Robert Graham

Author Archives: Robert Graham

Mini pwning with GL-iNet AR150

Seven years ago, before the $35 Raspberry Pi, hackers used commercial WiFi routers for their projects. They'd replace the stock firmware with Linux. The $22 TP-Link WR703N was extremely popular for these projects, being half the price and half the size of the Raspberry Pi.


Unfortunately, these devices had extraordinarily limited memory (16-megabytes) and even more limited storage (4-megabyte). That's megabytes -- the typical size of an SD card in an RPi is a thousand times larger.

I'm interested in that device for the simple reason that it has a big-endian CPU.

All these IoT-style devices these days run ARM and MIPS processors, with a smattering of others like x86, PowerPC, ARC, and AVR32. ARM and MIPS CPUs can run in either mode, big-endian or little-endian. Linux can be compiled for either mode. Little-endian is by far the most popular mode, because of Intel's popularity. Code developed on little-endian computers sometimes has subtle bugs when recompiled for big-endian, so it's best just to maintain the same byte-order as Intel. On the other hand, popular file-formats and crypto-algorithms use big-endian, so there's some efficiency to be gained with going with that choice.

I'd like to have a big-endian computer around to Continue reading

California’s bad IoT law

California has passed an IoT security bill, awaiting the governor's signature/veto. It’s a typically bad bill based on a superficial understanding of cybersecurity/hacking that will do little improve security, while doing a lot to impose costs and harm innovation.


It’s based on the misconception of adding security features. It’s like dieting, where people insist you should eat more kale, which does little to address the problem you are pigging out on potato chips. The key to dieting is not eating more but eating less. The same is true of cybersecurity, where the point is not to add “security features” but to remove “insecure features”. For IoT devices, that means removing listening ports and cross-site/injection issues in web management. Adding features is typical “magic pill” or “silver bullet” thinking that we spend much of our time in infosec fighting against.

We don’t want arbitrary features like firewall and anti-virus added to these products. It’ll just increase the attack surface making things worse. The one possible exception to this is “patchability”: some IoT devices can’t be patched, and that is a problem. But even here, it’s complicated. Even if IoT devices are patchable in theory there is no guarantee vendors will Continue reading

Debunking Trump’s claim of Google’s SOTU bias

Today, Trump posted this video proving Google promoted all of Obama "State of the Union" (SotU) speeches but none of his own. In this post, I debunk this claim. The short answer is this: it's not Google's fault but Trump's for not having a sophisticated social media team.


The evidence still exists at the Internet Archive (aka. "Wayback Machine") that archives copies of websites. That was probably how that Trump video was created, by using that website. We can indeed see that for Obama's SotU speeches, Google promoted them, such as this example of his January 12, 2016 speech:


And indeed, if we check for Trump's January 30, 2018 speech, there's no such promotion on Google's homepage:
But wait a minute, Google claims they did promote it, and there's even a screenshot on Reddit proving Google is telling the truth. Doesn't this disprove Trump?

No, it actually doesn't, at least not yet. It's comparing two different things. In the Obama example, Google promoted hours ahead of time that there was an upcoming event. In the Trump example, they didn't do that. Only once the event went Continue reading

Provisioning a headless Raspberry Pi

The typical way of installing a fresh Raspberry Pi is to attach power, keyboard, mouse, and an HDMI monitor. This is a pain, especially for the diminutive RPi Zero. This blogpost describes a number of options for doing headless setup. There are several options for this, including Ethernet, Ethernet gadget, WiFi, and serial connection. These examples use a Macbook as an example, maybe I'll get around to a blogpost describing this from Windows.

Burning micro SD card

We are going to edit the SD card before booting, so for completeness, I thought I'd describe the process of burning an SD card.

We are going to download the latest "raspbian" operating system. I download the "lite" version because I'm not using the desktop features. It comes as a compressed .zip file which we need to extract into an .img file. Just double-click on the .zip on Windows or Mac.

