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.
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
Fixes https://github.com/rfjakob/gocryptfs/issues/168
Steps to reproduce the problem:
* Create a regular reverse mount point
* Create files with the same very long name in multiple directories - so far
everything works as expected, and it will appear with a different name each
time, for example, gocryptfs.longname.A in directory A and
gocryptfs.longname.B in directory B
* Try to access a path with A/gocryptfs.longname.B or B/gocryptfs.longname.A -
this should fail, but it actually works.
The problem is that the longname cache only uses the path as key and not the
dir or divIV. Assume an attacker can directly interact with a reverse mount and
knows the relation longname path -> unencoded path in one directory, it allows
to test if the same unencoded filename appears in any other directory.
Fixes https://github.com/rfjakob/gocryptfs/issues/171
Steps to reproduce:
* Create a regular forward mount point
* Create a new directory in the mount point
* Manually delete the gocryptfs.diriv file from the corresponding ciphertext
directory
* Attempt to delete the directory with 'rmdir <dirname>'
Although the code explicitly checks for empty directories, it will still attempt
to move the non-existent gocryptfs.diriv file and fails with:
rmdir: failed to remove '<dirname>': No such file or directory
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.
Allows to use /dev/random for generating the master key instead of the
default Go implementation. When the kernel random generator has been
properly initialized both are considered equally secure, however:
* Versions of Go prior to 1.9 just fall back to /dev/urandom if the
getrandom() syscall would be blocking (Go Bug #19274)
* Kernel versions prior to 3.17 do not support getrandom(), and there
is no check if the random generator has been properly initialized
before reading from /dev/urandom
This is especially useful for embedded hardware with low-entroy. Please
note that generation of the master key might block indefinitely if the
kernel cannot harvest enough entropy.
At the moment, it does two things:
1. Disable stat() caching so changes to the backing storage show up
immediately.
2. Disable hard link tracking, as the inode numbers on the backing
storage are not stable when files are deleted and re-created behind
our back. This would otherwise produce strange "file does not exist"
and other errors.
Mitigates https://github.com/rfjakob/gocryptfs/issues/156
...this fails in a thousand ways:
[...]
vendor/golang.org/x/crypto/sha3/keccakf_amd64.s:324: [amd64] keccakF1600: unknown variable state; offset 0 is a+0(FP)
vendor/golang.org/x/crypto/ssh/certs.go:172: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/certs.go:166
vendor/golang.org/x/crypto/ssh/certs.go:187: declaration of "rest" shadows declaration at vendor/golang.org/x/crypto/ssh/certs.go:161
vendor/golang.org/x/crypto/ssh/certs.go:187: declaration of "ok" shadows declaration at vendor/golang.org/x/crypto/ssh/certs.go:161
vendor/golang.org/x/crypto/ssh/client_auth.go:226: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/client_auth.go:193
vendor/golang.org/x/crypto/ssh/client_auth.go:394: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/client_auth.go:380
vendor/golang.org/x/crypto/ssh/client_auth.go:405: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/client_auth.go:380
vendor/golang.org/x/crypto/ssh/handshake.go:566: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/handshake.go:547
vendor/golang.org/x/crypto/ssh/handshake.go:592: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/handshake.go:547
vendor/golang.org/x/crypto/ssh/handshake.go:630: declaration of "err" shadows declaration at vendor/golang.org/x/crypto/ssh/handshake.go:620
[...]
From https://github.com/rfjakob/gocryptfs/issues/150:
mkdir a
mkdir a/b
gocryptsfs -init -reverse a/
gocryptfs -reverse a/ a/b
Now directory a/b/ contains encrypted view of 'a' but it
is possible to descend into encrypted version of b (e.g.
a/b/43873uhj538765387/) which contains double encrypted
'a' and so on.
