ZEBEDEE(1) Zebedee ZEBEDEE(1)NAME
Zebedee --- a simple, free, secure TCP and UDP tunnel program
SYNOPSIS
Server:
zebedee-s [common-options] [-c host] [-C num] [-r ports] [target
...]
Client:
zebedee [-m] [-e command]
[server] [tunnel-spec ...]
Common Options:
zebedee [-dDLtuU] [-b address] [-F char] [-f file] [-K
checksumlevel] [-k keybits] [-n name] [-o log] [-T port] [-v level]
[-x config] [-z level] ...
Key generation:
zebedee-p [-f file]
zebedee-P [-p] [-f file]
Hash generation:
zebedee-h [file ...]
zebedee-H string ...
Windows Service:
zebedee [-n name] -S [install[=file] | remove | run]
UNIX-like only
zebedee [-N userid] ...
DESCRIPTION
Zebedee is a simple program to establish an encrypted, compressed
"tunnel" for TCP/IP or UDP traffic between two systems. This allows
data from, for example, telnet, ftp and X sessions to be protected from
snooping. You can also use compression, either with or without data
encryption, to gain performance over low-bandwidth networks.
This document describes the features of Zebedee as at release 2.5.3.
For details of the new features in this release see CHANGES.
The main goals for Zebedee are to:
· Provide client and server functionality under both UNIX/Linux and
Windows.
· Be easy to install, use and maintain with little or no
configuration required.
· Have a small footprint, low wire protocol overhead and give
significant traffic reduction by the use of compression.
· Use only algorithms that are either unpatented or for which the
patent has expired.
· Be entirely free for commercial or non-commercial use and
distributed under the term of the GNU General Public Licence (see
"CREDITS AND LEGALITIES").
Of course, Zebedee is by no means the first, or only secure tunnel
program available. It does not pretend to compete with the likes of ssh
or SSL in terms of breadth of function but if you want something quick,
simple and completely free then it may be the tool for you.
What's in a name?
In case you were wondering, or even if you weren't, Zebedee is named
after its three main components:
· Zlib compression
· Blowfish encryption and
· Diffie-Hellman key agreement.
So now you know!
Basic Usage
To set up a secure connection between your local machine and a remote
host you need first to run Zebedee in server mode on the remote system.
The easiest way to do this is to run Zebedee with the -s option (but
please read the notes on security issues later):
zebedee-s
If all goes well (and it should!) Zebedee will detach from the terminal
(or console window under Windows) and run in the background. It will
then be listening for incoming requests from clients.
On your local machine you then run Zebedee in client mode. You need to
specify the name of the remote machine and the name of the service or
number of the port to which the tunnel should be established --- we
will call this the "target" port. If the remote machine is called
"remhost" and you want to set up a secure telnet session then you would
run:
zebedee remhost:telnet
In fact, if you don't specify a service or port the default is telnet
so
zebedee remhost
would do just as well in this instance. When you run this command it
will print out a message telling you the port number which is the local
end of the tunnel. Zebedee will then detach from the terminal and run
in the background waiting for you to connect to the local port. If, for
example, the port number it printed out was 1234 then to connect to
"remhost" using the secure tunnel you would run:
telnet localhost 1234
By default, Zebedee will continue to listen for connections and tunnel
them, handling multiple simultaneous connections if necessary, until
you terminate the process.
Sometimes you will want to start Zebedee and then run a command that
connects to the port straight away. You can do this in a single
invocation of Zebedee as follows:
zebedee-e "telnet localhost %d" remhost
The "%d" in the string is automatically replaced with the local port
number so there is no need for Zebedee to print it out. If you specify
a command like this then the local Zebedee client will exit once the
command closes its connection.
You may want or need to control the local port number that the client
uses. This is necessary if the command whose connection you are trying
to protect expects to connect only to a specific port. In this case you
can also specify the local port number by invoking Zebedee as follows:
zebedee clientport:hostname:targetport
So, for example, the command:
zebedee 8000:webhost:80
will allow you to secure all HTTP connections to webhost if accessed
via port 8000 on the client system. See EXAMPLES for more details.
You can also use a single Zebedee client to handle multiple
simultaneous tunnels to different target ports on the same remote host.
In this case the client and target port specifications are lists of
ports. For example:
zebedee 9001,9002,9003:somehost:daytime,telnet,ftp
This will tunnel traffic on the clientport 9001 to the daytime port on
the remote target system, traffic on 9002 to the telnet port and
traffic on 9003 to the ftp port.
This combination of client listening ports, target host and destination
ports is called a "tunnel specification". See the tunnel keyword for
more details.
UDP Tunnelling
Originally Zebedee was designed only to be able to handle TCP/IP
traffic. It can now also handle connectionless UDP data. To enable
this start Zebedee with the -U option (or use the ipmode keyword). For
example:
zebedee-s -U
on the server host and
zebedee-U 10000:somehost:echo
on the client. When run in this way Zebedee will handle both TCP and
UDP traffic.
The tunnel between Zebedee clients and servers still uses a TCP/IP
connection even in UDP-mode. This connection is timed out after a
certain period of inactivity. It must be re-established if more data
arrives. For this reason the performance in UDP mode may appear poor,
depending on the nature of the application using it. You should note
that there is also a limit on the size of UDP datagrams that can be
handled.
For further details see the maxbufsize, ipmode, udptimeout and
tcptimeout keywords.
Some Terminology
Usually there will only be two systems involved when you set up a
tunnel using Zebedee. You will run a client on one and communicate with
it via connections to local ports. On the other you will run a server
which will speak to services local to that machine. However, there can
be up to four different systems involved, as shown below:
[source] <===> [client] <=====> [server] <===> [target]
| | |
+- insecure | + insecure
connection | connection
+- secure tunnel
The Zebedee client runs on the "client" system and the server runs on
the "server" host. The inital connection that causes a tunnel to be
established between client and server originates from the "source"
machine. This could be a different system than where the Zebedee client
is running, although it is usually the same. The server will ultimately
communicate with the "target" system. Again, this is usually the local
machine but does not have to be.
Most of the time you will not have to be concerned with the distinction
between source and client and server and target. The terminology is,
however, reflected in a number of the keywords described in the
following section so you should bear it in mind when reading their
descriptions.
In addition to the different systems involved in Zebedee tunnel there
are also several different types of keys used to secure connection. The
client and server generate or are provided with private key values.
These are used to calculate public values which are exchanged and used
to derive a shared secret key using the Diffie-Hellman key agreement
mechanism. From this shared key a unique session key is derived to
secure an individual connections between client and server.
Multiple Destinations
A single Zebedee client/server pair can handle tunnels for multiple
targets, not just the system on which the Zebedee server is running.
When a server is started it can be given a list of valid targets either
on the command-line or by using the target keyword. Each target is a
host name optionally followed by a list of ports to which connections
may be made. Consider the following command run on a machine called
serverhost:
zebedee-s target1:daytime,telnet target2:telnet target3
the server will allow connections to the daytime and telnet ports on
target1, the telnet port on target2 and any port on target3.
Given this server invocation, a client may be started as follows:
zebedee serverhost 10000:target1:telnet 20000:target3:telnet
This will connect to the Zebedee server on serverhost and use it to
establish tunnels to the telnet port on target1 via the client port
10000 and tunnels to the telnet port on target3 via 20000. Note that
the name of the host on which the server is running is given as the
first parameter. If the server name is omitted it is determined from
the first tunnel specification. So if the server had been running on
target3 then the above command could have been given as:
zebedee 20000:target3:telnet 10000:target1:telnet
In fact, a server also maintains a notion of a default target. This is
the host name of the last target specified. In the example server
invocation above the default target becomes target3. This is the target
used when the server and target names specified by the client are the
same. Be careful of this because you may get results that you do not
expect. For example, if the server was started on "target3" as:
zebedee-s target2:telnet target3 target1:daytime,telnet
then the following client invocation:
zebedee 20000:target3:telnet
would result in connections to port 20000 being tunnelled to target1
and not target3. This is because when the server and target specified
by the client are the same then the traffic goes to the server's
default target. To avoid confusion, if you want to include the server
host in a list of multiple destinations then always name it last. Note
that as well as a default target host it is also possible to specify a
list of default allowed target ports where none are otherwise given.
See the redirect keyword for more details.
As with the target keyword for the server, the equivalent of the
command-line parameter for the client is the tunnel keyword (and
serverhost in order to specify the server host explictly).
Server-Initiated Connections
In normal use a Zebedee client inititates connections to the server
when a connection has been made to it from a source system. Sometimes,
for example when using Zebedee through a restrictive firewall, it may
be necessary for the server to initiate the connection back to the
client --- to operate in "reverse." For details on how to do this see
the clienthost and listenmode keywords.
Configuration File
The behaviour of Zebedee is probably best controlled through the use of
a configuration file. A configuration file can be specified using the
-f command-line option. The file is read at the point at which the
option is encountered so later command-line options may override the
contents of the file.
Lines are of the form:
keyword value # optional comment
The keyword is a single, case-insensitive word. The value is either a
single word or a string. Strings are enclosed either in double quotes
("like this") or single quotes ('like this'). Double quotes may appear
in single quoted strings and vice versa ("here's an example"). Case is
preserved in the values where appropriate.
Blank lines and lines beginning with a ""#"" (after any leading
whitespace) are ignored. Long strings may be continued onto the next
line by ending the line with a ""\"" character. This character is
eliminated and the next line is joined on to the end. Note that there
is a limit of a total of 1024 characters on any line and its
continuations. Line continuation happens before anything else,
including comment recognition so the lines:
server false
# This comment continues on the next line \
server true
will leave the value of server as false.
