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.

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: 3c4d7559 ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

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;

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",

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;

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)) {

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;
 	}