Reported-by: https://github.com/tigmac
"go vet" on Go 1.8 and older does not support flags:
$ go version
go version go1.8.3 linux/amd64
$ ./test.bash
gocryptfs v1.4.1-27-g8c1b363 without_openssl; go-fuse v20170619-21-gcf21bc2; 2017-10-22 go1.8.3
gocryptfs v1.4.1-27-g8c1b363; go-fuse v20170619-21-gcf21bc2; 2017-10-22 go1.8.3
flag provided but not defined: -all
usage: vet [-n] [-x] [build flags] [packages]
Vet runs the Go vet command on the packages named by the import paths.
For more about vet, see 'go doc cmd/vet'.
For more about specifying packages, see 'go help packages'.
To run the vet tool with specific options, run 'go tool vet'.
The -n flag prints commands that would be executed.
The -x flag prints commands as they are executed.
For more about build flags, see 'go help build'.
See also: go fmt, go fix.
This reverts commit a1170be979.
Disable hard link tracking to avoid strange breakage on duplicate
inode numbers ( https://github.com/rfjakob/gocryptfs/issues/149 ).
Reverse mode is read-only, so we don't need a working link().
...to account for unaligned reads.
I have not seen this happen in the wild because the kernel
always seems to issue 4k-aligned requests. But the cost
of the additional block in the pool is low and prevents
a buffer overrun panic when an unaligned read does happen.
Our byte cache pools are sized acc. to MAX_KERNEL_WRITE, but the
running kernel may have a higher limit set. Clamp to what we can
handle.
Fixes a panic on a Synology NAS reported at
https://github.com/rfjakob/gocryptfs/issues/145
The extended TestLongnameStat() exposes a pathological case
when run on ext4, as ext4 reuses inode numbers immediately.
This change modifies the test to not delete the files immediately,
so the inode numbers cannot be reused immediately.
Fix for the underlying issue is a TODO.
A file with a name of exactly 176 bytes length caused this error:
ls: cannot access ./tmp/dsg/sXSGJLTuZuW1FarwIkJs0w/b6mGjdxIRpaeanTo0rbh0A/QjMRrQZC_4WLhmHI1UOBcA/gocryptfs.longname.QV-UipdDXeUVdl05WruoEzBNPrQCfpu6OzJL0_QnDKY: No such file or directory
ls: cannot access ./tmp/dsg/sXSGJLTuZuW1FarwIkJs0w/b6mGjdxIRpaeanTo0rbh0A/QjMRrQZC_4WLhmHI1UOBcA/gocryptfs.longname.QV-UipdDXeUVdl05WruoEzBNPrQCfpu6OzJL0_QnDKY.name: No such file or directory
-????????? ? ? ? ? ? gocryptfs.longname.QV-UipdDXeUVdl05WruoEzBNPrQCfpu6OzJL0_QnDKY
-????????? ? ? ? ? ? gocryptfs.longname.QV-UipdDXeUVdl05WruoEzBNPrQCfpu6OzJL0_QnDKY.name
Root cause was a wrong shortNameMax constant that failed to
account for the obligatory padding byte.
Fix the constant and also expand the TestLongnameStat test case
to test ALL file name lengths from 1-255 bytes.
Fixes https://github.com/rfjakob/gocryptfs/issues/143 .
The encrypt and decrypt path both had a copy that were equivalent
but ordered differently, which was confusing.
Consolidate it in a new dedicated function.
MacOS creates lots of these files, and if the directory is otherwise
empty, we would throw an IO error to the unsuspecting user.
With this patch, we log a warning, but otherwise pretend we did not
see it.
Mitigates https://github.com/rfjakob/gocryptfs/issues/140
...and if Getdents is not available at all.
Due to this warning I now know that SSHFS always returns DT_UNKNOWN:
gocryptfs[8129]: Getdents: convertDType: received DT_UNKNOWN, falling back to Lstat
This behavoir is confirmed at http://ahefner.livejournal.com/16875.html:
"With sshfs, I finally found that obscure case. The dtype is always set to DT_UNKNOWN [...]"
The exit codes have been documented in CLI_ABI.md for a while,
but they should also be listed in the man page.
Also fix the rendering of "[-o COMMA-SEPARATED-OPTIONS]", where
the square brackets where interpreted as something. Escape all
square brackets to be safe.
