[PATCH 04/11] lib/crypto: aes: Provide functions for zeroizing aes_key and aes_enckey

From: Thomas Huth <[email protected]>

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.

Signed-off-by: Thomas Huth <[email protected]>
---
 include/crypto/aes.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index faf1d1b75a15f..d00d88b71690b 100644
--- a/include/crypto/aes.h
+++ b/include/crypto/aes.h
@@ -102,6 +102,19 @@ struct aes_enckey {
 	union aes_enckey_arch k;
 };
 
+/**
+ * aes_zeroize_enckey() - Zeroize an aes_enckey structure
+ * @key: The location of the key structure that should be zeroized
+ *
+ * Explicitly fills the aes_enckey with zeroes. For example, use it with
+ * __cleanup() for local aes_enckey structures on the stack, so that their
+ * content is not leaked when the context is left.
+ */
+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
@@ -116,6 +129,19 @@ struct aes_key {
 	union aes_invkey_arch inv_k;
 };
 
+/**
+ * aes_zeroize_key() - Zeroize an aes_key structure
+ * @key: The location of the key structure that should be zeroized
+ *
+ * Explicitly fills the aes_key with zeroes. For example, use it with
+ * __cleanup() for local aes_key structures on the stack, so that their
+ * content is not leaked when the context is left.
+ */
+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!
-- 
2.55.0