package fusefrontend import ( "os" "path/filepath" "strings" "sync" "sync/atomic" "syscall" "time" "github.com/rfjakob/gocryptfs/internal/configfile" "github.com/rfjakob/gocryptfs/internal/contentenc" "github.com/rfjakob/gocryptfs/internal/inomap" "github.com/rfjakob/gocryptfs/internal/nametransform" "github.com/rfjakob/gocryptfs/internal/serialize_reads" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) // RootNode is the root of the filesystem tree of Nodes. type RootNode struct { Node // args stores configuration arguments args Args // dirIVLock: Lock()ed if any "gocryptfs.diriv" file is modified // Readers must RLock() it to prevent them from seeing intermediate // states dirIVLock sync.RWMutex // Filename encryption helper nameTransform nametransform.NameTransformer // Content encryption helper contentEnc *contentenc.ContentEnc // This lock is used by openWriteOnlyFile() to block concurrent opens while // it relaxes the permissions on a file. openWriteOnlyLock sync.RWMutex // MitigatedCorruptions is used to report data corruption that is internally // mitigated by ignoring the corrupt item. For example, when OpenDir() finds // a corrupt filename, we still return the other valid filenames. // The corruption is logged to syslog to inform the user, and in addition, // the corrupt filename is logged to this channel via // reportMitigatedCorruption(). // "gocryptfs -fsck" reads from the channel to also catch these transparently- // mitigated corruptions. MitigatedCorruptions chan string // IsIdle flag is set to zero each time fs.isFiltered() is called // (uint32 so that it can be reset with CompareAndSwapUint32). // When -idle was used when mounting, idleMonitor() sets it to 1 // periodically. IsIdle uint32 // inoMap translates inode numbers from different devices to unique inode // numbers. inoMap inomap.TranslateStater } func NewRootNode(args Args, c *contentenc.ContentEnc, n nametransform.NameTransformer) *RootNode { if args.SerializeReads { serialize_reads.InitSerializer() } if len(args.Exclude) > 0 { tlog.Warn.Printf("Forward mode does not support -exclude") } rn := &RootNode{ args: args, nameTransform: n, contentEnc: c, inoMap: inomap.New(), } // In `-sharedstorage` mode we always set the inode number to zero. // This makes go-fuse generate a new inode number for each lookup. if args.SharedStorage { rn.inoMap = &inomap.TranslateStatZero{} } return rn } // mangleOpenFlags is used by Create() and Open() to convert the open flags the user // wants to the flags we internally use to open the backing file. // The returned flags always contain O_NOFOLLOW. func (rn *RootNode) mangleOpenFlags(flags uint32) (newFlags int) { newFlags = int(flags) // Convert WRONLY to RDWR. We always need read access to do read-modify-write cycles. if (newFlags & syscall.O_ACCMODE) == syscall.O_WRONLY { newFlags = newFlags ^ os.O_WRONLY | os.O_RDWR } // We also cannot open the file in append mode, we need to seek back for RMW newFlags = newFlags &^ os.O_APPEND // O_DIRECT accesses must be aligned in both offset and length. Due to our // crypto header, alignment will be off, even if userspace makes aligned // accesses. Running xfstests generic/013 on ext4 used to trigger lots of // EINVAL errors due to missing alignment. Just fall back to buffered IO. newFlags = newFlags &^ syscallcompat.O_DIRECT // Create and Open are two separate FUSE operations, so O_CREAT should not // be part of the open flags. newFlags = newFlags &^ syscall.O_CREAT // We always want O_NOFOLLOW to be safe against symlink races newFlags |= syscall.O_NOFOLLOW return newFlags } // reportMitigatedCorruption is used to report a corruption that was transparently // mitigated and did not return an error to the user. Pass the name of the corrupt // item (filename for OpenDir(), xattr name for ListXAttr() etc). // See the MitigatedCorruptions channel for more info. func (rn *RootNode) reportMitigatedCorruption(item string) { if rn.MitigatedCorruptions == nil { return } select { case rn.MitigatedCorruptions <- item: case <-time.After(1 * time.Second): tlog.Warn.Printf("BUG: reportCorruptItem: timeout") //debug.PrintStack() return } } // isFiltered - check if plaintext "path" should be forbidden // // Prevents name clashes with internal files when file names are not encrypted func (rn *RootNode) isFiltered(path string) bool { atomic.StoreUint32(&rn.IsIdle, 0) if !rn.args.PlaintextNames { return false } // gocryptfs.conf in the root directory is forbidden if path == configfile.ConfDefaultName { tlog.Info.Printf("The name /%s is reserved when -plaintextnames is used\n", configfile.ConfDefaultName) return true } // Note: gocryptfs.diriv is NOT forbidden because diriv and plaintextnames // are exclusive return false } // decryptSymlinkTarget: "cData64" is base64-decoded and decrypted // like file contents (GCM). // The empty string decrypts to the empty string. // // This function does not do any I/O and is hence symlink-safe. func (rn *RootNode) decryptSymlinkTarget(cData64 string) (string, error) { if cData64 == "" { return "", nil } cData, err := rn.nameTransform.B64DecodeString(cData64) if err != nil { return "", err } data, err := rn.contentEnc.DecryptBlock([]byte(cData), 0, nil) if err != nil { return "", err } return string(data), nil } // Due to RMW, we always need read permissions on the backing