e827763f2e
This fixes a few issues I have found reviewing the code: 1) Limit the amount of data ReadLongName() will read. Previously, you could send gocryptfs into out-of-memory by symlinking gocryptfs.diriv to /dev/zero. 2) Handle the empty input case in unPad16() by returning an error. Previously, it would panic with an out-of-bounds array read. It is unclear to me if this could actually be triggered. 3) Reject empty names after base64-decoding in DecryptName(). An empty name crashes emeCipher.Decrypt(). It is unclear to me if B64.DecodeString() can actually return a non-error empty result, but let's guard against it anyway.
128 lines
3.8 KiB
Go
128 lines
3.8 KiB
Go
package nametransform
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import (
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"crypto/sha256"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"strings"
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"syscall"
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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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// LongNameSuffix is the suffix used for files with long names.
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// Files with long names are stored in two files:
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// gocryptfs.longname.[sha256] <--- File content, prefix = gocryptfs.longname.
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// gocryptfs.longname.[sha256].name <--- File name, suffix = .name
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LongNameSuffix = ".name"
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longNamePrefix = "gocryptfs.longname."
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)
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// HashLongName - take the hash of a long string "name" and return
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// "gocryptfs.longname.[sha256]"
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func (n *NameTransform) HashLongName(name string) string {
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hashBin := sha256.Sum256([]byte(name))
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hashBase64 := n.B64.EncodeToString(hashBin[:])
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return longNamePrefix + hashBase64
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}
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// Values returned by IsLongName
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const (
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// LongNameContent is the file that stores the file content.
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// Example: gocryptfs.longname.URrM8kgxTKYMgCk4hKk7RO9Lcfr30XQof4L_5bD9Iro=
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LongNameContent = iota
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// LongNameFilename is the file that stores the full encrypted filename.
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// Example: gocryptfs.longname.URrM8kgxTKYMgCk4hKk7RO9Lcfr30XQof4L_5bD9Iro=.name
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LongNameFilename = iota
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// LongNameNone is used when the file does not have a long name.
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// Example: i1bpTaVLZq7sRNA9mL_2Ig==
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LongNameNone = iota
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)
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// NameType - detect if cName is
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// gocryptfs.longname.[sha256] ........ LongNameContent (content of a long name file)
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// gocryptfs.longname.[sha256].name .... LongNameFilename (full file name of a long name file)
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// else ................................ LongNameNone (normal file)
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func NameType(cName string) int {
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if !strings.HasPrefix(cName, longNamePrefix) {
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return LongNameNone
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}
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if strings.HasSuffix(cName, LongNameSuffix) {
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return LongNameFilename
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}
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return LongNameContent
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}
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// IsLongContent returns true if "cName" is the content store of a long name
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// file (looks like "gocryptfs.longname.[sha256]").
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func IsLongContent(cName string) bool {
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return NameType(cName) == LongNameContent
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}
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// ReadLongName - read "$path.name"
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func ReadLongName(path string) (string, error) {
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path += LongNameSuffix
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fd, err := os.Open(path)
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if err != nil {
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return "", err
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}
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defer fd.Close()
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// 256 (=255 padded to 16) bytes base64-encoded take 344 bytes: "AAAAAAA...AAA=="
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lim := 344
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// Allocate a bigger buffer so we see whether the file is too big
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buf := make([]byte, lim+1)
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n, err := fd.ReadAt(buf, 0)
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if err != nil && err != io.EOF {
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return "", err
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}
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if n == 0 {
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return "", fmt.Errorf("ReadLongName: empty file")
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}
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if n > lim {
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return "", fmt.Errorf("ReadLongName: size=%d > limit=%d", n, lim)
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}
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return string(buf[0:n]), nil
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}
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// DeleteLongName deletes "hashName.name".
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func DeleteLongName(dirfd *os.File, hashName string) error {
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err := syscallcompat.Unlinkat(int(dirfd.Fd()), hashName+LongNameSuffix)
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if err != nil {
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tlog.Warn.Printf("DeleteLongName: %v", err)
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}
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return err
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}
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// WriteLongName encrypts plainName and writes it into "hashName.name".
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// For the convenience of the caller, plainName may also be a path and will be
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// converted internally.
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func (n *NameTransform) WriteLongName(dirfd *os.File, hashName string, plainName string) (err error) {
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plainName = filepath.Base(plainName)
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// Encrypt the basename
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dirIV, err := ReadDirIVAt(dirfd)
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if err != nil {
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return err
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}
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cName := n.EncryptName(plainName, dirIV)
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// Write the encrypted name into hashName.name
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fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), hashName+LongNameSuffix,
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syscall.O_WRONLY|syscall.O_CREAT|syscall.O_EXCL, 0600)
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if err != nil {
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tlog.Warn.Printf("WriteLongName: Openat: %v", err)
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return err
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}
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fd := os.NewFile(uintptr(fdRaw), hashName+LongNameSuffix)
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defer fd.Close()
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_, err = fd.Write([]byte(cName))
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if err != nil {
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tlog.Warn.Printf("WriteLongName: Write: %v", err)
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}
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return err
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}
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