NAME
ftp-proxy.conf - configuration file for FTP-Proxy
SYNOPSIS
/etc/proxy-suite/ftp-proxy.conf
DESCRIPTION
This manual page documents the configuration file format of the ftp-
proxy(8) program. FTP-Proxy is an application level gateway between
FTP clients and servers. Its main purpose is to secure servers against
attacks based on the FTP protocol.
The FTP-Proxy configuration file consists of option lines and comments.
A line starting with a ’#’ character is a comment. The general format
of a option line is
[WhiteSpace] Name WhiteSpace Value [WhiteSpace]
It is recommended to use up to 24 characters for the name and no more
than 1024 for the value, although theoretically both can be up to 4096
in size. Lines can be continued if the last character is a backslash.
The whole file is not case sensitive.
CONTEXT
Option lines always have a context which may be global or user
specific. A context is introduced by a [name] line, where name is the
FTP-login name or authuser if the UserAuthMagic feature is used. It is
allowed to use ’*’ wildcard character at the end of the context name
[name*] i.e. [foo*] to match multiple usernames beginning with "foo".
The beginning of the file is implicitly the [-Global-] context (the
dashes allow a user context named [global] without conflict). It is
legal to include an option more than once; the last one will be the one
used. Options in user contexts usually take precedence over the
equivalent global option.
Some of the options can be used in a user or the global context, while
others make sense only in one of them. See below.
VARIABLE SUBSTITUTION
Several options (see the individual discussion below for details)
support a limited set of variable substitution when evaluated. The
following replacements will be performed:
%b build date of the ftp-proxy(8) program
%d current system date in the form YYYY/MM/DD
%h host name from gethostname(2)
%n network name from getdomainname(2)
%t current system time in the form HH:MM:SS
%v version of the ftp-proxy(8) program
%% a single percent sign
OPTIONS
ActiveMaxDataPort
Both user and global context. Defines the maximum local port
number used when connecting to the client’s data port. The
latter is either the same as the client’s control port or the
one given in the most recent PORT command. If either minimum or
maximum value is not given, the program defaults to using port
20, the ftp-data port as per RFC 959, for the local end of the
socket if the proxy is running as root (user ID 0) or to use a
random port. See also ActiveMinDataPort and User options.
ActiveMinDataPort
Both user and global context. Defines the minimum local port
number used when connecting to the client’s data port. See also
ActiveMaxDataPort and User options.
AllowMagicUser
Global context only. Defines a flag that when set to yes, true,
or on allows the USER name to be optionally interpreted as
user[@host[:port]] where host overrides the DestinationAddress
and port the DestinationPort directive below. It should only be
activated with "trusted" users, like in an outgoing FTP proxy
scenario. See also the UserMagicChar and ForceMagicUser options.
AllowTransProxy
Global context only. Defines a flag that when set to yes, true,
or on allows to use the proxy as transparent proxy for outgoing
ftp. To get it working you also have to redirect client
requests on a gateway or firewall host (i.e. via ipchains) to
the ftp-proxy. It should only be activated with "trusted"
users, like in an outgoing FTP proxy scenario. You can combine
this with the AllowMagicUser option.
DenyMessage
Global context only. Defines the name of a file which prevents
any successful login if it exists, even if it is empty. The
file contents will be sent to the client, each line prefixed
with ’421-’ and with variable substitution applied. The whole
file is followed by a line starting with ’421 ’ followed by the
DenyString below. After sending the connection is closed. If
no such file exists, the deny mechanism is not triggered
altogether. See also DenyString option.
DenyString
Global context only. Defines a string that will be displayed to
clients, prefixed with ’421 ’ and variable substitution applied,
if and only if a DenyMessage file exists. The default is
’Service not available’. See also DenyMessage option.
DestinationAddress
Both user and global context. Defines where to redirect
incoming FTP traffic. Can be given as either dotted decimal IP
address or as DNS host name. Please note that the global
section must always contain this option as a basic sanity check.
DestinationMaxPort
Both user and global context. Defines the maximum local port
number to be used when opening a connection to the FTP server.
Valid both for control and for data connections. Defaults to
not binding prior to connecting and listening, so that the
system selects an arbitrary ephemeral port. See also
DestinationMinPort option.
