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Manual Page: SOCKD.CONF(5)
SOCKD.CONF(5) File Formats Manual SOCKD.CONF(5)
NAME
sockd.conf - Dante server configuration file syntax
DESCRIPTION
The configuration file for the Dante server controls both access
controls and logging. It is divided into three parts; server settings,
rules, and routes.
Note that server settings must come before rules and routes.
A line can be commented using the standard comment character #.
SERVER SETTINGS
The server settings control the generic behaviour of the server. Each
keyword is separated from it's value by a ':' character.
child.maxidle
Maintains a rough maximum on how many children of each type can
remain idle waiting for clients. This is used to reduce the
amount of idle processes after a "client burst" has passed. The
default is yes (maintain a maximum on how many processes can be
idle), which is the recommended value for optimal resource
usage.
It can be set to no if it is desirable to never shut down idle
processes. This can be used if client bursts are frequent and
it is important to serve them as fast as possible, with no delay
waiting for new server processes to be created, or to see how
many processes were used to handle the peak load.
clientmethod
A list of acceptable authentication methods for client-rules, in
order of preference. It is thus important that you specify
these in the correct order, normally with the more secure
methods first.
These are the authentication methods that can be checked before
the socks-negotiation has completed.
Supported values are none, gssapi, rfc931 and pam. For all
methods, except gssapi, that means the authentication will be
based on solely on the IP-address of the client, possibly in
combination with a rfc931 ("ident") lookup.
Any credentials provided during this pass will also be available
for use in later socks-rules, when the socks-request from the
client is evaluated.
The default value is all methods that may be necessary for the
later socks-based authentication, as specified in the socks-
method line. Normally you should not need to set this variable.
compatibility
With the sameport keyword, the server attempts to use the same
port on the server's external side as the client used on the
server's internal side. This is normally the default, but when
this option is given it will be done with privileged ports also.
The draft-5.05 keyword will enable usage of parts of the socks
v5-05 draft. The only feature from this draft that Dante
supports is the "USECLIENTSPORT" extension. Note that there is
a conflicting interpretation of this extension, so enabling it
might prevent clients using the conflicting interpretation from
working correctly. This only affects UDP.
debug Print debug info to the logs. The value sets the debug level.
errorlog
This value can be set to receive only error-related logoutput.
Note that this does not include client-specific errors, but only
more serious "global" errors.
The possible values are the same as for the logoutput keyword
mentioned below.
The intent is to have a special place that only serious errors
are logged so that they can discovered quickly. The default is
to not have any special place to log errors.
external
The address to be used for outgoing connections. The address
given may be either a IP address or an interface name. Can be
given multiple times for different addresses.
external.rotation
If more than one external address is given, this governs which
of the given addresses is selected as the source address for a
given outgoing connections/packet. Note that regardless of what
sort of external rotation you use, all addresses you want to
choose from must be listed via the external keyword first.
Valid values are none (the default), route, and same-same.
none indicates the first address on the list of external
addresses should be used.
route indicates the kernels routing table should be consulted to
find out what the source address for a given destination will
be, and might require you to set user.privileged to root. Note
that route might create problems for ftp-clients using active
ftp if the Dante bind extension is enabled for the ftp-client.
same-same indicates the source address for a given destination
should be the same address as the Dante server accepted the
client's connection on.
internal
The internal addresses. Connections will only be accepted on
these addresses. The address given may be either a IP address
or an interface name.
libwrap.hosts_access
If the server is compiled with libwrap support, determines
whether the hosts_access() function should be used for access
control. When enabled by setting this value to yes, the libwrap
library determines if TCP connections or UDP packets should be
immediately dropped or not, typically by consulting
/etc/hosts.allow and /etc/hosts.deny. These checks are applied
to all traffic, before the rule processing starts. The default
value is no (disabled).
logoutput
This value controls where the server sends logoutput. It can be
set to syslog[/facility], stdout, stderr, a filename, or a
combination. The default is nowhere. Note that if errorlog is
also set, there will be a overlap between what is logged there
(errors only), and what will be logged here (errors, and
everything else).
method A list of acceptable authentication methods for socks-rules, in
order of preference. It is thus important that you specify
these in the correct order, normally with the more secure
methods first.
