119 lines
3.8 KiB
Go
119 lines
3.8 KiB
Go
package fusefrontend_reverse
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import (
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"log"
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"path/filepath"
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"syscall"
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"golang.org/x/sys/unix"
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"github.com/hanwen/go-fuse/fuse"
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"github.com/hanwen/go-fuse/fuse/nodefs"
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"github.com/rfjakob/gocryptfs/internal/nametransform"
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"github.com/rfjakob/gocryptfs/internal/pathiv"
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"github.com/rfjakob/gocryptfs/internal/syscallcompat"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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const (
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// virtualFileMode is the mode to use for virtual files (gocryptfs.diriv and
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// *.name). They are always readable, as stated in func Access
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virtualFileMode = syscall.S_IFREG | 0444
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// inoBaseDirIV is the start of the inode number range that is used
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// for virtual gocryptfs.diriv files. inoBaseNameFile is the thing for
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// *.name files.
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// The value 10^19 is just below 2^60. A power of 10 has been chosen so the
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// "ls -li" output (which is base-10) is easy to read.
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// 10^19 is the largest power of 10 that is smaller than
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// INT64_MAX (=UINT64_MAX/2). This avoids signedness issues.
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inoBaseDirIV = uint64(1000000000000000000)
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inoBaseNameFile = uint64(2000000000000000000)
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// inoBaseMin marks the start of the inode number space that is
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// reserved for virtual files. It is the lowest of the inoBaseXXX values
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// above.
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inoBaseMin = inoBaseDirIV
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)
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func (rfs *ReverseFS) newDirIVFile(cRelPath string) (nodefs.File, fuse.Status) {
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cDir := nametransform.Dir(cRelPath)
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dir, err := rfs.decryptPath(cDir)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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iv := pathiv.Derive(cDir, pathiv.PurposeDirIV)
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return rfs.newVirtualFile(iv, rfs.args.Cipherdir, dir, inoBaseDirIV)
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}
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type virtualFile struct {
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// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
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nodefs.File
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// file content
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content []byte
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// backing directory
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cipherdir string
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// path to a parent file (relative to cipherdir)
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parentFile string
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// inode number of a virtual file is inode of parent file plus inoBase
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inoBase uint64
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}
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// newVirtualFile creates a new in-memory file that does not have a representation
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// on disk. "content" is the file content. Timestamps and file owner are copied
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// from "parentFile" (plaintext path relative to "cipherdir").
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// For a "gocryptfs.diriv" file, you would use the parent directory as
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// "parentFile".
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func (rfs *ReverseFS) newVirtualFile(content []byte, cipherdir string, parentFile string, inoBase uint64) (nodefs.File, fuse.Status) {
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if inoBase < inoBaseMin {
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log.Panicf("BUG: virtual inode number base %d is below reserved space", inoBase)
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}
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return &virtualFile{
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File: nodefs.NewDefaultFile(),
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content: content,
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cipherdir: cipherdir,
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parentFile: parentFile,
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inoBase: inoBase,
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}, fuse.OK
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}
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// Read - FUSE call
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func (f *virtualFile) Read(buf []byte, off int64) (resultData fuse.ReadResult, status fuse.Status) {
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if off >= int64(len(f.content)) {
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return nil, fuse.OK
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}
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end := int(off) + len(buf)
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if end > len(f.content) {
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end = len(f.content)
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}
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return fuse.ReadResultData(f.content[off:end]), fuse.OK
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}
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// GetAttr - FUSE call
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func (f *virtualFile) GetAttr(a *fuse.Attr) fuse.Status {
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dir := filepath.Dir(f.parentFile)
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dirfd, err := syscallcompat.OpenDirNofollow(f.cipherdir, dir)
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if err != nil {
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return fuse.ToStatus(err)
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}
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defer syscall.Close(dirfd)
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name := filepath.Base(f.parentFile)
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var st unix.Stat_t
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err = syscallcompat.Fstatat(dirfd, name, &st, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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tlog.Debug.Printf("GetAttr: Fstatat %q: %v\n", f.parentFile, err)
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return fuse.ToStatus(err)
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}
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if st.Ino > inoBaseMin {
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tlog.Warn.Printf("virtualFile.GetAttr: parent file inode number %d crosses reserved space, max=%d. Returning EOVERFLOW.",
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st.Ino, inoBaseMin)
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return fuse.ToStatus(syscall.EOVERFLOW)
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}
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st.Ino = st.Ino + f.inoBase
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st.Size = int64(len(f.content))
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st.Mode = virtualFileMode
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st.Nlink = 1
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st2 := syscallcompat.Unix2syscall(st)
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a.FromStat(&st2)
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return fuse.OK
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}
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