Details on a New PGP Vulnerability

A new PGP vulnerability was announced today. Basically, the vulnerability makes use of the fact that modern e-mail programs allow for embedded HTML objects. Essentially, if an attacker can intercept and modify a message in transit, he can insert code that sends the plaintext in a URL to a remote website. Very clever. The EFAIL attacks exploit vulnerabilities in the…

A new PGP vulnerability was announced today. Basically, the vulnerability makes use of the fact that modern e-mail programs allow for embedded HTML objects. Essentially, if an attacker can intercept and modify a message in transit, he can insert code that sends the plaintext in a URL to a remote website. Very clever.

The EFAIL attacks exploit vulnerabilities in the OpenPGP and S/MIME standards to reveal the plaintext of encrypted emails. In a nutshell, EFAIL abuses active content of HTML emails, for example externally loaded images or styles, to exfiltrate plaintext through requested URLs. To create these exfiltration channels, the attacker first needs access to the encrypted emails, for example, by eavesdropping on network traffic, compromising email accounts, email servers, backup systems or client computers. The emails could even have been collected years ago.

The attacker changes an encrypted email in a particular way and sends this changed encrypted email to the victim. The victim's email client decrypts the email and loads any external content, thus exfiltrating the plaintext to the attacker.

A few initial comments:

1. Being able to intercept and modify e-mails in transit is the sort of thing the NSA can do, but is hard for the average hacker. That being said, there are circumstances where someone can modify e-mails. I don't mean to minimize the seriousness of this attack, but that is a consideration.

2. The vulnerability isn't with PGP or S/MIME itself, but in the way they interact with modern e-mail programs. You can see this in the two suggested short-term mitigations: "No decryption in the e-mail client," and "disable HTML rendering."

3. I've been getting some weird press calls from reporters wanting to know if this demonstrates that e-mail encryption is impossible. No, this just demonstrates that programmers are human and vulnerabilities are inevitable. PGP almost certainly has fewer bugs than your average piece of software, but it's not bug free.

3. Why is anyone using encrypted e-mail anymore, anyway? Reliably and easily encrypting e-mail is an insurmountably hard problem for reasons having nothing to do with today's announcement. If you need to communicate securely, use Signal. If having Signal on your phone will arouse suspicion, use WhatsApp.

I'll post other commentaries and analyses as I find them.

from https://www.schneier.com/blog/

Critical PGP Vulnerability

EFF is reporting that a critical vulnerability has been discovered in PGP and S/MIME. No details have been published yet, but one of the researchers wrote: We’ll publish critical vulnerabilities in PGP/GPG and S/MIME email encryption on 2018-05-15 07:00 UTC. They might reveal the plaintext of encrypted emails, including encrypted emails sent in the past. There are currently no reliable…

EFF is reporting that a critical vulnerability has been discovered in PGP and S/MIME. No details have been published yet, but one of the researchers wrote:

We'll publish critical vulnerabilities in PGP/GPG and S/MIME email encryption on 2018-05-15 07:00 UTC. They might reveal the plaintext of encrypted emails, including encrypted emails sent in the past. There are currently no reliable fixes for the vulnerability. If you use PGP/GPG or S/MIME for very sensitive communication, you should disable it in your email client for now.

This sounds like a protocol vulnerability, but we'll learn more tomorrow.

News articles.

from https://www.schneier.com/blog/

Obscure E-Mail Vulnerability

This vulnerability is a result of an interaction between two different ways of handling e-mail addresses. Gmail ignores dots in addresses, so bruce.schneier@gmail.com is the same as bruceschneier@gmail.com is the same as b.r.u.c.e.schneier@gmail.com. (Note: I do not own any of those email addresses — if they’re even valid.) Netflix doesn’t ignore dots, so those are all unique e-mail addresses and…

This vulnerability is a result of an interaction between two different ways of handling e-mail addresses. Gmail ignores dots in addresses, so bruce.schneier@gmail.com is the same as bruceschneier@gmail.com is the same as b.r.u.c.e.schneier@gmail.com. (Note: I do not own any of those email addresses -- if they're even valid.) Netflix doesn't ignore dots, so those are all unique e-mail addresses and can each be used to register an account. This difference can be exploited.

I was almost fooled into perpetually paying for Eve's Netflix access, and only paused because I didn't recognize the declined card. More generally, the phishing scam here is:

  1. Hammer the Netflix signup form until you find a gmail.com address which is "already registered". Let's say you find the victim jameshfisher.
  2. Create a Netflix account with address james.hfisher.
  3. Sign up for free trial with a throwaway card number.
  4. After Netflix applies the "active card check", cancel the card.
  5. Wait for Netflix to bill the cancelled card. Then Netflix emails james.hfisher asking for a valid card.
  6. Hope Jim reads the email to james.hfisher, assumes it's for his Netflix account backed by jameshfisher, then enters his card **** 1234.
  7. Change the email for the Netflix account to eve@gmail.com, kicking Jim's access to this account.
  8. Use Netflix free forever with Jim's card **** 1234!

