Re: Problems with remote repository access via sftp

Hi Denis,

> back to dar, I found and fixed several issues:

Thank you and sorry for my delayed answer, I have not found the time to
deal with it until today.

So I tested with the new 2.7.8.RC3 but still without success.

First the good news:

> * first the self test error reported at "mycurl_easyhandle_node.cpp
>   line 176". It was a wrong implicit type conversion in libdar nothing
>   that hit this self test --- there is a lot in libdar --- before
>  calling libcurl.

> * I also fixed the double slash after the hostname, so the URL send to
> libcurl are correct (even if, so far, it did not hurt having double slash).
> * last I have surfaces the libcurl version when you list dar's version,
> for you can seen which libcurl is used in dar_static and which is grab
> from the OS when using dynamically linked dar.

Yep, this all works well and is helpful for debugging the reason why I
still cannot connect to my sftp share.

I still have two cases, one for my local machine running Void Linux and
one for a VPS running Debian.
I tested on both with `dar_static`.

On my local machine, I get a segfault both with and without running with
-afile-auth.

On Debian, things are better in a way that I get now the libcurl debug
messages.
The problems seems to be a failure in establishing a ssh connection.
Here is the output:

```
$ ./dar_static_2.7.8.RC3_x86_64_GNU_Linux -avc -l sftp://****@****.your-storagebox.de/archives/server4you/first
Please provide the password for login **** at host ****.your-storagebox.de:
repository parameters passed to libcurl:
hostname      : ****.your-storagebox.de
port          :
login         : ****
password      : (hidden)
base URL      : sftp://****.your-storagebox.de/
Asking libcurl to read directory content at sftp://****.your-storagebox.de/archives/server4you/
*   Trying 2a01:4f8:***:22...
* Connected to ****.your-storagebox.de (2a01:4f8:***) port 22 (#0)
* Found host ****.your-storagebox.de in /home/martin/.ssh/known_hosts
* Set "ecdsa-sha2-nistp521" as SSH hostkey type
* Failure establishing ssh session: -5, Unable to exchange encryption keys
* Closing connection 0
Error met while looking for slices: Error met while performing action on libcurl handle: Failed initialization, aborting
Asking libcurl to read directory content at sftp://****.your-storagebox.de/archives/server4you/
* Hostname ****.your-storagebox.de was found in DNS cache
*   Trying 2a01:4f8:***:22...
* Connected to ****.your-storagebox.de (2a01:4f8:***) port 22 (#1)
* Found host ****.your-storagebox.de in /home/martin/.ssh/known_hosts
* Set "ecdsa-sha2-nistp521" as SSH hostkey type
* Failure establishing ssh session: -5, Unable to exchange encryption keys
* Closing connection 1
Error met while looking for slices: Error met while performing action on libcurl handle: Failed initialization, aborting
No backup file is present in sftp://****.your-storagebox.de/archives/server4you for archive first, please provide the last file of the set. [return = YES
| Esc = NO]
No backup file is present in sftp://****.your-storagebox.de/archives/server4you for archive first, please provide the last file of the set. [return = YES
| Esc = NO]
Escaping...
Final memory cleanup...
Aborting program. User refused to continue while asking: No backup file is present in sftp://****.your-storagebox.de/archives/server4you for archive first
, please provide the last file of the set.
```

I have no problems to connect and list the sftp content with curl using
this version though:

```
$ curl -V
curl 7.74.0 (x86_64-pc-linux-gnu) libcurl/7.74.0 OpenSSL/1.1.1n zlib/1.2.11 brotli/1.0.9 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh2/1.9.0 nghttp2/1
.43.0 librtmp/2.3
Release-Date: 2020-12-09
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps mqtt pop3 pop3s rtmp rtsp scp sftp smb smbs smtp smtps telnet tftp
Features: alt-svc AsynchDNS brotli GSS-API HTTP2 HTTPS-proxy IDN IPv6
Kerberos Largefile libz NTLM NTLM_WB PSL SPNEGO SSL TLS-SRP UnixSockets
```

I could not yet dig deeper into it, and why it could not exchange
encryption keys.
Maybe it is really related to my remote sftp configuration.

Can you connect to a remote sftp share in general?

Best regards,
Martin