Add checksum to object extended attributes

Currently, our integrity checking for objects is pretty weak when it
comes to object metadata. If the extended attributes on a .data or
.meta file get corrupted in such a way that we can still unpickle it,
we don't have anything that detects that.

This could be especially bad with encrypted etags; if the encrypted
etag (X-Object-Sysmeta-Crypto-Etag or whatever it is) gets some bits
flipped, then we'll cheerfully decrypt the cipherjunk into plainjunk,
then send it to the client. Net effect is that the client sees a GET
response with an ETag that doesn't match the MD5 of the object *and*
Swift has no way of detecting and quarantining this object.

Note that, with an unencrypted object, if the ETag metadatum gets
mangled, then the object will be quarantined by the object server or
auditor, whichever notices first.

As part of this commit, I also ripped out some mocking of
getxattr/setxattr in tests. It appears to be there to allow unit tests
to run on systems where /tmp doesn't support xattrs. However, since
the mock is keyed off of inode number and inode numbers get re-used,
there's lots of leakage between different test runs. On a real FS,
unlinking a file and then creating a new one of the same name will
also reset the xattrs; this isn't the case with the mock.

The mock was pretty old; Ubuntu 12.04 and up all support xattrs in
/tmp, and recent Red Hat / CentOS releases do too. The xattr mock was
added in 2011; maybe it was to support Ubuntu Lucid Lynx?

Bonus: now you can pause a test with the debugger, inspect its files
in /tmp, and actually see the xattrs along with the data.

Since this patch now uses a real filesystem for testing filesystem
operations, tests are skipped if the underlying filesystem does not
support setting xattrs (eg tmpfs or more than 4k of xattrs on ext4).

References to "/tmp" have been replaced with calls to
tempfile.gettempdir(). This will allow setting the TMPDIR envvar in
test setup and getting an XFS filesystem instead of ext4 or tmpfs.

THIS PATCH SIGNIFICANTLY CHANGES TESTING ENVIRONMENTS

With this patch, every test environment will require TMPDIR to be
using a filesystem that supports at least 4k of extended attributes.
Neither ext4 nor tempfs support this. XFS is recommended.

So why all the SkipTests? Why not simply raise an error? We still need
the tests to run on the base image for OpenStack's CI system. Since
we were previously mocking out xattr, there wasn't a problem, but we
also weren't actually testing anything. This patch adds functionality
to validate xattr data, so we need to drop the mock.

`test.unit.skip_if_no_xattrs()` is also imported into `test.functional`
so that functional tests can import it from the functional test
namespace.

The related OpenStack CI infrastructure changes are made in
https://review.openstack.org/#/c/394600/.

Co-Authored-By: John Dickinson <me@not.mn>

Change-Id: I98a37c0d451f4960b7a12f648e4405c6c6716808

1 files changed, 6 insertions, 0 deletions

diff --git a/README.rst b/README.rst
index 6a5a1443d..529dfb855 100644
--- a/README.rst
+++ b/README.rst
@@ -82,6 +82,12 @@ You can run unit tests with ``.unittests``, functional tests with
 ``.functests``, and probe tests with ``.probetests``. There is an
 additional ``.alltests`` script that wraps the other three.
 
+To fully run the tests, the target environment must use a filesystem that
+supports large xattrs. XFS is strongly recommended. For unit tests and in-
+process functional tests, either mount ``/tmp`` with XFS or provide another
+XFS filesystem via the ``TMPDIR`` environment variable. Without this setting,
+tests should still pass, but a very large number will be skipped.
+
 Code Organization
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