- mdoc(7) style cleanup

- new version of security note from alex.

1 files changed, 300 insertions, 276 deletions

diff --git a/sbin/natd/natd.8 b/sbin/natd/natd.8
index 12cb27f..a0d56e5 100644
--- a/sbin/natd/natd.8
+++ b/sbin/natd/natd.8
@@ -1,152 +1,176 @@
-.\" manual page [] for natd 1.4
 .\" $FreeBSD$
-.Dd 15 April 1997
-.Os FreeBSD
+.Dd June 27, 2000
 .Dt NATD 8
+.Os FreeBSD
 .Sh NAME
 .Nm natd
-.Nd
-Network Address Translation Daemon
+.Nd Network Address Translation Daemon
 .Sh SYNOPSIS
-.Nm
-.Op Fl ldsmvu
-.Op Fl dynamic
-.Op Fl i Ar inport
-.Op Fl o Ar outport
-.Op Fl p Ar port
-.Op Fl a Ar address
-.Op Fl t Ar address
-.Op Fl n Ar interface
-.Op Fl f Ar configfile
-
-.Nm
-.Op Fl log
-.Op Fl deny_incoming
-.Op Fl log_denied
-.Op Fl use_sockets
-.Op Fl same_ports
-.Op Fl verbose
-.Op Fl log_facility Ar facility_name
-.Op Fl unregistered_only
+.Nm natd
+.Op Fl unregistered_only | u
+.Op Fl log | l
+.Op Fl proxy_only
+.Op Fl reverse
+.Op Fl deny_incoming | d
+.Op Fl use_sockets | s
+.Op Fl same_ports | m
+.Op Fl verbose | v
 .Op Fl dynamic
-.Op Fl inport Ar inport
-.Op Fl outport Ar outport
-.Op Fl port Ar port
-.Op Fl alias_address Ar address
-.Op Fl target_address Ar address
-.Op Fl interface Ar interface
-.Op Fl config Ar configfile
+.Op Fl in_port | i Ar port
+.Op Fl out_port | o Ar port
+.Op Fl port | p Ar port
+.Op Fl alias_address | a Ar address
+.Op Fl target_address | t Ar address
+.Op Fl interface | n Ar interface
+.Op Fl proxy_rule Ar proxyspec
 .Op Fl redirect_port Ar linkspec
 .Op Fl redirect_proto Ar linkspec
 .Op Fl redirect_address Ar linkspec
-.Op Fl reverse
-.Op Fl proxy_only
-.Op Fl proxy_rule Ar proxyspec
-
+.Op Fl config | f Ar configfile
+.Op Fl log_denied
+.Op Fl log_facility Ar facility_name
 .Sh DESCRIPTION
 This program provides a Network Address Translation facility for use
 with
 .Xr divert 4
-sockets under FreeBSD.  It is intended for use with NICs - if you want
-to do NAT on a PPP link, use the -nat switch to
+sockets under
+.Fx .
+It is intended for use with NICs - if you want to do NAT on a PPP link,
+use the
+.Fl nat
+switch to
 .Xr ppp 8 .
-
-.Pp
-.Nm Natd
-normally runs in the background as a daemon.  It is passed raw IP packets
-as they travel into and out of the machine, and will possibly change these
-before re-injecting them back into the IP packet stream.
-
-.Pp
-.Nm Natd
-changes all packets destined for another host so that their source
-IP number is that of the current machine.  For each packet changed
-in this manner, an internal table entry is created to record this
-fact.  The source port number is also changed to indicate the
-table entry applying to the packet.  Packets that are received with
-a target IP of the current host are checked against this internal
-table.  If an entry is found, it is used to determine the correct
-target IP number and port to place in the packet.
-
+.Pp
+The
+.Nm
+normally runs in the background as a daemon.
+It is passed raw IP packets as they travel into and out of the machine,
+and will possibly change these before re-injecting them back into the
+IP packet stream.
+.Pp
+It changes all packets destined for another host so that their source
+IP number is that of the current machine.
