wswrapper:
Getting the wswrapper.c LD_PRELOAD model working has turned out to
involve too many dark corners of the glibc/POSIX file descriptor
space. I realized that 95% of what I want can be accomplished by
adding a "wrap command" mode to wsproxy.
The code is still there for now, but consider it experimental at
best. Minor fix to dup2 and add dup and dup3 logging.
wsproxy Wrap Command:
In wsproxy wrap command mode, a command line is specified instead
of a target address and port. wsproxy then uses a much simpler
LD_PRELOAD library, rebind.so, to move intercept any bind() system
calls made by the program. If the bind() call is for the wsproxy
listen port number then the real bind() system call is issued for
an alternate (free high) port on loopback/localhost. wsproxy then
forwards from the listen address/port to the moved port.
The --wrap-mode argument takes three options that determine the
behavior of wsproxy when the wrapped command returns an exit code
(exit or daemonizing): ignore, exit, respawn.
For example, this runs vncserver on turns port 5901 into
a WebSockets port (rebind.so must be built first):
./utils/wsproxy.py --wrap-mode=ignore 5901 -- vncserver :1
The vncserver command backgrounds itself so the wrap mode is set
to "ignore" so that wsproxy keeps running even after it receives
an exit code from vncserver.
wstelnet:
To demonstrate the wrap command mode, I added WebSockets telnet
client.
For example, this runs telnetd (krb5-telnetd) on turns port 2023
into a WebSockets port (using "respawn" mode since telnetd exits
after each connection closes):
sudo ./utils/wsproxy.py --wrap-mode=respawn 2023 -- telnetd -debug 2023
Then the utils/wstelnet.html page can be used to connect to the
telnetd server on port 2023. The telnet client includes VT100.js
(from http://code.google.com/p/sshconsole) which handles the
terminal emulation and rendering.
rebind:
The rebind LD_PRELOAD library is used by wsproxy in wrap command
mode to intercept bind() system calls and move the port to
a different port on loopback/localhost. The rebind.so library can
be built by running make in the utils directory.
The rebind library can be used separately from wsproxy by setting
the REBIND_OLD_PORT and REBIND_NEW_PORT environment variables
prior to executing a command. For example:
export export REBIND_PORT_OLD="23"
export export REBIND_PORT_NEW="65023"
LD_PRELOAD=./rebind.so telnetd -debug 23
Alternately, the rebind script does the same thing:
rebind 23 65023 telnetd -debug 23
Other changes/notes:
- wsproxy no longer daemonizes by default. Remove -f/--foreground
option and add -D/--deamon option.
- When wsproxy is used to wrap a command in "respawn" mode, the
command will not be respawn more often than 3 times within 10
seconds.
- Move getKeysym routine out of Canvas object so that it can be called
directly.
- add dup2 functionality. This requires adding a ref cnt to the
_WS_connections structure so that we only free the structure once
all dup'd referenced are closed. Also, refactor malloc and free of
connection structure into _WS_alloc and _WS_free.
- allow select to accept a NULL timeout value which means sleep
forever instead of segfaulting.
- fix some compile warnings related to ppoll definition.
- move some WebSockets related html test pages into utils and symlink
them from tests.
Moved websocket.py code into a class WebSocketServer. WebSockets
server implementations will sub-class and define a handler() method
which is passed the client socket after. Global variable settings have been
changed to be parameters for WebSocketServer when created.
Subclass implementations still have to handle queueing and sending but
the parent class handles everything else (daemonizing, websocket
handshake, encode/decode, etc). It would be better if the parent class
could handle queueing and sending. This adds some buffering and
polling complexity to the parent class but it would be better to do so
at some point. However, the result is still much cleaner as can be
seen in wsecho.py.
Refactored wsproxy.py and wstest.py (formerly ws.py) to use the new
class. Added wsecho.py as a simple echo server.
- rename tests/ws.py to utils/wstest.py and add a symlink from
tests/wstest.py
- rename tests/ws.html to tests/wstest.html to match utils/wstest.py.
- add utils/wsecho.py
- add tests/wsecho.html which communicates with wsecho.py and simply
sends periodic messages and shows what is received.
- Added ability to respond to normal web requests. This is basically
integrating web.py functionality into wsproxy. This is only in the
python version and it is off by default when calling wsproxy. Turn
it on with --web DIR where DIR is the web root directory.
Next task is to clean up wsproxy.py. It's gotten unwieldy and it
really no longer needs to be parallel to the C version.
Warn early about no SSL cert and add clearer warning when a connection
comes in as SSL but no cert file exists.
For the C version, cleanup closing of the connection socket. Use
shutdown for a cleaner cleanup with the client.
