SFTP, SCP & RSYNC support

Introduction

The Bastion's main goal is to secure ssh connections. However, one might also want to use sftp, scp or rsync through it.

Its use is supported through the scp, sftp and rsync bastion plugins, and documented as part of all the plugins. This additional documentation section gives some examples and outlines some common configuration errors.

Prerequisites

SFTP & SCP

The use of SFTP or SCP through the bastion requires an SFTP or SCP program that supports the -S option, and a shell to run the wrapper. This is the case on all operating systems using OpenSSH such as Linux or *BSD.

If you're running under Microsoft Windows, you might want to setup either a Linux VM, or a WSL (Windows Subsystem for Linux) environment, to have the OpenSSH version of scp or sftp and a working POSIX-style shell.

Note that it won't work with Windows GUI apps, because there's no way to specify a wrapper (through -S), and no shell. For example, it won't work under WinSCP.

RSYNC

The use of RSYNC through the bastion only requires rsync to be installed locally and remotely, as is the case for usage without the bastion.

Basic usage

Please check the scp, sftp and rsync documentation to see how to use these.

Access model

Note

Currently, to be able to use SFTP, SCP or RSYNC with a remote server, you first need to have a declared SSH access to it. This might change in a future version.

Error message 1

This is briefly explained in the scp/doc:/plugins/open/sftp/rsync documentation, but having access rights to SSH to a machine is not enough to have the right to SCP to or from it, or use SFTP/RSYNC on it. If you have the following error, then this is the problem you're having:

Sorry, you seem to have access through ssh and through scp but by different and distinct means (distinct keys).
The intersection between your rights for ssh and for scp needs to be at least one.

When this happens, it means that you have at least one declared SSH access to this machine (through one or several groups, or through personal accesses). You also have at least one declared SCP/SFTP/RSYNC access to it. However both accesses are declared through different means, and more precisely different SSH keys. For example:

  • You are a member of a group having this machine on one hand, and you have a declared SCP/SFTP/RSYNC access to this machine using a personal access on the other hand. For SSH, the group key would be used, but for SCP/SFTP, your personal key would be used. However, for technical reasons (that might be lifted in a future version), your SSH and SCP/SFTP/RSYNC access must be declared with the same key, so in other words, using the same access mean (same group, or personal access).

  • You are a member of group A having this machine, but SCP/SFTP/RSYNC access is declared in group B. In that case, as previously, as two different keys are used, this won't work.

To declare an SCP/SFTP/RSYNC access, in addition to a preexisting SSH access, you should use either:

In both cases, where you would use the --user option to the command, to specify the remote user to use for the SSH access being declared, you should replace it by either --protocol scpdownload, --protocol scpupload, --protocol sftp or --protocol rsync, to specify that you're about to add an SCP/SFTP/RSYNC access (and not a bare SSH one), and which direction you want to allow in the case of SCP.

For SCP, you can allow both directions by using the command first with --protocol scpdownload, then with --protocol scpupload. Note that for SFTP and RYSNC, you can't specify a direction, due to how these protocols work: you either have SFTP/RSYNC access (hence being able to upload and download files), or you don't.

For example, this is a valid command to add SFTP access to a machine which is part of a group:

bssh --osh groupAddServer --group mygroup --host scpserver.example.org --port 22 --protocol sftp

Error message 2

If you have the following message:

Sorry, but you don't seem to have access to HOST:IP

Then it means that you don't even have SSH access to this machine. In that case, somebody should grant you access, either by adding you to a group having this machine (groupAddMember) or by adding this machine to your personal accesses (accountAddPersonalAccess or selfAddPersonalAccess).