Documentation

2.5. macOS Installation

2.5.1. Overview

For macOS systems, SFTPPlus is distributed as a gzipped TAR archive. Installing SFTPPlus consists of unpacking the archive, initializing the configuration, and generating the SSH keys and the SSL key and certificate to be used by the product.

The included default configuration requires the creation of a system account, named sftpplus, under which the SFTPPlus process is executed.

Optionally, you may choose to start SFTPPlus as root, but the sftpplus user is still required in order to drop privileges after starting up.

To have SFTPPlus launched at boot, you may use the included plist file.

All steps beyond unpacking the archive can be handled by the shell script found at ./bin/install.sh in the hierarchy of SFTPPlus files.

2.5.2. Unpacking the archive

After downloading the compressed archive, you can extract its files using the following command:

tar xfz sftpplus-os-arch-version.tar.gz

To install SFTPPlus, move (or copy/link) the unpacked directory to your preferred installation path, for example: /Library/sftpplus.

SFTPPlus may be installed in any location on the local file system. In this documentation page we assume that SFTPPlus is unpacked in the /Library/sftpplus directory (we discuss INSTALL_ROOT more later). Avoid using spaces or special characters in the SFTPPlus installation path.

2.5.3. Shell script installer

The easiest way to install SFTPPlus is to execute the shell script found at ./bin/install.sh in the hierarchy of SFTPPlus files, for example:

/Library/sftpplus/bin/install.sh

The install.sh script will guide you through all the necessary steps.

After a successful installation using the shell script, jump to Listening on privileged ports to learn how to enable SFTPPlus to listen on privileged ports. This would be needed if SFTPPlus is not started with superuser privileges, which would mean it cannot bind ports below 1024.

2.5.4. Initializing the configuration

When installing SFTPPlus on a machine for the first time, you need to generate the initial configuration file and machine-specific SSH keys. A self-signed SSL certificate will also be generated to help with the initial FTPS and HTTPS testing.

To initialize a fresh SFTPPlus installation, execute the following command (where $ADMIN should be replaced with your favourite administrative username and $PASS with a password to be used for the SFTPPlus $ADMIN user):

cd /Library/sftpplus
./bin/admin-commands.sh initialize --init-admin $ADMIN --init-password $PASS

Default configuration allows external connections to the management web page. Therefore, use a secure password to protect the management web page.

Note

If you don't want to allow external connections to the Local Manager web-based console, append the --local-admin-access command line argument to the initialization command above:

./bin/admin-commands.sh initialize \
    --local-admin-access \
    --init-admin $ADMIN \
    --init-password $PASS

The initialization step is not required when upgrading SFTPPlus. It will not overwrite the configuration file, SSH keys, and SSL keys and certificates, if existing. In the case that you want to generate a new configuration, manually remove the existing files first.

2.5.5. Configuring the SFTPPlus process user and group

On macOS, SFTPPlus' process is managed by launchd.

The following are details for configuring the SFTPPlus account and group for macOS systems.

2.5.5.1. Configuring the process user and group on macOS

On macOS systems, SFTPPlus is able to drop privileges to a regular account even when launched as root. The default configuration takes this a step further, always running under a regular account, thus requiring a dedicated sftpplus operating system account to be created. Creating a dedicated new group and a new user for running SFTPPlus' process is therefore strongly recommended.

In the following examples we will use the default configuration value of sftpplus for the name of the user to run SFTPPlus.

2.5.5.2. Configuring the process user and group on macOS

To create an sftpplus group and a corresponding user on macOS, use the following commands.

You can replace the value of 299 from the below example commands with a unique ID for your system. On macOS, you can use dscacheutil -q user or dscacheutil -q group to identify the used IDs and pick a unique ID.

