We have published Qubes Security Bulletin 091: Windows PV drivers potentially compromised. 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 091
---===[ Qubes Security Bulletin 091 ]===--- 2023-07-26 Windows PV drivers potentially compromised User action required --------------------- At the time of writing, no fix is available, so no user action is required. However, users may wish to consider discontinuing the use of Qubes Windows Tools (QWT) in security-sensitive Windows qubes until a fix is available. Users with especially high security requirements may wish to consider recreating existing Windows qubes without QWT or replacing existing Windows qubes with qubes running a different operating system. Summary -------- On 2023-07-24, the Xen Project published "Xen Security Notice 1: winpvdrvbuild.xenproject.org potentially compromised" , which states: | Software running on the Xen Project hosted subdomain | winpvdrvbuild.xenproject.org is outdated and vulnerable to several | CVEs. Some of the reported issues include remote code execution. The | affected host was running the Jenkins build system for the Windows PV | Drivers subproject. | Since the list of CVEs reported include remote code execution we no | longer have confidence that binaries previously available at: | | https://xenbits.xen.org/pvdrivers/win/ | | are trustworthy. This includes binaries signed with Xen Project's EV | key that is cross-signed by Microsoft. Qubes Windows Tools includes the Xen Project's Windows PV Drivers. Impact ------- If the Xen Project's Windows PV Drivers were compromised at build time, all Windows qubes that have Qubes Windows Tools (QWT) installed may also be compromised. If the drivers were not compromised at build time, then there is no known vulnerability. Dom0 is not affected, even though the `qubes-windows-tools` package is installed in dom0, since neither the dom0 package build process nor dom0 itself interprets these driver files. Rather, the purpose of this package is merely to make the driver files available to the Windows qubes in which QWT are installed. Discussion ----------- We decided to use the Xen Project's official Windows PV Driver binaries in Qubes Windows Tools (QWT) (rather than building our own binaries from source) because the Xen Project's official binaries are signed by a special key that Windows accepts by default, which avoids the need to enable test-signing mode in Windows when installing the drivers. (We have no such key.) We used this approach for all versions of QWT released for Qubes 4.0 (driver version 8.2.1, May 2017), Qubes 4.1 (driver version 8.2.2, April 2019), and Qubes 4.2 (same as Qubes 4.1). While we have no way to know whether driver versions 8.2.1 or 8.2.2 have actually been compromised, it is worth noting that if the binaries were not compromised at build time, they could not have been tampered with after that time, since they were stored on another system and signed with a timestamped signature proving they were not modified afterward. At the time of writing, the Xen Project has not published replacement binaries signed by a Microsoft-approved key. The process for doing this has changed since the last version of Windows PV Drivers was released, and we have no information as to whether or when new signed binaries will be available.  In order to avoid similar problems in the future, we are working on a more permanent solution regarding the need for signed PV drivers in QWT. In the meantime, we will replace the `qubes-windows-tools` package with a dummy package containing only warning text. Credits -------- See the original Xen Security Notice. References -----------  https://lists.xenproject.org/archives/html/xen-announce/2023-07/msg00000.html  https://learn.microsoft.com/en-us/windows-hardware/drivers/install/deprecation-of-software-publisher-certificates-and-commercial-release-certificates -- The Qubes Security Team https://www.qubes-os.org/security/
Marek Marczykowski-Górecki’s PGP signature
-----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEELRdx/k12ftx2sIn61lWk8hgw4GoFAmTCHCgACgkQ1lWk8hgw 4Grc+g//Xk6OJ5XDnRfYBAxbU19c+h+hAwUKmuYW413B4Vzs9NtPLOCO6Nw4Ckh6 YCWrg9yusY4DglBOaelTgVsVoS6JgrkdqXzFCi0DUXJHdsw/GsKoezVBbwMlC3mp XoNgfL/meHuqRIjCf6BGj9SmDYvGJH4zQKqTe+RI9Zgk6sCSkH46WLHrdsoN4/FW pvYD7fSLAkba1P/rXoJPRYvym8GMnrCMDgpWiI2jMp43AStjLIg1Cuyb4Zrwo6X4 uBHDdXrrMLpIGAA/P4agHMY5uNDQDF+UZA65Hk54Ko+3FbgAtxmYUx0IbdS4AcgY 3B3//tJqTYQVyZLX56VX7xjRfxqK6CGcQxXRyxRg5ICkhidlNP/wc5UkeG1JSoVh YeCkMus9rem0LgGTadT2rzSZ8tOpohMi9QNAjk77t2gxPovy66tnGcsSA3RXZeAM 5eOd7WhlPXSb4L1LHUdKU5n1LHTgpWW9KgoSNTE8UmxBSJXlGMpFJcdieDSSmUEs qt5kIVSftJfYO8AWUQZJgIBEJ5VARzgWUt59wFhNKScw/UJh+RWqFTYzCKEZwpJd wH1Lj+cm/udB1rVNvnOpfO8oWPHewzfZzDfkgsm+9D0SoB4cyh1ebPzqcaedwnw4 b4waEa1GMAkpKWZzXAsS+MhDtlXlGY7W25x6EOr141zk7gQ6p0A= =JLOr -----END PGP SIGNATURE-----
Simon Gaiser (aka HW42)’s PGP signature
-----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEE6hjn8EDEHdrv6aoPSsGN4REuFJAFAmTBiLYACgkQSsGN4REu FJA2axAArF7TL6m5u2ePSQdMoNKYZJc/rZ2lq4I/TxhiNhmuzGxarlP9k+L83VHg q0LN68bwCqQZjZxHgzTaoKlYPo7/MAGWkp+hvhxtNfjW/2geMz8CadJxirNQt+wy jgcDXWjD04wzdeRJPwl3yTHesn4cFzDxlZ0Ujle5xjbkjALj5VEzjT8Bxl1plPof wSLgmbp05I8WE/plE93fk+or2UActukb4OcNI6rI3/7M0BEhweEWdfuu+Mxmz1uL jViub0T29jO+bKAb/kYtIottIjL6vtNQne/vn2ixR0GS510QSA/t4qyYS27UEWb9 WmIFzX9jq5+1qY+yO2vGnpFuev/On35P80JwE8AC7+o6TMMBcQEeAmmVEJyCmO/x GxdOqeAhn62gG9hF2n1ik/ESvH5poqmj895Ww2/H43azA0wZtxK69RbdZiJitmuW Urv6XLIJBsgaYmJm6nQctzfoG0v5WHSGHvD1c7CExN89eB3Ahy1GIZqgZuTCQcGI /5HrCgbasHiJh5jAnb392MmFUptDv6Yl6Q9LDbW+LRStvAAJEGICtYpps7S84T8F FYZIDbv0fLRtmtS03W3rYvM6Zpwha0irYx0wQdEUt6HkbSkrz5vAMujlrzbjX2oN K1dUkTbNdPduGW9VbTOwos1GMO+CVMeyNXrA5YJDuMvKCZcMQ2A= =SZ6e -----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-091), the commands are:
$ gpg --verify qsb-091-2023.txt.sig.marmarek qsb-091-2023.txt $ gpg --verify qsb-091-2023.txt.sig.simon qsb-091-2023.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-091 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/2023/07/27/qsb-091/