The keywords and their meanings are as described below. There is a
brief description of all the keywords in the "Quick-Reference Summary"
section. Some, but not all, keywords have equivalent command-line
options. These are shown where available. There are also a few
command-line options that have no equivalent in the configuration file.
These are described at the end of this section.
If a keyword is described as being a boolean then its value must be one
of the words true or false.
Several keywords require a list of ports to be specfied. Where this the
case the value is string that consists of a comma or white-space
delimited list of port names, numbers or numeric ranges. For example
""telnet, ftp 5900-5903"". This is equivalent to the list
""23,21,5900,5901,5902,5903"". You can also specify that a particular
port or range should only be used for TCP or UDP traffic by suffixing
it with ""/tcp"" or ""/udp"". If this suffix is omitted it can be used
for either type. So, the list ""telnet/tcp,daytime/udp,echo"" specifies
TCP-only traffic to the "telnet" port, UDP-only traffic to the
"daytime" port and either to the "echo" port.
A number of the keywords are either only applicable to clients or only
applicable to servers. The same Zebedee program runs as either client
or server and will silently ignore inappropriate options for the
current type of usage. The choice of client or server behaviour is
controlled by the server keyword:
server (command-line -s)
This is a boolean indicating whether the program should run as a
client or a server. The default is to run as a client if this
keyword is not specified. The command-line -s option is equivalent
to setting this keyword to true.
targetconnecttimeout
This specifies the about of time, in seconds, that a server should
block trying to connect to a target host. The default is 300
seconds.
Client-Only Keywords
The following keywords apply only to Zebedee clients:
command (command-line -e)
When running as a client, this is a command that will be spawned to
run connected to the tunnel. If the value contains the character
sequence "%d" this will be replaced at run-time with the local port
number (see the tunnel keyword). As this is done using sprintf the
conventions of that routine apply with regards to escaping ""%""
characters (i.e. use ""%%"" to generate a single ""%""). In
addition, specifying more that one "%d" or other format sequence
will very likely crash the program.
Once the command closes its connection Zebedee will exit. Using
this keyword or option implicitly turns off multi-use mode (see
multiuse). You can not use automatic command spawning when a single
Zebedee client is handling multiple connections in multiuse mode or
when a list of ports has been specified with the tunnel keyword or
on the command-line.
listenmode (command-line -l)
In normal use a Zebedee client inititates connections to the server
when a connection has been made to it from a source system.
Sometimes, for example when using Zebedee through a restrictive
firewall, it may be necessary for the server to initiate the
connection with a client --- to operate in "reverse."
The listenmode keyword, if true, causes a Zebedee client to listen
for connections initiated by the server rather than to connect
directly. The client will listen for connections at the network
level but the connection from the server will not be fully accepted
and activated until a matching connection from the source system
has been received. Equally, a client will accept connections from
source clients but no data will be read from or sent to these
connections until a connection has been made with a server.
Normally a client makes a connection to a specific server address.
Server-initiated connections could, however, originate from
arbitrary addresses, thus giving the client no control over the
destination of the tunnel. To avoid this the client will validate
that the address of the server's connection matches that specified,
whether on the command-line, via the serverhost keyword or as part
of the first tunnel specification. (The client can also use the
checkaddress keyword to perform such checking).
When using listenmode the server address can also contain a network
mask. So the following client invocation:
zebedee-l 10000:10.10.10.0/24:telnet
will accept connections from any address on the 10.10.10.0 class C
subnet. As a special case, if the server name is ""*"" then
connections will be accepted from any server address. Use of the
identity checking features is also recommended to ensure that the
correct server connects.
If a connection from a server is not received within a certain
period then the connection back to the source system will be closed
and the process abandoned. This timeout is controlled by the
acceptconnecttimeout keyword. The default is 300 seconds.
See the clienthost keyword for the description of the server side
of this process.
localsource
If this value is true then the client will only accept connections
originating from the local machine. In other words the "source"
system must be the same as the "client" system.
The default is for this value to be false and for connections to be
allowed from any arbitrary source machine.
This has been superseded by the more generic listenip keyword. So
""localsource true"" is equivalent to ""listenip 127.0.0.1"".
multiuse (command-line -m)
If this value is true, which is the default, then the Zebedee
client will handle multiple (potentially simultaneous) connection
requests and will establish a new tunnel to the server for each
one. If it is false, the client runs in "single-use" mode and exits
after the first connection to the server has been closed.
The command-line -m option is equivalent to setting this to true.
This is the default behaviour in the current version of Zebedee and
the option is retained only for backwards-compatibility reasons.
Any client listening on multiple ports will automatically run in
"multi-use" mode, even if this is set false (see clientport).
serverhost
This is the name of the host on which a Zebedee server is running
and to which a tunnel is to be connected. There is no default and
a host name must be specified either in a configuration file or on
the command line.
See the listenmode keyword for the treatment of this value when
using server-initiated connections.
Prior to version 2.0.0 this was known as the remotehost keyword.
This is still recognised for backwards compatibility.
tunnel
This is a string that consists of three parts separated by colons,
for example:
10000-10002:targethost:echo,telnet,daytime
The first part is the list of ports on which the Zebedee client
will listen for connections. The second part is the name of the
target host to which the tunnelled data should be directed. The
final part is the list of target ports that correspond to the ports
on which the client is listening. The numbers of entries in the
client and target port lists must match.
As a special case, if only a single tunnel specification is given
with only a single target port then the client port list (and
separating colon) may be omitted. The client port will be assigned
automatically (and a message will be printed to the terminal giving
the port number). This is to allow for backwards compatibility and
for use with the command keyword. If the target port is also
omitted then it will default to telnet (port 23).
As described in the section "Multiple Destinations" if the Zebedee
server host is not explicitly specified, either as the first
argument on the command-line or via the serverhost keyword, then it
will be taken from the first tunnel specification found.
There is also one final variant of the tunnel specification. In
this case the targethost is replaced by a ""*"". This wild-card
form is used either with the client running in "listen-mode" (see
listenmode for further details) or when you want to specify
tunnelling to the server's default target, whatever it may be. This
latter form is useful in a configuration file when you want the
file to be generically applicable to any server. For example, a
file like this:
server false
tunnel 10000:*:daytime
tunnel 20000:*:echo
tunnel 30000:*:telnet
can be used to set up tunnels on ports 10000, 20000 and 30000 to
whatever host may be specified on the command-line like this:
zebedee-f configfile serverhost
Server-Only Keywords
The following keywords apply only when running as a server:
clienthost (command-line -c)
If a clienthost value is specified then the server will immediately
attempt to connect to the specified host (on the port given by
serverport). Once a connection to the client has been established
the protocol exchanges proceed as normal. Each time a connection
has been accepted by the client the server tentatively opens up
another one so that the client could establish further tunnels if
necessary.
Three other keywords affect this behaviour. The
serverconnecttimeout keyword determines how long the server will
spend trying to make a connection. If it cannot immediately connect
to the client it will wait this many seconds before trying again.
Once a connection has been established the server will wait up to
acceptconnecttimeout seconds for the client to accept the
connection and start the protocol exchange. Finally, this whole
process will be repeated up to connectattempts times. If a
connection is not opened and accepted within this number of
attempts the server will exit once all currently active tunnels
have been closed.
Note that Zebedee does not itself provide a mechanism for co-
ordinating the starting of client and server to set up a "reverse"
tunnel. That must be handled by some "out-of-band" mechanism.
connectattempts (command-line -C)
This specifies the number of attempts the server makes to connect
back to a client when a clienthost is given. The default is 1.
dropunknownprotocol
This is a boolean indicating whether a Zebedee server should
attempt to continue negotiating a connection with a client that
requests a version of the Zebedee protocol that the server can not
support. By default this is false, meaning that the server will
reply with the highest protocol version it supports, allowing the
client to decide if it can continue. If set to true, the server
will immediately terminate the connection.
See also lockprotocol.
redirect (command-line -r)
This is the default list of the ports on the target system to which
the server will accept requests to redirect data, when the target
specification does not otherwise specify a port range. An example
port list might be ""telnet, ftp, 5900-5910"".
If no redirect keyword is specified then requests to redirect
traffic to any port will be accepted. While this is convenient for
testing it may pose a security risk so you should specify an
explict list of allowed ports if at all possible. As a special
case, if the port range is given as ""none"" then any current
default redirection list will be cleared and no target ports will
be accepted by default.
The keyword (or -r option) may be specified multiple times in which
case redirection will be allowed to any of the ports specified.
It is generally better to use the target keyword instead of
redirect, where possible. The main reason to prefer redirect is
when you want to specify a common range of ports for a number of
targets, for example:
# Set up common target redirections
redirect telnet,ftp,daytime
target hosta
target hostb
target hostc
# Set up additional host-specific redirections
target hostb:http
target
This specifies a target host and, optionally, list of ports to
which a server will accept requests to redirect data. It is a
string consisting of the target host name followed by a colon and
then a list of ports. For example
target www.winton.org.uk:http,ftp
If the port list (and colon) are omitted then requests for
redirection will be controlled by the ports given by the redirect
statements, if any.
The target hostname may also be specified as a CIDR network
address, that is an address with the number of bits to be used for
the network mask, for example:
target 10.10.10.0/24:http
This means that HTTP connections to any host address in the
255-host class C subnet will be accepted.
This keyword is equivalent to the comnmand-line arguments of the
same form (see "Multiple Destinations"). It may be repeated
multiple times. The final target host specified, either using the
this keyword or on the command line, becomes the default
destination for tunnels when a client specifies the server's host-
name as the destination.
