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-rw-r--r--internal/fusefrontend/fs_dir.go11
-rw-r--r--internal/nametransform/longnames.go27
-rw-r--r--internal/nametransform/names.go8
-rw-r--r--internal/nametransform/names_test.go17
-rw-r--r--internal/nametransform/pad16.go17
5 files changed, 59 insertions, 21 deletions
diff --git a/internal/fusefrontend/fs_dir.go b/internal/fusefrontend/fs_dir.go
index 7d1e3ef..30e715a 100644
--- a/internal/fusefrontend/fs_dir.go
+++ b/internal/fusefrontend/fs_dir.go
@@ -273,16 +273,14 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
// silently ignore "gocryptfs.conf" in the top level dir
continue
}
- if !fs.args.PlaintextNames && cName == nametransform.DirIVFilename {
- // silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
- continue
- }
-
if fs.args.PlaintextNames {
plain = append(plain, cipherEntries[i])
continue
}
-
+ if cName == nametransform.DirIVFilename {
+ // silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
+ continue
+ }
// Handle long file name
isLong := nametransform.LongNameNone
if fs.args.LongNames {
@@ -301,7 +299,6 @@ func (fs *FS) OpenDir(dirName string, context *fuse.Context) ([]fuse.DirEntry, f
// ignore "gocryptfs.longname.*.name"
continue
}
-
name, err := fs.nameTransform.DecryptName(cName, cachedIV)
if err != nil {
tlog.Warn.Printf("OpenDir %q: invalid entry %q: %v",
diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
index 54095a4..8af191d 100644
--- a/internal/nametransform/longnames.go
+++ b/internal/nametransform/longnames.go
@@ -2,7 +2,8 @@ package nametransform
import (
"crypto/sha256"
- "io/ioutil"
+ "fmt"
+ "io"
"os"
"path/filepath"
"strings"
@@ -62,13 +63,29 @@ func IsLongContent(cName string) bool {
return NameType(cName) == LongNameContent
}
-// ReadLongName - read path.name
+// ReadLongName - read "$path.name"
func ReadLongName(path string) (string, error) {
- content, err := ioutil.ReadFile(path + LongNameSuffix)
+ path += LongNameSuffix
+ fd, err := os.Open(path)
if err != nil {
- tlog.Warn.Printf("ReadLongName: %v", err)
+ return "", err
}
- return string(content), err
+ defer fd.Close()
+ // 256 (=255 padded to 16) bytes base64-encoded take 344 bytes: "AAAAAAA...AAA=="
+ lim := 344
+ // Allocate a bigger buffer so we see whether the file is too big
+ buf := make([]byte, lim+1)
+ n, err := fd.ReadAt(buf, 0)
+ if err != nil && err != io.EOF {
+ return "", err
+ }
+ if n == 0 {
+ return "", fmt.Errorf("ReadLongName: empty file")
+ }
+ if n > lim {
+ return "", fmt.Errorf("ReadLongName: size=%d > limit=%d", n, lim)
+ }
+ return string(buf[0:n]), nil
}
// DeleteLongName deletes "hashName.name".
diff --git a/internal/nametransform/names.go b/internal/nametransform/names.go
index c96f7ce..3447583 100644
--- a/internal/nametransform/names.go
+++ b/internal/nametransform/names.go
@@ -42,6 +42,10 @@ func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error
if err != nil {
return "", err
}
+ if len(bin) == 0 {
+ tlog.Warn.Printf("DecryptName: empty input")
+ return "", syscall.EBADMSG
+ }
if len(bin)%aes.BlockSize != 0 {
tlog.Debug.Printf("DecryptName %q: decoded length %d is not a multiple of 16", cipherName, len(bin))
return "", syscall.EBADMSG
@@ -49,14 +53,14 @@ func (n *NameTransform) DecryptName(cipherName string, iv []byte) (string, error
bin = n.emeCipher.Decrypt(iv, bin)
bin, err = unPad16(bin)
if err != nil {
- tlog.Debug.Printf("DecryptName: unPad16 error: %v", err)
+ tlog.Debug.Printf("DecryptName: unPad16 error detail: %v", err)
// unPad16 returns detailed errors including the position of the
// incorrect bytes. Kill the padding oracle by lumping everything into
// a generic error.
return "", syscall.EBADMSG
}
// A name can never contain a null byte or "/". Make sure we never return those
- // to the user, even when we read a corrupted (or fuzzed) filesystem.
+ // to the kernel, even when we read a corrupted (or fuzzed) filesystem.
if bytes.Contains(bin, []byte{0}) || bytes.Contains(bin, []byte("/")) {
return "", syscall.EBADMSG
}
diff --git a/internal/nametransform/names_test.go b/internal/nametransform/names_test.go
index d772af2..0254777 100644
--- a/internal/nametransform/names_test.go
+++ b/internal/nametransform/names_test.go
@@ -32,3 +32,20 @@ func TestPad16(t *testing.T) {
}
}
}
+
+// TestUnpad16Garbage - unPad16 should never crash on corrupt or malicious inputs
+func TestUnpad16Garbage(t *testing.T) {
+ var testCases [][]byte
+ testCases = append(testCases, make([]byte, 0))
+ testCases = append(testCases, make([]byte, 16))
+ testCases = append(testCases, make([]byte, 1))
+ testCases = append(testCases, make([]byte, 17))
+ testCases = append(testCases, bytes.Repeat([]byte{16}, 16))
+ testCases = append(testCases, bytes.Repeat([]byte{17}, 16))
+ for _, v := range testCases {
+ _, err := unPad16([]byte(v))
+ if err == nil {
+ t.Fail()
+ }
+ }
+}
diff --git a/internal/nametransform/pad16.go b/internal/nametransform/pad16.go
index 2b30bcb..833be0e 100644
--- a/internal/nametransform/pad16.go
+++ b/internal/nametransform/pad16.go
@@ -31,6 +31,9 @@ func pad16(orig []byte) (padded []byte) {
// unPad16 - remove padding
func unPad16(padded []byte) ([]byte, error) {
oldLen := len(padded)
+ if oldLen == 0 {
+ return nil, errors.New("Empty input")
+ }
if oldLen%aes.BlockSize != 0 {
return nil, errors.New("Unaligned size")
}
@@ -39,12 +42,16 @@ func unPad16(padded []byte) ([]byte, error) {
// The padding byte's value is the padding length
padLen := int(padByte)
// Padding must be at least 1 byte
- if padLen <= 0 {
+ if padLen == 0 {
return nil, errors.New("Padding cannot be zero-length")
}
- // Larger paddings make no sense
+ // Padding more than 16 bytes make no sense
if padLen > aes.BlockSize {
- return nil, fmt.Errorf("Padding too long, padLen = %d > 16", padLen)
+ return nil, fmt.Errorf("Padding too long, padLen=%d > 16", padLen)
+ }
+ // Padding cannot be as long as (or longer than) the whole string,
+ if padLen >= oldLen {
+ return nil, fmt.Errorf("Padding too long, oldLen=%d >= padLen=%d", oldLen, padLen)
}
// All padding bytes must be identical
for i := oldLen - padLen; i < oldLen; i++ {
@@ -53,9 +60,5 @@ func unPad16(padded []byte) ([]byte, error) {
}
}
newLen := oldLen - padLen
- // Padding an empty string makes no sense
- if newLen == 0 {
- return nil, errors.New("Unpadded length is zero")
- }
return padded[0:newLen], nil
}