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@ -2,7 +2,7 @@
.TH X11VNC "1" "July 2006" "x11vnc " "User Commands"
.SH NAME
x11vnc - allow VNC connections to real X11 displays
version: 0.8.2, lastmod: 2006-07-11
version: 0.8.2, lastmod: 2006-07-12
.SH SYNOPSIS
.B x11vnc
[OPTION]...
@ -388,10 +388,6 @@ to the program location and in standard locations
(/usr/local/share/x11vnc/classes, etc). Under \fB-ssl\fR or
\fB-stunnel\fR the ssl classes subdirectory is sought.
.PP
\fB-http_ssl\fR
.IP
As \fB-http,\fR but force lookup for ssl classes subdir.
.PP
\fB-connect\fR \fIstring\fR
.IP
For use with "vncviewer -listen" reverse connections.
@ -555,160 +551,6 @@ used to have viewonly passwords. (tip: make the 3rd
and last line be "__BEGIN_VIEWONLY__" to have 2
full-access passwords)
.PP
\fB-unixpw\fR \fI[list]\fR
.IP
Use Unix username and password authentication. x11vnc
uses the
.IR su (1)
program to verify the user's password.
[list] is an optional comma separated list of allowed
Unix usernames. See below for per-user options that
can be applied.
.IP
A familiar "login:" and "Password:" dialog is
presented to the user on a black screen inside the
vncviewer. The connection is dropped if the user fails
to supply the correct password in 3 tries or does not
send one before a 25 second timeout. Existing clients
are view-only during this period.
.IP
Since the detailed behavior of
.IR su (1)
can vary from
OS to OS and for local configurations, test the mode
carefully on your systems before using it in production.
Test different combinations of valid/invalid usernames
and valid/invalid passwords to see if it behaves as
expected. x11vnc will attempt to be conservative and
reject a login if anything abnormal occurs.
.IP
On FreeBSD and the other BSD's by default it is
impossible for the user running x11vnc to validate
his *own* password via
.IR su (1)
(evidently commenting out
the pam_self.so entry in /etc/pam.d/su eliminates this
problem). So the x11vnc login will always *fail* for
this case (even when the correct password is supplied).
.IP
A possible workaround for this would be to start
x11vnc as root with the "\fB-users\fR \fI+nobody\fR" option to
immediately switch to user nobody. Another source of
problems are PAM modules that prompt for extra info,
e.g. password aging modules. These logins will fail
as well even when the correct password is supplied.
.IP
**IMPORTANT**: to prevent the Unix password being sent
in *clear text* over the network, one of two schemes
will be enforced: 1) the \fB-ssl\fR builtin SSL mode, or 2)
require both \fB-localhost\fR and \fB-stunnel\fR be enabled.
.IP
Method 1) ensures the traffic is encrypted between
viewer and server. A PEM file will be required, see the
discussion under \fB-ssl\fR below (under some circumstances
a temporary one can be automatically generated).
.IP
Method 2) requires the viewer connection to appear
to come from the same machine x11vnc is running on
(e.g. from a ssh \fB-L\fR port redirection). And that the
\fB-stunnel\fR SSL mode be used for encryption over the
network.(see the description of \fB-stunnel\fR below).
.IP
Note: as a convenience, if you
.IR ssh (1)
in and start
x11vnc it will check if the environment variable
SSH_CONNECTION is set and appears reasonable. If it
does, then the \fB-ssl\fR or \fB-stunnel\fR requirement will be
dropped since it is assumed you are using ssh for the
encrypted tunnelling. \fB-localhost\fR is still enforced.
Use \fB-ssl\fR or \fB-stunnel\fR to force SSL usage even if
SSH_CONNECTION is set.
.IP
To override the above restrictions you can set
environment variables before starting x11vnc:
.IP
Set UNIXPW_DISABLE_SSL=1 to disable requiring either
\fB-ssl\fR or \fB-stunnel.\fR Evidently you will be using a
different method to encrypt the data between the
vncviewer and x11vnc: perhaps
.IR ssh (1)
or an IPSEC VPN.