Supported values are bsdauth, gssapi, none, pam, rfc931, and
username,
The default is no methods, which means all socks-requests will
be blocked. If a method is not set in this list it will never
be selected.
See the section on methods for an explanation of the different
methods and their meaning.
socket This keyword allows you to configure a few low-level socket
options that relate to the socket buffers the Dante server will
use when communicating with clients and target hosts. Note that
these buffers will normally use kernel memory and the kernel may
or may not honour the Dante server's request.
Normally there should be no need to set these values, and the
default values should suffice.
The keywords you can set are socket.recvbuf.udp,
socket.sendbuf.udp, socket.recvbuf.tcp, socket.sendbuf.tcp.
These control what socket buffersize the Dante server will ask
the kernel to use for the sockets. The numeric argument given
to the keyword indicates the size of the socket buffer in bytes.
You can set different values depending on the protocol (tcp or
udp), and on whether it is for receiving (recvbuf) or sending
(sendbuf) data.
srchost
This keyword allows you to configure a few options that relate
to the srchost, i.e., the host the Dante server accepts the
connections from.
With the nodnsmismatch keyword, the server will not accept
connections from addresses having a mismatch between DNS IP
address and hostname. Default is to accept them.
With the nodnsunknown keyword, the server will not accept
connections from addresses without a DNS record. Default is to
accept them.
With the checkreplyauth keyword, the server will check that the
authentication on bind-replies and udp-replies matches that
which is set in the rule and global method. Normally,
authentication is not desired on these replies, as they are
replies sent to the socks-clients, from non-socks clients, and
thus only a limited set of authentication methods are possible.
These methods are the methods not involving the socks protocol;
rfc931 and pam (using only the ipaddress and portnumber).
Default is not to check the authentication on replies.
timeout.connect
The number of seconds the server will wait for a connect
initiated on behalf of the socks-client to complete. The
default is 30. Setting it to 0 will use the systems default.
timeout.io
The number of seconds an established connection can be idle.
The default is 86400 (24 hours). Set it to 0 for forever. See
also the "-n" option in the sockd(8) manpage.
Individual timeouts can be set for TCP and UDP by suffixing io
with ".<protocolname>", i.e. timeout.io.tcp or timeout.io.udp.
Individual timeouts can also be set within rules, using the same
syntax. The timeout set in the rule will then override the
default timeouts for clients matching the rule.
timeout.negotiate
The number of seconds a client can spend negotiating with the
Dante server for a socks session before Dante will close the
connection to the client. The default is 30. Set it to 0 for
forever, though that is strongly discouraged.
timeout.tcp_fin_wait
The timeout for the equivalent of TCP's FIN-WAIT-2. The default
is 0, which means use the systems default (normally, no
timeout).
udp.connectdst
Enables or disables whether the server should attempt connecting
UDP sockets to the destination. Valid values are yes and no.
The default is yes, which improves UDP performance, but may not
be compatible with some UDP-based application protocols as it
means the server can only receive packets from the destination
address.
Userids
On platforms providing a privilege-model supported by Dante, the
Dante server does not use userid-switching via the seteuid(2)
system call. On other platforms, it is prudent to set the
userid to be used by the Dante server to appropriate values.
The Dante server can use two different userids, or three if
compiled with libwrap support. They are as follows:
user.privileged
Username which will be used for doing privileged operations. If
you need special privileges to read the sockd.conf file or to
write the sockd.pid file (you can create it manually before
starting sockd), have anything in your configuration that
requires binding privileged TCP/UDP ports (ports below 1024), or
use some sort of password-based authentication, this probably
needs to be set to root.
If not, you can probably set it to the same value as
user.unprivileged.
user.unprivileged
User which the server runs as most of the time. This should be
an id with as little privileges as possible. It is recommended
that a separate sockd userid is created for this.
user.libwrap
User used to execute libwrap commands. Normally this should be
the same as user.unprivileged
MODULES
The following modules are supported by Dante. Modules are purchased
separately from Inferno Nettverk A/S and may add extra functionality
that is not needed by most users. See the Dante homepage for more
information.
bandwidth
The bandwidth module gives you control over how much bandwidth
the Dante server uses on behalf of different clients.
redirect
The redirect module gives you control over what addresses the
server will use on behalf of the clients, aswell as allowing you
to redirect client requests to a different addresses.
session
The session module gives you control over the number of sessions
that can be created by different socks users.
