AdGuardHome/internal/aghos/permission_windows.go

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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 9417b7dc510296c096f234e2f340dad5a6faf627 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Mon Oct 28 19:41:30 2024 +0300 aghos: imp doc commit b91f0e72a70a8e1392bd07b50714d8b83cc4e33e Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Mon Oct 28 19:26:15 2024 +0300 all: rm bin commit 9008ee93b181794c5082894bfa5ce4c76153f93d Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Mon Oct 28 18:23:54 2024 +0300 all: revert permcheck commit bcc85d50f5f39269713979c6509a9acd220570b8 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Mon Oct 28 17:48:55 2024 +0300 all: use aghos more commit 993e351712fbf004a6f96e06061ba2321c1c46e1 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Mon Oct 28 16:24:56 2024 +0300 all: fix more bugs commit a22b0d265eb0fa747e136363558b97de54e593b8 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 18:30:52 2024 +0300 all: fix bugs commit a2309f812ad3fd83d26c373b67756ea3074f4854 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 17:05:08 2024 +0300 all: fix chlog, imp api commit 42c3f8e91c49998068bc208166de20efe49c3dcb Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 16:04:47 2024 +0300 scripts: fix docs commit 9e781ff18db58ed9be35e259ecf3c669a4d41e02 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 16:03:19 2024 +0300 scripts: imp docs commit 1dbc7849828cc4933bb5edc3257f158ac292d48e Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 15:55:16 2024 +0300 all: use new functions, add tests commit dcbabaf4e37149a73969c52c9bfac2b9d9127a67 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Fri Oct 25 13:23:50 2024 +0300 aghos: add stat commit 72d7c0f881835725e65db63ac2dd1c5f7a409036 Author: Eugene Burkov <E.Burkov@AdGuard.COM> Date: Thu Oct 24 17:10:30 2024 +0300 aghos: add windows functions
2024-10-29 11:28:59 +00:00
//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
}