If the user manages to replace the directory with
a symlink at just the right time, we could be tricked
into chown'ing the wrong file.
This change fixes the race by using fchownat, which
unfortunately is not available on darwin, hence a compat
wrapper is added.
Scenario, as described by @slackner at
https://github.com/rfjakob/gocryptfs/issues/177 :
1. Create a forward mount point with `plaintextnames` enabled
2. Mount as root user with `allow_other`
3. For testing purposes create a file `/tmp/file_owned_by_root`
which is owned by the root user
4. As a regular user run inside of the GoCryptFS mount:
```
mkdir tempdir
mknod tempdir/file_owned_by_root p &
mv tempdir tempdir2
ln -s /tmp tempdir
```
When the steps are done fast enough and in the right order
(run in a loop!), the device file will be created in
`tempdir`, but the `lchown` will be executed by following
the symlink. As a result, the ownership of the file located
at `/tmp/file_owned_by_root` will be changed.
Fixes https://github.com/rfjakob/gocryptfs/issues/170
Steps to reproduce the problem:
* Create a regular forward mount point
* Create a file with a shortname and one with a long filename
* Try to run 'mv <shortname> <longname>'
This should actually work and replace the existing file, but instead it
fails with:
mv: cannot move '<shortname>' to '<longname>': File exists
The problem is the creation of the .name file. If the target already exists
we can safely ignore the EEXIST error and just keep the existing .name file.
Test that we get the right timestamp when extracting a tarball.
Also simplify the workaround in doTestUtimesNano() and fix the
fact that it was running no test at all.
The expected allocated sizes are verified for tmpfs and ext4.
btrfs gives different results, but that's not an error.
Also, simplify test_helpers.Du and several code paths.
Fixes#43.
This should make it work on OSX.
Also, split unmount into two functions. Depending on what you
want,
* UnmountErr returns the resulting error
* UnmountPanic panics if the error was not nil
"go tool vet -shadow=true" complained about the md5 package
being shadowed by variables called "md5".
Fix by using the Md5hex helper and dropping the md5 import.
...and convert all calls to syscall.{Fallocate,Openat}
to syscallcompat .
Both syscalls are not available on OSX. We emulate Openat and just
return EOPNOTSUPP for Fallocate.
We were growing the file block-by-block which was pretty
inefficient. We now coalesce all the grows into a single
Ftruncate. Also simplifies the code!
Simplistic benchmark: Before:
$ time truncate -s 1000M foo
real 0m0.568s
After:
$ time truncate -s 1000M foo
real 0m0.205s
