sctp: Use HMAC-SHA1 and HMAC-SHA256 library for chunk authentication

For SCTP chunk authentication, use the HMAC-SHA1 and HMAC-SHA256 library
functions instead of crypto_shash.  This is simpler and faster.  There's
no longer any need to pre-allocate 'crypto_shash' objects; the SCTP code
now simply calls into the HMAC code directly.

As part of this, make SCTP always support both HMAC-SHA1 and
HMAC-SHA256.  Previously, it only guaranteed support for HMAC-SHA1.
However, HMAC-SHA256 tended to be supported too anyway, as it was
supported if CONFIG_CRYPTO_SHA256 was enabled elsewhere in the kconfig.

Acked-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Link: https://patch.msgid.link/20250818205426.30222-4-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 6 insertions, 20 deletions

diff --git a/include/net/sctp/auth.h b/include/net/sctp/auth.h
index d4b3b2dcd15b..3d5879e08e78 100644
--- a/include/net/sctp/auth.h
+++ b/include/net/sctp/auth.h
@@ -22,16 +22,11 @@ struct sctp_endpoint;
 struct sctp_association;
 struct sctp_authkey;
 struct sctp_hmacalgo;
-struct crypto_shash;
 
-/*
- * Define a generic struct that will hold all the info
- * necessary for an HMAC transform
- */
+/* Defines an HMAC algorithm supported by SCTP chunk authentication */
 struct sctp_hmac {
-	__u16 hmac_id;		/* one of the above ids */
-	char *hmac_name;	/* name for loading */
-	__u16 hmac_len;		/* length of the signature */
+	__u16 hmac_id;		/* one of SCTP_AUTH_HMAC_ID_* */
+	__u16 hmac_len;		/* length of the HMAC value in bytes */
 };
 
 /* This is generic structure that containst authentication bytes used
@@ -78,9 +73,9 @@ int sctp_auth_asoc_copy_shkeys(const struct sctp_endpoint *ep,
 				struct sctp_association *asoc,
 				gfp_t gfp);
 int sctp_auth_init_hmacs(struct sctp_endpoint *ep, gfp_t gfp);
-void sctp_auth_destroy_hmacs(struct crypto_shash *auth_hmacs[]);
-struct sctp_hmac *sctp_auth_get_hmac(__u16 hmac_id);
-struct sctp_hmac *sctp_auth_asoc_get_hmac(const struct sctp_association *asoc);
+const struct sctp_hmac *sctp_auth_get_hmac(__u16 hmac_id);
+const struct sctp_hmac *
+sctp_auth_asoc_get_hmac(const struct sctp_association *asoc);
 void sctp_auth_asoc_set_default_hmac(struct sctp_association *asoc,
 				     struct sctp_hmac_algo_param *hmacs);
 int sctp_auth_asoc_verify_hmac_id(const struct sctp_association *asoc,
diff --git a/include/net/sctp/constants.h b/include/net/sctp/constants.h
index 5859e0a16a58..8e0f4c4f7750 100644
--- a/include/net/sctp/constants.h
+++ b/include/net/sctp/constants.h
@@ -417,16 +417,12 @@ enum {
 	SCTP_AUTH_HMAC_ID_RESERVED_0,
 	SCTP_AUTH_HMAC_ID_SHA1,
 	SCTP_AUTH_HMAC_ID_RESERVED_2,
-#if defined (CONFIG_CRYPTO_SHA256) || defined (CONFIG_CRYPTO_SHA256_MODULE)
 	SCTP_AUTH_HMAC_ID_SHA256,
-#endif
 	__SCTP_AUTH_HMAC_MAX
 };
 
 #define SCTP_AUTH_HMAC_ID_MAX	__SCTP_AUTH_HMAC_MAX - 1
 #define SCTP_AUTH_NUM_HMACS 	__SCTP_AUTH_HMAC_MAX
-#define SCTP_SHA1_SIG_SIZE 20
-#define SCTP_SHA256_SIG_SIZE 32
 
 /*  SCTP-AUTH, Section 3.2
  *     The chunk types for INIT, INIT-ACK, SHUTDOWN-COMPLETE and AUTH chunks
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 8a540ad9b509..6be6aec25731 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1329,11 +1329,6 @@ struct sctp_endpoint {
 	/* rcvbuf acct. policy.	*/
 	__u32 rcvbuf_policy;
 
-	/* SCTP AUTH: array of the HMACs that will be allocated
-	 * we need this per association so that we don't serialize
-	 */
-	struct crypto_shash **auth_hmacs;
-
 	/* SCTP-AUTH: hmacs for the endpoint encoded into parameter */
 	 struct sctp_hmac_algo_param *auth_hmacs_list;