The next step is to burn the image to an SD card. On Windows I use Win32DiskImager. On Mac I use the following command-line steps:

$ sudo -s
# mount
# diskutil unmount /dev/disk2s1
# dd bs=1m if=~/Downloads/2018-06-27-raspbian-stretch-lite.img of=/dev/disk2 conv=sync

First, I need a root prompt. I then use the Continue reading

DeGrasse Tyson: Make Truth Great Again

Neil deGrasse Tyson tweets the following:
When people make comparisons with Orwell's "Ministry of Truth", he obtusely persists:
Given that Orwellian dystopias were the theme of this summer's DEF CON hacker conference, let's explore what's wrong with this idea.

Truth vs. "Truth"

I work in a corrupted industry, variously known as the "infosec" community or "cybersecurity" industry. It's a great example of how truth is corrupted into "Truth".

At a recent government policy meeting, I pointed out how vendors often downplay the risk of bugs (vulnerabilities that can be exploited by hackers). When vendors are notified of these bugs and release a patch to fix them, they often give a risk rating. These ratings are often too low, in order to protect the corporate reputation. The representative from Oracle claimed that they didn't do Continue reading

That XKCD on voting machine software is wrong

The latest XKCD comic on voting machine software is wrong, profoundly so. It's the sort of thing that appeals to our prejudices, but mistakes the details.


Accidents vs. attack

The biggest flaw is that the comic confuses accidents vs. intentional attack. Airplanes and elevators are designed to avoid accidental failures. If that's the measure, then voting machine software is fine and perfectly trustworthy. Such machines are no more likely to accidentally record a wrong vote than the paper voting systems they replaced -- indeed less likely. The reason we have electronic voting machines in the first place was due to the "hanging chad" problem in the Bush v. Gore election of the year 2000. After that election, a wave of new, software-based, voting machines replaced the older inaccurate paper machines.

The question is whether software voting machines can be attacked. Well, if that's the measure, then airplanes aren't safe at all. Security against human attack consists of the entire infrastructure outside the plane, such as TSA forcing us to take off our shoes, to trade restrictions to prevent the proliferation of Stinger missiles.

Confusing the two, accidents vs. attack, is used here because it makes the reader feel superior. We Continue reading

What the Caesars (@DefCon) WiFi situation looks like

So I took a survey of WiFi at Caesar's Palace and thought I'd write up some results.


When we go to DEF CON in Vegas, hundreds of us bring our WiFi tools to look at the world. Actually, no special hardware is necessary, as modern laptops/phones have WiFi built-in, while the operating system (Windows, macOS, Linux) enables “monitor mode”. Software is widely available and free. We still love our specialized WiFi dongles and directional antennas, but they aren’t really needed anymore.

It’s also legal, as long as you are just grabbing header information and broadcasts. Which is about all that’s useful anymore as encryption has become the norm -- we can pretty much only see what we are allowed to see. The days of grabbing somebody’s session-cookie and hijacking their web email are long gone (though the was a fun period). There are still a few targets around if you want to WiFi hack, but most are gone.

So naturally I wanted to do a survey of what Caesar’s Palace has for WiFi during the DEF CON hacker conference located there.

Here is a list of access-points (on channel 1 only) sorted by popularity, the number of stations using Continue reading

Some changes in how libpcap works you should know

I thought I'd document the solution to this problem I had.

The API libpcap is the standard cross-platform way of sniffing packets off the network. It works on Windows (winpcap), macOS, and all the Unixes. It's better than simply opening a "raw socket" on Unix platforms because it takes advantage of higher performance capabilities of the system, including specialized sniffing hardware.


Traditionally, you'd open an adapter with pcap_open(), whose function parameters set options like snap length, promiscuous mode, and timeouts.

However, in newer versions of the API, what you should do instead is call pcap_create(), then set the options individually with calls to functions like pcap_set_timeout(), then once you are ready to start capturing, call pcap_activate().

I mention this in relation to "TPACKET" and pcap_set_immediate_mode().

Over the years, Linux has been adding a "ring buffer" mode to packet capture. This is a trick where a packet buffer is memory mapped between user-space and kernel-space. It allows a packet-sniffer to pull packets out of the driver without the overhead of extra copies or system calls that cause a user-kernel space transition. This has gone through several generations.