+For each packet changed in this manner, an internal table entry is
+created to record this fact.
+The source port number is also changed to indicate the table entry
+applying to the packet.
+Packets that are received with a target IP of the current host are
+checked against this internal table.
+If an entry is found, it is used to determine the correct target IP
+number and port to place in the packet.
 .Pp
 The following command line options are available.
 .Bl -tag -width Fl
-
 .It Fl log | l
 Log various aliasing statistics and information to the file
 .Pa /var/log/alias.log .
-This file is truncated each time natd is started.
-
+This file is truncated each time
+.Nm
+is started.
 .It Fl deny_incoming | d
-Reject packets destined for the current IP number that have no entry
-in the internal translation table.
-
+Do not pass packets destined for the current IP number that have no
+entry in the internal translation table.
 .It Fl log_denied
-Log denied incoming packets via syslog (see also log_facility)
-
+Log denied incoming packets via
+.Xr syslog 3
+.Po
+see also
+.Fl log_facility
+.Pc .
 .It Fl log_facility Ar facility_name
-Use specified log facility when logging information via syslog.
-Facility names are as in
-.Xr syslog.conf 5
-
+Use specified log facility when logging information via
+.Xr syslog 3 .
+Argument
+.Ar facility_name
+is one of the keywords specified in
+.Xr syslog.conf 5 .
 .It Fl use_sockets | s
 Allocate a
 .Xr socket 2
-in order to establish an FTP data or IRC DCC send connection.  This
-option uses more system resources, but guarantees successful connections
-when port numbers conflict.
-
+in order to establish an FTP data or IRC DCC send connection.
+This option uses more system resources, but guarantees successful
+connections when port numbers conflict.
 .It Fl same_ports | m
 Try to keep the same port number when altering outgoing packets.
 With this option, protocols such as RPC will have a better chance
-of working.  If it is not possible to maintain the port number, it
-will be silently changed as per normal.
-
+of working.
+If it is not possible to maintain the port number, it will be silently
+changed as per normal.
 .It Fl verbose | v
-Don't call
-.Xr fork 2
-or
+Do not call
 .Xr daemon 3
-on startup.  Instead, stay attached to the controling terminal and
-display all packet alterations to the standard output.  This option
-should only be used for debugging purposes.
-
+on startup.
+Instead, stay attached to the controling terminal and display all packet
+alterations to the standard output.
+This option should only be used for debugging purposes.
 .It Fl unregistered_only | u
-Only alter outgoing packets with an unregistered source address.
-According to rfc 1918, unregistered source addresses are 10.0.0.0/8,
+Only alter outgoing packets with an
+.Em unregistered
+source address.
+According to RFC 1918, unregistered source addresses are 10.0.0.0/8,
 172.16.0.0/12 and 192.168.0.0/16.
-
-.It Fl redirect_port Ar proto targetIP:targetPORT[-targetPORT] [aliasIP:]aliasPORT[-aliasPORT] [remoteIP[:remotePORT[-remotePORT]]]
+.It Fl redirect_port Ar proto Xo
+.Ar targetIP Ns : Ns Xo
+.Ar targetPORT Ns Op - Ns Ar targetPORT Xc
+.Op Ar aliasIP Ns : Ns Xo
+.Ar aliasPORT Ns Op - Ns Ar aliasPORT Xc
+.Oo Ar remoteIP Ns Oo : Ns
+.Ar remotePORT Ns Op - Ns Ar remotePORT
+.Oc Oc
+.Xc
 Redirect incoming connections arriving to given port(s) to another host
 and port(s).
-Proto is either tcp or udp, targetIP is the desired target IP
-number, targetPORT is the desired target PORT number or range, aliasPORT
-is the requested PORT number or range, and aliasIP is the aliasing address.
-RemoteIP and remotePORT can be used to specify the connection
-more accurately if necessary.
-The targetPORT range and aliasPORT range need not be the same numerically,
-but must have the same size.
