Security Hacks

1491 Articles

A Kill Cord To End Laptop Skulduggery

January 21, 2020 by 60 Comments

In our community it is common for ancient laptops to be used way beyond their usual service life, held together by stickers and lovingly upgraded to their maximum capabilities. We hope it’s unusual for such a venerable machine to be stolen, but it seems that grab-and-run thefts are very much a thing for owners of much shinier hardware. [Michael Altfield] has a solution to this problem, in the form of a kill cord that when broken by the crook making off with the loot, triggers a set of scripts that can wipe the device or otherwise make it useless.

Hardware-wise it’s simple enough, a USB magnetic breakaway adapter and a USB extension cable to a drive clipped to the laptop owner’s belt. On the software side it’s as straightforward as a udev rule to launch the disaster script of your choice. Perhaps you could link it to something like a glitter bomb and fart spray. But we can’t help worrying that it might be too easy to get up and accidentally detach yourself from the laptop, making it deploy whatever anti-theft measure you’d installed in error. If this goes some way to reducing theft though, it has to be worth a second look.

Thanks [bluewraith] for the tip.

Building A Better BitTorrent Client In Go

January 18, 2020 by 25 Comments

When it comes to peer-to-peer file sharing protocols, BitTorrent is probably one of the best known. It requires a client implementing the program and a tracker to list files available to transfer and to find peer users to transfer those files. Developed in 2001, BitTorrent has since acquired more than a quarter billion users according to some estimates.

While most users choose to use existing clients, [Jesse Li] wanted to build one from scratch in Go, a programming language commonly used for its built-in concurrency features and simplicity compared to C.

Client-server versus peer-to-peer architecture
Client-server versus peer-to-peer architecture

The first step for a client is finding peers to download files from. Trackers, web servers running over HTTP, serve as centralized locations for introducing peers to one another. Due to the centralization, the servers are at risk of being discovered and shut down if they facilitate illegal content exchange. Thus, making peer discovery a distributed process is a necessity for preventing trackers from following in the footsteps of the now-defunct TorrentSpy, Popcorn Time, and KickassTorrents.

The client starts off by reading a .torrent file, which describes the contents of the desired file and how to connect to a tracker. The information in the file includes the URL of the tracker, the creation time, and SHA-1 hashes of each piece, or a chunk of the file. One file can be made up of thousands of pieces – the client will need to download the pieces from peers, check the hashes against the torrent file, and finally assemble the pieces together to finally retrieve the file. For the implementation, [Jesse] chose to keep the structures in the Go program reasonably flat, separating application structs from serialization structs. Pieces are also separated into slices of hashes to more easily access individual hashes.

The bitfield explained as a coffee shop loyalty card.
The bitfield explained as a coffee shop loyalty card.

Next, a GET request to an `announce` URL in the torrent file announces the presence of the client to peers and retrieves a response from the tracker with the list of peers. To start downloading pieces, the client starts a TCP connection with a peer, completes a two-way BitTorrent handshake, and exchanges messages to download pieces.

One interesting data structure exchanged in the messages is a bitfield, which acts as a byte array that checks which pieces a peer has. Bits are flipped when their respective piece’s status changes, acting somewhat like a loyalty card with stamps.

While talking to one peer may be straightforward, managing the concurrency of talking to multiple peers at once requires solving a classically Hard problem. [Jesse] implements this in Go by using channels as thread-safe queues, setting up two channels to assign work and collect downloaded pieces. Requests are later pipelined to increase throughput since network round-trips are expensive and sending blocks individually inefficient.

The full implementation is available on GitHub, and is easy enough to use as an alternative client or as a walkthrough if you’d prefer to build your own.

This Week In Security: Windows 10 Apocalypse, Paypal Problems, And Cablehaunt

January 17, 2020 by 18 Comments

Nicely timed to drop on the final day of Windows 7 support, Windows 10 received a fix to an extremely serious flaw in crypt32.dll. This flaw was reported by the good guys at the NSA. (We know it was the good guys, because they reported it rather than used it to spy on us.) It’s really bad. If you’re running Windows 10, go grab the update now. OK, you’re updated? Good, let’s talk about it now.

The flaw applies to X.509 keys that use elliptic curve cryptography. We’ve discussed ECC in the past, but let’s review. Public key encryption is based on the idea that some calculations are very easy to perform and verify, but extremely difficult to calculate the reverse operation.

The historic calculation is multiplying large primes, as it’s unreasonably difficult to factorize that result by a conventional computer. A true quantum computer with enough qubits will theoretically be able to factorize those numbers much quicker than a classical computer, so the crypto community has been searching for a replacement for years. The elliptic curve is the solution that has become the most popular. An agreed-upon curve and initial vector are all that is needed to perform the ECC calculation.