AUTHENTICATION METHODS
The Dante server supports the following authentication methods. Some
installations of Dante may support only a subset of these.
none This method requires no form of authentication.
username
This method requires the client to provide a username and
password. This must match the username and password given in
the system password file.
gssapi This method requires the setup of a Kerberos environment and can
provide strong encryption and authentication.
rfc931 This method requires the client host to provide a rfc931
("ident") reply for the connecting client. This must match a
username given in the system password file.
pam This method requires the available client data to match against
the pam database.
bsdauth
This method requires the available client data to be verified by
the BSD Authentication system.
ADDRESSES
Each address field can consist of a IP address (and where required, a
netmask, separated from the IP address by a '/' sign), a hostname, a
domainname (designated so by the leading '.'), or an interface name.
Each address can be followed by a optional port specifier.
RULES
There are two sets of rules and they work at different levels. Rules
prefixed with client are checked first and are used to see if the
client is allowed to connect to the Dante server. We call them
"client-rules".
It is recommended that these do not use hostnames but only IP
addresses, both for security and performance reasons. These rules work
at the TCP level.
The other rules, which we call "socks-rules" are a level higher and are
checked after the client connection has been accepted by the client-
rules. The socks-rules are used to evaluate the socks request that the
client sends.
Both set of rules begin with a pass or deny keyword, but the client-
rules have "client " in front of the pass/deny keyword. The pass/deny
keyword determines whether connections matching the rule are to be
passed through or be blocked.
Both the client-rules and the socks-rules also specify a from/to
address pair which gives the addresses the rule will match.
In both contexts, from refers to the clients address, i.e., the address
the client is connecting to the Dante server from. The to address
however refers to different things depending on whether it is used in a
client-rule or in a socks-rule.
In the client-rule context, to means the address the request is
accepted on, i.e., a address the Dante server listens on.
In the socks-rule context, to means the client's destination address,
as expressed in the client's socks request. I.e., the address the
Dante server should connect to (for TCP sessions) or send packets to
(for UDP session) on behalf of the client.
Both set of rules are evaluated on a "first match is best match" basis.
That means, the first rule matched for a particular client or socks
request is the rule that will be used.
In addition to the addresses there is a set of optional keywords which
can be given. There are two forms of keywords; conditions and actions.
For each rule, all conditions are checked and if they match the
request, all actions are executed.
The list of condition keywords is: clientcompatibility, command, from,
group, method, protocol, proxyprotocol, to, user.
The list of action keywords is: bandwidth, libwrap, log, maxsessions,
redirect, timeout.connect, timeout.negotiate, timeout.io,
timeout.tcp_fin_wait, and udp.portrange.
The format and content of the the keyword as used in client-rules or
socks-rules is identical, but client-rules can contain only a subset of
the keyword that socks-rules may contain.
The contents of a client-rule can be:
bandwidth
The clients matching this rule will all share the given amount
of bandwidth, measured in bytes per second. Requires the
bandwidth module.
clientcompatibility
Enables certain options for compatibility with broken clients.
Valid values are: necgssapi, for compatibility with clients
implementing GSSAPI the NEC socks way.
from The rule applies to requests coming from the address given as
value.
group The user must belong to one of the groups given as value.
Note that if gssapi-based authentication is used, the username
as provided to the Dante server normally includes the Kerberos
domain. The name must be listed on the same form here and in
the system groupfile (usually /etc/passwd) if it is to be used.
gssapi.enctype
Which encryption to enforce for GSSAPI-authenticated
communication. Possible values are clear, integrity, or
confidentiality. The default is to accept whatever the client
offers.
gssapi.keytab
Value for keytab to use. The default is
"FILE:/etc/sockd.keytab".
gssapi.servicename
Which servicename to use when involving GSSAPI. Default is
"rcmd".
libwrap
The server will pass the line to libwrap for execution.
log Used to control logging. Accepted keywords are connect,
disconnect, data, error and iooperation. The default is no
logging.
maxsessions
Limit the number of active sessions allowed by this rule to the
given value. Requires the session module.
method Require that the connection be "authenticated" using one of the
given methods.
pam.servicename
Which servicename to use when involving pam. Default is
"sockd".
port Parameter to from, to and via. Accepts the keywords eq/=,
neq/!=, ge/>=, le/<=, gt/>, lt/< followed by a number. A
portrange can also be given as "port <start #> - <end #>", which
will match all port numbers within the range <start #> and <end
#>.
