Deprecating scp [LWN.net]

Deprecating scp

Posted Nov 5, 2020 22:24 UTC (Thu) by bnewbold (subscriber, #72587)
Parent article: Deprecating scp

What about re-using tar conventions and semantics? Eg, "source" side creates a tar stream, "destination" expands it. The security issues and corner-cases of tar seem well known (though maybe there are problems i'm not aware of). Also reduces the number of round-trip messages when pushing large numbers of small files (if I recall rcp protocol requires a round-trip between each file transfered). "star"?

Here is an old blog post describing the rcp protocol: http://web.archive.org/web/20110930024114/http://blogs.or...

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Deprecating scp

Posted Nov 5, 2020 22:37 UTC (Thu) by tokudan (subscriber, #104407) [Link] (4 responses)

That would create a dependency on tar binaries or require a reimplementation.
Rewriting scp to just use sftp seems to be the easier option, even if it's not as efficient. Efficient is rsync's domain.
Getting something done without too much hassle and easily chroot-able would be scp/sftp.

Deprecating scp

Posted Nov 5, 2020 23:03 UTC (Thu) by Sesse (subscriber, #53779) [Link] (2 responses)

Actually sftp is more efficient than scp, too. scp has its own awful buffering on top of TCP (lots of HPC sites used a patched version to avoid speed limits). Or at least did 10+ years ago when I checked; it's possible that OpenSSH has managed to circumvent the issue now.

Deprecating scp

Posted Nov 6, 2020 10:44 UTC (Fri) by ptman (subscriber, #57271) [Link] (1 responses)

IIRC SFTP is more like NFS than FTP and latency limits its bandwidth quite a lot.

Deprecating scp

Posted Nov 6, 2020 12:49 UTC (Fri) by ptman (subscriber, #57271) [Link]

Here's a good explanation: https://news.ycombinator.com/item?id=25006723

Deprecating scp

Posted Nov 6, 2020 12:19 UTC (Fri) by dezgeg (guest, #92243) [Link]

SFTP server is not available everywhere either (in embedded systems especially).

Deprecating scp

Posted Nov 6, 2020 5:56 UTC (Fri) by nilsmeyer (guest, #122604) [Link] (2 responses)

I often use tar through SSH, especially when I need to raise my privilege on either side of the connection. It's a simple matter of piping which should be familiar to most users. It will require shell access though. I would worry that tar has a couple of security issues as well depending on the parameters and the tar stream which may make it unsuitable for the use case of only allowing remote users to transfer files without shell access.

Deprecating scp

Posted Nov 6, 2020 7:55 UTC (Fri) by ibukanov (subscriber, #3942) [Link] (1 responses)

scp runs the remote scp binary using shell.

Deprecating scp

Posted Nov 8, 2020 11:09 UTC (Sun) by ptman (subscriber, #57271) [Link]

But there are shells that restrict you to only scp. Like rssh or scponly

Deprecating scp

Posted Nov 9, 2020 22:09 UTC (Mon) by Creideiki (subscriber, #38747) [Link]

Having had the misfortune of working in an environment that mixed modern Linux, ancient Solaris, and weird real-time UNIXoids, I laugh at the notion of "a tar stream", as if that is somehow well-defined. You don't even have to go that far out in the weeds to find incompatibilities; read https://mgorny.pl/articles/portability-of-tar-features.html and despair.