Subject: [PATCH net-next 06/10] tls: rx: use a define for tag length

From: Jakub Kicinski <[email-masked]>
Date: Thu, 7 Apr 2022 20:38:19 -0700

TLS 1.3 has to strip padding, and it starts out 16 bytes
from the end of the record. Make it clear this is because
of the auth tag.

Signed-off-by: Jakub Kicinski <[email-masked]>
---
 include/net/tls.h | 1 +
 net/tls/tls_sw.c  | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index f040edc97c50..a01c264e5f15 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -64,6 +64,7 @@
 #define TLS_AAD_SPACE_SIZE		13
 
 #define MAX_IV_SIZE			16
+#define TLS_TAG_SIZE			16
 #define TLS_MAX_REC_SEQ_SIZE		8
 
 /* For CCM mode, the full 16-bytes of IV is made of '4' fields of given sizes.
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index eb2e8495aa62..579ccfd011a1 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -136,9 +136,9 @@ static int padding_length(struct tls_prot_info *prot, struct sk_buff *skb)
 
 	/* Determine zero-padding length */
 	if (prot->version == TLS_1_3_VERSION) {
+		int back = TLS_TAG_SIZE + 1;
 		char content_type = 0;
 		int err;
-		int back = 17;
 
 		while (content_type == 0) {
 			if (back > rxm->full_len - prot->prepend_size)
@@ -2496,7 +2496,7 @@ int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
 
 	/* Sanity-check the sizes for stack allocations. */
 	if (iv_size > MAX_IV_SIZE || nonce_size > MAX_IV_SIZE ||
-	    rec_seq_size > TLS_MAX_REC_SEQ_SIZE) {
+	    rec_seq_size > TLS_MAX_REC_SEQ_SIZE || tag_size != TLS_TAG_SIZE) {
 		rc = -EINVAL;
 		goto free_priv;
 	}
-- 
2.34.1