We have published Qubes Security Bulletin 094: x86/AMD: Divide speculative information leak. The text of this QSB and its accompanying cryptographic signatures are reproduced below. For an explanation of this announcement and instructions for authenticating this QSB, please see the end of this announcement.
Qubes Security Bulletin 094
---===[ Qubes Security Bulletin 094 ]===--- 2023-09-27 x86/AMD: Divide speculative information leak User action required --------------------- Users must install the following specific packages in order to address the issues discussed in this bulletin: For Qubes 4.1, in dom0: - Xen packages, version 4.14.6-2 For Qubes 4.2, in dom0: - Xen packages, version 4.17.2-2 Dom0 must be restarted afterward in order for the updates to take effect. If you use Anti Evil Maid, you will need to reseal your secret passphrase to new PCR values, as PCR18+19 will change due to the new Xen binaries. Summary -------- On 2023-09-25, the Xen Project published XSA-439, "x86/AMD: Divide speculative information leak" : | In the Zen1 microarchitecture, there is one divider in the | pipeline which services uops from both threads. In the case of #DE, | the latched result from the previous DIV to execute will be forwarded | speculatively. | | This is a covert channel that allows two threads to communicate | without any system calls. In also allows userspace to obtain the | result of the most recent DIV instruction executed (even | speculatively) in the core, which can be from a higher privilege | context. For more information, see: * https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7007.html Impact ------- On systems with an AMD Zen (first generation) CPU, an attacker who compromises a VM can attempt to exploit this vulnerability in order to infer the contents of data from a different execution context on the same CPU core. This includes data belonging to a different VM (which could be dom0) that was previously scheduled on that CPU core and Xen itself. The latter is relevant because some system operations require Xen to load data from a VM. This data may or may not be sensitive. However, the attacker has no control over the data that Xen loads (and, to some extent, no knowledge of what was loaded). Credits -------- See the original Xen Security Advisory. References -----------  https://www.qubes-os.org/doc/testing/  https://www.qubes-os.org/doc/how-to-update/  https://xenbits.xen.org/xsa/advisory-439.html -- The Qubes Security Team https://www.qubes-os.org/security/
Marek Marczykowski-Górecki’s PGP signature
-----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEELRdx/k12ftx2sIn61lWk8hgw4GoFAmUTmvAACgkQ1lWk8hgw 4Go4DQ/9Gf5Jy377V8kLXSmxYcNBd2MLTkZ5SO1zbjcvZaHv19NL/QtONAYHnNFz PrUiBwai6//LGevV8SMAIr+ytADZDFN2kukMk+GCWfG5DSIqkVwcqWkSI/7Tc6sH 0LRoWcAJKNovZRLr+SHj1v5OP8E+42JTTv9k/3SlYVMVI6wuQ61dd0gnC32Wb6SA 4fj7VOOCuC0OfSAT+PBmp5EV8+4RgytzIrtbvaaFG7jhdVPX6bfkcDzSKJkcFLjV wlzwMkVk0hbDMTRwP3ZumUYbd9iA30JK+Q0lFwGX/MdMJ/mALnYSjlGh3XyDRBDE OxudQZ6PFTbhMbVmuJk69J999s537mQI6nyh7ygrrHgnxyqJq647U5bvG74jDEP1 SMCRXRCmQ+90HeTzDbFyJk9WVfWQtZh3e5vpDsSYJVcHVoSq50Zs3nVHAmiGWcJR M+u0vwaSPBWKKtxtvfcZw9GU2m9QoD03/JellZOfOhgafPHfmDUqLi/BsI0oN2WZ ABDZT3zwzwE7L8fRXPrYSnr3bNqx8ukIU6+DPEE+7Ckfkh4Z9KGCh7VmDs7wUL32 K9ugM9g8xARTQqs85uBQdohEWYU3M53uxb51AyFy8l6uJDpuOUgQnptqrQf2YjES /Ih03fE2Husc97qdsAGDlqet6wB57rbCpDy20+EYQFvXE7vynsg= =HOO+ -----END PGP SIGNATURE-----
