From d3602e5afa1e90c5e33625fc528db7f96195bada Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Mon, 7 Nov 2022 19:59:46 -0500
Subject: [PATCH 42/42] ui/vnc-clipboard: fix integer underflow in
 vnc_client_cut_text_ext
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: Jon Maloy <jmaloy@redhat.com>
RH-MergeRequest: 227: ui/vnc-clipboard: fix integer underflow in vnc_client_cut_text_ext
RH-Bugzilla: 2129760
RH-Acked-by: Mauro Matteo Cascella <None>
RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
RH-Commit: [1/1] ac19a6c0777e308061bcb6d1de5cc9beaa105a3a (jmaloy/qemu-kvm)

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2129760
CVE: CVE-2022-3165
Upstream: Merged

commit d307040b18bfcb1393b910f1bae753d5c12a4dc7
Author: Mauro Matteo Cascella <mcascell@redhat.com>
Date:   Sun Sep 25 22:45:11 2022 +0200

    ui/vnc-clipboard: fix integer underflow in vnc_client_cut_text_ext

    Extended ClientCutText messages start with a 4-byte header. If len < 4,
    an integer underflow occurs in vnc_client_cut_text_ext. The result is
    used to decompress data in a while loop in inflate_buffer, leading to
    CPU consumption and denial of service. Prevent this by checking dlen in
    protocol_client_msg.

    Fixes: CVE-2022-3165
    Fixes: 0bf41cab93e5 ("ui/vnc: clipboard support")
    Reported-by: TangPeng <tangpeng@qianxin.com>
    Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
    Message-Id: <20220925204511.1103214-1-mcascell@redhat.com>
    Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

(cherry picked from commit d307040b18bfcb1393b910f1bae753d5c12a4dc7)
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 ui/vnc.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/ui/vnc.c b/ui/vnc.c
index af02522e84..a14b6861be 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2442,8 +2442,8 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len)
         if (len == 1) {
             return 8;
         }
+        uint32_t dlen = abs(read_s32(data, 4));
         if (len == 8) {
-            uint32_t dlen = abs(read_s32(data, 4));
             if (dlen > (1 << 20)) {
                 error_report("vnc: client_cut_text msg payload has %u bytes"
                              " which exceeds our limit of 1MB.", dlen);
@@ -2456,8 +2456,13 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len)
         }
 
         if (read_s32(data, 4) < 0) {
-            vnc_client_cut_text_ext(vs, abs(read_s32(data, 4)),
-                                    read_u32(data, 8), data + 12);
+            if (dlen < 4) {
+                error_report("vnc: malformed payload (header less than 4 bytes)"
+                             " in extended clipboard pseudo-encoding.");
+                vnc_client_error(vs);
+                break;
+            }
+            vnc_client_cut_text_ext(vs, dlen, read_u32(data, 8), data + 12);
             break;
         }
         vnc_client_cut_text(vs, read_u32(data, 4), data + 8);
-- 
2.37.3