Content-type: text/html Manpage of IPSEC.CONF

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IPSEC.CONF

Section: File Formats (5)
Updated: 15 April 2000
Index Return to Main Contents

NAME

ipsec.conf - IPSEC configuration and connections

DESCRIPTION

The ipsec.conf file specifies most configuration and control information for the FreeS/WAN IPSEC subsystem. (The major exception is secrets for authentication; see ipsec.secrets(5).) Its contents are not security-sensitive unless manual keying is being done for more than just testing, in which case the encryption/authentication keys in the descriptions for the manually-keyed connections are very sensitive (and those connection descriptions are probably best kept in a separate file, via the include facility described below).

The file is a text file, consisting of one or more sections. White space followed by # followed by anything to the end of the line is a comment and is ignored, as are empty lines which are not within a section.

A line which contains include and a file name, separated by white space, is replaced by the contents of that file, preceded and followed by empty lines. If the file name is not a full pathname, it is considered to be relative to the directory containing the including file. Such inclusions can be nested. Only a single filename may be supplied, and it may not contain white space, but it may include shell wildcards (see sh(1)); for example:

include ipsec.*.conf

The intention of the include facility is mostly to permit keeping information on connections, or sets of connections, separate from the main configuration file. This permits such connection descriptions to be changed, copied to the other security gateways involved, etc., without having to constantly extract them from the configuration file and then insert them back into it. Note also the also parameter (described below) which permits splitting a single logical section (e.g. a connection description) into several actual sections.

A section begins with a line of the form:

type name

where type indicates what type of section follows, and name is an arbitrary name which distinguishes the section from others of the same type. (Names must start with a letter and may contain only letters, digits, periods, underscores, and hyphens.) All subsequent lines which begin with white space are part of the section; comments within a section must begin with white space too. There may be only one section of a given type with a given name.

Lines within the section are generally of the form

parameter=value

(note the mandatory preceding white space). There can be white space on either side of the =. The parameter names are specific to a section type. Unless otherwise explicitly specified, no parameter may appear more than once in a section.

An empty value stands for the default value (if any) of the parameter, i.e. it is roughly equivalent to omitting the parameter line entirely. A value may contain white space only if the entire value is enclosed in double quotes ("); a value cannot itself contain a double quote, nor may it be continued across more than one line.

Numeric values are specified to be either an ``integer'' (a sequence of digits) or a ``decimal number'' (sequence of digits optionally followed by `.' and another sequence of digits).

There is currently one parameter which is available in any type of section:

also: the value is a section name; the parameters of that section are appended to this section, as if they had been written as part of it. The specified section must exist, must follow the current one, and must have the same section type. (Nesting is permitted, and there may be more than one also in a single section, although it is forbidden to append the same section more than once.) This allows, for example, keeping the encryption keys for a connection in a separate file from the rest of the description, by using both an also parameter and an include line. (Caution, see BUGS below for some restrictions.)

Parameter names beginning with x- (or X-) are reserved for user extensions and will never be assigned meanings by IPSEC. Parameters with such names must still observe the syntax rules (name beginning with a letter and containing only letters, digits, underscores, and hyphens; value either containing no white space or enclosed in double quotes; no newlines or double quotes within the value). All other as-yet-unused parameter names are reserved for future IPSEC improvements.

A section with name %default specifies defaults for sections of the same type. For each parameter in it, any section of that type which does not have a parameter of the same name gets a copy of the one from the %default section. There may be multiple %default sections of a given type, but only one default may be supplied for any specific parameter name, and all %default sections of a given type must precede all non-%default sections of that type. %default sections may not contain also parameters.

Currently there are two types of section: a config section specifies general configuration information for IPSEC, while a conn section specifies an IPSEC connection.

CONN SECTIONS

A conn section contains a connection specification, defining a network connection to be made using IPSEC. The name given is arbitrary, and is used to identify the connection to ipsec_auto(8) and ipsec_manual(8). Here's a simple example:


conn snt
 left=10.11.11.1
 leftsubnet=10.0.1.0/24
 leftnexthop=33.44.55.66
 right=10.22.22.1
 rightsubnet=10.0.2.0/24
 rightnexthop=99.88.77.66
 keyingtries=0                # be very persistent

To avoid trivial editing of the configuration file to suit it to each system involved in a connection, connection specifications are written in terms of left and right participants, rather than in terms of local and remote. Which participant is considered left or right is arbitrary; IPSEC figures out which one it is being run on based on internal information. This permits using identical connection specifications on both systems.

