Topic "Reproducible data corruption during transfer"

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patrick
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Joined: 2008-02-04
Posts: 3
I get reproducible data corruption when I upload one file with WinSCP. The file is a configuration file created by foobar2000 (an audio player for Windows).

It took my friend and me a long time to track this down to WinSCP, but now I'm sure about it. I verified it on another computer with the same file, and the result is the same.

WinSCP version: 4.0.6 build 358
Transfer protocol: both with SFTP and SCP
There is no error message. Everything seems normal, but the file on the server is different from the file on the client.

The file in question can be downloaded from here: <invalid hyperlink removed by admin> User: winscp / Password: Qg5j5a8K
It is contained in a ZIP archive. Unpack it and verify that the md5sum is: '8d0b548533aa231652a91f040c99ffe2'
After uploading it to somewhere with WinSCP, it will have the md5sum 'e104794beaf0b830a09dbefa04a861f9'.

I consider this bug to be highly critical.

If you need more information, please contact me by mail.
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martin
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Joined: 2002-12-10
Posts: 25015
Location: Prague, Czechia
Would this FAQ explain the behaviour?
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Martin Prikryl
patrick
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Joined: 2008-02-04
Posts: 3
prikryl wrote:
Would this FAQ explain the behaviour?


Yes, it indeed explains the behaviour. But in this case it renders the transmitted data unusable. And the 'casual user' doesn't know why. I'd say this 'feature' should definitely not be activated by default. Classifying a file by its extension is a really bad idea in this context, if you ask me.
martin
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Joined: 2002-12-10
Posts: 25015
Location: Prague, Czechia
patrick wrote:
Yes, it indeed explains the behaviour. But in this case it renders the transmitted data unusable. And the 'casual user' doesn't know why. I'd say this 'feature' should definitely not be activated by default. Classifying a file by its extension is a really bad idea in this context, if you ask me.

I understand. On the other hand there are many users that need the conversion, although they does not know it. That's why it is enabled by default.
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Martin Prikryl
patrick
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Joined: 2008-02-04
Posts: 3
I still don't fully understand why WinSCP must distinguish between binary and text, unlike any other sftp client I know. But putting that aside I would suggest some additional sanity checks regarding the classification of the file in question. For example use the algorithms of the 'file' command (available on Unix/Linux) instead of or in addition to the current extension-based classification. Perhaps as a last resort ask the user to classify a file when unsure, instead of just transfering it and damaging it in the process.
martin
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Joined: 2002-12-10
Posts: 25015
Location: Prague, Czechia
patrick wrote:
I still don't fully understand why WinSCP must distinguish between binary and text, unlike any other sftp client I know.

This functionality is not common for SFTP client yet. But it is quite common with FTP.
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Martin Prikryl
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