-If remotePORT is not specified, it is assumed to be all ports.
-If remotePORT is specified, it must match the size of targetPORT, or be 0
-(all ports).
+Argument
+.Ar proto
+is either
+.Ar tcp
+or
+.Ar udp ,
+.Ar targetIP
+is the desired target IP number,
+.Ar targetPORT
+is the desired target port number or range,
+.Ar aliasPORT
+is the requested port number or range, and
+.Ar aliasIP
+is the aliasing address.
+Arguments
+.Ar remoteIP
+and
+.Ar remotePORT
+can be used to specify the connection more accurately if necessary.
+The
+.Ar targetPORT
+range and
+.Ar aliasPORT
+range need not be the same numerically, but must have the same size.
+If
+.Ar remotePORT
+is not specified, it is assumed to be all ports.
+If
+.Ar remotePORT
+is specified, it must match the size of
+.Ar targetPORT ,
+or be 0 (all ports).
 For example, the argument
-
+.Pp
 .Dl Ar tcp inside1:telnet 6666
-
-means that incoming tcp packets destined for port 6666 on this machine will
-be sent to the telnet port on the inside1 machine.
-
+.Pp
+means that incoming TCP packets destined for port 6666 on this machine
+will be sent to the telnet port on the inside1 machine.
+.Pp
 .Dl Ar tcp inside2:2300-2399 3300-3399
-
+.Pp
 will redirect incoming connections on ports 3300-3399 to host
 inside2, ports 2300-2399.
 The mapping is 1:1 meaning port 3300 maps to 2300, 3301 maps to 2301, etc.
-.It Fl redirect_proto Ar proto localIP Xo
-.Op Ar publicIP Op Ar remoteIP
-.Xc
+.It Fl redirect_proto Ar proto localIP Oo
+.Ar publicIP Op Ar remoteIP
+.Oc
 Redirect incoming IP packets of protocol
 .Ar proto
-.Pq see Xr protocols 5
+.Po see Xr protocols 5
+.Pc
 destined for
 .Ar publicIP
 address to a
@@ -164,26 +188,30 @@ will match the rule.
 .It Fl redirect_address Ar localIP publicIP
 Redirect traffic for public IP address to a machine on the local
 network.
-This function is known as "static NAT". Normally static NAT
-is useful if your ISP has allocated a small block of IP addresses to you,
-but it can even be used in the case of single address:
-
-  redirect_address 10.0.0.8 0.0.0.0
-
+This function is known as
+.Em static NAT .
+Normally static NAT is useful if your ISP has allocated a small block
+of IP addresses to you, but it can even be used in the case of single
+address:
+.Pp
+.Dl Ar redirect_address 10.0.0.8 0.0.0.0
+.Pp
 The above command would redirect all incoming traffic
 to machine 10.0.0.8.
-
+.Pp
 If several address aliases specify the same public address
 as follows
-
-  redirect_address 192.168.0.2 public_addr
-  redirect_address 192.168.0.3 public_addr
-  redirect_address 192.168.0.4 public_addr
-  
+.Bd -literal -offset indent
+.Ar redirect_address 192.168.0.2 public_addr
+.Ar redirect_address 192.168.0.3 public_addr
+.Ar redirect_address 192.168.0.4 public_addr
+.Ed
+.Pp
 the incoming traffic will be directed to the last
 translated local address (192.168.0.4), but outgoing
-traffic to the first two addresses will still be aliased
-to specified public address.
+traffic from the first two addresses will still be aliased
+to appear from the specified
+.Ar public_addr .
 .It Fl redirect_port Ar proto Xo
 .Ar targetIP Ns : Ns Xo
 .Ar targetPORT Ns Oo , Ns
@@ -232,66 +260,63 @@ option is used,
 .Nm
 will monitor the routing socket for alterations to the
 .Ar interface
-passed.  If the interfaces IP number is changed,
+passed.
+If the interface's IP number is changed,
 .Nm
 will dynamically alter its concept of the alias address.
