added -noxattr flag which ignores all xattr operations (#987)

* added -noxattr flag which ignores all xattr operations

Author: jkowalski

cli_args.go

@@ -31,7 +31,7 @@ type argContainer struct {
 	longnames, allow_other, reverse, aessiv, nonempty, raw64,
 	noprealloc, speed, hkdf, serialize_reads, hh, info,
 	sharedstorage, fsck, one_file_system, deterministic_names,
-	xchacha bool
+	xchacha, noxattr bool
 	// Mount options with opposites
 	dev, nodev, suid, nosuid, exec, noexec, rw, ro, kernel_cache, acl bool
 	masterkey, mountpoint, cipherdir, cpuprofile,
@@ -188,6 +188,7 @@ func parseCliOpts(osArgs []string) (args argContainer) {
 	flagSet.BoolVar(&args.one_file_system, "one-file-system", false, "Don't cross filesystem boundaries")
 	flagSet.BoolVar(&args.deterministic_names, "deterministic-names", false, "Disable diriv file name randomisation")
 	flagSet.BoolVar(&args.xchacha, "xchacha", false, "Use XChaCha20-Poly1305 file content encryption")
+	flagSet.BoolVar(&args.noxattr, "noxattr", false, "Disable extended attribute operations")
 
 	// Mount options with opposites
 	flagSet.BoolVar(&args.dev, "dev", false, "Allow device files")

internal/fusefrontend/args.go

@@ -51,4 +51,6 @@ type Args struct {
 	OneFileSystem bool
 	// DeterministicNames disables gocryptfs.diriv files
 	DeterministicNames bool
+	// NoXattr disables extended attribute operations
+	NoXattr bool
 }

internal/fusefrontend/node_xattr.go

@@ -32,6 +32,10 @@ func isAcl(attr string) bool {
 // This function is symlink-safe through Fgetxattr.
 func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32, syscall.Errno) {
 	rn := n.rootNode()
+	// If -noxattr is enabled, return ENOATTR for all getxattr calls
+	if rn.args.NoXattr {
+		return 0, noSuchAttributeError
+	}
 	// If we are not mounted with -suid, reading the capability xattr does not
 	// make a lot of sense, so reject the request and gain a massive speedup.
 	// See https://github.com/rfjakob/gocryptfs/issues/515 .
@@ -77,6 +81,10 @@ func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32,
 // This function is symlink-safe through Fsetxattr.
 func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uint32) syscall.Errno {
 	rn := n.rootNode()
+	// If -noxattr is enabled, fail all setxattr calls
+	if rn.args.NoXattr {
+		return syscall.EOPNOTSUPP
+	}
 	flags = uint32(filterXattrSetFlags(int(flags)))
 
 	// ACLs are passed through without encryption
@@ -102,6 +110,10 @@ func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uin
 // This function is symlink-safe through Fremovexattr.
 func (n *Node) Removexattr(ctx context.Context, attr string) syscall.Errno {
 	rn := n.rootNode()
+	// If -noxattr is enabled, fail all removexattr calls
+	if rn.args.NoXattr {
+		return syscall.EOPNOTSUPP
+	}
 
 	// ACLs are passed through without encryption
 	if isAcl(attr) {
@@ -119,11 +131,15 @@ func (n *Node) Removexattr(ctx context.Context, attr string) syscall.Errno {
 //
 // This function is symlink-safe through Flistxattr.
 func (n *Node) Listxattr(ctx context.Context, dest []byte) (uint32, syscall.Errno) {
+	rn := n.rootNode()
+	// If -noxattr is enabled, return zero results for listxattr
+	if rn.args.NoXattr {
+		return 0, 0
+	}
 	cNames, errno := n.listXAttr()
 	if errno != 0 {
 		return 0, errno
 	}
-	rn := n.rootNode()
 	var buf bytes.Buffer
 	for _, curName := range cNames {
 		// ACLs are passed through without encryption

internal/fusefrontend/node_xattr_darwin.go

@@ -11,6 +11,9 @@ import (
 	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
 )
 
+// On Darwin, ENOATTR is returned when an attribute is not found.
+const noSuchAttributeError = syscall.ENOATTR
+
 // On Darwin we have to unset XATTR_NOSECURITY 0x0008
 func filterXattrSetFlags(flags int) int {
 	// See https://opensource.apple.com/source/xnu/xnu-1504.15.3/bsd/sys/xattr.h.auto.html

internal/fusefrontend/node_xattr_linux.go

@@ -12,6 +12,9 @@ import (
 	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
 )
 
+// On Linux, ENODATA is returned when an attribute is not found.
+const noSuchAttributeError = syscall.ENODATA
+
 func filterXattrSetFlags(flags int) int {
 	return flags
 }

internal/fusefrontend_reverse/node_xattr.go

@@ -25,6 +25,10 @@ func isAcl(attr string) bool {
 // This function is symlink-safe through Fgetxattr.
 func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32, syscall.Errno) {
 	rn := n.rootNode()
+	// If -noxattr is enabled, return ENOATTR for all getxattr calls
+	if rn.args.NoXattr {
+		return 0, noSuchAttributeError
+	}
 	var data []byte
 	// ACLs are passed through without encryption
 	if isAcl(attr) {
@@ -56,11 +60,15 @@ func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32,
 //
 // This function is symlink-safe through Flistxattr.
 func (n *Node) Listxattr(ctx context.Context, dest []byte) (uint32, syscall.Errno) {
+	rn := n.rootNode()
+	// If -noxattr is enabled, return zero results for listxattr
+	if rn.args.NoXattr {
+		return 0, 0
+	}
 	pNames, errno := n.listXAttr()
 	if errno != 0 {
 		return 0, errno
 	}
-	rn := n.rootNode()
 	var buf bytes.Buffer
 	for _, pName := range pNames {
 		// ACLs are passed through without encryption

internal/fusefrontend_reverse/node_xattr_darwin.go

@@ -8,6 +8,9 @@ import (
 	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
 )
 
+// On Darwin, ENOATTR is returned when an attribute is not found.
+const noSuchAttributeError = syscall.ENOATTR
+
 func (n *Node) getXAttr(cAttr string) (out []byte, errno syscall.Errno) {
 	d, errno := n.prepareAtSyscall("")
 	if errno != 0 {

internal/fusefrontend_reverse/node_xattr_linux.go

@@ -9,6 +9,9 @@ import (
 	"github.com/rfjakob/gocryptfs/v2/internal/syscallcompat"
 )
 
+// On Linux, ENODATA is returned when an attribute is not found.
+const noSuchAttributeError = syscall.ENODATA
+
 func (n *Node) getXAttr(cAttr string) (out []byte, errno syscall.Errno) {
 	d, errno := n.prepareAtSyscall("")
 	if errno != 0 {

mount.go

@@ -284,6 +284,7 @@ func initFuseFrontend(args *argContainer) (rootNode fs.InodeEmbedder, wipeKeys f
 		SharedStorage:      args.sharedstorage,
 		OneFileSystem:      args.one_file_system,
 		DeterministicNames: args.deterministic_names,
+		NoXattr:            args.noxattr,
 	}
 	// confFile is nil when "-zerokey" or "-masterkey" was used
 	if confFile != nil {