hardcoresushi/libgocryptfs
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reverse: reject too-long symlink target reads with ENAMETOOLONG

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If the symlink target gets too long due to base64 encoding, we should
return ENAMETOOLONG instead of having the kernel reject the data and
returning an I/O error to the user.

Fixes https://github.com/rfjakob/gocryptfs/issues/167
This commit is contained in:
Jakob Unterwurzacher 2017-11-26 21:27:29 +01:00
parent 90687215a4
commit 1bb47b6796
2 changed files with 28 additions and 0 deletions
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6
internal/fusefrontend_reverse/rfs.go
View File

@ -319,5 +319,11 @@ func (rfs *ReverseFS) Readlink(cipherPath string, context *fuse.Context) (string
// Symlinks are encrypted like file contents and base64-encoded
cBinTarget := rfs.contentEnc.EncryptBlockNonce([]byte(plainTarget), 0, nil, nonce)
cTarget := rfs.nameTransform.B64.EncodeToString(cBinTarget)
// The kernel will reject a symlink target above 4096 chars and return
// and I/O error to the user. Better emit the proper error ourselves.
const PATH_MAX = 4096 // not defined on Darwin
if len(cTarget) > PATH_MAX {
return "", fuse.Status(syscall.ENAMETOOLONG)
}
return cTarget, fuse.OK
}

22
tests/reverse/correctness_test.go
View File

@ -147,3 +147,25 @@ func TestEnoent(t *testing.T) {
t.Errorf("want ENOENT, got: %v", err)
}
}
// If the symlink target gets too long due to base64 encoding, we should
// return ENAMETOOLONG instead of having the kernel reject the data and
// returning an I/O error to the user.
// https://github.com/rfjakob/gocryptfs/issues/167
func TestTooLongSymlink(t *testing.T) {
fn := dirA + "/TooLongSymlink"
target := string(bytes.Repeat([]byte("x"), 4000))
err := os.Symlink(target, fn)
if err != nil {
t.Fatal(err)
}
_, err = os.Readlink(dirC + "/TooLongSymlink")
if err == nil {
return
}
err2 := err.(*os.PathError)
if err2.Err != syscall.ENAMETOOLONG {
t.Errorf("Expected %q error, got %q instead", syscall.ENAMETOOLONG,
err2.Err)
}
}