Simon Gaiser (aka HW42)’s PGP signature
-----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE6hjn8EDEHdrv6aoPSsGN4REuFJAFAmUTncEACgkQSsGN4REu FJClzQ/+JkYPyrNcKWpHPvoxti+QxQLpZq1KvkIY/otEPMAFaDsmLg3sjcsd0Hs2 Co7kD6jy0BknS+ICBqc1eCQFwjU3cJn5Ay8F/G/zndK8UZDJWhj8ImPF79RJvawH l9QqVIGndis9XuSlkWXXV2Hi+bt55HOA2YwlrLg2XW/ptrsvHr61qA8VPWaVPncx DKH106S03a3tBDpTRnsUq/YZM1MYvXnzylKHrIF/TD2h0h2LmhPWNP812u3/Qt25 DqidNV23/l/Xri+gK0Mvnxel4nsBRz+iQBPcB+cMnYmOJ/jnVZsVS74/FBsj54q8 Uiphy0OrHLFjYFcv/eLIAKArcRrfILfRftUe7NyGjp4oIeKNGFc8zRf791gNUNiJ 1u4hwsH8W6xtLiERRv5K0d3UGZak8qmR3UgJ32gf+sF77kAc7Qe/200qyjmPwYG3 +4pO1UcFrAOaNBKG1aSp2J6byDc8ZO6qCv0XG+FcI6cntGBbAQjkrjclH+nSwF5M CPWd+nFwZe2EVjprebiTZfYA0nyiQKRkRf8RmCd316WG7IYktMny2TIrADn/rGcR d+RmHGBaRArPwPyefsre32jgpauRJ8hw5hwCenT2ELO17MsK/2FFp0Cguhyd2yEZ u9e5kmZK5o6FDqqZIHQFNmRyFWA3Jr5uygAZ0TetRroNlnKl96o= =yvp2 -----END PGP SIGNATURE-----
What is the purpose of this announcement?
The purpose of this announcement is to inform the Qubes community that a new Qubes security bulletin (QSB) has been published.
What is a Qubes security bulletin (QSB)?
A Qubes security bulletin (QSB) is a security announcement issued by the Qubes security team. A QSB typically provides a summary and impact analysis of one or more recently-discovered software vulnerabilities, including details about patching to address them. A list of all QSBs is available here.
Why should I care about QSBs?
QSBs tell you what actions you must take in order to protect yourself from recently-discovered security vulnerabilities. In most cases, security vulnerabilities are addressed by updating normally. However, in some cases, special user action is required. In all cases, the required actions are detailed in QSBs.
What are the PGP signatures that accompany QSBs?
A PGP signature is a cryptographic digital signature made in accordance with the OpenPGP standard. PGP signatures can be cryptographically verified with programs like GNU Privacy Guard (GPG). The Qubes security team cryptographically signs all QSBs so that Qubes users have a reliable way to check whether QSBs are genuine. The only way to be certain that a QSB is authentic is by verifying its PGP signatures.
Why should I care whether a QSB is authentic?
A forged QSB could deceive you into taking actions that adversely affect the security of your Qubes OS system, such as installing malware or making configuration changes that render your system vulnerable to attack. Falsified QSBs could sow fear, uncertainty, and doubt about the security of Qubes OS or the status of the Qubes OS Project.
How do I verify the PGP signatures on a QSB?
The following command-line instructions assume a Linux system with
gpg installed. (See here for Windows and Mac options.)
Obtain the Qubes Master Signing Key (QMSK), e.g.:
$ gpg --fetch-keys https://keys.qubes-os.org/keys/qubes-master-signing-key.asc gpg: directory '/home/user/.gnupg' created gpg: keybox '/home/user/.gnupg/pubring.kbx' created gpg: requesting key from 'https://keys.qubes-os.org/keys/qubes-master-signing-key.asc' gpg: /home/user/.gnupg/trustdb.gpg: trustdb created gpg: key DDFA1A3E36879494: public key "Qubes Master Signing Key" imported gpg: Total number processed: 1 gpg: imported: 1
(See here for more ways to obtain the QMSK.)
View the fingerprint of the PGP key you just imported. (Note:
gpg>indicates a prompt inside of the GnuPG program. Type what appears after it when prompted.)
