Security Model and Operations on S3
The security and permissions model of Amazon S3 is very different from this of a
UNIX-style filesystem: on Amazon S3, operations which query or manipulate permissions are
generally unsupported. Operations to which this applies include:
setfacl. The related attribute commands
setfattr are also unavailable.
In addition, operations which try to preserve permissions (for example
-p) do not preserve permissions.
Although these operations are unsupported, filesystem commands which list permission and user/group details usually simulate these details. As a consequence, when interacting with read-only object stores, the permissions found in “list” and “stat” commands may indicate that the user has write access — when they do not.
Amazon S3 has a permissions model of its own. This model can be manipulated through store-specific tooling. Be aware that some of the permissions which can be set — such as write-only paths, or various permissions on the root path — may be incompatible with the S3A client. It expects full read and write access to the entire bucket with trying to write data, and may fail if it does not have these permissions.
$ hadoop fs -ls s3a://landsat-pds/ Found 10 items drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/L8 -rw-rw-rw- 1 mapred 23764 2015-01-28 18:13 s3a://landsat-pds/index.html drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/landsat-pds_stats -rw-rw-rw- 1 mapred 105 2016-08-19 18:12 s3a://landsat-pds/robots.txt -rw-rw-rw- 1 mapred 38 2016-09-26 12:16 s3a://landsat-pds/run_info.json drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/runs -rw-rw-rw- 1 mapred 27458808 2016-09-26 12:16 s3a://landsat-pds/scene_list.gz drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/tarq drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/tarq_corrupt drwxrwxrwx - mapred 0 2016-09-26 12:16 s3a://landsat-pds/testThe following is evident from the examples:
- All files are listed as having full read/write permissions.
- All directories appear to have full
- The replication count of all files is "1".
- The owner of all files and directories is declared to be the current user
- The timestamp of all directories is actually that of the time the
-lsoperation was executed. This is because these directories are not actual objects in the store; they are simulated directories based on the existence of objects under their paths.
$ hadoop fs -rm s3a://landsat-pds/scene_list.gz rm: s3a://landsat-pds/scene_list.gz: delete on s3a://landsat-pds/scene_list.gz: com.amazonaws.services.s3.model.AmazonS3Exception: Access Denied (Service: Amazon S3; Status Code: 403; Error Code: AccessDenied; Request ID: 1EF98D5957BCAB3D), S3 Extended Request ID: wi3veOXFuFqWBUCJgV3Z+NQVj9gWgZVdXlPU4KBbYMsw/gA+hyhRXcaQ+PogOsDgHh31HlTCebQ=This demonstrates that the listed permissions cannot be taken as evidence of write access. Only object manipulation can determine this.