Request Based SFTP API

The request based API allows for custom backends in a way similar to the http package. In order to create a backend you need to implement 4 handler interfaces; one for reading, one for writing, one for misc commands and one for listing files. Each has 1 required method and in each case those methods take the Request as the only parameter and they each return something different. These 4 interfaces are enough to handle all the SFTP traffic in a simplified manner.

The Request structure has 5 public fields which you will deal with.

• Method (string) - string name of incoming call
• Filepath (string) - path of file to act on
• Attrs ([]byte) - byte string of file attribute data
• Target (string) - target path for renames and sym-links

Below are the methods and a brief description of what they need to do.

Fileread(*Request) (io.Reader, error)

Handler for “Get” method and returns an io.Reader for the file which the server then sends to the client.

Filewrite(*Request) (io.Writer, error)

Handler for “Put” method and returns an io.Writer for the file which the server then writes the uploaded file to.

Filecmd(*Request) error

Handles “SetStat”, “Rename”, “Rmdir”, “Mkdir” and “Symlink” methods. Makes the appropriate changes and returns nil for success or an filesystem like error (eg. os.ErrNotExist).

Fileinfo(*Request) ([]os.FileInfo, error)

Handles “List”, “Stat”, “Readlink” methods. Gathers/creates FileInfo structs with the data on the files and returns in a list (list of 1 for Stat and Readlink).

TODO

• Add support for API users to see trace/debugging info of what is going on inside SFTP server.
• Consider adding support for SFTP file append only mode.