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https://issues.apache.org/jira/browse/NET-663?focusedWorklogId=235984&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-235984
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ASF GitHub Bot logged work on NET-663:
--------------------------------------

                Author: ASF GitHub Bot
            Created on: 01/May/19 20:42
            Start Date: 01/May/19 20:42
    Worklog Time Spent: 10m 
      Work Description: markt-asf commented on pull request #40: [NET-663] 
Retrieve socket host before closing in remote verification
URL: https://github.com/apache/commons-net/pull/40
 
 
   
 
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Issue Time Tracking
-------------------

            Worklog Id:     (was: 235984)
            Time Spent: 10m
    Remaining Estimate: 0h

> NullPointerException when FTPClient remote verification fails
> -------------------------------------------------------------
>
>                 Key: NET-663
>                 URL: https://issues.apache.org/jira/browse/NET-663
>             Project: Commons Net
>          Issue Type: Bug
>          Components: FTP
>    Affects Versions: 3.6
>         Environment: OS: Linux
>            Reporter: Max Shenfield
>            Priority: Minor
>              Labels: NullPointerException
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> At L934 of the {{FTPClient}} code, Apache does a check to see whether the 
> data and control connections are at the same IP address ({{verifyRemote}}). 
> If they differ, the data connection socket is closed and an exception is 
> raised.  This can be disabled, but is the default behavior 
> ({{__remoteVerificationEnabled = true}}).
> I'm connecting to the FTP via a proxy.  In my setup, the L934-939 code path 
> where {{verifyRemote}} returns false always raises a 
> {{java.lang.NullPointerException}}.  {{socket.getInetAddress()}} seems to 
> return {{null}} after {{socket.close}} is called, leading to 
> {{socket.getInetAdress().getHostAddress()}} to raise the 
> {{java.lang.NullPointerException}} at L938.   This obfuscates a really useful 
> error message ("Host attempting data connection is not the same as server") 
> with a difficult to debug {{NullPointerException}}.
> Example State:
> {code}
> this.__remoteVerificationEnabled -> true
> this.getRemoteAddress().toString() -> "ftp.example.com/987.654.321.000"
> socket.getInetAddress().toString() -> "/123.456.789.000"
> {code}



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