Category: Encrypted firmware reversing

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Information Security Stack Exchange is a question and answer site for information security professionals. It only takes a minute to sign up. When working with Internet of Things devices, is it recommend to obfuscate or encrypt firmware images pushed to clients?

This to make reverse engineering harder. Some people argue that code which is open source can be audited by many and therefor contains little bugs. On the other hand, attackers have the same easy access and also look for these same vulnerabilities. There is definitely a tradeoff here which is not correctly described in previous answers.

It is true that a system should be designed to be secure even if you know how it works. This doesn't mean that this is always the case AND the implementation is flawless. Take a look at web app security: Why do we need security headers to protect us against XSS and CSRF attacks if there are no vulnerabilities in the web application? Additional security measures can be taken by trying to hide the code through encryption and obfuscation.

Allowing public review on you source code can help reduce the number of bugs. However, if you are a small company where the public has little incentive to freely audit your code, there is no benefit from publishing your code as nobody will look at it with good intentions.

However, it becomes much easier for attackers to discover vulnerabilities. We are not talking about the newest iOS version which every security researcher is trying to crack. In this case we aren't even talking about open sourcing the code for public review. We are talking about encrypting the firmware in transit. Security researchers are not likely going to buy your device to obtain the code to discover and publish vulnerabilities.

Therefor the chance of having the good guys finding the vulnerabilities VS the bad guys finding them decreases.

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I have a radical suggestion: do the exact opposite. Make your firmware binaries publicly available and downloadable, freely accessible to anyone who wants them. Add a page on your site with details on how to contact you about security issues. Engage with the security community to improve the security of your product. Doubtful it would be beneficial.

It is by far a better option to push it open-source than closed source.

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It might seem silly and even controversial at first, but opening up a project to the public has plenty of benefits. While there are people with malicious intents, there are also people wanting to help and make the internet a better place.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Reverse Engineering Stack Exchange is a question and answer site for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation.

It only takes a minute to sign up. I think the firmware might be encrypted; because of the two certificates in DER format at the top of the file but I am unsure about this. I tried using dd to pull out the jpeg data but it seems like that might be a false positive. Looking at some of the strings in the binary; there seems to be some 3rd party AI vision software; broadcom modem, zhouyanhui compile:[gcc 4. Sign up to join this community. The best answers are voted up and rise to the top.

Home Questions Tags Users Unanswered. Ask Question. Asked 2 months ago. Active 2 months ago. Viewed 94 times. My question; what are some other steps that I could take to get further into this firmware? Does binwalk -eM produce additional output?

It really depends what your objective is. Things to look at include strings -t x firmware. You can also look at each of the interesting things that binwalk found to see if they are real or false-positives.

encrypted firmware reversing

Active Oldest Votes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Featured on Meta. Feedback on Q2 Community Roadmap. Related 6. Hot Network Questions. Question feed.Perhaps you read our multiple previous blog posts on router vulnerability research and decided to give it a try.

You downloaded the firmware of your home router from the vender website, threw it in binwalk so that you could just emulate it in QEMU. Then the following screen appeared….

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Fig 1. In general, each non-binwalk friendly firmware will be an adventure of its own, making it impossible to provide a step-by-step guide for defeating all types of encrypted firmware. This blog aims to go through a few common scenarios and provide a general guide to dealing with this type of firmware. Look back and look around: Three common scenarios of encrypted firmware releases.

The simplest method to decrypt the firmware is to look for the decryption routine within the firmware. If the router can decrypt the new firmware for updates, the decryption routine must be located in the old firmware image somewhere. If you encounter an encrypted firmware, go to the vendor website and look for archived versions of the firmware, download all old versions and start poking around.

The device firmware was not encrypted nor did it contain any decryption routine when it was factory released. A decryption routine is shipped along with an unencrypted version of the firmware in a newer version v1.

Subsequent firmware releases are encrypted. In this scenario, we can obtain the decryption routine from firmware v1. The device firmware is encrypted in the original release.

