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                               CERT-Renater

                     Note d'Information No. 2023/VULN306

_____________________________________________________________________

DATE                : 08/09/2023

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running OpenSSL versions 1.1.1 to 1.1.1v,
                           3.0.0 to 3.0.10, and 3.1.0 to 3.1.2.

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https://www.openssl.org/news/secadv/20230908.txt
_____________________________________________________________________


OpenSSL Security Advisory [8th September 2023]
==============================================

POLY1305 MAC implementation corrupts XMM registers on Windows 
(CVE-2023-4807)
=============================================================================

Severity: Low

Issue summary: The POLY1305 MAC (message authentication code) 
implementation contains a bug that might corrupt the internal
state of applications on the Windows 64 platform when running
on newer X86_64 processors supporting the AVX512-IFMA
instructions.

Impact summary: If in an application that uses the OpenSSL
library an attacker can influence whether the POLY1305 MAC
algorithm is used, the application state might be corrupted with
various application dependent consequences.

The POLY1305 MAC (message authentication code) implementation
in OpenSSL does not save the contents of non-volatile XMM
registers on Windows 64 platform when calculating the MAC of
data larger than 64 bytes. Before returning to the caller all
the XMM registers are set to zero rather than restoring their
previous content. The vulnerable code is used only on newer
x86_64 processors supporting the AVX512-IFMA instructions.

The consequences of this kind of internal application state
corruption can be various - from no consequences, if the
calling application does not depend on the contents of
non-volatile XMM registers at all, to the worst
consequences, where the attacker could get complete control
of the application process. However given the contents of
the registers are just zeroized so the attacker cannot put
arbitrary values inside, the most likely consequence, if any,
would be an incorrect result of some application dependent
calculations or a crash leading to a denial of service.

The POLY1305 MAC algorithm is most frequently used as part of
the CHACHA20-POLY1305 AEAD (authenticated encryption with
associated data) algorithm. The most common usage of this AEAD
cipher is with TLS protocol versions 1.2 and 1.3 and a malicious
client can influence whether this AEAD cipher is used by the
server. This implies that server applications using OpenSSL
can be potentially impacted. However we are currently not aware
of any concrete application that would be affected by this
issue therefore we consider this a Low severity security
issue.

As a workaround the AVX512-IFMA instructions support can be
disabled at runtime by setting the environment variable
OPENSSL_ia32cap:

    OPENSSL_ia32cap=:~0x200000

OpenSSL versions 1.1.1 to 1.1.1v, 3.0.0 to 3.0.10, and 3.1.0
to 3.1.2 are vulnerable to this issue. The FIPS provider is
not affected because the POLY1305 MAC algorithm is not FIPS
approved and the FIPS provider does not implement it.

OpenSSL version 1.0.2 is not affected by this issue.

Due to the low severity of this issue we are not issuing new
releases of OpenSSL at this time. The fix will be included in
the next releases when they become available. The fix is also
available in commit 4bfac447 (for 3.1), commit 6754de4a
(for 3.0), and commit a632d534 (for 1.1.1) in the OpenSSL git
repository.

This issue was reported publicly on GitHub on 23rd July 2023
by Zach Wilson (Nvidia) and subsequently to the OpenSSL
security team on 28th August 2023 by Bernd Edlinger. The fix
disabling the vulnerable codepath was developed
by Bernd Edlinger.

General Advisory Notes
======================

URL for this Security Advisory:
https://www.openssl.org/news/secadv/20230908.txt

Note: the online version of the advisory may be updated with
additional details over time.

For details of OpenSSL severity classifications please see:
https://www.openssl.org/policies/secpolicy.html

OpenSSL 1.1.1 will reach end-of-life on 2023-09-11. After that
date security fixes for 1.1.1 will only be available to premium
support customers.

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