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>
diff --git a/ui/vnc.c b/ui/vnc.c
index 746293d..a77b568 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -982,14 +982,7 @@
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 @@
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 @@
{
int i;
uint16_t limit;
+ uint32_t freq;
VncDisplay *vd = vs->vd;
if (data[0] > 3) {
@@ -2411,7 +2405,17 @@
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));
