Dear Qubes Community,
We have updated [Qubes Security Bulletin 090: Zenbleed (CVE-2023-20593,
XSA-433)](https://github.com/QubesOS/qubes-secpack/blob/main/QSBs/qsb-090-2023.txt).
The text of this updated QSB (including a changelog) 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 090
```
---===[ Qubes Security Bulletin 090 ]===---
2023-07-24
Zenbleed (CVE-2023-20593, XSA-433)
Changelog
----------
2023-07-24: Original QSB published
2023-08-01: Updated Xen packages with upstream bug fix (XSA-433 v3 [3])
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:
- linux-firmware 20230625-146
- Xen packages 4.14.5-22
For Qubes 4.2, in dom0:
- linux-firmware 20230625-147
- Xen packages 4.17.1-4
These packages will migrate from the security-testing repository to the
current (stable) repository over the next two weeks after being tested
by the community. [1] Once available, the packages are to be installed
via the Qubes Update tool or its command-line equivalents. [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 and initramfs binaries.
Summary
--------
On 2023-07-24, the Xen Project published XSA-433, "x86/AMD: Zenbleed"
[3]:
| Researchers at Google have discovered Zenbleed, a hardware bug causing
| corruption of the vector registers.
|
| When a VZEROUPPER instruction is discarded as part of a bad transient
| execution path, its effect on internal tracking are not unwound
| correctly. This manifests as the wrong micro-architectural state
| becoming architectural, and corrupting the vector registers.
|
| Note: While this malfunction is related to speculative execution, this
| is not a speculative sidechannel vulnerability.
|
| The corruption is not random. It happens to be stale values from the
| physical vector register file, a structure competitively shared between
| sibling threads. Therefore, an attacker can directly access data from
| the sibling thread, or from a more privileged context.
|
| For more details, see:
| https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7008.html
|
|
https://github.com/google/security-research/security/advisories/GHSA-v6wh-rxpg-cmm8
Impact
-------
As explained in XSA-433, this vulnerability is specific to the AMD Zen 2
microarchitecture, and AMD does not believe that other
microarchitectures are affected. Exploiting this vulnerability would
allow an attacker to read data from different contexts on the same core.
Examples of such data include key material, ciphertext and plaintext
from AES-NI operations, and the contents of REP-MOVS instructions, which
are commonly used to implement `memcpy()`.
In order to exploit this vulnerability, an attacker must be capable of
executing code at any privilege level in any qube, e.g., JavaScript in a
web browser. Moreover, the code to reliably exploit this vulnerability
is publicly available. Accordingly, there is a high risk of this
vulnerability being exploited in practice.
Credits
--------
Tavis Ormandy of Google Project Zero.
References
-----------
[1] https://www.qubes-os.org/doc/testing/
[2] https://www.qubes-os.org/doc/how-to-update/
[3] https://xenbits.xen.org/xsa/advisory-433.html
--
The Qubes Security Team
https://www.qubes-os.org/security/
```
*Source*:
<https://github.com/QubesOS/qubes-secpack/blob/main/QSBs/qsb-090-2023.txt>
## [Marek
Marczykowski-Górecki](https://www.qubes-os.org/team/#marek-marczykowski-górecki)'s
PGP signature
```
-----BEGIN PGP SIGNATURE-----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=gT88
-----END PGP SIGNATURE-----
```
*Source*:
<https://github.com/QubesOS/qubes-secpack/blob/main/QSBs/qsb-090-2023.txt.sig.marmarek>
## [Simon Gaiser (aka
HW42)](https://www.qubes-os.org/team/#simon-gaiser-aka-hw42)'s PGP signature
```
-----BEGIN PGP SIGNATURE-----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=omf2
-----END PGP SIGNATURE-----
```
*Source*:
<https://github.com/QubesOS/qubes-secpack/blob/main/QSBs/qsb-090-2023.txt.sig.simon>
## 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](https://www.qubes-os.org/security/#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](https://www.qubes-os.org/security/qsb/).
## 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](https://www.qubes-os.org/doc/how-to-update/). 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](https://en.wikipedia.org/wiki/Pretty_Good_Privacy) signature is a
cryptographic [digital
signature](https://en.wikipedia.org/wiki/Digital_signature) made in accordance
with the [OpenPGP](https://en.wikipedia.org/wiki/Pretty_Good_Privacy#OpenPGP)
standard. PGP signatures can be cryptographically verified with programs like
[GNU Privacy Guard (GPG)](https://gnupg.org/). 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 `git` and
`gpg` installed. (See
[here](https://www.qubes-os.org/security/verifying-signatures/#openpgp-software)
for Windows and Mac options.)
1. Obtain the Qubes Master Signing Key (QMSK), e.g.:
```shell_session
$ 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](https://www.qubes-os.org/security/verifying-signatures/#how-to-import-and-authenticate-the-qubes-master-signing-key)
for more ways to obtain the QMSK.)
2. 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.)
```shell_session
$ 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
```
3. *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](https://www.qubes-os.org/security/verifying-signatures/#how-to-import-and-authenticate-the-qubes-master-signing-key)
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.
4. Once you are satisfied that you have the genuine QMSK, set its trust level
to 5 ("ultimate"), then quit GnuPG with `q`.
```shell_session
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
```
5. Use Git to clone the qubes-secpack repo.
```shell_session
$ 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.
```
6. Import the included PGP keys. (See our [PGP key
policies](https://www.qubes-os.org/security/pack/#pgp-key-policies) for
important information about these keys.)
```shell_session
$ 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
```
7. Verify signed Git tags.
```shell_session
$ 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.
8. Verify PGP signatures, e.g.:
```shell_session
$ 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 --verify` command should always start with `gpg: Good signature from...`
followed by an appropriate key.
For this announcement (QSB-090), the commands are:
```
$ gpg --verify qsb-090-2023.txt.sig.marmarek qsb-090-2023.txt
$ gpg --verify qsb-090-2023.txt.sig.simon qsb-090-2023.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-090 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 announcement is also available on the Qubes website:
https://www.qubes-os.org/news/2023/08/02/qsb-090-update/
--
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