Many of the parameters relate to one participant or the other; only the ones for left are listed here, but every parameter whose name begins with left has a right counterpart, whose description is the same but with left and right reversed.

Parameters are optional unless marked ``(required)''; a parameter required for manual keying need not be included for a connection which will use only automatic keying, and vice versa.

CONN PARAMETERS: GENERAL

The following parameters are relevant to both automatic and manual keying.

type: the type of the connection; currently the accepted values are tunnel (the default) signifying a host-to-host, host-to-subnet, or subnet-to-subnet tunnel; transport, signifying host-to-host transport mode; and passthrough (supported only for manual keying), signifying that no IPSEC processing should be done at all
auto: what operation, if any, should be done automatically at IPSEC startup; currently-accepted values are add (signifying an ipsec_auto add), start (signifying an ipsec_auto start), and ignore (also the default) (signifying no automatic startup operation). This parameter is ignored unless the plutoload or plutostart configuration parameter is set suitably; see the config setup discussion below.
left: (required) the IP address of the left participant's public-network interface, in any form accepted by ipsec_atoaddr(3). If it is the magic value %defaultroute, and interfaces=%defaultroute is used in the config setup section, left will be filled in automatically with the local address of the default-route interface (as determined at IPSEC startup time); this also overrides any value supplied for leftnexthop. (Either left or right may be %defaultroute, but not both.)
leftsubnet: private subnet behind the left participant, expressed as network/netmask; if omitted, essentially assumed to be left/32, signifying that the left end of the connection goes to the left participant only
leftnexthop: next-hop gateway IP address for the left participant's connection to the public network; defaults to right. If the value is to be overridden by the left=%defaultroute method (see above), an explicit value must not be given. If that method is not being used, but leftnexthop is %defaultroute, and interfaces=%defaultroute is used in the config setup section, the next-hop gateway address of the default-route interface will be used.
leftupdown: what ``updown'' script to run to adjust routing and/or firewalling when the status of the connection changes (default ipsec _updown). May include positional parameters separated by white space (although this requires enclosing the whole string in quotes); including shell metacharacters is unwise. See ipsec_pluto(8) for details.
leftfirewall: whether the left participant is doing forwarding-firewalling (including masquerading) for traffic from leftsubnet, which should be turned off (for traffic to the other subnet) once the connection is established; acceptable values are yes and (the default) no. May not be used in the same connection description with leftupdown. Implemented as a parameter to the default updown script.

If one or both security gateways are doing forwarding firewalling (possibly including masquerading), and this is specified using the firewall parameters, tunnels established with IPSEC are exempted from it so that packets can flow unchanged through the tunnels. (This means that all subnets connected in this manner must have distinct, non-overlapping subnet address blocks.) This is done by the default updown script (see ipsec_pluto(8)).

The implementation of this makes certain assumptions about firewall setup, notably the use of the old ipfwadm interface to the firewall. In situations calling for more control, it may be preferable for the user to supply his own updown script, which makes the appropriate adjustments for his system.

CONN PARAMETERS: AUTOMATIC KEYING

The following parameters are relevant only to automatic keying, and are ignored in manual keying.

