Comment by jolmg

SCP protocol is fine and convenient as long as people understand that the remote file arguments are server-side shell code, and the consequences that implies.

You get the benefit of being able to e.g. get your last download off your desktop to your laptop like this:

  scp -TO desktop:'downloads/*(oc[1])' .

or this if you're on bash:

  scp -TO desktop:'$(ls -t downloads/* | head -1)' .

or pull a file from a very nested project dir for which you have setup dynamic directories (or shell variables if you're on bash):

  scp -TO desktop:'~foo/config/database.yml' config/

  scp -TO desktop:'$FOO_DIR/config/database.yml' config/

Just don't pull files from an SCP server that may be malicious. Use on trusted servers. If you do the following on your home dir:

  scp -TOr malicious:foo/ .

That may overwrite .ssh/authorized_keys, .zshrc, etc. because `foo/` is server-side shell code. The client can't say that `.zshrc` resulting from the evaluation of `foo/` doesn't make sense, because it might in the remote shell language.

> If you need something that SFTP cannot do, then use tar on both sides.

No reason to make things inconvenient between personal, trusted computers, just because there may be malicious servers out there where one has no reason to SCP.

Something else to note is that your suggestion of using `tar` like `ssh malicious 'tar c foo/' | tar x` faces basically the exact same problem. The server can be malicious and return .ssh/authorized_keys, .zshrc, etc. in the archive for `tar x` to overwrite locally basically exactly the same way. This goes with the point of this SE answer:

> I'd say a lot of Unix commands become unsafe if you consider a MITM on SSH possible. A malicious sudo could steal your password, a malicious communication client could read your mails/instant messages, etc. Saying that replacing scp with sftp when talking to a compromised server will somehow rectify the situation is very optimistic to say the least. [...] In short, if you don't pay attention to which servers you SSH into, there's a high risk for you to be screwed no matter which tools you use, and using sftp instead of scp will be only marginally safer. --- https://unix.stackexchange.com/questions/571293/is-scp-unsaf...

I think this whole problem with SCP just stems from not having properly documented this aspect in the manpage, so people expected it to just take filepaths.