GCS_MAVLink: support for mavlink2 signing operations

libraries/GCS_MAVLink/GCS.h

@@ -309,6 +309,7 @@ private:
     static DataFlash_Class *dataflash_p;
     
     mavlink_signing_t signing;
+    static StorageAccess _signing_storage;
 
     // a vehicle can optionally snoop on messages for other systems
     static void (*msg_snoop)(const mavlink_message_t* msg);
@@ -352,4 +353,9 @@ private:
 
     // return true if this channel has hardware flow control
     bool have_flow_control(void);
+
+    void handle_setup_signing(const mavlink_message_t *msg);
+    bool signing_key_save(const struct SigningKey &key);
+    bool signing_key_load(struct SigningKey &key);
+    void load_signing_key(void);
 };

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -109,6 +109,9 @@ GCS_MAVLINK::setup_uart(const AP_SerialManager& serial_manager, AP_SerialManager
 
     // and init the gcs instance
     init(uart, mav_chan);
+
+    // load signing key
+    load_signing_key();
 }
 
 /**

libraries/GCS_MAVLink/GCS_Signing.cpp

@@ -0,0 +1,98 @@
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+
+/*
+  Code for handling MAVLink2 signing
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "GCS.h"
+
+extern const AP_HAL::HAL& hal;
+
+// storage object
+StorageAccess GCS_MAVLINK::_signing_storage(StorageManager::StorageKeys);
+
+// magic for versioning of the structure
+#define SIGNING_KEY_MAGIC 0x3852fcd1
+
+// structure stored in FRAM
+struct SigningKey {
+    uint32_t magic;
+    uint64_t timestamp;
+    uint8_t secret_key[32];
+};
+
+bool GCS_MAVLINK::signing_key_save(const struct SigningKey &key)
+{
+    if (_signing_storage.size() < sizeof(key)) {
+        return false;
+    }
+    return _signing_storage.write_block(0, &key, sizeof(key));
+}
+
+bool GCS_MAVLINK::signing_key_load(struct SigningKey &key)
+{
+    if (_signing_storage.size() < sizeof(key)) {
+        return false;
+    }
+    return _signing_storage.read_block(&key, 0, sizeof(key));
+}
+
+/*
+  handle a setup_signing message
+ */
+void GCS_MAVLINK::handle_setup_signing(const mavlink_message_t *msg)
+{
+    // decode
+    mavlink_setup_signing_t packet;
+    mavlink_msg_setup_signing_decode(msg, &packet);
+
+    struct SigningKey key;
+    key.magic = SIGNING_KEY_MAGIC;
+    key.timestamp = packet.initial_timestamp;
+    memcpy(key.secret_key, packet.secret_key, 32);
+
+    if (!signing_key_save(key)) {
+        hal.console->printf("Failed to save signing key");
+        return;
+    }
+
+    // activate it immediately
+    load_signing_key();
+}
+
+
+/*
+  load signing key
+ */
+void GCS_MAVLINK::load_signing_key(void)
+{
+    struct SigningKey key;
+    if (!signing_key_load(key)) {
+        hal.console->printf("Failed to load signing key");
+        return;
+    }
+    mavlink_status_t *status = mavlink_get_channel_status(chan);
+    if (status == NULL) {
+        hal.console->printf("Failed to load signing key - no status");
+        return;        
+    }
+    memcpy(signing.secret_key, key.secret_key, 32);
+    signing.link_id = (uint8_t)chan;
+    signing.timestamp = 1;
+    signing.flags = MAVLINK_SIGNING_FLAG_SIGN_OUTGOING;
+    
+    status->signing = &signing;
+}