Obscure, yes? A problem, yes?

James Fisher, who wrote the post, argues that it's Google's fault. Ignoring dots might give people an enormous number of different email addresses, but it's not a feature that people actually want. And as long as other sites don't follow Google's lead, these sorts of problems are possible.

I think the problem is more subtle. It's an example of two systems without a security vulnerability coming together to create a security vulnerability. As we connect more systems directly to each other, we're going to see a lot more of these. And like this Google/Netflix interaction, it's going to be hard to figure out who to blame and who -- if anyone -- has the responsibility of fixing it.

from https://www.schneier.com/blog/

E-Mailing Private HTTPS Keys

I don’t know what to make of this story: The email was sent on Tuesday by the CEO of Trustico, a UK-based reseller of TLS certificates issued by the browser-trusted certificate authorities Comodo and, until recently, Symantec. It was sent to Jeremy Rowley, an executive vice president at DigiCert, a certificate authority that acquired Symantec’s certificate issuance business after Symantec…

I don't know what to make of this story:

The email was sent on Tuesday by the CEO of Trustico, a UK-based reseller of TLS certificates issued by the browser-trusted certificate authorities Comodo and, until recently, Symantec. It was sent to Jeremy Rowley, an executive vice president at DigiCert, a certificate authority that acquired Symantec's certificate issuance business after Symantec was caught flouting binding industry rules, prompting Google to distrust Symantec certificates in its Chrome browser. In communications earlier this month, Trustico notified DigiCert that 50,000 Symantec-issued certificates Trustico had resold should be mass revoked because of security concerns.

When Rowley asked for proof the certificates were compromised, the Trustico CEO emailed the private keys of 23,000 certificates, according to an account posted to a Mozilla security policy forum. The report produced a collective gasp among many security practitioners who said it demonstrated a shockingly cavalier treatment of the digital certificates that form one of the most basic foundations of website security.

Generally speaking, private keys for TLS certificates should never be archived by resellers, and, even in the rare cases where such storage is permissible, they should be tightly safeguarded. A CEO being able to attach the keys for 23,000 certificates to an email raises troubling concerns that those types of best practices weren't followed.

I am croggled by the multiple layers of insecurity here.

BoingBoing post.

from https://www.schneier.com/blog/

E-Mail Tracking

Good article on the history and practice of e-mail tracking: The tech is pretty simple. Tracking clients embed a line of code in the body of an email­ — usually in a 1×1 pixel image, so tiny it’s invisible, but also in elements like hyperlinks and custom fonts. When a recipient opens the email, the tracking client recognizes that pixel…

Good article on the history and practice of e-mail tracking:

The tech is pretty simple. Tracking clients embed a line of code in the body of an email­ -- usually in a 1x1 pixel image, so tiny it's invisible, but also in elements like hyperlinks and custom fonts. When a recipient opens the email, the tracking client recognizes that pixel has been downloaded, as well as where and on what device. Newsletter services, marketers, and advertisers have used the technique for years, to collect data about their open rates; major tech companies like Facebook and Twitter followed suit in their ongoing quest to profile and predict our behavior online.

But lately, a surprising­ -- and growing­ -- number of tracked emails are being sent not from corporations, but acquaintances. "We have been in touch with users that were tracked by their spouses, business partners, competitors," says Florian Seroussi, the founder of OMC. "It's the wild, wild west out there."

According to OMC's data, a full 19 percent of all "conversational" email is now tracked. That's one in five of the emails you get from your friends. And you probably never noticed.

I admit it's enticing. I would very much like the statistics that adding trackers to Crypto-Gram would give me. But I still don't do it.

from https://www.schneier.com/blog/

Cybercriminals Infiltrating E-Mail Networks to Divert Large Customer Payments

There’s a new criminal tactic involving hacking an e-mail account of a company that handles high-value transactions and diverting payments. Here it is in real estate: The scam generally works like this: Hackers find an opening into a title company’s or realty agent’s email account, track upcoming home purchases scheduled for settlements — the pricier the better — then assume…

There's a new criminal tactic involving hacking an e-mail account of a company that handles high-value transactions and diverting payments. Here it is in real estate:

The scam generally works like this: Hackers find an opening into a title company's or realty agent's email account, track upcoming home purchases scheduled for settlements -- the pricier the better -- then assume the identity of the title agency person handling the transaction.

