main/spice: fix for CVE-2017-7506. Fixes #7590

1 files changed, 151 insertions, 0 deletions

diff --git a/main/spice/CVE-2017-7506.patch b/main/spice/CVE-2017-7506.patch
new file mode 100644
index 0000000000..dcdeea6e7d
--- /dev/null
+++ b/main/spice/CVE-2017-7506.patch
@@ -0,0 +1,151 @@
+From 257f69d619fed407493156c8a7b952abc8a51314 Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@...hat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [spice-server 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@...hat.com>
+---
+ server/reds.c | 25 +++++++++++++++++++++++--
+ 1 file changed, 23 insertions(+), 2 deletions(-)
+
+diff --git a/server/reds.c b/server/reds.c
+index f439a3668..7be85fdfc 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)
+-- 
+2.13.0
+
+From ff2b4ef70181087d5abd50bad76d026ec5088a93 Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@...hat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [spice-server 2/3] reds: Avoid integer overflows handling monitor
+ configuration
+
+Avoid VDAgentMessage::size integer overflows.
+
+Signed-off-by: Frediano Ziglio <fziglio@...hat.com>
+---
+ server/reds.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/server/reds.c b/server/reds.c
+index 7be85fdfc..e1c8c1086 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);
+-- 
+2.13.0
+
+From 8cc3d7df2792751939cc832f4110c57e2addfca5 Mon Sep 17 00:00:00 2001
+From: Frediano Ziglio <fziglio@...hat.com>
+Date: Mon, 15 May 2017 15:57:28 +0100
+Subject: [spice-server 3/3] 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@...hat.com>
+---
+ server/reds.c | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/server/reds.c b/server/reds.c
+index e1c8c1086..3a42c3755 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();
+-- 
+2.13.0
+