entity.  The results
 // are logged at the appropriate level.
 func chmodPath(entPath, fileType string, fm fs.FileMode) {
-	err := os.Chmod(entPath, fm)
+	err := aghos.Chmod(entPath, fm)
 	if err == nil {
 		log.Info("permcheck: changed permissions for %s %q", fileType, entPath)
 

internal/permcheck/permcheck.go

@@ -60,7 +60,7 @@ func checkFile(filePath string) {
 // checkPath checks the permissions of a single filesystem entity.  The results
 // are logged at the appropriate level.
 func checkPath(entPath, fileType string, want fs.FileMode) {
-	s, err := os.Stat(entPath)
+	s, err := aghos.Stat(entPath)
 	if err != nil {
 		logFunc := log.Error
 		if errors.Is(err, os.ErrNotExist) {

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.

internal/updater/updater.go

@@ -264,7 +264,7 @@ func (u *Updater) check() (err error) {
 // ignores the configuration file if firstRun is true.
 func (u *Updater) backup(firstRun bool) (err error) {
 	log.Debug("updater: backing up current configuration")
-	_ = os.Mkdir(u.backupDir, aghos.DefaultPermDir)
+	_ = aghos.Mkdir(u.backupDir, aghos.DefaultPermDir)
 	if !firstRun {
 		err = copyFile(u.confName, filepath.Join(u.backupDir, "AdGuardHome.yaml"))
 		if err != nil {
@@ -338,12 +338,12 @@ func (u *Updater) downloadPackageFile() (err error) {
 		return fmt.Errorf("io.ReadAll() failed: %w", err)
 	}
 
-	_ = os.Mkdir(u.updateDir, aghos.DefaultPermDir)
+	_ = aghos.Mkdir(u.updateDir, aghos.DefaultPermDir)
 
 	log.Debug("updater: saving package to file")
-	err = os.WriteFile(u.packageName, body, aghos.DefaultPermFile)
+	err = aghos.WriteFile(u.packageName, body, aghos.DefaultPermFile)
 	if err != nil {
-		return fmt.Errorf("os.WriteFile() failed: %w", err)
+		return fmt.Errorf("writing package file: %w", err)
 	}
 	return nil
 }
@@ -360,15 +360,15 @@ func tarGzFileUnpackOne(outDir string, tr *tar.Reader, hdr *tar.Header) (name st
 		if name == "AdGuardHome" {
 			// Top-level AdGuardHome/.  Skip it.
 			//
-			// TODO(a.garipov): This whole package needs to be
+			// TODO(a.garipov): This whole package needs to be rewritten and
-			// rewritten and covered in more integration tests.  It
+			// covered in more integration tests.  It has weird assumptions and
-			// has weird assumptions and file mode issues.
+			// file mode issues.
 			return "", nil
 		}
 
-		err = os.Mkdir(outputName, os.FileMode(hdr.Mode&0o755))
+		err = aghos.Mkdir(outputName, os.FileMode(hdr.Mode&0o755))
 		if err != nil && !errors.Is(err, os.ErrExist) {
-			return "", fmt.Errorf("os.Mkdir(%q): %w", outputName, err)
+			return "", fmt.Errorf("creating directory %q: %w", outputName, err)
 		}
 
 		log.Debug("updater: created directory %q", outputName)
@@ -383,7 +383,7 @@ func tarGzFileUnpackOne(outDir string, tr *tar.Reader, hdr *tar.Header) (name st
 	}
 
 	var wc io.WriteCloser
-	wc, err = os.OpenFile(
+	wc, err = aghos.OpenFile(
 		outputName,
 		os.O_WRONLY|os.O_CREATE|os.O_TRUNC,
 		os.FileMode(hdr.Mode&0o755),
@@ -464,14 +464,13 @@ func zipFileUnpackOne(outDir string, zf *zip.File) (name string, err error) {
 		if name == "AdGuardHome" {
 			// Top-level AdGuardHome/.  Skip it.
 			//
-			// TODO(a.garipov): See the similar todo in
+			// TODO(a.garipov): See the similar todo in tarGzFileUnpack.
-			// tarGzFileUnpack.
 			return "", nil
 		}
 
-		err = os.Mkdir(outputName, fi.Mode())
+		err = aghos.Mkdir(outputName, fi.Mode())
 		if err != nil && !errors.Is(err, os.ErrExist) {
-			return "", fmt.Errorf("os.Mkdir(%q): %w", outputName, err)
+			return "", fmt.Errorf("creating directory %q: %w", outputName, err)
 		}
 
 		log.Debug("updater: created directory %q", outputName)
@@ -480,7 +479,7 @@ func zipFileUnpackOne(outDir string, zf *zip.File) (name string, err error) {
 	}
 
 	var wc io.WriteCloser
-	wc, err = os.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, fi.Mode())
+	wc, err = aghos.OpenFile(outputName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, fi.Mode())
 	if err != nil {
 		return "", fmt.Errorf("os.OpenFile(): %w", err)
 	}
@@ -523,15 +522,19 @@ func zipFileUnpack(zipfile, outDir string) (files []string, err error) {
 }
 
 // Copy file on disk
-func copyFile(src, dst string) error {
+func copyFile(src, dst string) (err error) {
-	d, e := os.ReadFile(src)
+	d, err := os.ReadFile(src)
-	if e != nil {
+	if err != nil {
-		return e
+		// Don't wrap the error, since it's informative enough as is.
+		return err
 	}
-	e = os.WriteFile(dst, d, aghos.DefaultPermFile)
+
-	if e != nil {
+	err = aghos.WriteFile(dst, d, aghos.DefaultPermFile)
-		return e
+	if err != nil {
+		// Don't wrap the error, since it's informative enough as is.
+		return err
 	}
+
 	return nil
 }
 

scripts/make/go-lint.sh

@@ -54,9 +54,12 @@ set -f -u
 #
 #   *  Package unsafe is… unsafe.
 #
-# Currently, the only standard exception are files generated from protobuf
+# If your project needs more exceptions, add and document them.  Currently,
-# schemas, which use package reflect.  If your project needs more exceptions,
+# there are only two standard exceptions:
-# add and document them.
+#
+#   *  Files generated from protobuf schemas, which use package reflect.
+#
+#   *  Windows-specific code caused by golang.org/x/sys/windows API design.
 #
 # TODO(a.garipov): Add golibs/log.
 #
@@ -75,6 +78,7 @@ blocklist_imports() {
 		-n\
 		-- '*.go'\
 		':!*.pb.go'\
+		':!./internal/aghos/permission_windows.go'\
 		| sed -e 's/^\([^[:space:]]\+\)\(.*\)$/\1 blocked import:\2/'\
 		|| exit 0
 }