linux-cve-announce - CVE-2024-45004: KEYS: trusted: dcp: fix leak of blob encryption key

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Message-ID: <2024090451-CVE-2024-45004-61b4@gregkh>
Date: Wed,  4 Sep 2024 21:57:09 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-45004: KEYS: trusted: dcp: fix leak of blob encryption key

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

KEYS: trusted: dcp: fix leak of blob encryption key

Trusted keys unseal the key blob on load, but keep the sealed payload in
the blob field so that every subsequent read (export) will simply
convert this field to hex and send it to userspace.

With DCP-based trusted keys, we decrypt the blob encryption key (BEK)
in the Kernel due hardware limitations and then decrypt the blob payload.
BEK decryption is done in-place which means that the trusted key blob
field is modified and it consequently holds the BEK in plain text.
Every subsequent read of that key thus send the plain text BEK instead
of the encrypted BEK to userspace.

This issue only occurs when importing a trusted DCP-based key and
then exporting it again. This should rarely happen as the common use cases
are to either create a new trusted key and export it, or import a key
blob and then just use it without exporting it again.

Fix this by performing BEK decryption and encryption in a dedicated
buffer. Further always wipe the plain text BEK buffer to prevent leaking
the key via uninitialized memory.

The Linux kernel CVE team has assigned CVE-2024-45004 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.10 with commit 2e8a0f40a39c and fixed in 6.10.7 with commit 9e3b266afcfe
	Issue introduced in 6.10 with commit 2e8a0f40a39c and fixed in 6.11-rc4 with commit 0e28bf61a5f9

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-45004
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	security/keys/trusted-keys/trusted_dcp.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/9e3b266afcfe4294e84496f50f006f029d3100db
	https://git.kernel.org/stable/c/0e28bf61a5f9ab30be3f3b4eafb8d097e39446bb