Be careful when using CIDR addresses as targets that the last
target specified will be valid default address. If the default
target has an address mask then Zebedee will flag this as an error
and exit.
It is also possible to apply identity checking and source IP
address validation, like that provided by checkidfile and
checkaddress, to individual targets. If the target is suffixed with
a ""?"" followed by a file name, such as this:
target 10.10.10.0/24:http?httpusers.ids
then the file ("httpusers.ids" in this example) must be a file in
the same format as that described in the identity checking section.
The effect of this target specification is to allow connections to
be created to the HTTP port of any machine in the 10.10.10.0/24
sub-net, but only by clients whose identities are found in
"httpusers.ids".
Similarly, the target can be suffixed with ""@"" followed by an
address specification in the same form as that used by
checkaddress. For example:
target 10.10.10.0/24:http@10.20.30.0/24
In this case only clients in the 10.20.30.0/24 sub-net will be
permitted to create tunnels to this target.
You can't combine both the ""?"" and ""@"" forms. But you really
wouldn't want to do that anyway, would you?
targetconnecttimeout
This sets maximum timeout for server attempting to make a
connection to a target endpoint. Normally a connection attempt will
fail immediately if there is no target server running. However,
with certain kinds on network or system failures connection
attempts can block almost indefinitely. This timeout prevents these
hangs. The default is 300 seconds.
transparent
This is a boolean value, which is false by default. If set true it
causes the Zebedee server to attempt to propagate the client's IP
address to the target server --- for the existence of the server to
become "transparent".
This functionality will not work on all platforms and Zebedee will
have to be run as a privileged user (e.g. "root" on UNIX-like
systems) in order for it to work at all. Full transparency support
for TCP and UDP traffic is currently only expected work on Linux
and then only on systems with kernel versions 2.0 and 2.2. It will
not work on Linux 2.4, although there is some hope that it may work
in future versions.
Support for a limited form of transparency for UDP traffic is
available for a wider range of UNIX-like platforms, although this
must have been enabled at compile time (it is not enabled by
default in the "standard" builds). If it has been enabled then
unidirectional UDP traffic from client to server will preserve the
Zebedee client's IP address on datagrams sent to the target server.
This will be sufficient for applications such as "syslog" where
there is no requirement that the target server should reply to such
traffic. Applications that attempt to reply to the address in
these datagrams will not send replies via the Zebedee tunnel and,
in fact, are likely to send their data to non-existent or invalid
endpoints.
Compression, Encryption and Checksum Keywords
The following keywords control the compression, encryption and
checksumming of data passing through the tunnel. They apply to both
clients and servers:
checksumlevel (command-line -K)
Zebedee will, by default, calculate a checksum for every message
sent over the tunnel. This checksum is appended to the message and
verified by the recipient. If the checksum calculated by the
recipient does not match that in the message the tunnel connection
will be terminated. You should note that for the checksum to be
effective as a means of assuring that data has not been maliciously
modified, you should ensure that the data is also encrypted.
The checksumlevel is an integer between 0 and 3 that determines the
checksumming algorithm used to check the integrity of data
transferred by Zebedee. The default is 2. This provides a
reasonable level of assurance, at the price of a 4-byte overhead on
each message and some extra computation. Setting this to 0 turns
off checksumming (which was the behaviour prior to Zebedee version
2.5).
The checksum level used will be the minimum of the client's and
server's values (subject to any setting of minchecksumlevel).
The algorithms used and the overhead they imply are as follows:
Level 0
No checksum, no additional overhead.
Level 1
This uses the "ADLER32" algorithm from zlib. It requires a
4-byte overhead per message. The algorithm is fast but gives
the lowest degree of assurance that the message has not been
modified or corrupted in transit.
Level 2
This uses the "CRC32" algorithm from zlib. It requires a 4-byte
overhead per message. This is a little slower than "ADLER32"
but provides a better level of assurance of the data integrity.
Level 3
This uses the "SHA" algorithm. It requires a 20-byte overhead
per message. This is the most CPU-intensive operation but
provides a very high degree of assurance that the contents of
the message have not been altered in transit.
compression (command-line -z)
Zebedee can support both zlib and, if enabled when it is built,
bzip2 compression. This keyword specifies the type and level of
compression to be used. The value is of the form type:level where
type is either ""zlib"" or ""bzip2"" and level is an integer from 0
to 9. As a special case an integer without any prefix implicitly
selects a zlib compression level.
The level specifies the maximum compression level to used (9 is the
maximum and 0 is no compression). The actual compression level used
will be the minimum of the client's and server's values. For these
purposes all bzip2 levels (except 0) are considered to be greater
than all zlib levels so if either client or server does not support
bzip2 the protocol degrades gracefully to using zlib. The default
compression value is ""zlib:6"".
Note that, because of the way that bzip2 compression works and the
buffer sizes that Zebedee uses, bzip will probably only be useful
if continuous streams of data are flowing. On smaller transfers,
such as those in a normal telnet session, zlib will usually win.
You will have to experiment to see what works best for you. In
addition, because the buffer size is small there is no gain from
using bzip2 levels above 1 and Zebedee will round any higher values
down to this level.
You can see exactly how much compression is gaining you at
verbosity levels 2 and above when basic statistics are printed out
on connection termination. For example:
zebedee(232/210): read 166 bytes (265 expanded) in 3 messages
zebedee(232/210): wrote 20969 bytes (30499 expanded) in 247 messages
generator
This is the "generator" for the Diffie-Hellman key exchange and is
a hexadecimal string. The default value is "2". I recommend that
you don't mess with this unless you know what you are doing.
keygencommand
If this keyword is specified its value is a command string that
will be executed in order to generate a private key (see
privatekey. The command should write a single line of hexadecimal
digits to stdout. This line must be a string of at least 10
hexadecimal digits. A simple Tcl (see <http://tcl.activestate.com>)
script ("passphrase.tcl") that prompts a user for a pass-phrase and
then uses this to generate an appropriate key is included in the
standard Zebedee distribution. If might be used as follows ("wish"
is the Tcl script interpreter):
keygencommand "/usr/bin/wish -f passphrase.tcl"
If a privatekey value is specified it takes precedence over any
keygencommand.
If the command string ends with a ""+"" character then the command
will be run with three extra command line arguments. The first is
IP address of the system to which the tunnel is connected (the
server address for a client, and client for a server). This is in
numeric form, not the DNS name. The next argument is the IP address
of the target for the tunnel (note that if this is the default
target it will be given as 0.0.0.0). The final argument is the
target port number. So, for a Zebedee client run like this:
zebedee-x "keygencommand 'newkey -x +'" 1000:192.168.100.100:23
the key generation command run would be as follows:
newkey -x 192.168.100.100 0.0.0.0 23
keygenlevel
This is an integer between 0 and 2 inclusive that determines how
strong the private key generation in Zebedee should be. The default
is 2 (the strongest) and you should generally not change this
unless connection set-up performance becomes unacceptable.
Briefly, on UNIX-like systems the level-2 key generation mechanism
uses "/dev/urandom" or "/dev/random", if either of these devices is
available, to obtain good pseudo-random data based on the state of
the running kernel. If no random-data device is available or the
level is set to 1 then data from the current contents of the
"/proc" file-system, if there is one, will be used otherwise at
level 0 only data from the current process will be used.
On Windows systems there is currently no distinction between
different key generation strength levels and this keyword is
effectively ignored.
keylength (command-line -k)
This is an integer specifying the maximum key length (in bits) for
the Blowfish encryption. It should be a multiple of 4 between 4 and
576. The key length used will be the minimum of the client's and
server's values (subject to any setting of minkeylength).
The default value is 128. As a special case setting this value to 0
will turn off key negotiation and encryption.
keylifetime
If the value of this parameter is non-zero it causes the client to
request the re-use of a previously established shared secret key
for deriving session keys for subsequent connections. This means
that on the first connection between a Zebedee client and server
the full key exchange dialogue will take place to establish a
shared secret key. On subsequent connections, until the key
expires, the same secret key will be reused to generate a new
session key. Once the key expires a new key exchange will
automatically be performed when necessary.
This keyword specifies how long a shared secret key is valid before
it must be renegotiated. This does not affect connections that have
already been established, only new connections.
The value is in seconds and must be less than or equal to 65535,
which is a little over 18 hours. By default it is set to 3600
seconds (one hour). Setting this value to zero effectively disables
the use of reusable keys and a full negotiation of a shared key
will be performed for each connection --- assuming that both client
and server also generate a new private key each time. This will
impact performance and is recommended only if you have a very high
paranoia level!
minchecksumlevel
If supplied, this specifies the minimum acceptable checksum level
(see checksumlevel) to be used by the client or server. If a client
requests a lower level of a server the server will reply with this
minimum. If a server replies with a lower level to a client then
the client will terminate the connection.
The default value is zero.
minkeylength
If supplied, this specifies the minimum acceptable key length (see
keylength) to be used by client or server. If a client requests a
lower level of a server the server will reply with this minimum. If
a server replies with a lower level to a client then the client
will terminate the connection.
The default value is zero.
modulus
The value of this key is a hexadecimal string specifying the
modulus value for the Diffie-Hellman key exchange. Don't alter this
unless you are both paranoid and know what you are doing.
The default modulus is the 1024-bit prime:
f488fd584e49dbcd 20b49de49107366b 336c380d451d0f7c 88b31c7c5b2d8ef6
f3c923c043f0a55b 188d8ebb558cb85d 38d334fd7c175743 a31d186cde33212c
b52aff3ce1b12940 18118d7c84a70a72 d686c40319c80729 7aca950cd9969fab
d00a509b0246d308 3d66a45d419f9c7c bd894b221926baab a25ec355e92f78c7
This was taken from the file testdh.h in Peter Gutman's CryptLib.
