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From 1c6517973095a67c8cb57f3550fc1298404ab556 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Tue, 13 Dec 2016 14:39:48 +0000
Subject: [PATCH] Prevent possible DoS attempts during protocol handshake
The limit for link message is specified using a 32 bit unsigned integer.
This could cause possible DoS due to excessive memory allocations and
some possible crashes.
For instance a value >= 2^31 causes a spice_assert to be triggered in
async_read_handler (reds-stream.c) due to an integer overflow at this
line:
int n = async->end - async->now;
This could be easily triggered with a program like
#!/usr/bin/env python
import socket
import time
from struct import pack
server = '127.0.0.1'
port = 5900
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((server, port))
data = pack('<4sIII', 'REDQ', 2, 2, 0xaaaaaaaa)
s.send(data)
time.sleep(1)
without requiring any authentication (the same can be done
with TLS).
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Christophe Fergeau <cfergeau@redhat.com>
---
server/reds.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/server/reds.c b/server/reds.c
index f40b65c1..86a33d53 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -2202,7 +2202,8 @@ static void reds_handle_read_header_done(void *opaque)
reds->peer_minor_version = header->minor_version;
- if (header->size < sizeof(SpiceLinkMess)) {
+ /* the check for 4096 is to avoid clients to cause arbitrary big memory allocations */
+ if (header->size < sizeof(SpiceLinkMess) || header->size > 4096) {
reds_send_link_error(link, SPICE_LINK_ERR_INVALID_DATA);
spice_warning("bad size %u", header->size);
reds_link_free(link);
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