-
-.It Fl i | inport Ar inport
+.It Fl in_port | i Ar port
 Read from and write to
-.Ar inport ,
+.Ar port ,
 treating all packets as packets coming into the machine.
-
-.It Fl o | outport Ar outport
+.It Fl out_port | o Ar port
 Read from and write to
-.Ar outport ,
+.Ar port ,
 treating all packets as packets going out of the machine.
-
-.It Fl p | port Ar port
+.It Fl port | p Ar port
 Read from and write to
 .Ar port ,
-distinguishing packets as incoming our outgoing using the rules specified in
+distinguishing packets as incoming our outgoing using the rules
+specified in
 .Xr divert 4 .
 If
 .Ar port
 is not numeric, it is searched for in the
-.Pa /etc/services
-database using the
-.Xr getservbyname 3
-function.  If this flag is not specified, the divert port named natd will
-be used as a default.  An example entry in the
-.Pa /etc/services
-database would be:
-
-  natd   8668/divert  # Network Address Translation socket
-
-Refer to
 .Xr services 5
-for further details.
-
-.It Fl a | alias_address Ar address
+database.
+If this option is not specified, the divert port named
+.Em natd
+will be used as a default.
+.It Fl alias_address | a Ar address
 Use
 .Ar address
-as the alias address.  If this option is not specified, the
-.Fl n
-or
+as the aliasing address.
+If this option is not specified, the
 .Fl interface
-option must be used.  The specified address should be the address assigned
-to the public network interface.
+option must be used.
+The specified address is usually the address assigned to the
+public network interface.
 .Pp
-All data passing out through this addresses interface will be rewritten
-with a source address equal to
+All data passing
+.Em out
+will be rewritten with a source address equal to
 .Ar address .
-All data arriving at the interface from outside will be checked to
-see if it matches any already-aliased outgoing connection.  If it does,
-the packet is altered accordingly.  If not, all
-.Fl redirect_port
+All data coming
+.Em in
+will be checked to see if it matches any already-aliased outgoing
+connection.
+If it does, the packet is altered accordingly.
+If not, all
+.Fl redirect_port ,
+.Fl redirect_proto
 and
 .Fl redirect_address
-assignments are checked and actioned.  If no other action can be made,
-and if
+assignments are checked and actioned.
+If no other action can be made and if
 .Fl deny_incoming
-is not specified, the packet is delivered to the local machine and port
-as specified in the packet.
+is not specified, the packet is delivered unaltered to the local
+machine and port as specified in the packet, but see the
+.Fl target_address
+option below.
 .It Fl t | target_address Ar address
 Set the target address.
 When an incoming packet not associated with any pre-existing link
@@ -299,171 +324,170 @@ arrives at the host machine, it will be sent to the specified
 .Ar address .
 .Pp
 The target address may be set to
-.Dq 255.255.255.255 ,
+.Ar 255.255.255.255 ,
 in which case all new incoming packets go to the alias address set by
 .Fl alias_address
 or
 .Fl interface .
 .Pp
 If this option is not used, or called with the argument
-.Dq 0.0.0.0 ,
+.Ar 0.0.0.0 ,
 then all new incoming packets go to the address specified in
 the packet.
 This allows external machines to talk directly to internal machines if
 they can route packets to the machine in question.
-.It Fl n | interface Ar interface
+.It Fl interface | n Ar interface
 Use
 .Ar interface
-to determine the alias address.  If there is a possibility that the
-IP number associated with
+to determine the aliasing address.
+If there is a possibility that the IP number associated with
 .Ar interface
 may change, the
 .Fl dynamic
-flag should also be used.  If this option is not specified, the
-.Fl a
-or
+option should also be used.
+If this option is not specified, the
 .Fl alias_address
-flag must be used.
+option must be used.
 .Pp
 The specified
 .Ar interface
-must be the public network interface.
-.It Fl f | config Ar configfile
+is usually the public network interface.
+.It Fl config | f Ar file
 Read configuration from
-.Ar configfile .
