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Matthias Maier <tamiko@gentoo.org>
- Ported to 0.13.3
From 111ab38611cef5012f1565a65fa2d8a8a05cce37 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Mon, 15 May 2017 15:57:28 +0100
Subject: [PATCH 1/3] reds: Disconnect when receiving overly big
ClientMonitorsConfig
Total message size received from the client was unlimited. There is
a 2kiB size check on individual agent messages, but the MonitorsConfig
message can be split in multiple chunks, and the size of the
non-chunked MonitorsConfig message was never checked. This could easily
lead to memory exhaustion on the host.
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
---
diff --git a/server/reds.c b/server/reds.c
index 92feea1..286993b 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1077,19 +1077,35 @@ static void reds_client_monitors_config_cleanup(RedsState *reds)
static void reds_on_main_agent_monitors_config(RedsState *reds,
MainChannelClient *mcc, void *message, size_t size)
{
+ const unsigned int MAX_MONITORS = 256;
+ const unsigned int MAX_MONITOR_CONFIG_SIZE =
+ sizeof(VDAgentMonitorsConfig) + MAX_MONITORS * sizeof(VDAgentMonConfig);
+
VDAgentMessage *msg_header;
VDAgentMonitorsConfig *monitors_config;
RedsClientMonitorsConfig *cmc = &reds->client_monitors_config;
+ // limit size of message sent by the client as this can cause a DoS through
+ // memory exhaustion, or potentially some integer overflows
+ if (sizeof(VDAgentMessage) + MAX_MONITOR_CONFIG_SIZE - cmc->buffer_size < size) {
+ goto overflow;
+ }
+
cmc->buffer_size += size;
cmc->buffer = realloc(cmc->buffer, cmc->buffer_size);
spice_assert(cmc->buffer);
cmc->mcc = mcc;
memcpy(cmc->buffer + cmc->buffer_pos, message, size);
cmc->buffer_pos += size;
+ if (sizeof(VDAgentMessage) > cmc->buffer_size) {
+ spice_debug("not enough data yet. %d", cmc->buffer_size);
+ return;
+ }
msg_header = (VDAgentMessage *)cmc->buffer;
- if (sizeof(VDAgentMessage) > cmc->buffer_size ||
- msg_header->size > cmc->buffer_size - sizeof(VDAgentMessage)) {
+ if (msg_header->size > MAX_MONITOR_CONFIG_SIZE) {
+ goto overflow;
+ }
+ if (msg_header->size > cmc->buffer_size - sizeof(VDAgentMessage)) {
spice_debug("not enough data yet. %d", cmc->buffer_size);
return;
}
@@ -1097,6 +1113,12 @@ static void reds_on_main_agent_monitors_config(RedsState *reds,
spice_debug("%s: %d", __func__, monitors_config->num_of_monitors);
reds_client_monitors_config(reds, monitors_config);
reds_client_monitors_config_cleanup(reds);
+ return;
+
+overflow:
+ spice_warning("received invalid MonitorsConfig request from client, disconnecting");
+ red_channel_client_disconnect(RED_CHANNEL_CLIENT(mcc));
+ reds_client_monitors_config_cleanup(reds);
}
void reds_on_main_agent_data(RedsState *reds, MainChannelClient *mcc, void *message, size_t size)
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