Renci.SshNet.Common.SshException: Failure. exception

Hello,

I have been using the Renci SSH.NET(2016.1.0.0) NuGet package in my web api code, to transfer files from server to a remote SFTP server. This has been working very well for me. The issue I am facing is that I am getting the error marked below. My .NET framework version is 4.6

An exception has been caught during the file upload…:Renci.SshNet.Common.SshException: Failure. at Renci.SshNet.Sftp.SftpSession.RequestOpen(String path, Flags flags, Boolean nullOnError) at Renci.SshNet.SftpClient.InternalUploadFile(Stream input, String path, Flags flags, SftpUploadAsyncResult asyncResult, Action1 uploadCallback) at Renci.SshNet.SftpClient.UploadFile(Stream input, String path, Action1 uploadCallback) at BASF.TAR.RMSService.Controllers.AttachmentController.Get(String sourcepaths, String destinationpath) in d:\Projects\TAR\Samples\BASF.TAR.RMSService\BASF.TAR.RMSService\Controllers\AttachmentController.cs:line 47

I am using the code in my controller as below, its a simple function that takes a source path which is pipe seperated strings and a destination path which is the path on the remote FTP server. The client opens the connection to the server and then in a loop manner each file is uploaded to the remote server and the log is printed.

Please can you let me know why this error is occuring sometimes, any help would be greatly appreciated

public IHttpActionResult Get([FromUri]string sourcepaths, string destinationpath)
        {
            var fileInfo = new List<string>();

            log.Info("Entering the Put() method of the AttachmentController class..");
            try
            {
                using (SftpClient sftp = new SftpClient(ConfigurationManager.AppSettings["SFTP"].ToString(), Convert.ToInt32(ConfigurationManager.AppSettings["Port"].ToString()), ConfigurationManager.AppSettings["UserId"].ToString(), ConfigurationManager.AppSettings["Password"].ToString()))
                {
                    try
                    {
                        if (string.IsNullOrEmpty(sourcepaths) && string.IsNullOrEmpty(destinationpath)) return Ok();

                        var filePaths = sourcepaths.Split('|');
                        sftp.Connect();
                        log.InfoFormat("Connected to SFTP server:{0}..", ConfigurationManager.AppSettings["SFTP"].ToString());
                        
                        log.InfoFormat("Original destination path:{0}", destinationpath);
                        log.InfoFormat("Upload path in the sftp location:{0}", OriginalAttPathToFileSharePath(destinationpath.ToLower()));

                        log.Info("Uploading file...");

                        sftp.ChangeDirectory(OriginalAttPathToFileSharePath(destinationpath.ToLower()));
                        log.InfoFormat("Original destination path:{0}", destinationpath);
                        log.InfoFormat("Upload path in the sftp location:{0}", OriginalAttPathToFileSharePath(destinationpath.ToLower()));
                        foreach (var file in filePaths)
                        {
                            log.InfoFormat("File to be uploaded:{0}", file);
                            using (var stream = new FileStream(file, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
                            {
                                sftp.UploadFile(stream, Path.GetFileName(file), (o) =>
                                {
                                    Console.WriteLine(o);
                                });
                            }
                        }
                        log.Info("File uploaded to server...");
                        sftp.Disconnect();
                    }
                    catch (Exception e)
                    {
                        log.ErrorFormat("An exception has been caught during the file upload..:{0}", e);
                    }
                }
            }
            catch (Exception exp)
            {
                log.Error("Error occured in the Put() method of the AttachmentController class..", exp);
            }
            log.Info("Exiting the Put() method of the AttachmentController class..");
            return Ok();
        }

[worldbeater]

Well, I think I’ve figured out why this is happening to us. If I attempt to use the SSH.NET library on a Windows machine while targeting .NET Core netcoreapp2.1 (not sure, probably .NET Core support is at experimental stage for SSH.NET now), my absolute paths get misinterpreted.

The following line seems to be the cause: https://github.com/sshnet/SSH.NET/blob/13bef36d3811a3811b587c20b33c4ff512dabe93/src/Renci.SshNet/SftpClient.cs#L2051

For example, the following absolute Windows path: C:\Users\usr\AppData\Local\Temp\example_in Gets transformed into the following: /C:/Users/usr/C:/Users/usr/AppData/Local/Temp/example_in

Yeah, /C:/Users/usr repeats twice, and this isn’t a typo! The only way to fix the issue above is to fork the SSH.NET repository, and to replace the line referenced above with somewhat like the following: var fullPath = path; However, this works only for absolute paths, but this was enough in my case.

UPD

Ahh, found another neater way to resolve the issue, all we need to do is to turn the following:

// Breaks with Renci.SshNet.Common.SshException: Failure
sftp.DownloadFile("C:\Users\usr\AppData\Local\Temp\example_in", stream);

Into the following:

// Completes normally.
sftp.DownloadFile("/C:/Users/usr/AppData/Local/Temp/example_in", stream);

And so it works, the same applies to UploadFile too.

// With input like the following path:
// C:\Users\usr\AppData\Local\Temp\example_in
// The snippet below won't throw.
var path = $"/{from.Replace(@"\", "/")}";
sftp.DownloadFile(path, stream);

[Imbaker1234]

Problem

Encountered this error when attempting to call ReadAllFiles during my work on the CES.SquareDUpdater.

I was able to list all of the files, indicating this was not a lack of access, but some implementation detail.

---

Discovery - 1

I was reading all items in the directory, not just files. Calling ReadAllText on directories causes this very generic failure displayed here.

---

Solution

After listing all items (files and directories) in my target/parent directory I was searching I filtered out directories.

        public async Task<IEnumerable<string>> ListFiles(string remoteDirectory)
        {
            return await ConnectAndOperate(() => Task.FromResult(_client.ListDirectory(remoteDirectory)
                    .Where(item => !item.IsDirectory) // This is where I made the change.
                    .OrderBy(file => file.LastWriteTimeUtc)
                    .Select(file => file.FullName)),
                $"Listing files in `{remoteDirectory}");
        }

#DevLog