$ gpg --edit-key 0x427F11FD0FAA4B080123F01CDDFA1A3E36879494 gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. pub rsa4096/DDFA1A3E36879494 created: 2010-04-01 expires: never usage: SC trust: unknown validity: unknown [ unknown] (1). Qubes Master Signing Key gpg> fpr pub rsa4096/DDFA1A3E36879494 2010-04-01 Qubes Master Signing Key Primary key fingerprint: 427F 11FD 0FAA 4B08 0123 F01C DDFA 1A3E 3687 9494
Important: At this point, you still don’t know whether the key you just imported is the genuine QMSK or a forgery. In order for this entire procedure to provide meaningful security benefits, you must authenticate the QMSK out-of-band. Do not skip this step! The standard method is to obtain the QMSK fingerprint from multiple independent sources in several different ways and check to see whether they match the key you just imported. See here for more details and ideas for how to do that.
Tip: Record the genuine QMSK fingerprint in a safe place (or several) so that you don’t have to repeat this step in the future.
Once you are satisfied that you have the genuine QMSK, set its trust level to 5 (“ultimate”), then quit GnuPG with
gpg> trust pub rsa4096/DDFA1A3E36879494 created: 2010-04-01 expires: never usage: SC trust: unknown validity: unknown [ unknown] (1). Qubes Master Signing Key Please decide how far you trust this user to correctly verify other users' keys (by looking at passports, checking fingerprints from different sources, etc.) 1 = I don't know or won't say 2 = I do NOT trust 3 = I trust marginally 4 = I trust fully 5 = I trust ultimately m = back to the main menu Your decision? 5 Do you really want to set this key to ultimate trust? (y/N) y pub rsa4096/DDFA1A3E36879494 created: 2010-04-01 expires: never usage: SC trust: ultimate validity: unknown [ unknown] (1). Qubes Master Signing Key Please note that the shown key validity is not necessarily correct unless you restart the program. gpg> q
Use Git to clone the qubes-secpack repo.
$ git clone https://github.com/QubesOS/qubes-secpack.git Cloning into 'qubes-secpack'... remote: Enumerating objects: 4065, done. remote: Counting objects: 100% (1474/1474), done. remote: Compressing objects: 100% (742/742), done. remote: Total 4065 (delta 743), reused 1413 (delta 731), pack-reused 2591 Receiving objects: 100% (4065/4065), 1.64 MiB | 2.53 MiB/s, done. Resolving deltas: 100% (1910/1910), done.
Import the included PGP keys. (See our PGP key policies for important information about these keys.)
$ gpg --import qubes-secpack/keys/*/* gpg: key 063938BA42CFA724: public key "Marek Marczykowski-Górecki (Qubes OS signing key)" imported gpg: qubes-secpack/keys/core-devs/retired: read error: Is a directory gpg: no valid OpenPGP data found. gpg: key 8C05216CE09C093C: 1 signature not checked due to a missing key gpg: key 8C05216CE09C093C: public key "HW42 (Qubes Signing Key)" imported gpg: key DA0434BC706E1FCF: public key "Simon Gaiser (Qubes OS signing key)" imported gpg: key 8CE137352A019A17: 2 signatures not checked due to missing keys gpg: key 8CE137352A019A17: public key "Andrew David Wong (Qubes Documentation Signing Key)" imported gpg: key AAA743B42FBC07A9: public key "Brennan Novak (Qubes Website & Documentation Signing)" imported gpg: key B6A0BB95CA74A5C3: public key "Joanna Rutkowska (Qubes Documentation Signing Key)" imported gpg: key F32894BE9684938A: public key "Marek Marczykowski-Górecki (Qubes Documentation Signing Key)" imported gpg: key 6E7A27B909DAFB92: public key "Hakisho Nukama (Qubes Documentation Signing Key)" imported gpg: key 485C7504F27D0A72: 1 signature not checked due to a missing key gpg: key 485C7504F27D0A72: public key "Sven Semmler (Qubes Documentation Signing Key)" imported gpg: key BB52274595B71262: