[jira] [Work logged] (NET-663) NullPointerException when FTPClient remote verification fails

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[jira] [Work logged] (NET-663) NullPointerException when FTPClient remote verification fails

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     [ https://issues.apache.org/jira/browse/NET-663?focusedWorklogId=247752&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-247752 ]

ASF GitHub Bot logged work on NET-663:

                Author: ASF GitHub Bot
            Created on: 23/May/19 22:32
            Start Date: 23/May/19 22:32
    Worklog Time Spent: 10m
      Work Description: mshenfield commented on pull request #40: [NET-663] Retrieve socket host before closing in remote verification
URL: https://github.com/apache/commons-net/pull/40
   This retrieves the socket host before closing the socket when remote verification fails in order to get a non-null host address. In [NET-663](https://issues.apache.org/jira/browse/NET-663), `socket.getInetAddress()` returned a null after the socket was closed, causing a `NullPointerException` instead of the more helpful error message intended.
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Issue Time Tracking

    Worklog Id:     (was: 247752)
    Time Spent: 20m  (was: 10m)

> 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: 20m
>  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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