127 lines
3.6 KiB
Go
127 lines
3.6 KiB
Go
// +build linux
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// Package fusefrontend interfaces directly with the go-fuse library.
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package fusefrontend
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import (
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"fmt"
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"strings"
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"syscall"
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"github.com/hanwen/go-fuse/fuse"
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"github.com/pkg/xattr"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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// Only allow the "user" namespace, block "trusted" and "security", as
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// these may be interpreted by the system, and we don't want to cause
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// trouble with our encrypted garbage.
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const xattrUserPrefix = "user."
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func disallowedXAttrName(attr string) bool {
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return !strings.HasPrefix(attr, xattrUserPrefix)
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}
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func filterXattrSetFlags(flags int) int {
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return flags
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}
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// procFd returns the path to file descriptor "fd" in /proc/self/fd.
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func procFd(fd int) string {
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return fmt.Sprintf("/proc/self/fd/%d", fd)
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}
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// getFileFd calls fs.Open() on relative plaintext path "relPath" and returns
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// the resulting fusefrontend.*File along with the underlying fd. The caller
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// MUST call file.Release() when done with the file. The O_NONBLOCK flag is
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// used to not block on FIFOs.
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//
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// Used by xattrGet() and friends.
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func (fs *FS) getFileFd(relPath string, context *fuse.Context) (*File, int, fuse.Status) {
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fuseFile, status := fs.Open(relPath, syscall.O_RDONLY|syscall.O_NONBLOCK, context)
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if !status.Ok() {
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return nil, -1, status
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}
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file, ok := fuseFile.(*File)
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if !ok {
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tlog.Warn.Printf("BUG: xattrGet: cast to *File failed")
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fuseFile.Release()
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return nil, -1, fuse.EIO
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}
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return file, file.intFd(), fuse.OK
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}
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// getXattr - read encrypted xattr name "cAttr" from relative
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// plaintext path "relPath". Returns the encrypted xattr value.
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//
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// This function is symlink-safe by using /proc/self/fd.
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func (fs *FS) getXattr(relPath string, cAttr string, context *fuse.Context) ([]byte, fuse.Status) {
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file, fd, status := fs.getFileFd(relPath, context)
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if !status.Ok() {
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return nil, status
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}
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defer file.Release()
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cData, err := xattr.Get(procFd(fd), cAttr)
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if err != nil {
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return nil, unpackXattrErr(err)
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}
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return cData, fuse.OK
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}
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// setXattr - set encrypted xattr name "cAttr" to value "cData" on plaintext
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// path "relPath".
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//
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// This function is symlink-safe by using /proc/self/fd.
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func (fs *FS) setXattr(relPath string, cAttr string, cData []byte, flags int, context *fuse.Context) fuse.Status {
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file, fd, status := fs.getFileFd(relPath, context)
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if !status.Ok() {
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return status
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}
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defer file.Release()
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err := xattr.SetWithFlags(procFd(fd), cAttr, cData, flags)
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return unpackXattrErr(err)
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}
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// removeXAttr - remove encrypted xattr name "cAttr" from
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// plaintext path "relPath".
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//
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// This function is symlink-safe on Linux by using /proc/self/fd.
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func (fs *FS) removeXAttr(relPath string, cAttr string, context *fuse.Context) fuse.Status {
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file, fd, status := fs.getFileFd(relPath, context)
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if !status.Ok() {
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return status
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}
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defer file.Release()
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err := xattr.Remove(procFd(fd), cAttr)
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return unpackXattrErr(err)
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}
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// listXAttr - list encrypted xattr names on plaintext path "relPath".
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//
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// This function is symlink-safe on Linux by using /proc/self/fd.
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func (fs *FS) listXAttr(relPath string, context *fuse.Context) ([]string, fuse.Status) {
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file, fd, status := fs.getFileFd(relPath, context)
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if !status.Ok() {
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// If relPath is a symlink, getFileFd fails with ELOOP. As setXattr()
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// also fails with ELOOP, there is no way to set xattrs on symlinks,
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// and we can assume that the file does not have any.
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if status == fuse.Status(syscall.ELOOP) {
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return nil, fuse.OK
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}
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return nil, status
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}
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defer file.Release()
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cNames, err := xattr.List(procFd(fd))
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if err != nil {
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status := unpackXattrErr(err)
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return nil, status
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}
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return cNames, fuse.OK
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}
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