On Sun, Sep 25, 2022 at 10:45 PM Mauro Matteo Cascella
<mcasc...@redhat.com> wrote:
>
> 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 <tangp...@qianxin.com>
> Signed-off-by: Mauro Matteo Cascella <mcasc...@redhat.com>
> ---
> Extended Clipboard Pseudo-Encoding:
> https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#extended-clipboard-pseudo-encoding
>
> ui/vnc.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 6a05d06147..acb3629cd8 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
>
Any updates here?
Thanks,
--
Mauro Matteo Cascella
Red Hat Product Security
PGP-Key ID: BB3410B0