The comment in this code says that the value was among those
"generated by Colin Plumb for SKIP". It further says that "these
values were chosen as representative well-known public values to
allay fears of possible trapdoors in self-generated values. The
generation method and actual values can be checked against the SKIP
standards document."
privatekey
By default Zebedee will generate a new private key (the "exponent"
value in the Diffie-Hellman key exchange calculation) each time one
is required. If, however, you wish to use a fixed key then it can
be specified as a string of hexadecimal digits. You will
definitely need to do this if you wish to use the identity checking
feature. Note that the key must be at least 10 digits long.
sharedkey
By default Zebedee uses the Diffie-Hellman key exchange protocol to
establish an anonymous, shared secret key between client an server.
This means that neither party has to store any permanent secret
key. However, under some circumstances you may wish to use a pre-
established shared secret key, communicated by other means. The
sharedkey keyword allows you to do this. Its value is a string of
hexadecimal digits. This value is the unencrypted shared key and it
must contain at least as many bits (there are 4 bits per digit) as
will be used to encrypt the traffic through the tunnel. Note that
the shared key is not, however, used to encrypt the data directly.
A unique session key is still established for each tunnel.
All clients and servers that wish to communicate must use the same
shared secret key value. Connections between clients and servers
that do not share the same secret will be terminated before a
tunnel is established. It is your responsibility to distribute and
protect this secret from disclosure.
sharedkeygencommand
This is the equivalent to the keygencommand but in this case
generates a sharedkey value. Any sharedkey value overrides this, if
present.
Miscellaneous Keywords
The following keywords apply equally to clients and servers:
checkaddress
This keyword, which may be repeated multiple times, specifies an IP
address and, optionally, range of ports in the same form as that
used by the target keyword. The IP address can be in the form of a
CIDR address.
When a connection is established between a client and a server the
IP address and, optionally, source port of the system at the other
end of the connection is checked against the set of specified
addresses and ports. If it does not match any of the entries the
connection will be closed. So, for example, the entry:
checkaddress 192.168.1.0/24
checkaddress 192.168.2.0/24
in a server's configuration file would only permit connections from
systems on the two subnets named. This checking is done before any
further validation of identity (see identity checking).
Please note that source IP addresses can easily be "spoofed" and
you should not place great reliance on this for validating the
identity of a client or server. It is, however, a useful basic
protection mechanism.
checkidfile
This names a file that contains a set of identities that will be
checked before allowing a connection to be completed. This is
described further in the description of identity checking. You may
specify only one identity file. If this keyword appears multiple
times only the last value will be used.
If a keylength of zero has been agreed then no identity checking
will be performed.
acceptconnecttimeout
When Zebedee is used in "reverse-mode" (see listenmode and
clienthost) the timeout on waiting for connections to be accepted
is controlled by this keyword. Its value is in seconds and may be
no greater than 65535. The default is 300 seconds.
debug (command-line -D)
This is a boolean indicating that Zebedee should run in "debug"
mode. In this case a server (or client running in multiuse mode)
only accepts and handles a single connection at a time and does so
"inline" without creating another process or thread. This is useful
when running the program under the control of a debugger. It is
false by default. The command-line option -D is equivalent to
setting this to true.
Note that this setting will not work correctly in UDP mode, so
don't bother trying it!
detached (command-line -d)
This is a boolean indicating whether the process should detach
itself from the controlling terminal and run in the background (in
UNIX terms, to run as a "daemon"). This is valid for both client
and server and is true by default. The command-line option -d is
equivalent to setting this to false.
Note that this does not always seem to work from an interactive
command prompt under Windows systems. The symptom is that output to
the console window will stop and interrupt signals will be ignored
but the console prompt will not be issued until Zebedee terminates.
In order to work around this you can use the "start" command as in
the following example:
DOS> start zebedee-f server.zbd
This will start Zebedee in a new console session from which it will
then detach. You may see a console window appear briefly before it
detaches but Zebedee should be running in the background when it
disappears.
dumpdata
This is a boolean value indicating whether logging output should
include details of the data sent to and received from local
sockets. Because this data is potentially sensitive --- one of the
reasons for using Zebedee in the first place --- the default is for
such data not to be included (dumpdata is false). If it is set to
true then, when the verbosity level is 5 or greater, the logging
output will include lines such as the following:
read 39 bytes from local socket 324
< 0000 00 00 00 # ff S M B a2 4 00 00 c0 98 07 c8
< 0010 00 00 00 00 00 00 00 00 00 00 00 00 01 08 d0 03
< 0020 01 08 p 00 00 00 00
Lines beginning with ""<"" or "">"" show the data that is being is
read from or written to the local socket. Each line shows up to
sixteen bytes of data and is prefixed by the offset, in
hexadecimal, from the beginning of the data stream. Printable ASCII
characters are shown verbatim, such as the three characters ""SMB""
above, while other bytes are shown as a hexadecimal value.
httpproxy
Zebedee now has support for making the client-server TCP connection
via an HTTP proxy. If specified this should give the address and
port of the proxy server, for example:
httpproxy webproxy.example.com:8080
There is no default port, you must always specify one explicitly.
The proxy can be used for either client or server-initiated
connections (see listenmode). Source or target connections are
unaffected, the proxy only applies to connections between a Zebedee
client and server.
Please note that using an HTTP proxy server to tunnel arbitrary
connections is very likely to violate the security policy of the
organisation running the server. If you intend to use Zebedee in
this way (or, for that matter, to establish any other kind of
"backdoor" tunnel) I strongly advise you to seek permission from
the appropriate network administrators.
In order to give administrators some chance to maintain proper
control over the use of their proxy servers Zebedee does identify
itself with a user-agent string of "Zebedee" when it connects to
the proxy server. Well, it does in the "official" version anyway.
httpproxyauth
If tunnelling via an HTTP proxy, using httpproxy, some proxy
servers require authentication information to be supplied in order
to permit the connection to be made. Zebedee supports the "basic"
authentication type. The username and password required for this
can be specified using the httpproxyauth keyword. The username and
password are given in plain text, separated by a colon, as follows:
httpproxyauth "username:password"
idletimeout
This sets both the tcptimeout and udptimeout to the same value,
causing idle connections to be closed. Please see those keywords
for further details.
include (command-line -f)
This specifies the name of another configuration file to read and
parse at this point before continuing with the remainder of the
file. It might be used, for example, where a private key is stored
in a separate, more tightly protected file. There is a limit of 5
levels deep of include processing (counting the initial
configuration file as level 1). This avoids unintentional
recursion.
ipmode (command-line -U for "both" mode)
As of version 2.4, a Zebedee client or server can handle both TCP
and UDP traffic simultaneously. This is controlled by the ipmode
keyword. It can have a value of tcp, udp or both.
The default value is tcp and Zebedee will only handle TCP traffic
in this case. The value udp is equivalent to setting udpmode to be
true. In this case only UDP traffic will be handled and the Zebedee
server will, by default use a different port (11230). If it is set
to both then a client will listen for both TCP and UDP traffic and
a server will handle requests to tunnel both TCP and UDP traffic.
In this case the server uses only one port, by default the normal
TCP-mode port of 11965. The command-line option -U is equivalent to
""ipmode both"".
Please be aware that a client or server running purely in UDP mode
will expect to use port 11230 by default. If the corresponding
Zebedee server or client is running in "mixed" mode you may have to
specify the port explictly. For example, if the server is running
in mixed mode:
zebedee-s -U
then a client running in UDP-only mode will need to specify the
server port:
zebedee-u -T 11965 10000:serverhost:echo
listenip (command-line -b)
Specifies the local IP address used to listen for connections. This
can be useful on a system with multiple network interfaces, but
where Zebedee should only use one of them. If listenip is not
specified the default is to listen on all of the system's
interfaces.
The address can be given as a "dotted quad" or by name but in the
case where the name can resolve to multiple IP addresses the
results may be unpredictable. The address must, obviously, also
correspond to one of those belonging to the system.
Note that listenip is a more general form of localsource and
setting localsource will override listenip and vice versa.
lockprotocol (command-line -L)
In normal usage, different versions of Zebedee will try to
negotiate a compatible version of the Zebedee protocol between
themselves. Provided that no incompatible features are used, all
versions of Zebedee from 2.0 onwards can interwork with eachother.
The lockprotocol keyword is a boolean value that, if set true,
causes a client or server to reject requests for protocol versions
that do not match the default version being used by the program.
The default protocol version is always the highest that the program
supports so this has the effect of stopping the protocol being
"downgraded" to a previous version.
The main reason for using this is to ensure that features only
available in later versions of the protocol, such as checksumming
of data introduced in Zebedee version 2.5, can not be silently
dropped.
The default value is false.
maxbufsize
This specifies the size, in bytes, of the buffer Zebedee will use
to read data from applications. The actual size of buffer used will
be the minimum of the client's and server's values.
By default Zebedee attempts to read data from the client or server
programs at each end of the tunnel in chunks of 8192 bytes. There
may be occasions when you want to decrease this if, for example,
you have a highly interactive application and the response seems
sluggish because you end up waiting for large data transfers. You
can reduce the buffer size to one byte, but unless you are trying
to debug misbehaviour or have time to waste I don't recommend it!
Conversely, you may increase the buffer size up to a maximum of
16383 bytes to attempt to gain the most from data compression where
large blocks of data are being transferred. Note that the
maxbufsize value does not affect how much memory is allocated by
Zebedee, only the size of data chunks read.
