lib/crypto: aes: Provide functions for zeroizing aes_key and aes_enckey

Some crypto functions need to zeroize their local aes_key or aes_enckey
structures after use to avoid leaking sensitive material on the stack.
Provide aes_zeroize_key() and aes_zeroize_enckey() helper functions that
can be used with __cleanup() to automatically zeroize the structs when
they go out of scope.

While we're at it, replace the memzero_explicit() calls in lib/crypto/aes.c
with the new helper functions.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://patch.msgid.link/20260916095022.604354-2-thuth@redhat.com
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index 3279cfa54608..9fe868161e1d 100644
--- a/include/crypto/aes.h
+++ b/include/crypto/aes.h
@@ -102,6 +102,15 @@ struct aes_enckey {
 };
 
 /**
+ * aes_zeroize_enckey() - Zeroize an aes_enckey structure
+ * @key: The aes_enckey to zeroize
+ */
+static inline void aes_zeroize_enckey(struct aes_enckey *key)
+{
+	memzero_explicit(key, sizeof(*key));
+}
+
+/**
  * struct aes_key - An AES key prepared for encryption and decryption
  * @aes_enckey: Common fields and the key prepared for encryption
  * @inv_k: This generally contains the round keys for the AES Equivalent
@@ -115,6 +124,15 @@ struct aes_key {
 	union aes_invkey_arch inv_k;
 };
 
+/**
+ * aes_zeroize_key() - Zeroize an aes_key structure
+ * @key: The aes_key to zeroize
+ */
+static inline void aes_zeroize_key(struct aes_key *key)
+{
+	memzero_explicit(key, sizeof(*key));
+}
+
 /*
  * Please ensure that the first two fields are 16-byte aligned
  * relative to the start of the structure, i.e., don't move them!