There are potential weaknesses in ECC. One such weakness is that not all curves are created equal. A well constructed curve results in good cryptography, but there are weak curves that result in breakable encryption.

With that foundation laid, the flaw itself is relatively easy to understand. An X.509 certificate can define its own curve. The Windows 10 implementation doesn’t properly check the curve that is specified. A malicious curve is specified that is similar to the expected curve — similar enough that the checks in crypt32 don’t catch it. Continue reading “This Week In Security: Windows 10 Apocalypse, Paypal Problems, And Cablehaunt” →

Take Security Up A Notch By Adding LEDs

January 12, 2020 by 14 Comments

All computers are vulnerable to attacks by viruses or black hats, but there are lots of steps that can be taken to reduce risk. At the extreme end of the spectrum is having an “air-gapped” computer that doesn’t connect to a network at all, but this isn’t a guarantee that it won’t get attacked. Even transferring files to the computer with a USB drive can be risky under certain circumstances, but thanks to some LED lights that [Robert Fisk] has on his drive, this attack vector can at least be monitored.

Using a USB drive with a single LED that illuminates during a read OR write operation is fairly common, but since it’s possible to transfer malware unknowingly via USB drives, one that has a separate LED specifically for writing operations will help alert a user to any write operations that might be trying to fly under the radar. A recent article by [Bruce Schneier] pointed out this flaw in USB drives, and [Robert] was up to the challenge. His build returns more control to the user by showing them when their drive is accessed and in what way, which can also be used to discover unique quirks of one’s chosen operating system.

[Robert] is pretty familiar with USB drives and their ups and downs as well. A few years ago he built a USB firewall that was able to decrease the likelihood of BadUSB-type attacks. Be careful going down the rabbit hole of device security, though, or you will start seeing potential attacks hidden almost everywhere.

This Week In Security: Camera Feeds, Python 2, FPGAs

January 10, 2020 by 6 Comments

Networked cameras keep making the news, and not in the best of ways. First it was compromised Ring accounts used for creepy pranks, and now it’s Xiaomi’s stale cache sending camera images to strangers! It’s not hard to imagine how such a flaw could happen: Xiaomi does some video feed transcoding in order to integrate with Google’s Hub service. When a transcoding slot is re-purposed from one camera to another, the old data stays in the buffer until it is replaced by the new camera’s feed. The root cause is probably the same as the random images shown when starting some 3D games.

Python is Dead, Long Live Python

Python 2 has finally reached End of Life. While there are many repercussions to this change, the security considerations are important too. The Python 2 environment will no longer receive updates, even if a severe security vulnerability is found. How often is a security vulnerability found in a language? Perhaps not very often, but the impact can be far-reaching. Let’s take, for instance, this 2016 bug in zipimport. It failed to sanitize the header of a ZIP file being processed, causing all the problems one would expect.

It is quite possible that because of the continued popularity and usage of Python2, a third party will step in and take over maintenance of the language, essentially forking Python. Unless such an event happens, it’s definitely time to migrate away from Python2.
Continue reading “This Week In Security: Camera Feeds, Python 2, FPGAs” →

Possible Spyware On Samsung Phones

January 9, 2020 by 118 Comments

[Editor’s note: There’s an ongoing back-and-forth about this “spyware” right now. We haven’t personally looked into it on any phones, and decoded Wireshark caps of what the cleaner software sends home seem to be lacking — it could be innocuous. We’re leaving our original text as-run below, but you might want to take this with a grain of salt until further evidence comes out. Or keep us all up to date in the comments. But be wary of jumping to quick conclusions.]

Samsung may have the highest-end options for hardware if you want an Android smartphone, but that hasn’t stopped them from making some questionable decisions on the software they sometimes load on it. Often these phones come with “default” apps that can’t be removed through ordinary means, or can’t even be disabled, and the latest discovery related to pre-loaded software on Samsung phones seems to be of a pretty major security vulnerability.

This software in question is a “storage cleaner” in the “Device Care” section of the phone, which is supposed to handle file optimization and deletion. This particular application is made by a Chinese company called Qihoo 360 and can’t be removed from the phone without using ADB or having root. The company is known for exceptionally bad practices concerning virus scanning, and the software has been accused of sending all information about files on the phone to servers in China, which could then turn all of the data it has over to the Chinese government. This was all discovered through the use of packet capture and osint, which are discussed in the post.

These revelations came about recently on Reddit from [kchaxcer] who made the original claims. It seems to be fairly legitimate at this point as well, and another user named [GeorgePB] was able to provide a temporary solution/workaround in the comments on the original post. It’s an interesting problem that probably shouldn’t exist on any phone, let alone a flagship phone competing with various iPhones, but it does highlight some security concerns we should all have with our daily use devices when we can’t control the software on the hardware that we supposedly own. There are some alternatives though if you are interested in open-source phones.