When running in UDP mode this buffer size will also affect the
maximum size of any datagram that can be handled. Datagrams larger
than the current buffer size will be fragmented, which will likely
cause whatever application is consuming them to fail. Datagrams
larger than 16383 bytes can not be handled at all.
maxconnections
This specifies that maximum number of concurrent connections
(tunnels) that the Zebedee instance will handle.
The default value is zero, which means that no limit is applied.
=item message
The specifies a string that will be logged at verbosity level 1
when it is encountered in the configuration file.
name (command-line -n)
This is the name of the program that is to be used in messages
rather than the executable file name. Under Windows it is also the
name of any service to be installed or removed.
logfile (command-line -o)
This is the name of the file to which messages will be written. If
it is not specified then messages are written to stderr.
Two special "file names" are also recognised as valid values. If
the name is NULL the all messages will be turned off. If the name
is SYSLOG then messages will be written to the host system log. On
Windows systems this is the system application event log. Elsewhere
messages are written to the syslog service.
readtimeout
The readtimeout keyword is primarily intended to help provide a
Zebedee server with some additional defence against "denial of
service" attacks where a malicious user might make connections to a
server but not send any data to them. Each connection consumes
resources and it might be possible for an attacker to crash the
server by exceeding its resource capacity.
This value represents a time limit in seconds within which reads
from a Zebedee tunnel must be complete. If the value is zero then
no timeout is applied. This is the default behaviour because
applying a timeout will have some impact on performance and an
unnecessarily small timeout may cause valid connections to fail.
The timeout primarily affects the initial Zebedee protocol
exchanges. If you wish to cause valid but apparently idle
connections to be timed out you should use tcptimeout or
udptimeout.
This value may also be useful when a client is running in
listenmode. While Zebedee tries to determine whether a connection
from a server will be usable, and if it has already been closed,
this is not always possible. In this case setting this to a non-
zero value will stop the client hanging if it accepts such a "dead"
connection.
runasuser (command-line -N)
This keyword and option apply to UNIX/Linux systems only.
It may sometimes be necessary to run Zebedee as "root" (UID 0), for
example so that a server can listen on a so-called "privileged"
port below port 1024, or to access configuration or log files that
should not be readable by other users. However, having a program,
and particularly a network server, run as "root" for longer than
necessary is a potential security risk. If Zebedee is run as
"rootL" then this keyword can be used to specify a user identity to
which Zebedee should switch after it has opened all files and set
up listening sockets.
The user identity specified as an argument should be the name of a
valid account on the host machine. For example:
runasuser "nobody"
Zebedee will switch to the user-ID and primary group-ID associated
with that account. Note that it is considered a fatal error if the
account does not exist. This protects you against Zebedee failing
to switch away from "root" if you were expecting it do so. If
Zebedee is not running as "root" a warning will be issued and the
keyword ignored, but it will not cause a fatal error.
WARNING: Please note that it is not safe to make Zebedee a setuid
"root" program, even if this keyword is used. This keyword is only
intended for use where Zebedee is run by "root". Making Zebedee a
setuid "root" program will open a gaping security hole in your
system!
serverport (command-line -T)
This is the port on which the Zebedee server will listen for tunnel
connections. The default is 11965 (0x2EBD) when running in TCP mode
or mixed TCP and UDP mode. It is 11230 (0x2BDE) in UDP-only mode.
The keyword causes a server to listen on this port and a client to
attempt to connect to this port on the server system.
If using server-initiated connections (see listenmode and
clienthost) then this is also the port on which the client listens
for the server's incoming connections.
serverconnecttimeout
This sets maximum timeout for a client attempting to make a
connection to a server or (if running in "reverse" mode) for a
server to connect back to a client. Normally a connection attempt
will fail immediately if there is no remote Zebedee process
running. However, with certain kinds on network or system failures
connection attempts can block almost indefinitely. This timeout
prevents these hangs. The default is 300 seconds.
tcptimeout
By default, TCP-mode tunnels will stay open until either the
connection is closed by either source or target. This keyword
allows them to be closed after a certain period of inactivity. The
value is in seconds and must be no greater than 65535. Setting it
to zero results in an indefinite timeout.
See also idletimeout and udptimeout.
threadstacksize
This specifies the size of the stack allocated to each thread in
Zebedee, in units of 1 kilobyte. By default it is set to 64, and
Zebedee creates threads with a 64k stack. This should be more than
sufficient for its needs, and that of the C run time library. If
you suffer from inexplicable crashes you may wish to try raising
this. Conversely, on some platforms you may be able to lower it
without causing problems. Previous versions of Zebedee have run
successfully with a value of 32k. Under no circumstances can it be
lowered below 16 (kilobytes).
timestamplog (command-line -t)
This is a boolean value indicating whether log messages should
contain a time-stamp. The default is not to do so. The command-line
option -t is equivalent to setting this to true.
udpmode (command-line -u)
By default Zebedee handles connection-oriented TCP/IP traffic. If
this keyword is set true Zebedee handles UDP/IP connectionless
traffic instead.
The tunnel between Zebedee clients and servers still uses a TCP/IP
connection. A separate connection is established for each different
originating UDP network endpoint. Because UDP is connectionless
there is no easy way to tell when the data traffic has been
completed. For this reason the Zebedee connection must be timed out
after a period of inactivity. This period is controlled by the
udptimeout value.
If more data subsequently arrives from a source the tunnel for
which has been timed out, the connection must be re-established.
For this reason the performance in UDP mode may appear poor,
depending on the nature of the application using it. Altering the
keylifetime value may improve this by minimizing connection setup
times and changing the udptimeout value may also help.
The command-line -u option is equivalent to setting this to true.
It is also equivalent to setting ipmode to udp.
udptimeout
By default, UDP-mode tunnels will shut down after 300 seconds of
inactivty. They are recreated automatically if any further traffic
arrives. The timeout value can be changed by using this keyword to
specify the timeout in seconds. It must be no greater than 65535.
Setting it to zero results in an indefinite timeout. This is
probably not a good idea for UDP traffic as it means that there is
no way ever to indicate that those connections should be closed.
See also idletimeout and tcptimeout.
verbosity (command-line -v)
This is an integer specifying the level of message logging with 0
being just error messages and 5 giving excruciating detail of the
message traffic. The default (and generally most useful level) is
1.
Messages are written to stderr (unless redirected using the -o
command-line option or logfile keyword). The general form of
messages is something like:
zebedee(54/119): Listening on local port 1172
The numbers in brackets represent the process and thread
identifiers of the code logging the message. All error messages are
logged at level 0 and are preceded by the word "ERROR", as follows:
zebedee(54/119): ERROR: failed to connect to localhost:11965
Messages are indented according to the level at which they are
logged.
Obsolete Keywords
As Zebedee has evolved over time some of the keywords have been changed
to reflect this. In a few cases keywords have been superseded and made
obsolete. These obsolete keywords are still recognised in order to
retain backwards compatibility with old configuration files but they
should not be used in new ones.
clientport
This keyword has been superseded by the more general tunnel
keyword.
This is the port or list of ports on which the Zebedee client will
listen for connections. It is equivalent to the first part of a
tunnel specification.
connecttimeout
This has been replaced by the acceptconnecttimeout keyword.
localport
This was the name of the clientport keyword prior to version 2.0.0
of Zebedee.
redirecthost
This was the name of the targethost keyword prior to version 2.0.0
of Zebedee.
remoteport
This was the name of the targetport keyword prior to version 2.0.0
of Zebedee.
targethost
This keyword has been superseded by the more general target
keyword.
This keyword gives the name of a host to which a Zebedee server
will redirect all incoming tunnelled data, rather than to ports on
the local machine.
targetport
This keyword has been superseded by the more general tunnel
keyword.
It gives the port or list of ports to which the client will request
that Zebedee server should establish connections on the target
host. It is equivalent to the final part of a tunnel specification.
Other Options
There are a few command-line options that have no equivalent in the
configuration file. These are described below.
-F char
The first character of the argument to this option specifies an
additional field separator character, used in parsing configuration
file option lines. All instances of this character will be
replaced with a space before lines are parsed. It exists primarily
to be used in conjunction with the -x option where there may be
difficulties in constructing and invoking commands containing
spaces, owing to limitations in command interpreters. So, for
example, the command:
zebedee -F~ -x "message~'Hello,~World!'"
will output a message like the following:
zebedee(1128/1348): Hello, World!
Please be aware that you can specify any character as a separator.
It is your responsibility to ensure that the character you choose
does not conflict with any other usage in the configuration file.
-p This causes Zebedee to generate a private key value and to write it
to standard output in a form that can be used in a configuration
file (see privatekey). For example:
privatekey "c480bd48f707c69dec54c9e7b6e22dd04cac659e"
-P This causes Zebedee to generate a public "identity" suitable for
use by the identity checking feature. The result is written to
standard output. For example:
ef8153a0e392df005f67321ca2f0ace5bb8c5a1f myhostname
This option must either be specified with a configuration file that
contains a private key value or must be used in conjunction with -p
to generate private and public keys simultaneously.
-h This option causes the remaining command-line arguments to be
treated as the names of files. Each file is read in 8192 byte
chunks and the SHA hash is calculated. If no arguments are
specified or the argument is ""-"" then the standard input is read
and the hash of that is calculated. For example:
$ zebedee-h /etc/passwd
bb1e734aeffd2111417761f5938dea3b53759598 /etc/passwd
$ zebedee-h < /etc/passwd
bb1e734aeffd2111417761f5938dea3b53759598 -
-H This is similar to the -h option except that each argument is
treated as a literal string and the SHA hash of the string is
calculated and printed:
$ zebedee-H hello world
ac62a630ca850b4ea07eda664eaecf9480843152 hello
86bf25ecb8a40b40b885c097c683b6e236fc8085 world
-S (Windows only)
On Windows systems Zebedee can be installed and run as a "service"
--- an independently running process that is started automatically
at system boot time.
