WEBVTT 00:04.970 --> 00:06.070 I'm Aaron Grelias. 00:06.070 --> 00:08.130 I'm a security researcher with Grimm. 00:08.130 --> 00:10.270 I'm on the cyber physical systems team. 00:10.270 --> 00:16.430 We work on improving the security of embedded devices everywhere. 00:16.430 --> 00:29.310 I've also got a background, a long background in embedded software development on critical systems, the telecom, aerospace, medical, and a bunch of different fields. 00:30.550 --> 00:32.030 My name is Tim Brown. 00:32.030 --> 00:35.050 I run the cyber physical systems team here at Grimm. 00:35.050 --> 00:45.230 I've been at Grimm for about five years now, hacking all sorts of different types of embedded systems from aerospace to automotive, heavy trucking, medical. 00:46.710 --> 00:52.510 And we're here today to talk about some of where cybersecurity meets aviation regulations. 01:05.510 --> 01:10.890 I'm going to start by talking about the current status of cybersecurity regulation. 01:10.890 --> 01:16.570 And more how software development happens in aerospace. 01:18.270 --> 01:28.110 The current process that we have descends from the, historically, how airlines have approached the topic of safety. 01:28.110 --> 01:35.530 Airlines have approached the topic of safety, usually, historically, from a purely mechanical standpoint. 01:35.530 --> 01:39.610 This part will last for about this long in airplanes. 01:39.610 --> 01:41.530 It has to be replaced every so often. 01:41.530 --> 01:49.810 There's maintenance procedures and airworthiness directives that talk about how often these parts need to be replaced based on how long it takes them to fail. 01:49.850 --> 02:07.070 There's things that they test, like anywhere you have stresses on a metal joint, you'll have testing done, both visual inspection and other types of testing, depending on circumstances, to see if it's starting to fail, if it's starting to get cracks forming in those areas. 02:07.230 --> 02:17.970 But it's really designed around this concept that once you make a part, it behaves in some sort of defined way that doesn't change. 02:17.970 --> 02:30.530 Once you design it, do all your fairly rigorous testing that they do in the airline, the aerospace industry, and install it, it will change in ways that are defined, essentially, by the physics of the situation. 02:30.530 --> 02:40.610 Stresses on metal, opening and closings of latches, and stuff like that, that have a defined physical characteristic. 02:40.610 --> 02:47.970 And you can define maintenance procedures that will detect all of these potential issues on the airplane. 02:47.970 --> 02:53.410 Maintenance procedures are defined to replace things that need to be replaced periodically. 02:53.410 --> 03:01.110 These maintenance procedures you can follow in the commercial aerospace world will be followed. 03:01.110 --> 03:04.650 They rely on that happening, that does happen. 03:05.150 --> 03:07.910 And they do it in places like this. 03:07.910 --> 03:15.290 They have drawers that have labeled places for every bit, every socket, every tool. 03:15.290 --> 03:16.890 It's access controlled. 03:16.890 --> 03:25.810 So you know that when you do your maintenance procedure, there's a procedure for using this size socket to remove these bolts and you put it back when you're done. 03:25.810 --> 03:29.050 So you don't wind up leaving a socket in an airplane. 03:29.050 --> 03:38.830 They have these fairly strictly defined procedures that you follow in order to make sure that all these maintenance is done correctly and done completely. 03:42.510 --> 03:47.190 So that's the kind of history of where we came from. 03:47.190 --> 04:02.970 As far as the current regulations that drive the software development process for modern aviation software, that's regulated at least in this country and many other ones by something called DO-178C. 04:03.230 --> 04:17.350 We're not going to go into this too deeply, but knowing how things work right now and how levels of safety are defined will help us think about cybersecurity and how to go forward with that. 04:17.730 --> 04:20.410 This is developed by RTCA. 04:20.430 --> 04:27.530 It stands for Radio Technical Commissions for Aeronautics, which I never actually knew until I looked that up. 04:27.530 --> 04:28.690 It's not super important. 04:28.690 --> 04:31.850 It's just an organization that develops a bunch of aviation standards. 04:34.350 --> 04:43.870 And again, these are adopted by FAA in the United States, Transport Canada, and European Aviation Safety Agency, EASA. 04:45.490 --> 04:47.550 So what is DO-178C? 04:47.550 --> 04:49.510 I like to summarize it this way. 04:49.570 --> 04:58.490 You basically tell the FAA... well, a DER is the designated representative that stands in for the FAA. 04:58.490 --> 05:03.990 Tell them how you plan on designing, creating, and testing your software. 05:04.310 --> 05:07.750 And then you go and follow your plan and do those things. 05:07.750 --> 05:09.870 And then you have to prove that you followed your plan. 05:09.870 --> 05:11.750 That's it in a nutshell. 05:11.990 --> 05:15.150 Now there's a lot more paperwork involved. 05:15.150 --> 05:23.970 There's a lot of checklists you do have to go through and make sure that your plan actually does identify all the areas of concern that DO-178C points out. 05:24.290 --> 05:35.850 And if the DER thinks that anything is lacking in your plan, they will tell you and help you make sure that it gets revised appropriately. 05:36.010 --> 05:39.170 That's the way things go forward right now. 05:39.170 --> 06:06.090 And as you can see, it's kind of a very waterfall-y based model where you do all your design up front, you create a design, you create a spec, the actual product that implements the design, then you do testing on it in order to make sure that the product design actually meets the requirements that the product was supposed to fulfill. 06:06.350 --> 06:07.730 That is a good point. 06:07.730 --> 06:11.990 The way this does work in practice, it is extremely waterfall. 06:13.370 --> 06:20.930 There have been attempts to try and figure out how to fit Agile methods into this, but it is very much plan, do, prove. 