keyexchange: method of key exchange; the default and currently the only accepted value is ike
auth: whether authentication should be done as part of ESP encryption, or separately using the AH protocol; acceptable values are esp (the default) and ah.
authby: how the two security gateways should authenticate each other; acceptable values are secret for shared secrets (the default) and rsasig for RSA digital signatures
leftid: how the left participant should be identified for authentication; defaults to left. Can be an IP address (in any ipsec_atoaddr(3) syntax) or a fully-qualified domain name preceded by @ (which is used as a literal string and not resolved).
leftrsasigkey: the left participant's public key for RSA signature authentication, in RFC 2537 format using ipsec_atobytes(3) encoding; the magic value %dns means to fetch it from DNS instead. Caution: if two connection descriptions specify different public keys for the same leftid, confusion and madness will ensue.
pfs: whether Perfect Forward Secrecy of keys is desired on the connection (with PFS, later compromise of the key-exchange protocol does not compromise the connection's keys); acceptable values are yes (the default) and no
keylife: how long a particular set of SAs (and hence keys) should be used, from successful negotiation to expiry; acceptable values are an integer optionally followed by s (a time in seconds) or a decimal number followed by m, h, or d (a time in minutes, hours, or days respectively) (default 8.0h, maximum 24h).
rekeymargin: how long before SA (and key) expiry should attempts to negotiate replacements begin; acceptable values as for keylife (default 9m)
rekeyfuzz: maximum percentage by which rekeymargin should be randomly increased to randomize rekeying intervals (important for hosts with many connections); acceptable values are an integer, which may exceed 100, followed by a `%' (default set by ipsec_pluto(8), currently 100%). The value of rekeymargin, after this random increase, must not exceed keylife. The value 0% will suppress time randomization.
keyingtries: how many attempts (an integer) should be made to negotiate a connection, or a replacement for one, before giving up (default 3); the value 0 means ``never give up''
ikelifetime: how long the connection to the other key-management daemon should last before being renegotiated; acceptable values as for keylife (default set by ipsec_pluto(8), currently 1h, maximum 8h).

CONN PARAMETERS: MANUAL KEYING

The following parameters are relevant only to manual keying, and are ignored in automatic keying. A manually-keyed connection must specify at least one of AH or ESP.

spi: (this or spibase required for manual keying) the SPI number to be used for the connection (see ipsec_manual(8)); must be of the form 0xhex, where hex is one or more hexadecimal digits (note, it will generally be necessary to make spi at least 0x100 to be acceptable to KLIPS)
spibase: (this or spi required for manual keying) the base number for the SPIs to be used for the connection (see ipsec_manual(8)); must be of the form 0xhex0, where hex is one or more hexadecimal digits (note, it will generally be necessary to make spibase at least 0x100 for the resulting SPIs to be acceptable to KLIPS)
esp: ESP encryption/authentication algorithm to be used for the connection, e.g. 3des-md5-96 (must be suitable as a value of ipsec_spi(8)'s --esp option); default is not to use ESP
espenckey: ESP encryption key (must be suitable as a value of ipsec_spi(8)'s --enckey option) (may be specified separately for each direction using leftespenckey (leftward SA) and rightespenckey parameters)
espauthkey: ESP authentication key (must be suitable as a value of ipsec_spi(8)'s --authkey option) (may be specified separately for each direction using leftespauthkey (leftward SA) and rightespauthkey parameters)
espreplay_window: ESP replay-window setting, an integer from 0 (the ipsec_manual default, which turns off replay protection) to 64; relevant only if ESP authentication is being used
leftespspi: SPI to be used for the leftward ESP SA, overriding automatic assignment using spi or spibase; typically a hexadecimal number beginning with 0x
ah: AH authentication algorithm to be used for the connection, e.g. hmac-md5-96 (must be suitable as a value of ipsec_spi(8)'s --ah option); default is not to use AH
ahkey: (required if ah is present) AH authentication key (must be suitable as a value of ipsec_spi(8)'s --authkey option) (may be specified separately for each direction using leftahkey (leftward SA) and rightahkey parameters)
ahreplay_window: AH replay-window setting, an integer from 0 (the ipsec_manual default, which turns off replay protection) to 64
leftahspi: SPI to be used for the leftward AH SA, overriding automatic assignment using spi or spibase; typically a hexadecimal number beginning with 0x

CONFIG SECTIONS

At present, the only config section known to the IPSEC software is the one named setup, which contains information used when the software is being started (see ipsec_setup(8)). Here's an example:


config setup
 interfaces="ipsec0=eth1 ipsec1=ppp0"
 klipsdebug=none
 plutodebug=all
 manualstart=
 plutoload="snta sntb sntc sntd"
 plutostart=