The select call needs to timeout if a WebSocket socket keeps reporting
ready but actually isn't ready. To prevent it hanging forever in that
condition, the timeout value is now adjusted now for each call.
Move the DO_DEBUG and DO_TRACE settings to wswrapper.c.
Interpose on select/pselect so that WebSockets sockets are only
reported as ready if they have enough to actually decode at least
1 byte of real data. This prevents hanging in read/recv after
WebSocket is reported as ready but is not actually ready because empty
frames or less than four base64 bytes have been received.
Split defines and constant defintions into wswrapper.h.
Cleanup debug output and add TRACE for more detailed tracing debug
output.
Major TODO is that select needs to timeout if WebSocket socket keeps
reporting ready but actually isn't ready. That condition will
currently hang forever because the select timeout value is not
adjusted when looping.
Make path to ld preload library absolute so wswrapper works even if
path is changed before main program is executed (i.e. by the vncserver
wrapper script).
bind() was using the return value for the port number, but it's
actually the original port number that we should interpose on in the
bind() routine.
Allocate buffer and state memory for each accepted connection. This
allows all WebSockets connections to a given listen port to be wrapped
with WebSockets support.
wswrapper.so will only interpose on the listen port specified in
WSWRAP_PORT.
Add simple wswrap script that sets the WSWRAP_PORT, LD_PRELOAD and
invokes the command line to wrap.
Rename the $() selector to $D() so that it doesn't collide with
the jQuery name.
The API change is that the 'target' option for Canvas and RFB objects
must now be a DOM Canvas element. A string is no longer accepted
because this requires that a DOM lookup is done and the Canvas and RFB
should have no UI code in them. Modularity.
wswrapper.so is LD_PRELOAD shared library that interposes and turns
a generic TCP socket into a WebSockets service.
This current version works but will only allow work for a single
connection, subsequent connections will not be wrapped. In addition
the wrapper interposes on the first incoming network connection. It
should read an environment variable to determine the port to interpose
on. Also, should limit origin based on another environment variable.
Then there should be a wswrap setup script that allows easier
invocation.
Only call encode_message when the WebSockets object is actually
ready to send. Otherwise multiple base64 encode sequences can be
encoded into the same WebSockets frame. This causes the C version of
wsproxy to crash and the python version to ignore the subsequent
base64 sequence(s).
Thanks to Colin Dean (xvpsource.org) for finding this and helping
track it down.
- Add meta tag to vnc.html and vnc_auto.html so that if Chrome Frame
is installed, it is used.
- Add detection to default_controls.js that shows a message with
a Chrome Frame install link if the user is using a version of IE
without Canvas support.
- Fix web.py so that requests have their connection closed after they
are completed. This has been a bug for a while but it prevents
Chrome Frame from working because Chrome Frame doesn't activate
until the initial request connection closes.
Node:
http://nodejs.org/https://github.com/ry/node
It mostly works, but it eventually gets an error from the target which
is probably due to missing support for re-assembly of client
WebSockets frames.
This is WebKit bug https://bugs.webkit.org/show_bug.cgi?id=46319
The workaround is to wrap Canvas render functions with a function that
sets a flush timer. The flush function sets the right margin and then
1ms later sets it back. This triggers the canvas to redraw with the
correct contents.
Two downsides:
- rendering is slower, but only on the busted versions of webkit.
Correct and useful is better than fast and useless.
- There is a barely perceptible jitter of the control buttons because
the canvas size is changing by one pixel.
To support this functionality, we also have to read out the exact
webkit version from the user agent in the render engine detection code
in include/util.js.
- Make sure that canvas exists (i.e. didn't throw an error) before
trying to call canvas method get_canvas_uri.
- Typos in HTML render engine debug output.
- pass CFLAGS and LDFLAGS in case one needs to use -m32
- link to libcrypto for _ERR_print_errors_fp
- __THROW is non-standard define it to nothing by default
- use b64_ntop and b64_pton instead of mangled versions, OSX doesn't mangle them in the same way
- access() takes two arguments!
Signed-off-by: François Revol <revol@free.fr>
- Split out ClientInitialisation state.
- In version 3.3 and 3.7, when the server has no auth (scheme
1), then we should skip from Authentication to ClientInitialisation.
- Add wsproxy README.md in utils/ directory.
- Document how to build ssl module for python 2.5 and older in wsproxy
README.
- Update browsers.md to note revision that have the webkit Canvas
rendering bug: WebKit build 66396 through 68867 (Chrome/Chromium
build 57968 through 61278).
Joel Martin
Amir Malik
François Revol