06:21.170 --> 06:23.210 Just pretty much in those steps. 06:23.450 --> 06:30.930 And this again comes from that historical background of making mostly mechanical components where that is how you design them. 06:30.930 --> 06:37.670 You don't do iterative development on, you know, a weight usually. 06:37.670 --> 06:45.510 I mean, if there's issues, you'll go back and fix them of course, but like you don't really do, you know, there is no fail fast on making a lot of these mechanical components. 06:45.510 --> 06:54.150 So it's trying to shoehorn software development into how they make mechanical components for these aircraft. 06:54.370 --> 07:02.070 And as anybody who's been in software development for a while knows that waterfall has been around for a long time. 07:02.870 --> 07:12.230 The DO-178C categorizes different levels of software according to the potential consequences of a failure of that software. 07:13.090 --> 07:21.890 So levels A through E, and basically A means that something catastrophic would happen if it fails. 07:22.270 --> 07:30.370 Level E means that nothing is going to happen safety wise, you know, maybe the passengers can't watch movies, right? 07:30.370 --> 07:32.790 That would be a level E software. 07:33.530 --> 07:36.610 The level A is also the highest cost. 07:36.610 --> 07:37.950 This is probably unsurprising. 07:41.230 --> 07:49.630 The last numbers I can find show that it's estimated to be about $100 per line of code for level A software. 07:51.050 --> 07:54.530 They're not all software on an airplane is level A. 07:54.530 --> 07:58.430 It's usually just as small percentage as possible because of the cost. 07:58.830 --> 08:04.530 But Boeing 787, for example, is estimated to have between 6 and 7 million lines of code. 08:04.530 --> 08:12.610 So even if it's a small percentage, just the level of certification alone of the software drives a great deal of cost. 08:13.470 --> 08:16.030 Basically, these go from different levels. 08:16.150 --> 08:32.430 So level A, catastrophic software, usually software that is level A rated will have autonomous control, which means that there's no way to intervene if something fails, hence why it's so expensive and so time consuming to develop. 08:32.430 --> 08:34.170 Then they go on both. 08:34.170 --> 08:43.570 Level B would be something where something hazardous could happen, but also level B will typically allow for pilot intervention. 08:43.890 --> 08:56.250 So it might be something that significantly increases the workload or the challenge of flying the aircraft, but it would be something that can be addressed by the pilot training. 08:56.250 --> 08:59.430 Level A and B is usually loss of life. 08:59.430 --> 09:03.830 A level A failure was likely to lead to loss of life. 09:03.830 --> 09:10.450 Level B failure is not likely to lead to loss of life or severe injury. 09:11.030 --> 09:15.330 Injury sustained in a level B failure should be minimal. 09:17.130 --> 09:19.330 And then it goes on down from there. 09:19.330 --> 09:24.390 C and D are major minor impacts to the flight of the aircraft. 09:27.750 --> 09:37.810 Also, so entertainment systems are going to be level E, means that there's lower, less regulations and less checklists, essentially. 09:37.810 --> 09:43.630 As you go down in level, you have to do less to prove in that proof step. 09:47.100 --> 09:51.920 In DO-178C, code is expensive. 09:51.920 --> 10:02.760 So stuff, especially if it's a level B or level A, very unlikely to have unused code in it or unnecessary code in it, like a shell onto a system . 10:04.860 --> 10:15.380 DO-178A, you're not allowed to have dead code in your design on the system. 10:16.600 --> 10:23.480 Because it's so expensive to develop the code, there's usually a minimal amount of code on these systems. 10:23.480 --> 10:28.640 There is extensive testing done for the higher certification levels. 10:28.640 --> 10:32.060 There's at least a significant quantity of testing done. 10:33.000 --> 10:40.400 Pilot training on how to use the software is... the systems are designed for redundancy and safety. 10:40.400 --> 10:46.880 So if you do have a failure, there should be a redundant system to back up that failure. 10:46.880 --> 10:50.620 Unless you have a 737 MAX, we won't talk about that right now. 10:51.480 --> 10:56.120 Very limited interfaces on these flight-critical systems. 10:56.220 --> 10:58.240 They use interfaces like RN429. 10:58.240 --> 11:01.180 RN429 is a UART-style bus. 11:01.180 --> 11:07.560 You're limited to sending 32 bits of data at a time. 11:07.560 --> 11:10.060 There's not really room for buffer overflow here. 11:10.060 --> 11:14.100 You don't really have longer messages on top of RN429. 11:14.500 --> 11:25.180 These interfaces are very strictly defined and fairly provide very limited functionality beyond just sending the necessary critical data back and forth on the bus. 11:25.180 --> 11:29.320 There's a great deal of emphasis on determinism and reliability. 11:34.300 --> 11:46.180 So there's some bad things related to the current way software is defined and designed in aerospace. 11:47.160 --> 11:59.240 This is kind of... so as I said, you know, as we said, both Tim and I have worked in aerospace kind of on the development side of things and also on the cybersecurity testing side of things. 11:59.760 --> 12:06.920 The things that... I found many things frustrating when I was doing on the development side of things. 12:06.920 --> 12:11.480 This is kind of the... a piece of that list right here. 12:11.500 --> 12:17.440 Data validation is guarding against accidental data modification. 12:17.440 --> 12:28.720 The design of how software is made to be robust in aviation systems is guarding against like cosmic rate bit flips, single event upsets. 12:28.720 --> 12:34.040 So simple methods like CRCs and checksums are sufficient. 12:34.040 --> 12:49.180 And also the software that runs it is typically slower and older, more reliable, and therefore modern data validation methods are... can be very time consuming for those... for the hardware involved. 