One of the latest generations causes the pcap_next() function Continue reading

Your IoT security concerns are stupid

Lots of government people are focused on IoT security, such as this recent effort. They are usually wrong. It's a typical cybersecurity policy effort which knows the answer without paying attention to the question. Government efforts focus on vulns and patching, ignoring more important issues.


Patching has little to do with IoT security. For one thing, consumers will not patch vulns, because unlike your phone/laptop computer which is all "in your face", IoT devices, once installed, are quickly forgotten. For another thing, the average lifespan of a device on your network is at least twice the duration of support from the vendor making patches available.

Naive solutions to the manual patching problem, like forcing autoupdates from vendors, increase rather than decrease the danger. Manual patches that don't get applied cause a small, but manageable constant hacking problem. Automatic patching causes rarer, but more catastrophic events when hackers hack the vendor and push out a bad patch. People are afraid of Mirai, a comparatively minor event that led to a quick cleansing of vulnerable devices from the Internet. They should be more afraid of notPetya, the most catastrophic event yet on the Internet that was launched by subverting an automated patch Continue reading

Lessons from nPetya one year later

This is the one year anniversary of NotPetya. It was probably the most expensive single hacker attack in history (so far), with FedEx estimating it cost them $300 million. Shipping giant Maersk and drug giant Merck suffered losses on a similar scale. Many are discussing lessons we should learn from this, but they are the wrong lessons.


An example is this quote in a recent article:
"One year on from NotPetya, it seems lessons still haven't been learned. A lack of regular patching of outdated systems because of the issues of downtime and disruption to organisations was the path through which both NotPetya and WannaCry spread, and this fundamental problem remains." 
This is an attractive claim. It describes the problem in terms of people being "weak" and that the solution is to be "strong". If only organizations where strong enough, willing to deal with downtime and disruption, then problems like this wouldn't happen.

But this is wrong, at least in the case of NotPetya.

NotPetya's spread was initiated through the Ukraining company MeDoc, which provided tax accounting software. It had an auto-update process for keeping its software up-to-date. This was subverted in order to deliver the initial NotPetya Continue reading

SMB version detection in masscan

My Internet-scale port scanner, masscan, supports "banner checking", grabbing basic information from a service after it connects to a port. It's less comprehensive than nmap's version and scripting checks, but it's better than just recording which ports are open.

I recently extended this banner checking to include SMB. It's a complicated protocol so requires a lot more work than just grabbing text banners like you see on FTP. Implementing this, I've found that nmap and smbclient often fail to get version information. They seem focused on getting the information from a standard location in SMBv1 packets, which gives a text string indicating version. There's another place you get get it, from the NTLMSSP pluggable authentication chunks, which gives version numbers in the form of major version, minor version. and build number. Sometimes the SMBv1 information is missing, either because newer Windows version disable SMBv1 by default (supporting only SMBv2) or because they've disabled null/anonymous sessions. They still give NTLMSSP version info, though.


For example, running masscan in my local bar, I get the following result:

Banner on port 445/tcp on 10.1.10.200: [smb] SMBv1  time=2018-06-24 22:18:13 TZ=+240  domain=SHIPBARBO version=6.1.7601 ntlm-ver=15 domain=SHIPBARBO name=SHIPBARBO domain-dns=SHIPBARBO Continue reading

Notes on “The President is Missing”

Former president Bill Clinton has contributed to a cyberthriller "The President is Missing", the plot of which is that the president stops a cybervirus from destroying the country. This is scary, because people in Washington D.C. are going to read this book, believe the hacking portrayed has some basis in reality, and base policy on it. This "news analysis" piece in the New York Times is a good example, coming up with policy recommendations based on fictional cliches rather than a reality of what hackers do.


The cybervirus in the book is some all powerful thing, able to infect everything everywhere without being detected. This is fantasy no more real than magic and faeries. Sure, magical faeries is a popular basis for fiction, but in this case, it's lazy fantasy, a cliche. In fiction, viruses are rarely portrayed as anything other than all powerful.

