Notice

This document is for a development version of Ceph.

Authentication and ACLs

Requests to the RADOS Gateway (RGW) can be either authenticated or unauthenticated. RGW assumes unauthenticated requests are sent by an anonymous user. RGW supports canned ACLs.

Authentication

Authenticating a request requires including an access key and a Hash-based Message Authentication Code (HMAC) in the request before it is sent to the RGW server. RGW uses an S3-compatible authentication approach.

HTTP/1.1
PUT /buckets/bucket/object.mpeg
Host: cname.domain.com
Date: Mon, 2 Jan 2012 00:01:01 +0000
Content-Encoding: mpeg
Content-Length: 9999999

Authorization: AWS {access-key}:{hash-of-header-and-secret}

In the foregoing example, replace {access-key} with the value for your access key ID followed by a colon (:). Replace {hash-of-header-and-secret} with a hash of the header string and the secret corresponding to the access key ID.

To generate the hash of the header string and secret, you must:

  1. Get the value of the header string.

  2. Normalize the request header string into canonical form.

  3. Generate an HMAC using a SHA-1 hashing algorithm. See RFC 2104 and HMAC for details.

  4. Encode the hmac result as base-64.

To normalize the header into canonical form:

  1. Get all fields beginning with x-amz-.

  2. Ensure that the fields are all lowercase.

  3. Sort the fields lexicographically.

  4. Combine multiple instances of the same field name into a single field and separate the field values with a comma.

  5. Replace white space and line breaks in field values with a single space.

  6. Remove white space before and after colons.

  7. Append a new line after each field.

  8. Merge the fields back into the header.

Replace the {hash-of-header-and-secret} with the base-64 encoded HMAC string.

Authentication against OpenStack Keystone

In a radosgw instance that is configured with authentication against OpenStack Keystone, it is possible to use Keystone as an authoritative source for S3 API authentication. To do so, you must set:

In addition, a user wishing to use the S3 API must obtain an AWS-style access key and secret key. They can do so with the openstack ec2 credentials create command:

$ openstack --os-interface public ec2 credentials create
+------------+---------------------------------------------------------------------------------------------------------------------------------------------+
| Field      | Value                                                                                                                                       |
+------------+---------------------------------------------------------------------------------------------------------------------------------------------+
| access     | c921676aaabbccdeadbeef7e8b0eeb2c                                                                                                            |
| links      | {u'self': u'https://auth.example.com:5000/v3/users/7ecbebaffeabbddeadbeefa23267ccbb24/credentials/OS-EC2/c921676aaabbccdeadbeef7e8b0eeb2c'} |
| project_id | 5ed51981aab4679851adeadbeef6ebf7                                                                                                            |
| secret     | ********************************                                                                                                            |
| trust_id   | None                                                                                                                                        |
| user_id    | 7ecbebaffeabbddeadbeefa23267cc24                                                                                                            |
+------------+---------------------------------------------------------------------------------------------------------------------------------------------+

The thus-generated access and secret key can then be used for S3 API access to radosgw.

Note

Consider that most production radosgw deployments authenticating against OpenStack Keystone are also set up for RGW Multi-tenancy, for which special considerations apply with respect to S3 signed URLs and public read ACLs.

Access Control Lists (ACLs)

RGW supports S3-compatible ACL functionality. An ACL is a list of access grants that specify which operations a user can perform on a bucket or on an object. Each grant has a different meaning when applied to a bucket versus applied to an object:

Permission

Bucket

Object

READ

Grantee can list the objects in the bucket.

Grantee can read the object.

WRITE

Grantee can write or delete objects in the bucket.

N/A

READ_ACP

Grantee can read bucket ACL.

Grantee can read the object ACL.

WRITE_ACP

Grantee can write bucket ACL.

Grantee can write to the object ACL.

FULL_CONTROL

Grantee has full permissions for object in the bucket.

Grantee can read or write to the object ACL.

Internally, S3 operations are mapped to ACL permissions thus:

Operation

Permission

s3:GetObject

READ

s3:GetObjectTorrent

READ

s3:GetObjectVersion

READ

s3:GetObjectVersionTorrent

READ

s3:GetObjectTagging

READ

s3:GetObjectVersionTagging

READ

s3:ListAllMyBuckets

READ

s3:ListBucket

READ

s3:ListBucketMultipartUploads

READ

s3:ListBucketVersions

READ

s3:ListMultipartUploadParts

READ

s3:AbortMultipartUpload

WRITE

s3:CreateBucket

WRITE

s3:DeleteBucket

WRITE

s3:DeleteObject

WRITE

s3:s3DeleteObjectVersion

WRITE

s3:PutObject

WRITE

s3:PutObjectTagging

WRITE

s3:PutObjectVersionTagging

WRITE

s3:DeleteObjectTagging

WRITE

s3:DeleteObjectVersionTagging

WRITE

s3:RestoreObject

WRITE

s3:GetAccelerateConfiguration

READ_ACP

s3:GetBucketAcl

READ_ACP

s3:GetBucketCORS

READ_ACP

s3:GetBucketLocation

READ_ACP

s3:GetBucketLogging

READ_ACP

s3:GetBucketNotification

READ_ACP

s3:GetBucketPolicy

READ_ACP

s3:GetBucketRequestPayment

READ_ACP

s3:GetBucketTagging

READ_ACP

s3:GetBucketVersioning

READ_ACP

s3:GetBucketWebsite

READ_ACP

s3:GetLifecycleConfiguration

READ_ACP

s3:GetObjectAcl

READ_ACP

s3:GetObjectVersionAcl

READ_ACP

s3:GetReplicationConfiguration

READ_ACP

s3:GetBucketEncryption

READ_ACP

s3:DeleteBucketPolicy

WRITE_ACP

s3:DeleteBucketWebsite

WRITE_ACP

s3:DeleteReplicationConfiguration

WRITE_ACP

s3:PutAccelerateConfiguration

WRITE_ACP

s3:PutBucketAcl

WRITE_ACP

s3:PutBucketCORS

WRITE_ACP

s3:PutBucketLogging

WRITE_ACP

s3:PutBucketNotification

WRITE_ACP

s3:PutBucketPolicy

WRITE_ACP

s3:PutBucketRequestPayment

WRITE_ACP

s3:PutBucketTagging

WRITE_ACP

s3:PutPutBucketVersioning

WRITE_ACP

s3:PutBucketWebsite

WRITE_ACP

s3:PutLifecycleConfiguration

WRITE_ACP

s3:PutObjectAcl

WRITE_ACP

s3:PutObjectVersionAcl

WRITE_ACP

s3:PutReplicationConfiguration

WRITE_ACP

s3:PutBucketEncryption

WRITE_ACP

Some mappings, (e.g. s3:CreateBucket to WRITE) are not applicable to S3 operation, but are required to allow Swift and S3 to access the same resources when things like Swift user ACLs are in play. This is one of the many reasons that you should use S3 bucket policies rather than S3 ACLs when possible.