Golang SFTP Server

The sftp package implements the SFTP server protocol. To serve SFTP, you need only an io.ReadWriter for the packet transport (typically this will be an SSH channel), and a RequestHandler implementation.

This package currently provides two RequestHandler implementations for your convenience: an in-memory filesystem (MemFS) and a wrapper around the OS filesystem (HostFS). Both implementations are excellent references for writing your own driver.

See the GoDoc for full documentation and small examples. Larger examples can be found in the examples/ folder.

Contributing

We welcome pull requests, bug fixes and issue reports.

Before proposing a large change, first please discuss your change by raising an issue.

For API/code bugs, please include a small, self contained code example to reproduce the issue. For pull requests, remember test coverage.

We try to handle issues and pull requests with a 0 open philosophy. That means we will try to address the submission as soon as possible and will work toward a resolution. If progress can no longer be made (eg. unreproducible bug) or stops (eg. unresponsive submitter), we will close the bug.

Thanks.

Navigating the Source Code

The SFTP protocol spec used for reference can be found here. Please also review the OpenSSH extensions and changes, as they influenced most of the SFTP ecosystem.

• packets.go

  All (un)marshaling code for standard SFTP packets. Please respect the fxp<type>Pkt naming convention. Do not propose using the reflect or encoding/binary packages for marshaling unless you can prove that they are not vastly slower than manually-written marshaling code.

  Note: Packets do not technically adhere to the encoding.BinaryMarshaler/Unmarshaler interfaces. This is done for significant performance gains, and packet types are not exposed by the package so it should be a non-issue. Namely, fxpWritePkt retains a subslice of the data passed to Unmarshal, and packets cannot directly unmarshal themselves from their marshaled forms. Both of these gotchas should be pretty easy to keep in check and allow for minimal copying and memory usage.

• packets_extended.go

  All (un)marshaling code for extended packets. Please respect the fxpExt<type>Pkt naming convention and read the packets.go note above.

• sftp.go

  Contains all the SFTP protocol constants, like packet types and file open flags. Please respect the fxp<type> naming convention, e.g. SSH_FXP_INIT becomes fxpInit and SSH_FXP_READDIR becomes fxpReaddir.

• server.go

  Contains the Serve(io.ReadWriter, RequestHandler) implementation and also the RequestHandler interface.

• handler_*.go

  Each RequestHandler implementation gets its own file, prefixed with handler_.

• TODO(samterainsights): rest of the files cleanup/documentation...