DestinationMinPort
Both user and global context. Defines the minimum local port
number to be used when opening a connection to the FTP server.
See also DestinationMaxPort option.
DestinationPort
Both user and global context. Defines the FTP server’s control
port where the proxy itself will connect. This option can
either be given as a numeric value or as the service name
retrieved by getservbyname(3) and defaults to port 21, the ftp
port as per RFC 959.
DestinationTransferMode
Both user and global context. Defines the FTP transfer mode to
be used from the proxy to the server. Legal values are active,
passive, or client. The latter means to follow the mode the
client is using. The default value is client.
FailResetsPasv
Global context only. Defines the action that is taken when a
data transfer command is failed on the server side. If the
option is set to yes, true, or on the client data transfer
socket will be closed and the transfer mode set to the default
(active-ftp).
If this flag is set to no, false, or off (which is also the
default) the socket can be reused for the next data transfer
command in passive mode. This options is a workaround for
Netscape (4.x) clients, that sends a second data transfer
command if the first is failed, while the user clicks on a
symbolic link pointing to a directory.
Note, that this behavior may break the RFC definitions.
ForceMagicUser
Global context only. Same as AllowMagicUser, but makes the host
and port portion mandatory.
ForkLimit
Global context only. Limits the number of incoming client
connections per minute in daemon mode - it defaults to 40
connections per minute.
Group Global context only. Defines the UNIX style group ID which is
set by the process before it serves clients. Default is to keep
the current real group ID.
LDAPAuthDN
Global context only. Defines a different base distinguished
name that is used when accessing an LDAP directory for user
authentication purposes. It defaults to the value of LDAPBaseDN.
See also LDAPAuthPWAttr, LDAPAuthPWType, LDAPAuthOKFlag,
UserAuthType, LDAPBindDN options.
LDAPAuthOKFlag
Global context only. Defines an attribute and its value as
attr=value string, i.e. userEnabled=yes, that will be checked
while user authentication in the directory tree specified using
LDAPAuthDN or LDAPBaseDN. Defaults to an empty string - no flag
check used.
LDAPAuthPWAttr
Global context only. Defines the LDAP password attribute name
used for user authentication.
A common used attribute name is userPassword. Defaults to an
empty string - password authentication disabled. See also
LDAPAuthPWType option.
LDAPAuthPWType
Global context only. Defines the LDAP password type / format
and a minimal allowed password length expected as value for
attribute name specified using LDAPAuthPWAttr.
Valid values are plain, crypt, {crypt} followed by one number
0-9, i.e. {crypt}7, plain9 or plain.
If no minimum length specified the default minimum length of 5
characters is used.
A password type {crypt} means, the password value in the LDAP
directory is prefixed by the {crypt} scheme specification. Other
password schemes, i.e. MD5, are not supported at the moment.
Crypted passwords are only avaliable, if the proxy is compiled
with crypt support - see also --with-crypt compile time option
in configure script.
If the password (without scheme prefix) stored in LDAP directory
is * or ! the account is disabled and the authentication fails.
Defaults to plain (equivalent to plain5). See also the
LDAPAuthOKFlag.
LDAPBaseDN
Global context only. Defines the base distinguished name that
is used when accessing an LDAP directory, i.e. the root of the
tree containing the FTP-Proxy entries. Defaults to an empty
string. If UserAuthMagic is used, the authuser is used as user
name for authentication and user profiles, otherwise the normal
ftp-user name. See also LDAPIdentifier, LDAPObjectClass,
LDAPServer, UserAuthMagic options.
LDAPBindDN
Defines the distinguished name that is used to (simple) bind the
directory service. Defaults to an empty string (anonymous bind).
It is allowed to include one %s in this string, that will be
replaced with the FTP username or authuser if UserAuthMagic is
used. See also UserAuthMagic, LDAPAuthDN, LDAPBindPW options.
LDAPBindPW
Defines the credential (password) that is used to (simple) bind
the directory service using distinguished name given in the
LDAPBindDN option. Defaults to an empty string (anonymous bind).
LDAPIdentifier
Global context only. Defines the identification attribute for
the access to the LDAP directory. This can be thought of as the
primary key and defaults to the string CN which is short for
"Common Name." See also LDAPBaseDN, LDAPObjectClass, LDAPServer
options.
