* extend the diriv cache to 100 entries
* add special handling for the immutable root diriv
The better cache allows to shed some complexity from the path
encryption logic (parent-of-parent check).
Mitigates https://github.com/rfjakob/gocryptfs/issues/127
Dir is like filepath.Dir but returns "" instead of ".".
This was already implemented in fusefrontend_reverse as saneDir().
We will need it in nametransform for the improved diriv caching.
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.
When a user calls into a deep directory hierarchy, we often
get a sequence like this from the kernel:
LOOKUP a
LOOKUP a/b
LOOKUP a/b/c
LOOKUP a/b/c/d
The diriv cache was not effective for this pattern, because it
was designed for this:
LOOKUP a/a
LOOKUP a/b
LOOKUP a/c
LOOKUP a/d
By also using the cached entry of the grandparent we can avoid lots
of diriv reads.
This benchmark is against a large encrypted directory hosted on NFS:
Before:
$ time ls -R nfs-backed-mount > /dev/null
real 1m35.976s
user 0m0.248s
sys 0m0.281s
After:
$ time ls -R nfs-backed-mount > /dev/null
real 1m3.670s
user 0m0.217s
sys 0m0.403s
As reported at https://github.com/rfjakob/gocryptfs/issues/105 ,
the "ioutil.WriteFile(file, iv, 0400)" call causes "permissions denied"
errors on an NFSv4 setup.
"strace"ing diriv creation and gocryptfs.conf creation shows this:
conf (works on the user's NFSv4 mount):
openat(AT_FDCWD, "/tmp/a/gocryptfs.conf.tmp", O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0400) = 3
diriv (fails):
openat(AT_FDCWD, "/tmp/a/gocryptfs.diriv", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0400) = 3
This patch creates the diriv file with the same flags that are used for
creating the conf:
openat(AT_FDCWD, "/tmp/a/gocryptfs.diriv", O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0400) = 3
Closes https://github.com/rfjakob/gocryptfs/issues/105
Version 1.1 of the EME package (github.com/rfjakob/eme) added
a more convenient interface. Use it.
Note that you have to upgrade your EME package (go get -u)!
$ golint ./... | grep -v underscore | grep -v ALL_CAPS
internal/fusefrontend_reverse/rfs.go:52:36: exported func NewFS returns unexported type *fusefrontend_reverse.reverseFS, which can be annoying to use
internal/nametransform/raw64_go1.5.go:10:2: exported const HaveRaw64 should have comment (or a comment on this block) or be unexported
The Back In Time backup tool (https://github.com/bit-team/backintime)
wants to write directly into the ciphertext dir.
This may cause the cached directory IV to become out-of-date.
Having an expiry time limits the inconstency to one second, like
attr_timeout does for the kernel getattr cache.
The last patch added functionality for generating gocryptfs.longname.*
files, this patch adds support for mapping them back to the full
filenames.
Note that resolving a long name needs a full readdir. A cache
will be implemented later on to improve performance.
As ReadDirIV operates on a path anyway, opening the directory
has no clear safety advantage w.r.t. concurrent renames.
If the backing directory is a reverse-mounted gocryptfs filesystem,
each directory open is an OPENDIR, and this causes a full directory
read!
This patch improves the "ls -lR" performance of an
DIR --> gocryptfs-reverse --> gocryptfs
chain by a factor of ~10.
OPENDIR counts for ls -lR:
Before 15570
After 2745
unPad16 returns detailed errors including the position of the
incorrect bytes. Kill a possible padding oracle by lumping
everything into a generic error.
The detailed error is only logged if debug is active.
tlog is used heavily everywhere and deserves a shorter name.
Renamed using sed magic, without any manual rework:
find * -type f -exec sed -i 's/toggledlog/tlog/g' {} +
