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>
(cherry picked from commit f9a70e79391f6d7c2a912d785239ee8effc1922d)
Conflicts:
	ui/vnc.c

Dropped { } style changes.

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/vnc.c b/vnc.c
index 7629dfa18645684a60b9b1db3732193ecb3a5da3..86c2ff4c97bb7dbb48607aee980a01af2a16670e 100644 (file)
--- a/vnc.c
+++ b/vnc.c
@@ -1768,6 +1768,12 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len)
        if (len == 8) {
            uint32_t v;
            v = read_u32(data, 4);
+           if (v > (1 << 20)) {
+               error_report("vnc: client_cut_text msg payload has %u bytes"
+                             " which exceeds our limit of 1MB.", v);
+               vnc_client_error(vs);
+               break;
+           }
            if (v)
                return 8 + v;
        }