LDAPObjectClass
Global context only. Defines the LDAP object class which holds
the entries for the FTP-Proxy access control. It is assumed
that the possible user specific config options exist as
attributes within a record of this type. There is no default,
but a value of FTPProxyUser is recommended. See also
LDAPBaseDN, LDAPIdentifier, LDAPServer options.
LDAPServer
Global context only. This is the main option for using an LDAP
directory for retrieving user specific values. If given, it
denotes the server (and possible port separated by a colon)
where FTP-Proxy will ask for the attributes. The program will
bind as the anonymous user and try to retrieve the values from
the tree rooted at LDAPBaseDN, having an object class of
LDAPObjectClass and identified by the LDAPIdentifier. If the
server cannot be reached, the program aborts. If the user
cannot be found, the program falls back to the configuration
file, but will query only the global values and not the user
specific ones. See also LDAPBaseDN, LDAPBindDN, LDAPIdentifier,
LDAPObjectClass options.
LDAPVersion
Global context only. Use this option to set the LDAP API
version, the proxy should set: 2 or 3. Use 0 to skip explicit
version setting and use library defaults. Defaults is version 3
if supported by the library or 2 if not.
Note: OpenLDAP 2.x library defaults to version 2 bind, but the
OpenLDAP server refuses LDAPv2 bind by default.
Listen Global context only. Defines the address where the proxy itself
opens the listening port. The default is 0.0.0.0 which
instructs the server to bind to any address. See also Port
option.
LogDestination
Global context only. Defines the destination of the logging
information the program wishes to emit. If the value starts
with a slash (/) it will be interpreted as an absolute path.
This file will be created and kept open during the lifetime of
the process. The signal SIGUSR1 can be sent to the (daemon)
process in order to rotate this log file.
A second way to provide logging is via a pipe and is employed
when the first character of the option is a pipe symbol (|). In
this case the rest of the value is interpreted as the name of a
UNIX command which is invoked and receives logging information
on its standard input.
The third way is to use the syslog(3) service which is assumed
for all other values. The option value is interpreted as the
syslog facility while the severity is defined by the various
messages themselves.
LogLevel
Global context only. Defines the maximal level of logged
messages. The levels are, in order of decreasing importance:
FLT, ERR, WRN, INF, DBG
The default level is INF. A LogLevel set to WRN causes, that
only messages with levels FLT, ERR, WRN will be logged.
MaxClients
Global context only. Defines the maximum number of clients the
proxy will allow concurrently. The valid range for this option
is 1 to 512, with a default of 64. See also MaxClientsMessage,
MaxClientsString options.
MaxClientsMessage
Global context only. Defines the name of a file that is
displayed to clients if their maximum number defined with
MaxClients has been exceeded. If no such file exists only the
MaxClientsString is displayed, else both the file and the string
are transmitted. After transmission the connection is
terminated in any case. When sending the file, each line is
prefixed with ’421-’ and variable substitution is applied to it.
See also MaxClients, MaxClientsString options.
MaxClientsString
Global context only. Defines a string that will be displayed to
clients, prefixed with ’421 ’ and variable substitution applied,
if the maximum client number has been exceeded. The default is
’Service not available’ . See also MaxClients,
MaxClientsMessage options.
MaxRecvBufSize
Global context only. Defines the maximum number of bytes read
from socket at once while data transfers. Default is to read all
data as reported by the kernel.
It may be useful to set a limit (i.e. to 8192), if your proxy
machine uses two interfaces of different speed, i.e. the clients
are accessing the proxy via a high-speed interface (i.e. Fast-
Ethernet) and the proxy is accessing servers using a slower one
(i.e. modem, ISDN link) and your ftp-clients aborts the data
transfers because of a timeout.
PassiveMaxDataPort
Both user and global context. Defines the maximum local port
number used when listening for the client’s data connection.
This is the port number transmitted to the client in a 227
response to the PASV command. If either minimum or maximum
value is not given, the program defaults to let the system
choose an arbitrary ephemeral port. See also PassiveMinDataPort
option.
PassiveMinDataPort
Both user and global context. Defines the minimum local port
number used when listening for the client’s data connection.
See also PassiveMaxDataPort option.