12:49.280 --> 12:52.320 There's very little code to guard against unexpected scenarios. 12:52.320 --> 13:11.630 If you don't... if it's... if every single line of code costs a hundred dollars approximately, probably more nowadays than it was when I found that statistic, then you're not going to have a code for guarding against things that the system designers say won't happen. 13:11.630 --> 13:18.790 In fact, as Tim says, dead code, code that is never expected to be executed, is not allowed in DO-178C. 13:20.470 --> 13:22.410 The... there's a lot of complacency. 13:22.410 --> 13:39.470 Because of the level of tests involved, because of the amount of work that goes into designing the software, there's a lot of point of view in the industry that the way we do things, the redundancies that we design into the system, protect us from bad things. 13:39.630 --> 13:42.150 And it protects against single event upsets. 13:42.150 --> 13:47.570 It doesn't protect against determined and directed attacks. 13:48.190 --> 13:58.130 One thing... one piece of software I was working on a while ago had a... just a straight-up buffer overflow attack against it. 13:58.150 --> 14:14.930 And I had to fight fairly hard to actually get it fixed, because the incoming data that hit that function with the buffer overflow could only come from a trusted source that would never send more than such amount of data. 14:14.990 --> 14:29.390 And if there was some sort of, like Aaron says, a single event upset, a sort of random bit flip that caused the length field to be longer than it was supposed to be, there's a CRC check that would have failed, and wouldn't have even processed the data at all. 14:29.390 --> 14:42.830 So they felt that they were completely protected against this scenario, because they just don't have this concept of an adversarial attacker with knowledge of the system being able to get data into this function. 14:42.830 --> 14:53.510 They believe that the only way for data to get into this function is from a source that they trust to not send data that's going to cause a buffer overflow. 14:54.530 --> 14:56.590 So Tim's kind of jumping ahead there. 14:56.590 --> 15:02.130 That last bullet point on this one is software is only tested against expected flight configurations. 15:02.370 --> 15:10.590 So you will only say, here's, you know, this is what we're going to do for this flight, and that's what we're testing, because testing is expensive. 15:10.590 --> 15:15.090 There's a lot of tests that are performed as part of this software certification process. 15:15.090 --> 15:17.410 You don't want to run more than necessary. 15:17.570 --> 15:33.510 What that means, though, is that software, aviation software, while robust in flight configurations, can be extremely brittle when it is put into conditions that it is not, that are not expected to happen. 15:34.410 --> 15:46.110 Some other things here, ground maintenance devices, so things that actually program the different flight devices, those are not D1C rated, because they're not flying, right? 15:46.110 --> 15:48.690 They just stay on the ground while the airplane flies. 15:48.730 --> 15:58.010 They're covered under some different guidelines about tool development, but you don't have to go, they're not even leveling certified, it's something different. 15:59.650 --> 16:06.350 Maintenance software, so on each box, there's typically a component that will help reprogram that device. 16:06.990 --> 16:16.450 That's considered to be deactivated, because when the airplane is in flight, you have a signal that says, are we, are the wheels on the ground or not? 16:16.450 --> 16:19.530 Sometimes it's called weight on wheels, sometimes it's called weight off wheels. 16:19.530 --> 16:22.070 Make sure you read your documentation very carefully. 16:23.430 --> 16:37.890 And whatever signal that is, indicates if the, that signal is then used in the startup process to make sure that the reprogramming software, that component, doesn't run. 16:37.930 --> 16:40.590 So this is considered to be deactivated. 16:40.970 --> 16:49.410 There's also frequently a physical switch on the piece of hardware they have to switch into some sort of boot mode, maintenance mode, programming mode. 16:49.410 --> 17:02.810 So you have to not only have the weight on wheels signal, but you also have to have this switch set in the activated position to boot the piece of hardware into the maintenance mode. 17:02.810 --> 17:08.830 And then the plane won't fly if that piece of hardware is in its maintenance mode or programming mode. 17:08.830 --> 17:12.770 You have to switch it back to flight mode before the plane will take off. 17:12.770 --> 17:18.010 Right, and it'll be like programmed sometimes that are built into the wiring harnesses themselves. 17:18.010 --> 17:25.670 So when you plug in the harness for reprogramming a box, that thing has a wire jumper in it that forces this type of mode. 17:30.090 --> 17:36.830 So there are some current cybersecurity documents out there, DO-326, which 17:41.550 --> 17:43.270 DO -326, 17:48.290 --> 17:54.190 which outlines the activities that should take place at a system and airframe levels. 17:54.190 --> 18:03.130 These are the type of security activities that you should do if you're developing either a system for an airplane or developing the entire airplane. 18:03.290 --> 18:10.330 These are the various testing activities and testing documents that you should create and how to create them. 18:10.610 --> 18:16.570 DO-356 goes a little bit more into the nuts and bolts of what testing should look like. 18:16.890 --> 18:27.090 Something I like about DO-356 is DO-356 does make provisions for the more ad hoc pentest style testing that hackers tend to do. 18:27.090 --> 18:39.090 You know, the adversarial feeling around trying to see, you know, scan different systems, trying to find some way and some chink in the armor that you can then exploit into the system. 18:39.090 --> 18:47.470 This is a testing that's much... most testing that you see, especially the DO-178C type testing, is extremely formalized. 