public key "unman (Qubes Documentation Signing Key)" imported gpg: key DC2F3678D272F2A8: 1 signature not checked due to a missing key gpg: key DC2F3678D272F2A8: public key "Wojtek Porczyk (Qubes OS documentation signing key)" imported gpg: key FD64F4F9E9720C4D: 1 signature not checked due to a missing key gpg: key FD64F4F9E9720C4D: public key "Zrubi (Qubes Documentation Signing Key)" imported gpg: key DDFA1A3E36879494: "Qubes Master Signing Key" not changed gpg: key 1848792F9E2795E9: public key "Qubes OS Release 4 Signing Key" imported gpg: qubes-secpack/keys/release-keys/retired: read error: Is a directory gpg: no valid OpenPGP data found. gpg: key D655A4F21830E06A: public key "Marek Marczykowski-Górecki (Qubes security pack)" imported gpg: key ACC2602F3F48CB21: public key "Qubes OS Security Team" imported gpg: qubes-secpack/keys/security-team/retired: read error: Is a directory gpg: no valid OpenPGP data found. gpg: key 4AC18DE1112E1490: public key "Simon Gaiser (Qubes Security Pack signing key)" imported gpg: Total number processed: 17 gpg: imported: 16 gpg: unchanged: 1 gpg: marginals needed: 3 completes needed: 1 trust model: pgp gpg: depth: 0 valid: 1 signed: 6 trust: 0-, 0q, 0n, 0m, 0f, 1u gpg: depth: 1 valid: 6 signed: 0 trust: 6-, 0q, 0n, 0m, 0f, 0u
Verify signed Git tags.
$ cd qubes-secpack/ $ git tag -v `git describe` object 266e14a6fae57c9a91362c9ac784d3a891f4d351 type commit tag marmarek_sec_266e14a6 tagger Marek Marczykowski-Górecki 1677757924 +0100 Tag for commit 266e14a6fae57c9a91362c9ac784d3a891f4d351 gpg: Signature made Thu 02 Mar 2023 03:52:04 AM PST gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full]
The exact output will differ, but the final line should always start with
gpg: Good signature from...followed by an appropriate key. The
[full]indicates full trust, which this key inherits in virtue of being validly signed by the QMSK.
Verify PGP signatures, e.g.:
$ cd QSBs/ $ gpg --verify qsb-087-2022.txt.sig.marmarek qsb-087-2022.txt gpg: Signature made Wed 23 Nov 2022 04:05:51 AM PST gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full] $ gpg --verify qsb-087-2022.txt.sig.simon qsb-087-2022.txt gpg: Signature made Wed 23 Nov 2022 03:50:42 AM PST gpg: using RSA key EA18E7F040C41DDAEFE9AA0F4AC18DE1112E1490 gpg: Good signature from "Simon Gaiser (Qubes Security Pack signing key)" [full] $ cd ../canaries/ $ gpg --verify canary-034-2023.txt.sig.marmarek canary-034-2023.txt gpg: Signature made Thu 02 Mar 2023 03:51:48 AM PST gpg: using RSA key 2D1771FE4D767EDC76B089FAD655A4F21830E06A gpg: Good signature from "Marek Marczykowski-Górecki (Qubes security pack)" [full] $ gpg --verify canary-034-2023.txt.sig.simon canary-034-2023.txt gpg: Signature made Thu 02 Mar 2023 01:47:52 AM PST gpg: using RSA key EA18E7F040C41DDAEFE9AA0F4AC18DE1112E1490 gpg: Good signature from "Simon Gaiser (Qubes Security Pack signing key)" [full]
Again, the exact output will differ, but the final line of output from each
gpg --verifycommand should always start with
gpg: Good signature from...followed by an appropriate key.
For this announcement (QSB-094), the commands are:
$ gpg --verify qsb-094-2023.txt.sig.marmarek qsb-094-2023.txt $ gpg --verify qsb-094-2023.txt.sig.simon qsb-094-2023.txt
You can also verify the signatures directly from this announcement in addition to or instead of verifying the files from the qubes-secpack. Simply copy and paste the QSB-094 text into a plain text file and do the same for both signature files. Then, perform the same authentication steps as listed above, substituting the filenames above with the names of the files you just created.
This is a companion discussion topic for the original entry at https://www.qubes-os.org/news/2023/09/27/qsb-094/