[Solved]SFTP via HTTP proxy: access violation in SSPICLI.DLL

[probspot3]

Hi,

I've set up an SFTP synchronization with public key authentication and SFTP library. Works perfectly when connecting directly.

At work however I am behind an HTTP proxy. Therefore I changed the SSHd's listening port to 443 and added Web Tunneling in Syncovery conf as shown on the attached screenshot.

After trying to connect I'm getting the following in the log file:

===============================
Using client certificate "NUC_backup_RSA" with K:\soft\id_rsa.ppk.pub and K:\soft\id_rsa.ppk
SSH Exception: Access violation at address 00007FFD877F432A in module 'SSPICLI.DLL'. Read of address FFFFFFFFFFFFFFFF
Address: <Proxy IP address>
16.03.2016 13:28:30 FTP Exception (3): ETGFTPError Access violation at address 00007FFD877F432A in module 'SSPICLI.DLL'. Read of address FFFFFFFFFFFFFFFF @ 00000000014EDE73

ERROR
sftp://my.sftp.host/bkp/Backups: Cannot access sftp://my.sftp.host/bkp/Backups
(Access violation at address 00007FFD877F432A in module 'SSPICLI.DLL'. Read of address FFFFFFFFFFFFFFFF at 00000000014EDE73)


************************************************************************
ERROR (EPrepException): Cannot access sftp://my.sftp.host/bkp/Backups/
(Access violation at address 00007FFD877F432A in module 'SSPICLI.DLL'. Read of address FFFFFFFFFFFFFFFF at 00000000014EDE73) @ 0000000001962DEF
************************************************************************

Job preparation and/or building the filelist failed.
=========================================

Is this a bug or an expected behavior? I'm on Windows 8.1.

Thanks

[superflexible]

This was a bug, can you try the new version 7.45a?

[probspot3]

Tried with 7.46c, it works now. Thank you.

However, I discovered that the SFTP method does not preserve timestamps on the remote side (also tested directly without Web tunneling). In the documentation you recommend exactly this method for timestamp preservation.

I verified that my SFTP server (OpenSSH 7.2) supports timestamp preservation by connecting to it using the '-p' option as follows:

sftp -p username@my.sftp.server

and uploading a sample file.

Choosing other library options in Syncovery (SCP or Pure SSH) produces connection error which is kind of expected as I hardened the server to accept SFTP connections only.

Am I missing some setting to make SFTP timestamps work?

[superflexible]

TImestamps usually work fine via SFTP. Some servers are limited though and may reject the requests made by Syncovery. You could try editing the Advanced SSH Settings and limiting the SFTP versions to up to 3.

Or you could send a test account to support@syncovery.com so I can test it with your server.

[probspot3]

I think I nailed the issue: it was about the underlying filesystem (NTFS-3G) of the remote side. The filesystem (and all new files on it) was owned by one user, and the sync was done with another one. The POSIX standard dictates that only the owner of the files is allowed to update their timestamps, which was not the case here. With some NTFS-3G voodoo I managed to configure it correctly.

Now I'm running into the next issue: the timestamps of files are preserved fine, however those of directories are not. This results in Syncovery simply not seeing the files on the remote side which are inside a directory IF that directory has a timestamp different from the local one (which is the case here). Looks like Syncovery doesn't even traverse the directory if it detects that it has a different timestamp, and wants to copy all files in that directory again.

Questions:

1) I made a test with 'sftp -p' and tried to copy a test directory. Its timestamp was _not_ preserved. Does it mean that the SFTP protocol itself does not have the functionality for this?

2) Can I make Syncovery look into _all_ directories and compare their contents even if the directories themselves might have different timestamps? In other words, can Syncovery ignore the timestamps of directories and always compare their contents?

Thanks.

[superflexible]

Timestamps of folders are irrelevant. Syncovery always scans all folders and compares the files.

So either the profile is misconfigured, or the SFTP communication is not working correctly yet.

The first thing to try would be to change the setting "Recursive listing" on the second tab sheet of the FTP dialog. The recursive listing works only with some servers.

[probspot3]

Solved this one as well. Again it was due to my "special" setup. I'm syncing a backup already made by Syncovery with versioning. In other words, my setup is A->B (with versioning), and then B->C (without versioning). To make the latter work I had to tick the "Do not decode right-hand filenames when building the file list" option for my B->C profile. Now everything works as expected.

Thanks for your hints!