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authorJakob Unterwurzacher2021-06-02 14:21:30 +0200
committerJakob Unterwurzacher2021-06-02 14:29:48 +0200
commit04858ddd222bbf7156f33f99cfb293a9b1e15ec8 (patch)
tree732cbf83c9d842a911d515abbad7c153c4159354 /internal/nametransform
parent242cdf966f262b2e20785eb0ff49ac55a8bd4636 (diff)
nametransform: check name validity on encryption
xfstests generic/523 discovered that we allowed to set xattrs with "/" in the name, but did not allow to read them later. With this change we do not allow to set them in the first place.
Diffstat (limited to 'internal/nametransform')
-rw-r--r--internal/nametransform/diriv.go5
-rw-r--r--internal/nametransform/longnames.go5
-rw-r--r--internal/nametransform/names.go27
-rw-r--r--internal/nametransform/names_test.go24
-rw-r--r--internal/nametransform/valid.go27
5 files changed, 70 insertions, 18 deletions
diff --git a/internal/nametransform/diriv.go b/internal/nametransform/diriv.go
index b2f165b..1d27aa5 100644
--- a/internal/nametransform/diriv.go
+++ b/internal/nametransform/diriv.go
@@ -102,7 +102,10 @@ func (be *NameTransform) EncryptAndHashName(name string, iv []byte) (string, err
if len(name) > NameMax {
return "", syscall.ENAMETOOLONG
}
- cName := be.EncryptName(name, iv)
+ cName, err := be.EncryptName(name, iv)
+ if err != nil {
+ return "", err
+ }
if be.longNames && len(cName) > NameMax {
return be.HashLongName(cName), nil
}
diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
index aa463a1..74ddb07 100644
--- a/internal/nametransform/longnames.go
+++ b/internal/nametransform/longnames.go
@@ -132,7 +132,10 @@ func (n *NameTransform) WriteLongNameAt(dirfd int, hashName string, plainName st
if err != nil {
return err
}
- cName := n.EncryptName(plainName, dirIV)
+ cName, err := n.EncryptName(plainName, dirIV)
+ if err != nil {
+ return err
+ }
// Write the encrypted name into hashName.name
fdRaw, err := syscallcompat.Openat(dirfd, hashName+LongNameSuffix,
diff --git a/internal/nametransform/names.go b/internal/nametransform/names.go
index 119d592..ca28230 100644
--- a/internal/nametransform/names.go
+++ b/internal/nametransform/names.go
@@ -2,7 +2,6 @@
package nametransform
import (
- "bytes"
"crypto/aes"
"encoding/base64"
"path/filepath"
@@ -21,7 +20,7 @@ const (
// NameTransformer is an interface used to transform filenames.
type NameTransformer interface {
DecryptName(cipherName string, iv []byte) (string, error)
- EncryptName(plainName string, iv []byte) string
+ EncryptName(plainName string, iv []byte) (string, error)
EncryptAndHashName(name string, iv []byte) (string, error)
// HashLongName - take the hash of a long string "name" and return
// "gocryptfs.longname.[sha256]"
@@ -99,22 +98,14 @@ 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 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.
+ tlog.Warn.Printf("DecryptName %q: unPad16 error: %v", cipherName, err)
return "", syscall.EBADMSG
}
- // A name can never contain a null byte or "/". Make sure we never return those
- // 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
- }
- // The name should never be "." or "..".
- if bytes.Equal(bin, []byte(".")) || bytes.Equal(bin, []byte("..")) {
+ plain := string(bin)
+ if err := IsValidName(plain); err != nil {
+ tlog.Warn.Printf("DecryptName %q: invalid name after decryption: %v", cipherName, err)
return "", syscall.EBADMSG
}
- plain := string(bin)
return plain, err
}
@@ -123,12 +114,16 @@ func (n *NameTransform) decryptName(cipherName string, iv []byte) (string, error
//
// This function is exported because in some cases, fusefrontend needs access
// to the full (not hashed) name if longname is used.
-func (n *NameTransform) EncryptName(plainName string, iv []byte) (cipherName64 string) {
+func (n *NameTransform) EncryptName(plainName string, iv []byte) (cipherName64 string, err error) {
+ if err := IsValidName(plainName); err != nil {
+ tlog.Warn.Printf("EncryptName %q: invalid plainName: %v", plainName, err)
+ return "", syscall.EBADMSG
+ }
bin := []byte(plainName)
bin = pad16(bin)
bin = n.emeCipher.Encrypt(iv, bin)
cipherName64 = n.B64.EncodeToString(bin)
- return cipherName64
+ return cipherName64, nil
}
// B64EncodeToString returns a Base64-encoded string
diff --git a/internal/nametransform/names_test.go b/internal/nametransform/names_test.go
index 9d77c2d..b4e98d4 100644
--- a/internal/nametransform/names_test.go
+++ b/internal/nametransform/names_test.go
@@ -2,6 +2,7 @@ package nametransform
import (
"bytes"
+ "strings"
"testing"
)
@@ -51,3 +52,26 @@ func TestUnpad16Garbage(t *testing.T) {
}
}
}
+
+func TestIsValidName(t *testing.T) {
+ cases := []struct {
+ in string
+ want bool
+ }{
+ {"", false},
+ {".", false},
+ {"..", false},
+ {"...", true},
+ {"asdasd/asdasd", false},
+ {"asdasd\000asdasd", false},
+ {"hello", true},
+ {strings.Repeat("x", 255), true},
+ {strings.Repeat("x", 256), false},
+ }
+ for _, c := range cases {
+ have := IsValidName(c.in)
+ if (have == nil) != c.want {
+ t.Errorf("IsValidName(%q): want %v have %v", c.in, c.want, have)
+ }
+ }
+}
diff --git a/internal/nametransform/valid.go b/internal/nametransform/valid.go
new file mode 100644
index 0000000..b991074
--- /dev/null
+++ b/internal/nametransform/valid.go
@@ -0,0 +1,27 @@
+package nametransform
+
+import (
+ "fmt"
+ "strings"
+)
+
+// IsValidName checks if `name` is a valid name for a normal file
+// (does not contain null bytes or "/" etc...).
+func IsValidName(name string) error {
+ if name == "" {
+ return fmt.Errorf("empty input")
+ }
+ if len(name) > NameMax {
+ return fmt.Errorf("too long")
+ }
+ // A name can never contain a null byte or "/". Make sure we never return those
+ // to the kernel, even when we read a corrupted (or fuzzed) filesystem.
+ if strings.Contains(name, "\000") || strings.Contains(name, "/") {
+ return fmt.Errorf("contains forbidden bytes")
+ }
+ // The name should never be "." or "..".
+ if name == "." || name == ".." {
+ return fmt.Errorf(". and .. are forbidden names")
+ }
+ return nil
+}