1 files changed, 169 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_xattr.go b/pkg/sentry/syscalls/linux/sys_xattr.go
new file mode 100644
index 000000000..97d9a65ea
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_xattr.go
@@ -0,0 +1,169 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// Getxattr implements linux syscall getxattr(2).
+func Getxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	pathAddr := args[0].Pointer()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := args[3].SizeT()
+
+	path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	valueLen := 0
+	err = fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		value, err := getxattr(t, d, dirPath, nameAddr)
+		if err != nil {
+			return err
+		}
+
+		valueLen = len(value)
+		if size == 0 {
+			return nil
+		}
+		if size > linux.XATTR_SIZE_MAX {
+			size = linux.XATTR_SIZE_MAX
+		}
+		if valueLen > int(size) {
+			return syserror.ERANGE
+		}
+
+		_, err = t.CopyOutBytes(valueAddr, []byte(value))
+		return err
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(valueLen), nil, nil
+}
+
+// getxattr implements getxattr from the given *fs.Dirent.
+func getxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr) (string, error) {
+	if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+		return "", syserror.ENOTDIR
+	}
+
+	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil {
+		return "", err
+	}
+
+	name, err := copyInXattrName(t, nameAddr)
+	if err != nil {
+		return "", err
+	}
+
+	if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+		return "", syserror.EOPNOTSUPP
+	}
+
+	return d.Inode.Getxattr(name)
+}
+
+// Setxattr implements linux syscall setxattr(2).
+func Setxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	pathAddr := args[0].Pointer()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := args[3].SizeT()
+	flags := args[4].Uint()
+
+	path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		return setxattr(t, d, dirPath, nameAddr, valueAddr, size, flags)
+	})
+}
+
+// setxattr implements setxattr from the given *fs.Dirent.
+func setxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint, flags uint32) error {
+	if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+		return syserror.ENOTDIR
+	}
+
+	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Write: true}); err != nil {
+		return err
+	}
+
+	name, err := copyInXattrName(t, nameAddr)
+	if err != nil {
+		return err
+	}
+
+	if size > linux.XATTR_SIZE_MAX {
+		return syserror.E2BIG
+	}
+	buf := make([]byte, size)
+	if _, err = t.CopyInBytes(valueAddr, buf); err != nil {
+		return err
+	}
+	value := string(buf)
+
+	if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+		return syserror.EOPNOTSUPP
+	}
+
+	return d.Inode.Setxattr(name, value)
+}
+
+func copyInXattrName(t *kernel.Task, nameAddr usermem.Addr) (string, error) {
+	name, err := t.CopyInString(nameAddr, linux.XATTR_NAME_MAX+1)
+	if err != nil {
+		if err == syserror.ENAMETOOLONG {
+			return "", syserror.ERANGE
+		}
+		return "", err
+	}
+	if len(name) == 0 {
+		return "", syserror.ERANGE
+	}
+	return name, nil
+}
+
+func checkXattrPermissions(t *kernel.Task, i *fs.Inode, perms fs.PermMask) error {
+	// Restrict xattrs to regular files and directories.
+	//
+	// In Linux, this restriction technically only applies to xattrs in the
+	// "user.*" namespace, but we don't allow any other xattr prefixes anyway.
+	if !fs.IsRegular(i.StableAttr) && !fs.IsDir(i.StableAttr) {
+		if perms.Write {
+			return syserror.EPERM
+		}
+		return syserror.ENODATA
+	}
+
+	return i.CheckPermission(t, perms)
+}