[ceph-users] radosgw, Keystone integration, and the S3 API

Florian Haas florian at citynetwork.eu
Mon Nov 19 07:23:06 PST 2018


Hi everyone,

I've recently started a documentation patch to better explain Swift
compatibility and OpenStack integration for radosgw; a WIP PR is at
https://github.com/ceph/ceph/pull/25056/. I have, however, run into an
issue that I would really *like* to document, except I don't know
whether what I'm seeing is how things are supposed to work. :)

This is about multi-tenancy in radosgw, in combination with S3
authentication via Keystone (and EC2-compatible credentials generated
from OpenStack, as explained in my doc patch). Now, when I enable
rgw_s3_use_keystone_auth and rgw_keystone_implicit_tenants, then, if I
create an S3 bucket in radosgw for the first time, naming that bucket
"foo", the following things happen:

* I see a user that has been created, and that I can query with
  "radosgw-admin user info", that is named
  ff569d377ecb4f77875fa1b3f89eb16f$ff569d377ecb4f77875fa1b3f89eb16f
  (that is, the Keystone tenant/project UUID twice[1], separated by a $
  character). Its display_name is the name of my tenant.

* With "radosgw-admin bucket list
--uid='ff569d377ecb4f77875fa1b3f89eb16f$ff569d377ecb4f77875fa1b3f89eb16f'",
  I see a bucket that has been created, and that has been named "foo".

So far, all is well. If I do this, then I can see an bucket named
"foo" if I use an S3 client, and I can see a container named "foo",
with identical content, if I use the Swift API.

Now, if I enable rgw_swift_account_in_url, and update my Keystone
object store endpoint to include AUTH_%(tenant_id)s, then using the
Swift API I can also use public ACLs and temp URLs.

However, I am stumped trying to to understand how exactly this is meant
to work with the S3 API.

So I have two questions:

(1) What do I have to do to get publicly-readable buckets to work in
    the Keystone-authenticated scenario? Moreover, what is the correct
    path to use, for a non-S3 client like curl or a browser, to access
    an object? It seems that using
    http://host:port/ff569d377ecb4f77875fa1b3f89eb16f:foo/bar works
    for S3 objects with a public ACL set, but if I try to use the same
    approach with a signed object, I get a 403 with
    SignatureDoesNotMatch. It seems like what I have to use for a
    signed object is, instead,

http://host:port/foo/bar?AWSAccessKeyId=something&Expires=something&Signature=something.
    However, if I do *ask* for a signed object that includes the
    tenant name, as in "s3cmd signurl
    s3://5ed51981f4a8468292bf2c578806ebf:foo/bar +120", then I *can*
    use the same URL format as for public ACL objects. Is this the
    intended behavior? If so, does that mean that an application
    using the S3 API, and access/secret keys from OpenStack-backed
    EC2, should configure always itself to use the "<tenant_id>:"
    prefix to precede the bucket name?

(2) Do I understand the documentation
    (http://docs.ceph.com/docs/mimic/radosgw/multitenancy/#s3)
    correctly in that whenever one uses multitenancy of any kind in
    radosgw, S3 bucket hostnames can't ever be used? Thus, is it correct
    to say that if a radosgw instance is meant to *only* ever
    authenticate its users against Keystone, where there is always a
    radosgw tenant that is being created, then it's pointless to set
    rgw_dns_name?


If anyone could shed a light on the above, I can write up the answer and
amend the doc patch. Thanks!

Cheers,
Florian


[1] This would be an additional question: why is the project UUID in
there *twice*? Surely there's a good cause for that, but it presently
escapes me. http://docs.ceph.com/docs/master/radosgw/multitenancy/ says
"TBD – don’t forget to explain the function of rgw keystone implicit
tenants = true" here, which isn't very helpful. :)


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