.IP
Note that use of \fB-localhost\fR with
.IR ssh (1)
is roughly
the same as requiring a Unix user login (since a Unix
password or the user's public key authentication is
used by sshd on the machine where x11vnc runs and only
local connections from that machine are accepted)
.IP
Set UNIXPW_DISABLE_LOCALHOST=1 to disable the \fB-localhost\fR
requirement in Method 2). One should never do this
(i.e. allow the Unix passwords to be sniffed on the
network).
.IP
Regarding reverse connections (e.g. \fB-R\fR connect:host
and \fB-connect\fR host), when the \fB-localhost\fR constraint is
in effect then reverse connections can only be used
to connect to the same machine x11vnc is running on
(default port 5500). Please use a ssh or stunnel port
redirection to the viewer machine to tunnel the reverse
connection over an encrypted channel. Note that in \fB-ssl\fR
mode reverse connection are disabled (see below).
.IP
In \fB-inetd\fR mode the Method 1) will be enforced (not
Method 2). With \fB-ssl\fR in effect reverse connections
are disabled. If you override this via env. var, be
sure to also use encryption from the viewer to inetd.
Tip: you can also have your own stunnel spawn x11vnc
in \fB-inetd\fR mode (thereby bypassing inetd). See the FAQ
for details.
.IP
The user names in the comma separated [list] can have
per-user options after a ":", e.g. "fred:opts"
where "opts" is a "+" separated list of
"viewonly", "fullaccess", "input=XXXX", or
"deny", e.g. "karl,wally:viewonly,boss:input=M".
For "input=" it is the K,M,B,C described under \fB-input.\fR
.IP
If a user in the list is "*" that means those
options apply to all users. It also means all users
are allowed to log in after supplying a valid password.
Use "deny" to explicitly deny some users if you use
"*" to set a global option.
.IP
There are also some utilities for testing password
if [list] starts with the "%" character. See the
quick_pw() function in the source for details.
.PP
\fB-unixpw_nis\fR \fI[list]\fR
.IP
As \fB-unixpw\fR above, however do not use
.IR su (1)
but rather
use the traditional
.IR getpwnam (3)
+
.IR crypt (3)
method to
verify passwords instead. This requires that the
encrypted passwords be readable. Passwords stored
in /etc/shadow will be inaccessible unless x11vnc
is run as root.
.IP
This is called "NIS" mode simply because in most
NIS setups the user encrypted passwords are accessible
(e.g. "ypcat passwd"). NIS is not required for this
mode to work (only that
.IR getpwnam (3)
return the encrypted
password is required), but it is unlikely it will work
for any other modern environment unless x11vnc is run
as root (which, btw, is often done when running x11vnc
from inetd and xdm/gdm/kdm). All of the \fB-unixpw\fR options
and contraints apply.
.PP
\fB-display\fR \fIWAIT:...\fR
.IP
A special usage mode for the normal \fB-display\fR option.
@ -736,47 +578,6 @@ output is taken as XAUTHORITY data. It can be either
of the form XAUTHORITY=<file> or raw xauthority data for
the display (e.g. "xauth extract - $DISPLAY" output).
.IP
In the case of \fB-unixpw\fR (but not \fB-unixpw_nis),\fR then the
above command is run as the user who just authenticated
via the login and password prompt.
.IP
Also in the case of \fB-unixpw,\fR the user logging in can
place a colon at the end of his username and supply
a few options: scale=, scale_cursor= (or sc=), solid,
id=, clear_mods (or cm), clear_keys (or ck), repeat, or
speeds= separated by commas if there is more than one.
After the user logs in successfully, these options will
be applied to the VNC screen. For example,
.IP
login: fred:scale=3/4,repeat
Password: ...