PidFile
Global context only. Defines the name of a process ID file
where FTP-Proxy will store its process ID if running as daemon.
The file contents will be an ASCII string with a trailing
newline. On many operating systems such PID files will be
located in the /var/run directory.
Port Global context only. Defines the listening port where the FTP-
Proxy offers its service. The port can be given as a number or
as a string suitable for retrieval by the getservbyname(3)
function. It defaults to port 21, the ftp port as per RFC 959.
See also Listen option.
PortResetsPasv
Global context only. Defines the action that is taken when a
PORT command is received while a passive port is open for
listening. If the option is set to yes, true, or on, (which is
also the default) the socket will be closed and the passive mode
will be terminated (set to active-ftp). Setting the option to
no, false, or off does not cancel the listen. This flag seems
necessary because the RFC is not really clear enough about the
correct handling.
SameAddress
Both user and global context. Defines a boolean value which
determines if the proxy is allowed to be included in so-called
third party server to server transfers. In this situation the
client first sends a PASV command to one server, then a PORT
command with the response code to the second server, and then
initiates the transfer with mutual transfer commands on the two
servers. Specifying this option as no, false, or off allows
FTP-Proxy to take part in such a transfer, while saying yes,
true, or on (the default) will enforce that transfers can only
take place to/from the client itself.
ServerRoot
Defines the directory into which the FTP-Proxy performs a
chroot(2) in order to increase its security level. See also the
User and Group options.
Note, that you have to copy needed libraries, configuration
files, etc into this directory first!
ServerType
Global context only. Defines the mode in which the FTP-Proxy is
running if no command line switch (-d/-i) has been provided.
The option value can either be inetd in which case the proxy
expects the client to be available at standard input and output,
or it can be standalone which means the process will become a
daemon, open the listening port and fork child processes for all
future connections. The child processes themselves will behave
exactly as if they were started from inetd.
SockBindRand
Global context only. Defines a flag that when set to yes, true,
or on , causes the proxy to use a random port in the specified
range via DestinationMinPort/MaxPort, ActiveMinPort/MaxDataPort,
PassiveMinDataPort/MaxDataPort instead of increment the port
number inside of this range. See also DestinationMinPort,
DestinationMaxPort, PassiveMinDataPort, PassiveMaxDataPort,
ActiveMinPort, ActiveMaxPort options.
TCPWrapper
Global context only. Defines a boolean value which is evaluated
by the FTP-Proxy running as a standalone daemon only. Saying
yes, true, or on activate the TCP Wrapper library, whereas no,
false, or off (the default) disable the function. See also
TCPWrapperName option.
TCPWrapperName
Global context only. Use given name for TCP-Wrapper checks
instead of the program name (argv[0]). See also TCPWrapper
option.
TimeOut
Both user and global context. Defines the time in seconds after
which a client is assumed to be disconnected. If no activity is
detected from the client after this time, the connection is
closed and the process terminates. Default value is 900
seconds.
TranslatedAddress
Global context only. Defines an IP address the server will use
in 227 replies to PASV commands instead of its own address.
Usually the address where the client connected to is taken, but
this may not be appropriate in situations where an NAT (Network
Address Translation) device is located in the way from the
client to the proxy. In this situation the response can be
changed to include the input address of the NAT device.
The value for this option can be given as a DNS host name, as a
dotted decimal IP address, or as a file name. The latter is
assumed when the name starts with a slash. The file is opened
and scanned for the desired address. Blank lines or lines
starting with ’#’ are ignored. Reading the address from a file
may be useful for environments with masquerading and dynamic PPP
connections.
User Global context only. Defines the UNIX style user ID which is
given to the process before it serves clients. Default is to
keep the current real user ID.
If the proxy does not run as a privileged user (root, user ID
0), it has no permission to bind a socket to port < 1024 or to
preform a chroot(2) call. See also ActiveMinDataPort,
ActiveMaxDataPort, ServerRoot options.
UserMagicChar or UseMagicChar
Global context only. Defines the character to use as separator
between user and host[:port] in the target setting of
AllowMagicUser Default is the ’@’ character. This allows you to
use E-Mail addresses as usernames for login to the ftp server
(i.e. me@mydomain%ftp.server:21 if you set it to %).
