[PATCH] lib/crypto: Add a sentence about zeroizing raw key structures

[PATCH] lib/crypto: Add a sentence about zeroizing raw key structures

[Thomas Huth]

Let's make it clear that raw key material has to be zeroized, too.

Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 Suggested here:
 https://lore.kernel.org/linux-crypto/20260930201434.GA61218@google.com/

 Documentation/crypto/libcrypto-zeroization.rst | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/crypto/libcrypto-zeroization.rst b/Documentation/crypto/libcrypto-zeroization.rst
index 76b6506711634..fe9f94413d1f2 100644
--- a/Documentation/crypto/libcrypto-zeroization.rst
+++ b/Documentation/crypto/libcrypto-zeroization.rst
@@ -47,7 +47,9 @@ The following types of structures hold sensitive material and should be
 zeroized after use:
 
 - **Key structures** (e.g. ``struct aes_key``, ``struct hmac_sha256_key``):
-  contain expanded round keys or prepared key material.
+  contain expanded round keys or prepared key material. Note: Arrays and
+  structures that contain raw key material (e.g. raw AES keys) of course
+  need to be zeroized as well as soon as the data is not required anymore.
 
 - **HMAC/MAC context structures** (e.g. ``struct hmac_sha256_ctx``,
   ``struct aes_cmac_ctx``): contain inner and outer hash states derived from
-- 
2.56.0

Re: [PATCH] lib/crypto: Add a sentence about zeroizing raw key structures

[Eric Biggers]

On Wed, Nov 04, 2026 at 11:53:52AM +0100, Thomas Huth wrote:
> Let's make it clear that raw key material has to be zeroized, too.
> 
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  Suggested here:
>  https://lore.kernel.org/linux-crypto/20260930201434.GA61218@google.com/
> 
>  Documentation/crypto/libcrypto-zeroization.rst | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/crypto/libcrypto-zeroization.rst b/Documentation/crypto/libcrypto-zeroization.rst
> index 76b6506711634..fe9f94413d1f2 100644
> --- a/Documentation/crypto/libcrypto-zeroization.rst
> +++ b/Documentation/crypto/libcrypto-zeroization.rst
> @@ -47,7 +47,9 @@ The following types of structures hold sensitive material and should be
>  zeroized after use:
>  
>  - **Key structures** (e.g. ``struct aes_key``, ``struct hmac_sha256_key``):
> -  contain expanded round keys or prepared key material.
> +  contain expanded round keys or prepared key material. Note: Arrays and
> +  structures that contain raw key material (e.g. raw AES keys) of course
> +  need to be zeroized as well as soon as the data is not required anymore.

It's better than nothing, but it reads kind of like an afterthought.
Might be worth its own paragraph before the one beginning with "The
following types of structures".

- Eric