Title: How to use sshfs on OpenBSD

	Title: How to use sshfs on OpenBSD
	Author: Solène
	Date: 23 July 2022
	Tags: openbsd security
	Description: This simple guide explains how to use sshfs to use sshfs
	on OpenBSD

	# Introduction

	Today we will learn about how to use sshfs, a program to mount a remote
	directory through ssh into our local file system.

	But OpenBSD has a different security model than in other Unixes
	systems, you can't use FUSE (Filesystem in USErspace) file systems from
	a non-root user. And because you need to run your fuse mount program as
	root, the mount point won't be reachable by other users because of
	permissions.

	Fortunately, with the correct combination of flags, this is actually
	achievable.

	sshfs project website

	# Setup

	First, as root we need to install sshfs-fuse from packages.

	```shell
	# pkg_add sshfs-fuse
	```

	# Permissions errors when mounting with sshfs

	If we run sshfs as our user, we will get the error "fuse_mount:
	permission denied", so root is mandatory for running the command.

	But if we run "sshfs server.local:/home /mnt" as root, we can't reach
	the /mnt directory with our regular user because it's root property:

	```shell
	$ ls /mnt/
	ls: /mnt/: Permission denied
	```

	This confirms sshfs needs some extra flags to be used for non-root
	users on OpenBSD.

	# The solution

	As root, we will run sshfs to mount a directory from t470-wifi.local
	(my laptop Wi-Fi IP address on my LAN) to make it available to our user
	with uid 1000 and gid 1000 (this is the ids for the first user added),
	you can find the information about your users with the command "id".
	We will also use the allow_other mount option.

	```shell
	# sshfs -o idmap=user,allow_other,uid=1000,gid=1000 [email protected]:/hom…
	```

	After this command, when I switch to my user whose id and gid is 1000,
	I can read and write into /mnt.

	# Credits

	This article exists because many OpenBSD users struggle using sshfs,
	and it's not easy to find the solution on the Internet.

	OpenBSD as NAS FOSDEM talk giving an example of sshfs use
	= > https://marc.info/?l=openbsd-misc&m=153390693400573&w=2
	[email protected] email thread explaining why fuse mount behavior
	changed in 2018