.IP
for convenience m/n implies scale= e.g. fred:3/4
To disable this set the environment variable
X11VNC_NO_UNIXPW_OPTS=1. To set any other options,
the user can use the gui (x11vnc \fB-gui\fR connect) or the
remote control method (x11vnc \fB-R\fR opt:val) during his
VNC session.
.IP
So the combination of \fB-display\fR WAIT:cmd=... and
\fB-unixpw\fR allows automatic pairing of an unix
authenticated VNC user with his desktop. This could
be very useful on SunRays and also any system where
multiple users share a given machine. The user does
not need to remember special ports or passwords set up
for his desktop and VNC.
.IP
A nice way to use WAIT:cmd=... is out of
.IR inetd (8)
(it automatically forks a new x11vnc for each user).
You can have the x11vnc inetd spawned process run as,
say, root or nobody. When run as root (for either inetd
or display manager), you can also supply the option
"\fB-users\fR \fIunixpw=\fR" to have the x11vnc process switch to
the user as well. Note: there will be a 2nd SSL helper
process that will not switch, but it is only encoding
and decoding the encrypted stream at that point.
.IP
As a special case, WAIT:cmd=FINDDISPLAY will run a
script that works on most Unixes to determine a user's
DISPLAY variable and xauthority data (see
@ -801,544 +602,6 @@ e.g. WAIT:1280x1024:... to set the size of the display
the VNC client first attaches to since some VNC viewers
will not automatically adjust to a new framebuffer size.
.PP
\fB-ssl\fR \fI[pem]\fR
.IP
Use the openssl library (www.openssl.org) to provide a
built-in encrypted SSL tunnel between VNC viewers and
x11vnc. This requires libssl support to be compiled
into x11vnc at build time. If x11vnc is not built
with libssl support it will exit immediately when \fB-ssl\fR
is prescribed.
.IP
[pem] is optional, use "\fB-ssl\fR \fI/path/to/mycert.pem\fR"
to specify a PEM certificate file to use to identify
and provide a key for this server. See
.IR openssl (1)
for
more info about PEMs and the \fB-sslGenCert\fR option below.
.IP
The connecting VNC viewer SSL tunnel can optionally
authenticate this server if they have the public
key part of the certificate (or a common certificate
authority, CA, is a more sophisicated way to verify
this server's cert, see \fB-sslGenCA\fR below). This is
used to prevent man-in-the-middle attacks. Otherwise,
if the VNC viewer accepts this server's key without
verification, at least the traffic is protected
from passive sniffing on the network (but NOT from
man-in-the-middle attacks).
.IP
If [pem] is not supplied and the
.IR openssl (1)
utility
command exists in PATH, then a temporary, self-signed
certificate will be generated for this session (this
may take 5-30 seconds on slow machines). If
.IR openssl (1)
cannot be used to generate a temporary certificate
x11vnc exits immediately.
.IP
If successful in using
.IR openssl (1)
to generate a
temporary certificate, the public part of it will be
displayed to stderr (e.g. one could copy it to the
client-side to provide authentication of the server to
VNC viewers.) See following paragraphs for how to save
keys to reuse when x11vnc is restarted.
.IP
Set the env. var. X11VNC_SHOW_TMP_PEM=1 to have x11vnc
print out the entire certificate, including the PRIVATE
KEY part, to stderr. One could reuse this cert if saved
in a [pem] file. Similarly, set X11VNC_KEEP_TMP_PEM=1
to not delete the temporary PEM file: the file name
will be printed to stderr (so one could move it to
a safe place for reuse). You will be prompted for a
passphrase for the private key.
.IP
If [pem] is "SAVE" then the certificate will be saved
to the file ~/.vnc/certs/server.pem, or if that file
exists it will be used directly. Similarly, if [pem]
is "SAVE_PROMPT" the server.pem certificate will be
made based on your answers to its prompts for info such
as OrganizationalName, CommonName, etc.
