openssh unix dev - Jul 2025 - SFTP's handling of "." and ".."

Hi all,

Apologies if this has already been discussed before; I googled a bit before
coming here but couldn't find any mention of this issue. The other day I
noticed what felt like some strange behavior from SFTP. When doing a
recursive put command to upload a directory and making the folder a
"." or
"..", it gets copied to the destination with those dots. I'm not
good at
explaining things so perhaps it's easier to give an example.
If I ran:
$ cd /path/to/source_dir
$ sftp dest_host
sftp> put -r . /destination/path

Instead of transferring source_dir as a full directory to
"/destination/path/source_dir", what happens is the "." is
simply appended
to /destination/path resulting in all of the files going to
"/destination/path/.". Even worse, if I tried to transfer
".." to
"/destination/path", all my files would instead go to
"/destination"!

This feels problematic to me because it's completely unexpected behavior
from what one would expect based on any other scenario when uploading a
directory. I think I found where in sftp.c this is happening:
[image: image.png]

So my question now is, would there be interest in me submitting a pull
request for a fix to this? Or am I completely missing something? Don't want
to waste any effort/waste any reviewer's time if this is intentional or
something that should be expected :)

Thanks,
Andrew

On Thu, 3 Jul 2025, Andrew Wood wrote:
>  Hi all,
> 
> Apologies if this has already been discussed before; I googled a bit before
> coming here but couldn't find any mention of this issue. The other day
I
> noticed what felt like some strange behavior from SFTP. When doing a
> recursive put command to upload a directory and making the folder a
"." or
> "..", it gets copied to the destination with those dots. I'm
not good at
> explaining things so perhaps it's easier to give an example.
> If I ran:
> $ cd /path/to/source_dir
> $ sftp dest_host
> sftp> put -r . /destination/path
> 
> Instead of transferring source_dir as a full directory to
> "/destination/path/source_dir", what happens is the "."
is simply appended
> to /destination/path resulting in all of the files going to
> "/destination/path/.".
This is expected IMO. You're telling sftp to transfer the current
directory and it's doing that.
> Even worse, if I tried to transfer ".." to
> "/destination/path", all my files would instead go to
"/destination"!
This OTOH isn't expected. "put -r .. foo" should IMO have
identical
behaviour to "put -r . foo". I think this fixed it:

diff --git a/sftp.c b/sftp.c
index dfbb2d2..a3339f1 100644
--- a/sftp.c
+++ b/sftp.c
@@ -760,6 +760,9 @@ process_put(struct sftp_conn *conn, const char *src, const
char *dst,
 			err = -1;
 			goto out;
 		}
+		/* Special handling for source of '..' */
+		if (strcmp(filename, "..") == 0)
+			filename++; /* point to '.' */
 
 		free(abs_dst);
 		abs_dst = NULL;