18:47.470 --> 18:49.670 Every test procedure is written down. 18:49.670 --> 18:51.190 You do this set of procedures. 18:51.190 --> 18:52.390 This is your test. 18:52.390 --> 18:55.090 That's going to... there's conditions to pass. 18:55.350 --> 18:59.230 There's conditions for... and if they don't meet the passing conditions, the test failed. 19:00.030 --> 19:07.710 DO-356 does provide those provisions for the more ad hoc style testing that can be much more useful for security testing. 19:07.710 --> 19:16.310 Provisions for things like fuzzing, which doesn't really have an analog in like DO-178C, but you can't really formalize a fuzzing procedure. 19:18.690 --> 19:21.730 So that's where we are right now. 19:22.070 --> 19:29.050 We've got some concerns with the current way aviation software is currently defined. 19:29.070 --> 19:30.490 What do we do? 19:30.570 --> 19:32.150 So what do we do about that? 19:32.150 --> 19:34.410 Well, Tim and I have a plan. 19:36.670 --> 19:51.370 First, you know, as with anything, we've got to figure out what our actual goals are for how to... what needs to be secured, what devices need to be secured, and come up with some examples, come up with some measures that we can use to reach those goals. 19:51.370 --> 20:05.030 It's all very well and good to say secure the system, but if you don't actually tell people how to go about doing that, you're going to end up with a large number of ways to do that, some of which may not be very effective. 20:08.320 --> 20:13.700 So the problem is up front here, everything is hackable, right? 20:13.780 --> 20:17.400 Give some... give enough access, motivation, time, and money. 20:17.400 --> 20:19.940 You can get into any type of device. 20:19.940 --> 20:23.560 You give us a piece of hardware, and we can get into it. 20:24.840 --> 20:36.240 There's a lot of measures you can use to make it more difficult, but depend... with a large enough playground, you can get into anything you want. 20:42.270 --> 20:53.390 So for goals here, we... so for goals here, we need to assume that attacker has all the necessary information and resources to do what they want to. 20:53.470 --> 21:04.430 If we're going to... if we're going to design an aircraft to be secure, we need to start from the assumption that the adversary knows what they need to know to get into it. 21:04.990 --> 21:18.230 We need to make sure that we have some way to prove beyond the most up-to-date way to prove that the software on a particular component is 100% correct. 21:18.230 --> 21:26.210 If you cannot prove that, then it's going to be impossible to figure out how to get to secure an aircraft. 21:28.230 --> 21:32.810 We need to prevent accidental transmission of something malicious. 21:32.810 --> 21:42.250 If you know that everything is secure at some point in time, you need to, you know, protect it from going forward, and then put multiple barriers in place also to all these different components. 21:42.970 --> 21:49.850 We know that given enough time and money and so on, anybody can get into a device if they want to. 21:49.850 --> 22:00.830 But it is possible to figure out how to prevent, make an attack practically impossible if you limit some of those things. 22:00.830 --> 22:17.630 So if you know when an airplane is on the ground, that it has all of the correct software and configurations in all of the different parts that are on the aircraft, then an attacker would have a limited time frame of the actual flight itself to perform an attack. 22:17.630 --> 22:20.350 So that's what we're aiming for. 22:20.650 --> 22:34.970 And also aiming to get the idea into aviation that a software component can go from good to bad very quickly. 22:35.010 --> 22:42.890 Just one exploit and all of a sudden this device that was working completely fine is now no longer working completely fine. 22:42.890 --> 22:48.730 And it's not based on some statistical degradation over time. 22:48.730 --> 22:51.510 Now that can just go be good and then be bad. 22:55.910 --> 23:01.150 So to define what is important to secure, here's my list. 23:01.170 --> 23:04.450 We have things that are important for flying an aircraft. 23:04.550 --> 23:07.890 And then we have things that are not important for flying the aircraft. 23:07.890 --> 23:10.870 These are two device categories. 23:11.330 --> 23:25.370 The level D-178C defines five different levels to how critical software is and the consequences of failures here. 23:25.530 --> 23:30.090 For us, there's really only two categories, important or not. 23:30.110 --> 23:41.250 Because if you leave something that has partial measures in place on the aircraft, then that is a potential point that an attacker could use to pivot to other parts of the aircraft. 23:48.730 --> 23:54.570 So flight devices are any component that's used to operate the aircraft. 23:55.310 --> 23:58.470 Any or any device that communicates with those components. 23:58.470 --> 24:09.730 We've seen instances where you have, you may have a level E hardware device that communicates in some way with even a level A hardware device. 24:09.910 --> 24:31.070 And this is allowed because that communication has been strictly defined and tested on the piece of hardware, the level A software, to make sure that it should reject any bad inputs with oftentimes not very robust checking on what these bad inputs actually are. 24:31.530 --> 24:39.790 But from a security context, anywhere that you can touch something important from, also needs to be secured. 24:39.950 --> 24:54.990 Because if you can, you know, have a lower functional, lower functioning device, lower classification, lower DO1s, then you see a DAL classification device that can maybe in some way disrupt a higher level, more critical device. 24:54.990 --> 25:04.230 And this is something that you have to think about from the security perspective as an attacker, using this as a potential pivot to get onto a more critical system. 25:05.950 --> 25:18.270 And also any device or software that interacts with these components, whether in the flight or on the ground, all your ground maintenance software, is now needs to be considered essentially from a security level, the same as a flight device. 