.IP
Use "SAVE-<string>" and "SAVE_PROMPT-<string>"
to refer to the file ~/.vnc/certs/server-<string>.pem
instead. E.g. "SAVE-charlie" will store to the file
~/.vnc/certs/server-charlie.pem
.IP
See \fB-ssldir\fR below to use a directory besides the
default ~/.vnc/certs
.IP
Example: x11vnc \fB-ssl\fR SAVE \fB-display\fR :0 ...
.IP
Reverse connections are disabled in \fB-ssl\fR mode because
there is no way to ensure that data channel will
be encrypted. Set X11VNC_SSL_ALLOW_REVERSE=1 to
override this.
.IP
Your VNC viewer will also need to be able to connect
via SSL. See the discussion below under \fB-stunnel\fR and
the FAQ (ssl_vncviewer script) for how this might be
achieved. E.g. on Unix it is easy to write a shell
script that starts up stunnel and then vncviewer.
Also in the x11vnc source a SSL enabled Java VNC Viewer
applet is provided in the classes/ssl directory.
.PP
\fB-ssldir\fR \fI[dir]\fR
.IP
Use [dir] as an alternate ssl certificate and key
management toplevel directory. The default is
~/.vnc/certs
.IP
This directory is used to store server and other
certificates and keys and also other materials. E.g. in
the simplest case, "\fB-ssl\fR \fISAVE\fR" will store the x11vnc
server cert in [dir]/server.pem
.IP
Use of alternate directories via \fB-ssldir\fR allows you to
manage multiple VNC Certificate Authority (CA) keys.
Another use is if ~/.vnc/cert is on an NFS share you
might want your certificates and keys to be on a local
filesystem to prevent network snooping (for example
\fB-ssldir\fR /var/lib/x11vnc-certs).
.IP
\fB-ssldir\fR affects nearly all of the other \fB-ssl*\fR options,
e.g. \fB-ssl\fR SAVE, \fB-sslGenCert,\fR etc..
.PP
\fB-sslverify\fR \fI[path]\fR
.IP
For either of the \fB-ssl\fR or \fB-stunnel\fR modes, use [path]
to provide certificates to authenticate incoming VNC
*Client* connections (normally only the server is
authenticated in SSL.) This can be used as a method
to replace standard password authentication of clients.
.IP
If [path] is a directory it contains the client (or CA)
certificates in separate files. If [path] is a file,
it contains multiple certificates. See special tokens
below. These correspond to the "CApath = dir" and
"CAfile = file" stunnel options. See the
.IR stunnel (8)
manpage for details.
.IP
Examples:
x11vnc \fB-ssl\fR \fB-sslverify\fR ~/my.pem
x11vnc \fB-ssl\fR \fB-sslverify\fR ~/my_pem_dir/
.IP
Note that if [path] is a directory, it must contain
the certs in separate files named like <HASH>.0, where
the value of <HASH> is found by running the command
"openssl x509 \fB-hash\fR \fB-noout\fR \fB-in\fR file.crt". Evidently
one uses <HASH>.1 if there is a collision...
.IP
The the key-management utility "\fB-sslCertInfo\fR \fIHASHON\fR"
and "\fB-sslCertInfo\fR \fIHASHOFF\fR" will create/delete these
hashes for you automatically (via symlink) in the HASH
subdirs it manages. Then you can point \fB-sslverify\fR to
the HASH subdir.
.IP
Special tokens: in \fB-ssl\fR mode, if [path] is not a file or
a directory, it is taken as a comma separated list of
tokens that are interpreted as follows:
.IP
If a token is "CA" that means load the CA/cacert.pem
file from the ssl directory. If a token is "clients"
then all the files clients/*.crt in the ssl directory
are loaded. Otherwise the file clients/token.crt
is attempted to be loaded. As a kludge, use a token
like ../server-foo to load a server cert if you find
that necessary.
.IP
Use \fB-ssldir\fR to use a directory different from the
~/.vnc/certs default.
