User is denied access without "read" permission to the physical path

Question

I am trying to create an upload-only SFTP Server.

But, if I deny the physical path "read" permission to the user, it fails to login:

Server log:

2021-07-21 16:45:37.460 +00:00 [Error] Session 4: Error while initializing subsystem (sftp): nmfqt.pabbe: Access denied.
at nmfqt.kuvgb.ybxbw(String p0, FileSystemOperation p1, FileServerAction p2)
at nmfqt.kuvgb.dobwe(String p0)
at nmfqt.uyjub.nsjsn(nsbrt p0, String& p1)
at nmfqt.ivqkh.lromo(zyjht p0, bqsol p1, String p2, String& p3)
at nmfqt.clxpq.nmfqt.ngxrj.udyux(String p0, String p1, String& p2)
at nmfqt.hfswm.wbirm(String p0, String p1, Boolean p2)

Access log:

20210721164537.457,"127.0.0.1",4,"alice","login",[]
20210721164537.459,"127.0.0.1",4,"alice","access",["/mount", "Read"]
20210721_164537.464,"127.0.0.1",4,"alice","logout",[]

Answer 1

Hi Gromit,

I was able to replicate the issue and will try to come with a solution / fix soon.

Answer 2

Hi Gromit,

Buru SFTP Server v2.4.1 should have the issue fixed.

Hope it helps!

Comments

I have upgraded to 2.4.1 - same problem, different error in WinSCP:
Permission denied.
Error code: 3
Error message from server: Access denied.


Access log:
20210726_173854.474,"127.0.0.1",6,"alice","login",[]
20210726_173854.476,"127.0.0.1",6,"alice","access",["/mount", "Read"]
20210726_173854.516,"127.0.0.1",6,"alice","access",["/mount", "Read"]
20210726_173854.541,"127.0.0.1",6,"alice","access",["/mount", "List"]

Server log didn't update for some reason.

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There's an error message because since your root is write-only, you can't read its contents. I tried using WinSCP and I can write to the root folder just fine (with the same error message you got).

We might distinguish "list" and "read" in the future but I can't say when this will get implemented.

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So it's currently impossible to create an upload-only SFTP Server?

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It is possible and you already did it. The error you got is displayed because WinSCP cannot list the contents of the root folder (because it is write-only). But as you can see WinSCP is connected and you can upload files.

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Has this issue been resolved? We are not able to use FileZilla at all when accessing write only folders, since it straight up drops the connection when trying to read/list directory content. I know that other servers can be configured to return an empty listing in case of write only folders - this would be a much needed feature going forward....

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The suggested behavior change will be implemented - here's a ticket you can follow for more information -- https://github.com/rebexnet/buru-sftp-server/issues/5 . Please note that as of now there is no ETA on shipping this feature.