netdev - [PATCH net 3/3] tls: zero the crypto information from tls

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Message-Id: <c2b629a06486cd9c17a42cf2efe11ad26d8f9ef6.1536152698.git.sd@queasysnail.net>
Date:   Wed,  5 Sep 2018 15:21:45 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     Sabrina Dubroca <sd@...asysnail.net>,
        Boris Pismenny <borisp@...lanox.com>,
        Ilya Lesokhin <ilyal@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        Dave Watson <davejwatson@...com>
Subject: [PATCH net 3/3] tls: zero the crypto information from tls_context before freeing

This contains key material in crypto_send_aes_gcm_128 and
crypto_recv_aes_gcm_128.

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 include/net/tls.h  |  1 +
 net/tls/tls_main.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index d5c683e8bb22..2010d23112f9 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -180,6 +180,7 @@ struct tls_context {
 		struct tls_crypto_info crypto_recv;
 		struct tls12_crypto_info_aes_gcm_128 crypto_recv_aes_gcm_128;
 	};
+	char tls_crypto_ctx_end[0];
 
 	struct list_head list;
 	struct net_device *netdev;
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 0d432d025471..d3a57c0b2182 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -241,6 +241,16 @@ static void tls_write_space(struct sock *sk)
 	ctx->sk_write_space(sk);
 }
 
+static void tls_ctx_free(struct tls_context *ctx)
+{
+	if (!ctx)
+		return;
+
+	memzero_explicit(&ctx->crypto_send,
+			 offsetof(struct tls_context, tls_crypto_ctx_end));
+	kfree(ctx);
+}
+
 static void tls_sk_proto_close(struct sock *sk, long timeout)
 {
 	struct tls_context *ctx = tls_get_ctx(sk);
@@ -294,7 +304,7 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
 #else
 	{
 #endif
-		kfree(ctx);
+		tls_ctx_free(ctx);
 		ctx = NULL;
 	}
 
@@ -305,7 +315,7 @@ static void tls_sk_proto_close(struct sock *sk, long timeout)
 	 * for sk->sk_prot->unhash [tls_hw_unhash]
 	 */
 	if (free_ctx)
-		kfree(ctx);
+		tls_ctx_free(ctx);
 }
 
 static int do_tls_getsockopt_tx(struct sock *sk, char __user *optval,
-- 
2.18.0