Zebedee can be installed as a service by specifying the install
parameter with the name of a configuration file, for example:
zebedee "-Sinstall=c:\zebedee\service.zbd"
You should always specify the full path to the configuration file.
This will be read at service start-up and must contain all the
parameters required for the service to run. Note that if the path
contains spaces you must enclose it in double quotes, as shown.
By default, the name of the installed service will be taken from
the name of the program file, and hence is usually zebedee, but you
can change this by using the -n option:
zebedee-n "Zebedee Client Service" "-Sinstall=c:\zebedee\clientsvc.zbd"
Once the service has been installed it will be automatically
started the next time that the system reboots. Alternatively you
can start it manually using the Service Control Panel (under
Windows NT).
To remove the service specify first stop it and then use the remove
parameter to the -S option, along with any necessary service name
using -n. For example:
zebedee-n "Zebedee Client Service" -Sremove
There is one further valid parameter to the -S option and this is
run. This is used internally by Zebedee to invoke the service
start-up code and should not be used directly.
-x This option can be used to set those configuration parameters that
do not have any other direct command-line equivalent. It takes a
string as an argument and this string is treated as if it were a
line read from a configuration files (including comments but
without "\" line continuation). So, for example:
zebedee-x " server true # It's a server!"
is a rather perverse way of achieving the same effect as:
zebedee-s
Quick-Reference Summary
The following table lists the recognised keywords, their argument
types, command-line equivalents, validity for client, server or both
and a brief description.
acceptconnecttimeout
seconds CS Timeout for connections to be accepted
checkidfile filename CS Checks peer identities against this file
checksumlevel level -K CS Sets data integrity checksum level (0 to 3)
clienthost hostname -c S Server initiates connection to client host
command string -e C Specified command to run connected to tunnel
compression level -z CS Requested maximum compression level
connectattempts
number -C S Number of attempts to connect to client
debug boolean CS Run in single-threaded "debug" mode
detached boolean -d CS Detach from the terminal/console
dropunknownprotocol
boolean CS Drop requests for incompatible protocol
generator string CS Hexadecimal Diffie-Hellman generator value
httpproxy host:port CS Make connections via the given HTTP proxy
httpproxyauth user:pass CS SUpply HTTP proxy authorisation details
idletimeout seconds CS Inactivity timeout for all tunnels
include filename -f CS Read in the named configuration file
ipmode type -U CS Run in TCP, UDP or "both" mode (-U = both)
keygencommand string CS Command to run to generate key
keygenlevel level CS Key generation strength level (0 to 2)
keylength bits CS Requested maximum keylength in bits
keylifetime seconds CS Lifetime of shared secret keys
listenip address -b CS Listens only on the specified IP address
listenmode boolean -l C Client listens for server connections
localsource boolean C Only accepts connections from local machine
lockprotocol boolean CS Allow only current default protocol
logfile filename -o CS Set the output log file
maxbufsize bytes CS Specify buffer size for data reads
maxconnections num CS Specify maximum number of active connections
message string CS Output the specified string
minchecksumlevel
level CS Acceptable minimum checksum level
minkeylength bits CS Acceptable minimum keylength in bits
modulus string CS Hexadecimal Diffie-Hellman modulus value
multiuse boolean -m C Handle multiple connections
name string CS Specify the name of the program
privatekey string CS Hexadecimal private key string
redirect ports -r S Ports to which server will redirect traffic
runasuser user -N CS Switch to if running as root (UNIX only)
server boolean -s CS Selects server-mode or client-mode
serverconnecttimeout
seconds CS Timeout for connection to server
serverhost hostname C Name of server host to which to connect
serverport port -T CS Set the port on which the server listens
sharedkey string CS Hexadecimal shared secret key string
sharedkeygencommand
string CS Command to run to generate shared key
target spec S Specifies allowed target host and ports
targetconnecttimeout
seconds S Timeout for connection to target
tcptimeout seconds CS Inactivity timeout for TCP tunnels
timestamplog boolean -t CS Add timestamps to the log file
tunnel spec C Specifies client ports and matching targets
udpmode boolean -u CS Handle UDP traffic only
udptimeout seconds CS Inactivity timeout for UDP tunnels
verbosity level -v CS Set the message logging level
Other options that have no keyword equivalents:
-F char
Specify an additional field separator (whitespace) character
-p Generate a private key
-P Generate a public "identity"
-h file ...
Hash file contents and print results
-H string ...
Hash string arguments and print results
-Sinstall=file
Install Windows service with specified configuration file
-Sremove
Remove Windows service
-x string
Parse option string
Identity Checking
By default Zebedee just establishes an encrypted channel between two
points. While you know that the data is protected from snooping "on the
wire" there is no guarantee that the tunnel ends up where you think it
does. By default, and unless you are applying any other kind of
filtering or firewalling, a Zebedee server will accept connections from
any client that can reach it. If the service to which you are
tunnelling does not provide any further authentication, or if it relies
on checking the source IP address, then it will be potentially open to
attack.
The simplest, but most basic check, that you can make is to restrict
the IP addresses from which a server will accept, or to which a client
will make, connections. You can do this by using the checkaddress
keyword.
IP address checking is useful but not that secure. Zebedee is also open
to open to "man-in-the-middle" attacks where an eavesdropper pretends
to a client to be the server and intercepts all traffic before
forwarding it on to the real server. If you are concerned primarily
with using data compression or protecting against casual "network
sniffing" then you may be happy with this situation. If, however, you
want more assurance that your connection is not being "hijacked" then
Zebedee provides some basic facilities for doing so.
A Zebedee server can validate the identity of the client at the other
end of a tunnel provided that you are using an encrypted connection. To
do so the client must use a fixed private key. The easiest way to
generate such a key is by using the -p option, like this:
zebedee-p
This will output a line something like this:
privatekey "410dea0cbd9c10da057848c43a610f6bb859b769"
The string of hexadecimal digits will be different every time you run
it. So, on your client system you should generate a key and save it in
a file, for example:
zebedee-p > myclient.key
The file "myclient.key" now contains the private key that will be used
by Zebedee on this system. The private key must be kept secret so you
should apply appropriate protection to this file to stop unauthorised
users accessing it. You now need to generate the public "fingerprint"
associated with this key, which you can do as follows:
zebedee-P -f myclient.key > myclient.id
The contents of the file "myclient.id" will look something like this:
135f04050961d37553731250d5c6f7495f088b32 myclient
The text after the string of hexadecimal digits will be the name of the
machine on which you run this. It's just a descriptive tag so you can
change it to be, for example:
135f04050961d37553731250d5c6f7495f088b32 Neil's PC
You should now modify your client configuration file to add a line:
include "path-to-dir/myclient.key"
where ""path-to-dir"" is the directory in which the key file is being
kept. The "myclient.id" file is used by any server that wishes to
validate the identity of "myclient". The contents are not secret and
you should copy this file to the Zebedee server.
On the server you should add the contents of "myclient.id" to a single
file containing the identity "fingerprints" of all clients you wish to
validate. This file, for example called "client.idlist", might look
like this:
ba077f6a42bea502f517cab5685e476a713d9621 Rebecca's PC
3ad38cb1f16957d5c535272ce27557bdaa4389c6 Ben's PC
135f04050961d37553731250d5c6f7495f088b32 Neil's PC
Now, to the server configuration file add the following line:
checkidfile "path-to-dir/client.idlist"
That's it! Now only clients whose identities appear in this file will
be able to create tunnels to the server. If you remove a line the
client will be denied further access.
At the moment you can only have a single identity file and it is an
"all or nothing" mechanism --- a client can either create a tunnel to
any valid target or to none at all. This may be enhanced in future.
It is also worth noting that this mechanism can equally well be used
for a client to validate the identity of a server, if the server uses a
fixed private key.
How does this work?
By default, Zebedee generates a new private key every time it is
started. If the same modulus, generator and private key are used they
will always generate the same public value for use in the Diffie-
Hellman key exchange protocol. The "fingerprint" is a hash of the
modulus, generator and public key. Only a person knowing the private
key will be able to produce public key and successfully decrypt
traffic. So, if the same combination of modulus, generator and key are
seen then the identity of the client can be tied to the owner of that
private key. The modulus, generator and key strings are hashed together
to produce the fingerprint merely for convenience and to keep the size
of the identity file small.
Notes on Other Security Issues
Message Integrity
Starting with version 2.5, Zebedee has the ability to perform data
integrity validation on the transmitted data stream. This is
controlled by the checksumlevel and minchecksumlevel keywords. This
integrity checking is on by default (although not set to the
highest level).
This integrity checking does give a greater assurance that data
packets have not been corrupted "in flight", but is does add a
little overhead in terms of both data traffic and CPU effort.
Replay and Insertion Attacks
One possible attack on many networked systems is that of capturing
data streams that have a known effect --- for example, a telnet
session during which an administrator was known to be performing
certain "dangerous" actions --- and then replaying it at some later
time. This does not require cracking the encrypted data stream
itself, merely knowing that the same network packets sent to a
server will elicit the same response.
When Zebedee is operating in "anonymous" mode the risk of such an
attack being successful is low because different private keys will
be generated every time Zebedee is used. However, if the identity
checking features are used the keys will be fixed and replay could
be a possibility. Zebedee protects against this by generating a
unique session key for each connection. Following that, the final
part of the connection setup also involves a challenge-response
exchange that verifies that the system at the other end of the
connection really knows the shared secret key and is not just
parrotting back previously recorded data.
