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A new set of vulnerabilities affecting users of PGP and S/MIME

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Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#71

Post by virusduck »

simias wrote: post #48
fensipens wrote: post #41

Response by Werner Koch (GPG), contains some details: https://lists.gnupg.org/pipermail/gnupg-users/2018-May/06031...

>Due to broken MIME parsers a bunch of MUAs seem to concatenate decrypted HTML mime parts which makes it easy to plant such HTML snippets. To me this sounds strictly like a MUA issue, not a PGP/SMIME one. If that's really all it is it does seem massively overblown to me. Why not single out the broken MUA implementations instead of saying "don't decrypt emails OR YOU'LL DIE"? I mean just look at the wild speculation i…

I dunno, a client issue like this seems pretty terrible to me since there is no obvious (to me) way to fix it. If I am encrypting a message, I have no control over what client decrypts it (and whether that client unwittingly passes the information along) without maybe changing the standard completely.

The thing is, If I am reading correctly, it seems like this kind of vulnerability seems totally predictable.

Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#73

Post by Jach »

rdl wrote: post #29

I've always handled PGP via cut-and-paste of the ascii armored block, through a text file on a ramdisk (or between systems), then using command-line pgp or gpg to decrypt, and the reverse. Not always on a VM or machine without external network access, but for signing keys for software and stuff, yes. It just seemed too easy to mess up auto-decrypt/auto-encrypt and accidentally send out cleartext -- the cut and paste…

On Android, the OpenKeychain app suits my needs just fine on the rare occasion I need to encrypt/decrypt on mobile, though I've never used its email integration... Apart from that I have basically the same workflow. I wrote a GUI program once to play with Clojure + Apache Pivot that lets me copy/paste text into the program's text fields and gives a dropdown of public keys (or an option to add a key), that's sometimes a bit more convenient. I can also explicitly manage whether I add myself as a recipient or not, lots of email clients seem to automatically encrypt to the sender's key as well so they can read it later.

Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#75

Post by tzs »

gsich wrote: post #74
tzs wrote: post #67

Earlier quoted context omitted.

That ship sailed when email got named email instead of etelegram.

Why do you think so? People are not forced to use HTML mails. I don't.

Oh, I thought you were making the "email should only be text" argument, not the "you should avoid looking at the non-text part of multipart email" argument. I was addressing the former.

Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#76

Post by pdfernhout »

From an essay I wrote in 2015 on "Why Encryption Use Is Problematical When Advocating For Social Change": http://pdfernhout.net/why-encryption-use-is-problematical-wh... "In general, a system intended to ensure private communications is only as secure as its weakest link. If any of these levels is compromised (hardware, firmware, OS, application, algorithm theory, algorithm implementation, user error, user loyalty, etc.) then your communications are compromised. ... If you want to build a mass movement, at some point, you need to engage people. In practice, for social psychology reasons, engaging people is very difficult, if not impossible, to do completely anonymously in an untraceable way. People have historically built mass movements without computers or the internet. It's not clear if the internet really makes this easier for activists or instead just for the status quo who wants to monitor them. If you work in public, you don't have to fear loss of secure communications because you never structure your movement to rely on them. If you rely on "secure" communications, then you may set yourself up to fail when such communications are compromised. If your point is to build a mass movement, then where should your focus be? ..."

Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#78

Post by jstanley »

im3w1l wrote: post #40
jstanley wrote: post #22

Earlier quoted context omitted.

Good point. I wonder what kind of flaw in PGP's design could make it unsafe to decrypt incoming mails.

At a guess: 1. Take previous email (X) that you want to decrypt. 2. Apply transformation (this is the actual secret sauce) to previous X to get email Y. 3. Because of how Y was constructed, decrypting it causes X to be decypted. 4. Phone home with the result by using some kind of tracking pixel. My reasoning is that they didn't talk about RCE and they didn't talk about stealing the key, and they did warn about automa…

Update: you were right :)

Re: A new set of vulnerabilities affecting users of PGP and S/MIME

#79

Post by simias »

virusduck wrote: post #71
simias wrote: post #48

Earlier quoted context omitted.

>Due to broken MIME parsers a bunch of MUAs seem to concatenate decrypted HTML mime parts which makes it easy to plant such HTML snippets. To me this sounds strictly like a MUA issue, not a PGP/SMIME one. If that's really all it is it does seem massively overblown to me. Why not single out the broken MUA implementations instead of saying "don't decrypt emails OR YOU'LL DIE"? I mean just look at the wild speculation i…

I dunno, a client issue like this seems pretty terrible to me since there is no obvious (to me) way to fix it. If I am encrypting a message, I have no control over what client decrypts it (and whether that client unwittingly passes the information along) without maybe changing the standard completely. The thing is, If I am reading correctly, it seems like this kind of vulnerability seems totally predictable.

I agree, after getting the details it's fair to say that while some MUAs should fix their handling of encrypted emails PGP implementations and the S/MIME standard shares a part of the blame by not detecting and preventing the decoding of tampered documents. Still, the way the problem was disclosed is rather misleading and confusing.
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