From: Thomas Huth <[email protected]> Some kernel code needs to zeroize their local hmac_sha1_ctx structures after use to avoid leaking sensitive material on the stack. Provide an hmac_sha1_zeroize_ctx() helper that can be used with __cleanup() to automatically zeroize the context when it goes out of scope.
Signed-off-by: Thomas Huth <[email protected]> --- include/crypto/sha1.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/include/crypto/sha1.h b/include/crypto/sha1.h index 4d973e016cd69..888dfc62e1c65 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 @@ -106,6 +107,22 @@ struct hmac_sha1_ctx { struct sha1_block_state ostate; }; +/** + * hmac_sha1_zeroize_ctx() - Zeroize a hmac_sha1_ctx structure + * @ctx: The location of the context that should be zeroized + * + * This function explicitly fills the hmac_sha1_ctx with zeroes. For + * example, it can be used with __cleanup() for local hmac_sha1_ctx + * structures on the stack, so that their content is not leaked via the + * stack when the context is left. Note: This is only required when not + * using hmac_sha1_final() that already zeroizes the structure at the + * end. + */ +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 -- 2.55.0