Thanks to [kickaxe] for the tip!

Photo from Pang Kakit [CC BY-SA 3.0 DE (https://creativecommons.org/licenses/by-sa/3.0/de/deed.en)]

This Week In Security: ToTok, Edgium, Chrome Checks Your Passwords, And More

January 3, 2020 by 11 Comments

Merry Christmas and happy New Year! After a week off, we have quite a few stories to cover, starting with an unexpected Christmas gift from Apple. Apple has run an invitation-only bug bounty program for years, but it only covered iOS, and the maximum payout topped out at $200K. The new program is open to the public, covers the entire Apple product lineup, and has a maximum payout of $1.5 million. Go forth and find vulnerabilities, and make sure to let us know what you find.

ToTok

The United Arab Emirates had an odd policy regarding VoIP communications. At least on mobile networks, it seems that all VoIP calls are blocked — unless you’re using a particular app: ToTok. Does that sound odd? Is your “Security Spider Sense” tingling? It probably should. The New York Times covered ToTok, claiming it was actually a tool for spying on citizens.

While that coverage is interesting, more meat can be found in [Patrick Wardle]’s research on the app. What’s most notable, however, is the distinct lack of evidence found in the app itself. Sure, ToTok can read your files, uploads your contact book to a centralized server, and tries to send the device’s GPS coordinates. This really isn’t too far removed from what other apps already do, all in the name of convenience.

It seems that ToTok lacks end-to-end encryption, which means that calls could be easily decrypted by whoever is behind the app. The lack of malicious code in the app itself makes it difficult to emphatically call it a spy tool, but it’s hard to imagine a better way to capture VoIP calls. Since those articles ran, ToTok has been removed from both the Apple and Google’s app stores.

SMS Keys to the Kingdom

Have you noticed how many services treat your mobile number as a positive form of authentication? Need a password reset? Just type in the six-digit code sent in a text. Prove it’s you? We sent you a text. [Joakim Bech] discovered a weakness that takes this a step further: all he needs is access to a single SMS message, and he can control your burglar alarm from anywhere. Well, at least if you have a security system from Alert Alarm in Sweden.

The control messages are sent over SMS, making them fairly accessible to an attacker. AES encryption is used for encryption, but a series of errors seriously reduces the effectiveness of that encryption. The first being the key. To build the 128-bit encryption key, the app takes the user’s four-digit PIN, and pads it with zeros, so it’s essentially a 13 bit encryption key. Even worse, there is no message authentication built in to the system at all. An attacker with a single captured SMS message can brute force the user’s PIN, modify the message, and easily send spoofed commands that are treated as valid.

Microsoft Chrome

You may have seen the news, Microsoft is giving up on their Edge browser code, and will soon begin shipping a Chromium based Edge. While that has been a source of entertainment all on its own, some have already begun taking advantage of the new bug bounty program for Chromium Edge (Edgium?). It’s an odd bounty program, in that Microsoft has no interest in paying for bugs found in Google’s code. As a result, only bugs in the Edge-exclusive features qualify for payout from Microsoft.

As [Abdulrahman Al-Qabandi] puts it, that’s a very small attack surface. Even so, he managed to find a vulnerability that qualified, and it’s unique. One of the additions Microsoft has made to Edgium is a custom new tab page. Similar to other browsers, that new tab page shows the user their most visited websites. The problem is that the site’s title is shown on that page, but without any sanity checking. If your site’s title field happens to include Javascript, that too is injected into the new tab page.

The full exploit has a few extra steps, but the essence is that once a website makes it to the new tab page, it can take over that page, and maybe even escape the browser sandbox.

Chrome Password Checkup

This story is a bit older, but really grabbed my attention. Google has rolled a feature out in Chrome that automatically compares your saved passwords to past data breaches. How does that work without being a security nightmare? It’s clever. A three-byte hash of each username is sent to Google, and compared to the hashes of the compromised accounts. A encrypted database of potential matches is sent to your machine. Your saved passwords, already encrypted with your key, is encrypted a second time with a Google key, and sent back along with the database of possible matches, also encrypted with the same Google key. The clever bit is that once your machine decrypts your database, it now has two sets of credentials, both encrypted with the same Google key. Since this encryption is deterministic, the encrypted data can be compared without decryption. In the end, your passwords aren’t exposed to Google, and Google hasn’t given away their data set either.

The Password Queue

Password changes are a pain, but not usually this much of a pain. A university in Germany suffered a severe malware infection, and took the precaution of resetting the passwords for every student’s account. Their solution for bootstrapping those password changes? The students had to come to the office in person with a valid ID to receive their new passwords. The school cited German legal requirements as a primary cause of the odd solution. Still, you can’t beat that for a secure delivery method.