.IP
Note that if the "CA" cert is loaded you do not need
to load any of the certs that have been signed by it.
You will need to load any additional self-signed certs
however.
.IP
Examples:
x11vnc \fB-ssl\fR \fB-sslverify\fR CA
x11vnc \fB-ssl\fR \fB-sslverify\fR self:fred,self:jim
x11vnc \fB-ssl\fR \fB-sslverify\fR CA,clients
.IP
Usually "\fB-sslverify\fR \fICA\fR" is the most effective.
See the \fB-sslGenCA\fR and \fB-sslGenCert\fR options below for
how to set up and manage the CA framework.
.IP
NOTE: the following utilities, \fB-sslGenCA,\fR \fB-sslGenCert,\fR
\fB-sslEncKey,\fR and \fB-sslCertInfo\fR are provided for
completeness, but for casual usage they are overkill.
.IP
They provide VNC Certificate Authority (CA) key creation
and server / client key generation and signing. So they
provide a basic Public Key management framework for
VNC-ing with x11vnc. (note that they require
.IR openssl (1)
be installed on the system)
.IP
However, the simplest usage mode (where x11vnc
automatically generates its own, self-signed, temporary
key and the VNC viewers always accept it, e.g. accepting
via a dialog box) is probably safe enough for most
scenarios. CA management is not needed.
.IP
To protect against Man-In-The-Middle attacks the
simplest mode can be improved by using "\fB-ssl\fR \fISAVE\fR"
to have x11vnc create a longer term self-signed
certificate, and then (safely) copy the corresponding
public key cert to the desired client machines (care
must be taken the private key part is not stolen;
you will be prompted for a passphrase).
.IP
So keep in mind no CA key creation or management
(-sslGenCA and \fB-sslGenCert)\fR is needed for either of
the above two common usage modes.
.IP
One might want to use \fB-sslGenCA\fR and \fB-sslGenCert\fR
if you had a large number of VNC client and server
workstations. That way the administrator could generate
a single CA key with \fB-sslGenCA\fR and distribute its
certificate part to all of the workstations.
.IP
Next, he could create signed VNC server keys
(-sslGenCert server ...) for each workstation or user
that then x11vnc would use to authenticate itself to
any VNC client that has the CA cert.
.IP
Optionally, the admin could also make it so the
VNC clients themselves are authenticated to x11vnc
(-sslGenCert client ...) For this \fB-sslverify\fR would be
pointed to the CA cert (and/or self-signed certs).
.IP
x11vnc will be able to use all of these cert and
key files. On the VNC client side, they will need to
be "imported" somehow. Web browsers have "Manage
Certificates" actions as does the Java applet plugin
Control Panel. stunnel can also use these files (see
the ssl_vncviewer example script in the FAQ.)
.PP
\fB-sslGenCA\fR \fI[dir]\fR
.IP
Generate your own Certificate Authority private key,
certificate, and other files in directory [dir].
.IP
If [dir] is not supplied, a \fB-ssldir\fR setting is used,
or otherwise ~/.vnc/certs is used.
.IP
This command also creates directories where server and
client certs and keys will be stored. The
.IR openssl (1)
program must be installed on the system and available
in PATH.
.IP
After the CA files and directories are created the
command exits; the VNC server is not run.
.IP
You will be prompted for information to put into the CA
certificate. The info does not have to be accurate just
as long as clients accept the cert for VNC connections.
You will also need to supply a passphrase of at least
4 characters for the CA private key.
.IP
Once you have generated the CA you can distribute
its certificate part, [dir]/CA/cacert.pem, to other
workstations where VNC viewers will be run. One will
need to "import" this certicate in the applications,
e.g. Web browser, Java applet plugin, stunnel, etc.
Next, you can create and sign keys using the CA with
the \fB-sslGenCert\fR option below.