-.Ar Configfile
-contains a list of options, one per line in the same form as the
-long form of the above command line flags.  For example, the line
-
-  alias_address 158.152.17.1
-
-would specify an alias address of 158.152.17.1.  Options that don't
-take an argument are specified with an option of
+.Ar file .
+A
+.Ar file
+should contain a list of options, one per line, in the same form
+as the long form of the above command line options.
+For example, the line
+.Pp
+.Dl alias_address 158.152.17.1
+.Pp
+would specify an alias address of 158.152.17.1.
+Options that do not take an argument are specified with an option of
 .Ar yes
 or
 .Ar no
-in the configuration file.  For example, the line
-
-  log yes
-
-is synonomous with
+in the configuration file.
+For example, the line
+.Pp
+.Dl log yes
+.Pp
+is synonymous with
 .Fl log .
 .Pp
 Trailing spaces and empty lines are ignored.
 A
 .Ql \&#
 sign will mark the rest of the line as a comment.
-
 .It Fl reverse
-Reverse operation of natd.
-This can be useful in some 
-transparent proxying situations when outgoing traffic
-is redirected to the local machine and natd is running on the
-incoming interface (it usually runs on the outgoing interface).
-
+This option makes
+.Nm
+reverse the way it handles incoming and outgoing packets,
+allowing it to operate on the internal interface rather than
+the external one.
+.Pp
+This can be useful in some transparent proxying situations
+when outgoing traffic is redirected to the local machine
+and
+.Nm
+is running on the internal interface (it usually runs on the
+external interface).
 .It Fl proxy_only
-Force natd to perform transparent proxying
-only.
+Force
+.Nm
+to perform transparent proxying only.
 Normal address translation is not performed.
-
-.It Fl proxy_rule Ar [type encode_ip_hdr|encode_tcp_stream] port xxxx server a.b.c.d:yyyy
+.It Fl proxy_rule Xo
+.Op Ar type encode_ip_hdr | encode_tcp_stream
+.Ar port xxxx
+.Ar server a.b.c.d:yyyy
+.Xc
 Enable transparent proxying.
-Packets with the given port going through this
+Outgoing TCP packets with the given port going through this
 host to any other host are redirected to the given server and port.
 Optionally, the original target address can be encoded into the packet.
-Use 
-.Dq encode_ip_hdr
+Use
+.Ar encode_ip_hdr
 to put this information into the IP option field or
-.Dq encode_tcp_stream
+.Ar encode_tcp_stream
 to inject the data into the beginning of the TCP stream.
 .El
-
 .Sh RUNNING NATD
 The following steps are necessary before attempting to run
 .Nm natd :
-
 .Bl -enum
 .It
-Get FreeBSD version 2.2 or higher.  Versions before this do not support
-.Xr divert 4
-sockets.
-
-.It
 Build a custom kernel with the following options:
-
-  options IPFIREWALL
-  options IPDIVERT
-
+.Bd -literal -offset indent
+options IPFIREWALL
+options IPDIVERT
+.Ed
+.Pp
 Refer to the handbook for detailed instructions on building a custom
 kernel.
-
 .It
-Ensure that your machine is acting as a gateway.  This can be done by
-specifying the line
-
-  gateway_enable=YES
-
-in
-.Pa /etc/rc.conf ,
-or using the command
-
-  sysctl -w net.inet.ip.forwarding=1
-
+Ensure that your machine is acting as a gateway.
+This can be done by specifying the line
+.Pp
+.Dl gateway_enable=YES
+.Pp
+in the
+.Pa /etc/rc.conf
+file or using the command
+.Pp
+.Dl sysctl -w net.inet.ip.forwarding=1
+.Pp
 .It
-If you wish to use the
-.Fl n
-or
+If you use the
 .Fl interface
-flags, make sure that your interface is already configured.  If, for
-example, you wish to specify tun0 as your
+option, make sure that your interface is already configured.