The default is all ports.
redirect
The source and/or destination can be redirected using the
redirect statement. Requires the redirect module.
The syntax of the redirect statement is as follows:
redirect from: ADDRESS
See the redirect manual for detailed information.
timeout.negotiate
See the global timeout.negotiate option.
to The rule applies to requests going to the address given as
value.
user The user must match one of the names given as value. If no user
value is given for a rule requiring usernames, the effect will
be the same as listing every user in the password file.
Note that if gssapi-based authentication is used, the username
as provided to the Dante server normally includes the Kerberos
domain. The name must be listed on the same form here if it is
to be used.
The contents of a socks-rule can be:
bandwidth
The clients matching this rule will all share the given amount
of bandwidth, measured in bytes per second. Requires the
bandwidth module.
bsdauth.stylename
The name of the BSD authentication style to use. The default is
to not specify a value, causing the default system style to be
used.
command
The rule applies to the given commands. Valid commands are
bind, bindreply, connect, udpassociate and udpreply. Can be
used instead of, or to complement, protocol. The default is all
commands valid for the protocols allowed by the rule.
from The rule applies to requests coming from the address given as
value.
group The user must belong to one of the groups given as value.
libwrap
The server will pass the line to libwrap for execution.
log Used to control logging. Accepted keywords are connect,
disconnect, data and iooperation.
maxsessions
Limit the number of active sessions allowed by this rule to the
given value. Requires the session module.
method Require that the connection be established using one of the
given methods. method always refers to the source part of the
rule. Valid values are the same as in the global method line.
pam.servicename
What servicename to use when involving pam. Default is "sockd".
port Parameter to from, to and via. Accepts the keywords eq/=,
neq/!=, ge/>=, le/<=, gt/>, lt/< followed by a number. A
portrange can also be given as "port <start #> - <end #>", which
will match all port numbers within the range <start #> and <end
#>.
The default is all ports.
protocol
The rule applies to the given protocols. Valid values are tcp
and udp. The default is all supported protocols that can apply
to the given commands.
proxyprotocol
The rule applies to requests using the given proxy protocol.
Valid proxy protocols are socks_v4 and socks_v5. The default is
all supported proxy protocols.
redirect
The source and/or destination can be redirected using the
redirect statement. Requires the redirect module.
The syntax of the redirect statement is as follows:
redirect from: ADDRESS
redirect to: ADDRESS
The semantics of from and to vary according to command. See the
redirect manual for detailed information.
timeout.connect
See the global timeout.connect option.
timeout.io
See the global timeout.io option.
timeout.tcp_fin_wait
See the global timeout.tcp_fin_wait option.
to The rule applies to requests going to or using the address given
as value. Note that the meaning of this address is affected by
command.
udp.portrange
The argument to this keyword is two portnumbers, separated by a
dash ('-'). They specify the UDP port-range that will be used
between the socks-client and the Dante-server for UDP packets.
Note that this has no relation to the UDP port-range used
between the Dante-server and external, non-socks,
clients/servers.
user The user must match one of the names given as value. If no user
value is given for a rule requiring usernames, the effect will
be the same as listing every user in the password file.
ROUTES
The routes are specified with a route keyword. Inside a pair of
parenthesis ({}) a set of keywords control the behavior of the route.
See socks.conf(5) for a description. This is used to perform so-called
"server-chaining", where one socks-server connects to another socks-
server further upstream.
Note that at present, server-chaining is only supported for the connect
command. See socks.conf(5) for more information about routes.
EXAMPLES
See the example directory in the distribution.
FILES
/etc/sockd.conf Dante server configuration file.
/etc/passwd file used when checking username/passwords.
AUTHORS
For inferno Nettverk A/S:
Michael Shuldman
Karl-Andre' Skevik
SEE ALSO
sockd(8), socks.conf(5), hosts_access(5) Information about new releases
and other related issues can be found on the WWW home page:
http://www.inet.no/dante/
November 1 2009 SOCKD.CONF(5)
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