Description of problem:

We have a customer reporting a bug with curl on RHEL 8.7.0: any transfer to their Jscape SFTP server creates the file but empty, the content is not copied.

RHEL 9.1.0 curl works fine.

Digging into this, it appears that there is a bug when setting the flags:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
 546 static CURLcode myssh_statemach_act(struct connectdata *conn, bool *block)
 547 {
 :
1114         /* Clear file before writing (normal behaviour) */
1115         flags = O_WRONLY|O_APPEND|O_CREAT|O_TRUNC;
 :
1119       sshc->sftp_file =
1120         sftp_open(sshc->sftp_session, protop->path,
1121                   flags, (mode_t)data->set.new_file_perms);
1122       if(!sshc->sftp_file) {
1123         err = sftp_get_error(sshc->sftp_session);
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

The flags state to O_APPEND + O_TRUNC, which is considered as an error on the Jscape SFTP server side.

This makes libssh fail to return a handle on line 1119 and "err" to be set to 4 ("Generic Error").

RHEL9 code is fixed, the flags line doesn't have O_APPEND anymore:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
1237         flags = O_WRONLY|O_CREAT|O_TRUNC;
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------


Version-Release number of selected component (if applicable):

libcurl-7.61.1-25.el8_7.3.x86_64

How reproducible:

Always when connection to customer system