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ui/vnc: limit client_cut_text msg payload size 

currently a malicious client could define a payload
size of 2^32 - 1 bytes and send up to that size of
data to the vnc server. The server would allocated
that amount of memory which could easily create an
out of memory condition.

This patch limits the payload size to 1MB max.

Please note that client_cut_text messages are currently
silently ignored.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Peter Lieven 2014-06-30 10:07:54 +02:00 committed by Gerd Hoffmann
parent b3959efdbb
commit f9a70e7939
1 changed files with 10 additions and 3 deletions
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13
ui/vnc.c
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@ -2165,13 +2165,20 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len)
pointer_event(vs, read_u8(data, 1), read_u16(data, 2), read_u16(data, 4));
break;
case VNC_MSG_CLIENT_CUT_TEXT:
if (len == 1)
if (len == 1) {
return 8;
}
if (len == 8) {
uint32_t dlen = read_u32(data, 4);
if (dlen > 0)
if (dlen > (1 << 20)) {
error_report("vnc: client_cut_text msg payload has %u bytes"
" which exceeds our limit of 1MB.", dlen);
vnc_client_error(vs);
break;
}
if (dlen > 0) {
return 8 + dlen;
}
}
client_cut_text(vs, read_u32(data, 4), data + 8);