Days or sometimes weeks before the settlement, the scammer poses as the title or escrow agent whose email accounts they've hijacked and instructs the home buyer to wire the funds needed to close -- often hundreds of thousands of dollars, sometimes far more -- to the criminals' own bank accounts, not the title or escrow company's legitimate accounts. The criminals then withdraw the money and vanish.

Here it is in fine art:

The fraud is relatively simple. Criminals hack into an art dealer's email account and monitor incoming and outgoing correspondence. When the gallery sends a PDF invoice to a client via email following a sale, the conversation is hijacked. Posing as the gallery, hackers send a duplicate, fraudulent invoice from the same gallery email address, with an accompanying message instructing the client to disregard the first invoice and instead wire payment to the account listed in the fraudulent document.

Once money has been transferred to the criminals' account, the hackers move the money to avoid detection and then disappear. The same technique is used to intercept payments made by galleries to their artists and others. Because the hackers gain access to the gallery's email contacts, the scam can spread quickly, with fraudulent emails appearing to come from known sources.

I'm sure it's happening in other industries as well, probably even with business-to-business commerce.

EDITED TO ADD (11/14): Brian Krebs wrote about this in 2014.

from https://www.schneier.com/blog/

Journalists Generally Do Not Use Secure Communication

This should come as no surprise: Alas, our findings suggest that secure communications haven’t yet attracted mass adoption among journalists. We looked at 2,515 Washington journalists with permanent credentials to cover Congress, and we found only 2.5 percent of them solicit end-to-end encrypted communication via their Twitter bios. That’s just 62 out of all the broadcast, newspaper, wire service, and…

This should come as no surprise:

Alas, our findings suggest that secure communications haven't yet attracted mass adoption among journalists. We looked at 2,515 Washington journalists with permanent credentials to cover Congress, and we found only 2.5 percent of them solicit end-to-end encrypted communication via their Twitter bios. That's just 62 out of all the broadcast, newspaper, wire service, and digital reporters. Just 28 list a way to reach them via Signal or another secure messaging app. Only 22 provide a PGP public key, a method that allows sources to send encrypted messages. A paltry seven advertise a secure email address. In an era when anything that can be hacked will be and when the president has declared outright war on the media, this should serve as a frightening wake-up call.

[...]

When journalists don't step up, sources with sensitive information face the burden of using riskier modes of communication to initiate contact­ -- and possibly conduct all of their exchanges­ -- with reporters. It increases their chances of getting caught, putting them in danger of losing their job or facing prosecution. It's burden enough to make them think twice about whistleblowing.

I forgive them for not using secure e-mail. It's hard to use and confusing. But secure messaging is easy.

from https://www.schneier.com/blog/

The Pro-PGP Position

A few days ago, I blogged an excellent essay by Filippo Valsorda on why he’s giving up on PGP. Neal Walkfield wrote a good rebuttal. I am on Valsorda’s side. I don’t like PGP, and I use it as little as possible. If I want to communicate securely with someone, I use Signal….

A few days ago, I blogged an excellent essay by Filippo Valsorda on why he's giving up on PGP. Neal Walkfield wrote a good rebuttal.

I am on Valsorda's side. I don't like PGP, and I use it as little as possible. If I want to communicate securely with someone, I use Signal.

from https://www.schneier.com/blog/

Giving Up on PGP

Filippo Valsorda wrote an exellent essay on why he’s giving up on PGP. I have long believed PGP to be more trouble than it is worth. It’s hard to use correctly, and easy to get wrong. More generally, e-mail is inherently difficult to secure because of all the different things we ask of it and use it for. Valsorda has…

Filippo Valsorda wrote an exellent essay on why he’s giving up on PGP. I have long believed PGP to be more trouble than it is worth. It’s hard to use correctly, and easy to get wrong. More generally, e-mail is inherently difficult to secure because of all the different things we ask of it and use it for.

Valsorda has a different complaint, that its long-term secrets are an unnecessary source of risk:

But the real issues, I realized, are more subtle. I never felt confident in the security of my long-term keys. The more time passed, the more I would feel uneasy about any specific key. Yubikeys would get exposed to hotel rooms. Offline keys would sit in a far away drawer or safe. Vulnerabilities would be announced. USB devices would get plugged in.

A long-term key is as secure as the minimum common denominator of your security practices over its lifetime. It’s the weak link.

Worse, long-term key patterns, like collecting signatures and printing fingerprints on business cards, discourage practices that would otherwise be obvious hygiene: rotating keys often, having different keys for different devices, compartmentalization. Such practices actually encourage expanding the attack surface by making backups of the key.

Both he and I favor encrypted messaging, either Signal or OTR.