25:18.270 --> 25:30.210 Because these are things that are designed to be able to modify the behavior of these pieces of hardware that are responsible for directly controlling the flight of the aircraft. 25:30.670 --> 25:35.330 I think that's an important point of what we're defining here. 25:35.330 --> 25:42.190 Things that we consider flight devices includes the things on the ground that program the device. 25:42.250 --> 25:52.450 Because those are very critical to making sure that the correct and only the correct components are programmed. 25:53.690 --> 26:02.550 You know, one thing also, Tim talked about the different components, different level of components talking together on the same bus. 26:02.550 --> 26:12.750 One very common level A software item on recent aircraft is an operating system running on a particular device. 26:12.750 --> 26:30.530 There is a standard called RX-653, which defines ways for a partitioned operating system that's effectively like a virtual machine, can have multiple different severity levels running on the same component. 26:31.250 --> 26:37.050 So as we all know, in security though, virtual machine escapes are definitely a thing. 26:37.130 --> 26:49.550 So if there was an attacker who was able to get into a lower level component, you know that they would be able to, from there, pivot into the operating system itself, or a more critical component if they wanted to. 26:53.980 --> 26:55.580 So that's our devices. 26:56.240 --> 26:58.220 How do we go about doing this? 26:58.220 --> 27:00.600 Well, we've got a couple different things here. 27:02.800 --> 27:05.780 So there's adversarial testing. 27:07.060 --> 27:12.660 I choose the word adversarial testing because I don't want to say pentesting, because pentesting means different things to different people. 27:12.660 --> 27:19.500 This is the idea of testing the system as an attacker would. 27:19.500 --> 27:24.940 You're no longer just strictly checking against a specification. 27:25.040 --> 27:30.140 You're actually looking at it from, if I'm an attacker, how could I leverage this system to do something? 27:30.140 --> 27:33.400 How could I use this protocol to do something? 27:33.400 --> 27:41.600 All the things that, you know, security professionals that we do in our jobs, how do we, you know, doing these things to now an airplane? 27:43.180 --> 27:48.120 Another method is some sort of pre-flight software and configuration authentication. 27:48.840 --> 28:03.540 If before every flight there was a way to go and check that the system is actually running the software that you think is going to be running, actually has a cryptographically secure method of validating that the software that's running is the software that's supposed to be running, 28:03.540 --> 28:06.060 that your configuration is correct. 28:07.680 --> 28:28.320 Other methods could include like physically incompatible interfaces on flight systems to make sure that no flight system, you can't just plug your iPad into a critical flight system, that there's the interface on these flight systems, just, you know, they don't speak these commodity protocols like USB or Bluetooth or Wi-Fi. 28:28.320 --> 28:29.960 We'll talk about this a little bit later. 28:30.960 --> 28:33.940 We also need to talk about air gaps. 28:33.940 --> 28:54.620 I know anybody in ICS is definitely laughing a little bit right now, but on an airplane with a strictly controlled configuration, you know, air gaps could certainly be a part of the solution for making sure that you can't jump from, you know, the non-flight critical portion of the aircraft to the flight critical portion of the aircraft, 28:54.620 --> 28:57.740 at least as a passenger sitting in the plane. 29:00.480 --> 29:05.400 Now the adversarial testing, you know, review and test all interfaces for vulnerabilities. 29:05.400 --> 29:22.900 You know, you have to, you can't trust, just blindly trust the external inputs into the system, even if they should only be coming from a system that's also been tested in the same level and should only be producing correct outputs for you to consume, 29:22.900 --> 29:29.060 you still can't trust this because you can't always trust that the system hasn't been compromised in some way. 29:29.500 --> 29:34.780 I'd like to give an example from automotive for that. 29:34.780 --> 29:50.860 If you have one component that tells you the brake is pressed and you make sure that the thing that actually generates the signal saying the brake is pressed works perfectly, can't be cracked, the thing that interprets that signal works perfectly, can't be cracked, 29:50.860 --> 30:01.480 it's all well and good, but if you then have an entertainment system on the same bus and that sends a message saying the brake is pressed, well, now you can't trust your inputs, can you? 30:04.400 --> 30:07.620 Yeah, and testing your protocol stacks and milestones for vulnerability. 30:07.640 --> 30:17.520 I mean, we've gotten a little bit better, but there's been lots of vulnerabilities found in TCP IP stacks and other network stacks over the years. 30:18.300 --> 30:28.300 Reviewing the software and compile code for vulnerabilities, making sure you're doing static analysis on the code, not a perfect solution, but it does catch some things. 30:29.440 --> 30:37.800 Secure boot is, I think, a fairly critical part of making sure that we can actually trust the software running on the systems. 30:37.800 --> 30:55.700 Having a good, secure boot platform set up could go a very long way to preventing at least an attacker from modifying the operating system that should then be modifying the software that runs on this platform because it should be detected. 30:56.320 --> 30:59.120 And , of course, having multiple layers of protection. 30:59.620 --> 31:07.520 Defense in depth has always been one of the strongest things you can do for the security posture of basically anything. 31:09.120 --> 31:17.220 The topic of secure boot is one that could be talked about for a long time and different people have different definitions of what secure boot means. 