Commit 0471b109 authored by Sabrina Dubroca's avatar Sabrina Dubroca Committed by David S. Miller
Browse files

tls: block decryption when a rekey is pending 



When a TLS handshake record carrying a KeyUpdate message is received,
all subsequent records will be encrypted with a new key. We need to
stop decrypting incoming records with the old key, and wait until
userspace provides a new key.

Make a note of this in the RX context just after decrypting that
record, and stop recvmsg/splice calls with EKEYEXPIRED until the new
key is available.

key_update_pending can't be combined with the existing bitfield,
because we will read it locklessly in ->poll.

Signed-off-by: default avatarSabrina Dubroca <sd@queasysnail.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 92c932b9

include/net/tls.h

+3 −0
Original line number Diff line number Diff line
@@ -59,6 +59,8 @@ struct tls_rec; 


#define TLS_CRYPTO_INFO_READY(info)	((info)->cipher_type)



#define TLS_HANDSHAKE_KEYUPDATE		24	/* rfc8446 B.3: Key update */



#define TLS_AAD_SPACE_SIZE		13



#define TLS_MAX_IV_SIZE			16
@@ -130,6 +132,7 @@ struct tls_sw_context_rx { 
	u8 async_capable:1;

	u8 zc_capable:1;

	u8 reader_contended:1;

	bool key_update_pending;



	struct tls_strparser strp;

net/tls/tls_sw.c

+34 −1
Original line number Diff line number Diff line
@@ -1314,6 +1314,10 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock, 
	int ret = 0;

	long timeo;



	/* a rekey is pending, let userspace deal with it */

	if (unlikely(ctx->key_update_pending))

		return -EKEYEXPIRED;



	timeo = sock_rcvtimeo(sk, nonblock);



	while (!tls_strp_msg_ready(ctx)) {
@@ -1720,6 +1724,34 @@ tls_decrypt_device(struct sock *sk, struct msghdr *msg, 
	return 1;

}



static int tls_check_pending_rekey(struct tls_context *ctx, struct sk_buff *skb)

{

	const struct strp_msg *rxm = strp_msg(skb);

	const struct tls_msg *tlm = tls_msg(skb);

	char hs_type;

	int err;



	if (likely(tlm->control != TLS_RECORD_TYPE_HANDSHAKE))

		return 0;



	if (rxm->full_len < 1)

		return 0;



	err = skb_copy_bits(skb, rxm->offset, &hs_type, 1);

	if (err < 0) {

		DEBUG_NET_WARN_ON_ONCE(1);

		return err;

	}



	if (hs_type == TLS_HANDSHAKE_KEYUPDATE) {

		struct tls_sw_context_rx *rx_ctx = ctx->priv_ctx_rx;



		WRITE_ONCE(rx_ctx->key_update_pending, true);

	}



	return 0;

}



static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,

			     struct tls_decrypt_arg *darg)

{
@@ -1739,7 +1771,7 @@ static int tls_rx_one_record(struct sock *sk, struct msghdr *msg, 
	rxm->full_len -= prot->overhead_size;

	tls_advance_record_sn(sk, prot, &tls_ctx->rx);



	return 0;

	return tls_check_pending_rekey(tls_ctx, darg->skb);

}



int decrypt_skb(struct sock *sk, struct scatterlist *sgout)
@@ -2719,6 +2751,7 @@ int tls_set_sw_offload(struct sock *sk, int tx) 
		crypto_info = &ctx->crypto_recv.info;

		cctx = &ctx->rx;

		aead = &sw_ctx_rx->aead_recv;

		sw_ctx_rx->key_update_pending = false;

	}



	cipher_desc = get_cipher_desc(crypto_info->cipher_type);