The function used to do two things:
1) Walk the directory tree in a manner safe from symlink attacks
2) Open the final component in the mode requested by the caller
This change drops (2), which was only used once, and lets the caller
handle it. This simplifies the function and makes it fit for reuse in
forward mode in openBackingPath(), and for using O_PATH on Linux.
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.
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 .
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.
A directory with a long name has two associated virtual files:
the .name file and the .diriv files.
These used to get the same inode number:
$ ls -di1 * */*
33313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw
1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw/gocryptfs.diriv
1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw.name
With this change we use another prefix (2 instead of 1) for .name files.
$ ls -di1 * */*
33313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw
1000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw/gocryptfs.diriv
2000000000033313535 gocryptfs.longname.2togDFouca9mrTwtfF1RNW5DZRAQY8alaR7wO_Xd5Zw.name
This PR addresses the Issue #95, about "Confusing file owner for
longname files in reverse mode".
It affects only the reverse mode, and introduces two
modifications:
1) The "gocryptfs.longname.XXXX.name" files are assigned the owner and
group of the underlying plaintext file. Therefore it is consistent
with the file "gocryptfs.longname.XXXX" that has the encrypted
contents of the plaintext file.
2) The two virtual files mentioned above are given -r--r--r--
permissions. This is consistent with the behavior described in
function Access in internal/fusefrontend_reverse/rfs.go where all
virtual files are always readable. Behavior also observed in point
c) in #95 .
Issue #95 URL: https://github.com/rfjakob/gocryptfs/issues/95
Pull request URL: https://github.com/rfjakob/gocryptfs/pull/97
This could have caused spurious ENOENT errors.
That it did not cause these errors all the time is interesting
and probably because an earlier readdir would place the entry
in the cache. This masks the bug.
$ 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 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.
Jakob Unterwurzacher