The below commands are included into an easy to use script which is available as osx_useradd.sh:

# Create the group dedicated to the service account.
sudo dscl . create /Groups/sftpplus
# Assign an unique ID to the group.
sudo dscl . create /Groups/sftpplus PrimaryGroupID 299
# Disable group password.
sudo dscl . create /Groups/sftpplus Password '*'
# Create a user for the service account.
sudo dscl . create /Users/sftpplus
# Assign a unique ID to the new user.
sudo dscl . create /Users/sftpplus UniqueID 299
# Assign this account to the dedicated group.
sudo dscl . create /Users/sftpplus PrimaryGroupID 299
# Disable shell access.
sudo dscl . create /Users/sftpplus UserShell /usr/bin/false
# Make sure it has a default empty home folder.
sudo dscl . create /Users/sftpplus NFSHomeDirectory /var/empty
# Disable password to block any authentication request.
sudo dscl . create /Users/sftpplus Password '*'
# Initialize blank password and authentication rules.
sudo dscl . delete /Users/sftpplus PasswordPolicyOption
sudo dscl . delete /Users/sftpplus AuthenticationAuthority

You need to adjust the ownership of the files, otherwise some of the functionality (logging and saving configuration changes) will not work:

cd /Library && chown -R root:admin sftpplus
cd /Library/sftpplus && chown -R sftpplus configuration/ log/ run/

At the very least, SFTPPlus needs read access to all the files under /Library/sftpplus, but in a typical installation it also requires write permission to the log/ subdirectory (for logging) and the configuration/ subdirectory (for saving changes to the running configuration). If running at all times under an unprivileged account, write permissions to the run/ sub-directory holding the PID file are needed as well.

2.5.6. Init system configuration for macOS

The next step is to configure your operating system to automatically start SFTPPlus on boot.

For macOS systems, you can use the example launchd job definition provided with SFTPPlus. The job definition file is formatted as XML, and it is called a property list file or 'plist'. Edit this file with your favourite editor, e.g. vi:

vi bin/sftpplus-mft.plist

The sample job definition file assumes that SFTPPlus is installed in the /Library/sftpplus directory. Depending on where the job definition is stored, it will be treated as a daemon or an agent. In order to have SFTPPlus act as a global daemon, launching each time the macOS system starts, you need to copy it in the appropriate place:

sudo cp bin/sftpplus-mft.plist /Library/LaunchDaemons/sftpplus.plist

After the file is copied, you need to instruct launchd to load/read the new job definition file using the command:

sudo launchctl load /Library/LaunchDaemons/sftpplus.plist

Note

During startup, the launchd process will scan and automatically load job definitions found in the /Library/LaunchDaemons directory.

To stop SFTPPlus, use the following command:

sudo pkill sftpplus-service

In the case that there are problems starting the server, you can check the log files at /var/log/system.log and /var/log/sftpplus-launchd.log.

You can read more about launchd on the official documentation page

2.5.7. Listening on privileged ports

When running SFTPPlus as a regular user, it's not possible to bind privileged ports in the range 0-1024.

One generic method which works on any Unix-like system is to set up SFTPPlus to listen on a port above 1024, then set up port-forwarding in your firewall configuration.

For example, to set up port-forwarding using pf, we can use the loopback interface to keep things simple. However, you should adapt and extend the exemplified firewall rules to account for your own local configuration: different network interfaces, IPs, and other network traffic rules.

Step-by-step instructions on how to forward port 122 to 10022:

Create a pf anchor file for sftpplus in /etc/pf.anchors/sftpplus
with the following contents:
    rdr pass on lo0 inet proto tcp from any to 127.0.0.1
    port = 122 -> 127.0.0.1 port 10022
    (note the above 2 lines go into only one line, it has been
    split here for better readability)

Reference anchor in /etc/pf.conf, add:
    rdr-anchor "sftpplus"
    load anchor "sftpplus" from "/etc/pf.anchors/sftpplus"

Enable and reload pf manually:
    $ sudo pfctl -ef /etc/pf.conf

Note: Updates to the OS may override the pf.conf file, make sure to
make a backup of it.

Note

In the case in which you know how to configure macOS to allow binding privileged ports without firewall redirection, please let us know and we will improve this documentation.

2.5.8. First Steps

After starting SFTPPlus, the Local Manager is a good way to visualize the current configuration that is available, and is even configurable itself.

We highly recommend going through the Getting Started on Windows guide or Getting Started on Linux guide first as it contains additional tips for new SFTPPlus installations.

There is also an FAQ section if you have an idea, but are in search of answers.

If you want to skip ahead, the Configuration Instructions or the Usage Instructions will contain detailed information to configure and operate SFTPPlus.