Reversing an Oppo ozip encryption key from encrypted firmware

The vendor decided to change the encryption scheme and release an unencrypted transition version v1. Similar to scenario 1, we can obtain the decryption routine from v1. Reading the release notes of the firmware releases could be helpful in identifying the unencrypted transition version. The release notes will usually direct the user to upgrade to an intermediate version before upgrading to the latest version. The intermediate version is very likely to be the unencrypted transition firmware.

However, the vendor decided to change the encryption scheme, and release an unencrypted transition version which contains the new decryption routine.

In this case, there is no easy method to obtain the decryption routine. One route is to purchase a device and extract the unencrypted firmware from the hardware directly.Anything that can help us understand the system or may come in handy later on. Please check out the legal disclaimer in case I come across anything sensitive. I tried to contact TalkTalk, but their security staff is nowhere to be seen. We find multiple random pieces of data scattered across the boot sequence.

Hacking/Reverse Engineering a PRIVATE api

Intel on how the external flash memory is structured will be very useful when we get to extracting it. The Ralink IC in this router runs a Linux kernel to control memory and parallel processes, keep overall control of the system, etc. BusyBox is a single binary containing reduced versions of common unix commands, both for development convenience and -most importantly- to save memory. From ls and cd to topSystem V init scripts and pipes, it allows us to use the Ralink IC somewhat like your regular Linux box.

One of the utilities the BusyBox binary includes is the shell itself, which has access to the rest of the commands:. The top command will help us identify which processes are consuming the most resources. This can be an extremely good indicator of whether some processes are important or not. They could be RSA private keys used for mutually-authenticated TLS connections with a server, variables buried in a file to be loaded by an application, etc.

By accessing 1 single device via hardware you may obtain the keys that will help you eavesdrop encrypted connections, attack servers, end users or other devices in the fleet.

encrypted firmware reversing

With so many different files everywhere it can be quite time consuming to go through all the info without the right tools. Once we have as many files as possible in our computer we can check some things very quick.

What about searching the word password in all files? The credentials we can see are either in plain text or encoded in base Of course, encoding is worthless for data protection:. That is the current WiFi password set in the router. It leads us to 2 VERY interesting files. The most interesting one -besides shell - is debug. Not even encoded this time.

The rest of the ATP commands are pretty useless: clear screen, help menu, save to flash and exit.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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Reverse Engineering Stack Exchange is a question and answer site for researchers and developers who explore the principles of a system through analysis of its structure, function, and operation. It only takes a minute to sign up. I am by no means a hardware or software expert. But I've got a bit of a dilemma.

MindShaRE: Dealing with encrypted router firmware

I have on my hands an "encrypted" firmware image. I say that with air quotes because I'm not sure if it's encrypted, obfuscated, or whatever. It's an old firmware file that was written to a temporary firmware memory on a device and then executed through a bootloader of some kind.

People before me have decrypted the same file; however that was about three years ago and the user who posted the decrypted file has dissappeared, along with the file. I really need the decrytped file, as well as the ability to re-encrypt it once I change some code and have it still run on the device once I've edited it. According to the user who decrypted it originally:. There can be multiple files, encryption is optional, metadata is optional.

Where should I start with this? I tried running a few of the first tools that come up in a google search and they lead me to dead ends. Basically I'd like something that doesn't require me to have a degree in CS to understand.

Things would be so much easier if the user who figured out how to decrypt this originally had not fallen off the face of the earth, but we aren't so lucky.

Practical Reverse Engineering Part 2 - Scouting the Firmware

Here's a link to the original file if you want to look. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.

Decrypting Firmware File Ask Question. Asked 3 years, 10 months ago. Active 3 years, 10 months ago. Viewed 1k times. According to the user who decrypted it originally: "The format is pretty complex, the cryptography is simple.