UserAuthMagic
Global context only. This is an authentication extension like
AllowMagicUser, allowing encoding of additional username and
password in the USER and PASS commands for authentication.
Valid values are @auth for ftpuser@authuser[@host:port] and
ftppass@authpass or auth@ for authuser@[ftpuser@host:port] and
authpass@ftppass. See also LDAPBindDN, LDAPAuthType and
AllowMagicUser.
UserAuthType
Global context only. Defines the authentication mechanism the
proxy should use. Currently "ldap" is implemented to support
simple LDAP authentication using FTP username and password from
USER and PASS commands or the special authuser and authpass
encoded using UserAuthMagic. See also LDAPBindDN, LDAPAuthDN,
LDAPAuthPWAttr, LDAPAuthPWType, LDAPAuthOKFlag and UserAuthMagic
options.
UserNameRule
Global context only. Defines a regular expression rule for
validation of the user name (used for profile-setup and
authentication purposes). Defaults to:
^[[:alnum:]]+([%20@/\._-][[:alnum:]]+)*$
It checks, if the first character is alphanumeric, optionally
followed by @/_-. or alphanumeric characters and ending with an
alphanumeric one.
This matches the usual cases inclusive E-Mail adresses and
"domain/user" names.
If regex support is not avaliable, above default rule is still
used and the option ignored. See also ValidCommands option for
regex encoding description.
ValidCommands
Both user and global context. Defines the list of allowed FTP
commands for the client. If this option is not installed, there
will be no restriction on the allowed commands. But if it is
given, then all commands not on this list will be denied. The
list is space separated and may consist of the following
commands: USER, PASS, ACCT, CWD, CDUP, SMNT, QUIT, REIN, PORT,
PASV, TYPE, STRU, MODE, RETR, STOR, STOU, APPE, ALLO, REST,
RNFR, RNTO, ABOR, DELE, RMD, MKD, PWD, LIST, NLST, SITE, SYST,
STAT, HELP, NOOP, SIZE, MDTM, MLFL, MAIL, MSND, MSOM, MSAM,
MRSQ, MRCP, XCWD, XMKD, XRMD, XPWD, XCUP, AUTH, APSV, EPRT, and
EPSV.
Each command can be followed by an optional equals sign and
POSIX 1003.2 Extended Regular Expression (RE) that describes the
valid argument(s) for the command. If the whole string is to be
matched, the pattern has to start with a caret (^) and end with
a dollar ($). If no pattern follows a command, its arguments
are not checked. An example for a name would be the pattern
’^[a-zA-Z0-9]{1,512}$’ for an argument that is mandatory and may
consist of up to 512 letters or digits only. A command that
does not allow any arguments can also easily be represented:
’QUIT=^$’ .
Please note that the regular expression is "pre-processed".
This means that a pattern in the form %xx will be interpreted as
a hexadecimal constant and will be replaced by the value of that
constant. This looks a bit like HTML and helps to include
characters that might not be handled as expected, like %20 for
space or %5c (equivalent to %5C) for backslash. The space is
especially important because it is the separator for the
commands within the list itself.
Please note also that regular expression support must have been
enabled with the --with-regex switch during the configure
compilation step of the whole package.
WelcomeMessage
Global context only. Defines the name of a file that will be
displayed to all clients as the first action when they open the
control connection. Each line is prefixed with ’220-’ and
variable substitution is applied to it. If no such file exists
it is silently ignored. See also WelcomeString option.
WelcomeString
Global context only. Defines the string that is sent to the
client in order to start login negotiation. The string is
prefixed with ’220 ’ and variable substitution is applied to it.
If this option is not given it defaults to the following string:
’%h FTP server (%v - %b) ready’.
See also WelcomeMessage option.
FILES
/etc/proxy-suite/ftp-proxy.conf
/usr/sbin/ftp-proxy
SEE ALSO
ftp-proxy(8)
The SuSE Proxy-Suite documentation included in the doc subdirectory of
the package.
AUTHORS
Jens-Gero Boehm <jens-gero.boehm@suse.de>
Pieter Hollants <pieter.hollants@suse.de>
Volker Wiegand <volker.wiegand@suse.de>
Marius Tomaschewski <mt@suse.de>
COPYRIGHT
The SuSE Proxy-Suite is released under the
GNU General Public License (GPL).