But in the real world, viruses have important limitations. If you knew anything about computer viruses, rather than being impressed by what they can do, you'd be disappointed by what they can't.

Go look at your home router. See the blinky lights. The light flashes every time a packet of data goes across the network. Continue reading

The First Lady’s bad cyber advice

First Lady Melania Trump announced a guide to help children go online safely. It has problems.

Melania's guide is full of outdated, impractical, inappropriate, and redundant information. But that's allowed, because it relies upon moral authority: to be moral is to be secure, to be moral is to do what the government tells you. It matters less whether the advice is technically accurate, and more that you are supposed to do what authority tells you.

That's a problem, not just with her guide, but most cybersecurity advice in general. Our community gives out advice without putting much thought into it, because it doesn't need thought. You should do what we tell you, because being secure is your moral duty.

This post picks apart Melania's document. The purpose isn't to fine-tune her guide and make it better. Instead, the purpose is to demonstrate the idea of resting on moral authority instead of technical authority.
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Strong Passwords



"Strong passwords" is the quintessential cybersecurity cliché that insecurity is due to some "weakness" (laziness, ignorance, greed, etc.) and the remedy is to be "strong".

The first flaw is that this advice is outdated. Ten years ago, important websites would frequently get hacked and Continue reading

The devil wears Pravda

Classic Bond villain, Elon Musk, has a new plan to create a website dedicated to measuring the credibility and adherence to "core truth" of journalists. He is, without any sense of irony, going to call this "Pravda". This is not simply wrong but evil.


Musk has a point. Journalists do suck, and many suck consistently. I see this in my own industry, cybersecurity, and I frequently criticize them for their suckage.

But what he's doing here is not correcting them when they make mistakes (or what Musk sees as mistakes), but questioning their legitimacy. This legitimacy isn't measured by whether they follow established journalism ethics, but whether their "core truths" agree with Musk's "core truths".

An example of the problem is how the press fixates on Tesla car crashes due to its "autopilot" feature. Pretty much every autopilot crash makes national headlines, while the press ignores the other 40,000 car crashes that happen in the United States each year. Musk spies on Tesla drivers (hello, classic Bond villain everyone) so he can see the dip in autopilot usage every time such a news story breaks. He's got good reason to be concerned about this.

He argues that autopilot is safer Continue reading

C is to low level

I'm in danger of contradicting myself, after previously pointing out that x86 machine code is a high-level language, but this article claiming C is a not a low level language is bunk. C certainly has some problems, but it's still the closest language to assembly. This is obvious by the fact it's still the fastest compiled language. What we see is a typical academic out of touch with the real world.

The author makes the (wrong) observation that we've been stuck emulating the PDP-11 for the past 40 years. C was written for the PDP-11, and since then CPUs have been designed to make C run faster. The author imagines a different world, such as where CPU designers instead target something like LISP as their preferred language, or Erlang. This misunderstands the state of the market. CPUs do indeed supports lots of different abstractions, and C has evolved to accommodate this.


The author criticizes things like "out-of-order" execution which has lead to the Spectre sidechannel vulnerabilities. Out-of-order execution is necessary to make C run faster. The author claims instead that those resources should be spent on having more slower CPUs, with more threads. This sacrifices single-threaded performance in exchange Continue reading

masscan, macOS, and firewall

One of the more useful features of masscan is the "--banners" check, which connects to the TCP port, sends some request, and gets a basic response back. However, since masscan has it's own TCP stack, it'll interfere with the operating system's TCP stack if they are sharing the same IPv4 address. The operating system will reply with a RST packet before the TCP connection can be established.

The way to fix this is to use the built-in packet-filtering firewall to block those packets in the operating-system TCP/IP stack. The masscan program still sees everything before the packet-filter, but the operating system can't see anything after the packet-filter.


