From cf0706581bc0c24ab2e9a81ff0fc3efa9482c812 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Mon, 5 Feb 2018 11:49:37 +0000 Subject: [PATCH] ui: check VNC audio frequency limit at time of reading from client MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The 'vs->as.freq' value is a signed integer, which is read from an unsigned 32-bit int field on the wire. There is thus a risk of overflow on 32-bit platforms. Move the frequency limit checking to be done at time of read before casting to a signed integer. Reported-by: Laszlo Ersek Signed-off-by: Daniel P. Berrangé Reviewed-by: Laszlo Ersek Reviewed-by: Philippe Mathieu-Daudé Message-id: 20180205114938.15784-4-berrange@redhat.com Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/ui/vnc.c b/ui/vnc.c index 746293ddfa..a77b568b57 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -982,14 +982,7 @@ static void vnc_update_throttle_offset(VncState *vs) vs->client_width * vs->client_height * vs->client_pf.bytes_per_pixel; if (vs->audio_cap) { - int freq = vs->as.freq; - /* We don't limit freq when reading settings from client, so - * it could be upto MAX_INT in size. 48khz is a sensible - * upper bound for trustworthy clients */ int bps; - if (freq > 48000) { - freq = 48000; - } switch (vs->as.fmt) { default: case AUD_FMT_U8: @@ -1005,7 +998,7 @@ static void vnc_update_throttle_offset(VncState *vs) bps = 4; break; } - offset += freq * bps * vs->as.nchannels; + offset += vs->as.freq * bps * vs->as.nchannels; } /* Put a floor of 1MB on offset, so that if we have a large pending @@ -2292,6 +2285,7 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len) { int i; uint16_t limit; + uint32_t freq; VncDisplay *vd = vs->vd; if (data[0] > 3) { @@ -2411,7 +2405,17 @@ static int protocol_client_msg(VncState *vs, uint8_t *data, size_t len) vnc_client_error(vs); break; } - vs->as.freq = read_u32(data, 6); + freq = read_u32(data, 6); + /* No official limit for protocol, but 48khz is a sensible + * upper bound for trustworthy clients, and this limit + * protects calculations involving 'vs->as.freq' later. + */ + if (freq > 48000) { + VNC_DEBUG("Invalid audio frequency %u > 48000", freq); + vnc_client_error(vs); + break; + } + vs->as.freq = freq; break; default: VNC_DEBUG("Invalid audio message %d\n", read_u8(data, 4)); -- 2.11.4.GIT