From effa979582e34687688df36c9a10b33862f2581f Mon Sep 17 00:00:00 2001 From: Mauro Matteo Cascella Date: Sun, 25 Sep 2022 22:45:11 +0200 Subject: [PATCH] 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 Signed-off-by: Mauro Matteo Cascella Message-Id: <20220925204511.1103214-1-mcascell@redhat.com> Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index 310a873c21..8a2e176b64 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); -- 2.37.0.rc2