Parameters are optional unless marked ``(required)''. The currently-accepted parameter names in a config setup section are:

interfaces: (required) virtual and physical interfaces for IPSEC to use: a single virtual=physical pair, a (quoted!) list of pairs separated by white space, or %defaultroute, which means to find the interface d that the default route points to, and then act as if the value was ``ipsec0=d''. (Also, in the %defaultroute case, information about the default route and its interface is noted for use by ipsec_manual(8) and ipsec_auto(8).)
forwardcontrol: whether setup should turn IP forwarding on after IPSEC is started, and off before it is stopped; acceptable values are yes and (the default) no. For this to have full effect, forwarding must be turned off before the hardware interfaces are brought up (e.g., FORWARD_IPV4=false in Red Hat 5.x /etc/sysconfig/network), because IPSEC doesn't get control early enough to do that.
syslog: the syslog(2) ``facility'' name and priority to use for startup/shutdown log messages, default daemon.error.
klipsdebug: how much KLIPS debugging output should be logged. An empty value, or the magic value none, means no debugging output (the default). The magic value all means full output. Otherwise only the specified types of output (a quoted list, names separated by white space) are enabled; for details on available debugging types, see ipsec_klipsdebug(8).
plutodebug: how much Pluto debugging output should be logged. An empty value, or the magic value none, means no debugging output (the default). The magic value all means full output. Otherwise only the specified types of output (a quoted list, names without the --debug- prefix, separated by white space) are enabled; for details on available debugging types, see ipsec_pluto(8).
dumpdir: in what directory should things started by setup (notably the Pluto daemon) be allowed to dump core? The empty value (the default) means they are not allowed to.
dump: obsolete variant of dumpdir. dump=no is synonymous with dumpdir= and dump=yes is synonymous with dump=/var/tmp.
manualstart: which manually-keyed connections to set up at startup (empty, a name, or a quoted list of names separated by white space); see ipsec_manual(8). Default is none.
pluto: whether to start Pluto or not; Values are yes (the default) or no (useful only in special circumstances).
plutoload: which connections (by name) to load into Pluto's internal database at startup (empty, a name, or a quoted list of names separated by white space); see ipsec_auto(8) for details. Default is none. If the special value %search is used, all connections with auto=add or auto=start are loaded.
plutostart: which connections (by name) to attempt to negotiate at startup (empty, a name, or a quoted list of names separated by white space); any such names which do not appear in plutoload are implicitly added to it. Default is none. If the special value %search is used, all connections with auto=start are started.
plutowait: should Pluto wait for each plutostart negotiation attempt to finish before proceeding with the next? Values are yes (the default) or no.
plutobackgroundload: should loading and starting of connections be spun off as a background process to avoid startup delays? Values are yes or no (the default).

FILES

/etc/ipsec.conf

HISTORY

Designed for the FreeS/WAN project <http://www.xs4all.nl/~freeswan/> by Henry Spencer.

BUGS

Including attributes of the participant-to-participant negotiation (authentication methods, ikelifetime, etc.) as an attribute of an IPSEC connection, rather than of a security gateway, is dubious.

The keyingtries default should be 0.

Ipsec_manual is not nearly as generous about the syntax of subnets, addresses, etc. as the usual FreeS/WAN user interfaces. Four-component dotted-decimal must be used for all addresses. It is smart enough to translate bit-count netmasks to dotted-decimal form.

Putting an auto parameter in a conn %default section does not work. Analogously, an auto parameter cannot be acquired from a section appended by an also parameter.

It would be good to have a line-continuation syntax, especially for the very long lines involved in RSA signature keys.

The ability to specify different identities, authby, and public keys for different automatic-keyed connections between the same participants is misleading; this doesn't work dependably because the identity of the participants is not known early enough. This is especially awkward for the ``Road Warrior'' case, where the remote IP address is specified as 0.0.0.0, and that is considered to be the ``participant'' for such connections.

Index

NAME

DESCRIPTION

CONN SECTIONS

CONN PARAMETERS: GENERAL
CONN PARAMETERS: AUTOMATIC KEYING
CONN PARAMETERS: MANUAL KEYING

This document was created by man2html, using the manual pages.
Time: 04:38:14 GMT, May 22, 2000