[PATCH net 3/3] tls: zero the crypto information from tls_context before freeing

[Sabrina Dubroca]

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 <s...@queasysnail.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