[PATCH] Adds support for Append command (SSH_FXF_APPEND) to sftp_client

Daniele Calore
Mon, 14 May 2007 21:30:22 -0000

Dear list,

Attached is a patch that implements the "append" command in a sftp
session,
as describe in "draft-ietf-secsh-filexfer-01" and further releases.

It is for and had been tested on the current version of OpenSSH
(the Portable CVS) and it works, also against non patched versions.

The patch is "simple" it it just like the "do_upload"
function in
"sftp-client.c".

Pseudo Instruction of the new "do_append" function:

 1) stat_remote_file
         This will return an Attrib struct to know the remote file size.
 2) open_remote_file
         Open the remote file without the "SSH2_FXF_TRUNC" flag and
with
         SSH2_FXF_APPEND flag.
 3) write_to_remote_file
         It is like the "do_upload" function, expect that the
         offset does not start with a '0' but it is set to the value
returned
         by "stat_remote_file".

 More in depth I have use the function "do_fstat" to retrive
remote_file
 size.  The function "do_fstat" is never used, but is still present,
in the
 "sftp-client.c" ... so why not to use it ?

I hope this patch will be included in future release of OpenSSH, or at least
that you will consider to reimplement it in a better way.  Let me know if ...


* Some notes:

I have also revisited "sftp.c".
There is now a new I_APPEND Command, that has number "1" for
alphabetic
reason.

If you do not plan to insert this patch consider to change this line of code:

--- sftp.c.orig 2007-05-14 22:48:33.000000000 +0200
+++ sftp.c      2007-05-14 22:50:07.000000000 +0200
@@ -940,7 +940,7 @@
                        return(-1);
                if (get_pathname(&cp, path2))
                        return(-1);
-               if (!*path1 || !*path2) {
+               if (*path1 == NULL || *path2 == NULL) {
                        error("You must specify two paths after a %s "
                            "command.", cmd);
                        return(-1);

And maybe remove also the "do_fstat" function in
"sftp-client.c"
(it is never used)

We can also patch the "sftp-server.c" to honor the APPEND flag, but
there
is no way for the client to know if the server is patched or not...

* Suggestions:
1) Change the SSH2_FILEXFER_VERSION to something new.
2) Implement a VENDOR specific future to retrive the presence of the new
   SSH2_FXF_APPEND future.  We can do this using the SSH2_FXP_EXTENDED
   command.
(This will be useful also for other patches; like the SSH_FXP_LINK patch)

If you want I can make a patch also for the server side.


Best regards,

--
Daniele Calore ( orkaan at orkaan.org )
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