In addition, Zebedee uses Blowfish encryption in "cipher feedback"
mode which means that decryption of any part of the data depends
upon successful decryption of all the data packets that have gone
before it. The challenge-response exchange "salts" the data-stream
so even if the protocol being tunnelled is determined a "known
plain-text" attack is made more difficult.
Key Generation
A poorly-chosen key can compromise even the strongest encryption
mechanism. When generating keys Zebedee attempts to gather as much
hard-to-guess state data as possible and then "stir" it using the
SHA hashing algorithm. On modern UNIX systems this generation
process should give pretty good keys.
On Windows the available state data is somewhat more predictable,
particularly if an attacker has access to the system. Having said
that, it should be quite acceptable for most purposes. The comments
in the code explain this in more detail if you are interested.
If you are unhappy with the key generation mechanisms then you
should call out to an external key generation program using the
keygencommand option in a configuration file. Suggestions for
improving the built-in capabilities will also be gratefully
received!
Default Server Configuration
By default, if you do not specify any target ports either in a
target specification or with a redirect keyword a Zebedee server
will accept requests to make connections to any port. This is
almost certainly not what you want in a production environment.
Denial of Service Attacks
A "denial of service" attack is one where a malicious user does not
attempt to capture secret information but instead tries to render a
service unavailable or unusable. In common with many network
service, Zebedee is somewhat vulnerable to such attacks. If this is
a particular concern to you then you may wish to employ the
readtimeout keyword in order to reduce the susceptibility to this
kind of attack.
TROUBLESHOOTING
Although Zebedee should work "out of the box" you might encounter some
problems. These are most likely during connection setup --- once that
has been accomplished the data transfer generally goes smoothly. The
eaisest way to see what is happening during the setup process is to use
the -v option. You will usually want to combine this with the -d and -D
options to stop Zebedee from the terminal and to force it to handle
only a single connection at a time. So, for example, you might use the
following command to start up a server:
zebedee-dD -v 3 -s
Setting the logging level to 3 should show you the main exchanges
during connection setup. If you believe there is a problem after this
then levels 4 and 5 will show you what message traffic is being
exchanged.
EXAMPLES
In the Zebedee distribution there are a number of example configuration
files. The following sections describe how they can be used as well as
how to use Zebedee to tunnel some specific protocols.
Example Server Configuration
There is an example server configuration file (server.zbd) shipped with
the Zebedee distribution. This shows most of the common options.
#
# Sample Zebedee server configuration file
#
# This shows the use of many, but not all, of the configuration file
# options available for use by a server.
#
verbosity 2 # Slightly more than basic messages
# Comment out the following line once you have read the comments
# in this file and enabled or disabled the appropriate options!
message "DEFAULT CONFIGURATION FILE -- EDIT BEFORE USE"
detached false # You will probably want this 'true' for normal
# use but I want to make sure that you see the
# preceding message if you haven't edited this.
server true # Yes, it's a server!
ipmode both # Operate in mixed TCP/UDP mode
compression zlib:9 # Allow maximum zlib compression
keylength 256 # Allow keys up to 256 bits
keylifetime 36000 # Shared keys last 10 hours
maxbufsize 16383 # Allow maximum possible buffer size
# Uncomment the following line to log messages to a local file.
#
# logfile './server.log'
#
# Or to log to the system logging facility uncomment this:
#
# logfile SYSLOG
keygenlevel 2 # Generate maximum strength private keys
# Uncomment the following line if you want to use a fixed private
# key stored in a static file. The file should contain a line of
# the form "privatekey hexadecimal-key-string". This file should
# be readable by the user running Zebedee but no-one else.
#
# include './server.key'
# To validate the identity of clients use a line something like
# the following:
#
# checkidfile './clients.id'
# The "redirect" expression can be use to set the default ports
# allowed when a target specification consists of a hostname but
# no other ports. The "redirect none" statement prohibits
# tunnelling anywhere by default.
redirect none
# Set up allowed targets. Note that there are NO targets allowed
# by this file by default. You must explicitly edit it to enable
# them.
# The following are good for testing purposes. Either TCP or UDP
# are allowed.
#
# target localhost:daytime,echo,chargen
# Basic interactive services, TCP only.
#
# target localhost:telnet/tcp,ftp/tcp
# VNC traffic -- usually you will only need a subset of this
# range, perhaps 5900 or 5901.
#
# target localhost:5900-5999/tcp
# X Window System -- again, usually you will only need
# a subset of this range.
#
# target localhost:6000-6010/tcp
# Here is an example of specifying targets using a subnet. In
# this case allowing tunnels to be established to VNC servers
# on the 10.1.1.xx subnet.
#
# target 10.1.1.0/24:5900/tcp
# The following line ensures that the default target host
# is the local machine. The last named host becomes the
# default so leaving this here ensures that "localhost" is,
# the default unless overridden on the command line.
target localhost
To test the identity checking facilities you can uncomment the
checkidfile line and then use one of the supplied client1.key or
client2.key files on the client side.
Use with VNC
One of the reasons behind writing Zebedee was to use it over dial-up
lines with VNC. VNC is a free system to provide remote display
capabilities using a "remote frame-buffer" concept. You can use it to
display Windows desktops remotely or, with an "Xvnc" server to access
an "X desktop" from any VNC client machine, or even a Java-enabled
browser! See http://www.uk.research.att.com/vnc/ for more details.
The supplied sample server configuration file server.zbd has sample
target statements (commented out by default) that are configured to
allow redirection of ports 5900-5999 which will allow tunnelling of VNC
sessions. This file can be used on both UNIX and Windows but note that
on Windows you must set the "AllowLoopback" flag in the registry in
order for tunnelling to work. Saving the following snippet (without any
leading spaces) in file a and then importing it into regedit will do
the trick:
REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\ORL\WinVNC3]
"AllowLoopback"=dword:00000001
[HKEY_LOCAL_MACHINE\SOFTWARE\ORL\WinVNC3\Default]
"AllowLoopback"=dword:00000001
You will find a file with these contents in the Zebedee distribution by
the name vncloopback.reg. Having set these registry entries then the
file vncviewer.zbd can be used to invoke a VNC viewer tunnelled to the
host named on the command line. Here are the contents of the file
vncviewer.zbd:
#
# Zebedee configuration file to start up a tunnelled VNC session
#
# Usage: zebedee-f vncviewer.zbd remote-host:vnc-port
#
verbosity 1 # Basic messages only
server false # It's a client
detached true # Detach from terminal
message "Starting VNC viewer"
# On Windows systems you might use the following:
command '"c:\Program Files\ORL\VNC\vncviewer.exe" localhost:%d'
# On UNIX systems you might use the following:
# command 'vncviewer localhost:%d'
compression 6 # Request normal Zlib compression
So using this file as follows:
zebedee-f vncviewer.zbd somehost:5901
will start a VNC viewer tunnelled to the VNC server on somehost port
5901 (the server you would usually refer to in VNC-parlance as
"somehost:1").
VNC also supports a Java viewer. If the server is running on port 59xx
then the viewer can be downloaded via port 58xx. However, it appears
that the Java viewer communicates the main VNC port number to the
client. So, to tunnel traffic when using the Java viewer you must make
sure that the local and remote ports use the same numbers. So, for
example, to tunnel traffic to a VNC server using port 5901 you should
do something like:
zebedee 5801,5901:remotehost:5801,5901
This will be problematic if you already have a VNC server running
locally on port 5901, but you can usually arrange local and remote VNC
servers so that there is no clash.
There is one last point worth mentioning. If you are using compression
with VNC it is worth experimenting a bit with the VNC protocol
encoding. I have found that "raw" encoding often compresses best and
sometimes gives better performance with Zebedee over slow links. But,
as they say, your mileage may vary!
Use with the X Window System
The X Window System uses ports in the range 6000 onwards.
Let's assume that your local machine called xlocal is running an X
server on port 6000. This would be the port normally used by the
display known as xlocal:0. You now want to send a secure xterm session
back to your local display from a machine called xremote. To do this
you might run the following command on xlocal:
zebedee-s localhost:6000
Then on xremote you could run:
zebedee 6001:xlocal:6000
This means that if the DISPLAY environment variable on xremote is set
to "localhost:1" then X traffic will end up on xlocal. So, for example,
to send a secured xterm session from xremote to xterm you would run a
command like this on xremote:
xterm -display localhost:1
Note that in order for this to work correctly you must also add an
entry for localhost to the access control list for the X server on
xlocal. You can do this by running the following command on xlocal:
xhost +localhost
Securing HTTP traffic
Zebedee can be used to secure or just compress all traffic to and from
a Web server. So, for example, if a Web server is running on the
machine webhost on port 80 and it is also running a Zebedee server then
the command:
zebedee 8000:webhost:80
will set up a tunnel via port 8000 on the client host. Now any URLs
that previously were addressed via webhost, for example:
http://webhost/private/index.html
can now be accessed securely as follows:
http://localhost:8000/private/index.html
You could redirect all HTTP traffic via the secure tunnel by setting
""localhost:8000"" as your proxy. Be careful, however, only to set this
as the proxy for HTTP connections --- other protocols (including Secure
HTTP) should be directed elsewhere. It is also possible to configure
most browsers to use different proxies for different domains and so
secure connections selectively. Consult your browser's documentation
for details on how to do this.
Securing FTP traffic
It is possible to protect the FTP control connection (over which the
username and password are sent) for many FTP servers using Zebedee "out
of the box" by following the instructions below. It may also be
possible to protect the control connection for other servers and even
"passive-mode" data connections by using Zebedee in conjunction with
one of the techniques described below.