.IP
Examples:
x11vnc \fB-sslGenCA\fR
x11vnc \fB-sslGenCA\fR ~/myCAdir
x11vnc \fB-ssldir\fR ~/myCAdir \fB-sslGenCA\fR
.IP
(the last two lines are equivalent)
.PP
\fB-sslGenCert\fR \fItype\fR \fIname\fR
.IP
Generate a VNC server or client certificate and private
key pair signed by the CA created previously with
\fB-sslGenCA.\fR The
.IR openssl (1)
program must be installed
on the system and available in PATH.
.IP
After the Certificate is generated the command exits;
the VNC server is not run.
.IP
The type of key to be generated is the string \fItype\fR.
It is either "server" (i.e. for use by x11vnc) or
"client" (for a VNC viewer). Note that typically
only "server" is used: the VNC clients authenticate
themselves by a non-public-key method (e.g. VNC or
unix password). \fItype\fR is required.
.IP
An arbitrary default name you want to associate with
the key is supplied by the \fIname\fR string. You can
change it at the various prompts when creating the key.
\fIname\fR is optional.
.IP
If name is left blank for clients keys then "nobody"
is used. If left blank for server keys, then the
primary server key: "server.pem" is created (this
is the saved one referenced by "\fB-ssl\fR \fISAVE\fR" when the
server is started)
.IP
If \fIname\fR begins with the string "self:" then
a self-signed certificate is created instead of one
signed by your CA key.
.IP
If \fIname\fR begins with the string "req:" then only a
key (.key) and a certificate signing *request* (.req)
are generated. You can then send the .req file to
an external CA (even a professional one, e.g. Thawte)
and then combine the .key and the received cert into
the .pem file with the same basename.
.IP
The distinction between "server" and "client" is
simply the choice of output filenames and sub-directory.
This makes it so the \fB-ssl\fR SAVE-name option can easily
pick up the x11vnc PEM file this option generates.
And similarly makes it easy for the \fB-sslverify\fR option
to pick up your client certs.
.IP
There is nothing special about the filename or directory
location of either the "server" and "client" certs.
You can rename the files or move them to wherever
you like.
.IP
Precede this option with \fB-ssldir\fR [dir] to use a
directory other than the default ~/.vnc/certs You will
need to run \fB-sslGenCA\fR on that directory first before
doing any \fB-sslGenCert\fR key creation.
.IP
Note you cannot recreate a cert with exactly the same
distiguished name (DN) as an existing one. To do so,
you will need to edit the [dir]/CA/index.txt file to
delete the line.
.IP
Similar to \fB-sslGenCA,\fR you will be prompted to fill
in some information that will be recorded in the
certificate when it is created. Tip: if you know
the fully-quailified hostname other people will be
connecting to you can use that as the CommonName "CN"
to avoid some applications (e.g. web browsers and java
plugin) complaining it does not match the hostname.
.IP
You will also need to supply the CA private key
passphrase to unlock the private key created from
\fB-sslGenCA.\fR This private key is used to sign the server
or client certicate.
.IP
The "server" certs can be used by x11vnc directly by
pointing to them via the \fB-ssl\fR [pem] option. The default
file will be ~/.vnc/certs/server.pem. This one would
be used by simply typing \fB-ssl\fR SAVE. The pem file
contains both the certificate and the private key.
server.crt file contains the cert only.
.IP
The "client" cert + private key file will need
to be copied and imported into the VNC viewer
side applications (Web browser, Java plugin,
stunnel, etc.) Once that is done you can delete the
"client" private key file on this machine since
it is only needed on the VNC viewer side. The,
e.g. ~/.vnc/certs/clients/<name>.pem contains both
the cert and private key. The <name>.crt contains the
certificate only.
.IP
NOTE: It is very important to know one should always
generate new keys with a passphrase. Otherwise if an
untrusted user steals the key file he could use it to
masquerade as the x11vnc server (or VNC viewer client).
You will be prompted whether to encrypt the key with
a passphrase or not. It is recommended that you do.
