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Limit lenght to INT_MAX bytes in rfbProcessFileTransferReadBuffer()

This ammends 15bb719c03 fix for a heap
out-of-bound write access in rfbProcessFileTransferReadBuffer() when
reading a transfered file content in a server. The former fix did not
work on platforms with a 32-bit int type (expected by rfbReadExact()).

CVE-2018-15127
<https://github.com/LibVNC/libvncserver/issues/243>
<https://github.com/LibVNC/libvncserver/issues/273>

(cherry picked from commit 09e8fc02f59f16e2583b34fe1a270c238bd9ffec)
pull/3/head
Petr Písař 4 years ago committed by Slávek Banko
parent
commit
6142d389db
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  1. 7
      libvncserver/rfbserver.c

7
libvncserver/rfbserver.c

@ -83,6 +83,8 @@
#include <errno.h>
/* strftime() */
#include <time.h>
/* INT_MAX */
#include <limits.h>
#ifdef LIBVNCSERVER_WITH_WEBSOCKETS
#include "rfbssl.h"
@ -1469,8 +1471,11 @@ char *rfbProcessFileTransferReadBuffer(rfbClientPtr cl, uint32_t length)
0XFFFFFFFF, i.e. SIZE_MAX for 32-bit systems. On 64-bit systems, a length of 0XFFFFFFFF
will safely be allocated since this check will never trigger and malloc() can digest length+1
without problems as length is a uint32_t.
We also later pass length to rfbReadExact() that expects a signed int type and
that might wrap on platforms with a 32-bit int type if length is bigger
than 0X7FFFFFFF.
*/
if(length == SIZE_MAX) {
if(length == SIZE_MAX || length > INT_MAX) {
rfbErr("rfbProcessFileTransferReadBuffer: too big file transfer length requested: %u", (unsigned int)length);
rfbCloseClient(cl);
return NULL;

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