[Spice-devel] [PATCH spice-gtk 2/2] spice-channel: Avoid some buffer reading overflows

[Frediano Ziglio]

Check link message contains valid offset and array sizes.
The overflows do not produce data leaking as data are copied into
other client arrays and used only for checking limited bit arrays.
This remove possible client DoS.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 src/spice-channel.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/spice-channel.c b/src/spice-channel.c
index 7e5b2e7f..cc089ebb 100644
--- a/src/spice-channel.c
+++ b/src/spice-channel.c
@@ -1906,7 +1906,7 @@ static gboolean spice_channel_recv_link_msg(SpiceChannel *channel)
     int rc;
     uint32_t num_caps;
     uint32_t num_channel_caps, num_common_caps;
-    uint8_t *caps_src;
+    const uint8_t *caps_src, *caps_end;
     SpiceChannelEvent event = SPICE_CHANNEL_ERROR_LINK;
 
     g_return_val_if_fail(channel != NULL, FALSE);
@@ -1947,14 +1947,25 @@ static gboolean spice_channel_recv_link_msg(SpiceChannel *channel)
     num_caps = num_channel_caps + num_common_caps;
     CHANNEL_DEBUG(channel, "%s: %u caps", __FUNCTION__, num_caps);
 
+    if (c->peer_msg->caps_offset > c->peer_hdr.size) {
+        goto error;
+    }
+    caps_end = (uint8_t*)c->peer_msg + c->peer_hdr.size;
+
     /* see original spice/client code: */
     /* g_return_if_fail(c->peer_msg + c->peer_msg->caps_offset * sizeof(uint32_t) > c->peer_msg + c->peer_hdr.size); */
 
     caps_src = (uint8_t *)c->peer_msg + c->peer_msg->caps_offset;
+    if ((caps_end - caps_src) / sizeof(uint32_t) < num_common_caps) {
+        goto error;
+    }
     CHANNEL_DEBUG(channel, "got remote common caps:");
     store_caps(caps_src, num_common_caps, c->remote_common_caps);
 
     caps_src += num_common_caps * sizeof(uint32_t);
+    if ((caps_end - caps_src) / sizeof(uint32_t) < num_channel_caps) {
+        goto error;
+    }
     CHANNEL_DEBUG(channel, "got remote channel caps:");
     store_caps(caps_src, num_channel_caps, c->remote_caps);
 
-- 
2.17.2