Patrick Patrick 11 4 4 bronze badges. Can you show us the plaintext? Yes please. What device is the firmware for? A programming tool for old Motorola radios.Start your free trial. The article will explore various strategies for reversing firmware, with some examples. Finally, some best practices are mentioned. Embedded systems are everywhere, in mobiles, cameras, TVs, smart cards, and other automated devices.

They have become an integral part of our lives and have made it comfortable and easy. But how do these embedded devices work? Firmware is basically a binary file installed on customized operating systems such as Unix or Windows and very small in size. It is specifically designed and developed to perform some predetermined set of functions. The introduction and architecture of firmware is beyond the scope and context of this article.

We are more interested here in analyzing firmware from a security standpoint. After unpacking the firmware we may find the following: bootloaders, kernels, filesystem images, user apps, and web servers.

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We need to extract the filesystem images in order to analyze them. It comes as a part of a BT5 installation by default. Binwalk is basically a tool to examine binary files. It searches for certain strings or patterns and gives the result; however, analysis needs to be done to ascertain the correctness of the results, as it may throw a lot of false positives.

It lists the starting address of a certain section, size, and encryption types, etc. A sample:. We need to unpack the archives to examine further, which may give us information about bootloaders, kernels, web servers, filesystems, etc. Unfortunately, no headers are identified. The reason I wanted to show the above examples on a simple firmware file is that sometimes there may not be any leads while doing analysis.

In the reconnaissance phase it may fail; however, the key takeaway was that the above file was not encrypted, which may be a security issue. This can be downloaded from the DLink website.

It may give us some clues. Unfortunately, we are not able to get the boot loader information due to some error. Binwalk provides us with some interesting information. We need to be careful about false positives. All of these indicate that it is a valid result. The information about encryption seems to be a false positive, as we already saw that we were able to read the strings in clear text.

The filesystem SquashFS seems to be valid, since its size is well below the actual file size and the created date is in the past.

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This can be downloaded from:. Here are the contents of the passwd file:.As a start, in order to understand what we need, take a look at my repo implementing the ozip decrypter in python 3.

The data to be decrypted starts at the offset 0x and is usually encrypted using a simple aes with mode ECB and a block size of 0x bytes.

So, in order to understand where those ozip files are decrypted, there are usually two types of suspects where we can search for. So, enable the adb debugging on your target device, then run.

Second one: All the device related stuff we find on the internet seems to be encrypted. So nothing to see here, huh? So I searched on the internet for a full firmware package. Entropy is our best friend and obviously we are lucky and only the first section seems to be encrypted. So here we are, looking with our favorite hexeditor at that file, we finally see some sort of partition structure.

encrypted firmware reversing

Thus it allows us to search for a possible partition start and thus might help to find the vendor partition which we need.

Over there I wrote a script for it yeah bloody dirty hack, but who cares :. So we finally have our crafted vendor. Ok, obviously I missed something, but the layout looks like ext4 but with pagesize of instead ofstill kind of weird. Maybe another researcher has an idea and leaves a comment? We also assume the image was just build and never used in real life, so we can assume all data is in sequential order and not mixed up due to the way ext4 normally works with its nodes.

Using that belief, we first search for the bytepattern in our crafted vendor. I expected that, as we should have two libraries in the system, on for 32bit and one for 64bit.

So we only need to find the end of the binary. And at offset 0x2E starting from the ELF structure we see the size of a section header is 0x28 bytes and at offset 0x30 we see there are 0x1B sections in total. So we extract 0x6B3EC bytes starting from offset 0x25B of our vendor. Once you got it, fire up ghidra. If being asked for analysing the file first, do so. Well done mate, it looks like a valid arm binary :.

You will see that there is one hit in the Exports table. Doubleclick it so that it is shown in the Listing window. The latter is the key context, but as we are interested in finding the correct aes key, we choose the first parameter to be interesting. I feedback. Let me know what you think of this article on twitter viperbjk or leave a comment below!

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