31:18.460 --> 31:36.960 At a simple level right now, I think what we mean is just that there's a way that the hardware has the ability to use cryptographically secure methods to ensure that only authorized software and components are installed and operating on that device. 31:37.000 --> 31:44.060 And a way to store the keys that should be immutable. 31:45.220 --> 31:45.860 Right. 31:45.860 --> 32:01.860 And also, once somebody gets in and pulls apart the hardware that they are not able to go in and break out, break the secure boot for all of the devices. 32:01.940 --> 32:02.200 Right. 32:02.200 --> 32:10.280 Something that is, uses perhaps asymmetric cryptography methods and secure hashing to be used for device. 32:13.720 --> 32:17.980 So pre-flight software authentication, talked about this a little bit earlier. 32:17.980 --> 32:26.160 We want to make sure that the before takeoff that everything on the aircraft is 100% correct and secure and authentic. 32:27.880 --> 32:36.140 So this would be some way, some centralized way to query every single device and find out what software and configuration are running on them. 32:36.140 --> 32:46.160 This is already somewhat in existing, you know, before an aircraft flies, this is already somewhat what happens, right? 32:46.160 --> 32:50.120 We need to make sure that only the correct software is on each component. 32:50.120 --> 32:58.980 So people who fly aircraft will already have a list of different software versions that should be running on each component of the aircraft. 32:58.980 --> 33:03.320 So this isn't as outlandish as it sounds. 33:04.260 --> 33:07.940 You can use cryptographic and secure algorithms, no CRCs, no checksums. 33:07.940 --> 33:13.680 You should be using something like SHA-2, SHA-3, something better. 33:14.100 --> 33:22.800 And there should be also the protocol, the way the centralized device queries every single component, there should be a challenge response protocol here. 33:22.800 --> 33:29.160 The protocol should also be tested adversarially to make sure there is something that cannot be spoofed. 33:29.160 --> 33:31.520 We need to make sure we can prevent replay attacks. 33:31.520 --> 33:43.260 So if there is some malicious software, malicious component on a box, it should be incapable of falsifying the authenticity of that software. 33:43.260 --> 33:48.620 You can also validate the entire range of memory and flash on each device. 33:48.940 --> 33:52.680 You want to make sure that you can't set the length to zero. 33:52.680 --> 34:05.300 You want to make sure that you don't have the correct software and the correct configuration and put some sort of mystery component in the middle and that that gap just isn't checked because it wasn't thought to be important, right? 34:05.300 --> 34:07.900 You need to make sure that the entire range is validated. 34:14.800 --> 34:27.280 Yeah, physically incompatible interfaces, you know, we're seeing that like the flight crews, they have the iPad devices that will be there, their flight book that has the flight information. 34:27.900 --> 34:43.700 One of the ways to make sure to, one order to help prevent malicious software from being loaded onto these flight critical systems is to make sure that there are physically incompatible interfaces between the non-flight systems and the flight capable systems. 34:43.700 --> 34:59.180 So your flight cable systems shouldn't have USB, they shouldn't have Bluetooth, they shouldn't have Wi-Fi, they shouldn't have these standardized protocols that everything speaks, you know, specialized hardwired connections like the connections we have a picture of here, 34:59.180 --> 35:07.280 very common in aerospace, just make it a lot harder for the flight crew to just plug their iPad into a flight critical system. 35:08.240 --> 35:14.800 And if you can see on these connectors, some of the important parts of them is that they've actually got different keying. 35:14.800 --> 35:23.000 So there's usually a bunch of different, you know, a bunch of different pins so that you have all the necessary signals that you need for a particular connector. 35:23.000 --> 35:26.800 But then you, there's a lot of different varieties of keying. 35:26.800 --> 35:30.460 Some have five slots, some have four, different widths, different positions. 35:30.600 --> 35:35.820 And the whole idea is that you want to make sure that you cannot connect a component wrong. 35:35.820 --> 35:39.460 This is already what's done on an aircraft for connecting all the different flight components. 35:39.460 --> 35:45.940 And this is something that we say is necessary when connecting anything to a flight system. 35:50.040 --> 35:56.920 So air gaps, as Tim said, everybody who's in ICS is probably laughing when we had that out there before. 35:56.920 --> 36:00.160 But the whole point is that an aircraft doesn't change. 36:00.340 --> 36:04.460 If it changes, it changes because the design of the aircraft changes. 36:04.460 --> 36:10.740 It changes because there was an actual documented and, you know, tested reason for doing so. 36:11.100 --> 36:20.300 So designing the system, you should make sure that the flight systems and the non-flight systems cannot talk at all. 36:22.280 --> 36:24.400 They should be physically separate. 36:25.020 --> 36:27.900 We, as I said, virtual machine escapes are definitely a thing. 36:27.900 --> 36:29.500 You should not be running on the same box. 36:29.500 --> 36:32.020 They should not be able to even talk on the same bus. 36:33.300 --> 36:39.420 So anything that needs, if somebody, you don't want to have to test everything on an aircraft, right? 36:39.420 --> 36:49.160 You want to make sure you can, you want to try and trim what you need to test because testing is expensive. 36:49.440 --> 36:54.980 So something like an entertainment system, maybe somebody doesn't want to go about testing that. 36:54.980 --> 36:56.040 Well, that's okay. 36:56.520 --> 37:04.560 If you can make sure that that entertainment system can never ever talk to a flight system, which means no common buses. 37:04.600 --> 37:13.520 It means that the only thing on the aircraft connected to that entertainment system from the flight components is power. 