saned

 

NAME

saned – SANE network daemon  

SYNOPSIS

saned [ -a [ username ] | -d [ n ] | -s [ n ] | -h ]  

DESCRIPTION

saned is the SANE (Scanner Access Now Easy) daemon that allows remote clients to access image acquisition devices available on the local host.  

OPTIONS

The -a flag requests that saned run in standalone daemon mode. In this mode, saned will detach from the console and run in the background, listening for incoming client connections; inetd is not required for saned operations in this mode. If the optional username is given after -a , saned will drop root privileges and run as this user (and group).

The -d and -s flags request that saned run in debug mode (as opposed to inetd(8) daemon mode). In this mode, saned explicitly waits for a connection request. When compiled with debugging enabled, these flags may be followed by a number to request debug info. The larger the number, the more verbose the debug output. E.g., -d128 will request printing of all debug info. Debug level 0 means no debug output at all. The default value is 2. If flag -d is used, the debug messages will be printed to stderr while -s requests using syslog.

If saned is run from inetd, xinetd or systemd, no option can be given.

The -h flag displays a short help message.  

CONFIGURATION

First and foremost: saned is not intended to be exposed to the internet or other non-trusted networks. Make sure that access is limited by tcpwrappers and/or a firewall setup. Don’t depend only on saned‘s own authentication. Don’t run saned as root if it’s not necessary. And do not install saned as setuid root.

The saned.conf configuration file contains both options for the daemon and the access list.

data_portrange = min_port – max_port

Specify the port range to use for the data connection. Pick a port range between 1024 and 65535; don’t pick a too large port range, as it may have performance issues. Use this option if your saned server is sitting behind a firewall. If that firewall is a Linux machine, we strongly recommend using the Netfilter nf_conntrack_sane module instead.

The access list is a list of host names, IP addresses or IP subnets (CIDR notation) that are permitted to use local SANE devices. IPv6 addresses must be enclosed in brackets, and should always be specified in their compressed form. Connections from localhost are always permitted. Empty lines and lines starting with a hash mark (#) are ignored. A line containing the single character “+” is interpreted to match any hostname. This allows any remote machine to use your scanner and may present a security risk, so this shouldn’t be used unless you know what you’re doing.

A sample configuration file is shown below:

# Daemon options
data_portrange = 10000 – 10100
# Access list
scan-client.somedomain.firm
# this is a comment
192.168.0.1
192.168.2.12/29
[::1]
[2001:db8:185e::42:12]/64

The case of the host names does not matter, so AHost.COM is considered identical to ahost.com.  

SERVER DAEMON CONFIGURATION

For saned to work properly in its default mode of operation, it is also necessary to add the appropriate configuration for (x)inetd or systemd. (see below). Note that your inetd must support IPv6 if you want to connect to saned over IPv6 ; xinetd, openbsd-inetd and systemd are known to support IPv6, check the documentation for your inetd daemon.

In the sections below the configuration for inetd, xinetd and systemd are described in more detail.

For the configurations below it is necessary to add a line of the following form to /etc/services:

sane-port 6566/tcp # SANE network scanner daemon

The official IANA short name for port 6566 is "sane-port". The older name "sane" is now deprecated.  

INETD CONFIGURATION

It is required to add a single line to the inetd configuration file (/etc/inetd.conf)

The configuration line normally looks like this:

sane-port stream tcp nowait saned.saned /usr/sbin/saned saned

However, if your system uses tcpd(8) for additional security screening, you may want to disable saned access control by putting “+” in saned.conf and use a line of the following form in /etc/inetd.conf instead:

sane-port stream tcp nowait saned.saned /usr/sbin/tcpd /usr/sbin/saned

Note that both examples assume that there is a saned group and a saned user. If you follow this example, please make sure that the access permissions on the special device are set such that saned can access the scanner (the program generally needs read and write access to scanner devices).  

XINETD CONFIGURATION

If xinetd is installed on your system instead of inetd the following example for /etc/xinetd.conf may be helpful:

# default: off
# description: The sane server accepts requests 
# for network access to a local scanner via the
# network.
service sane-port
{
   port        = 6566
   socket_type = stream
   wait        = no
   user        = saned
   group       = saned
   server      = /usr/sbin/saned
}

 

SYSTEMD CONFIGURATION

for systemd we need to add 2 configuation files in /etc/systemd/system.

The first file we need to add here is called saned.socket. It shall have the following contents:

[Unit]
Description=saned incoming socket

[Socket]
ListenStream=6566
Accept=yes
MaxConnections=1

[Install]
WantedBy=sockets.target

The second file to be added is [email protected] with the following contents:

[Unit]
Description=Scanner Service
Requires=saned.socket

[Service]
ExecStart=/usr/sbin/saned
User=saned
Group=saned
StandardInput=null
StandardOutput=syslog
StandardError=syslog
# Environment=SANE_CONFIG_DIR=/etc/sane.d SANE_DEBUG_DLL=255

Is you need to set an environment variable for saned like SANE_CONFIG_DIR you will have to remove the # on the last line and set the variable appropriately. Multiple variables can be set by separating the assignments by spaces as shown in the example above.

Unlike (x)inetd systemd allows debugging output from backends set using SANE_DEBUG_<backend_name> to be captured. With the service unit as described above, the debugging output is forwarded to the system log.  

FILES

/etc/hosts.equiv

The hosts listed in this file are permitted to access all local SANE devices. Caveat: this file imposes serious security risks and its use is not recommended.

/etc/sane.d/saned.conf

Contains a list of hosts permitted to access local SANE devices (see also description of SANE_CONFIG_DIR below).

/etc/sane.d/saned.users

If this file contains lines of the form

user:password:backend

access to the listed backends is restricted. A backend may be listed multiple times for different user/password combinations. The server uses MD5 hashing if supported by the client.

 

ENVIRONMENT

SANE_CONFIG_DIR

This environment variable specifies the list of directories that may contain the configuration file. Under UNIX, the directories are separated by a colon (`:’), under OS/2, they are separated by a semi-colon (`;’). If this variable is not set, the configuration file is searched in two default directories: first, the current working directory (".") and then in /etc/sane.d. If the value of the environment variable ends with the directory separator character, then the default directories are searched after the explicitly specified directories. For example, setting SANE_CONFIG_DIR to "/tmp/config:" would result in directories "tmp/config", ".", and "/etc/sane.d" being searched (in this order).