One inconvenience to a passphrase is that it must
be suppled every time x11vnc or the client app is
started up.
.IP
Examples:
.IP
x11vnc \fB-sslGenCert\fR server
x11vnc \fB-ssl\fR SAVE \fB-display\fR :0 ...
.IP
and then on viewer using ssl_vncviewer stunnel wrapper
(see the FAQ):
ssl_vncviewer \fB-verify\fR ./cacert.crt hostname:0
.IP
(this assumes the cacert.crt cert from \fB-sslGenCA\fR
was safely copied to the VNC viewer machine where
ssl_vncviewer is run)
.IP
Example using a name:
.IP
x11vnc \fB-sslGenCert\fR server charlie
x11vnc \fB-ssl\fR SAVE-charlie \fB-display\fR :0 ...
.IP
Example for a client certificate (rarely used):
.IP
x11vnc \fB-sslGenCert\fR client roger
scp ~/.vnc/certs/clients/roger.pem somehost:.
rm ~/.vnc/certs/clients/roger.pem
.IP
x11vnc is then started with the the option \fB-sslverify\fR
~/.vnc/certs/clients/roger.crt (or simply \fB-sslverify\fR
roger), and on the viewer user on somehost could do
for example:
.IP
ssl_vncviewer \fB-mycert\fR ./roger.pem hostname:0
.PP
\fB-sslEncKey\fR \fI[pem]\fR
.IP
Utility to encrypt an existing PEM file with a
passphrase you supply when prompted. For that key to be
used (e.g. by x11vnc) the passphrase must be supplied
each time.
.IP
The "SAVE" notation described under \fB-ssl\fR applies as
well. (precede this option with \fB-ssldir\fR [dir] to refer
a directory besides the default ~/.vnc/certs)
.IP
The
.IR openssl (1)
program must be installed on the system
and available in PATH. After the Key file is encrypted
the command exits; the VNC server is not run.
.IP
Examples:
x11vnc \fB-sslEncKey\fR /path/to/foo.pem
x11vnc \fB-sslEncKey\fR SAVE
x11vnc \fB-sslEncKey\fR SAVE-charlie
.PP
\fB-sslCertInfo\fR \fI[pem]\fR
.IP
Prints out information about an existing PEM file.
In addition the public certificate is also printed.
The
.IR openssl (1)
program must be in PATH. Basically the
command "openssl x509 \fB-text"\fR is run on the pem.
.IP
The "SAVE" notation described under \fB-ssl\fR applies
as well.
.IP
Using "LIST" will give a list of all certs being
managed (in the ~/.vnc/certs dir, use \fB-ssldir\fR to refer
to another dir). "ALL" will print out the info for
every managed key (this can be very long). Giving a
client or server cert shortname will also try a lookup
(e.g. \fB-sslCertInfo\fR charlie). Use "LISTL" or "LL"
for a long (ls \fB-l\fR style) listing.
.IP
Using "HASHON" will create subdirs [dir]/HASH and
[dir]/HASH with OpenSSL hash filenames (e.g. 0d5fbbf1.0)
symlinks pointing up to the corresponding *.crt file.
([dir] is ~/.vnc/certs or one given by \fB-ssldir.)\fR
This is a useful way for other OpenSSL applications
(e.g. stunnel) to access all of the certs without
having to concatenate them. x11vnc will not use them
unless you specifically reference them. "HASHOFF"
removes these HASH subdirs.
.IP
The LIST, LISTL, LL, ALL, HASHON, HASHOFF words can
also be lowercase, e.g. "list".
.PP
\fB-sslDelCert\fR \fI[pem]\fR
.IP
Prompts you to delete all .crt .pem .key .req files
associated with [pem]. "SAVE" and lookups as in
\fB-sslCertInfo\fR apply as well.
.PP
\fB-stunnel\fR \fI[pem]\fR
.IP
Use the
.IR stunnel (8)
(www.stunnel.org) to provide an
encrypted SSL tunnel between viewers and x11vnc.