37:13.840 --> 37:25.620 If you need somebody to, if the crew needs to like disconnect a component, they would need to be able to, you know, toggle the power to that device instead of actually sending a message to shut down. 37:33.550 --> 37:38.090 So some examples of what we've got here. 37:38.090 --> 37:46.690 We're going to go through some different categories, three different types of systems and talk about how we would apply these things to ensure that they're secure. 37:48.130 --> 37:49.030 Maintenance. 37:49.030 --> 37:56.190 In these cover, this is pretty much the, you know, all the different types of devices that you would have on an aircraft, right? 37:56.190 --> 38:01.630 Passenger accessible systems, things that passengers can get access to and so on. 38:04.980 --> 38:07.120 So maintenance devices. 38:07.520 --> 38:11.740 These are the things that program the different components when the aircraft is on the ground. 38:12.540 --> 38:24.060 They're usually a fancy laptop, maybe a robust laptop with some sort of waterproof case and special cables and extra interfaces to talk to the aircraft parts. 38:25.720 --> 38:29.460 These need to be adversarially tested. 38:29.460 --> 38:32.980 This is, should be unsurprising to hear by now. 38:33.280 --> 38:46.300 Communications with the different flight devices should require full authentication and these devices should also have a plan and method to periodically validate that the device itself has not been compromised. 38:46.420 --> 38:52.880 As I said, they're typically a regular laptop or some sort of PC type device. 38:52.880 --> 39:03.320 So any of the standard ways to secure a PC, you know, a laptop should be used on these devices to make auditing. 39:03.440 --> 39:10.560 They should have auditing on, they should have all the different security protections in place. 39:11.420 --> 39:18.600 Programming other devices as well, as typically it can happen to, there is an ERIN standard for this as well, although it's optional. 39:18.600 --> 39:20.300 Not every device implements it. 39:20.300 --> 39:29.360 It's called ERIN 615 for data loading and that can happen over multiple types of device buses such as ERIN 429. 39:30.140 --> 39:33.320 These devices will then usually talk over that. 39:33.320 --> 39:34.780 It's kind of a double-edged sword. 39:34.780 --> 39:38.400 On one hand, it means you've got a standard way of doing things. 39:38.400 --> 39:55.760 On the other hand, it means that if somebody implements ERIN 429, you potentially be able to go up and program with an unauthenticated device, which is why communication with the flight device should require full back and forth challenge response authentication on both ends. 39:55.940 --> 40:02.620 The device should make sure that the device programming it is who it says it is and vice versa. 40:03.380 --> 40:06.180 Full mutual authentication. 40:06.180 --> 40:07.800 That's the term. 40:11.040 --> 40:33.100 So passenger accessible systems should either be incapable of connecting to aircraft systems, not physically connected in any way, not physically sharing any piece of hardware, ideally not even speaking the same sort of protocols so they couldn't even accidentally be connected together. 40:33.100 --> 40:37.360 You can't just plug USB into ERIN 429 and have it work. 40:37.980 --> 40:50.300 Or they need to be same as everything else adversarial tested and not have external connectivity that a normal passenger would be able to just plug into and use. 40:50.420 --> 40:54.420 If you have a USB for charging, it should only be for charging. 40:54.420 --> 40:55.820 Only the data lines should be connected. 40:55.820 --> 41:02.500 It shouldn't have any of the... you should be capable of passing data back and forth. 41:05.320 --> 41:21.660 The only case where there's an exception then is if this isn't a system, if the entertainment system is incapable of being connected to critical flight systems or to flight systems, then you could have a USB audio interface on it. 41:21.660 --> 41:22.480 Yes. 41:22.740 --> 41:26.960 But that's the only case where that would be allowed. 41:26.960 --> 41:30.220 You would need to make sure that this device cannot talk to anything else. 41:30.220 --> 41:50.200 And the whole goal here is to make sure that something can't be done, something cannot accidentally or through somebody dropping a bad cable somewhere near the airport, have somebody connect something that shouldn't be connected to the flight systems. 41:50.200 --> 41:51.280 That's the whole goal here. 41:51.280 --> 42:07.200 If somebody is going to try and attack an aircraft during that small, that limited window of the flight itself, we want to make sure that it is incredibly obvious that they're doing something that they shouldn't be doing. 42:07.360 --> 42:11.020 So just plugging the USB in is very benign. 42:11.100 --> 42:25.320 But if they're starting to rip up panels and trying to find the 429 bus somewhere down there, well, that should hopefully be obvious to some of the other passengers or the crew and corrective measures could take place. 42:26.740 --> 42:28.120 But that's the whole goal here. 42:28.120 --> 42:35.540 We want to make sure that it can't be done accidentally or on purpose without it being obvious. 42:39.500 --> 42:45.360 So the flight systems, the flight systems themselves, we've talked about these quite a bit already. 42:45.460 --> 42:47.760 These need to be adversarially tested, of course. 42:47.760 --> 42:59.980 We need to make sure that there's multiple levels of... there's multiple layers of protection in the way for anybody who is trying to attack a system that they would need to get through. 43:00.260 --> 43:01.920 No consumer interfaces. 43:02.200 --> 43:12.160 So all those flight systems, you need to make sure that you do not have the... you don't have the... you know, there's no USB in there. 43:12.160 --> 43:13.840 There's no Wi-Fi in there. 43:13.840 --> 43:16.920 So iPads as a flight bag are a thing now. 43:17.580 --> 43:22.360 And obviously, there's an appeal in terms of how easy it is to update. 