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ui: check VNC audio frequency limit at time of reading from client 

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 <lersek@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180205114938.15784-4-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2018-02-05 11:49:37 +00:00 committed by Gerd Hoffmann
parent 52c7c9d076
commit cf0706581b
1 changed files with 13 additions and 9 deletions
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22
ui/vnc.c
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@ -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));