The simplest approach, which will protect the control connection and
which works with some FTP servers, is to run the Zebedee server as
follows:
zebedee-s ftpserverhost:ftp
Note that even if you are running Zebedee on the same machine as the
FTP server you should explictly name it on the command line (or using
the target keyword). Do not refer to it as localhost. On the client
system you could then run Zebedee as follows to set up a tunnel via
port 10000:
zebedee 10000:ftpserverhost:ftp
To connect to the FTP server you would then use a command like:
ftp clienthost 10000
Again, use the local client host name not, localhost. If your FTP
client does not support specifying the port on the command line, as is
the case with the standard Windows FTP client program, you may be able
to use the command ""open clienthost 10000"" from within the program.
If you are not running an FTP server on the client machine you could
also try running Zebedee as:
zebedee ftp:ftpserverhost:ftp
and then just invoking the FTP client program as:
ftp clienthost
The approach just described will work for FTP servers that do not check
that the FTP control and data connections appear to come from the same
source. However, some servers such as the widely-used wu-ftpd are more
strict about this --- for good security reasons. If you can apparently
establish a connection to the server but directory listing and file
retrievals fail or hang then it is likely that your server is one of
the strict ones.
If you find yourself in this situation then a good approach (suggested
by Magnus Wedburg) is to investigate your FTP server's support for
operating with firewalls and Network Address Translation (NAT). Many
modern servers, including wu-ftpd, allow you to specify the address
that a server will report for itself in FTP requests. They will also
allow you to specify a range of ports which will be used for "passive
mode" connections. If you can specify these two values you should be
able to use Zebedee to tunnel both control traffic and also data
traffic for passive connections. Support for passive mode depends upon
the particular FTP client being used. Netscape Navigator and the
Windows program "WS_FTP" are examples of clients able to do this.
Assuming that you have the capability to specify the server response
address and range of ports you can the use Zebedee as follows. First,
set the response address to the "localhost" address, that is,
127.0.0.1. Then select a range of ports to be used for tunnelling
passive-mode data connections. The size of the range will limit the
number of simultaneous connections that can be handled. In this case we
will chose 30000-30010. Now, on the FTP server run:
zebedee-s localhost:ftp,30000-30010
Then on the client run:
zebedee 2121,30000-30010:ftpserverhost:ftp,30000-30010
The value of 2121, for the FTP control connection, could be any other
convenient port. The passive port range must, however, be the same as
that on the server. To access the server with both control and data
connections secured using Netscape you would then supply a URL of the
form:
ftp://username@clienthost:2121/
where username is your user-name on the FTP server host.
If you can't configure the target FTP server as described above then
there is one more method that you can try. The Zebedee distribution
contains an "FTP gateway" script called ftpgw.tcl. This is a program,
written using the freely-available Tcl scripting language (see
<http://tcl.activestate.com>) that intercepts FTP requests and re-
writes them so that a server is shielded from the presence of Zebedee.
You should run this on the same system as the Zebedee server. Assuming
that the FTP server is also running on the same system you can just run
this as:
tclsh ftpgw.tcl
This will start the gateway listening on port 2121. Obviously, in real
usage you will probably want to start this in the background. You then
start the Zebedee server as:
zebedee-s localhost:2121
Note that in this case you do specify the local host as the target. On
the client side you can now run:
zebedee 2121:ftpserverhost:2121
followed by:
ftp clienthost 2121
You must still, however, use the client host name here.
This configuration will allow you to tunnel the FTP control connection
but will not affect any data connections. Using ftpgw.tcl it is,
however, also possible to secure the passive-mode data channels in a
similar manner to that described above.
To secure passive-mode data connections you must choose a range of
ports on the server that will be used for data connections. In this
example we will again use 30000 to 30010. You then start ftpgw.tcl with
the -p option to specify this port range:
tclsh ftpgw.tcl -p 30000-30100
The Zebedee server would then be started as:
zebedee-s localhost:2121,30000-30100
and the client as
zebedee 2121,30000-30100:ftpserverhost:2121,30000-30100
To access the server with both control and data connections secured
using Netscape you would then supply a URL, identical to that shown
above, of the form:
ftp://username@clienthost:2121/
CHANGES
This section outlines the main user-visible changes since the previous
"stable" release, 2.4.1. Full details, including bug fixes and other
non-visible enhancements, are in the "CHANGES.txt" file in the Zebedee
distribution.
Backwards compatibility with Zebedee 1.x versions of the protocol
(which is now more than 3 years old) has been dropped. Compatibility is
maintained for releases 2.0.0 and upward.
New message integrity checking keywords (checksumlevel and
minchecksumlevel) have been added. These give assurance that messages
have not been tampered with in transit. Also the keywords
dropunknownprotocol and lockprotocol help enforce the use of these
features, if required. These are all derived from patches submitted by,
Henrick Lund. Great work Henrick!
Added the ability to hand the peer address, target address and target
port to key generation commands (add a ""+"" to the end of the command
to get three extra arguments provided). See keygencommand and
sharedkeygencommand for further details.
Added httpproxyauth" -- thanks to James CE Johnson.
Added runasuser|/item_runasuser> (and the -N option) -- thanks to
Thomas Melzer.
The target specification has been extended to allow per-target client
identity and address checking. The identity checking was originally
submitted by Alain Turbide and address checking by Henrik Lund (again!)
The acceptconnecttimeout connectattempts, serverconnecttimeout and
targetconnecttimeout keywords have been added to significantly improve
the "reverse-mode" operation.
Add maxconnections to alleviate potential denial of service attacks.
CREDITS AND LEGALITIES
The following information can also be found in the file LICENCE.txt in
the Zebedee distribution.
Copyright (c) 1999-2003 by Neil Winton. All Rights Reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
A copy of the GNU General Public License can be found in the file
GPL2.txt.
You may obtain the latest copy of Zebedee, including full source code
from http://www.winton.org.uk/zebedee/ and other enquiries about
Zebedee can be e-mailed to the author at zebedee@winton.org.uk
Zebedee would not have been possible without the use of a large amount
of freely-available software to do all the really hard stuff. I
gratefully acknowledge the contributions made by the authors of the
following software packages.
Zebedee uses the "Blowfish" encryption algorithm devised by Bruce
Schneier. For more information on Blowfish see
http://www.counterpane.com/blowfish.html . The implementation used is
by Eric Young and is covered by the following copyright:
Copyright (C) 1995-1997 Eric Young (eay@mincom.oz.au)
All rights reserved.
This package is an Blowfish implementation written
by Eric Young (eay@mincom.oz.au).
This library is free for commercial and non-commercial use as long as
the following conditions are aheared to. The following conditions
apply to all code found in this distribution.
Copyright remains Eric Young's, and as such any Copyright notices in
the code are not to be removed.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by Eric Young (eay@mincom.oz.au)
THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
The license and distribution terms for any publically available version or
derivative of this code cannot be changed. i.e. this code cannot simply be
copied and put under another distrubution license
[including the GNU Public License.]
The reason behind this being stated in this direct manner is past
experience in code simply being copied and the attribution removed
from it and then being distributed as part of other packages. This
implementation was a non-trivial and unpaid effort.
Zebedee uses the zlib compression library by Jean-loup Gailly and Mark
Adler. It is covered by the following copyright notice:
(C) 1995-1998 Jean-loup Gailly and Mark Adler
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
Jean-loup Gailly Mark Adler
jloup@gzip.org madler@alumni.caltech.edu
Zebedee may use the bzip2 compression library by Julian Seward which is
covered by the following licence:
This program, "bzip2" and associated library "libbzip2", are
copyright (C) 1996-1999 Julian R Seward. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. The origin of this software must not be misrepresented; you must
not claim that you wrote the original software. If you use this
software in a product, an acknowledgment in the product
documentation would be appreciated but is not required.
3. Altered source versions must be plainly marked as such, and must
not be misrepresented as being the original software.
4. The name of the author may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Julian Seward, Cambridge, UK.
jseward@acm.org
bzip2/libbzip2 version 0.9.5 of 24 May 1999
By default Zebedee is built using an aribtrary precision integer
arithmetic library derived from the sources to "mirrordir-0.10.49"
which in turn derived this from the Python sources. The copyright is as
follows:
huge-number.c: arbitrary precision integer library from Python sources
This has nothing to do with cryptography.
Copyright (C) 1998 Paul Sheer
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
This file was taken from the Python source for `long' type
integers. I have changed it to compile independently of the
Python source, and added the optimisation that GNU C can
use 31 bit digits instead of Python's 15 bit. You can download
the original from www.python.org. This file bears little
resemblance to the original though - paul
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.
While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.
STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
Zebedee uses the Secure Hash Algorith (SHA) the code for which was
derived from Uwe Hollerbach's SHA module for perl. The code contains
the following statement:
NIST Secure Hash Algorithm
heavily modified by Uwe Hollerbach <uh@alumni.caltech edu>
from Peter C. Gutmann's implementation as found in
Applied Cryptography by Bruce Schneier
This code is in the public domain
Under Windows, Zebedee uses an implementation of the getopt function
covered by the following copyright:
Copyright (c) 1987, 1993, 1994
The Regents of the University of California. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the University of
California, Berkeley and its contributors.
4. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
Thanks
Special thanks go to those people who have taken the trouble to give me
feedback and suggestions for improvement!
$Id: zebedee.pod,v 1.31 2005/09/02 22:10:41 ndwinton Exp $
Zebedee 2.5.3 2015-08-31 ZEBEDEE(1)