.IP
This external tunnel method was implemented prior to the
integrated \fB-ssl\fR encryption described above. It still
works well. This requires stunnel to be installed
on the system and available via PATH (n.b. stunnel is
often installed in sbin directories). Version 4.x of
stunnel is assumed (but see \fB-stunnel3\fR below.)
.IP
[pem] is optional, use "\fB-stunnel\fR \fI/path/to/stunnel.pem\fR"
to specify a PEM certificate file to pass to stunnel.
Whether one is needed or not depends on your stunnel
configuration. stunnel often generates one at install
time. See the stunnel documentation for details.
.IP
stunnel is started up as a child process of x11vnc and
any SSL connections stunnel receives are decrypted and
sent to x11vnc over a local socket. The strings
"The SSL VNC desktop is ..." and "SSLPORT=..."
are printed out at startup to indicate this.
.IP
The \fB-localhost\fR option is enforced by default
to avoid people routing around the SSL channel.
Set STUNNEL_DISABLE_LOCALHOST=1 before starting x11vnc
to disable the requirement.
.IP
Your VNC viewer will also need to be able to connect via
SSL. Unfortunately not too many do this. UltraVNC has
an encryption plugin but it does not seem to be SSL.
.IP
Also, in the x11vnc distribution, a patched TightVNC
Java applet is provided in classes/ssl that does SSL
connections (only).
.IP
It is also not too difficult to set up an stunnel or
other SSL tunnel on the viewer side. A simple example
on Unix using stunnel 3.x is:
.IP
% stunnel \fB-c\fR \fB-d\fR localhost:5901 \fB-r\fR remotehost:5900
% vncviewer localhost:1
.IP
For Windows, stunnel has been ported to it and there
are probably other such tools available. See the FAQ
for more examples.
.PP
\fB-stunnel3\fR \fI[pem]\fR
.IP
Use version 3.x stunnel command line syntax instead of
version 4.x
.PP
\fB-https\fR \fI[port]\fR
.IP
Choose a separate HTTPS port (-ssl mode only).
.IP
In \fB-ssl\fR mode, it turns out you can use the
single VNC port (e.g. 5900) for both VNC and HTTPS
connections. (HTTPS is used to retrieve a SSL-aware
VncViewer.jar applet that is provided with x11vnc).
Since both use SSL the implementation was extended to
detect if HTTP traffic (i.e. GET) is taking place and
handle it accordingly. The URL would be, e.g.:
.IP
https://mymachine.org:5900/
.IP
This is convenient for firewalls, etc, because only one
port needs to be allowed in. However, this heuristic
adds a few seconds delay to each connection and can be
unreliable (especially if the user takes much time to
ponder the Certificate dialogs in his browser, Java VM,
or VNC Viewer applet. That's right 3 separate "Are
you sure you want to connect" dialogs!)
.IP
So use the \fB-https\fR option to provide a separate, more
reliable HTTPS port that x11vnc will listen on. If
[port] is not provided (or is 0), one is autoselected.
The URL to use is printed out at startup.
.IP
The SSL Java applet directory is specified via the
\fB-httpdir\fR option. If not supplied it will try to guess
the directory as though the \fB-http\fR option was supplied.
.PP
\fB-usepw\fR
.IP
If no other password method was supplied on the command

1
x11vnc/x11vnc.h
Unescape View File

@ -119,6 +119,7 @@
#endif
#define noREL8x
#define REL8x
/*
* Beginning of support for small binary footprint build for embedded

2
x11vnc/x11vnc_defs.c
Unescape View File

@ -15,7 +15,7 @@ int xtrap_base_event_type = 0;
int xdamage_base_event_type = 0;
/* date +'lastmod: %Y-%m-%d' */
char lastmod[] = "0.8.2 lastmod: 2006-07-11";
char lastmod[] = "0.8.2 lastmod: 2006-07-12";
/* X display info */

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