Security & Access Control
This page summarizes the most relevant security and access control methods.
Storing of Sensitive Information
PX4 Logging
SDLOG_BACKEND controls where flight log data is written — to the FMU SD card, over MAVLink to the companion computer, or both. Note that on the Skynode S, SD card logging is unavailable and only logging on the companion side is possible. The content of the FMU SD card is unencrypted, while the companion computer is encrypted.
SDLOG_NO_POS_DAT allows position and GPS data to be excluded from logs entirely, which is useful in privacy-sensitive or operationally sensitive deployments where recording the vehicle's flight path is undesirable. Note that flight logs originating from flights with SDLOG_NO_POS_DAT are often missing crucial information for incident analysis.
PX4 Mission, Safe Points and Geofence Storage
SYS_DM_BACKEND controls the storage backend used by PX4's dataman module, which persistently stores operationally sensitive data including mission waypoints, mission state, geofence polygons, and safe points. Setting the backend to RAM rather than file means this data is never written to disk and is lost on power cycle, which can be desirable in deployments where residual mission data on the vehicle poses a security concern.
Skynode S does not have an SD card and thus the data is always only stored in RAM.
PX4 Secure Mode
The PX4 parameter COM_SEC_MODE_EN enables secure mode, which protects operationally sensitive information by automatically purging GCS-related data after landing. This includes deleting the Home position, mission, and land approaches, resetting the local position origin, and disabling the serial console — ensuring that details about the GCS location cannot be reconstructed from the vehicle after a flight.
Access Control
Production Image
Skynode releases ship with two image variants: a development image and a production image. On the production image, the MAVLink shell is password protected, the UART debug port is changed to read only, and parameter changes are blocked by default — the PX4 parameter MAV_PARAM_LOCK must be explicitly set to allow them. The development image has no such restrictions and is intended for integration and testing only; it should not be used in deployed vehicles.
PX4 Parameter Summary
BAT_CRIT_THR
minValue: 0.05 maxValue: 0.5 increment: 0.01 default: 0.07
Sets the threshold when the battery will be reported as critically low. This has to be lower than the low threshold. This threshold commonly will trigger RTL.
BAT_EMERGEN_THR
minValue: 0.03 maxValue: 0.5 increment: 0.01 default: 0.05
Sets the threshold when the battery will be reported as dangerously low. This has to be lower than the critical threshold. This threshold commonly will trigger landing.
BAT_LOW_THR
minValue: 0.12 maxValue: 0.5 increment: 0.01 default: 0.15
Sets the threshold when the battery will be reported as low. This has to be higher than the critical threshold. This threshold commonly will trigger landing.
CA_SV_CS0_TRIM
CA_SV_CS1_TRIM
CA_SV_CS2_TRIM
CA_SV_CS3_TRIM
CA_SV_CS4_TRIM
CA_SV_CS5_TRIM
CA_SV_CS6_TRIM
CA_SV_CS7_TRIM
minValue: -1.0 maxValue: 1.0 default: 0.0
Control Surface X trim, where X can be from 0->7.
Can be used to add an offset to the servo control. NOTE: Do not use for PWM servos. Use the PWM CENTER parameters instead (e.g., PWM_MAIN_CENT, PWM_AUX_CENT) instead. This parameter can only be set if all PWM Center parameters are set to default.
COM_DLL_EXCEPT
0: Mission
1: Auto modes
2: Offboard
3: External Mode
4: Altitude Cruise
Datalink loss exceptions.
Specify modes in which ground control station connection loss is ignored and no failsafe action is triggered. See also COM_RCL_EXCEPT.
COM_LOW_BAT_ACT
0: Warning
2: Land mode
3: Return at critical level, land at emergency level
4: Return at critical level, terminate at emergency level
Battery failsafe mode.
Action the system takes at critical battery. See also BAT_CRIT_THR and BAT_EMERGEN_THR for definition of battery states.
COM_RC_IN_MODE
0: RC only
1: MAVLink only
2: RC or MAVLink with fallback
3: RC or MAVLink keep first
4: Disable manual control
5: Prio: RC > MAVL 1 > MAVL 2
6: Prio: MAVL 1 > MAVL 2 > RC
7: Prio: RC > MAVL 2 > MAVL 1
8: Prio: MAVL 2 > MAVL 1 > RC
Manual control input source configuration.
Selects stick input selection behavior: either a traditional remote control receiver (RC) or a MAVLink joystick (MANUAL_CONTROL message)
Priority sources are immediately switched to whenever they get valid.
