• Attention PGP Users : New Vulnerabilities Require You To Take Action Now | Electronic Frontier Foundation
    https://www.eff.org/deeplinks/2018/05/attention-pgp-users-new-vulnerabilities-require-you-take-action-now

    A group of European security researchers have released a warning about a set of vulnerabilities affecting users of PGP and S/MIME. EFF has been in communication with the research team, and can confirm that these vulnerabilities pose an immediate risk to those using these tools for email communication, including the potential exposure of the contents of past messages.

    The full details will be published in a paper on Tuesday at 07:00 AM UTC (3:00 AM Eastern, midnight Pacific). In order to reduce the short-term risk, we and the researchers have agreed to warn the wider PGP user community in advance of its full publication.

    Our advice, which mirrors that of the researchers, is to immediately disable and/or uninstall tools that automatically decrypt PGP-encrypted email. Until the flaws described in the paper are more widely understood and fixed, users should arrange for the use of alternative end-to-end secure channels, such as Signal, and temporarily stop sending and especially reading PGP-encrypted email.

    #sécurité #boum

    • Par contre, si vous n’utilisez que des messages au format « texte » il semble qu’il n’y ait pas de trou de sécu. L’algorithme de PGP est toujour aussi sûr que possibe après meltdown :-)

      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.

      EFAIL
      https://efail.de

      EFAIL describes vulnerabilities in the end-to-end encryption technologies OpenPGP and S/MIME that leak the plaintext of encrypted emails.

    • OK, après la première lecture du site efail.de il semble qu’on puisse se protéger en suivant les indications suivantes :

      Mitigations

      Here are some strategies to prevent EFAIL attacks:

      Short term: No decryption in email client. The best way to prevent EFAIL attacks is to only decrypt S/MIME or PGP emails in a separate application outside of your email client. Start by removing your S/MIME and PGP private keys from your email client, then decrypt incoming encrypted emails by copy&pasting the ciphertext into a separate application that does the decryption for you. That way, the email clients cannot open exfiltration channels. This is currently the safest option with the downside that the process gets more involved.

      Short term: Disable HTML rendering. The EFAIL attacks abuse active content, mostly in the form of HTML images, styles, etc. Disabling the presentation of incoming HTML emails in your email client will close the most prominent way of attacking EFAIL. Note that there are other possible backchannels in email clients which are not related to HTML but these are more difficult to exploit.

      Medium term: Patching. Some vendors will publish patches that either fix the EFAIL vulnerabilities or make them much harder to exploit.

      Long term: Update OpenPGP and S/MIME standards. The EFAIL attacks exploit flaws and undefined behavior in the MIME, S/MIME, and OpenPGP standards. Therefore, the standards need to be updated, which will take some time.