--- /dev/null
+From f1e7ec03e26ab6b8ca9b7ec060846a5b706a963d Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@redhat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [PATCH] 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>
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+---
+ server/reds.c | 25 +++++++++++++++++++++++--
+ 1 file changed, 23 insertions(+), 2 deletions(-)
+
+diff --git a/server/reds.c b/server/reds.c
+index f439a366..7be85fdf 100644
+--- a/server/reds.c
++++ b/server/reds.c
+@@ -993,19 +993,34 @@ static void reds_client_monitors_config_cleanup(void)
+ static void reds_on_main_agent_monitors_config(
+ 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;
+ }
+@@ -1013,6 +1028,12 @@ static void reds_on_main_agent_monitors_config(
+ spice_debug("%s: %d", __func__, monitors_config->num_of_monitors);
+ red_dispatcher_client_monitors_config(monitors_config);
+ reds_client_monitors_config_cleanup();
++ return;
++
++overflow:
++ spice_warning("received invalid MonitorsConfig request from client, disconnecting");
++ red_channel_client_disconnect(main_channel_client_get_base(mcc));
++ reds_client_monitors_config_cleanup();
+ }
+
+ void reds_on_main_agent_data(MainChannelClient *mcc, void *message, size_t size)
+--
+2.11.0
+
--- /dev/null
+From ec6229c79abe05d731953df5f7e9a05ec9f6df79 Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@redhat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [PATCH] reds: Avoid integer overflows handling monitor
+ configuration
+
+Avoid VDAgentMessage::size integer overflows.
+
+Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+---
+ server/reds.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/server/reds.c b/server/reds.c
+index 7be85fdf..e1c8c108 100644
+--- a/server/reds.c
++++ b/server/reds.c
+@@ -1024,6 +1024,9 @@ static void reds_on_main_agent_monitors_config(
+ spice_debug("not enough data yet. %d", cmc->buffer_size);
+ return;
+ }
++ if (msg_header->size < sizeof(VDAgentMonitorsConfig)) {
++ goto overflow;
++ }
+ monitors_config = (VDAgentMonitorsConfig *)(cmc->buffer + sizeof(*msg_header));
+ spice_debug("%s: %d", __func__, monitors_config->num_of_monitors);
+ red_dispatcher_client_monitors_config(monitors_config);
+--
+2.11.0
+
--- /dev/null
+From a957a90baf2c62d31f3547e56bba7d0e812d2331 Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@redhat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [PATCH] reds: Avoid buffer overflows handling monitor
+ configuration
+
+It was also possible for a malicious client to set
+VDAgentMonitorsConfig::num_of_monitors to a number larger
+than the actual size of VDAgentMOnitorsConfig::monitors.
+This would lead to buffer overflows, which could allow the guest to
+read part of the host memory. This might cause write overflows in the
+host as well, but controlling the content of such buffers seems
+complicated.
+
+Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
+Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
+---
+ server/reds.c | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/server/reds.c b/server/reds.c
+index e1c8c108..3a42c375 100644
+--- a/server/reds.c
++++ b/server/reds.c
+@@ -1000,6 +1000,7 @@ static void reds_on_main_agent_monitors_config(
+ VDAgentMessage *msg_header;
+ VDAgentMonitorsConfig *monitors_config;
+ RedsClientMonitorsConfig *cmc = &reds->client_monitors_config;
++ uint32_t max_monitors;
+
+ // limit size of message sent by the client as this can cause a DoS through
+ // memory exhaustion, or potentially some integer overflows
+@@ -1028,6 +1029,12 @@ static void reds_on_main_agent_monitors_config(
+ goto overflow;
+ }
+ monitors_config = (VDAgentMonitorsConfig *)(cmc->buffer + sizeof(*msg_header));
++ // limit the monitor number to avoid buffer overflows
++ max_monitors = (msg_header->size - sizeof(VDAgentMonitorsConfig)) /
++ sizeof(VDAgentMonConfig);
++ if (monitors_config->num_of_monitors > max_monitors) {
++ goto overflow;
++ }
+ spice_debug("%s: %d", __func__, monitors_config->num_of_monitors);
+ red_dispatcher_client_monitors_config(monitors_config);
+ reds_client_monitors_config_cleanup();
+--
+2.11.0
+
projects / buildroot.git / commitdiff