43:22.520 --> 43:26.380 You don't have to carry around stacks and stacks of paper. 43:26.860 --> 43:29.360 There's... it's an easy way to store a lot of things. 43:30.960 --> 43:38.780 But that means you've now got a device which is in the cockpit, which is considered a flight critical system, which is a consumer device. 43:39.460 --> 43:42.740 And that gives me some concerns. 43:42.740 --> 43:48.320 So I think there needs to be some thought on how to secure that type of system. 43:48.440 --> 43:50.960 Maybe it just needs to be not an iPad. 43:50.960 --> 43:52.840 Maybe it can be a special purpose device. 43:52.840 --> 43:54.880 There's plenty of things out there with LCD. 43:54.880 --> 43:57.520 They can store maps and have a program in them. 43:59.320 --> 44:00.700 No consumer interfaces. 44:00.700 --> 44:01.980 Yeah, so no USB. 44:01.980 --> 44:03.840 You wouldn't be able to connect this. 44:04.780 --> 44:09.980 You don't want to have somebody accidentally plug in a USB as you're not supposed to, right? 44:16.170 --> 44:20.970 So just as a quick summary here. 44:23.550 --> 44:25.530 Again, our goals. 44:26.450 --> 44:30.710 These are the things that we want to achieve. 44:30.770 --> 44:33.710 And I think we have for what we've put in place. 44:34.150 --> 44:37.850 Making sure we still have to assume, again, that's up front. 44:37.850 --> 44:40.090 An attacker has everything, knows everything. 44:41.130 --> 44:46.310 We've talked about providing a way to make sure that the systems can be validated to be correct. 44:47.330 --> 44:53.430 That the software and configurations on the different components are correct when the aircraft, before the aircraft takes off. 44:53.430 --> 44:56.510 We want to limit that potential attack window. 44:58.730 --> 45:13.650 We've talked about the ways we can prevent accidental transmission of something malicious to the physical air gaps, physical disconnects, physical incompatible interfaces. 45:14.810 --> 45:18.870 And then, again, if this is all, the goal is to make multiple barriers there. 45:19.650 --> 45:22.950 Multiple barriers there an attacker would need to get through. 45:27.200 --> 45:30.460 Yeah, and then two device categories. 45:30.460 --> 45:33.900 There's stuff that can affect flight and stuff that can't affect flight. 45:34.800 --> 45:42.180 And can't affect flight does, in this case, mean physical, full physical isolation of anything flight critical. 45:46.200 --> 45:46.780 Methods. 45:46.780 --> 45:48.320 We've talked about these at length. 45:48.320 --> 45:52.860 Adversarial testing, I believe, is a big key part of this. 45:53.400 --> 45:57.320 One thing I guess we didn't really talk about is kind of design standards. 45:58.360 --> 46:00.700 It's something that could be addressed as well. 46:01.080 --> 46:16.840 Making sure that the software as it's developed complies with the different best practice recommendation of how to develop secure software in terms of functions that are allowed and such. 46:17.180 --> 46:18.820 That's another potential method. 46:18.820 --> 46:23.740 We are more looking at the fitting things on top of what was there already. 46:27.050 --> 46:30.510 But we still do have a few problems that we need to solve. 46:30.830 --> 46:34.150 We're not going to try and pretend that we solved everything here. 46:34.150 --> 46:39.970 We'd like to think that we solved a significant part of aviation cybersecurity just in this talk. 46:40.830 --> 46:45.170 But there's a few things that we need to think about going forward. 46:45.650 --> 46:47.930 Supply chain security is still a concern. 46:49.790 --> 46:52.150 Obviously, as I said, anything can be hacked. 46:52.150 --> 46:57.750 As the devices are sitting in storage, an attacker could go in and modify them. 46:57.750 --> 47:03.490 They've got plenty of time to go in and modify them, figure out how they work. 47:03.630 --> 47:06.370 Either modify the software or just physically. 47:06.370 --> 47:08.310 Physical modifications to the hardware. 47:08.990 --> 47:14.690 And how to make sure that that doesn't happen or can't happen is a challenge. 47:16.150 --> 47:23.470 RF communication is also another area that we can't really address. 47:23.470 --> 47:26.090 The airplane has a fair bit of RF communication. 47:26.090 --> 47:32.550 It has radio, ADS-B, weather, etc. 47:32.550 --> 47:39.590 This is also something that wasn't addressed by what we've presented here in this talk. 47:40.850 --> 47:45.730 The flight crew, the pilot's training is a significant part of that. 47:45.730 --> 47:55.870 If there's issues with communication between the aircraft and ground, that's something where training can kick in and deal with the situation. 47:55.930 --> 48:02.650 But it is still something that would improve matters if there was a way to secure the communications. 48:05.750 --> 48:14.150 Things that we might also want to think about in the future are how often, how much change would require something to be retested, more adversarial testing. 48:14.150 --> 48:30.050 What level of change, where different amounts of change are considered to be minor fixes, and they don't have to require a complete redesign of the system. 48:30.410 --> 48:35.430 But some level of change does require a complete redesign and retesting the system. 48:35.430 --> 48:39.390 So that's something that would need to be looked at in the future. 48:42.200 --> 48:44.740 And then there's also the maintenance devices themselves. 48:44.740 --> 48:50.240 We talked about how maintenance devices are used to program all the different components on an aircraft. 48:50.240 --> 48:55.900 This means that would be used to program both flight systems and these air-gapped non-flight systems. 48:56.380 --> 49:00.820 So maybe those need to have a slightly different category. 49:00.820 --> 49:06.700 You could argue, you can put together a committee meeting and argue about lots of this stuff for a while if you want to. 49:06.760 --> 49:15.920 But I think that what we've given here is a fairly complete approach to address cyber security. 49:16.940 --> 49:18.720 Any questions? 49:18.720 --> 49:21.020 We'll be in the discord for any questions.