+If, for example, you wish to specify tun0 as your
 .Ar interface ,
-and you're using
+and you are using
 .Xr ppp 8
 on that interface, you must make sure that you start
 .Nm ppp
 prior to starting
 .Nm natd .
-
-.It
-Create an entry in
-.Pa /etc/services :
-
-  natd          8668/divert  # Network Address Translation socket
-
-This gives a default for the
-.Fl p
-or
-.Fl port
-flag.
-
 .El
 .Pp
 Running
 .Nm
-is fairly straight forward.  The line
-
-  natd -interface ed0
-
-should suffice in most cases (substituting the correct interface name).  Once
+is fairly straight forward.
+The line
+.Pp
+.Dl natd -interface ed0
+.Pp
+should suffice in most cases (substituting the correct interface name).
+Once
 .Nm
-is running, you must ensure that traffic is diverted to natd:
-
+is running, you must ensure that traffic is diverted to
+.Nm natd :
 .Bl -enum
 .It
 You will need to adjust the
 .Pa /etc/rc.firewall
-script to taste.  If you're not interested in having a firewall, the
+script to taste.
+If you are not interested in having a firewall, the
 following lines will do:
-
-  /sbin/ipfw -f flush
-  /sbin/ipfw add divert natd all from any to any via ed0
-  /sbin/ipfw add pass all from any to any
-
-The second line depends on your interface (change ed0 as appropriate)
-and assumes that you've updated
-.Pa /etc/services
-with the natd entry as above.  If you specify real firewall rules, it's
-best to specify line 2 at the start of the script so that
+.Bd -literal -offset indent
+/sbin/ipfw -f flush
+/sbin/ipfw add divert natd all from any to any via ed0
+/sbin/ipfw add pass all from any to any
+.Ed
+.Pp
+The second line depends on your interface (change ed0 as appropriate).
+.Pp
+You should be aware of the fact that, with these firewall settings,
+everyone on your local network can fake his source-address using your
+host as gateway.
+If there are other hosts on your local network, you are strongly
+encouraged to create firewall rules that only allow traffic to and
+from trusted hosts.
+.Pp
+If you specify real firewall rules, it is best to specify line 2 at
+the start of the script so that
 .Nm
 sees all packets before they are dropped by the firewall.
 .Pp
@@ -472,37 +496,37 @@ After translation by
 packets re-enter the firewall at the rule number following the rule number
 that caused the diversion (not the next rule if there are several at the
 same number).
-
 .It
 Enable your firewall by setting
-
-  firewall_enable=YES
-
+.Pp
+.Dl firewall_enable=YES
+.Pp
 in
 .Pa /etc/rc.conf .
 This tells the system startup scripts to run the
 .Pa /etc/rc.firewall
-script.  If you don't wish to reboot now, just run this by hand from the
-console.  NEVER run this from a virtual session unless you put it into
-the background.  If you do, you'll lock yourself out after the flush
-takes place, and execution of
+script.
+If you do not wish to reboot now, just run this by hand from the console.
+NEVER run this from a remote session unless you put it into the background.
+If you do, you will lock yourself out after the flush takes place, and
+execution of
 .Pa /etc/rc.firewall
-will stop at this point - blocking all accesses permanently.  Running
-the script in the background should be enough to prevent this disaster.
-
+will stop at this point - blocking all accesses permanently.
+Running the script in the background should be enough to prevent this
+disaster.
 .El
-
 .Sh SEE ALSO
-.Xr socket 2 ,
-.Xr getservbyname 3 ,
 .Xr divert 4 ,
+.Xr protocols 5 ,
+.Xr rc.conf 5 ,
 .Xr services 5 ,
-.Xr ipfw 8
-
+.Xr syslog.conf 5 ,
+.Xr ipfw 8 ,
+.Xr ppp 8 .
 .Sh AUTHORS
 This program is the result of the efforts of many people at different
 times:
-
+.Pp
 .An Archie Cobbs Aq archie@whistle.com
 (divert sockets)
 .An Charles Mott Aq cmott@scientech.com