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https://issues.apache.org/jira/browse/HADOOP-18235?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17692040#comment-17692040
 ] 

ASF GitHub Bot commented on HADOOP-18235:
-----------------------------------------

pranavsaxena-microsoft commented on code in PR #4998:
URL: https://github.com/apache/hadoop/pull/4998#discussion_r1114022360


##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/LocalKeyStoreProvider.java:
##########
@@ -142,20 +142,26 @@ protected void initFileSystem(URI uri)
 
   @Override
   public void flush() throws IOException {
-    super.flush();
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Resetting permissions to '" + permissions + "'");
-    }
-    if (!Shell.WINDOWS) {
-      Files.setPosixFilePermissions(Paths.get(file.getCanonicalPath()),
-          permissions);
-    } else {
-      // FsPermission expects a 10-character string because of the leading
-      // directory indicator, i.e. "drwx------". The JDK toString method 
returns
-      // a 9-character string, so prepend a leading character.
-      FsPermission fsPermission = FsPermission.valueOf(
-          "-" + PosixFilePermissions.toString(permissions));
-      FileUtil.setPermission(file, fsPermission);
+    super.getWriteLock().lock();
+    try {
+      file.createNewFile();
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("Resetting permissions to '" + permissions + "'");
+      }
+      if (!Shell.WINDOWS) {
+        Files.setPosixFilePermissions(Paths.get(file.getCanonicalPath()),
+            permissions);
+      } else {
+        // FsPermission expects a 10-character string because of the leading
+        // directory indicator, i.e. "drwx------". The JDK toString method 
returns
+        // a 9-character string, so prepend a leading character.
+        FsPermission fsPermission = FsPermission.valueOf(
+            "-" + PosixFilePermissions.toString(permissions));
+        FileUtil.setPermission(file, fsPermission);
+      }

Review Comment:
   In the method getOutputStreamForKeystore(), before sending outputStream, 
should it be checked that the file is empty. Reason being, between creatingFile 
and setting permissions, there could be that some other process puts something 
in the file.





> vulnerability:  we may leak sensitive information in LocalKeyStoreProvider
> --------------------------------------------------------------------------
>
>                 Key: HADOOP-18235
>                 URL: https://issues.apache.org/jira/browse/HADOOP-18235
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: lujie
>            Assignee: Clay B.
>            Priority: Critical
>              Labels: pull-request-available
>
> Currently, we implement flush like:
> {code:java}
> //  public void flush() throws IOException {
>     super.flush();
>     if (LOG.isDebugEnabled()) {
>       LOG.debug("Resetting permissions to '" + permissions + "'");
>     }
>     if (!Shell.WINDOWS) {
>       Files.setPosixFilePermissions(Paths.get(file.getCanonicalPath()),
>           permissions);
>     } else {
>       // FsPermission expects a 10-character string because of the leading
>       // directory indicator, i.e. "drwx------". The JDK toString method 
> returns
>       // a 9-character string, so prepend a leading character.
>       FsPermission fsPermission = FsPermission.valueOf(
>           "-" + PosixFilePermissions.toString(permissions));
>       FileUtil.setPermission(file, fsPermission);
>     }
>   } {code}
> we wirite the Credential first, then set permission.
> The correct order is setPermission first, then write Credential .
> Otherswise, we may leak Credential . For example, the origin perms of file is 
> 755(default on linux),  when the Credential  is flushed, Credential can be 
> leaked when 
>  
> 1)between flush and setPermission,  others have a chance to access the file.
> 2)  CredentialShell(or the machine node )  crash between flush and 
> setPermission,   the file permission is 755 for ever before we run the 
> CredentialShell again.
>  



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