file. This is a // problem if the file permissions do not allow reading (i.e. 0200 permissions). // This function works around that problem by chmod'ing the file, obtaining a fd, // and chmod'ing it back. func (rn *RootNode) openWriteOnlyFile(dirfd int, cName string, newFlags int) (rwFd int, err error) { woFd, err := syscallcompat.Openat(dirfd, cName, syscall.O_WRONLY|syscall.O_NOFOLLOW, 0) if err != nil { return } defer syscall.Close(woFd) var st syscall.Stat_t err = syscall.Fstat(woFd, &st) if err != nil { return } // The cast to uint32 fixes a build failure on Darwin, where st.Mode is uint16. perms := uint32(st.Mode) // Verify that we don't have read permissions if perms&0400 != 0 { tlog.Warn.Printf("openWriteOnlyFile: unexpected permissions %#o, returning EPERM", perms) err = syscall.EPERM return } // Upgrade the lock to block other Open()s and downgrade again on return rn.openWriteOnlyLock.RUnlock() rn.openWriteOnlyLock.Lock() defer func() { rn.openWriteOnlyLock.Unlock() rn.openWriteOnlyLock.RLock() }() // Relax permissions and revert on return err = syscall.Fchmod(woFd, perms|0400) if err != nil { tlog.Warn.Printf("openWriteOnlyFile: changing permissions failed: %v", err) return } defer func() { err2 := syscall.Fchmod(woFd, perms) if err2 != nil { tlog.Warn.Printf("openWriteOnlyFile: reverting permissions failed: %v", err2) } }() return syscallcompat.Openat(dirfd, cName, newFlags, 0) } // openBackingDir opens the parent ciphertext directory of plaintext path // "relPath". It returns the dirfd (opened with O_PATH) and the encrypted // basename. // // The caller should then use Openat(dirfd, cName, ...) and friends. // For convenience, if relPath is "", cName is going to be ".". // // openBackingDir is secure against symlink races by using Openat and // ReadDirIVAt. // // Retries on EINTR. func (rn *RootNode) openBackingDir(relPath string) (dirfd int, cName string, err error) { dirRelPath := nametransform.Dir(relPath) // With PlaintextNames, we don't need to read DirIVs. Easy. if rn.args.PlaintextNames { dirfd, err = syscallcompat.OpenDirNofollow(rn.args.Cipherdir, dirRelPath) if err != nil { return -1, "", err } // If relPath is empty, cName is ".". cName = filepath.Base(relPath) return dirfd, cName, nil } // Open cipherdir (following symlinks) dirfd, err = syscallcompat.Open(rn.args.Cipherdir, syscall.O_DIRECTORY|syscallcompat.O_PATH, 0) if err != nil { return -1, "", err } // If relPath is empty, cName is ".". if relPath == "" { return dirfd, ".", nil } // Walk the directory tree parts := strings.Split(relPath, "/") for i, name := range parts { iv, err := nametransform.ReadDirIVAt(dirfd) if err != nil { syscall.Close(dirfd) return -1, "", err } cName, err = rn.nameTransform.EncryptAndHashName(name, iv) if err != nil { syscall.Close(dirfd) return -1, "", err } // Last part? We are done. if i == len(parts)-1 { break } // Not the last part? Descend into next directory. dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_NOFOLLOW|syscall.O_DIRECTORY|syscallcompat.O_PATH, 0) syscall.Close(dirfd) if err != nil { return -1, "", err } dirfd = dirfd2 } return dirfd, cName, nil } // encryptSymlinkTarget: "data" is encrypted like file contents (GCM) // and base64-encoded. // The empty string encrypts to the empty string. // // Symlink-safe because it does not do any I/O. func (rn *RootNode) encryptSymlinkTarget(data string) (cData64 string) { if data == "" { return "" } cData := rn.contentEnc.EncryptBlock([]byte(data), 0, nil) cData64 = rn.nameTransform.B64EncodeToString(cData) return cData64 } // encryptXattrValue encrypts the xattr value "data". // The data is encrypted like a file content block, but without binding it to // a file location (block number and file id are set to zero). // Special case: an empty value is encrypted to an empty value. func (rn *RootNode) encryptXattrValue(data []byte) (cData []byte) { if len(data) == 0 { return []byte{} } return rn.contentEnc.EncryptBlock(data, 0, nil) } // decryptXattrValue decrypts the xattr value "cData". func (rn *RootNode) decryptXattrValue(cData []byte) (data []byte, err error) { if len(cData) == 0 { return []byte{}, nil } data, err1 := rn.contentEnc.DecryptBlock([]byte(cData), 0, nil) if err1 == nil { return data, nil } // This backward compatibility is needed to support old // file systems having xattr values base64-encoded. cData, err2 := rn.nameTransform.B64DecodeString(string(cData)) if err2 != nil { // Looks like the value was not base64-encoded, but just corrupt. // Return the original decryption error: err1 return nil, err1 } return rn.contentEnc.DecryptBlock([]byte(cData), 0, nil) } // encryptXattrName transforms "user.foo" to "user.gocryptfs.a5sAd4XAa47f5as6dAf" func (rn *RootNode) encryptXattrName(attr string) (cAttr string) { // xattr names are encrypted like file names, but with a fixed IV. cAttr = xattrStorePrefix + rn.nameTransform.EncryptName(attr, xattrNameIV) return cAttr } func (rn *RootNode) decryptXattrName(cAttr string) (attr string, err error) { // Reject anything that does not start with "user.gocryptfs." if !strings.HasPrefix(cAttr, xattrStorePrefix) { return "", syscall.EINVAL } // Strip "user.gocryptfs." prefix cAttr = cAttr[len(xattrStorePrefix):] attr, err = rn.nameTransform.DecryptName(cAttr, xattrNameIV) if err != nil { return "", err } return attr, nil }