[PATCH net v2 0/3] tls: don't leave keys in kernel memory

[PATCH net v2 0/3] tls: don't leave keys in kernel memory

[Sabrina Dubroca]

There are a few places where the RX/TX key for a TLS socket is copied
to kernel memory. This series clears those memory areas when they're no
longer needed.

v2: add union tls_crypto_context, following Vakul Garg's comment
    swap patch 2 and 3, using new union in patch 3

Sabrina Dubroca (3):
  tls: don't copy the key out of tls12_crypto_info_aes_gcm_128
  tls: zero the crypto information from tls_context before freeing
  tls: clear key material from kernel memory when do_tls_setsockopt_conf
    fails

 include/net/tls.h             | 19 +++++++++----------
 net/tls/tls_device.c          |  6 +++---
 net/tls/tls_device_fallback.c |  2 +-
 net/tls/tls_main.c            | 22 ++++++++++++++++------
 net/tls/tls_sw.c              | 13 +++++--------
 5 files changed, 34 insertions(+), 28 deletions(-)

-- 
2.18.0

[PATCH net v2 1/3] tls: don't copy the key out of tls12_crypto_info_aes_gcm_128

[Sabrina Dubroca]

There's no need to copy the key to an on-stack buffer before calling
crypto_aead_setkey().

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
---
 net/tls/tls_sw.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index e28a6ff25d96..f29b7c49cbf2 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1136,7 +1136,6 @@ void tls_sw_free_resources_rx(struct sock *sk)
 
 int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
 {
-	char keyval[TLS_CIPHER_AES_GCM_128_KEY_SIZE];
 	struct tls_crypto_info *crypto_info;
 	struct tls12_crypto_info_aes_gcm_128 *gcm_128_info;
 	struct tls_sw_context_tx *sw_ctx_tx = NULL;
@@ -1265,9 +1264,7 @@ int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
 
 	ctx->push_pending_record = tls_sw_push_pending_record;
 
-	memcpy(keyval, gcm_128_info->key, TLS_CIPHER_AES_GCM_128_KEY_SIZE);
-
-	rc = crypto_aead_setkey(*aead, keyval,
+	rc = crypto_aead_setkey(*aead, gcm_128_info->key,
 				TLS_CIPHER_AES_GCM_128_KEY_SIZE);
 	if (rc)
 		goto free_aead;
-- 
2.18.0

[PATCH net v2 2/3] 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.

Introduce union tls_crypto_context, and replace the two identical
unions directly embedded in struct tls_context with it. We can then
use this union to clean up the memory in the new tls_ctx_free()
function.

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
---
v2: introduce union tls_crypto_context

 include/net/tls.h             | 19 +++++++++----------
 net/tls/tls_device.c          |  6 +++---
 net/tls/tls_device_fallback.c |  2 +-
 net/tls/tls_main.c            | 20 +++++++++++++++-----
 net/tls/tls_sw.c              |  8 ++++----
 5 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index d5c683e8bb22..0a769cf2f5f3 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -171,15 +171,14 @@ struct cipher_context {
 	char *rec_seq;
 };
 
+union tls_crypto_context {
+	struct tls_crypto_info info;
+	struct tls12_crypto_info_aes_gcm_128 aes_gcm_128;
+};
+
 struct tls_context {
-	union {
-		struct tls_crypto_info crypto_send;
-		struct tls12_crypto_info_aes_gcm_128 crypto_send_aes_gcm_128;
-	};
-	union {
-		struct tls_crypto_info crypto_recv;
-		struct tls12_crypto_info_aes_gcm_128 crypto_recv_aes_gcm_128;
-	};
+	union tls_crypto_context crypto_send;
+	union tls_crypto_context crypto_recv;
 
 	struct list_head list;
 	struct net_device *netdev;
@@ -367,8 +366,8 @@ static inline void tls_fill_prepend(struct tls_context *ctx,
 	 * size KTLS_DTLS_HEADER_SIZE + KTLS_DTLS_NONCE_EXPLICIT_SIZE
 	 */
 	buf[0] = record_type;
-	buf[1] = TLS_VERSION_MINOR(ctx->crypto_send.version);
-	buf[2] = TLS_VERSION_MAJOR(ctx->crypto_send.version);
+	buf[1] = TLS_VERSION_MINOR(ctx->crypto_send.info.version);
+	buf[2] = TLS_VERSION_MAJOR(ctx->crypto_send.info.version);
 	/* we can use IV for nonce explicit according to spec */
 	buf[3] = pkt_len >> 8;
 	buf[4] = pkt_len & 0xFF;
diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 292742e50bfa..961b07d4d41c 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -686,7 +686,7 @@ int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
 		goto free_marker_record;
 	}
 