COM_RC_LOSS_T
minValue: 0 maxValue: 35 increment: 0.1 default: 0.5
Manual control loss timeout.
The time in seconds without a new setpoint from RC or Joystick, after which the connection is considered lost. This must be kept short as the vehicle will use the last supplied setpoint until the timeout triggers. Ensure the value is not set lower than the update interval of the RC or Joystick.
COM_WIND_MAX_ACT
0: None
1: Warning
2: Hold
3: Return
4: Terminate
5: Land
High wind failsafe mode.
Action the system takes when a wind speed above the specified threshold is detected. See COM_WIND_MAX to set the failsafe threshold. If enabled, it is not possible to resume the mission or switch to any auto mode other than RTL or Land if this threshold is exceeded. Taking over in any manual mode is still possible.
EKF2_AGP0_CTRL
EKF2_AGP1_CTRL
minValue: 0 maxValue: 3
Auxiliary global position sensor 0 aiding. Set bits in the following positions to enable: 0 : Horizontal position fusion 1 : Vertical position fusion
EKF2_GPS_CTRL
minValue: 0 maxValue: 15 default: 7
GNSS sensor aiding. Set bits in the following positions to enable: 0 : Longitude and latitude fusion 1 : Altitude fusion 2 : 3D velocity fusion 3 : Dual antenna heading fusion
GF_ACTION
0: None
1: Warning
2: Hold mode
3: Return mode
4: Terminate
5: Land mode
Geofence violation action.
Note: Setting this value to 4 enables flight termination, which will kill the vehicle on violation of the fence.
GF_MAX_HOR_DIST
minValue: 0 maxValue: 10000 default: 0.0
Max horizontal distance from Home.
Maximum horizontal distance in meters the vehicle can be from Home before triggering a geofence action. Disabled if 0.
GF_MAX_VER_DIST
minValue: 0 maxValue: 10000 default: 0.0
Max vertical distance from Home.
Maximum vertical distance in meters the vehicle can be from Home before triggering a geofence action. Disabled if 0.
MAV_SYS_ID
minValue: 1 maxValue: 250 default: 1
MAVLink system ID.
NAV_DLL_ACT
0: Disabled
1: Hold mode
2: Return mode
3: Land mode
5: Terminate
6: Disarm
Set GCS connection loss failsafe mode.
The GCS connection loss failsafe will only be entered after a timeout, set by COM_DL_LOSS_T in seconds. Once the timeout occurs the selected action will be executed.
NAV_RCL_ACT
1: Hold mode
2: Return mode
3: Land mode
5: Terminate
6: Disarm
7: Hold mode (no failsafe)
Set manual control loss failsafe mode.
The manual control loss failsafe will only be entered after a timeout, set by COM_RC_LOSS_T in seconds.
RTL_DESCEND_ALT
minValue: 0 increment: 0.5 default: 30.0
Return mode loiter altitude.
Descend to this altitude (above destination position) after return, and wait for time defined in RTL_LAND_DELAY. Land (i.e. slowly descend) from this altitude if autolanding allowed. VTOLs do transition to hover in this altitude above the landing point.
RTL_LAND_DELAY
minValue: -1 increment: 0.5 default: 0.0
Return mode delay.
Delay before landing (after initial descent) in Return mode. If set to -1 the system will not land but loiter at RTL_DESCEND_ALT.
RTL_RETURN_ALT
minValue: 0 increment: 0.5 default: 60.0
Return mode return altitude.
Default minimum altitude above destination (e.g. home, safe point, landing pattern) for return flight. The vehicle will climb to this altitude when Return mode is engaged, unless it currently is flying higher already. This is affected by RTL_MIN_DIST and RTL_CONE_ANG.
COM_SEC_MODE_EN
0: disabled 1: enabled
Purges GCS-related data after landing to protect operationally sensitive information.
MAV_PARAM_LOCK
0: Whitelist in restricted, full otherwise 1: Only whitelist 2: Full access
Prevents modification of parameters except for white-listed ones.
SDLOG_BACKEND
bit 0: FMU SD card bit 1: Companion computer
Selects where flight log data is written — FMU SD card, Companion computer (streamed over MAVLink), or both.
SDLOG_NO_POS_DAT
0: disabled 1: enabled
Excludes position and GPS data from flight logs.
SYS_DM_BACKEND
0: Default storage
1: RAM storage
Place to store Mission, Safe Points and Geofences. Default storage for Skynode X and N is the SD card, for Skynode S this parameter has no effect.
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