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https://issues.apache.org/jira/browse/HDFS-8037?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14530446#comment-14530446
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Walter Su commented on HDFS-8037:
---------------------------------
003 patch add unit test. Please review.
> WebHDFS: CheckAccess silently accepts certain malformed FsActions
> -----------------------------------------------------------------
>
> Key: HDFS-8037
> URL: https://issues.apache.org/jira/browse/HDFS-8037
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: webhdfs
> Affects Versions: 2.6.0
> Reporter: Jake Low
> Assignee: Walter Su
> Priority: Minor
> Labels: BB2015-05-TBR, easyfix, newbie
> Attachments: HDFS-8037.001.patch, HDFS-8037.002.patch,
> HDFS-8037.003.patch
>
>
> WebHDFS's {{CHECKACCESS}} operation accepts a parameter called {{fsaction}},
> which represents the type(s) of access to check for.
> According to the documentation, and also the source code, the domain of
> {{fsaction}} is the set of strings matched by the regex {{"\[rwx-\]{3\}"}}.
> This domain is wider than the set of valid {{FsAction}} objects, because it
> doesn't guarantee sensible ordering of access types. For example, the strings
> {{"rxw"}} and {{"--r"}} are valid {{fsaction}} parameter values, but don't
> correspond to valid {{FsAction}} instances.
> The result is that WebHDFS silently accepts {{fsaction}} parameter values
> which don't match any valid {{FsAction}} instance, but doesn't actually
> perform any permissions checking in this case.
> For example, here's a {{CHECKACCESS}} call where we request {{"rw-"}} access
> on a file which we only have permission to read and execute. It raises an
> exception, as it should.
> {code:none}
> curl -i -X GET
> "http://localhost:50070/webhdfs/v1/myfile?op=CHECKACCESS&user.name=nobody&fsaction=r-x";
> HTTP/1.1 403 Forbidden
> Content-Type: application/json
> {
> "RemoteException": {
> "exception": "AccessControlException",
> "javaClassName": "org.apache.hadoop.security.AccessControlException",
> "message": "Permission denied: user=nobody, access=READ_WRITE,
> inode=\"\/myfile\":root:supergroup:drwxr-xr-x"
> }
> }
> {code}
> But if we instead request {{"r-w"}} access, the call appears to succeed:
> {code:none}
> curl -i -X GET
> "http://localhost:50070/webhdfs/v1/myfile?op=CHECKACCESS&user.name=nobody&fsaction=r-w";
> HTTP/1.1 200 OK
> Content-Length: 0
> {code}
> As I see it, the fix would be to change the regex pattern in
> {{FsActionParam}} to something like {{"\[r-\]\[w-\]\[x-\]"}}.
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