lib/crypto: sha1: Provide functions for zeroizing hmac_sha1 structures

In certain cases crypto code needs to zeroize their local hmac_sha1_key
or hmac_sha1_ctx structures after use to avoid leaking sensitive material.
Provide hmac_sha1_zeroize_key() and hmac_sha1_zeroize_ctx() helper
functions that e.g. can be used with __cleanup() to automatically zeroize
the structures when they go out of scope.

While we're at it, replace the related memzero_explicit() call in
lib/crypto/sha1.c with a call to the new helper function.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://patch.msgid.link/20260916095022.604354-9-thuth@redhat.com
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/crypto/sha1.h b/include/crypto/sha1.h
index 4d973e016cd6..bc0046bffeae 100644
--- a/include/crypto/sha1.h
+++ b/include/crypto/sha1.h
@@ -7,6 +7,7 @@
 #define _CRYPTO_SHA1_H
 
 #include <linux/types.h>
+#include <linux/string.h>
 
 #define SHA1_DIGEST_SIZE        20
 #define SHA1_BLOCK_SIZE         64
@@ -97,6 +98,15 @@ struct hmac_sha1_key {
 };
 
 /**
+ * hmac_sha1_zeroize_key() - Zeroize an hmac_sha1_key structure
+ * @key: The hmac_sha1_key to zeroize
+ */
+static inline void hmac_sha1_zeroize_key(struct hmac_sha1_key *key)
+{
+	memzero_explicit(key, sizeof(*key));
+}
+
+/**
  * struct hmac_sha1_ctx - Context for computing HMAC-SHA1 of a message
  * @sha_ctx: private
  * @ostate: private
@@ -107,6 +117,15 @@ struct hmac_sha1_ctx {
 };
 
 /**
+ * hmac_sha1_zeroize_ctx() - Zeroize an hmac_sha1_ctx structure
+ * @ctx: The hmac_sha1_ctx context to zeroize
+ */
+static inline void hmac_sha1_zeroize_ctx(struct hmac_sha1_ctx *ctx)
+{
+	memzero_explicit(ctx, sizeof(*ctx));
+}
+
+/**
  * hmac_sha1_preparekey() - Prepare a key for HMAC-SHA1
  * @key: (output) the key structure to initialize
  * @raw_key: the raw HMAC-SHA1 key