Cryptographically secure hashes can be forced to be used in a repository,
by setting annex.securehashesonly. This does not prevent the git repository
from containing files with insecure hashes, but it does prevent the content
of such files from being pulled into .git/annex/objects from another
repository.
We want to make sure that at no point does git-annex accept content into
.git/annex/objects that is hashed with an insecure key. Here's how it
was done:
* .git/annex/objects/xx/yy/KEY/ is kept frozen, so nothing can be
written to it normally
* So every place that writes content must call, thawContent or modifyContent.
We can audit for these, and be sure we've considered all cases.
* The main functions are moveAnnex, and linkToAnnex; these were made to
check annex.securehashesonly, and are the main security boundary
for annex.securehashesonly.
* Most other calls to modifyContent deal with other files in the KEY
directory (inode cache etc). The other ones that mess with the content
are:
- Annex.Direct.toDirectGen, in which content already in the
annex directory is moved to the direct mode file, so not relevant.
- fix and lock, which don't add new content
- Command.ReKey.linkKey, which manually unlocks it to make a
copy.
* All other calls to thawContent appear safe.
Made moveAnnex return a Bool, so checked all callsites and made them
deal with a failure in appropriate ways.
linkToAnnex simply returns LinkAnnexFailed; all callsites already deal
with it failing in appropriate ways.
This commit was sponsored by Riku Voipio.
import: --deduplicate and --skip-duplicates were implemented inneficiently;
they unncessarily hashed each file twice. They have been improved to only
hash once.
The new approach is to lock down (minimally) and hash files, and then
reuse that information when importing them.
This was rather tricky, especially in detecting changes to files while
they are being imported.
The output of import changed slightly. While before it silently skipped
over files with eg --skip-duplicates, now it shows each file as it starts
to act on it. Since every file is hashed first thing, it would otherwise
not be clear what file import is chewing on. (Actually, it wasn't clear
before when any of the duplicates switches were used.)
This commit was sponsored by Alexander Thompson on Patreon.
In the case where the pointer file is in place, and not the content
of the object, lock's performNew was called with filemodified=True,
which caused it to try to repopulate the object from an unmodified
associated file, of which there were none. So, the content of the object
got thrown away incorrectly. This was the cause (although not the root
cause) of data loss in https://github.com/datalad/datalad/issues/1020
The same problem could also occur when the work tree file is modified,
but the object is not, and lock is called with --force. Added a test case
for this, since it's excercising the same code path and is easier to set up
than the problem above.
Note that this only occurred when the keys database did not have an inode
cache recorded for the annex object. Normally, the annex object would be in
there, but there are of course circumstances where the inode cache is out
of sync with reality, since it's only a cache.
Fixed by checking if the object is unmodified; if so we don't need to
try to repopulate it. This does add an additional checksum to the unlock
path, but it's already checksumming the worktree file in another case,
so it doesn't slow it down overall.
Further investigation found a similar problem occurred when smudge --clean
is called on a file and the inode cache is not populated. cleanOldKeys
deleted the unmodified old object file in this case. This was also
fixed by checking if the object is unmodified.
In general, use of getInodeCaches and sameInodeCache is potentially
dangerous if the inode cache has not gotten populated for some reason.
Better to use isUnmodified. I breifly auited other places that check the
inode cache, and did not see any immediate problems, but it would be easy
to miss this kind of problem.
When annex.thin is set, adding an object will add the execute bits to the
work tree file, and this does mean that the annex object file ends up
executable.
This doesn't add any complexity that wasn't already present, because git
annex add of an executable file has always ingested it so that the annex
object ends up executable.
But, since an annex object file can be executable or not, when populating
an unlocked file from one, the executable bit is always added or removed
to match the mode of the pointer file.
* add, addurl, import, importfeed: When in a v6 repository on a crippled
filesystem, add files unlocked.
* annex.addunlocked: New configuration setting, makes files always be
added unlocked. (v6 only)
Linking the file to the tmp dir was not necessary in the clean
filter, and it caused the ctime to change, which caused git to think
the file was changed. This caused git status to get slow as it kept
re-cleaning unchanged files.
Fixes several bugs with updates of pointer files. When eg, running
git annex drop --from localremote
it was updating the pointer file in the local repository, not the remote.
Also, fixes drop ../foo when run in a subdir, and probably lots of other
problems. Test suite drops from ~30 to 11 failures now.
TopFilePath is used to force thinking about what the filepath is relative
to.
The data stored in the sqlite db is still just a plain string, and
TopFilePath is a newtype, so there's no overhead involved in using it in
DataBase.Keys.
Decided it's too scary to make v6 unlocked files have 1 copy by default,
but that should be available to those who need it. This is consistent with
git-annex not dropping unused content without --force, etc.
* Added annex.thin setting, which makes unlocked files in v6 repositories
be hard linked to their content, instead of a copy. This saves disk
space but means any modification of an unlocked file will lose the local
(and possibly only) copy of the old version.
* Enable annex.thin by default on upgrade from direct mode to v6, since
direct mode made the same tradeoff.
* fix: Adjusts unlocked files as configured by annex.thin.
This can happen when ingesting a new file in either locked or unlocked
mode, when some unlocked files in the repo use the same key, and the
content was not locally available before.