Note that we are talking about the "packet-filter" firewall feature here. Remember that macOS, like most operating systems these days, has two separate firewalls: an application firewall and a packet-filter firewall. The application firewall is the one you see in System Settings labeled "Firewall", and it controls things based upon the application's identity rather than by which ports it uses. This is normally "on" by default. The packet-filter is normally "off" by default and is of little use to normal users.

Also note that macOS changed packet-filters around version 10.10. Continue reading

Some notes on eFail

I've been busy trying to replicate the "eFail" PGP/SMIME bug. I thought I'd write up some notes.

PGP and S/MIME encrypt emails, so that eavesdroppers can't read them. The bugs potentially allow eavesdroppers to take the encrypted emails they've captured and resend them to you, reformatted in a way that allows them to decrypt the messages.

Disable remote/external content in email

The most important defense is to disable "external" or "remote" content from being automatically loaded. This is when HTML-formatted emails attempt to load images from remote websites. This happens legitimately when they want to display images, but not fill up the email with them. But most of the time this is illegitimate, they hide images on the webpage in order to track you with unique IDs and cookies. For example, this is the code at the end of an email from politician Bernie Sanders to his supporters. Notice the long random number assigned to track me, and the width/height of this image is set to one pixel, so you don't even see it:

Such trackers are so pernicious they are disabled by default in most email clients. This is an example of the settings in Thunderbird:


The problem is Continue reading

Leaking securely, for White House staffers

Spencer Ackerman has this interesting story about a guy assigned to crack down on unauthorized White House leaks. It's necessarily light on technical details, so I thought I'd write up some guesses, either as a guide for future reporters asking questions, or for people who want to better know the risks when leak information.

It should come as no surprise that your work email and phone are already monitored. They can get every email you've sent or received, even if you've deleted it. They can get every text message you've sent or received, the metadata of every phone call sent or received, and so forth.

To a lesser extent, this also applies to your well-known personal phone and email accounts. Law enforcement can get the metadata (which includes text messages) for these things without a warrant. In the above story, the person doing the investigation wasn't law enforcement, but I'm not sure that's a significant barrier if they can pass things onto the Secret Service or something.

The danger here isn't that you used these things to leak, it's that you've used these things to converse with the reporter before you made the decision to leak. That's what happened in Continue reading

No, Ray Ozzie hasn’t solved crypto backdoors

According to this Wired article, Ray Ozzie may have a solution to the crypto backdoor problem. No, he hasn't. He's only solving the part we already know how to solve. He's deliberately ignoring the stuff we don't know how to solve. We know how to make backdoors, we just don't know how to secure them.


The vault doesn't scale

Yes, Apple has a vault where they've successfully protected important keys. No, it doesn't mean this vault scales. The more people and the more often you have to touch the vault, the less secure it becomes. We are talking thousands of requests per day from 100,000 different law enforcement agencies around the world. We are unlikely to protect this against incompetence and mistakes. We are definitely unable to secure this against deliberate attack.

A good analogy to Ozzie's solution is LetsEncrypt for getting SSL certificates for your website, which is fairly scalable, using a private key locked in a vault for signing hundreds of thousands of certificates. That this scales seems to validate Ozzie's proposal.

But at the same time, LetsEncrypt is easily subverted. LetsEncrypt uses DNS to verify your identity. But spoofing DNS is easy, as was recently shown in Continue reading

OMG The Stupid It Burns

This article, pointed out by @TheGrugq, is stupid enough that it's worth rebutting.




The article starts with the question "Why did the lessons of Stuxnet, Wannacry, Heartbleed and Shamoon go unheeded?". It then proceeds to ignore the lessons of those things.

Some of the actual lessons should be things like how Stuxnet crossed air gaps, how Wannacry spread through flat Windows networking, how Heartbleed comes from technical debt, and how Shamoon furthers state aims by causing damage.

But this article doesn't cover the technical lessons. Instead, it thinks the lesson should be the moral lesson, that we should take these things more seriously. But that's stupid. It's the sort of lesson people teach you that know nothing about the topic. When you have nothing of value to contribute to a topic you can always take the moral high road and criticize everyone for being morally weak for not taking it Continue reading
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