[PATCH v2 01/13] lib/crypto: aes: Provide functions for zeroizing aes_key and aes_enckey

[Thomas Huth]

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@xxxxxxxxxx>
---
 include/crypto/aes.h | 18 ++++++++++++++++++
 lib/crypto/aes.c     | 10 +++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index 3279cfa546085..9fe868161e1d3 100644
--- a/include/crypto/aes.h
+++ b/include/crypto/aes.h
@@ -101,6 +101,15 @@ struct aes_enckey {
 	union aes_enckey_arch k;
 };
 
+/**
+ * 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
@@ -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!
diff --git a/lib/crypto/aes.c b/lib/crypto/aes.c
index f1549839b3de0..07c1d912ac365 100644
--- a/lib/crypto/aes.c
+++ b/lib/crypto/aes.c
@@ -539,7 +539,7 @@ static void __init aes_fips_test(void)
 	if (memcmp(fips_test_data, data, sizeof(data)) != 0)
 		panic("aes: FIPS self-test failed (wrong plaintext)\n");
 
-	memzero_explicit(&key, sizeof(key));
+	aes_zeroize_key(&key);
 }
 
 #if IS_ENABLED(CONFIG_CRYPTO_LIB_AES_CBC_MACS)
@@ -827,7 +827,7 @@ static void __init aes_ecb_fips_test(void)
 	if (memcmp(fips_test_data, data, sizeof(data)) != 0)
 		panic("aes: ECB FIPS self-test failed (wrong plaintext)\n");
 
-	memzero_explicit(&key, sizeof(key));
+	aes_zeroize_key(&key);
 }
 #else /* CONFIG_CRYPTO_LIB_AES_ECB */
 static inline void aes_ecb_fips_test(void)
@@ -1040,7 +1040,7 @@ static void __init aes_cbc_fips_test(void)
 	if (memcmp(fips_test_data, data, sizeof(data)) != 0)
 		panic("aes: CBC FIPS self-test failed (wrong plaintext)\n");
 
-	memzero_explicit(&key, sizeof(key));
+	aes_zeroize_key(&key);
 }
 
 /* FIPS cryptographic algorithm self-test for AES-CBC-CTS */
@@ -1069,7 +1069,7 @@ static void __init aes_cbc_cts_fips_test(void)
 	if (memcmp(ptext, data, data_len) != 0)
 		panic("aes: CBC-CTS FIPS self-test failed (wrong plaintext)\n");
 
-	memzero_explicit(&key, sizeof(key));
+	aes_zeroize_key(&key);
 }
 #else /* CONFIG_CRYPTO_LIB_AES_CBC */
 static inline void aes_cbc_fips_test(void)
@@ -1194,7 +1194,7 @@ static void __init aes_ctr_fips_test(void)
 	if (memcmp(fips_test_data, data, sizeof(data)) != 0)
 		panic("aes: CTR FIPS self-test failed (wrong plaintext)\n");
 
-	memzero_explicit(&key, sizeof(key));
+	aes_zeroize_enckey(&key);
 }
 #else /* CONFIG_CRYPTO_LIB_AES_CTR */
 static inline void aes_ctr_fips_test(void)
-- 
2.55.0