-	crypto_info = &ctx->crypto_send;
+	crypto_info = &ctx->crypto_send.info;
 	switch (crypto_info->cipher_type) {
 	case TLS_CIPHER_AES_GCM_128:
 		nonce_size = TLS_CIPHER_AES_GCM_128_IV_SIZE;
@@ -780,7 +780,7 @@ int tls_set_device_offload(struct sock *sk, struct tls_context *ctx)
 
 	ctx->priv_ctx_tx = offload_ctx;
 	rc = netdev->tlsdev_ops->tls_dev_add(netdev, sk, TLS_OFFLOAD_CTX_DIR_TX,
-					     &ctx->crypto_send,
+					     &ctx->crypto_send.info,
 					     tcp_sk(sk)->write_seq);
 	if (rc)
 		goto release_netdev;
@@ -862,7 +862,7 @@ int tls_set_device_offload_rx(struct sock *sk, struct tls_context *ctx)
 		goto release_ctx;
 
 	rc = netdev->tlsdev_ops->tls_dev_add(netdev, sk, TLS_OFFLOAD_CTX_DIR_RX,
-					     &ctx->crypto_recv,
+					     &ctx->crypto_recv.info,
 					     tcp_sk(sk)->copied_seq);
 	if (rc) {
 		pr_err_ratelimited("%s: The netdev has refused to offload this socket\n",
diff --git a/net/tls/tls_device_fallback.c b/net/tls/tls_device_fallback.c
index 6102169239d1..450a6dbc5a88 100644
--- a/net/tls/tls_device_fallback.c
+++ b/net/tls/tls_device_fallback.c
@@ -320,7 +320,7 @@ static struct sk_buff *tls_enc_skb(struct tls_context *tls_ctx,
 		goto free_req;
 
 	iv = buf;
-	memcpy(iv, tls_ctx->crypto_send_aes_gcm_128.salt,
+	memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
 	       TLS_CIPHER_AES_GCM_128_SALT_SIZE);
 	aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 	      TLS_CIPHER_AES_GCM_128_IV_SIZE;
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 180b6640e531..737b3865be1b 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, sizeof(ctx->crypto_send));
+	memzero_explicit(&ctx->crypto_recv, sizeof(ctx->crypto_recv));
+	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,
@@ -330,7 +340,7 @@ static int do_tls_getsockopt_tx(struct sock *sk, char __user *optval,
 	}
 
 	/* get user crypto info */
-	crypto_info = &ctx->crypto_send;
+	crypto_info = &ctx->crypto_send.info;
 
 	if (!TLS_CRYPTO_INFO_READY(crypto_info)) {
 		rc = -EBUSY;
@@ -417,9 +427,9 @@ static int do_tls_setsockopt_conf(struct sock *sk, char __user *optval,
 	}
 
 	if (tx)
-		crypto_info = &ctx->crypto_send;
+		crypto_info = &ctx->crypto_send.info;
 	else
-		crypto_info = &ctx->crypto_recv;
+		crypto_info = &ctx->crypto_recv.info;
 
 	/* Currently we don't support set crypto info more than one time */
 	if (TLS_CRYPTO_INFO_READY(crypto_info)) {
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index f29b7c49cbf2..9e918489f4fb 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1055,8 +1055,8 @@ static int tls_read_size(struct strparser *strp, struct sk_buff *skb)
 		goto read_failure;
 	}
 
-	if (header[1] != TLS_VERSION_MINOR(tls_ctx->crypto_recv.version) ||
-	    header[2] != TLS_VERSION_MAJOR(tls_ctx->crypto_recv.version)) {
+	if (header[1] != TLS_VERSION_MINOR(tls_ctx->crypto_recv.info.version) ||
+	    header[2] != TLS_VERSION_MAJOR(tls_ctx->crypto_recv.info.version)) {
 		ret = -EINVAL;
 		goto read_failure;
 	}
@@ -1180,12 +1180,12 @@ int tls_set_sw_offload(struct sock *sk, struct tls_context *ctx, int tx)
 
 	if (tx) {
 		crypto_init_wait(&sw_ctx_tx->async_wait);
-		crypto_info = &ctx->crypto_send;
+		crypto_info = &ctx->crypto_send.info;
 		cctx = &ctx->tx;
 		aead = &sw_ctx_tx->aead_send;
 	} else {
 		crypto_init_wait(&sw_ctx_rx->async_wait);
-		crypto_info = &ctx->crypto_recv;
+		crypto_info = &ctx->crypto_recv.info;
 		cctx = &ctx->rx;
 		aead = &sw_ctx_rx->aead_recv;
 	}
-- 
2.18.0

[PATCH net v2 3/3] tls: clear key material from kernel memory when do_tls_setsockopt_conf fails

[Sabrina Dubroca]

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
---
v2: use the new union tls_crypto_context

 net/tls/tls_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 737b3865be1b..523622dc74f8 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -509,7 +509,7 @@ static int do_tls_setsockopt_conf(struct sock *sk, char __user *optval,
 	goto out;
 
 err_crypto_info:
-	memset(crypto_info, 0, sizeof(*crypto_info));
+	memzero_explicit(crypto_info, sizeof(union tls_crypto_context));
 out:
 	return rc;
 }
-- 
2.18.0

Re: [PATCH net v2 0/3] tls: don't leave keys in kernel memory

[David Miller]

From: Sabrina Dubroca <sd@queasysnail.net>
Date: Wed, 12 Sep 2018 17:44:40 +0200

> There are a few places where the RX/TX key for a TLS socket is copied
> to kernel memory. This series clears those memory areas when they're no
> longer needed.
> 
> v2: add union tls_crypto_context, following Vakul Garg's comment
>     swap patch 2 and 3, using new union in patch 3

Series applied and queued up for -stable.

Thanks.