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https://issues.apache.org/jira/browse/SSHD-1147?focusedWorklogId=571542&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-571542
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ASF GitHub Bot logged work on SSHD-1147:
----------------------------------------
Author: ASF GitHub Bot
Created on: 24/Mar/21 22:34
Start Date: 24/Mar/21 22:34
Worklog Time Spent: 10m
Work Description: tomaswolf opened a new pull request #187:
URL: https://github.com/apache/mina-sshd/pull/187
IBM's Sterling B2B SFTP connector may limit some files to be downloaded
only once. The mechanism they use assumes that once a file has been
opened, it'll be read and closed without any other SFTP requests being
made on the same handle in between.
Get the file size via SSH_FXP_STAT before opening the file instead of
using SSH_FXP_FSTAT on the handle obtained from opening the file. That
way it should be possible to download such files from such an off-spec
SFTP server.
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Issue Time Tracking
-------------------
Worklog Id: (was: 571542)
Remaining Estimate: 0h
Time Spent: 10m
> SftpClient is not able to download file from proprietory SFTP servers (IBM)
> with a one time download policy
> -----------------------------------------------------------------------------------------------------------
>
> Key: SSHD-1147
> URL: https://issues.apache.org/jira/browse/SSHD-1147
> Project: MINA SSHD
> Issue Type: Wish
> Affects Versions: 2.5.1
> Reporter: Alex D
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Some propretory SFTP servers support a so-called "one time download" policy
> also known as Extractability Count.
> Current implementation of the input stream based read ofile operation
> org.apache.sshd.client.subsystem.sftp.SftpClient::read(String path) uses
> org.apache.sshd.client.subsystem.sftp.impl.SftpInputStreamAsync
> which performs 2 operations in its constructor:
> 1) Open remote file (SftpClient::open)
> 2) Calculate remote file size using file's handle obtained in 1)
> As a result the following error is produced on attempt to download a file
> from IBMs SFTP:
> SFTP error (SSH_FX_FAILURE): The message [remote file path] is not
> extractable!
> IBM specifically states that it's not their problem at all, and they are not
> going to fix it.
> According to their flow described here:
> https://www.ibm.com/support/pages/node/1121475?lang=en
> "Any attempt from client to issue other SFTP operations like SSH_FXP_STAT
> (reading attributes) makes server to validate extractability_count > 0.
> If found 0, download would be reported as "not extractable".
> Most likely it's possible to use SftpClient::openRemoteFileChannel and work
> with the obtained FileChannel manually without any additional requests to
> stat remote file size.
> Though it would be a cumbersome approach, as reading remote file in chunks
> not knowing its size in this case will be far from optimal.
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