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: Sabrina Dubroca sd@queasysnail.net --- v3: - move key_update_pending check into tls_rx_rec_wait (Jakub) - TLS_RECORD_TYPE_HANDSHAKE was added to include/net/tls_prot.h by the tls handshake series, drop that from this patch - move key_update_pending into an existing hole
v4: - flip TLS_RECORD_TYPE_HANDSHAKE test and use likely() (Jakub) - pass ctx rather than sk to tls_check_pending_rekey (Jakub) - use WRITE_ONCE to set key_update_pending to pair with poll's lockless read
v5: - some coding style changes (Parthiban Veerasoora) - changes to error handling in tls_check_pending_rekey (Jakub)
include/net/tls.h | 3 +++ net/tls/tls_sw.c | 35 ++++++++++++++++++++++++++++++++++- 2 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/include/net/tls.h b/include/net/tls.h index 61fef2880114..857340338b69 100644 --- a/include/net/tls.h +++ b/include/net/tls.h @@ -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;
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index bbf26cc4f6ee..3dcf8ee60fea 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -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);